SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS
Complexation in M (II) – Rut systems (M(II) = Co, Cu) was studied by electron absorption spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal: ligand ratio (1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoichiometric composition of the c...
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Ukrainian Chemistry Journal| _version_ | 1871465759921668096 |
|---|---|
| author | Trunova , Elena Artamonov, Michailo Makotryk , Tamara |
| author_facet | Trunova , Elena Artamonov, Michailo Makotryk , Tamara |
| author_institution_txt_mv | [
{
"author": "Elena Trunova ",
"institution": "V. I. Vernadskii Institute of General and Inorganic Chemistry of the Ukrainian National Academy of Sciences, Akad. Palladin Avenue 32\/34, Kyiv 03142, Ukraine"
},
{
"author": "Michailo Artamonov",
"institution": "V. I. Vernadskii Institute of General and Inorganic Chemistry of the Ukrainian National Academy of Sciences, Akad. Palladin Avenue 32\/34, Kyiv 03142, Ukraine"
},
{
"author": "Tamara Makotryk ",
"institution": "V. I. Vernadskii Institute of General and Inorganic Chemistry of the Ukrainian National Academy of Sciences, Akad. Palladin Avenue 32\/34, Kyiv 03142, Ukraine"
}
] |
| author_sort | Trunova , Elena |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:47Z |
| description | Complexation in M (II) – Rut systems (M(II) = Co, Cu) was studied by electron absorption spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal: ligand ratio (1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoichiometric composition of the complexation reaction products are influenced by such basic parameters as L:M and the pH value of the medium. Depending on the pH value,  chelation involves certain binding sites, which primarily is associated with the redistribution of the electron density in the flavonoid molecule. In a weakly acidic or neutral medium, regardless of the M(II): Rut ratio, the formation of monoligand complexes of rutin with 3-d metals occurs with the participation of 5-OH and 4-C=O fragments of the A and C rings, and in an alkaline medium, chelation proceeds on the catecholic fragment of  ring B rutin. Biligand complexes are formed with the participation of the gydroxo groups of the catechol fragment of each rutin molecule, and the formation of compounds with a ratio of 2:1 occurs both due to 5-OH and 4C=O and due to 3 ', 4'-OH groups. The calculated values of the stability constants of the complexes showed that the stability of the Co (II) complexes is several orders of magnitude lower than the stability of the corresponding Cu (II) complexes. |
| doi_str_mv | 10.33609/2708-129X.87.10.2021.90-102 |
| first_indexed | 2025-09-24T17:43:41Z |
| format | Article |
| fulltext |
90 ISSN 2708-129X. Укр. хім. журн., 2020
UDC 541.49: 546.562+546.73: 577.164.32 – 54-386 doi: 10.33609/2708-129X.87.10.2021.90-102
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES
WITH RUTIN IN SOLUTIONS
O.K. Тrunova*, М.S. Аrtamonov, T.O. Makotryk
V.I. Vernadsky Institute of General and Inorganic Chemistry of the National Academy of Sciences
of Ukraine, 32/34 Academic Palladin ave., Kyiv 03142, Ukraine
* e-mail: trelkon@gmail.com
Complexation in M (II) – Rut systems (M(II) = Co, Cu) was studied by electron absorption
spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal:
ligand ratio (1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoi-
chiometric composition of the complexation reaction products are influenced by such basic
parameters as L:M and the pH value of the medium. Depending on the pH value, chelation
involves certain binding sites, which primarily is associated with the redistribution of the
electron density in the flavonoid molecule. In a weakly acidic or neutral medium, regardless
of the M(II): Rut ratio, the formation of monoligand complexes of rutin with 3-d metals oc-
curs with the participation of 5-OH and 4-C=O fragments of the A and C rings, and in an
alkaline medium, chelation proceeds on the catecholic fragment of ring B rutin. Biligand
complexes are formed with the participation of the gydroxo groups of the catechol fragment
of each rutin molecule, and the formation of compounds with a ratio of 2:1 occurs both due
to 5-OH and 4C=O and due to 3 ', 4'-OH groups. The calculated values of the stability con-
stants of the complexes showed that the stability of the Co (II) complexes is several orders of
magnitude lower than the stability of the corresponding Cu (II) complexes.
Keywords: complexes, copper, cobalt, rutin, flavonoids, absorption spectra.
INTRODUCTION. Flavonoids are a large
class of natural low-molecular-weight poly
phenolic compounds of the general С6–С3–С6
carbon skeleton formula, as well as their de-
rivatives, which are characterized by high bio
logical activity and low toxicity. The targeted
biological action of flavonoids is related to the
physicochemical properties of various struc-
tures, including conformations of molecules,
the presence of which provides, for example,
radioprotective and antioxidant properties.
Flavonoids are widely used in plants, in which
they play several very important functions, in-
cluding antioxidant one [1–5]. Rutin (3, 3 ', 4',
5,7-pentahydroxyflavone-3-rhamnoglucoside
C27H26O16H4, H4L, Rut) is a natural flavonoid
of the flavonol type, consisting of the flavo-
nol quercetin and the rutinose disaccharide
(rhamnose and glucose):
O.K. Тrunova, М.S. Аrtamonov, T.O. Makotryk
91https://ucj.org.ua
UCJ № 10 / Vol. 87
It exhibits high biological and pharmaco-
logical activity (antioxidant, anti-inflammato-
ry, antiviral, antimicrobial, etc.) [6–12]. Due
to its medicinal properties, rutin is widely
used as a component of many pharmaceuticals
(eg, vitamin P). The most important structu
ral elements of rutin, which determine its pro
perties, are: o-dihydroxo group in the B-cycle
(catechol structure) as a potential radical label;
the double bond between positions 2 and 3 of
the C-cycle is conjugated with the keto group
at position 4 (due to the ability to delocalize
the unpaired electron of the flavonoid radical)
and C-3, C-5 and C-7 hydroxyl groups (C and
A cycles) as potential acceptors of free radicals
[13,14].
Flavonoids bind metal ions well, forming
chelate complexes, which is of great impor-
tance for the analytical and pharmaceutical
use of these compounds. The formation of
different CS structures of flavonoids with me
tal ions with the stoichiometric composition
L: M from 1: 2 to 2: 1 depends on the binding
sites that participate in the reaction. As can be
seen from the structure of the rutin molecule,
in complexes with metals, this flavonoid has
two potential centers for coordination to me
tal ions: 5-OH and 4-C = O, 3'-OH and 4'-OH
(Fig. 1). Most metal ions are able to form com-
plexes with rutin in a wide range of pH (2-10),
the stereochemistry of which strongly depends
on the acidity of the solutions [15-17]. The
best complexation occurs at pH 4-8, because at
pH<4 rutin is in undissociated form (weak
acid), and at pH>8 there is the formation of
stoichiometrically different coordination com-
pounds or dissociation of existing complexes.
In aqueous solutions, the complexes are poorly
soluble, so, as a rule, they are investigated in
the form of solid compounds.
Considerable attention in the study of flavo-
noids is paid to complexes with transition me
tals, which can be used for the prevention and
treatment of many diseases [15, 18,19]. Studies
of flavonoids in oxidative processes show that
the formation of chelates gives them antioxi-
dant properties, which are more effective in
binding free radicals [20–22]. In [20] it was
shown that rutin complexes with iron, copper
and zinc show increased efficiency in the ab-
sorption of free radicals, the most effective of
which is the copper complex. The rutin com-
UDC 541.49: 546.562+546.73: 577.164.32 – 54-386 doi:
O.K. Тrunova*, М.S. Аrtamonov, T.O. Makotryk
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN
SOLUTIONS
V.I. Vernadsky Institute of General and Inorganic Chemistry of the National Academy of Sciences
of Ukraine, 32/34 Academic Palladin ave., Kyiv, 03142, Ukraine
* e-mail: trelkon@gmail.com
Complexation in M (II) - Rut systems (M(II) = Co, Cu) was studied by electron absorption
spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal: ligand ratio
(1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoichiometric
composition of the complexation reaction products are influenced by such basic parameters as L:M
and the pH value of the medium. Depending on the pH value, chelation involves certain binding
sites, which primarily is associated with the redistribution of the electron density in the flavonoid
molecule. In a weakly acidic or neutral medium, regardless of the M(II): Rut ratio, the formation of
monoligand complexes of rutin with 3-d metals occurs with the participation of 5-OH and 4-C=O
fragments of the A and C rings, and in an alkaline medium, chelation proceeds on the catecholic
fragment of ring B rutin. Biligand complexes are formed with the participation of the gydroxo
groups of the catechol fragment of each rutin molecule, and the formation of compounds with a
ratio of 2:1 occurs both due to 5-OH and 4C=O and due to 3 ', 4'-OH groups. The calculated values
of the stability constants of the complexes showed that the stability of the Co (II) complexes is
several orders of magnitude lower than the stability of the corresponding Cu (II) complexes.
Keywords: complexes, copper, cobalt, rutin, flavonoids, absorption spectra.
INTRODUCTION. Flavonoids are a large class of natural low-molecular-weight
polyphenolic compounds of the general С6–С3–С6 carbon skeleton formula, as well as their
derivatives, which are characterized by high biological activity and low toxicity. The targeted
biological action of flavonoids is related to the physicochemical properties of various structures,
including conformations of molecules, the presence of which provides, for example, radioprotective
and antioxidant properties. Flavonoids are widely used in plants, in which they play several very
important functions, including antioxidant one [1–5]. Rutin (3, 3 ', 4', 5,7-pentahydroxyflavone-3-
rhamnoglucoside C27H26O16H4, H4L, Rut) is a natural flavonoid of the flavonol type, consisting of
the flavonol quercetin and the rutinose disaccharide (rhamnose and glucose):
Fig.1 The structure of the rutin molecule
It exhibits high biological and pharmacological activity (antioxidant, anti-inflammatory,
antiviral, antimicrobial, etc.) [6–12]. Due to its medicinal properties, rutin is widely used as a
component of many pharmaceuticals (eg, vitamin P). The most important structural elements of
Fig. 1. The structure of the rutin molecule.
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS
92 ISSN 2708-129X. Укр. хім. журн., 2021
INORGANIC CHEMISTRY
plex with copper has a greater ability to retard
the oxidation process, and rutin complexes
with iron(II) and copper(II) are more effective
in removing free radicals compared to pure ru-
tin [23, 24].
It should be noted that rutin and its com-
plexes due to poor solubility in water and body
fluids have a very low bioavailability in the body,
which limits the use of their useful pharmaco-
logical properties. Increased solubility can be
achieved by using other solvents that will also
be non-toxic to living organisms. The literature
mainly investigates the complexation of rutin
with metals in methanol solutions, DMSO or
mixtures of different organic solvents [23, 25–
28]. Since rutin is poorly soluble in water, but
better soluble in ethanol (0.66∙10-5 mol/dm3
and 436.5∙10-5 mol/dm3, respectively) [1, 29,
30], for the potential application of its useful
properties in pharmacology, there is a need to
investigate the properties of rutin and its com-
plexes with Cu (II) and Co (II) in aqueous-
ethanolic solutions. The choice of metal ions is
due to their role in the life of organisms. Cop-
per and cobalt are transition metals and es-
sential trace elements. Cu (II) is part of many
vitamins, hormones, enzymes, respiratory pig-
ments, is involved in metabolic processes, tis-
sue respiration and more. Copper ions play an
important role of cofactors in living systems, so
the presence of competing complexing agents
can affect their biological activity [20,31], Co
(II) is present in vitamin B12, is involved in
enzymatic processes and hormone synthesis
[31]. Therefore, the aim of this work is to study
the acid-base forms of rutin depending on the
pH of the solution and its complexation with
Cu(II) and Co(II) in aqueous-ethanol solu-
tions by pH-metric titration and electron ab-
sorption spectroscopy.
EXPERIMENT AND DISCUSSION OF
THE RESULTS. The study of the complexa-
tion of Cu(II) and Co(II) ions with rutin was
carried out in water-ethanol solutions (1: 2)
depending on pH (~ 2÷11) and the metal:li-
gand ratio. Inorganic salts of 3-d metals were
used as starting compounds: cobalt chloride
СоCl2⋅6H2O (analytical grade) and copper
sulfate СuSO4∙5H2O (analytical grade). Rutin
manufactured by Sigma- Aldrich was used
without further purification.
The exact concentration of metal ions was
determined by complexometric titration [32].
Working solutions of rutin were prepared
using a precisely weighed sample. Potentio-
metric titration was carried out with a 0,1 M
solution of alkali (NaOH) or acid (HCl) as a
titrant. The pH value was recorded on a Met-
tler Toledo Seven Easy pH meter (accuracy
± 0.05)at 20 ± 3 °C and constant ionic strength
μ = 0,1 M (KNO3). Electronic absorption spectra
were recorded on a UV/VIS Specord 210 Plus
spectrophotometer (Analytik Jena AG) in
quartz cuvettes with l=1 cm (measurement
range 190-1100 nm; relative error in the measu
rement of optical density ±0,005). A series of
Co(II) and Cu(II) solutions with rutin was stud-
ied at a concentration of 1·10-4 М and the ratio
M:Rut = 1:1, 2:1. The comparison solution is
water. To establish the stoichiometric compo-
sition and stability of the formed complexes,
the method of equilibrium displacement was
used [33]. Step constants of complex formation
were determined by the titration of a solution
containing known amounts of C (II) chloride
C (II) sulfate and rutin with an acid/alkali
solution.
In the electronic absorption spectrum of an
aqueous ethanolic solution of rutin (Fig. 2)
there are two absorption bands, which are
O.K. Тrunova, М.S. Аrtamonov, T.O. Makotryk
93https://ucj.org.ua
UCJ № 10 / Vol. 87
due to intramolecular π → π * transitions:
the first band with a maximum in the area of
327–408 nm corresponds to the absorption of
a cynnamoyl fragment of the molecule asso
ciated with a conjugated system between cy-
cle B and a carbonyl fragment of cycle C. The
second absorption band in the region of 250–
290 nm refers to π → π* transitions in the A
ring benzoyl fragment [34]
Fig. 2. UV absorption spectrum of an aqueous-ethanol solution of rutin at pH: 1. – 5.6; 2. – 6.3;
3. – 7.0; 4. – 8.2; 5. – 9.7; 6. – 10.4; 7. – 11.4.
3
ratio M:Rut = 1:1, 2:1. The comparison solution is water. To establish the stoichiometric
composition and stability of the formed complexes, the method of equilibrium displacement was
used [33]. Step constants of complex formation were determined by the titration of a solution
containing known amounts of C (II) chloride C (II) sulfate and rutin with an acid/alkali solution.
In the electronic absorption spectrum of an aqueous ethanolic solution of rutin (Fig. 2) there
are two absorption bands, which are due to intramolecular π → π * transitions: the first band with a
maximum in the area of 327–408 nm corresponds to the absorption of a cynnamoyl fragment of the
molecule associated with a conjugated system between cycle B and a carbonyl fragment of cycle
C. The second absorption band in the region of 250-290 nm refers to π → π* transitions in the A
ring benzoyl fragment [34]
250 300 350 400 450 500
0
1
2
3
1
1
7
6
5
4
32
,nm
A
bs
or
ba
nc
e
рН
I
II
Fig. 2. UV absorption spectrum of an aqueous-ethanol solution of rutin at pH: 1. – 5.6; 2. – 6.3; 3. –
7.0; 4. – 8.2; 5. – 9.7; 6. – 10.4; 7. – 11.4.
The gradual bathochromic shift at pH>6 is associated with the formation of differently
protonated forms of rutin, which are in dynamic equilibrium depending on the acidity of the
solutions. In the acidic pH range, there is a bathochromic shift of absorption band II with the
formation of a shoulder at 290 nm, which disappears at pH~7. At the same time, there is a
bathochromic shift of the band I maximum (357 nm→363 nm), which is accompanied by a
hypochromic effect. Such changes may be related to the dissociation of the OH group at position 7
of cycle A of the rutin molecule. At pH = 7.74 there are a hypsochromic shift and an increase in the
optical density of the solution, which indicates the further dissociation of proton rutin. At pH =
9.65, the optical properties of the system change significantly – two absorption maxima are clearly
manifested at λmax = 329 nm and 407 nm. At pH = 11.90, a hypsochromic shift of these absorption
maxima is observed, which may be associated with partial oxidation of rutin.
According to spectrophotometric titration, the dissociation constants of rutin and the distribution of
acid-base forms of rutin depending on the pH of the solution were calculated using the
mathematical program CLINP 2.1 [35] (tab. 1, fig. 3, respectively).
Table 1
Values of rutin dissociation constants in an aqueous ethanol solution.
Dissociation stage рК Dissociating group
H4L ↔ H3L- + H+ 8,17 ± 0,15 7-ОН
H3L- ↔ H2L2- + H+ 9,63 ± 0,16 3’-ОН
H2L2- ↔ HL3- + H+ 10,76 ± 0,14 5-ОН
HL3- ↔ L4- + H+ 11,85 ± 0,26 4’-ОН
The gradual bathochromic shift at pH>6
is associated with the formation of different-
ly protonated forms of rutin, which are in
dynamic equilibrium depending on the aci
dity of the solutions. In the acidic pH range,
there is a bathochromic shift of absorption
band II with the formation of a shoulder at
290 nm, which disappears at pH~7. At the
same time, there is a bathochromic shift of the
band I maximum (357 nm→363 nm), which
is accompanied by a hypochromic effect. Such
changes may be related to the dissociation of
the OH group at position 7 of cycle A of the
rutin molecule. At pH = 7.74 there are a hyp-
sochromic shift and an increase in the opti-
cal density of the solution, which indicates
the further dissociation of proton rutin. At
pH = 9.65, the optical properties of the system
change significantly – two absorption maxi-
ma are clearly manifested at λmax = 329 nm
and 407 nm. At pH = 11.90, a hypsochromic
shift of these absorption maxima is observed,
which may be associated with partial oxida-
tion of rutin.
According to spectrophotometric titration,
the dissociation constants of rutin and the dis-
tribution of acid-base forms of rutin depend-
ing on the pH of the solution were calculated
using the mathematical program CLINP 2.1
[35] (tab. 1, fig. 3, respectively).
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS
94 ISSN 2708-129X. Укр. хім. журн., 2021
INORGANIC CHEMISTRY
Table 1
Values of rutin dissociation constants in
an aqueous ethanol solution.
Dissociation
stage рК Dissociating
group
H4L ↔ H3L
- + H+ 8,17 ± 0,15 7-ОН
H3L
- ↔ H2L
2- + H+ 9,63 ± 0,16 3’-ОН
H2L
2- ↔ HL3- + H+ 10,76 ± 0,14 5-ОН
HL3- ↔ L4- + H+ 11,85 ± 0,26 4’-ОН
It should be noted that the calculated disso-
ciation constants of the OH groups of rutin dif-
fer slightly from the pK values given in [36,37]
due to the use of different solvents (methanol
or water)
Thus, the analysis of electronic absorption
spectra shows that the dissociation of the hy-
droxyl groups of rutin in aqueous-ethano
lic solutions takes place in the order: 7-OH,
3´-OH, 5-OH, 4´-OH.
Fig.3 Dissociation diagram of rutin: H4L undissociated form of rutin (1); H3L
- (2); H2L
2- (3); HL3- (4),
L4-
(5).
4
It should be noted that the calculated dissociation constants of the OH groups of rutin differ slightly
from the pK values given in [36,37] due to the use of different solvents (methanol or water)
2 4 6 8 10 12
0
20
40
60
80
100
5
4
3
1
%
pH
2
Fig.3 Dissociation diagram of rutin: H4L undissociated form of rutin (1); H3L- (2); H2L2- (3); HL3-
(4), L4- (5).
Thus, the analysis of electronic absorption spectra shows that the dissociation of the hydroxyl
groups of rutin in aqueous-ethanolic solutions takes place in the order: 7-OH, 3´-OH, 5-OH, 4´-OH.
The study of complex formation processes of rutin with Co (II) and Cu (II) ions was
performed by pH-potentiometric titration. Figure 4 shows titration curves of the Co(II):Rut (a) and
Cu(II):Rut (b) systems, which are in a more acidic pH range relative to the critical titration of rutin,
which is associated with the formation of metal complexes with functional groups Rut (carbonyl
СO or ОН). The titration curves of cobalt and copper systems at M: Rut = 1: 1 (Fig. 4, curves 2)
have almost the same appearance: two poorly defined buffer regions (pH ~ 6-8 and 8-10) and a
blurred jump at pH ~ 10. It is likely that tapered complexes are formed in a more acidic medium in
which the metals are bonded to the 5-hydroxyl and 4-carbonyl groups of rings A and C. In an
alkaline medium, the metals are bonded to the deprotonated hydroxyls of the catechol moiety. The
titration curve of the system Cu(II):Rut = 2:1 (Fig. 4, curve 3) has two distinct jumps (pH 5.5 and
9), shifted to a more acidic pH region compared to the equimolar system. Under these conditions,
the interaction of a copper ion with the 3´-4´-hydroxyl groups of the ring B of two rutin molecules
is possible similar to the interaction of Cu (II) with quercetin [38].
а b
The study of complex formation processes
of rutin with Co (II) and Cu (II) ions was per-
formed by pH-potentiometric titration. Figu
re 4 shows titration curves of the Co(II):Rut
(a) and Cu(II):Rut (b) systems, which are in
a more acidic pH range relative to the critical
titration of rutin, which is associated with the
formation of metal complexes with functio
nal groups Rut (carbonyl –СO= or –ОН). The
titration curves of cobalt and copper systems
at M: Rut = 1: 1 (Fig. 4, curves 2) have almost
the same appearance: two poorly defined buff-
er regions (pH ~ 6-8 and 8-10) and a blurred
jump at pH ~ 10. It is likely that tapered com-
plexes are formed in a more acidic medium in
which the metals are bonded to the 5-hydro
xyl and 4-carbonyl groups of rings A and C.
In an alkaline medium, the metals are bond-
ed to the deprotonated hydroxyls of the cate
chol moiety. The titration curve of the system
O.K. Тrunova, М.S. Аrtamonov, T.O. Makotryk
95https://ucj.org.ua
UCJ № 10 / Vol. 87
Cu(II):Rut = 2:1 (Fig. 4, curve 3) has two dis-
tinct jumps (pH 5.5 and 9), shifted to a more
acidic pH region compared to the equimolar
system. Under these conditions, the interac-
tion of a copper ion with the 3´-4´-hydroxyl
groups of the ring B of two rutin molecules is
possible similar to the interaction of Cu (II)
with quercetin [38].
Fig. 4. Curves of pH-metric titration of the systems Co(II):Rut (a) and Cu (II):Rut (b): 1. – Rut; 2. –
M:Rut = 1:1; 3. – M:Rut = 2: 1. 4
It should be noted that the calculated dissociation constants of the OH groups of rutin differ slightly
from the pK values given in [36,37] due to the use of different solvents (methanol or water)
2 4 6 8 10 12
0
20
40
60
80
100
5
4
3
1
%
pH
2
Fig.3 Dissociation diagram of rutin: H4L undissociated form of rutin (1); H3L- (2); H2L2- (3); HL3-
(4), L4- (5).
Thus, the analysis of electronic absorption spectra shows that the dissociation of the hydroxyl
groups of rutin in aqueous-ethanolic solutions takes place in the order: 7-OH, 3´-OH, 5-OH, 4´-OH.
The study of complex formation processes of rutin with Co (II) and Cu (II) ions was
performed by pH-potentiometric titration. Figure 4 shows titration curves of the Co(II):Rut (a) and
Cu(II):Rut (b) systems, which are in a more acidic pH range relative to the critical titration of rutin,
which is associated with the formation of metal complexes with functional groups Rut (carbonyl
СO or ОН). The titration curves of cobalt and copper systems at M: Rut = 1: 1 (Fig. 4, curves 2)
have almost the same appearance: two poorly defined buffer regions (pH ~ 6-8 and 8-10) and a
blurred jump at pH ~ 10. It is likely that tapered complexes are formed in a more acidic medium in
which the metals are bonded to the 5-hydroxyl and 4-carbonyl groups of rings A and C. In an
alkaline medium, the metals are bonded to the deprotonated hydroxyls of the catechol moiety. The
titration curve of the system Cu(II):Rut = 2:1 (Fig. 4, curve 3) has two distinct jumps (pH 5.5 and
9), shifted to a more acidic pH region compared to the equimolar system. Under these conditions,
the interaction of a copper ion with the 3´-4´-hydroxyl groups of the ring B of two rutin molecules
is possible similar to the interaction of Cu (II) with quercetin [38].
а b
4
It should be noted that the calculated dissociation constants of the OH groups of rutin differ slightly
from the pK values given in [36,37] due to the use of different solvents (methanol or water)
2 4 6 8 10 12
0
20
40
60
80
100
5
4
3
1
%
pH
2
Fig.3 Dissociation diagram of rutin: H4L undissociated form of rutin (1); H3L- (2); H2L2- (3); HL3-
(4), L4- (5).
Thus, the analysis of electronic absorption spectra shows that the dissociation of the hydroxyl
groups of rutin in aqueous-ethanolic solutions takes place in the order: 7-OH, 3´-OH, 5-OH, 4´-OH.
The study of complex formation processes of rutin with Co (II) and Cu (II) ions was
performed by pH-potentiometric titration. Figure 4 shows titration curves of the Co(II):Rut (a) and
Cu(II):Rut (b) systems, which are in a more acidic pH range relative to the critical titration of rutin,
which is associated with the formation of metal complexes with functional groups Rut (carbonyl
СO or ОН). The titration curves of cobalt and copper systems at M: Rut = 1: 1 (Fig. 4, curves 2)
have almost the same appearance: two poorly defined buffer regions (pH ~ 6-8 and 8-10) and a
blurred jump at pH ~ 10. It is likely that tapered complexes are formed in a more acidic medium in
which the metals are bonded to the 5-hydroxyl and 4-carbonyl groups of rings A and C. In an
alkaline medium, the metals are bonded to the deprotonated hydroxyls of the catechol moiety. The
titration curve of the system Cu(II):Rut = 2:1 (Fig. 4, curve 3) has two distinct jumps (pH 5.5 and
9), shifted to a more acidic pH region compared to the equimolar system. Under these conditions,
the interaction of a copper ion with the 3´-4´-hydroxyl groups of the ring B of two rutin molecules
is possible similar to the interaction of Cu (II) with quercetin [38].
а b
Based on the obtained titration curves, the
concentration of the free ligand [L–] and the
formation function were calculated using the
formulas:
–lg[L–] = pka – paH+ – lg(CL – CT – aH+),
ñ = (CT + aH+ – [L–]) / CМ,
(1)
(2)
where CL – the total ligand concentration, CМ –
the total metal concentration, CT – the con-
centration of added titrant, aH+ – the activity of
hydrogen ions, ka – the acid dissociation con-
stant of rutin.
Based on the values of ñ according to the
Bjerrum method [39] stepwise stability con-
stants of complexes of cobalt and copper with
rutin are calculated (Table 2).
The stability of Co(II) complexes is several
orders of magnitude lower than the stability of
copper complexes, which is obviously due to
the high affinity of Cu2+ for rutin donor oxygen
atoms, and especially for the ortho-dihydroxyl
group [34].
Table 2
The calculated values of the stability con-
stants of complexes of Co (II) and Cu (II)
with rutin*.
Metals M: Rut lgβ
Co2+
1:1 8,85±0,05
2:1 8,16±0,07
Cu2+
1:1 18,51±0,08
2: 1 11,76±0,05
*lgβ is given for the form of complexes [ML] and [M2L]
The complexation of rutin with Co(II) and
Cu(II) ions was analyzed using electronic ab-
sorption spectra in the ultraviolet and visible
regions depending on pH (fig. 5, a, b)
In the spectra of all studied systems with
a change in pH and the ratio of components,
there are a change in the optical density of
solutions and a bathochromic shift of the ab-
sorption maxima of bands I and II in complex-
es relative to their position in the spectra of
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS
96 ISSN 2708-129X. Укр. хім. журн., 2021
INORGANIC CHEMISTRY
pure rutin. This indicates complexation in M:
Rut systems. It should be noted that in acidic
media (pH <4) rutin is in the protonated form
H4L, the participation of which in complexa-
tion is not possible. At pH≥6, rutin turns into
an electron-donating form, which further dis-
sociates with the formation of a flavonolate ion
and can interact with the metal-complexing
agent. The largest bathochromic shift λmax
for all studied systems occurs at pH≥5.5 due
to the involvement in chelation of different
binding sites.
Fig. 5 UV spectra of systems as a function of pH: a – Co: Rut=1:1 (2.56 (1); 4.16 (2); 6.5 (3); 7.52 (4);
8.44 (5); 9.79 (6); 10.48 (7)); b – Cu:Rut=2:1 (2.6 (1); 3.67 (2); 4.62 (3); 5.55 (4); 6.38 (5); 7.95 (6); 9.47 (7);
10.0 (8)). Insertion: UV spectra of systems in the range of 700–900 nm.
5
Fig.4. Curves of pH-metric titration of the systems Co(II):Rut (a) and Cu (II):Rut (b): 1-Rut; 2-
M:Rut = 1:1; 3- M:Rut = 2: 1.
Based on the obtained titration curves, the concentration of the free ligand [L–] and the
formation function were calculated using the formulas:
–lg[L–] = pka – paH+ – lg(CL – CT – aH+),
ñ = (CT + aH+ – [L–]) / CМ,
(1)
(2)
where CL – the total ligand concentration, CМ – the total metal concentration, CT – the
concentration of added titrant, aH+ – the activity of hydrogen ions, ka – the acid dissociation
constant of rutin.
Based on the values of ñ according to the Bjerrum method [39] stepwise stability constants
of complexes of cobalt and copper with rutin are calculated (Table 2).
Table 2
The calculated values of the stability constants of complexes of Co (II) and Cu (II) with
rutin*.
Metals M: Rut lgβ
Co2+ 1:1 8,85±0,05
2:1 8,16±0,07
Cu2+ 1:1 18,51±0,08
2: 1 11,76±0,05
*lgβ is given for the form of complexes [ML] and [M2L]
The stability of Co(II) complexes is several orders of magnitude lower than the stability of copper
complexes, which is obviously due to the high affinity of Cu2+ for rutin donor oxygen atoms, and
especially for the ortho-dihydroxyl group [34].
The complexation of rutin with Co(II) and Cu(II) ions was analyzed using electronic
absorption spectra in the ultraviolet and visible regions depending on pH (fig. 5, a, b)
200 300 400 500 600
0.0
0.5
1.0
1.5
2.0
2.5
3.0
,nm
A
bs
or
ba
nc
e
4
6
5
731
2
a
6
200 300 400 500 600
0.0
0.5
1.0
1.5
2.0
2.5
,nm
A
bs
or
ba
nc
e
4
5
8
6
7
3
2
1 b
Fig. 5 UV spectra of systems as a function of pH: a – Co: Rut=1:1 (2.56 (1); 4.16 (2); 6.5 (3); 7.52
(4); 8.44 (5); 9.79 (6); 10.48 (7)); b – Cu:Rut=2:1 (2.6 (1); 3.67 (2); 4.62 (3); 5.55 (4); 6.38 (5); 7.95
(6); 9.47 (7); 10.0 (8)). Insertion: UV spectra of systems in the range of 700–900 nm.
In the spectra of all studied systems with a change in pH and the ratio of components, there
are a change in the optical density of solutions and a bathochromic shift of the absorption maxima
of bands I and II in complexes relative to their position in the spectra of pure rutin. This indicates
complexation in M: Rut systems. It should be noted that in acidic media (pH <4) rutin is in the
protonated form H4L, the participation of which in complexation is not possible. At pH≥6, rutin
turns into an electron-donating form, which further dissociates with the formation of a flavonolate
ion and can interact with the metal-complexing agent. The largest bathochromic shift λmax for all
studied systems occurs at pH≥5.5 due to the involvement in chelation of different binding sites.
Regardless of the metal, for all systems, the maximum of band I shifts toward long
wavelengths compared to the solution of pure rutin (Fig. 6).
200 300 400 500
0
2
4
Rut
=360 nm =257 nm
Co-Rut
=368 nm =268 nm =204 nm
Cu-Rut
=409 nm=267 nm=209 nm IV=413 nm
,nm
A
bs
or
ba
nc
e
IV
Fig.6 UV spectra of rutin and complexes CoRut, CuRut.
For a Cu-containing system, band I is strongly shifted to the visible region by 53 nm (λmax. = 413
nm, band IV). Under similar conditions, band II of rutin in the presence of metal ions has a
bathochromic shift of ~ 10 nm, but in the spectra of metal complexes appears band III at 204 (209)
nm, which may be due to different modes of coordination of cations to the functional groups of
rutin.
Figure 7 shows a comparison of electronic absorption spectra for systems with different M: Rut
ratios.
O.K. Тrunova, М.S. Аrtamonov, T.O. Makotryk
97https://ucj.org.ua
UCJ № 10 / Vol. 87
Fig.6 UV spectra of rutin and complexes CoRut, CuRut.
6
200 300 400 500 600
0.0
0.5
1.0
1.5
2.0
2.5
,nm
A
bs
or
ba
nc
e
4
5
8
6
7
3
2
1 b
Fig. 5 UV spectra of systems as a function of pH: a – Co: Rut=1:1 (2.56 (1); 4.16 (2); 6.5 (3); 7.52
(4); 8.44 (5); 9.79 (6); 10.48 (7)); b – Cu:Rut=2:1 (2.6 (1); 3.67 (2); 4.62 (3); 5.55 (4); 6.38 (5); 7.95
(6); 9.47 (7); 10.0 (8)). Insertion: UV spectra of systems in the range of 700–900 nm.
In the spectra of all studied systems with a change in pH and the ratio of components, there
are a change in the optical density of solutions and a bathochromic shift of the absorption maxima
of bands I and II in complexes relative to their position in the spectra of pure rutin. This indicates
complexation in M: Rut systems. It should be noted that in acidic media (pH <4) rutin is in the
protonated form H4L, the participation of which in complexation is not possible. At pH≥6, rutin
turns into an electron-donating form, which further dissociates with the formation of a flavonolate
ion and can interact with the metal-complexing agent. The largest bathochromic shift λmax for all
studied systems occurs at pH≥5.5 due to the involvement in chelation of different binding sites.
Regardless of the metal, for all systems, the maximum of band I shifts toward long
wavelengths compared to the solution of pure rutin (Fig. 6).
200 300 400 500
0
2
4
Rut
=360 nm =257 nm
Co-Rut
=368 nm =268 nm =204 nm
Cu-Rut
=409 nm=267 nm=209 nm IV=413 nm
,nm
A
bs
or
ba
nc
e
IV
Fig.6 UV spectra of rutin and complexes CoRut, CuRut.
For a Cu-containing system, band I is strongly shifted to the visible region by 53 nm (λmax. = 413
nm, band IV). Under similar conditions, band II of rutin in the presence of metal ions has a
bathochromic shift of ~ 10 nm, but in the spectra of metal complexes appears band III at 204 (209)
nm, which may be due to different modes of coordination of cations to the functional groups of
rutin.
Figure 7 shows a comparison of electronic absorption spectra for systems with different M: Rut
ratios.
Regardless of the metal, for all systems, the
maximum of band I shifts toward long wave-
lengths compared to the solution of pure rutin
(Fig. 6).
For a Cu-containing system, band I is
strongly shifted to the visible region by 53 nm
(λmax. = 413 nm, band IV). Under similar con-
ditions, band II of rutin in the presence of me
tal ions has a bathochromic shift of ~ 10 nm,
but in the spectra of metal complexes appears
band III at 204 (209) nm, which may be due to
different modes of coordination of cations to
the functional groups of rutin.
Figure 7 shows a comparison of electronic
absorption spectra for systems with different
M: Rut ratios.
In the UV spectra of copper complexes with
the Cu:L=2:1 ratio for bands II and I, a hyp-
sochromic shift relative to equimolar metal
complex (λI 277 → 267 nm; λII 420 → 409 nm)
is observed, which can be explained by the dif-
ferent structure of metal complex and an in-
crease in conjugation in the heterocyclic ring.
Probably, at the ratio Cu:L=1:1, chelation oc-
curs at the 5-OH hydroxyl group and the oxy
gen atom of the carbonyl group (4-C=O) of
the C-ring of rutin. The maximum absorption
responsible for the absorption of the A-ring of
rutin (7-OH) for both systems does not actu-
ally change (210 nm), which indicates that the
7-OH group does not participate in complexa
tion due to its lower protic acidity. The forma-
tion of copper complexes with a ratio of 2:1
occurs both due to 5-OH and 4C=O and due
to two hydroxo groups of the catechol frag-
ment. The different structures of the complex-
es are confirmed by the change in the values
of optical density as a function of the pH of
solutions (fig. 7a, inset). The catechol group is
the most likely metal binding site, especially
in alkaline media (pH ≥9) due to the depro-
tonation of hydroxyls. At the ratio Cu: Rut =
2: 1, the copper ion can bind to the hydroxyls
of the catechol groups from two rutin mole-
cules, which are located in orthogonal planes.
The different mode of coordination of Cu(II)
is also evidenced by the position of the bands
of the d – d transition B1g→A1g, corresponding
to planar-square complexes: 644 nm (2:1) and
634 nm (1:1).
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS
98 ISSN 2708-129X. Укр. хім. журн., 2021
INORGANIC CHEMISTRY
Fig. 7 Сomparison of UV spectra for systems with different Cu:Rut (а), Со:Rut (b) rations (рН=6).
Insert: dependence of optical density on pH
at ratios M:Rut = 1:1; 2:1 In the electronic ab-
sorption spectra of Co(II) complexes, regard-
less of the Co: Rut ratio, the maxima of the ab-
sorption bands are at the same wavelength, and
the course of the А → pH curves is the same
(fig. 7, b). This indicates the formation of com-
plexes of the same composition in both systems.
However, at a ratio of 2:1, the spectral bands are
split into 3 components, which may be associ-
ated with the formation of biligand complexes
in which the Co2+ ion is coordinated through
the catechol fragment B of the ring of each ru-
tin molecule. In this case, the cobalt ion is in a
distorted octahedral environment, as evidenced
by the maxima of the d-d transitions in the elec-
tronic absorption spectra corresponding to the
4T1g(F)→ 4T1g(P) transition in high-spin six-co-
ordinate complexes of cobalt(II) (λmax=508 (1:1)
and 512 (2:1) nm). The bathochromic shift λmax
in the 2:1 system is due to the formation of a
tetragonally deformed octahedron of D4h sym-
metry due to a significant spin-orbit interaction
in the excited state 4T1g(P).
7
200 400 600
0.0
0.5
1.0
1.5
2.0
2 4 6 8 10
0.60
0.65
0.70
0.75
Cu:Rut=1:1
Cu:Rut=2:1
A
bc
or
ba
nc
e
pH
A
bc
or
ba
nc
e
Cu:Rut=1:1
, нм
Cu:Rut=2:2
210
267
277
409
420
a
200 300 400 500
0
1
2
3
2 3 4 5 6 7 8 9 10 11
0.3
0.4
0.5
0.6
0.7
0.8
A
bc
or
ba
nc
e
pH
2:1
1:1
Co-Rut
l=390
A
bc
or
ba
nc
e
Cо:Rut=2:1
Cо:Ru=1:1
, нм
204
268
365
b
Fig. 7 Сomparison of UV spectra for systems with different Cu:Rut (а), Со:Rut (b) rations (рН=6).
Insert: dependence of optical density on pH at ratios M:Rut = 1:1; 2:1
In the UV spectra of copper complexes with the Cu:L=2:1 ratio for bands II and I, a
hypsochromic shift relative to equimolar metal complex (λI 277 → 267 nm; λII 420 → 409 nm) is
observed, which can be explained by the different structure of metal complex and an increase in
conjugation in the heterocyclic ring. Probably, at the ratio Cu:L=1:1, chelation occurs at the 5-OH
hydroxyl group and the oxygen atom of the carbonyl group (4-C=O) of the C-ring of rutin. The
maximum absorption responsible for the absorption of the A-ring of rutin (7-OH) for both systems
does not actually change (210 nm), which indicates that the 7-OH group does not participate in
complexation due to its lower protic acidity. The formation of copper complexes with a ratio of 2:1
occurs both due to 5-OH and 4C=O and due to two hydroxo groups of the catechol fragment. The
different structures of the complexes are confirmed by the change in the values of optical density as
a function of the pH of solutions (fig. 7a, inset). The catechol group is the most likely metal binding
site, especially in alkaline media (pH ≥9) due to the deprotonation of hydroxyls. At the ratio Cu:
Rut = 2: 1, the copper ion can bind to the hydroxyls of the catechol groups from two rutin
molecules, which are located in orthogonal planes. The different mode of coordination of Cu(II) is
also evidenced by the position of the bands of the d – d transition B1g→A1g, corresponding to
planar-square complexes: 644 nm (2:1) and 634 nm (1:1).
In the electronic absorption spectra of Co(II) complexes, regardless of the Co: Rut ratio, the
maxima of the absorption bands are at the same wavelength, and the course of the А → pH curves
is the same (fig. 7, b). This indicates the formation of complexes of the same composition in both
systems. However, at a ratio of 2:1, the spectral bands are split into 3 components, which may be
associated with the formation of biligand complexes in which the Co2+ ion is coordinated through
7
200 400 600
0.0
0.5
1.0
1.5
2.0
2 4 6 8 10
0.60
0.65
0.70
0.75
Cu:Rut=1:1
Cu:Rut=2:1
A
bc
or
ba
nc
e
pH
A
bc
or
ba
nc
e
Cu:Rut=1:1
, нм
Cu:Rut=2:2
210
267
277
409
420
a
200 300 400 500
0
1
2
3
2 3 4 5 6 7 8 9 10 11
0.3
0.4
0.5
0.6
0.7
0.8
A
bc
or
ba
nc
e
pH
2:1
1:1
Co-Rut
l=390
A
bc
or
ba
nc
e
Cо:Rut=2:1
Cо:Ru=1:1
, нм
204
268
365
b
Fig. 7 Сomparison of UV spectra for systems with different Cu:Rut (а), Со:Rut (b) rations (рН=6).
Insert: dependence of optical density on pH at ratios M:Rut = 1:1; 2:1
In the UV spectra of copper complexes with the Cu:L=2:1 ratio for bands II and I, a
hypsochromic shift relative to equimolar metal complex (λI 277 → 267 nm; λII 420 → 409 nm) is
observed, which can be explained by the different structure of metal complex and an increase in
conjugation in the heterocyclic ring. Probably, at the ratio Cu:L=1:1, chelation occurs at the 5-OH
hydroxyl group and the oxygen atom of the carbonyl group (4-C=O) of the C-ring of rutin. The
maximum absorption responsible for the absorption of the A-ring of rutin (7-OH) for both systems
does not actually change (210 nm), which indicates that the 7-OH group does not participate in
complexation due to its lower protic acidity. The formation of copper complexes with a ratio of 2:1
occurs both due to 5-OH and 4C=O and due to two hydroxo groups of the catechol fragment. The
different structures of the complexes are confirmed by the change in the values of optical density as
a function of the pH of solutions (fig. 7a, inset). The catechol group is the most likely metal binding
site, especially in alkaline media (pH ≥9) due to the deprotonation of hydroxyls. At the ratio Cu:
Rut = 2: 1, the copper ion can bind to the hydroxyls of the catechol groups from two rutin
molecules, which are located in orthogonal planes. The different mode of coordination of Cu(II) is
also evidenced by the position of the bands of the d – d transition B1g→A1g, corresponding to
planar-square complexes: 644 nm (2:1) and 634 nm (1:1).
In the electronic absorption spectra of Co(II) complexes, regardless of the Co: Rut ratio, the
maxima of the absorption bands are at the same wavelength, and the course of the А → pH curves
is the same (fig. 7, b). This indicates the formation of complexes of the same composition in both
systems. However, at a ratio of 2:1, the spectral bands are split into 3 components, which may be
associated with the formation of biligand complexes in which the Co2+ ion is coordinated through
O.K. Тrunova, М.S. Аrtamonov, T.O. Makotryk
99https://ucj.org.ua
UCJ № 10 / Vol. 87
According to the results of electrospray
mass spectrometry, the composition of the
products formed in the studied systems was
determined (tabl. 3).
Table 3
The mass-to-charge ratio of fragments
and their interpretation in the ESI mass
spectrum of the Co (II) and Cu (II) complex-
es with Rut.
m/z
InterpretationCo(II):Rut Cu (II):Rut
1:1 2:1 1:1 2:1
611 611 611 611 (L+H)+
633 - 636 [NaI(L)]+
668 668 672 672 [МII(L-H)]+
726 725 - 738 [М2
II(L-H5,3’,4’)]+
1278 1282 [МII(L-H3’,4’)L]+
The peak of protonated flavonoid (m/z= 611)
is observed in all spectra. In the mass spectra
of the M:Rut = 2:1 systems, quite intense peaks
with m/z=633 and 636 appear, which corre-
spond to the salts of rutin with Na. In addi-
tion, the ESI MS identified key characteristic
fragments with m/z=668 (for Co) and 672 (for
Cu), which correspond to species [MII(L - H)]+,
which clearly indicates the formation of metal
complexes with monodeprotonated rutine mole
cules. In this case, the peak of the [MII(L - H)]+
ion is the main one in the studied mass spec-
tra. Also in the mass spectra there is a weak-
ly intense peak with m/z = 726 (738), which
corresponds to the formation of dimeric cat-
ions [М2
II(L-H5,3’,4’)]
+, in which 3-d metals
are coordinated by deprotonated catecho
lic hydroxo-groups of the ligand. In ESI MS,
peaks of biligand complexes [МII(L-H3’,4’)L]+
with the inclusion of one neutral rutin molecule
are recorded. Moreover, the intensity of these
peaks is quite small.
CONCLUSIONS. Complex formation has
been studied in the systems M (II) - Rut (M (II)
= Co (II), Cu (II)) in aqueous alcohol solutions
depending on pH and the ratio metal: ligand =
1 :1; 2: 1. It was shown that the structure and
stoichiometric composition of the complexa-
tion reaction products are influenced by such
basic parameters as L:M and the pH value of the
medium. Depending on the pH value, chelation
involves certain binding sites, which primarily
is associated with the redistribution of the elec-
tron density in the flavonoid molecule.
In a weakly acidic or neutral medium, re-
gardless of the M(II): Rut ratio, the formation
of monoligand complexes of rutin with 3-d
metals occurs with the participation of 5-OH
and 4-C=O fragments of the A and C rings,
and in an alkaline medium, chelation proceeds
on the catecholic fragment of ring B rutin.
Biligand complexes are formed with the parti
cipation of the gydroxo groups of the catechol
fragment of each rutin molecule, and the for-
mation of compounds with a ratio of 2:1 occurs
both due to 5-OH and 4C=O and due to 3 ',
4'-OH groups. The calculated values of the sta-
bility constants of the complexes showed that
the stability of the Co (II) complexes is several
orders of magnitude lower than the stability of
the corresponding Cu (II) complexes.
ACKNOWLEDGEMENTS
This work was supported by funding
from the National Academy of Sciences
of Ukraine (318 E – program), «Crea-
tion of new multifunctional nanomate-
rials based on coordination compounds
of 3d-metals and lanthanides with O,
N-donor ligands».
SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS
100 ISSN 2708-129X. Укр. хім. журн., 2021
INORGANIC CHEMISTRY
СПЕКТРОСКОПІЧНІ ДОСЛІДЖЕННЯ КОМП
ЛЕКСІВ Cu(II) ТА Co(II) З РУТИНОМ У РОЗЧИНІ
O. К. Трунова*, М. С. Артамонов,
T. O. Maкотрик
Інститут загальної та неорганічної хімії
ім. В. І. Вернадського НАН України, просп.
Академіка Палладіна, 32/34, Київ 03142,
Україна
* e-mail: trelkon@gmail.com.
Методами електронної спектроскопії
поглинання та pH-метричного титруван-
ня вивчено комплексоутворення в систе-
мах M(II) – рутин (Rut) (M(II) = Co, Cu) у
водно-етанольних розчинах залежно від
співвідношення метал:ліганд (1:1; 2: 1) і рН
середовища. Показано, що на структуру та
стехіометричний склад продуктів реакції
комплексоутворення впливають такі ос-
новні параметри, як L:M та значення pH
середовища. Залежно від значення pH, в
хелатуванні беруть участь певні сайти зв'я-
зування, що, перш за все, пов'язано із пере-
розподілом електронної густини в молекулі
флавоноїду. У слабокислому або нейтраль-
ному середовищі, незалежно від співвідно-
шення M(II):Rut, утворення монолігандних
комплексів рутину з 3-d-металами відбува-
ється за участю 5-OH і 4-C=O фрагментів А
і C кільця, а в лужному середовищі хелату-
вання відбувається на катехольному фраг-
менті кільця B рутину. Білігандні комплек-
си утворюються за участю гідроксогруп ка-
техольного фрагменту кожної молекули ру-
тину, а утворення сполук у співвідношенні
2:1 відбувається як за рахунок 5-OH і 4C=O,
так і за рахунок 3', 4'-OH груп. Розрахова-
ні значення констант стійкості комплексів
показали, що стійкість комплексів Co(II)
на кілька порядків нижча за стійкість від-
повідних комплексів Cu(II).
Ключові слова: комплекс, мідь, кобальт,
рутин, флавоноїди, електронна спектро
скопія.
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Стаття надійшла 16.11.2021.
|
| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-371 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:07:09Z |
| publishDate | 2021 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/89/875f6fb405866ee57a016b9960bb9e89.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-3712026-07-22T08:23:47Z SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS Trunova , Elena Artamonov, Michailo Makotryk , Tamara complexes, copper, cobalt, rutin, flavonoids, absorption spectra. Complexation in M (II) – Rut systems (M(II) = Co, Cu) was studied by electron absorption spectroscopy and pH-metric titration in water-ethanol solutions depending on the metal: ligand ratio (1: 1; 2: 1) and the pH of the medium. It was shown that the structure and stoichiometric composition of the complexation reaction products are influenced by such basic parameters as L:M and the pH value of the medium. Depending on the pH value,&nbsp; chelation involves certain binding sites, which primarily is associated with the redistribution of the electron density in the flavonoid molecule. In a weakly acidic or neutral medium, regardless of the M(II): Rut ratio, the formation of monoligand complexes of rutin with 3-d metals occurs with the participation of 5-OH and 4-C=O fragments of the A and C rings, and in an alkaline medium, chelation proceeds on the catecholic fragment of&nbsp; ring B rutin. Biligand complexes are formed with the participation of the gydroxo groups of the catechol fragment of each rutin molecule, and the formation of compounds with a ratio of 2:1 occurs both due to 5-OH and 4C=O and due to 3 ', 4'-OH groups. The calculated values of the stability constants of the complexes showed that the stability of the Co (II) complexes is several orders of magnitude lower than the stability of the corresponding Cu (II) complexes. V.I.Vernadsky Institute of General and Inorganic Chemistry 2021-11-26 Article Article Inorganic Chemistry Неорганическая химия Неорганічна хімія application/pdf https://ucj.org.ua/index.php/journal/article/view/371 10.33609/2708-129X.87.10.2021.90-102 Ukrainian Chemistry Journal; Vol. 87 No. 10 (2021): Ukrainian Chemistry Journal; 90-102 Украинский химический журнал; ##issue.vol## 87 ##issue.no## 10 (2021): Ukrainian Chemistry Journal; 90-102 Український хімічний журнал; Том 87 № 10 (2021): Український хімічний журнал; 90-102 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/371/192 Copyright (c) 2021 Elena Trunova , Michailo Artamonov, Tamara Makotryk https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Trunova , Elena Artamonov, Michailo Makotryk , Tamara SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS |
| title | SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS |
| title_full | SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS |
| title_fullStr | SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS |
| title_full_unstemmed | SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS |
| title_short | SPECTROSCOPIC STUDIES OF Cu (II) AND Co (II) COMPLEXES WITH RUTIN IN SOLUTIONS |
| title_sort | spectroscopic studies of cu (ii) and co (ii) complexes with rutin in solutions |
| topic_facet | complexes copper cobalt rutin flavonoids absorption spectra. |
| url | https://ucj.org.ua/index.php/journal/article/view/371 |
| work_keys_str_mv | AT trunovaelena spectroscopicstudiesofcuiiandcoiicomplexeswithrutininsolutions AT artamonovmichailo spectroscopicstudiesofcuiiandcoiicomplexeswithrutininsolutions AT makotryktamara spectroscopicstudiesofcuiiandcoiicomplexeswithrutininsolutions |