LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS
An analysis of the fluorescent characteristics of ethylenediamine-N,N'-disuccinic and N,N-bis(phosphonomethyl)-2-aminopropionic acids was carried out depending on the pH of the solutions. It was established that the change in fluorescence intensity and lifetime is associated with the formation...
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2023
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Ukrainian Chemistry Journal| _version_ | 1871465954592948224 |
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| author | Trunova, Olena Rusakova, Nataliia |
| author_facet | Trunova, Olena Rusakova, Nataliia |
| author_institution_txt_mv | [
{
"author": "Olena Trunova",
"institution": "V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine"
},
{
"author": "Nataliia Rusakova",
"institution": "A.V. Bogatsky Physico-Chemical Institute of the National Academy of Sciences of Ukraine"
}
] |
| author_sort | Trunova, Olena |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:52Z |
| description | An analysis of the fluorescent characteristics of ethylenediamine-N,N'-disuccinic and N,N-bis(phosphonomethyl)-2-aminopropionic acids was carried out depending on the pH of the solutions. It was established that the change in fluorescence intensity and lifetime is associated with the formation of variously protonated forms of acids in which stable H-cycles are formed with the participation of hydrogen bonds. The energies of the singlet and triplet levels of the ligands were experimentally determined, the values of which are higher than the energy of the radiative level of the Nd(III) ion, which indicates the possibility of intramolecular transfer of the excitation energy to the resonance level of the lanthanide ion. It was established that both homo- and heteronuclear complexes of Nd(III) exhibit 4f-luminescence in the near-IR region. It was found that for phosphorus-containing complexes there is an increase in luminescence intensity and relative quantum yields in comparison with aminocarboxylate analogs. In heterometallic complexes based on aminopolycarboxylic acids, the intramolecular transfer of energy from the excited level of Co(II) to the resonance level of the f-metal leads to sensitization of the 4f-luminescence of the neodymium ion. |
| doi_str_mv | 10.33609/2708-129X.89.06.2023.55-70 |
| first_indexed | 2025-09-24T17:43:51Z |
| format | Article |
| fulltext |
55
UDK 546.657: 54-386 doi: 10.33609/2708-129X.89.06.2023.55-70
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONO
METHYL)-2-AMINOPROPIONIC ACIDS.
О.К. Trunova1, N.V. Rusakova2
1V.I. Vernadsky Institute of General and Inorganic Chemistry of the National Academy of Sciences
of Ukraine, 32/34 Academic Palladin ave., 03142 Kyiv, Ukraine;
2O.V. Bogatsky Physico-Chemical Institute of the National Academy of Sciences of Ukraine,
86 Lustdorf road, 65000 Odessa, Ukraine
*e-mail: trelkon@gmail.com
An analysis of the fluorescent characteristics of ethylenediamine-N,N'-disuccinic and
N,N-bis(phosphonomethyl)-2-aminopropionic acids was carried out depending on the pH
of the solutions. It was established that the change in fluorescence intensity and lifetime is
associated with the formation of variously protonated forms of acids in which stable H-cycles
are formed with the participation of hydrogen bonds. The energies of the singlet and triplet
levels of the ligands were experimentally determined, the values of which are higher than the
energy of the radiative level of the Nd(III) ion, which indicates the possibility of intramo-
lecular transfer of the excitation energy to the resonance level of the lanthanide ion. It was
established that both homo- and heteronuclear complexes of Nd(III) exhibit 4f-luminescence
in the near-IR region. It was found that for phosphorus-containing complexes there is an
increase in luminescence intensity and relative quantum yields in comparison with amino-
carboxylate analogs. In heterometallic complexes based on aminopolycarboxylic acids, the
intramolecular transfer of energy from the excited level of Co(II) to the resonance level of the
f-metal leads to sensitization of the 4f-luminescence of the neodymium ion.
Key words: complexes, neodymium, aminopolycarboxylic acids, aminocarboxyphospho-
nates, synthesis, luminescence.
INTRODUCTION. The synthesis and re-
search of complex compounds with ligands
that have several donor centers are of increased
interest due to the possibility of using them
as primary molecular blocks to create more
complex polynuclear systems with a given
structure and predicted properties. The stabili
ty and solubility of the complex, as well as the
efficiency of 4f-luminescence, depend on the
selected ligand. Effective energy transfer from
the triplet level of the ligand to the resonance
level of the lanthanide ion is a necessary con-
dition for realizing 4f-luminescence in lantha-
nide compounds. Moreover, the effectiveness
56 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
of this process and the luminescence yield will
be influenced by such factors as the energy of
the triplet level of the ligand, the structure of
the ligand (the presence of electron-donat-
ing and electron-accepting substituents and
their mutual location in the ligand molecule),
quenching mechanisms, etc. In addition, for
selective binding to various metal ions, ligands
must have a heterodentate nature and an un-
saturated character [1, 2]. These requirements
are met by polydentate acyclic ligands, such as
aminopolycarboxylic (APС) or aminocarboxy-
phosphonic (AСPh) acids, which form highly
stable metal complexes with lanthanide ions
[3–8]. Complexes of lanthanides with APC or
ACPh that exhibit luminescence in the IR re-
gion (Nd, Pr, Er, Yb) can be used as precursors
for luminescent diagnostics, for fluorescent
immunoassays, for creating amplifiers in laser
systems, etc. [9–13]. In the latter case, factors
such as the minimal background signal of bio
objects (high in measurements in the visible
region), the possibility of luminescence excita-
tion in a wide range, including non-rigid irra-
diation with visible light, determine the pros-
pects for the practical use of these compounds.
Work on the enhancement of IR lumines-
cence of Ln(III) ions is mainly divided into two
directions: targeted selection of ligands in com-
plexes with which 4f-luminescence is realized
and synthesis of heteronuclear, in particular,
d-f-metal complexes. In the latter, 3-d metal
complexes can be used as energy transfer "an-
tennas" for the sensitization of the 4f-lumines-
cence of Ln(III) ions, as well as "energy gaps"
between the triplet level of the ligand and the
emission level of the lanthanide ion, thus fa-
cilitating the sensitization of its luminescence,
especially in the near-IR region. This is due to
the fact that the absorption bands (L→L* or
L→M) of transition metal complexes lie in the
near-ultraviolet, visible, or near long-wave-
length region, compared to the π→π* absorp-
tion bands of common ligands [14–16].
The studies of the spectral-luminescent
properties of aminopolycarboxylate complex-
es of lanthanides (both mono- and hetero-
metallic) cover mainly compounds with the
most common APC: EDTA and DTPA [17–
23]. There are almost no studies of the lumi-
nescent properties of Ln(III) complexes with
ethylenediaminedi-succinic acid (H4EDDS),
although it is known that heterometallic neo
dymium complexes can be used as drugs
for cancer diseases, immunodeficiency, and
blood diseases [24, 25]. In [5], new heterome-
tallic complexes of neodymium and zinc with
ethylenediaminedisuccinic acid were synthe-
sized for the first time. It was shown that the
monometallic complex of zinc, which is less
stable than the corresponding neodymium
complex, acts as a "building block" for obtain-
ing a heterobinuclear compound by the exo-
coordination of additional metal ions. It was
found that in the heterometallic complex, the
Nd3+ ion is bound to the oxygen atoms of two
α-carboxyl groups and one β-carboxyl group
and to the nitrogen atom of the ligand, and
the coordination sphere of the Zn2+ ion is
formed by the oxygen atoms of the β-carboxyl
group of the EDDS molecule, which performs
the bridging function, and water molecules.
It was shown that both homonuclear and
heteronuclear complexes exhibit 4f-lumines-
cence of neodymium ions, but the intensity
and quantum yield of luminescence in the
heterometallic system decreases due to the
overlap of the luminescence spectra of the
zinc-containing fragment with the absorption
bands of Nd(III) ions.
57https://ucj.org.ua
О.К. Trunova, N.V. Rusakova UCJ № 06 / Vol. 89
To date, in the literature, only a small num-
ber of works are devoted to complexes of lan-
thanides with aminocarboxyphosphonic acids,
their structural features and physicochemical
properties [26–31], and there is limited in-
formation on the luminescent properties of
the compounds. The work [26] describes the
synthesis of complexes of lanthanides with
phosphonomethylglycine (NPMG) of the gen-
eral formula LnC3H5NO5P∙nH2O (Ln(III)= La,
Ce, Nd, Er; n= 1; 1.5; 2 ). It was established
that the lanthanide ion coordinates NPMG
through the oxygen atoms of the carboxyl and
phosphonium groups and the nitrogen atom.
The stability constants of phosphonomethyl
glycinate complexes of Pr(III), Nd(III), and
Ga(III) were determined in [27, 28]. However,
in none of the cited works, data on the spect
ral-luminescent characteristics of synthesized
compounds were obtained.
Using N-(phosphonomethyl)iminodiacetic
acid (H4PMIDA), the authors of [29–31] ob-
tained a number of isostructural chiral lanth-
anoid carboxylate-phosphonates Ln(HPMI-
DA)(H2O)2·H2O (Ln(III) = Gd, Tb, Dy, Y, Er,
Yb, Lu). It was established that the Ln(III) ion
has an 8-coordinate environment and chelates
one HPMIDA anion in a tetradentate man-
ner (1N+3O) and two other HPMIDA anions
through one carboxylate and one phosphonate
oxygen atom. The lanthanide coordination
sphere is complemented by two aqua ligands.
Luminescence studies of the synthesized com-
pounds showed that the terbium complex ex-
hibits four very strong characteristic emission
bands 5D4→7Fj (j=6;5;4;3) at 490 nm, 547 nm,
582 nm, and 622 nm, respectively. The lifetime
of Tb (5D4) for λex,em = 380, 488 nm is about 1 ms.
In the spectra of the Er complex, there is only a
very broad emission band in the visible region
at 406 nm. The authors explain the absence of
emission bands in the near IR region for the
Er(III) compound by the effect of quenching of
the luminescent state by high-frequency oscil-
lating water molecules.
The study of Ln(III) (Pr, Nd, Gd, Ho, Er)
complexes with phosphonomethylaminosuc-
cinic acid showed that f-metals coordinate to
the ligand through a nitrogen atom and three
oxygen atoms of the phosphonic group and α-
and β-carboxyl groups with the formation of
complexes of the composition 1:1 for Pr(III)
and Er(III) and dimers for Nd(III) and Gd(III).
It has been established that molecular fluores-
cence is observed for phosphonomethylami-
nosuccinic acid in a wide pH range. Nd(III)
complexes exhibit 4f-luminescence in solid
form and in solution in the near IR region [4].
The survey of scientific literature shows
that the synthesis of new aminopolycarboxy-
lates and aminocarboxyphosphonates of lan-
thanides remains in the circle of interests of
modern coordination chemistry, since these
compounds can exhibit useful luminescent
properties both in the visible and in the near
IR region.
EXPERIMENT AND RESULTS DISCUS-
SION. The synthesis of monometallic com-
plexes was carried out by the interaction of
aqueous solutions of neodymium nitrate
Nd(NO3)3⋅6H2O with aqueous solutions of
complexons at a molar ratio of reagents of 1:1
at pH ~6 and a temperature of 50°C. After
cooling the reaction mixture, the formed com-
plexes were precipitated with absolute ethyl al-
cohol, filtered off and washed with ethanol to
remove inorganic impurities.
Ethylenediaminedisuccinic acid was ob-
tained by the condensation reaction of maleic
acid with ethylenediamine [32].
58 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
The synthesis of N,N-bis(phosphonome
thyl)-2-aminopropionic acid (H5PMAP) (Fig. 1)
was carried out in a three-component system
using phosphorous acid (hydrophosphoryl
component), paraformaldehyde (ketone com-
ponent) and β-alanine (amine component):
Fig. 1 - Synthesis scheme of N,N-bis(phosphonomethyl)-2-aminopropionic acid.
EXPERIMENT AND RESULTS DISCUSSION. The synthesis of monometallic complexes
was carried out by the interaction of aqueous solutions of neodymium nitrate Nd(NO3)36H2O with
aqueous solutions of complexons at a molar ratio of reagents of 1:1 at pH ~6 and a temperature of
50°C. After cooling the reaction mixture, the formed complexes were precipitated with absolute
ethyl alcohol, filtered off and washed with ethanol to remove inorganic impurities.
Ethylenediaminediasuccinic acid was obtained by the condensation reaction of maleic acid with
ethylenediamine [32].
The synthesis of N,N-bis(phosphonomethyl)-2-aminopropionic acid (H5PMAP) (Fig. 1) was
carried out in a three-component system using phosphorous acid (hydrophosphoryl component),
paraformaldehyde (ketone component) and β-alanine (amine component):
P
OH
OH
O
P
OH
OH
O
N
OH
O
NH2
OH
O
P
OH
OHOH CH2
O+ +2 2
Fig. 1 - Synthesis scheme of N,N-bis(phosphonomethyl)-2-aminopropionic acid.
Synthesis method of N,N-bis(phosphonomethyl)-2-aminopropionic acid. A mixture of 12.07
g (147 mmol) of phosphorous acid and 9.91 g (74.46 mmol) was dissolved in 40 ml of 1:1
hydrochloric acid. A two-fold excess of paraformaldehyde was added in small portions to the
resulting solution heated to 100°C, adding the next portion after dissolving the sediment of the
previous one. After that, the reaction mixture was heated for 8–16 hours, controlling the course of
the reaction according to the data of 31P NMR spectroscopy until the doublet signal of phosphorous
acid (1JPH=670 Hz) completely disappeared. After that, the reaction mixture was heated for another
2 hours and evaporated in vacuo to a thick glue-like consistency. The light viscous oil was
additionally evaporated three times under vacuum with isopropanol to remove residual water. A
white fine-crystalline precipitate of the target product (H5PMAP) was formed during long-term
grinding of the crushed glassy mass with methanol, it was quickly filtered off, washed twice with
methanol, diethyl ester and dried in a vacuum. The product yield of N,N-bis(phosphonomethyl)-2-
aminopropionic acid is 9.08 g (28.29 mmol, 38%).
The purity of the final product was determined by elemental analysis and the 31P NMR
method. The content of C, H, N was determined on a CHN analyzer Perkin Elmer - 2400. The
content of phosphorus was determined by the method of gravimetry. Н5PMAP: C4H11NO8P2 (М=
263). Anal. calc.(%): С, 18.26; Н, 4.14; N, 5.37; Р, 23.64. Found (%): С, 18.25; Н, 4.18; N, 5.32; Р,
23.57. 31Р NMR (D2O; δ, ррm): 10.360, t, 2JHP = 12,4 Hz. FT-IR (KBr, cm−1): 1737 [ν(COОН)];
1635 [νas(COO-)]; 1465 [νs(COO-)]; 1166 [νas(PO3)]; 1009 [νs(P=O)]; 943 [νas(POН)]; 3007–2926
[ν(СН)]; 3434 [ν(H2O)].
The synthesis of the heterometallic complexes NdCoEDDS and NdCoEDTA was carried out
by the block method by the interaction of monoprotonated ethylenediaminedisuccinate complex of
Co(II) with neodymium nitrate [8].
The excitation, fluorescence, and 4f-luminescence spectra were recorded on a Fluorolog FL
3–22 spectrofluorimeter (Horiba Jobin Yvon, Xe-450 W ozone-free lamp), equipped with an R928P
photoelectric power supply unit (Hamamatsu, Japan) for the visible spectral region and cooled to 77
K (Optical Systems Inc., USA) for the IR region.
In aqueous solutions, depending on the pH, ethylenediaminedisuccinic acid exists in several
stable anionic forms, which are characterized by the formation of chelate cycles with the
participation of a proton due to cross hydrogen bonds [33, 34]. At the same time, the presence of
intra- and intermolecular hydrogen bonds will affect the fluorescent properties of complexons, since
it is known that fluorescence spectra are sensitive to the influence of the latter. From this point of
view, it was interesting to study the fluorescence of H4EDDS at different pH values. Figure 2 shows
fluorescence spectra of ethylenediaminedisuccinic acid at different pH values of the solution. At 77
K, the fluorescence spectrum of ethylenediaminedisuccinic acid solutions in the pH range 1–2 (Fig.
2 a, curve 1) is a broad unstructured band with a maximum at 443.6 nm, (integral intensity (Ifl) is
Synthesis method of N,N-bis(phosphono
methyl)-2-aminopropionic acid. A mixture of
12.07 g (147 mmol) of phosphorous acid and
9.91 g (74.46 mmol) was dissolved in 40 ml of
1:1 hydrochloric acid. A two-fold excess of pa
raformaldehyde was added in small portions to
the resulting solution heated to 100 °C, adding
the next portion after dissolving the sediment
of the previous one. After that, the reaction
mixture was heated for 8–16 hours, controlling
the course of the reaction according to the data
of 31P NMR spectroscopy until the doublet sig-
nal of phosphorous acid (1JPH=670 Hz) com-
pletely disappeared. After that, the reaction
mixture was heated for another 2 hours and
evaporated in vacuo to a thick glue-like con-
sistency. The light viscous oil was additional-
ly evaporated three times under vacuum with
isopropanol to remove residual water. A white
fine-crystalline precipitate of the target pro
duct (H5PMAP) was formed during long-
term grinding of the crushed glassy mass with
methanol, it was quickly filtered off, washed
twice with methanol, diethyl ester and dried in
a vacuum. The product yield of N,N-bis(phos
phonomethyl)-2-aminopropionic acid is 9.08 g
(28.29 mmol, 38%).
The purity of the final product was deter-
mined by elemental analysis and the 31P NMR
method. The content of C, H, N was determined
on a CHN analyzer Perkin Elmer - 2400. The
content of phosphorus was determined by the
method of gravimetry. Н5PMAP: C4H11NO8P2
(М= 263). Anal. calc.(%): С, 18.26; Н, 4.14; N,
5.37; Р, 23.64. Found (%): С, 18.25; Н, 4.18;
N, 5.32; Р, 23.57. 31Р NMR (D2O; δ, ррm):
10.360, t, 2JHP = 12,4 Hz. FT-IR (KBr, cm−1):
1737 [ν(COОН)]; 1635 [νas(COO-)]; 1465
[νs(COO-)]; 1166 [νas(PO3)]; 1009 [νs(P=O)];
943 [νas(POН)]; 3007–2926 [ν(СН)]; 3434
[ν(H2O)].
The synthesis of the heterometallic comp
lexes NdCoEDDS and NdCoEDTA was carried
out by the block method by the interaction of
monoprotonated ethylenediaminedisuccinate
complex of Co(II) with neodymium nitrate [8].
The excitation, fluorescence, and 4f-lumi-
nescence spectra were recorded on a Fluoro
log FL 3–22 spectrofluorimeter (Horiba Jobin
Yvon, Xe-450 W ozone-free lamp), equipped
with an R928P photoelectric power supply unit
(Hamamatsu, Japan) for the visible spectral re-
gion and cooled to 77 K (Optical Systems Inc.,
USA) for the IR region.
In aqueous solutions, depending on the pH,
ethylenediaminedisuccinic acid exists in seve
ral stable anionic forms, which are character-
ized by the formation of chelate cycles with the
59https://ucj.org.ua
О.К. Trunova, N.V. Rusakova UCJ № 06 / Vol. 89
97∙106 a.u.). At these pH values, the emission spectrum of the acid is blurred, which can be
attributed to the formation of a network of hydrogen bonds between the molecules of the ligand and
the solvent.
Fig. 2 – Fluorescence spectra of H4EDDS at different pH values of the solution: 1 – 0.55–0.80; 2 – 2–5; 3 –
9.1; λex=340–360 nm, T 77K.
The fluorescence lifetime at pH 0.55 is 5.8 ns (Table 1) and has a monoexponential
character, which may indicate the predominant existence of betaine cations (H6L)2+ and (H5L)+ in
the solution. When carboxyl groups are ionized in the pH range 2–5 (Fig. 2, a, curve 2), in which
H4L, (H3L)1- and (H2L)2- particles are formed, the fluorescence intensity decreases slightly, and the
fluorescence maximum bathochromically shifts by 5–8 nm. The lifetimes fluorescence were
determined (τfl (pH 2.2) = 5.6 ns and 2.4 ns; τfl (pH 4.1) = 6.4 ns and 3.1 ns), the decay curves of
which have a multiexponential character and indicate the existence of several forms in the solution.
Table 1.
Characteristics of the fluorescence spectra for the variously protonated forms of H4EDDS and
H5PMAP depending on the pH of the solutions.
pH
Predominant form of the
ligand λfl, nm τfl, ns
H4EDDS Н5PMAP H4EDDS Н5PMAP H4EDDS Н5PMAP
0,55 - 1 (HCl) H6L2+, H5L+ H6L+
, H5L, 444 433 5.8 12.6
2.5 (acetate buffer) H4L, H3L; H4L-, H3L2-
449 437 5.6; 2.4 10.8
5 (КОН) H2L2; H2L3- 452 422 6.4; 3.1 12.3
7 (КОН) HL3; HL4- - 430 12.3; 4,8 12,6
9-10 (ammonia buffer) HL3-;L4- HL4-, L5- 454 429 7,3; 1,8 11.7
It can be assumed that, for example, for the form (H2L)2- (pН ≈ 5.3 – 5.5; Ifl=63∙106 a.u.; τfl= 12.3
and 4.8 ns) two methyleneaminodiacetate fragments, which make up 50% of the mass of the
molecule, rotate freely, causing a non-radiative loss of excitation energy, which explains the weak
fluorescence of this form of the ligand. It should be noted that, despite the significant advantage of
the presence of the (H2L)2- form in the solution, the value of the second τfl=4.8 ns indicates the
presence of other protoned forms of EDDS in this pH region [35]. At pH>8 (Fig. 2, a, curve 3),
there is a significant increase in fluorescence with a small shift in λfl. to the short-wave region.
Since the (H2L)2- and (HL)1- forms of the ligand dominate in the pH range 5–10, the increase in
fluorescence intensity can be attributed to the dissociation of the first betaine proton and the
formation of a hydrogen bond between nitrogen atoms and α-carboxyl groups, and, therefore, to a
participation of a proton due to cross hydrogen
bonds [33, 34]. At the same time, the presence
of intra- and intermolecular hydrogen bonds
will affect the fluorescent properties of com-
plexons, since it is known that fluorescence
spectra are sensitive to the influence of the lat-
ter. From this point of view, it was interesting to
study the fluorescence of H4EDDS at different
pH values. Figure 2 shows fluorescence spectra
of ethylenediaminedisuccinic acid at different
pH values of the solution. At 77 K, the fluores-
cence spectrum of ethylenediaminedisuccinic
acid solutions in the pH range 1–2 (Fig. 2 a,
curve 1) is a broad unstructured band with a
maximum at 443.6 nm, (integral intensity (Ifl)
is 97∙106 a.u.). At these pH values, the emission
spectrum of the acid is blurred, which can be
attributed to the formation of a network of hy-
drogen bonds between the molecules of the li-
gand and the solvent.
The fluorescence lifetime at pH 0.55 is 5.8
ns (Table 1) and has a monoexponential char-
acter, which may indicate the predominant ex-
istence of betaine cations (H6L)2+ and (H5L)+
in the solution. When carboxyl groups are
ionized in the pH range 2–5 (Fig. 2, curve 2),
in which H4L, (H3L)1- and (H2L)2- particles are
formed, the fluorescence intensity decreases
slightly, and the fluorescence maximum ba-
thochromically shifts by 5–8 nm. The lifetimes
fluorescence were determined (τfl (pH 2.2) =
5.6 ns and 2.4 ns; τfl (pH 4.1) = 6.4 ns and 3.1
ns), the decay curves of which have a multiex-
ponential character and indicate the existence
of several forms in the solution.
Fig. 2 – Fluorescence spectra of H4EDDS at
different pH values of the solution: 1 – 0.55–0.80;
2 – 2–5; 3 – 9.1; λex=340–360 nm, T 77K.
97∙106 a.u.). At these pH values, the emission spectrum of the acid is blurred, which can be
attributed to the formation of a network of hydrogen bonds between the molecules of the ligand and
the solvent.
Fig. 2 – Fluorescence spectra of H4EDDS at different pH values of the solution: 1 – 0.55–0.80; 2 – 2–5; 3 –
9.1; λex=340–360 nm, T 77K.
The fluorescence lifetime at pH 0.55 is 5.8 ns (Table 1) and has a monoexponential
character, which may indicate the predominant existence of betaine cations (H6L)2+ and (H5L)+ in
the solution. When carboxyl groups are ionized in the pH range 2–5 (Fig. 2, a, curve 2), in which
H4L, (H3L)1- and (H2L)2- particles are formed, the fluorescence intensity decreases slightly, and the
fluorescence maximum bathochromically shifts by 5–8 nm. The lifetimes fluorescence were
determined (τfl (pH 2.2) = 5.6 ns and 2.4 ns; τfl (pH 4.1) = 6.4 ns and 3.1 ns), the decay curves of
which have a multiexponential character and indicate the existence of several forms in the solution.
Table 1.
Characteristics of the fluorescence spectra for the variously protonated forms of H4EDDS and
H5PMAP depending on the pH of the solutions.
pH
Predominant form of the
ligand λfl, nm τfl, ns
H4EDDS Н5PMAP H4EDDS Н5PMAP H4EDDS Н5PMAP
0,55 - 1 (HCl) H6L2+, H5L+ H6L+
, H5L, 444 433 5.8 12.6
2.5 (acetate buffer) H4L, H3L; H4L-, H3L2-
449 437 5.6; 2.4 10.8
5 (КОН) H2L2; H2L3- 452 422 6.4; 3.1 12.3
7 (КОН) HL3; HL4- - 430 12.3; 4,8 12,6
9-10 (ammonia buffer) HL3-;L4- HL4-, L5- 454 429 7,3; 1,8 11.7
It can be assumed that, for example, for the form (H2L)2- (pН ≈ 5.3 – 5.5; Ifl=63∙106 a.u.; τfl= 12.3
and 4.8 ns) two methyleneaminodiacetate fragments, which make up 50% of the mass of the
molecule, rotate freely, causing a non-radiative loss of excitation energy, which explains the weak
fluorescence of this form of the ligand. It should be noted that, despite the significant advantage of
the presence of the (H2L)2- form in the solution, the value of the second τfl=4.8 ns indicates the
presence of other protoned forms of EDDS in this pH region [35]. At pH>8 (Fig. 2, a, curve 3),
there is a significant increase in fluorescence with a small shift in λfl. to the short-wave region.
Since the (H2L)2- and (HL)1- forms of the ligand dominate in the pH range 5–10, the increase in
fluorescence intensity can be attributed to the dissociation of the first betaine proton and the
formation of a hydrogen bond between nitrogen atoms and α-carboxyl groups, and, therefore, to a
Table 1.
Characteristics of the fluorescence spectra for the variously protonated forms of
H4EDDS and H5PMAP depending on the pH of the solutions.
pH
Predominant form of
the ligand λfl, nm τfl, ns
H4EDDS Н5PMAP H4EDDS Н5PMAP H4EDDS Н5PMAP
0,55 - 1 (HCl) H6L
2+, H5L
+ H6L
+
, H5L, 444 433 5.8 12.6
2.5 (acetate buffer) H4L, H3L; H4L
-, H3L
2- 449 437 5.6; 2.4 10.8
5 (КОН) H2L
2; H2L
3- 452 422 6.4; 3.1 12.3
7 (КОН) HL3; HL4- - 430 12.3; 4,8 12,6
9-10 (ammonia buffer) HL3-;L4- HL4-, L5- 454 429 7,3; 1,8 11.7
60 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
It can be assumed that, for example, for the
form (H2L)2- (pН ≈ 5.3 – 5.5; Ifl=63∙106 a.u.; τfl=
12.3 and 4.8 ns) two methyleneaminodiacetate
fragments, which make up 50% of the mass of
the molecule, rotate freely, causing a non-radi-
ative loss of excitation energy, which explains
the weak fluorescence of this form of the ligand.
It should be noted that, despite the significant
advantage of the presence of the (H2L)2- form
in the solution, the value of the second τfl=4.8
ns indicates the presence of other protoned
forms of EDDS in this pH region [35]. At
pH>8 (Fig. 2, curve 3), there is a significant in-
crease in fluorescence with a small shift in λfl.
to the short-wave region. Since the (H2L)2- and
(HL)1- forms of the ligand dominate in the pH
range 5–10, the increase in fluorescence in-
tensity can be attributed to the dissociation of
the first betaine proton and the formation of
a hydrogen bond between nitrogen atoms and
α-carboxyl groups, and, therefore, to a change
in the symmetry of the ligand. Probably, during
the transition to the (HL)3- and (L)4- forms, the
formation of hydrogen bonds limits the free
rotation of the groups, causing a sharp jump
in the fluorescence intensity. The analysis of
the data on the fluorescence attenuation of the
form (L)4- (рН≈11) made it possible to deter-
mine two values of τfl = 7.3 and 1.8 ns, which
can probably be associated with the formation
of "short-lived" H-cycles in solutions.
To obtain information on the possibil-
ity of realizing 4f-luminescence in lantha
nide-containing compounds based on N,N-
bis(phosphonomethyl)-2-aminopropionic
acid, its luminescent properties were investi-
gated. Figure 3 shows fluorescence spectra of
H5PMAP aqueous solutions at different pH
levels.
change in the symmetry of the ligand. Probably, during the transition to the (HL)3- and (L)4- forms,
the formation of hydrogen bonds limits the free rotation of the groups, causing a sharp jump in the
fluorescence intensity. The analysis of the data on the fluorescence attenuation of the form (L)4-
(рН≈11) made it possible to determine two values of τfl = 7.3 and 1.8 ns, which can probably be
associated with the formation of "short-lived" H-cycles in solutions.
To obtain information on the possibility of realizing 4f-luminescence in lanthanide-
containing compounds based on N,N-bis(phosphonomethyl)-2-aminopropionic acid, its luminescent
properties were investigated. Figure 3 shows fluorescence spectra of H5PMAP aqueous solutions at
different pH levels.
Fig. 3 – Fluorescence spectra of H5PMAP aqueous solutions at different pH values of the medium: 1– pH 1;
2 – pH 2.5; 3 – pH 5; 4 – pH 7.5 (λex=340 nm, T 298 K).
Upon excitation into the absorption band of the ligand at 290 nm at room temperature, a
broad structureless band is observed in the region of 370–600 nm, the position of the maximum of
which depends on the pH. At pH 1, the maximum of the fluorescence band is at 433 nm and at pH 2
at 437 nm. In a strongly acidic environment, the acid molecule is in the cationic form H6L+ as a
result of protonation of the amino group and realization of a zwitterionic structure with a positive
charge on the ammonium nitrogen atom and a negative center on one of the phosphonic groups. At
pH 5, the maximum of the fluorescence band is at 422 nm, which corresponds to the presence in the
solution of a mixture of ligand forms of various degrees of protonation with the predominant form
H3L2-. It should be noted that the fluorescence spectrum of H5PMAP in solid form consists of a
band with a maximum at 420 nm, which is probably caused by the presence of both zwitterionic and
deprotonated forms. The fluorescence lifetime at the maximum of this band is 12.61±0.26 ns. With
a further increase in pH, the HL4 and L5- forms prevail in the solution, which is reflected in the
fluorescence spectra by a long-wavelength shift of the band maximum: 429 nm at pH 7 and 430 nm
at pH 9. At the same time, stable H-cycles are formed in the anions: two 5-membered
aminophosphonic cycles and one 6-membered β-alanine cycle.
At a temperature of 77 K, a band with oscillatory structure is observed in the luminescence
spectrum of the ligand, the maximum of which is at 449 nm.
For the effective transfer of excitation energy from the triplet level of the ligand to the
resonance (radiating) level of lanthanide ions, it is necessary that the difference between these states
(energy gap) is within 2500–3500 cm-1 [36]. To experimentally determine the energy of the singlet
and triplet levels of ethylenediaminedisuccinic and bis(phosphonomethyl)-2-aminopropionic acids,
the fluorescence spectra of Gd(III) and Lu(III) complexes were studied. It was established that for
gadolinium ethylenediaminedisuccinate, the energy values of the singlet S1 (ES) and triplet T1 (ET)
levels are 22650 cm-1 and 19420 cm-1, respectively. The singlet and triplet levels of Lu(III)
complexes with H5PMAP are 22780 cm-1 and 21740 cm-1, respectively. The calculated energy
values of the triplet levels of the ligands are above the emitting 4F3/2 level of the Nd(III) ion, the
energy of which is approximately 11460 cm-1, which indicates the possibility of intramolecular
transfer of excitation energy from the lower triplet levels of the ligands to the resonance level of the
neodymium ion.
All synthesized Nd(III) complexes exhibit 4f-luminescence in the near IR region. Figure 4
shows excitation (a) and luminescence (b) spectra of the Nd(III) complex with H4EDDS. The
Fig. 3 – Fluorescence spectra of
H5PMAP aqueous solutions at dif-
ferent pH values of the medium: 1–
pH 1; 2 – pH 2.5; 3 – pH 5; 4 – pH 7.5
(λex=340 nm, T 298 K).
Upon excitation into the absorption band
of the ligand at 290 nm at room temperature,
a broad structureless band is observed in the
region of 370–600 nm, the position of the max-
imum of which depends on the pH. At pH 1,
the maximum of the fluorescence band is at
433 nm and at pH 2 at 437 nm. In a strongly
acidic environment, the acid molecule is in the
cationic form H6L
+ as a result of protonation
of the amino group and realization of a zwit-
terionic structure with a positive charge on
61https://ucj.org.ua
О.К. Trunova, N.V. Rusakova UCJ № 06 / Vol. 89
the ammonium nitrogen atom and a negative
center on one of the phosphonic groups. At pH
5, the maximum of the fluorescence band is at
422 nm, which corresponds to the presence
in the solution of a mixture of ligand forms of
various degrees of protonation with the pre-
dominant form H3L
2-. It should be noted that
the fluorescence spectrum of H5PMAP in solid
form consists of a band with a maximum at 420
nm, which is probably caused by the presence
of both zwitterionic and deprotonated forms.
The fluorescence lifetime at the maximum of
this band is 12.61±0.26 ns. With a further in-
crease in pH, the HL4 and L5- forms prevail in
the solution, which is reflected in the fluores-
cence spectra by a long-wavelength shift of the
band maximum: 429 nm at pH 7 and 430 nm
at pH 9. At the same time, stable H-cycles are
formed in the anions: two 5-membered ami-
nophosphonic cycles and one 6-membered
β-alanine cycle.
At a temperature of 77 K, a band with os-
cillatory structure is observed in the lumines-
cence spectrum of the ligand, the maximum of
which is at 449 nm.
For the effective transfer of excitation ener
gy from the triplet level of the ligand to the
resonance (radiating) level of lanthanide ions,
it is necessary that the difference between
these states (energy gap) is within 2500–
3500 cm-1 [36]. To experimentally determine
the energy of the singlet and triplet levels of
ethylenediaminedisuccinic and bis(phospho-
nomethyl)-2-aminopropionic acids, the fluo-
rescence spectra of Gd(III) and Lu(III) com-
plexes were studied. It was established that for
gadolinium ethylenediaminedisuccinate, the
energy values of the singlet S1 (ES) and triplet
T1 (ET) levels are 22650 cm-1 and 19420 cm-1,
respectively. The singlet and triplet levels of
Lu(III) complexes with H5PMAP are 22780 cm-1
and 21740 cm-1, respectively. The calculat-
ed energy values of the triplet levels of the li
gands are above the emitting 4F3/2 level of the
Nd(III) ion, the energy of which is approxi-
mately 11460 cm-1, which indicates the possi-
bility of intramolecular transfer of excitation
energy from the lower triplet levels of the
ligands to the resonance level of the neody
mium ion.
All synthesized Nd(III) complexes exhibit
4f-luminescence in the near IR region. Figure
4 shows excitation (a) and luminescence (b)
spectra of the Nd(III) complex with H4EDDS.
The excitation spectrum of NdEDDS contains
an intense broad band in the interval 330–380
nm with a maximum at 353 nm, which refers
to the π-π* transitions of the ligand. A low-in-
tensity and weak band at 332 nm is the result
of the overlap of the excitation spectra of an
organic molecule and the Nd(III) ions them-
selves, and the shoulder at 379 nm corresponds
to the transitions 4I9/2→4D3/2,
4D5/2,
4I11/2,
4D1/2,
2L15
/2,
4D7/2 of the Nd(III) ion. This relationship be-
tween the band intensities indicates lumines-
cence sensitization due to intramolecular en-
ergy transfer from the aminocarboxylate frag-
ment to the lanthanide ion.
In the spectra of 4f-luminescence of neo-
dymium ethylenediaminedisuccinate, three
bands of intrinsic luminescence of Nd(III)
are observed, which correspond to transi-
tions from the excited level 4F3/2 to the multi-
plets of the ground level 4Ij:
4I9/2 (λmax =871/905
nm), 4I11/2 (λmax = 1063 nm) and 4I13/2 (λmax =
1337/1359 nm) (Fig. 4, b). The most intense
emission band, the integral area of which
is ~75% of the total intensity, is at 1063 nm,
which is characteristic of the so-called «laser»
transition 4F3/2→4I11/2. The relative contributions
62 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
of the integral intensities of the 4I9/2 and 4I13/2
bands to the total intensity are approximate-
ly 13.5% and 11.5%, respectively. In this case,
the splitting of the 4F3/2→ 4I9/2 band into two
components at 871, 905 nm is observed. The
transition 4F3/2 → 4I13/2 is less intense, but is also
split into two components, one of which mani-
fests itself in a longer wavelength region (λmax =
1359 nm).
excitation spectrum of NdEDDS contains an intense broad band in the interval 330–380 nm with a
maximum at 353 nm, which refers to the π-π* transitions of the ligand. A low-intensity and weak
band at 332 nm is the result of the overlap of the excitation spectra of an organic molecule and the
Nd(III) ions themselves, and the shoulder at 379 nm corresponds to the transitions
4I9/2→4D3/2,4D5/2,4I11/2,4D1/2,2L15/2,4D7/2 of the Nd(III) ion. This relationship between the band
intensities indicates luminescence sensitization due to intramolecular energy transfer from the
aminocarboxylate fragment to the lanthanide ion.
300 320 340 360 380 400
4000
6000
8000
10000
12000
14000
16000
18000
20000
In
te
ns
ity
, a
.u
.
, nm
353
а
332
379
900 1000 1100 1200 1300 1400
0
5000
10000
15000
20000
, nm
In
te
ns
ity
, a
.u
.
4F
3/2
4I
11/2
4F
3/2
4I
9/2
4F
3/2
4I
13/2
b
Fig. 4 – Excitation spectrum (a) and 4f-luminescence spectrum (b) of NdEDDS in the solid state (λexc. = 353
nm, T=298 K).
In the spectra of 4f-luminescence of neodymium ethylenediaminedisuccinate, three bands of
intrinsic luminescence of Nd(III) are observed, which correspond to transitions from the excited
level 4F3/2 to the multiplets of the ground level 4Ij: 4I9/2 (λmax =871/905 nm), 4I11/2 (λmax = 1063 nm)
and 4I13/2 (λmax = 1337/1359 nm) (Fig. 4, b). The most intense emission band, the integral area of
which is ~75% of the total intensity, is at 1063 nm, which is characteristic of the so-called «laser»
transition 4F3/2→4I11/2. The relative contributions of the integral intensities of the 4I9/2 and 4I13/2
bands to the total intensity are approximately 13.5% and 11.5%, respectively. In this case, the
splitting of the 4F3/2→ 4I9/2 band into two components at 871, 905 nm is observed. The transition
4F3/2 4I13/2 is less intense, but is also split into two components, one of which manifests itself in a
longer wavelength region (λmax = 1359 nm).
The structure of the 4f-luminescence spectra of the neodymium complex based on H5PMAP
is identical to the luminescence spectra of the NdEDDS complex (Fig. 5). However, it should be
noted that in the phosphonate complex, in comparison with the ethylenediaminedisuccinate
complex, there is a hypsochromic shift of both components of the 4F3/2→ 4I9/2 transition by 4-7 nm
and the transition band 4F3/2→4I13/2 by 5 nm. The maximum of the most intense transition
4F3/2→4I11/2 which is at 1062 nm in the case of NdPMAP and at 1063 nm in the case of NdEDDS,
almost does not change its position. The absence of splitting of this band for both complexes
indicates the presence of one emitting center.
900 1000 1100 1200 1300 1400
300 350 400
800
1000
1200
1400
1600
, nm
362 nm
I, a.u.
0.0
, nm
I lu
m
., a
rb
.u
ni
.
1.0
4F3/2
4I9/2
4F3/2
4I11/2
4F3/2
4I13/2
1
2
Fig. 4 – Excitation spectrum (a) and 4f-luminescence spectrum (b) of NdEDDS
in the solid state (λexc. = 353 nm, T=298 K).
The structure of the 4f-luminescence spectra
of the neodymium complex based on H5PMAP
is identical to the luminescence spectra of the
NdEDDS complex (Fig. 5). However, it should
be noted that in the phosphonate complex, in
comparison with the ethylenediaminedisucci-
nate complex, there is a hypsochromic shift of
both components of the 4F3/2→ 4I9/2 transition
by 4-7 nm and the transition band 4F3/2→4I13/2
by 5 nm. The maximum of the most intense
transition 4F3/2→4I11/2 which is at 1062 nm in the
case of NdPMAP and at 1063 nm in the case of
NdEDDS, almost does not change its position.
The absence of splitting of this band for both
complexes indicates the presence of one emit-
ting center.
It should be noted that the luminescence in-
tensity of the NdPMAP complex in solutions is
much lower than in the solid state, because in
solutions there is a more significant deactiva-
tion of the excited state of the lanthanide ion
on the O–H oscillators of coordinated water
molecules, which is manifested in a low lumi-
nescence signal. But when passing from aque-
ous solutions of complexes to solid samples,
the structure of the luminescence spectra and
the position of the maxima of the spectral lines
does not change, which is a consequence of the
absence of significant structural changes in the
immediate environment of the lanthanide in
both aggregate states.
excitation spectrum of NdEDDS contains an intense broad band in the interval 330–380 nm with a
maximum at 353 nm, which refers to the π-π* transitions of the ligand. A low-intensity and weak
band at 332 nm is the result of the overlap of the excitation spectra of an organic molecule and the
Nd(III) ions themselves, and the shoulder at 379 nm corresponds to the transitions
4I9/2→4D3/2,4D5/2,4I11/2,4D1/2,2L15/2,4D7/2 of the Nd(III) ion. This relationship between the band
intensities indicates luminescence sensitization due to intramolecular energy transfer from the
aminocarboxylate fragment to the lanthanide ion.
300 320 340 360 380 400
4000
6000
8000
10000
12000
14000
16000
18000
20000
In
te
ns
ity
, a
.u
.
, nm
353
а
332
379
900 1000 1100 1200 1300 1400
0
5000
10000
15000
20000
, nm
In
te
ns
ity
, a
.u
.
4F
3/2
4I
11/2
4F
3/2
4I
9/2
4F
3/2
4I
13/2
b
Fig. 4 – Excitation spectrum (a) and 4f-luminescence spectrum (b) of NdEDDS in the solid state (λexc. = 353
nm, T=298 K).
In the spectra of 4f-luminescence of neodymium ethylenediaminedisuccinate, three bands of
intrinsic luminescence of Nd(III) are observed, which correspond to transitions from the excited
level 4F3/2 to the multiplets of the ground level 4Ij: 4I9/2 (λmax =871/905 nm), 4I11/2 (λmax = 1063 nm)
and 4I13/2 (λmax = 1337/1359 nm) (Fig. 4, b). The most intense emission band, the integral area of
which is ~75% of the total intensity, is at 1063 nm, which is characteristic of the so-called «laser»
transition 4F3/2→4I11/2. The relative contributions of the integral intensities of the 4I9/2 and 4I13/2
bands to the total intensity are approximately 13.5% and 11.5%, respectively. In this case, the
splitting of the 4F3/2→ 4I9/2 band into two components at 871, 905 nm is observed. The transition
4F3/2 4I13/2 is less intense, but is also split into two components, one of which manifests itself in a
longer wavelength region (λmax = 1359 nm).
The structure of the 4f-luminescence spectra of the neodymium complex based on H5PMAP
is identical to the luminescence spectra of the NdEDDS complex (Fig. 5). However, it should be
noted that in the phosphonate complex, in comparison with the ethylenediaminedisuccinate
complex, there is a hypsochromic shift of both components of the 4F3/2→ 4I9/2 transition by 4-7 nm
and the transition band 4F3/2→4I13/2 by 5 nm. The maximum of the most intense transition
4F3/2→4I11/2 which is at 1062 nm in the case of NdPMAP and at 1063 nm in the case of NdEDDS,
almost does not change its position. The absence of splitting of this band for both complexes
indicates the presence of one emitting center.
900 1000 1100 1200 1300 1400
300 350 400
800
1000
1200
1400
1600
, nm
362 nm
I, a.u.
0.0
, nm
I lu
m
., a
rb
.u
ni
.
1.0
4F3/2
4I9/2
4F3/2
4I11/2
4F3/2
4I13/2
1
2
63https://ucj.org.ua
О.К. Trunova, N.V. Rusakova UCJ № 06 / Vol. 89
A relatively small increase in luminescence
intensity for the NdPMAP complex compared
to NdEDDS may be due to the different struc-
ture of the complexes, which differ in the size
and number of chelate cycles. During com-
plexation, EDDS forms three 5-membered
(one ethylenediamine and two glycine) and
two 6-membered β-alanine cycles [7, 8]. Two
5-membered metallocycles aminophosphon-
ic and one 6-membered β-alanine metallocy-
cle are formed in the NdPMAP complex. The
arrangement of the cycles according to the
5–6–5 system is energetically more attractive
than 6–5–6. That is, in the neodymium amino
carboxyphosphonate, a less rigid structure is
realized than in the EDDS-based complex, and
in the latter, the neodymium ion is more coor-
dinatively saturated.
As it was indicated, recently the interest in
heterobinuclear coordination compounds of
lanthanides has increased significantly, which
is connected with the variety of their proper-
ties and the expansion of the field of practical
application. There are almost no reports on
luminescent Co-Nd aminocarboxylate comp
lexes. Some Co(II) coordination compounds
are characterized by fluorescence in the blue
or green region and can be used to sensitize
the luminescence of Ln(III) ions in the IR re-
gion. Therefore, it was of interest to investigate
the luminescence of heterometallic complexes
CoEDDSNd and CoEDTANd.
For CoGdEDDS solutions, upon excitation
in the region of 300–390 nm at room tempe
rature, a broad band of molecular fluorescence
in the region of 420–490 nm is observed. At
Fig. 5 – Excitation (inset) and 4f-luminescence spectra of the NdPMAP complex
in the solid state (1) and in solution (2) (λexc. = 362 nm, Т=298 К; CNd = 1∙10-3М).
excitation spectrum of NdEDDS contains an intense broad band in the interval 330–380 nm with a
maximum at 353 nm, which refers to the π-π* transitions of the ligand. A low-intensity and weak
band at 332 nm is the result of the overlap of the excitation spectra of an organic molecule and the
Nd(III) ions themselves, and the shoulder at 379 nm corresponds to the transitions
4I9/2→4D3/2,4D5/2,4I11/2,4D1/2,2L15/2,4D7/2 of the Nd(III) ion. This relationship between the band
intensities indicates luminescence sensitization due to intramolecular energy transfer from the
aminocarboxylate fragment to the lanthanide ion.
300 320 340 360 380 400
4000
6000
8000
10000
12000
14000
16000
18000
20000
In
te
ns
ity
, a
.u
.
, nm
353
а
332
379
900 1000 1100 1200 1300 1400
0
5000
10000
15000
20000
, nm
In
te
ns
ity
, a
.u
.
4F
3/2
4I
11/2
4F
3/2
4I
9/2
4F
3/2
4I
13/2
b
Fig. 4 – Excitation spectrum (a) and 4f-luminescence spectrum (b) of NdEDDS in the solid state (λexc. = 353
nm, T=298 K).
In the spectra of 4f-luminescence of neodymium ethylenediaminedisuccinate, three bands of
intrinsic luminescence of Nd(III) are observed, which correspond to transitions from the excited
level 4F3/2 to the multiplets of the ground level 4Ij: 4I9/2 (λmax =871/905 nm), 4I11/2 (λmax = 1063 nm)
and 4I13/2 (λmax = 1337/1359 nm) (Fig. 4, b). The most intense emission band, the integral area of
which is ~75% of the total intensity, is at 1063 nm, which is characteristic of the so-called «laser»
transition 4F3/2→4I11/2. The relative contributions of the integral intensities of the 4I9/2 and 4I13/2
bands to the total intensity are approximately 13.5% and 11.5%, respectively. In this case, the
splitting of the 4F3/2→ 4I9/2 band into two components at 871, 905 nm is observed. The transition
4F3/2 4I13/2 is less intense, but is also split into two components, one of which manifests itself in a
longer wavelength region (λmax = 1359 nm).
The structure of the 4f-luminescence spectra of the neodymium complex based on H5PMAP
is identical to the luminescence spectra of the NdEDDS complex (Fig. 5). However, it should be
noted that in the phosphonate complex, in comparison with the ethylenediaminedisuccinate
complex, there is a hypsochromic shift of both components of the 4F3/2→ 4I9/2 transition by 4-7 nm
and the transition band 4F3/2→4I13/2 by 5 nm. The maximum of the most intense transition
4F3/2→4I11/2 which is at 1062 nm in the case of NdPMAP and at 1063 nm in the case of NdEDDS,
almost does not change its position. The absence of splitting of this band for both complexes
indicates the presence of one emitting center.
900 1000 1100 1200 1300 1400
300 350 400
800
1000
1200
1400
1600
, nm
362 nm
I, a.u.
0.0
, nm
I lu
m
., a
rb
.u
ni
.
1.0
4F3/2
4I9/2
4F3/2
4I11/2
4F3/2
4I13/2
1
2
excitation spectrum of NdEDDS contains an intense broad band in the interval 330–380 nm with a
maximum at 353 nm, which refers to the π-π* transitions of the ligand. A low-intensity and weak
band at 332 nm is the result of the overlap of the excitation spectra of an organic molecule and the
Nd(III) ions themselves, and the shoulder at 379 nm corresponds to the transitions
4I9/2→4D3/2,4D5/2,4I11/2,4D1/2,2L15/2,4D7/2 of the Nd(III) ion. This relationship between the band
intensities indicates luminescence sensitization due to intramolecular energy transfer from the
aminocarboxylate fragment to the lanthanide ion.
300 320 340 360 380 400
4000
6000
8000
10000
12000
14000
16000
18000
20000
In
te
ns
ity
, a
.u
.
, nm
353
а
332
379
900 1000 1100 1200 1300 1400
0
5000
10000
15000
20000
, nm
In
te
ns
ity
, a
.u
.
4F
3/2
4I
11/2
4F
3/2
4I
9/2
4F
3/2
4I
13/2
b
Fig. 4 – Excitation spectrum (a) and 4f-luminescence spectrum (b) of NdEDDS in the solid state (λexc. = 353
nm, T=298 K).
In the spectra of 4f-luminescence of neodymium ethylenediaminedisuccinate, three bands of
intrinsic luminescence of Nd(III) are observed, which correspond to transitions from the excited
level 4F3/2 to the multiplets of the ground level 4Ij: 4I9/2 (λmax =871/905 nm), 4I11/2 (λmax = 1063 nm)
and 4I13/2 (λmax = 1337/1359 nm) (Fig. 4, b). The most intense emission band, the integral area of
which is ~75% of the total intensity, is at 1063 nm, which is characteristic of the so-called «laser»
transition 4F3/2→4I11/2. The relative contributions of the integral intensities of the 4I9/2 and 4I13/2
bands to the total intensity are approximately 13.5% and 11.5%, respectively. In this case, the
splitting of the 4F3/2→ 4I9/2 band into two components at 871, 905 nm is observed. The transition
4F3/2 4I13/2 is less intense, but is also split into two components, one of which manifests itself in a
longer wavelength region (λmax = 1359 nm).
The structure of the 4f-luminescence spectra of the neodymium complex based on H5PMAP
is identical to the luminescence spectra of the NdEDDS complex (Fig. 5). However, it should be
noted that in the phosphonate complex, in comparison with the ethylenediaminedisuccinate
complex, there is a hypsochromic shift of both components of the 4F3/2→ 4I9/2 transition by 4-7 nm
and the transition band 4F3/2→4I13/2 by 5 nm. The maximum of the most intense transition
4F3/2→4I11/2 which is at 1062 nm in the case of NdPMAP and at 1063 nm in the case of NdEDDS,
almost does not change its position. The absence of splitting of this band for both complexes
indicates the presence of one emitting center.
900 1000 1100 1200 1300 1400
300 350 400
800
1000
1200
1400
1600
, nm
362 nm
I, a.u.
0.0
, nm
I lu
m
., a
rb
.u
ni
.
1.0
4F3/2
4I9/2
4F3/2
4I11/2
4F3/2
4I13/2
1
2
64 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
77K, a structured band was recorded, which
is characterized by a maximum in the region
of 435–450 nm and a shoulder in the region
of 465–480 nm, which is probably a superpo-
sition of singlet and triplet states in hetero-
nuclear complexes. The application of a time
delay (50 µs) and freezing of the solutions al-
lowed to record the phosphorescence of the
complexes understudy, the maxima of which
lie in the region of 495–535 nm. Thus, the in-
troduction of Co(II) ions into the composition
of neodymium complexes leads, in compari-
son with monocomplexes, to a decrease in the
energy of singlet (ΔES ~ 2100–2300 cm-1) and
triplet (ΔET ~ 2100–2400 cm-1) levels, the latter
are located in the region of 18750–20300 cm-1.
For all complexes, the position of the fluores-
cence maximum within the experimental error
does not depend on the excitation wavelength.
It can be assumed that the influence of Co(II)
ions on the S1 and T1 states is associated with
the enhancement of the spin-orbital interac-
tion in the molecule. The position of the triplet
levels accounts for the presence of the 4f-lumi-
nescence signal of the neodymium ion in he
teronuclear complexes. It is also necessary to
take into account the energy of the excited le
vel of the cobalt ion itself (18500–20000 cm-1).
It can be assumed that intramolecular d → f
energy transfer leads to sensitization of 4f-lu-
minescence in the IR region in the case of
Nd(III) complexes, the luminescence spectra
of which are shown in Fig. 6.
Fig. 6 – 4f-Luminescence spectra of NdСoEDTA (1) complexes (λexc. = 365 nm) and NdCoEDDS (2) (λexc. =
345 nm).
The 4f-luminescence spectra of both complexes are identical have the appearance
characteristic of the neodymium ion and consist of three transitions: 4F3/2 → 4I9/2 (875–902 nm),
4F3/2 → 4I11/2 (1062–1065 nm), 4F3/2 → 4I13/2 (1330–1335 nm). But in the spectrum of the complex
with EDDS, a splitting of the 4F3/2 → 4I9/2 and 4F3/2 → 4I13/2 transition bands into three components
(878, 893, and 905 nm and 1340, 1357, and 1381 nm, respectively) is observed. The 4F3/2 → 4I11/2
transition has a pronounced splitting into two components, one of which manifests itself in the
longer wavelength region (1063 and 1078 nm). It is obvious that there are two emission centers in
the ethylenediaminedisuccinate complex. A similar set of splittings of the corresponding bands is
probably a consequence of the distortion of the configuration of the Nd(III) ion in NdCoEDDS and
a decrease in the symmetry of the coordination polyhedron compared to the NdCoEDTA complex.
Taking into account the energy of the excited level of Co(II) (4T1(P) ~ 520 nm [37, 38]), it
can be assumed that intramolecular d → f energy transfer leads to sensitization of the 4f-
luminescence of the neodymium ion, which is provided both by the overlapping of the
luminescence spectra of Co(II) with the excitation bands of neodymium-containing compounds,
which correspond to the transitions 4I9/2→4D3/2 (354 nm), 4I9/2→2P1/2 (432 nm), and by the low-
lying emitting 4F3/2 level of the ion neodymium (Fig. 7).
Fig. 7 – Scheme of sensitization of Nd(III) ion luminescence by Co(II) ions.
The increase in the luminescence intensity of Nd(III) ions in cobalt-containing heteronuclear
complexes is probably associated with the non-radiative transfer of energy between two metal
centers, in which the Co(III) ion acts as a donor, and the Nd(III) ion acts as an acceptor .
Comparison of the structure of the luminescence spectra of NdCoEDDS and NdCoEDTA
indicates a different coordination environment of Nd(III) in these complexes. Obviously, in
Fig. 6 – 4f-Luminescence spectra of
NdСoEDTA (1) complexes (λexc. = 365 nm)
and NdCoEDDS (2) (λexc. = 345 nm).
The 4f-luminescence spectra of both comp
lexes are identical have the appearance charac-
teristic of the neodymium ion and consist of
three transitions: 4F3/2 → 4I9/2 (875–902 nm),
4F3/2 → 4I11/2 (1062–1065 nm), 4F3/2 → 4I13/2
(1330–1335 nm). But in the spectrum of the
complex with EDDS, a splitting of the 4F3/2 →
4I9/2 and 4F3/2 → 4I13/2 transition bands into three
components (878, 893, and 905 nm and 1340,
1357, and 1381 nm, respectively) is observed.
The 4F3/2 → 4I11/2 transition has a pronounced
splitting into two components, one of which
65https://ucj.org.ua
О.К. Trunova, N.V. Rusakova UCJ № 06 / Vol. 89
manifests itself in the longer wavelength region
(1063 and 1078 nm). It is obvious that there are
two emission centers in the ethylenediaminedi-
succinate complex. A similar set of splittings of
the corresponding bands is probably a conse-
quence of the distortion of the configuration of
the Nd(III) ion in NdCoEDDS and a decrease
in the symmetry of the coordination polyhe-
dron compared to the NdCoEDTA complex.
Taking into account the energy of the excit-
ed level of Co(II) (4T1(P) ~ 520 nm [37, 38]),
it can be assumed that intramolecular d → f
energy transfer leads to sensitization of the
4f-luminescence of the neodymium ion, which
is provided both by the overlapping of the lu-
minescence spectra of Co(II) with the excita-
tion bands of neodymium-containing com-
pounds, which correspond to the transitions
4I9/2→4D3/2 (354 nm), 4I9/2→2P1/2 (432 nm), and
by the low-lying emitting 4F3/2 level of the ion
neodymium (Fig. 7).
Fig. 6 – 4f-Luminescence spectra of NdСoEDTA (1) complexes (λexc. = 365 nm) and NdCoEDDS (2) (λexc. =
345 nm).
The 4f-luminescence spectra of both complexes are identical have the appearance
characteristic of the neodymium ion and consist of three transitions: 4F3/2 → 4I9/2 (875–902 nm),
4F3/2 → 4I11/2 (1062–1065 nm), 4F3/2 → 4I13/2 (1330–1335 nm). But in the spectrum of the complex
with EDDS, a splitting of the 4F3/2 → 4I9/2 and 4F3/2 → 4I13/2 transition bands into three components
(878, 893, and 905 nm and 1340, 1357, and 1381 nm, respectively) is observed. The 4F3/2 → 4I11/2
transition has a pronounced splitting into two components, one of which manifests itself in the
longer wavelength region (1063 and 1078 nm). It is obvious that there are two emission centers in
the ethylenediaminedisuccinate complex. A similar set of splittings of the corresponding bands is
probably a consequence of the distortion of the configuration of the Nd(III) ion in NdCoEDDS and
a decrease in the symmetry of the coordination polyhedron compared to the NdCoEDTA complex.
Taking into account the energy of the excited level of Co(II) (4T1(P) ~ 520 nm [37, 38]), it
can be assumed that intramolecular d → f energy transfer leads to sensitization of the 4f-
luminescence of the neodymium ion, which is provided both by the overlapping of the
luminescence spectra of Co(II) with the excitation bands of neodymium-containing compounds,
which correspond to the transitions 4I9/2→4D3/2 (354 nm), 4I9/2→2P1/2 (432 nm), and by the low-
lying emitting 4F3/2 level of the ion neodymium (Fig. 7).
Fig. 7 – Scheme of sensitization of Nd(III) ion luminescence by Co(II) ions.
The increase in the luminescence intensity of Nd(III) ions in cobalt-containing heteronuclear
complexes is probably associated with the non-radiative transfer of energy between two metal
centers, in which the Co(III) ion acts as a donor, and the Nd(III) ion acts as an acceptor .
Comparison of the structure of the luminescence spectra of NdCoEDDS and NdCoEDTA
indicates a different coordination environment of Nd(III) in these complexes. Obviously, in
Fig. 7 – Scheme of sensitization
of Nd(III) ion luminescence by
Co(II) ions.
The increase in the luminescence intensity
of Nd(III) ions in cobalt-containing heteronu-
clear complexes is probably associated with the
non-radiative transfer of energy between two
metal centers, in which the Co(III) ion acts as a
donor, and the Nd(III) ion acts as an acceptor .
Comparison of the structure of the lumines-
cence spectra of NdCoEDDS and NdCoEDTA
indicates a different coordination environment
of Nd(III) in these complexes. Obviously, in
heterometallic ethylenediaminedisuccinate, the
Nd3+ coordination environment is formed due
to the 5-dentate coordination (2N+3O) of one
EDDS ion and 3 water molecules. The cobalt
ion is bound monodentately to the bridging
β-carboxyl group and bidentately to the oxygen
atoms of two α-carboxyl groups of the EDDS
molecule [8]. The Nd(III) ion in the NdСoEDTA
complex, similarly to Gd2Co3(EDTA)3(H2O)11
[39], is in the coordination environment of
NdO10 (bent bicapped tetragonal antiprism)
and is monodentately bound to six carboxy-
late oxygen atoms from three different EDTA
molecules and to four oxygen atoms of water
molecules. The Co(II) ion is in a distorted oc-
tahedral environment and is coordinated by two
nitrogen atoms, four oxygen atoms of EDTA
and one oxygen atom of a water molecule. Thus,
66 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
a more rigid structure is achieved in the ethy
lenediaminetetraacetate heterocomplex than
in the heteronuclear complex based on EDDS,
due to which the radiation intensity decreases.
In addition, a larger number of water mole-
cules in the NdCoEDTA complex also contri
butes to a decrease in luminescence.
But it should be noted that in going from
monometallic complexes based on aminopoly-
carboxylates to their heterometallic analogues,
the positions of the most intense transition
4F3/2 → 4I11/2 almost do not change, and the
components of the transition 4F3/2 → 4I9/2 shift
by ~1–3 nm, which is evidence of the preser-
vation of the neodymium coordination site in
both types of compounds.
When determining the luminescence inten-
sity of Nd(III) ions, as a rule, its «laser» most
intense transition 4F3/2 → 4I11/2, which corre-
sponds to the band with a maximum at 1060–
1065 nm, is used. When calculating the quan-
tum yield of luminescence of Nd(III) ions, the
4F3/2 → 4I9/2 transition is also taken into account,
the intensity of which is usually 20–40% of the
«laser» intensity. Due to the low intensity of the
4F3/2 → 4I13/2 transition (λmax ≅ 1345–1350 nm;
emission 5–10%), it is not taken into account
in the calculations (Table 2).
Table 2.
Characteristics of the luminescence spectra of Nd(III) complexes
with aminopolycarboxylic and aminocarboxyphosphonic acids.
Complex λex., nm λ4f-lum., nm Ilum.⋅ 10-4, a.u. φ4-f·10-3, a.u.
NdEDDS 353 905/871; 1063; 1359/1337 10.65 0.11
NdZnEDDS 365 [4] 902/874; 1064; 1365 4.26 0.06
NdСоEDDS 365 878/893/905; 1064/1077; 1340/1357/1381 14.27 0.29
NdEDТА 365 903/872;1062; 1358 4.04 0.025
NdZnEDТА 365 [4] 905/876; 1062; 1360 3.27 0.021
NdСоEDТА 345 902/867;1064; 1359/1338 8.92 0.17
NdPMAP 362 898/875; 1062; 1332 14.21 0.28
As can be seen from the data in the table. 2,
the heterometallic complex NdCoEDDS has
the largest integrated intensity of 4f-lumines-
cence among the investigated compounds. The
intensity of 4f-luminescence of NdCoEDTA
is 1.72 times lower than the intensity of
NdCoEDDS, but 2.2 times greater than
NdEDTA. In general, the trend of decreas-
ing Ilum. should be noted. of ethylenediamine-
tetraacetates compared to their ethylenedi-
aminedisuccinate analogues. Obviously, this is
related to the structure of the complexes. Com-
plexes based on EDTA are characterized by
the formation of net 2D polymers [39], which
obviously causes the shielding of the emitting
centers of the Nd3+ ion, and is the reason for the
low intensity and efficiency of luminescence.
The intensity of 4f-luminescence of the
NdPMAP complex is approximately the same
as that of Ilum. NdCoEDDS, which is probably
due to the proximity of the energies of their
triplet levels.
The quantum yield of 4f-luminescence (φ4-f)
for cobalt-containing heterometallic complex-
67https://ucj.org.ua
О.К. Trunova, N.V. Rusakova UCJ № 06 / Vol. 89
es is greater than for monometallic compounds
regardless of the complexon, while for ethyle
ne diamine disuccinates φ4-f is greater than for
ethylene diamine tetraacetates by a factor of 4.4
in the case of homonuclear complexes and by a
factor of 1.6 and – in the case of heteronuclear.
According to the values of 4f-luminescence
intensity and the calculated φ4-f, the Nd(III)
complexes can be placed in the following order:
NdСоEDDS ≥ NdPHMAР > NdСоEDТА >
NdEDDS > NdEDТА > NdZnEDТА >
NdZnEDDS.
CONCLUSIONS. The fluorescence of ethyle
nediaminedisuccinic and N,N-bis(phosphono
methyl)-2-aminopropionic acids in solution
at different pH values was investigated. It was
shown that depending on the pH, the intensity
and lifetime of fluorescence of variously proto-
nated forms of acids change, which is due to the
formation of stable H-cycles with the participa-
tion of hydrogen bonds. The energies of the sin-
glet and triplet levels of the ligands were exper-
imentally determined, the values of which are
higher than the energy of the radiative level of
the Nd(III) ion, which indicates the possibility
of intramolecular transfer of excitation energy
to the resonance level of the lanthanide ion.
The luminescent properties of homo- and
heteronuclear complexes of Nd(III) with
H4EDDS and H5PMAP were studied. It was
found that intense 4ƒ-luminescence in the
near IR region is observed for all synthesized
compounds upon excitation in the absorption
region of the ligand. It was shown that the lu-
minescence intensity depends on the coordi-
nation environment of the lanthanide ion. The
highest intensity of luminescence is exhibited
by the NdCoEDDS and NdPHMAR complex-
es, which are also characterized by a higher
quantum yield. In heterometallic complexes
based on aminopolycarboxylic acids, the intra
molecular transfer of energy from the excited
level of Co(II) to the resonance level of the
f-metal leads to sensitization of the 4f-lumi-
nescence of the neodymium ion.
AKNOWLEDGEMENT. The work was
carried out with the financial support
from the National Academy of Scienc-
es of Ukraine within the state budget topic
322E "Creation of new hybrid, composite and
polymer materials doped with coordination
compounds of 3d- and 4f-metals based on
β-diketonate and carboxylate acyclic ligands".
The state registration number of the work is
0122U001299.
ЛЮМІНЕСЦЕНТНІ ВЛАСТИВОСТІ КОМПЛЕК-
СІВ Nd(III) З ЕТИЛЕНДІАМІН-N,N'-ДИЯНТАР-
НОЮ ТА N,N-БІС(ФОСФОНОМЕТИЛ)-2-АМІНО
ПРОПІОНОВОЮ КИСЛОТАМИ
О. К. Трунова1, Н. В. Русакова2
1Інститут загальної та неорганічної хімії
ім. В. І. Вернадського НАН України,
просп. Академіка Палладіна, 32/34, Київ
03142, Україна;
2Фізико-хімічний інститут ім. О. В. Богат-
ського НАН України,
Люстдорфська дорога, 86, Одеса 65080, Ук
раїна
*e-mail: trelkon@gmail.com
Досліджено флуоресценцію етилендиа-
мін-N,N'-диянтарної та N,N-біс(фосфоно
метил)-2-амінопропіонової кислот у роз-
чині за різних значень рН. Показано, що
залежно від рН змінюються інтенсивність
та час життя флуоресценції різнопротонова-
них форм кислот, що зумовлено утворенням
68 ISSN 2708-129X. Укр. хім. журн., 2023
LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH
ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS.INORGANIC CHEMISTRY
стійких Н-циклів за участю водневих зв'яз-
ків. Експериментально визначено енергії
синглетних та триплетних рівнів лігандів
(ES= 22650 см-1, ET= 21420 см-1 для H4EDDS;
ES= 22780 см-1, ET= 20740 см-1 для H5PMAP),
значення яких є вищим енергії випроміню-
вального рівня іона Nd(III) (11 460 см-1), що
свідчить про можливість внутрішньо-мо-
лекулярного перенесення енергії збуджен-
ня на резонансний рівень іона лантаноїду.
Досліджено люмінесцентні властивості
гомо- і гетероядерних комплексів Nd(ІІІ) з
H4EDDS та H5PMAP. Виявлено, що при збу-
дженні в області поглинання ліганду для
всіх синтезованих сполук спостерігається
інтенсивна 4ƒ-люмінесценція в ближній
ІЧ-області. Показано, що інтенсивність
люмінесценції залежить від координацій-
ного оточення іона лантаноїду. Найбільшу
інтенсивність люмінесценції проявляють
комплекси NdСоEDDS та NdPHMAР, для
яких характерний і більш високий кванто-
вий вихід. У гетерометалічних комплексах
на основі амінополікарбонових кислот вну-
трішньомолекулярне перенесення енергії зі
збудженого рівня Со(ІІ) на резонансний рі-
вень f-металу призводить до сенсибілізації
4f-люмінесценції іона неодиму.
Ключові слова: комплекси, неодим, амі
нополікарбонові кислоти, амінокарбокси
фосфонати, синтез, люмінесценція.
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Стаття надійшла 12.07.2023.
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| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-554 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:10:14Z |
| publishDate | 2023 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/74/9f4c210ee7516f2813101711ae8ce074.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-5542026-07-22T08:23:52Z LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS Trunova, Olena Rusakova, Nataliia complexes, neodymium, aminopolycarboxylic acids, aminocarboxyphosphonates, synthesis, luminescence. An analysis of the fluorescent characteristics of ethylenediamine-N,N'-disuccinic and N,N-bis(phosphonomethyl)-2-aminopropionic acids was carried out depending on the pH of the solutions. It was established that the change in fluorescence intensity and lifetime is associated with the formation of variously protonated forms of acids in which stable H-cycles are formed with the participation of hydrogen bonds. The energies of the singlet and triplet levels of the ligands were experimentally determined, the values of which are higher than the energy of the radiative level of the Nd(III) ion, which indicates the possibility of intramolecular transfer of the excitation energy to the resonance level of the lanthanide ion. It was established that both homo- and heteronuclear complexes of Nd(III) exhibit 4f-luminescence in the near-IR region. It was found that for phosphorus-containing complexes there is an increase in luminescence intensity and relative quantum yields in comparison with aminocarboxylate analogs. In heterometallic complexes based on aminopolycarboxylic acids, the intramolecular transfer of energy from the excited level of Co(II) to the resonance level of the f-metal leads to sensitization of the 4f-luminescence of the neodymium ion. V.I.Vernadsky Institute of General and Inorganic Chemistry 2023-07-28 Article Article Inorganic Chemistry Неорганическая химия Неорганічна хімія application/pdf https://ucj.org.ua/index.php/journal/article/view/554 10.33609/2708-129X.89.06.2023.55-70 Ukrainian Chemistry Journal; Vol. 89 No. 6 (2023): Ukrainian Chemistry Journal; 55-70 Украинский химический журнал; ##issue.vol## 89 ##issue.no## 6 (2023): Ukrainian Chemistry Journal; 55-70 Український хімічний журнал; Том 89 № 6 (2023): Ukrainian Chemistry Journal; 55-70 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/554/284 Copyright (c) 2023 Olena Trunova, Nataliia Rusakova https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Trunova, Olena Rusakova, Nataliia LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS |
| title | LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS |
| title_full | LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS |
| title_fullStr | LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS |
| title_full_unstemmed | LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS |
| title_short | LUMINESCENT PROPERTIES OF Nd(III) COMPLEXES WITH ETHYLENEDIAMINE-N,N'-DISUCCINIC AND N,N-BIS(PHOSPHONOMETHYL)-2-AMINOPROPIONIC ACIDS |
| title_sort | luminescent properties of nd(iii) complexes with ethylenediamine-n,n'-disuccinic and n,n-bis(phosphonomethyl)-2-aminopropionic acids |
| topic_facet | complexes neodymium aminopolycarboxylic acids aminocarboxyphosphonates synthesis luminescence. |
| url | https://ucj.org.ua/index.php/journal/article/view/554 |
| work_keys_str_mv | AT trunovaolena luminescentpropertiesofndiiicomplexeswithethylenediaminenndisuccinicandnnbisphosphonomethyl2aminopropionicacids AT rusakovanataliia luminescentpropertiesofndiiicomplexeswithethylenediaminenndisuccinicandnnbisphosphonomethyl2aminopropionicacids |