COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES
The study presents a comparative analysis of the spectral-luminescent properties of synthesized β-diketonate coordination complexes of ytterbium with the following ligands: 2,7-dimethyl-oct-1-en-3,5-dione, 2,6-dimethyl-hept-1-en-3,5-dione, 2-methyl-5-phenylpent-1-en-3,5-dione, 2-methyl-5-biphenylpe...
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| Дата: | 2024 |
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| Автори: | , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
V.I.Vernadsky Institute of General and Inorganic Chemistry
2024
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Репозитарії
Ukrainian Chemistry Journal| _version_ | 1871466079780339712 |
|---|---|
| author | Ivakha , Nadiia Berezhnytska, Oleksandra |
| author_facet | Ivakha , Nadiia Berezhnytska, Oleksandra |
| author_institution_txt_mv | [
{
"author": "Nadiia Ivakha ",
"institution": "V.I.Vernadsky Institute of General and Inorganic Chemistry of NAS of Ukraine, Akad. Palladin Avenue, 32\/34, Kyiv, Ukraine, 03142"
},
{
"author": "Oleksandra Berezhnytska",
"institution": "V.I.Vernadsky Institute of General and Inorganic Chemistry of NAS of Ukraine, Akad. Palladin Avenue, 32\/34, Kyiv, Ukraine, 03142"
}
] |
| author_sort | Ivakha , Nadiia |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:55Z |
| description | The study presents a comparative analysis of the spectral-luminescent properties of synthesized β-diketonate coordination complexes of ytterbium with the following ligands: 2,7-dimethyl-oct-1-en-3,5-dione, 2,6-dimethyl-hept-1-en-3,5-dione, 2-methyl-5-phenylpent-1-en-3,5-dione, 2-methyl-5-biphenylpent-1-en-3,5-dione. In addition, research was conducted on polymeric compounds based on these complexes and their phenanthroline mixed-ligand derivatives.
Using a range of physicochemical analysis methods, it was established that the structure of the elementary unit during polymerization, as well as the coordination sphere of the complexes during the formation of mixed-ligand compounds, does not undergo significant changes compared to the initial β-diketonate molecules. Thermal analysis revealed a significant increase in the decomposition onset temperature of mixed-ligand and metallopolymeric compounds compared to their monomeric counterparts. Luminescence spectroscopy demonstrated that the studied samples exhibit luminescence in the infrared (IR) range.
A comparative analysis of the integral luminescence intensities of ytterbium complexes identified key factors influencing the emission characteristics. Primarily, the synthesis of mixed-ligand complexes with phenanthroline mitigates the negative effects of one of the most well-known quenching factors: OH-oscillators of water molecules, which complement the coordination sphere of monomeric ytterbium complexes. Furthermore, the synthesis of polymeric compounds based on β-diketonate complexes positively affects the luminescence, potentially due to a reduction in concentration quenching, as in polymers, the emitting centers are uniformly distributed along the macromolecular chain. Besides directly enhancing luminescent properties, this approach aims to address the practical application of the synthesized compounds since polymers are significantly easier to process and can form film materials.
Based on the conducted research, the following luminescence intensity dependencies were established: dmod>dmhpd>mbphpd>mphpd, as well as monomer-polymer-MLC-MLC polymer. As seen from the presented data, the best emission characteristics are exhibited by ytterbium mixed-ligand mono- and polycomplexes with β-diketones containing alkyl substituents. |
| doi_str_mv | 10.33609/2708-129X.90.10.2024.69-87 |
| first_indexed | 2025-09-24T17:43:58Z |
| format | Article |
| fulltext |
69
UDC 546.650+547.1’13+541.64+543.426 doi: 10.33609/2708-129X.90.10.2024.69-87
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE
PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED
β-DIKETONES.
N.B. Ivakha1,2*, O.S. Berezhnytska1,2
1 V.I.Vernadsky Institute of General and Inorganic Chemistry of the NAS of Ukraine,
32/34 Aсad. Palladin Avenue, 03142 Kyiv, Ukraine;
2 National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute»,
37 Beresteiskyi Ave., 03056 Kyiv, Ukraine
e-mail: ivakhanadiia@gmail.com
The study presents a comparative analysis of the spectral-luminescent properties of synthesized
β-diketonate coordination complexes of ytterbium with the following ligands: 2,7-dimethyl-oct-1-
en-3,5-dione, 2,6-dimethyl-hept-1-en-3,5-dione, 2-methyl-5-phenylpent-1-en-3,5-dione, 2-methyl-
5-biphenylpent-1-en-3,5-dione. In addition, research was conducted on polymeric compounds based
on these complexes and their phenanthroline mixed-ligand derivatives.
Using a range of physicochemical analysis methods, it was established that the structure of the ele
mentary unit during polymerization, as well as the coordination sphere of the complexes during the
formation of mixed-ligand compounds, does not undergo significant changes compared to the initial
β-diketonate molecules. Thermal analysis revealed a significant increase in the decomposition onset
temperature of mixed-ligand and metallopolymeric compounds compared to their monomeric coun-
terparts. Luminescence spectroscopy demonstrated that the studied samples exhibit luminescence in
the infrared (IR) range.
A comparative analysis of the integral luminescence intensities of ytterbium complexes identified
key factors influencing the emission characteristics. Primarily, the synthesis of mixed-ligand complex-
es with phenanthroline mitigates the negative effects of one of the most well-known quenching factors:
OH-oscillators of water molecules, which complement the coordination sphere of monomeric ytterbi-
um complexes. Furthermore, the synthesis of polymeric compounds based on β-diketonate complexes
positively affects the luminescence, potentially due to a reduction in concentration quenching, as in
polymers, the emitting centers are uniformly distributed along the macromolecular chain. Besides di-
rectly enhancing luminescent properties, this approach aims to address the practical application of the
synthesized compounds since polymers are significantly easier to process and can form film materials.
Based on the conducted research, the following luminescence intensity dependencies were estab-
lished: dmod>dmhpd>mbphpd>mphpd, as well as monomer-polymer-MLC-MLC polymer. As seen
from the presented data, the best emission characteristics are exhibited by ytterbium mixed-ligand
mono- and polycomplexes with β-diketones containing alkyl substituents.
Keywords: ytterbium, complex, luminescence, β-diketones, polymers.
70 ISSN 2708-129X. Укр. хім. журн., 2024
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
INTRODUCTION. The luminescence of
ytterbium(III) coordination compounds is
a subject of intensive research due to their
unique spectroscopic properties and poten-
tial applications across various fields. A key
feature of the Yb³⁺ ion is its ability to emit in
the near-infrared (NIR) range [1], making it
highly appealing for investigation. For examp
le, Yb-containing compounds can be used as
luminescent markers in immunofluorescence
analysis [2–5], as well as in laser systems, elec-
troluminescent devices, optoelectronics, and
communication technologies [6, 7].
Ytterbium complexes with organic ligands,
particularly β-diketones, are actively studied
due to their ability to provide high lumines-
cence efficiency and resistance to external in-
fluences. The ligand used for energy transfer
determines the luminescence process’s efficien-
cy. β-Diketones, which have a high absorbance
in the UV spectral range, serve as effective sen-
sitizers for luminescence due to their ability to
efficiently transfer absorbed energy to lantha-
nide ions [8, 9]. The luminescence intensity of
lanthanide ions, including Yb³⁺, in β-diketo-
nate complexes is influenced by two primary
factors: energy transfer from the triplet state
of the ligand (T₁) to the resonant level of the
Ln(III) ion and deactivation processes of the
excited levels of the Ln(III) ion. The efficiency
of energy transfer from the ligand to the metal
is determined by the energy gap (∆E) between
the triplet and resonant levels, with the optimal
∆E value depending on the type of ligand and
Ln(III) ion [9]. Experimentally, the T₁ energy
levels of ligands are determined from molecu-
lar phosphorescence spectra of their complex-
es with rare-earth metals that have an empty
(Y, La) or fully filled (Lu) 4f subshell or with
gadolinium, as the resonant 6P₇/₂ level of the
Gd(III) ion lies above the triplet levels of most
organic ligands [10].
The energy of triplet states in β-diketonates
of Ln(III) depends on the nature of the radicals
attached to the chelating [OCCCO] fragment
of the ligand and generally decreases in the fol-
lowing substituent series: aliphatic > fluorina
ted > aromatic [11]. The energy of the triplet
level also decreases with the elongation of the
aliphatic chain of the fluorinated substituent.
For instance, using fluorinated β-diketonates
of Yb³⁺ can affect luminescence intensity, re-
ducing it with the increasing chain length of
fluorinated compounds [12, 13]. In β-dike-
tonates containing aromatic substituents, a
decrease in T₁ energy levels is observed with
the increasing size of the conjugated radical
system, e.g., phenyl > biphenyl > naphthyl ≈
phenanthryl > anthracenyl. Furthermore, the
branching of the alkyl radical chain reduces
the spectroscopic properties of the complexes
due to increased steric hindrance during coor-
dination.
Most β-diketones form hexacoordinated
complexes [Ln(β-dik)₃] with lanthanide ions,
where the coordination sphere of Ln(III) is
completed by solvent molecules, particularly
water. However, as shown in many studies, wa-
ter is a primary quencher of luminescence due
to the vibrational oscillations of O–H groups,
which facilitate non-radiative energy transfer.
Replacing water with organic ligands free of
such quenchers (e.g., phenanthroline or its de-
rivatives) significantly enhances the quantum
yield of luminescence. The additional ligand
may also participate in the energy transfer
process to the Ln(III) ion, further increasing
luminescence intensity [14-16]. The degree
of luminescence quenching by water mole-
cules is inversely proportional to the energy
71https://ucj.org.ua
N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
gap ΔEg between the emitting and ground
states. For Yb(III), this gap is relatively large
(~10,000 cm⁻¹), enabling the synthesis of yt-
terbium compounds with sufficiently high
quantum yields. Among β-diketonate lantha-
nide compounds emitting in the IR region,
Yb(III) compounds exhibit higher quantum
efficiency and longer luminescence lifetimes,
with emission wavelengths of 980–1000 nm.
This is particularly advantageous for applica-
tions in bio-objects, as they are transparent in
this range [17–19].
Ytterbium(III) is a unique ion among lan-
thanides, as it has only one emission band
corresponding to the ²F₅/₂ → ²F₇/₂ transition.
Optimizing Yb³⁺ luminescence requires select-
ing appropriate ligands that act as “antennas,”
absorbing light more efficiently than the lan-
thanide ion and transferring this energy to the
excited state of Yb³⁺, thereby enhancing lumi-
nescence intensity.
However, monomeric lanthanide complexes
have several drawbacks, including insufficient
thermal stability, a tendency to aggregate, and
difficulties in obtaining film materials, lim-
iting their use as precursors for luminescent
materials. One approach to overcoming these
challenges is incorporating polymer matrices
such as polymethyl methacrylate (PMMA),
polyvinylcarbazole (PVK), or polystyrene (PS)
to create stable materials with high lumines-
cence yields [20–22]. Lanthanide ion-based
polymer compositions, prepared by dispers-
ing lanthanide salts or β-diketonate complexes
into polymer matrices, have been thoroughly
studied. Ytterbium polymer complexes are
typically formed by incorporating ytterbium
coordination compounds into a polymer ma-
trix, which acts as a stabilizing environment to
enhance luminescence stability and efficiency.
Polymers not only provide a protective coat-
ing but also influence the coordination envi-
ronment of the ion, reducing the impact of
luminescence-quenching factors such as water
or ligand vibrations. However, these products
often lack uniform metal distribution within
the polymer matrix, resulting in unpredicta-
ble properties. Polymer compounds based on
monomeric complexes are promising in terms
of stability and enhanced luminescence inten-
sity. Lanthanide complexes with unsaturated
β-diketones containing a metal-chelating ring
and a double bond represent a readily available
and promising class of compounds for synthe-
sizing polymeric metal complexes. These com-
pounds enable one-stage synthesis of macro-
molecular metal chelates and uniform metal
distribution throughout the polymer, which
generally exhibits isotropic properties.
Despite the evident potential of such com-
pounds as polymerization monomers, research
on lanthanide β-diketonates with unsaturated
substituents remains limited. Combining poly-
mers with coordination complexes reduces the
impact of external factors such as moisture or
temperature on luminescent properties. This
paves the way for stable materials for optical
communication and biosensors operating un-
der challenging conditions.
Since the 2010s, researchers at the Depart-
ment of Heterophase Synthesis of Inorganic
Compounds and Materials, Vernadsky Insti-
tute of General and Inorganic Chemistry, NAS
of Ukraine, have investigated the polymeriza-
tion of unsaturated diketonate lanthanide com-
plexes [23–25]. Radical polymerization has
been used to obtain metallopolymers based on
mono- and mixed-ligand β-diketonate com-
plexes of Ln(III) with 2,7-dimethyl-oct-1-en-
3,5-dione, 2,6-dimethyl-hept-1-en-3,5-dione,
72 ISSN 2708-129X. Укр. хім. журн., 2024
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
2-methyl-5-phenylpent-1-en-3,5-dione, 2-me-
thyl-5-biphenylpent-1-en-3,5-dione, and their
mixed-ligand derivatives with phenanthroline.
Currently, key challenges in this field in-
clude identifying optimal ligands to enhance
luminescence efficiency and refining methodo
logies for controlling the coordination envi-
ronment of ytterbium ions. Despite signifi-
cant progress in understanding luminescence
mechanisms, future research should focus on
developing new ligand types that minimize
quenching processes. Systematizing previously
obtained data, including those by the authors
of this article, is essential for these advance-
ments.
This work summarizes the results of re-
search on ytterbium metal complexes and
their polymers with unsaturated β-diketones
containing alkyl and aromatic substituents and
compares the spectral-luminescent characte
ristics of the compounds depending on the na-
ture of the substituents.
EXPERIMENT AND DISCUSSION OF RE-
SULTS. The study focused on mono-, mixed-li-
gand, and polymer coordination compounds
of ytterbium (III) with unsaturated β-dike-
tones. The synthesis of the initial β-diketones
was carried out via Claisen condensation ac-
cording to the methodology described in [26–
27] (Fig. 1).
Fig. 1 – Structural formulas of β-diketonate ligands.
The synthesis of Yb(III) complexes with
β-diketones was conducted in aqueous-alco-
hol solutions by reacting ytterbium chloride
(YbCl₃∙6H₂O) with the sodium salt of the re-
spective ligand at a molar ratio of 1:3.5 (pH
8–8.5) at room temperature. The synthesis
of mixed-ligand complexes, where phenan
throline was used as the second ligand, was
performed in alcoholic solutions with a
Yb(β-dik)₃·Phen ratio of 1:1 following the
method described in [23].
Polymer β-Diketonates of Yb (III) were
73https://ucj.org.ua
N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
obtained through the homopolymerization of
the synthesized monomeric complexes via a
radical mechanism [24]. The polymerization
was carried out at 80 °C, with azobisisobuty-
ronitrile (AIBN) chosen as the initiator for the
radical polymerization, as the polymerization
mechanism for β-diketonates of lanthanides is
identical to that of vinylmonomers.
All synthesized compounds were investigat-
ed using IR spectroscopy, DRS, thermogravim-
etry, and luminescence analysis.
IR spectra were recorded using a Specord
M80 spectrometer in the range of 400–
4000 cm⁻¹ in KBr pellets.
Diffuse reflectance spectra in the range of
300 – 1100 nm were registered using a UV-
VIS-IR Shimadzu UV-3600 spectrophotome-
ter.
The hydratecomposition of the synthesized
compounds and their thermal stability were
determined using DTA. Thermograms were
recorded using a Q–1500°D derivatograph sys-
tem from F. Paulik, J. Paulik, L. Erdey, in the
temperature range of 20–500 °C at a heating
rate of 5 °C/min in a platinum crucible with
a carrier (anhydrous Al₂O₃) under a static air
atmosphere.
The excitation and emission spectra of so
lid complexes were recorded using a Fluorolog
FL 3-22 spectrofluorimeter, Horiba Jobin Yvon
(Xe lamp 450 W), with a light filter OS 11, fol-
lowed by corrections accounting for the emis-
sion distribution of the xenon lamp and the
sensitivity of the photomultiplier tube (PMT).
For the IR region, InGaAs photoresistors
(DSS-IGA020L, Electro-Optical Systems, Inc,
USA, cooled to liquid nitrogen temperatures)
were used as radiation receivers.
The coordination mode of β-diketonates
with the Yb(III) ion was determined by IR
spectroscopy, which, in cases where direct
X-ray structural analysis is not possible, al-
lows the structural identification of β-dike-
tonate complexes. Fig. 2 shows a typical IR
spectrum of Yb(III) coordination compounds
with β-diketonate ligands containing unsatu-
rated substituents in the α-position, and Table
1 summarizes the main vibrational frequencies
and their assignments for all studied ytterbi-
um-containing β-diketonates.
The main characteristic vibration bands of
complex β-diketonate compounds are located
in the region of 1500–1700 cm-1, which cor-
respond to stretching vibrations of carbonyl
groups and multiple CC bonds of the dicarbo-
nyl fragment [28, 29].
Since there is a delocalization of electron
density in the diketonate fragment, the stretch-
ing vibration bands occupy an intermediate
position between the stretching vibrations of
single C-O and C-C and double C=O and C=C
bonds. Thus, the band with a higher frequency
(~1580–1610 cm-1) corresponds to the sym-
metric stretching vibration of the bond (C O),
and with a lower frequency (~1540–1580 cm-1)
to the asymmetric stretching vibration of the
bond (С С). It should be noted that for mo
nomeric and polymeric complexes with mbph-
pd and Рhen, the splitting of the νs(C O) band
into 2 components is observed, which may be
due to the structural inequivalence of some
chelate rings. For most polymeric compounds,
the ν(С=С) band appears in the region of
~1650–1660 cm-1 as a shoulder, indicating the
presence of terminal unsaturated groups, and
in the case of the [Yb(mphpd)3Phen]n comp
lex, the average intensity of this band may indi-
cate an incomplete polymerization process and
the formation of a certain number of oligome
ric products.
74 ISSN 2708-129X. Укр. хім. журн., 2024
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
Fig. 2. – IR spectrum of the complex Yb(mphpd)3⋅2H2O.
Table 1.
Assignment of vibration bands in the IR spectra of Yb(III) β-diketonate (cm-1)
Complex ν(Yb–O)+δhel. ring ν (Yb-N) νas(С С) νs(C O) νs(C=C)
Yb(mphpd)3∙3H2O 421, 453, 490, 505, 545 - 1580 1596 1655
Yb(mphpd)3∙Рhen 405, 464, 487, 504, 545 467 1582 1601 1655
Yb(mbphpd)3∙2H2O 411, 429, 450 - 1560 1586 1653
Yb(mbphpd)3∙Рhen 410, 428, 451 474 1558 1575, 1607 1653
Yb(dmhpd)3∙2H2O 408,430, 478, 501, 526 - 1555 1555 1640, 1660
Yb(dmhpd)3∙Phen 420, 435, 481, 495, 507 477 1552 1590 1630
Yb(dmod)3∙2H2O 456, 470, 489, 520 - 1542, 1560 1590 1680
Yb(dmod)3∙Phen 450, 468, 470, 515 480 1547 1592 1650
[Yb(mphpd)3]n 421, 453, 490, 505, 545 - 1560 1590 1651sh.
[Yb(mphpd)3∙Рhen]n 410, 420, 435, 495, 507 481 1565 1585 1650
[Yb(mbphpd)3]n 406, 427, 455 - 1559 1581, 1599 1652sh.
[Yb(mbphpd)3∙Phen]n 409, 432, 461 481 1561 1580, 1607 1651sh.
[Yb(dmhpd)3]n 419, 426, 484, 511 - 1537 1578 1659sh.
[Yb(dmhpd)3∙Phen]n 417, 429, 475, 515 468 1535 1577 1653sh.
[Yb(dmod)3]n 421, 435, 481, 511 - 1542 1581 1661sh.
[Yb(dmod)3∙Phen]n 419, 439, 474, 518 465 1544 1584 1663sh.
Fig. 2. – IR spectrum of the complex Yb(mphpd)32H2O.
Table 1.
Assignment of vibration bands in the IR spectra of Yb(III) -diketonate(cm-1).
Complex (Yb–O)+hel. ring (Yb-N) as(С С) s(C O) s(C=C)
Yb(mphpd)3∙3H2O 421, 453, 490, 505, 545 – 1580 1596 1655
Yb(mphpd)3Рhen 405, 464, 487, 504, 545 467 1582 1601 1655
Yb(mbphpd)3∙2H2O 411, 429, 450 – 1560 1586 1653
Yb(mbphpd)3Рhen 410, 428, 451 474 1558 1575, 1607 1653
Yb(dmhpd)3∙2H2O 408,430, 478,501, 526 – 1555 1555 1640, 1660
Yb(dmhpd)3Phen 420, 435, 481, 495, 507 1552 1590 1630
Yb(dmod)3∙2H2O 456, 470, 489, 520 – 1542, 1560 1590 1680
Yb(dmod)3Phen 450, 468, 470, 515 480 1547 1592 1650
[Yb(mphpd)3]n 421, 453, 490, 505, 545 – 1560 1590 1651
[Yb(mphpd)3Рhen]n 410, 420, 435, 495, 507 481 1565 1585 1650
[Yb(mbphpd)3]n 406, 427, 455 – 1559 1581, 1599 1652 пл.
[Yb(mbphpd)3∙Phen]n 409, 432, 461 481 1561 1580, 1607 1651пл
[Yb(dmhpd)3]n 419, 426, 484, 511 – 1537 1578 1659
[Yb(dmhpd)3Phen]n 417, 429, 475, 515 468 1535 1577 1653
[Yb(dmod)3]n 421, 435, 481, 511 – 1542 1581 1661
[Yb(dmod)3Phen]n 419, 439, 474, 518 465 1544 1584 1663
In the low-frequency region of the spectra (400–600 cm-1) a set of bands appears, which
corresponds to a combination of stretching vibrations of the Yb-O bond and deformation vibrations
of the chelatering. At the same time, the frequencies of the δring and ν(Yb–O) differ slightly for
different complexes, since the structure of the [OCCCO] fragment of the ligands practically does
not depend on the type of substituents in them, which may indicate a close coordination
environment of Yb(ІІІ) in all the studied compounds. For complexes with phenanthroline in the IR
spectra in the range of 465–480 cm-1, bands corresponding to the stretching vibration of Yb-N are
additionally observed. Their presence confirms the formation of mixed-ligand complexes. The
position of the ν vibration of the Yb-O bonds in the IR spectra of polymer and monomer complexes
is almost the same, and the slight shift of the band data to the low-frequency region (up to 20 cm-1)
for polymer complexes is probably due to the deformation of the coordination site. That is, during
polymerization, the immediate environment of the lanthanide ion practically does not change in
comparison with metal complexes.
75https://ucj.org.ua
N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
In the low-frequency region of the spectra
(400–600 cm-1) a set of bands appears, which
corresponds to a combination of stretching
vibrations of the Yb-O bond and deforma-
tion vibrations of the chelate ring. At the same
time, the frequencies of the δring and ν(Yb–O)
differ slightly for different complexes, since the
structure of the [OCCCO] fragment of the li-
gands practically does not depend on the type
of substituents in them, which may indicate
a close coordination environment of Yb(ІІІ)
in all the studied compounds. For complexes
with phenanthroline in the IR spectra in the
range of 465–480 cm-1, bands corresponding
to the stretching vibration of Yb-N are addi-
tionally observed. Their presence confirms the
formation of mixed-ligand complexes. The po-
sition of the ν vibration of the Yb-O bonds in
the IR spectra of polymer and monomer comp
lexes is almost the same, and the slight shift of
the band data to the low-frequency region (up
to 20 cm-1) for polymer complexes is probably
due to the deformation of the coordination site.
That is, during polymerization, the immediate
environment of the lanthanide ion practical-
ly does not change in comparison with metal
complexes.
In the region of 3200–3600 cm-1 for all
monomer complexes, there is a broad vibration
band of the O-H groups, which is associated
with the addition of water molecules to the co-
ordination sphere of ytterbium(III) complexes.
In the case of phenanthroline complexes, this
band is not observed in the IR spectra, which
indicates the displacement of water molecules
from the inner coordination sphere due to the
coordination of the Phen molecule to the cen-
tral ion. In the case of polymer complexes, the
ν(O–H) band has a low intensity in the given
spectral range. This can be explained by the
presence of a small amount of occluded water
in the structure of metal polymers.
The similarity of the IR spectra of metal
chelate monomers, mixed ligand and polycom-
plexes suggests the proximity of the ligand en-
vironment of metal ions in these compounds.
Based on the analysis of the IR spectra, it
can be unequivocally stated that in the com-
plexes Yb(β-dik)3∙2Н2О the metal ion coordi-
nates the β-diketonate ligands bidentately-cy-
clically with a delocalized system of π-bonds
in the chelate ring. In this case, six-membered
metallocycles are formed (Fig. 3).
а b
Fig. 3 – Schematic structure of Yb(III) complexes: Yb(β-dik)3 (a), Yb(β-dik)3Рhen (b).
In the region of 3200–3600 cm-1 for all monomer complexes, there is a broad vibration band
of the O-H groups, which is associated with the addition of water molecules to the coordination
sphere of ytterbium(III) complexes. In the case of phenanthroline complexes, this band is not
observed in the IR spectra, which indicates the displacement of water molecules from the inner
coordination sphere due to the coordination of the Phenmolecule to the centralion. In the case of
polymer complexes, the ν(O–H) band has a low intensity in the given spectral range. This can be
explained by the presence of a small amoun to foccludedwaterinthestructureofmetalpolymers.
The similarity of the IR spectra of metalchelatemonomers, mixed ligand and polycomplexes
suggests the proximity of the ligand environment of metal ions in these compounds.
Based on the analysis of the IR spectra, it can be unequivocally stated that in the complexes
Yb(β-dik)3∙2Н2О the metal ion coordinates theβ-diketonate ligands bidentately-cyclically with a
delocalized system of π-bonds in the chelatering. In this case, six-membered metallocycles are
formed (Fig. 3).
а b
Fig. 3 – Schematic structure of Yb(III) complexes: Yb(β-dik)3 (a), Yb(β-dik)3Рhen (b).
From the point of view of the possible practical application of the synthesized
coordination compounds of ytterbium (III), an important stage of the study is the thermal analysis,
in particular the determination of the thermal stability of the synthesized compounds. The thermal
stability of Yb(III) complexes with unsaturated β-diketonesis analyzed in sufficient detail in [23,
24]. The generalization of there sults of thermal studies of Yb(III) β-diketonates shows that the
thermal decomposition of all compounds proceeds in the same way:
– dehydration of monomeric complexes Yb(β-dik)3, regardless of the β-diketone, occurs
in the temperature range of 120–127ºС and is accompanied by endoeffects, which corresponds to
the elimination of two coordinated water molecules;
– for mixed-ligand compounds, the absence of this thermal effect indicates there
placement of water molecules by a phenanthroline molecule. The elimination of a phenanthroline
molecule begins at about 170ºС;
– in the case of polymer complexes at a temperature of ~ 130ºС, a slight endo effect is
observed, which may indicate the elimination of water remaining in the voids of the polymermatrix
during polymerization of the monomer;
– at a temperature of>180ºС, polymerization of complexes occurs with out aninitiator;
– in the temperature range of 250–450ºС, oxidative thermal destruction of all complexes
is accompanied by a number of exoeffects, which is due to the decomposition of organic fragments
of the molecule, and the final decomposition products are non-stoichiometric ytterbium(III) oxides;
– the thermal stability of the studied compounds increases in the following order:
monocomplexes>mixed-ligand complexes>metalpolymers>mixed-ligand metalpolymers.
The temperature at the on set of degradation varies from 250ºС (formonomers) to 375ºС
(forpolymers). This effect may be due to the denser, ordered packing of polycomplexes with a
complex, possiblybranched, system of bonds.
The geometry evaluation, coordination number, and determination of the symmetry of the
nearest coordination environment around the Yb(III) ion were carried out based on the analysis of
the position and intensity of the f-f transition bands in the diffuse reflectance (DR) spectra of the
studied compounds.
76 ISSN 2708-129X. Укр. хім. журн., 2024
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
From the point of view of the possible prac-
tical application of the synthesized coordina-
tion compounds of ytterbium (III), an impor-
tant stage of the study is the thermal analysis,
in particular the determination of the thermal
stability of the synthesized compounds. The
thermal stability of Yb(III) complexes with un-
saturated β-diketonesis analyzed in sufficient
detail in [23, 24]. The generalization of the
results of thermal studies of Yb(III) β-diketo-
nates shows that the thermal decomposition of
all compounds proceeds in the same way:
– dehydration of monomeric complexes
Yb(β-dik)3, regardless of the β-diketone,
occurs in the temperature range of 120–
127 ºС and is accompanied by endoeffects,
which corresponds to the elimination of
two coordinated water molecules;
– for mixed-ligand compounds, the ab-
sence of this thermal effect indicates the
replacement of water molecules by a phe-
nanthroline molecule. The elimination
of a phenanthroline molecule begins at
about 170 ºС;
– in the case of polymer complexes at a tem-
perature of ~ 130 ºС, a slight endoeffect is
observed, which may indicate the elimi
nation of water remaining in the voids of
the polymer matrix during polymeriza-
tion of the monomer;
– at a temperature of > 180 ºС, polymeriza-
tion of complexes occurs without an ini
tiator;
– in the temperature range of 250–450 ºС,
oxidative thermal destruction of all comp
lexes is accompanied by a number of exo
effects, which is due to the decomposition
of organic fragments of the molecule,
and the final decomposition products are
non-stoichiometric ytterbium(III) oxides;
– the thermal stability of the studied com-
pounds increases in the following order:
monocomplexes>mixed-ligand complex-
es>metalpolymers>mixed-ligand metal-
polymers.
The temperature at the onset of degradation
varies from 250 ºС (for monomers) to 375 ºС
(for polymers). This effect may be due to the
denser, ordered packing of polycomplexes with
a complex, possibly branched, system of bonds.
The geometry evaluation, coordination
number, and determination of the symmetry of
the nearest coordination environment around
the Yb(III) ion were carried out based on the
analysis of the position and intensity of the f-f
transition bands in the diffuse reflectance (DR)
spectra of the studied compounds.
In Fig. 4, as an example, the DR spectra of
Yb(III) complexes with 2,7-dimethyl-octen-
1-dione-3,5 are shown, while Table 2 lists the
characteristics of the 2F7/2 → 2F5/2 transition for
all synthesized complexes. In the DR spectra of
all complexes, one 2F7/2 → 2F5/2 transition cha
racteristic of the Yb(III) ion is observed, with a
maximum in the range of 970–980 nm. At the
same time, the overall appearance of the spectra
for both monomeric and polymeric complexes is
similar, indicating that polymerization does not
affect the geometry and structure of the coordi-
nation polyhedron of the lanthanide. The slight
difference in λmax values is due to the geometric
structure of the substituents in the β-diketonate
ligands, which have different λmax values for al-
lowed π–π* transitions in the near ultraviolet
region (200–400 nm). For example, replacing
a biphenyl substituent with an alkyl substituent
causes a significant shift in the absorption maxi
mum and broadening of spectral lines, which is
due to different energy characteristics of the of
the ligands being studied [10, 24].
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N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
Fig. 4 – Diffuse reflection spectra of complexesYb(dmоd)3·2H2O (1), Yb(dmоd)3·Phen (2),
[Yb(dmod)3]n (3), [Yb(dmod)3⋅Phen]n (4) [24].
Table 2
Position of the maxima of the 2F
7/2
→2F
5/2
transitions in the DRS
of Yb(III) complexes with unsaturated β-diketones
Complex λmax, nm β δ b1/2
Yb(mphpd)3∙3H2O 975 0,9945 0,5530 0,05244
Yb(mphpd)3∙Рhen 978 0,9968 0,3210 0,04000
Yb(mbphpd)3∙2H2O 974 0,9957 0,4319 0,04637
Yb(mbphpd)3∙Рhen 976 0,9941 0,5935 0,05431
Yb(dmhpd)3∙2H2O 973 0,998 0,2004 0,03162
Yb(dmhpd)3∙Phen 974 0,998 0,2004 0,03162
Yb(dmod)3∙2H2O 975 0,9951 0,4924 0,04950
Yb(dmod)3∙Phen 975.5 0,9969 0,3110 0,03937
[Yb(mphpd)3]n 971 0,9978 0,2205 0,03317
[Yb(mphpd)3∙Рhen]n 973 0,9962 0,3814 0,04359
[Yb(dmhpd)3]n 972 0,998 0,2004 0,03162
[Yb(dmhpd)3∙Phen]n 973.5 0,997 0,3009 0,03873
[Yb(dmod)3]n 973 0,9978 0,2205 0,03317
[Yb(dmod)3∙Phen]n 972 0,9947 0,5328 0,05148
In Fig. 4, as an example, the DR spectra of Yb(III) complexes with 2,7-dimethyl-octen-1-
dione-3,5 are shown, while Table 2 lists the characteristics of the 2F7/2 → 2F5/2 transition for all
synthesized complexes. In the DR spectra of all complexes, one 2F7/2 → 2F5/2 transition
characteristic of the Yb(III) ion is observed, with a maximum in the range of 970-980 nm. At the
same time, the overall appearance of the spectra for both monomeric and polymeric complexes is
similar, indicating that polymerization does not affect the geometry and structure of the
coordination polyhedron of the lanthanide. The slight difference in λmax values is due to the
geometric structure of the substituents in the β-diketonate ligands, which have different λmax values
for allowed π–π* transitions in the near ultraviolet region (200 – 400 nm). For example, replacing a
biphenyl substituent with an alkyl substituent causes a significant shift in the absorption maximum
and broadening of spectral lines, which is due to different energy characteristics of the of the
ligands being studied [10, 24].
Fig. 4 – Diffuse reflection spectra of complexesYb(dmоd)3·2H2O (1), Yb(dmоd)3·Phen (2), [Yb(dmod)3]n (3)
, [Yb(dmod)3Phen]n (4) [24].
Table 2
Position of the maxima of the
2
F7/2 →
2
F5/2transitions in the DRS of Yb(III) complexes with unsaturated
-diketones.
Complex λmax, nm β b1/2
Yb(mphpd)3∙3H2O 975 0,9945 0,5530 0,05244
Yb(mphpd)3Рhen 978 0,9968 0,3210 0,04000
Yb(mbphpd)3∙2H2O 974 0,9957 0,4319 0,04637
Yb(mbphpd)3Рhen 976 0,9941 0,5935 0,05431
Yb(dmhpd)3∙2H2O 973 0,998 0,2004 0,03162
Yb(dmhpd)3Phen 974 0,998 0,2004 0,03162
Yb(dmod)3∙2H2O 975 0,9951 0,4924 0,04950
Yb(dmod)3Phen 975.5 0,9969 0,3110 0,03937
[Yb(mphpd)3]n 971 0,9978 0,2205 0,03317
[Yb(mphpd)3Рhen]n 973 0,9962 0,3814 0,04359
[Yb(dmhpd)3]n 972 0,998 0,2004 0,03162
[Yb(dmhpd)3Phen]n 973.5 0,997 0,3009 0,03873
[Yb(dmod)3]n 973 0,9978 0,2205 0,03317
[Yb(dmod)3Phen]n 972 0,9947 0,5328 0,05148
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COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
It should be noted that for mixed-ligand
phenanthroline complexes, regardless of the li-
gand, there is a slight (~30 cm-1) bathochromic
shift of the band maximum and a significant
increase in absorption intensity. Probably, the
N,N-donor ligand makes the structure of the
complexes more rigid due to the axial distor-
tion of the f-metal coordination site during
the coordination of the Phen molecule with
two nitrogen heteroatoms, providing effective
shielding of the Yb3+ nucleus from external
quenching compared to the original complexes
without Рhen.
However, in general, the shape and position
of the 2F7/2 →
2F5/2 transition band for all ytterbi-
um compounds are almost the same, which in-
dicates a similar coordination environment of
Yb(ІІІ) in all synthesized samples. At the same
time, the absorption maxima for monocomp
lexes are close to λmax of the aquated Ybaq3+ ion
(973 nm), which indicates a close symmetry of
the nearest coordination environment of the
ytterbium ion in complexes and inorganic salts
[30]. Thus, it can be assumed that the synthe-
sized Yb(III) β-diketonates are characterized
by C4v symmetry, the lanthanide coordination
number = 8, to which the coordination poly-
hedron corresponds is a deformed square an-
tiprism.
For all synthesized compounds, the covalent
bond parameters were calculated: the nephe
loxetic parameter (β), the covalent parameter
(b1/2) and the Sinha parameter (δ) (Table 2).
As can be seen from the data in Table 2, for all
complexes the values of β are close to 1, which
may indicate a high ionicity of the Yb–O bond
[31]. The parameters b1/2 and δ characterize the
degree of covalent bond of the lanthanide with
the donor ligand molecules. The largest va
lues of b1/2 are found in monomeric complexes,
which also correspond to the largest values of
δ, which indicates a smaller contribution of the
covalent component to the Yb–O bond. Dur-
ing polymerization of the complexes, the va
lues of b1/2 decrease by almost 1.5 times, which
indicates an increase in the covalent bond
when transitioning from mononuclear to poly-
meric complexes. This is also confirmed by the
values of the parameter δ: δ[Yb(β-dik)3]n<δYb(β-dik)3.
The lowest values of covalence parameters are
found in ligands with alkyl substituents (2,7-di-
methyl-oct-1-en-3,5-dione, 2,6-dimethyl-hept-
1-en-3,5-dione), which are structurally less
bulky than β-diketones with phenyl substitu
ents (2-methyl-5-phenylpent-1-en-3,5-dione,
2-methyl-5-biphenylpent-1-en-3,5-dione).
Therefore, dmhpd/dmod easily “fit” to the cen-
tral atom, while bulky mphpd/mbphpd mole-
cules do not create additional shielding of the
emitting centers and can form a more ionic
bond with the central atom. Thus, a decrease
in the parameter b1/2 in the order mphpd>
mbphpd>dmod>dmhpd indicates a decrease
in the covalent contribution to the metal-li-
gand bond. It is clear that in the case of poly-
mers, the contribution of the covalent compo-
nentis greater, which is due to the insignificant
deformation of the coordination site due to the
polymerization processes, while the structure
and symmetry of the complexes do not under
go major changes. Due to the weakening of the
ionicity of the bond with increasing covalency,
the intensity of the radiation can increase due
to the decrease in the shielding of the emitting
ion. However, this is not the only factor affect-
ing the intensity of luminescence.
For all obtained Yb(III) complexes, a char-
acteristic 4f-luminescence is observed in the
near-IR region of the spectrum (λlum. = 980–
1015 nm, transition2F5/2→ 2F7/2).
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N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
An important condition for observing in-
tense luminescence is the optimal energy gap
between the triplet level of the ligand (ET) and
the resonance level of the lanthanide. To expe
rimentally determine the energy of the triplet
levels of β-diketones, the fluorescence spectra
of Gd(III) complexes were studied, which were
synthesized by a similar method as the Yb(III)
complexes (Fig. 5, Table 3) [10].
Table 3.
Calculated energies of the triplet levels
of the ligands.
Ligand ET (cm-1) Δ ET – ЕYd(2F5/2),(cm-1)
dmhpd 19570 9370
[dmhpd]n 19230 9030
dmod 19350 9150
[dmod]n 18900 8700
mphpd 19490 9290
[mphpd]n 20600 10400
mbhppd 21000 10800
[mbhppd]n 20750 10550
Fig. 5 – Phosphorescence spectra of some
gadolinium complexes, Т=77 K.
The calculated values of the triplet energy
levels of the ligands and the width of the energy
gap between the ET of the ligands and the reso
nanсе 2F5/2 level of Yb(III) (10330 cm-1) show
that in all cases, intramolecular energy trans-
fer to the metal ion is fundamentally possible,
which indicates the ability of the complexes to
exhibit effective 4f-luminescence.
Fig. 6 (a, b, c) presents the excitation and
luminescence spectra of ytterbium compounds
with the studied β-diketones. The excitation
spectra of the complexes (Fig. 6, a) are similar
for all compounds regardless of the ligands and
represent broad structured bands in the region
of 230–410 nm, corresponding to the π-π*
transitions of the β-diketonate fragment. The
partial overlap of the ligand absorption spec-
tra and the excitation spectra of the complexes
indicates the sensitization of 4f-luminescence
due to intramolecular energy transfer from the
β-diketonate fragment to the ytterbium ion.
Compared with the absorption of the organic
ligand, the bands of the f-f transitions of Yb(III)
are quite weak, which confirms the predomi-
nant sensitization due to the excitation of the
ligand compared to the direct excitation of the
lanthanide ion.
In the luminescence spectra of Yb(III)
β-diketonates, the most intense is one band,
which corresponds to the transition from
the excited level 2F5/2→
2F7/2 in the region λmax=
978–985 nm. Table 5 shows the position of this
band for all synthesized ytterbium complex-
es, and also the calculated integral intensities
of luminescence of the samples. In addition to
the narrow peak, a broad band at λ≈1000nm
is observed in the spectra, which corresponds
to optical transitions of an electron between
the Stark sublevels of the ion and depends
on the symmetry of the crystal field of the li-
gand. The difference in the shape of the spec-
tral lines and the integrated intensity for dif-
ferent ligands can be due to both the different
[dmhpd]n 19230 9030
dmod 19350 9150
[dmod]n 18900 8700
mphpd 19490 9290
[mphpd]n 20600 10400
mbhppd 21000 10800
[mbhppd]n 20750 10550
Fig. 5 – Phosphorescence spectra of some gadolinium complexes, Т=77 K.
Fig. 6 (a, b, c) presents the excitation and luminescence spectra of ytterbium compounds
with the studied β-diketones. The excitation spectra of the complexes (Fig. 6, a) are similar for all
compounds regardless of the ligands and represent broad structured bands in the region of 230–410
nm, corresponding to the π-π* transitions of the β-diketonate fragment. The partial over lap of the
ligand absorption spectra and the excitation spectra of the complexes indicates the sensitization of
4f-luminescence due to intramolecular energy transfer from the β-diketonate fragment to the
ytterbiumion. Compared with the absorption of the organic ligand, the bands of the f-f transitions of
Yb(III) are quite weak, which confirms the predominant sensitization due to the excitation of the
ligand compared to the direct excitation of the lanthanide ion.
In the luminescence spectra of Yb(III) β-diketonates, the most intense is one band,
which corresponds to the transition from the excited level 2F5/2→2F7/2 in the region λmax= 978–985
nm. Table 5 shows the position of this band for all synthesized ytterbium complexes, and also the
calculated integral intensities of luminescence of the samples. In addition to the narrow peak, a
broad band at λ≈1000nm is observed in the spectra, which corresponds to optical transitions of an
electron between the Stark sublevels of the ion and depends on the symmetry of the crystalfield of
the ligand. The difference in the shape of the spectral lines and the integrated intensity for different
ligands can be due to both the different structure of the ligands and the screening of the emitting
centers by phenyl substituents of aromatic β-diketonesorphenanthroline. Thus, the maximum
relative emission intensity is observed for complexes with dmod, which is up to ≈ 6 (for monomers)
and ≈ 1.5 (for polymers) times higher than the relative intensity for complexes with other β-
diketones, which can be explained by the positive effect of the additional methylene group of the
hydrocarbonradicalind mod, which in a certain way weakens the bond of the Yb(III) ion with the
ligand due to there distribution of the electrondensity in the molecule, and, presumably, contributes
to a more efficient transfer of energy from the ligand to the metal.
80 ISSN 2708-129X. Укр. хім. журн., 2024
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
structure of the ligands and the screening of
the emitting centers by phenyl substituents of
aromatic β-diketones or phenanthroline. Thus,
the maximum relative emission intensity is
observed for complexes with dmod, which is
up to ≈ 6 (for monomers) and ≈ 1.5 (for pol-
ymers) times higher than the relative intensity
for complexes with other β-diketones, which
can be explained by the positive effect of the
additional methylene group of the hydrocar-
bon radical in dmod, which in a certain way
weakens the bond of the Yb(III) ion with the
ligand due to there distribution of the electron
density in the molecule, and, presumably, con-
tributes to a more efficient transfer of energy
from the ligand to the metal.
a b
c
Fig. 6 – Excitation (a) and luminescence (b, c) spectra of Yb(III) β-diketonates (λеm.=365 nm, Т=293К).
The minimum value of Ilum is exhibited by complexes based on methacroylacetophenone
(Table 4), which maybe due to the structural features of the methacroylace to phenone molecule,
namely, the screening of the emitting centers of the ytterbium ion by the aromaticring. The higher
integral intensity of complexes based on mbphpd compared to mphpd could be explained by an
antenna effector stacking-stacking interactions in the biphenyl substituent.
Table 4.
Characteristics of luminescence spectra of complexes with unsaturated diketones.
Complex λlum, nm Ilum. 10-4,a.u. Complex λlum, nm Ilum. 10-4,a.u.
Yb(mphpd)3∙3H2O 978 309580.54 Yb(dmhpd)3∙2H2O 980,1005,2054 1758376.24
Yb(mphpd)3Рhen 978 1758712.35 Yb(dmhpd)3Phen 984 5416980.82
[Yb(mphpd)3]n 978 477261.68 [Yb(dmhpd)3]n 982 2076017.15
[Yb(mphpd)3Рhen]n 979, 1001, 1037 114618.03 [Yb(dmhpd)3Phen]n 985,1020 5927269.72
Yb(mbphpd)3∙2H2O 980 514338.36 Yb(dmod)3∙2H2O 983 3348353.14
Yb(mbphpd)3Рhen 982 5446747.50 Yb(dmod)3Phen 982 6284268.62
[Yb(mbphpd)3]n 981 529824.78 [Yb(dmod)3]n 985 2693542.02
[Yb(mbphpd)3∙Phen]n 982,1014,1038 6367072.55 [Yb(dmod)3Phen]n 981,985,987,990 9429427.30
For the all studied complexes, the integral luminescence intensity of
metallopolymersexceeds the luminescence of their monomeric analogues, which is due to the
presence of a larger number of emitting centers in [Yb(β-dik)3]n (Fig. 5, b, c). In addition, the higher
Fig. 6 – Excitation (a) and luminescence (b, c) spectra of Yb(III) β-diketonates
(λеm.=365 nm, Т=293К).
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N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
The minimum value of Ilum is exhibited by
complexes based on methacroylacetophenone
(Table 4), which maybe due to the structural
features of the methacroylacetophenone mo
lecule, namely, the screening of the emitting
centers of the ytterbium ion by the aromatic-
ring. The higher integral intensity of comp
lexes based on mbphpd compared to mphpd
could be explained by an antenna effect or
stacking-stacking interactions in the biphenyl
substituent.
Table 4.
Characteristics of luminescence spectra of complexes with unsaturated diketones.
Complex λlum, nm Ilum.⋅ 10-4,a.u. Complex λlum, nm Ilum.⋅ 10-4,a.u.
Yb(mphpd)3∙3H2O 978 309580.54 Yb(dmhpd)3∙2H2O 980, 1005, 2054 1758376.24
Yb(mphpd)3⋅Рhen 978 1758712.35 Yb(dmhpd)3⋅Phen 984 5416980.82
[Yb(mphpd)3]n 978 477261.68 [Yb(dmhpd)3]n 982 2076017.15
[Yb(mphpd)3⋅Рhen]n
979, 1001,
1037 114618.03 [Yb(dmhpd)3⋅Phen]n 985,1020 5927269.72
Yb(mbphpd)3∙2H2O 980 514338.36 Yb(dmod)3∙2H2O 983 3348353.14
Yb(mbphpd)3⋅Рhen 982 5446747.50 Yb(dmod)3⋅Phen 982 6284268.62
[Yb(mbphpd)3]n 981 529824.78 [Yb(dmod)3]n 985 2693542.02
[Yb(mbphpd)3∙Phen]n
982, 1014,
1038 6367072.55 [Yb(dmod)3⋅Phen]n
981, 985, 987,
990 9429427.30
For the all studied complexes, the integral
luminescence intensity of metallo polymers
exceeds the luminescence of their monomer-
ic analogues, which is due to the presence of
a larger number of emitting centers in [Yb(β-
dik)3]n (Fig. 5, b, c). In addition, the higher
luminescence intensity of polymeric metal
complexes enhanced with monomeric ones
may be due to an increase in the molecular
weight of the metallopolymer, which, in turn,
contributes to a decrease in exchange inter-
actions between lanthanide ions, and, conse-
quently, to a decrease in energy loss, and also
contributes to a more efficient transfer of ener-
gy from the molecular levels of the polymer to
the resonance level of Yb(III).
The highest luminescence intensity is ob-
served in the mixed ligand complexes, re-
gardless of the β-diketonate ligand. Thus, for
monomeric dimethyloctene and dimethylhep-
tene complexes Ilum. increases by 2 and 3 times,
respectively, and for complexes with mphpd
and mbphpd Ilum. increases by 6 and 10 times,
respectively. The tendency to increase the in-
tensity of luminescence is also preserved for
polymeric mixed-ligand compounds, with this
value of Ilum. individual monoligand polymers
increases by up to 1.5 times. The exception is
the complex with methacroylacetophenone,
the luminescence of which decreases upon
formation of a mixed-ligand polymer com-
plex. The obtained data can be explained by
two reasons, one of which is possibly due to
the removal of OH oscillators from the inner
sphere of the complexes, which quench the
luminescence of the compounds [32]. On the
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COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
other hand, due to the additional coordination
of the REE ion of the neutral phenanthroline
ligand, intramolecular energy transfer occurs
from Phen to β-dik, after ET(β-dic)<ET(Phen)
(ET(Phen) = 21480 cm-1), which only leads to
an additional antenna effect.
As can be seen from Fig. 5c, for the homo
polymer [Yb(dmod)3∙Phen]n, a broadening and
splitting of the 2F5/2 → 2F7/2 transition line into
4 components at 981, 985, 987, and 990 nm is
observed. Such splitting indicates the presence
of several emitting centers. This may be due to
the formation of complexes with different de-
grees of polymerization. It is known that com-
pounds with long alkyl substituents polymerize
with a low degree of conversion, which is due
to the transfer of the chain to the monomer,
therefore, during polymerization, several poly-
mer compounds of different molecular weights
and, accordingly, different optical properties
can be formed.
Summarizing the data of the luminescent
properties of Yb(III) complexes with unsatu-
rated β-diketones, we can draw the following
conclusions (Fig. 7):
Fig. 7 – Diagram of the change of integral intensity of luminescence inYb(III) β-diketonates depending on
the nature of the substituents in the ligands molecules.
According to the obtained data for the studied Yb(III) complexes with unsaturated β-
diketones, the following excitation and energy transfer scheme can be proposed (Fig. 8)
Fig. 8 – Scheme of energy transfer from an organic ligand to the Yb(III) (GSA – ground state
absorption).
As calculated above, there is a significant energy gap between the triplet state of the ligand
and the excited state of the ytterbium (III) ion. In addition, for Yb3+ ions, the 2F5/2 fluorescence level
lies∼10,000 cm−1 above the 2F7/2 ground state, which in this case allows us to speak about vibronic
interaction or theme chan is mof internal electrontransfer from the ligand to the metal [33]. We
propose that the energy transfer from the ligand triplet state to the excited level of Yb³⁺, facilitated
by vibronic coupling, accounts for the population of the Yb³⁺ excited state, which can then relax
radiatively to the ground state by emitting photons at approximately 980 nm. This indicates an
effective antenna effect, since the excitation energy photogenerated inorganic ligands is quickly
Fig. 7 – Diagram of the change of integral intensity of luminescence inYb(III) β-diketonates
depending on the nature of the substituents in the ligands molecules.
• the intensity and efficiency of lumines-
cence directly depend of the nature of the sub-
stituents in the ligand molecules (aliphatic sub-
stituents in the α-position contribute to more
efficient emission in the near-IR range than
aryl ones) and increase in the order dmod>
dmhpd>mbphpd>mphpd;
• the luminescence intensity of Yb(III)
complexes with phenanthroline for all synthe-
sized compounds is higher than for monoli-
gand complexes, which is due to the leveling
of the gassing action of water molecules and
additional energy transfer and luminescence
sensitization;
• the luminescence intensity of metallopoly
mers is higher than that of monomeric comp
lexes. Not a very significant difference in the
integral intensity of luminescence between
monomeric and polymeric samples maybe
due to the complex structure of ytterbium (III)
83https://ucj.org.ua
N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
β-diketonate complexes, which prevents the
production of polymers with high molecular
weight;
• the change in the luminescent properties
of Yb(III) β-diketonates occurs in the follow-
ing series: Yb(β-dik)3∙2H2O< [Yb(β-dik)3]n<
Yb(β-dik)3∙Phen < [Yb(β-dik)3∙Phen]n, β-dik:
mphpd<mbphpd<dmhpd<dmod.
According to the obtained data for the
studied Yb(III) complexes with unsaturated
β-diketones, the following excitation and ener
gy transfer scheme can be proposed (Fig. 8)
Fig. 7 – Diagram of the change of integral intensity of luminescence inYb(III) β-diketonates depending on
the nature of the substituents in the ligands molecules.
According to the obtained data for the studied Yb(III) complexes with unsaturated β-
diketones, the following excitation and energy transfer scheme can be proposed (Fig. 8)
Fig. 8 – Scheme of energy transfer from an organic ligand to the Yb(III) (GSA – ground state
absorption).
As calculated above, there is a significant energy gap between the triplet state of the ligand
and the excited state of the ytterbium (III) ion. In addition, for Yb3+ ions, the 2F5/2 fluorescence level
lies∼10,000 cm−1 above the 2F7/2 ground state, which in this case allows us to speak about vibronic
interaction or theme chan is mof internal electrontransfer from the ligand to the metal [33]. We
propose that the energy transfer from the ligand triplet state to the excited level of Yb³⁺, facilitated
by vibronic coupling, accounts for the population of the Yb³⁺ excited state, which can then relax
radiatively to the ground state by emitting photons at approximately 980 nm. This indicates an
effective antenna effect, since the excitation energy photogenerated inorganic ligands is quickly
Fig. 8 – Scheme of energy transfer from an organic ligand to the Yb(III)
(GSA – ground state absorption).
As calculated above, there is a significant en-
ergy gap between the triplet state of the ligand
and the excited state of the ytterbium (III) ion.
In addition, for Yb3+ ions, the 2F5/2 fluorescence
level lies ∼10,000 cm−1 above the 2F7/2 ground
state, which in this case allows us to speak
about vibronic interaction or the mechanism
of internal electrontransfer from the ligand
to the metal [33]. We propose that the energy
transfer from the ligand triplet state to the ex-
cited level of Yb³⁺, facilitated by vibronic cou-
pling, accounts for the population of the Yb³⁺
excited state, which can then relax radiatively
to the ground state by emitting photons at ap-
proximately 980 nm. This indicates an effective
antenna effect, since the excitation energy pho-
togenerated inorganic ligands is quickly trans-
ferred to the Yb3+ nucleus. The type of β-dike-
tone mainly affects the intensity of absorption
and emission.
CONCLUSIONS. Monomeric, mixed-li-
gand and polymeric complexes of ytterbium
(III) with β-diketonate ligands with alkyl and
aryl substituents were synthesized and stud-
ied. It was established that the Yb(III) ion
forms triscomplexes with β-diketonate ligands
of the general formula Yb(β-dik)3∙2Н2О, the
coordination sphere in monoligand complex-
es is supplemented by 2 water molecules, the
coordination number of the lanthanide = 8,
84 ISSN 2708-129X. Укр. хім. журн., 2024
COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES
WITH UNSATURATED β-DIKETONES.INORGANIC CHEMISTRY
the coordination polyhedron is a square an
tiprism. Yb(III) β-diketonates easily attach a
donor ligand (phenanthroline), which displac-
es H2O molecules (OH-oscillators) due to the
formation of stronger bonds with the central
ion. Replacing water molecules with a phenan-
throline molecule does not affect the structure
of the coordination polyhedron, but causes
only its slight deformation, which is reflected
in the covalence parameters (increasing the
covalence of the bond). The polymerization
process also does not significantly affect the
structure of the elementary unit, there is only
a slight distortion of the coordination polyhe-
dron. The thermal stability of the synthesized
complexes increases from monoligand mono-
meric compounds to mixed-ligand polymers,
which can be explained by the formation of
compounds with a more rigid structure and a
system of branched chemical bonds.
The study of luminescent characteristics
showed that the integral intensity of lumi-
nescence varies in the series: dmod>dmh-
pd>mbphpd>mphpd and monomer-poly-
mer-MLC-MLC polymer. The best lumines-
cent characteristics are possessed by the ytter-
bium complex based on dmod. A significant
increase in the luminescent properties of the
synthesized complexes occurs when obtaining
mixed ligand complexes with phenanthroline,
which is primarily associated with solving the
problem of the quenching effect of water mol-
ecules. Also, a noticeable increase in Ilum occurs
when synthesizing MLC polymers. The prepa-
ration of such compounds is of practical im-
portance, since it is easy to obtain film materi-
als from polymer samples. Thus, the conduct-
ed studies of Yb(III) β-diketonate complexes
may hold promise for practical applications as
precursors of luminescent materials.
The work was financially supported
by the National Academy of Scien
ces of Ukraine within the framework
of the state budget topic 322E «Creation of
new hybrid, composite and polymeric mate-
rials doped with coordination compounds of
3d- and 4f-metals based on β-diketonate and
carboxylate acyclic ligands» (state registra-
tion number 0122U001299).
ПОРІВНЯЛЬНА ХАРАКТЕРИСТИКА СПЕКТ
РАЛЬНО-ЛЮМІНЕСЦЕНТНИХ ВЛАСТИВОСТЕЙ
КОМПЛЕКСІВ Yb(III) З НЕНАСИЧЕНИМИ
β-ДИКЕТОНАМИ
Н. Б. Іваха1,2*, О. С. Бережницька1,2
1Інститут загальної та неорганічної хімії
ім. В. І. Вернадського НАН України,
просп. Академіка Палладіна, 32/34, Київ
03142, Україна;
2Національний технічний університет
України «Київський політехнічний
інститут імені Ігоря Сікорського»,
просп. Берестейський, 37, Київ 03056,
Україна
e-mail: ivakhanadiia@gmail.com
У роботі проведено порівняльний аналіз
спектрально-люмінесцентних властивос-
тей синтезованих координаційних β-ди
кетонатних комплексів ітербію з такими лі-
гандами: 2,7-диметил-октен-1-діоном-3,5,
2,6-диметил-гептен-1-діоном-3,5, 2-метил-
5-фенілпентен-1-3,5-діоном, 2-метил-5-бі
фенілпентен-1-3,5-діоном. Крім цього про-
ведено дослідження полімерних сполук на
основі представлених комплексів та їхніх
85https://ucj.org.ua
N.B. Ivakha, O.S. Berezhnytska UCJ № 10 / Vol. 90
фенантролінових змішанолігандних похід-
них.
За допомогою низки фізико-хімічних
методів аналізу встановлено, що будова
елементарної ланки при полімеризації, а
також координаційна сфера комплексів
при утворенні змішанолігандних сполук не
зазнає суттєвих змін порівняно з вихідни-
ми молекулами β-дикетонатів. Термічний
аналіз показав значне підвищення темпера-
тури початку розкладання змішаноліганд-
них і металополімерних сполук відносно
їхніх мономерних аналогів. Методом люмі-
несцентної спектроскопії встановлено, що
досліджувані зразки проявляють люмінес-
ценцію в ІЧ-діапазоні.
Порівняльний аналіз інтегральних ін-
тенсивностей люмінесценції ітербієвих
комплексів дозволив виявити ключові фак-
тори впливу на емісійні характеристики.
Насамперед це одержання змішаноліганд-
них комплексів із фенантроліном, що доз-
воляє нівелювати негативний вплив одного
з найбільш відомих чинників гасійної дії:
ОН-осциляторів молекул води, яка допов-
нює координаційну сферу мономерних
ітербієвих комплексів. Крім цього позитив-
но позначається на Ilumсинтез полімерних
сполук на основі β-дикетонатних комплек-
сів, що може бути зумовлено зменшенням
впливу концентраційного гасіння, оскіль-
ки у полімерах випромінювальні центри
рівномірно розподілені по ланцюгу макро-
молекули.Такий підхід, окрім прямого по-
зитивного впливу на люмінесцентні вла-
стивості, має на меті вирішення питання
прикладного застосування синтезованих
сполук, оскільки полімери значно легше
піддаються переробленню та можуть утво-
рювати плівкові матеріали.
Загалом на основі проведених дослі-
джень можна сформувати такі залежно-
сті інтенсивності люмінесценції: dmod>
dmhpd>mbphpd>mphpd та мономер-полі-
мер-ЗЛК-ЗЛК-полімер. Як видно з цих да-
них, найкращими емісійними характерис-
тиками володіють ітербієві змішаноліганд-
ні моно- та полікомплекси з β-дикетонами з
алкільними замісниками.
Ключові слова: ітербій, комплекс, люмі-
несценція, β-дикетони, полімери.
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Стаття надійшла 27.05.2024.
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| resource_txt_mv | ucjorgua/67/058bd02af0b1196a7337511dee4f2b67.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-6922026-07-22T08:23:55Z COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES Ivakha , Nadiia Berezhnytska, Oleksandra ytterbium, complex, luminescence, β-diketones, polymers. The study presents a comparative analysis of the spectral-luminescent properties of synthesized β-diketonate coordination complexes of ytterbium with the following ligands: 2,7-dimethyl-oct-1-en-3,5-dione, 2,6-dimethyl-hept-1-en-3,5-dione, 2-methyl-5-phenylpent-1-en-3,5-dione, 2-methyl-5-biphenylpent-1-en-3,5-dione. In addition, research was conducted on polymeric compounds based on these complexes and their phenanthroline mixed-ligand derivatives. Using a range of physicochemical analysis methods, it was established that the structure of the elementary unit during polymerization, as well as the coordination sphere of the complexes during the formation of mixed-ligand compounds, does not undergo significant changes compared to the initial β-diketonate molecules. Thermal analysis revealed a significant increase in the decomposition onset temperature of mixed-ligand and metallopolymeric compounds compared to their monomeric counterparts. Luminescence spectroscopy demonstrated that the studied samples exhibit luminescence in the infrared (IR) range. A comparative analysis of the integral luminescence intensities of ytterbium complexes identified key factors influencing the emission characteristics. Primarily, the synthesis of mixed-ligand complexes with phenanthroline mitigates the negative effects of one of the most well-known quenching factors: OH-oscillators of water molecules, which complement the coordination sphere of monomeric ytterbium complexes. Furthermore, the synthesis of polymeric compounds based on β-diketonate complexes positively affects the luminescence, potentially due to a reduction in concentration quenching, as in polymers, the emitting centers are uniformly distributed along the macromolecular chain. Besides directly enhancing luminescent properties, this approach aims to address the practical application of the synthesized compounds since polymers are significantly easier to process and can form film materials. Based on the conducted research, the following luminescence intensity dependencies were established: dmod&gt;dmhpd&gt;mbphpd&gt;mphpd, as well as monomer-polymer-MLC-MLC polymer. As seen from the presented data, the best emission characteristics are exhibited by ytterbium mixed-ligand mono- and polycomplexes with β-diketones containing alkyl substituents. V.I.Vernadsky Institute of General and Inorganic Chemistry 2024-11-29 Article Article Inorganic Chemistry Неорганическая химия Неорганічна хімія application/pdf https://ucj.org.ua/index.php/journal/article/view/692 10.33609/2708-129X.90.10.2024.69-87 Ukrainian Chemistry Journal; Vol. 90 No. 10 (2024): Ukrainian Chemistry Journal; 69-87 Украинский химический журнал; ##issue.vol## 90 ##issue.no## 10 (2024): Ukrainian Chemistry Journal; 69-87 Український хімічний журнал; Том 90 № 10 (2024): Ukrainian Chemistry Journal; 69-87 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/692/345 Copyright (c) 2024 Nadiia Ivakha , Oleksandra Berezhnytska https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Ivakha , Nadiia Berezhnytska, Oleksandra COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES |
| title | COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES |
| title_full | COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES |
| title_fullStr | COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES |
| title_full_unstemmed | COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES |
| title_short | COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES |
| title_sort | comparative characteristics of spectral-luminescence properties of yb(iii) complexes with unsaturated β-diketones |
| topic_facet | ytterbium complex luminescence β-diketones polymers. |
| url | https://ucj.org.ua/index.php/journal/article/view/692 |
| work_keys_str_mv | AT ivakhanadiia comparativecharacteristicsofspectralluminescencepropertiesofybiiicomplexeswithunsaturatedbdiketones AT berezhnytskaoleksandra comparativecharacteristicsofspectralluminescencepropertiesofybiiicomplexeswithunsaturatedbdiketones |