Solid complexes of iron(II) and iron(III) with rutin

Article abstract of DOI:10.1007/s11224-009-9531-z

Solid complex compounds of Fe(II) and Fe(III) ions with rutin were obtained. On the basis of the elementary analysis and thermogravimetric investigation, the following composition of the compounds was determined: (1) FeOH(C₂₇H₂₉O

Full text of DOI:10.1007/s11224-009-9531-z

Struct Chem (2010) 21:323–330
DOI 10.1007/s11224-009-9531-z
ORIGINAL PAPER
Solid complexes of iron(II) and iron(III) with rutin
•
Dorota Nowak Anna Kuzniar Maria Kopacz
•
´
Received: 22 October 2009 / Accepted: 28 October 2009 / Published online: 14 November 2009
Ó Springer Science+Business Media, LLC 2009
Abstract Solid complex compounds of Fe(II) and Fe(III)
ions with rutin were obtained. On the basis of the elemen-
tary analysis and thermogravimetric investigation, the fol-
lowing composition of the compounds was determined: (1)
FeOH(C27H29O16)ꢀ5H2O, (2) Fe2OH(C27H27O16)ꢀ9H2O, (3)
Fe(OH)2(C27H29O16)ꢀ8H2O, (4) [Fe6(OH)2(4H2O)(C15H7O12)
SO4]ꢀ10H2O. The coordination site in a rutin molecule was
established on the basis of spectroscopic data (UV–Vis and
IR). It was supposed that rutin was bound to the iron ions via
4C=O and 5C—oxygen in the case of (1) and (3). Groups
5C–OH and 4C=O as well as 30C–OH and 40C–OH of the
ligand participate in binding metals ions in the case of (2).
At an excess of iron(III) ions with regard to rutin under the
synthesis conditions of (4), a side reaction of ligand oxi-
dation occurs. In this compound, the ligands’ role plays a
quinone which arose after rutin oxidation and the substitu-
tion of Fe(II) and Fe(III) ions takes place in 4C=O, 5C–OH
as well as 40C–OH, 30C–OH ligands groups. The magnetic
measurements indicated that (1) and (3) are high-spin
complexes.
Introduction
Flavonoids are a group of compounds characterized by
diverse structure and various biological activities. In the
nature, they are widespread as glycosides and in this form
are well absorbed by the body organisms. Bioflavonoids
used to be called vitamin P. In fresh plants, rutin occurs
frequently with vitamin C because it has similar properties
to vitamin C; these substances well complement one
another. In health care, a specimen including both com-
pounds is administered. Rutin increases flexibility and
tightness of capillaries, which efficacious that the vessels
keep the plasma proteins out—these proteins are often
responsible for skin inflammatory and allergy [1].
In recent years, hydroxyflavones have been intensively
determined for the sake of their antioxidant properties
[2–9]. In [5], it was stated that flavonoids, which are
capable of binding metal ions, are less susceptible to oxi-
dation than free compounds.
Flavonoids’ complex and redox properties are connected
with hydroxyl group position in a molecule. In rutin mol-
ecule (5,7,30,40-tetrahydroxyflurone-3-b-D-rutinoside), the
following coordination sites of metal ions are possible
(Fig. 1).
Keywords Iron ꢀ Rutin ꢀ
Spectroscopic and magnetic properties
Iron as a hemoglobin component plays an important
biological role in human organism. However, iron excess is
harmful because of the increase in oxidation stress and
formation of reactive oxygen species, which efficacious
lipid, protein, and nucleic acids oxidation [10].
Dedicated to Professor Adam Bartecki on the occasion of his 90th
birthday.
Chelation (especially iron) potency among other things
rutin and radical scavenging activities of flavonoids are most
useful for inhibition of lipid peroxidation description [6, 7].
van Acker et al. [8] stated that the scavenger potencies of
flavonoid (rutin) metal (Cu2?, Fe2?, and Fe3?) complexes
were significantly higher than those of the parent flavonoid.
´
D. Nowak ꢀ A. Kuzniar (&) ꢀ M. Kopacz
Department of Inorganic and Analytical Chemistry, Chemical
´ ´
Faculty, Rzeszow University of Technology, 6 Powstancow
´
Warszawy Ave, P.O. Box 85, 35-959 Rzeszow, Poland
e-mail: akuzniar@prz.edu.pl
123

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Struct Chem (2010) 21:323–330
Erba, Italy). The contents of iron were determined by a
gravimetric and spectrophotometric methods (spectropho-
tometer SPECOL 10, Carl Zeiss Jena, Germany). The ther-
mogravimetric analysis was carried out in air using an
OD-102 derivatograph, F. Paulik-J. Paulik-L. Erdey system
(MOM, Hungary). The UV–Vis spectra of the complexes in
water and methanol were taken with a Beckman DU-640
spectrophotometer (Beckman, Germany). IR spectra were
made on FTIR spectrophotometer model IFS 66/S (BRUC-
KER, Ettlingen, Germany). Measurements of magnetic
susceptibility of the complexes of Fe(II) and Fe(III) with
rutin were made with a Quantum Desigon SQUID magne-
tometer (type MPMS-5).
OH
II
2' 3'
8
4'
1'
9
10
I
OH
O
HO
B
2
7
A
C
5'
3
6'
6
O
C12H21O9
5
4
OH
O
Fig. 1 Possible coordination sites of metal ions in rutin molecule
In [9], it was also shown that the iron and copper
complexes of flavonoids were much more effective than
the uncomplexed polyphenols in protecting isolated rat
hepatocytes against hyposia-reoxygenation injury.
Deng et al. [11] emphasize that flavonoids’ (baicalin,
hesperidin, naringin, quercetin, and rutin) function as anti-
oxidant mainly depends on chelating iron ions and scav-
enging peroxyl radicals, whereas their OH radical
scavenging effect is much less important. What’s more,
quercetin and rutin are the most effective in scavenging
peroxyl radicals because of their structure—phenolic
hydroxyl groups in the B-ring are more liable to peroxyl
radical attack.
Reagents
Solutions (0.1 and 0.05 mol dm-3) of rutin (Koch-Light
Laboratories Ltd., UK) were obtained by dissolving the
appropriate weighed amounts of compounds in methanol.
0.1 mol dm-3 solutions of iron(II) and iron(III) sulfate(VI)
were obtained by dissolving the appropriate weighed
amounts of the salts in redistilled water and acidifying them
with a 1 mol dm-3 H2SO4 solution. All reagents were ana-
lytically pure. The solutions were prepared directly before
synthesis.
Experiments on animals [12] (rats) showed that com-
plexation copper(II) ions by rutin increase antioxidant and
anti-inflammatory activity of bioflavonoid. Whereas the
antioxidant activity of Fe(rut)Cl3 was much lower and in
some cases approached that of rutin.
Preliminary tests
In order to estimate the optimal pH value of iron(II) and
iron(III) complexation by rutin, the preliminary tests were
carried out in methanol-aqueous solutions (1:1) using
spectrophotometric method. The absorbance dependence of
wavelength and pH was determined. Two series of solu-
tions were prepared.
In [13], it was stated that the selective inhibitory effect
of rutin under pathologic conditions induced by iron
overload is thought to be due to the formation of inactive
iron–rutin complexes which are unable to catalyze the
conversion of superoxide ion into reactive hydroxyl radi-
cals, a process responsible for the free radical-mediated
toxic effect of iron overload.
Series I—cM:cL = 1:5, series II—cM:cL = 5:1 (cM and
cL—molar concentration of metal and ligand, respec-
tively); the tested solutions were green–yellow. pH within
3–7 was fixed with 0.01 mol dm-3 NaOH and H2SO4
solutions. The spectra in the range 300–800 nm were taken
on SPECORD UV VIS spectrophotometer (Carl Zeiss
Jena) at 293 1 K.
In the above-mentioned publications, the examinations
were carried out in solutions and they concerned mainly
biological properties of rutin complexes with some transi-
tion metal ions.
In this article, the synthesis of solid-state complexes of
Fe(II) and Fe(III) ions with rutin was carried out. Some of
physicochemical properties of the obtained compounds
were examined.
In visible region was observed:
–
–
for Fe(II) over pH = 4 bathochromic shift of ligand
band by 6 nm and inflexion formation at k = 417 nm,
for Fe(III) over pH = 4.5 inflexion at k = 417 nm.
On the basis of examinations, pH = 5.5 was chosen as
Experimental
the optimal environment of iron complexation by rutin.
Apparatus
Synthesis of complexes
The elemental analysis for C, H, N, and S was performed
with an Elemental Analyser EA 1108 apparatus (Carbo
The synthesis of the complexes was carried out using an
excess of metal ions with relation to the ligand;
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Struct Chem (2010) 21:323–330
325
cM:cL = 5:1 and with the ligand excess in relation to metal
cations, cM:cL = 1:5. To this end, an appropriate volume of
rutin was mixed with an appropriate volume of the initial
metal ion solution at room temperature. The syntheses were
carried out in methanol-aqueous solutions (1:1), and
pH = 5.0 were fixed with 0.10 and 0.01 mol dm-3 NaOH
solutions. The time of each reaction was 8, 96, and 196 h.
Amorphous sediment precipitated, which, after appropriate
time, was filtered off and rinsed several times in methanol-
aqueous solutions (1:1). Next, the sediments were dried in
air at room temperature. All obtained compounds were
black, only Fe(III)–rutin complexes, cM:cL = 5:1 (96 and
196 h), characterized by metallic lustre.
At an excess of iron(III) ions with regard to rutin under
the synthesis conditions, a side reaction of rutin oxidation
occurs—its equilibrium establishes after 96 h. It was stated
that in a shorter time of reaction a mixture with indeter-
minate composition forms.
Thermogravimetric analysis
The investigation was carried out in air under the following
conditions: sensitivity TG—100 mg, temperature 293–
1273 K, DTA—1/15, DTG—1/5, time 100 min. The
results were listed in Table 1 and presented, for selected
compound, in Fig. 2.
Composition of complexes
Spectral measurements
The contents of C, H, and S in the compounds under
investigation were determined using a Carbo Erba EA-
1108 elemental analyser. The amount of iron was estab-
lished by the spectrophotometric and gravimetric methods
[14]. The gravimetric (drying at 393 K) and derivato-
graphic methods were applied to find the content of crys-
tallization water in the complexes.
The UV–Vis spectra of rutin and its complexes were taken
in water and methanol (Figs. 3 and 4). The infrared spectra
were carried out in KBr pellets in the range 4000–400 and
600–50 cm-1, the samples were powered and suspended in
the Nujol mull and were then inserted between two poly-
ethylene windows. Table 2 lists the results of the UV–Vis
spectral examination and the oscillation frequencies of the
chosen infrared bands.
Anal. Calcd. for (1) FeOH(C27H29O16)ꢀ5H2O (cFe2þ
:
cL = 1:5; regardless of synthesis time): C, 41.98; H, 5.22;
Fe, 7.23; H2O, 11.66. Found: C, 42.35; H, 5.16; Fe, 7.36;
H2O, 11.50. Anal. Calcd. for (2) Fe2OH(C27H27O16)ꢀ9H2O
(cFe2þ :cL = 5:1, regardless of synthesis time): C, 36.10; H,
5.16; Fe, 12.43; H2O, 18.05. Found: C, 35.80; H, 4.75; Fe,
12.48; H2O, 18.00. Anal. Calcd. for (3) Fe(OH)2(C27H29O16)ꢀ
8H2O (cFe2þ :cL = 1:5, regardless of synthesis time): C,
38.44; H, 5.62; Fe, 6.62; H2O, 17.09. Found: C, 38.73; H,
5.29; Fe, 6.46; H2O, 17.00. Anal. Calcd. for (4) [Fe6(OH)2
(4H2O)(C15H7O12)SO4]ꢀ10H2O (cFe2þ :cL = 5:1, 96 and
196 h): C, 16.43; H, 3.40; S, 2.92; Fe, 30.56; H2O, 16.43.
Found: C, 16.13; H, 3.47; S, 2.87; Fe, 30.82; H2O, 16.10.
Magnetic measurements
Measurements of magnetic susceptibility of the complexes
of Fe(II) and Fe(III) with rutin were made with a Quantum
Desigon SQUID magnetometer (type MPMS-5) in the
temperature range from 2 to 300 K and magnetic field of
5 kOe. The contribution of the support cell was indepen-
dently measured and subtracted. The correction for dia-
magnetism of the constituent atoms was calculated using
Pascal’s constants [15] and found to be -3.79 9 10-4
-5.22 9 10-4, -5.11 9 10-4, -4.83 9 10-4 cm3 mol-1
,
Table 1 Temperature values of thermal decomposition of rutin complexes with Fe(II) and Fe(III)
DTG
min
DT1 (K)
T
DT2 (K)
Tk (K)
% H2O
Calc.
nH2O
% Residue mass
Final decomposition
product
Obtain.
Calc.
Obtain.
(1) FeOH(C27H29O16)ꢀ5H2O
293–463 393 463–1053
(2) Fe2OH(C27H27O16)ꢀ9H2O
293–423 363 423–1063
(3) Fe(OH)2(C27H29O16)ꢀ8H2O
293–453 363 453–1053
1053
1063
1053
11.7
18.0
17.1
16.4
11.5
18.0
17.0
17.0
5
9
10.3
17.8
9.5
10.0
17.5
9.0
Fe2O3
Fe2O3
Fe2O3
8
(4) [Fe6(OH)2(4H2O)(C15H7O12)SO4]ꢀ10H2O
293–383
333
443–1273
–
10
Continuous loss of mass was observed at 1273 K
383–443
393
DT1 (DT2), temperature range corresponding to dehydration endoeffect of definite amount of water molecules (corresponding to decomposition of
anhydrous compound); TmDiTnG; temperature corresponding to minimum on DTG curve; Tk, temperature of final product formation
123

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Struct Chem (2010) 21:323–330
1,0
0,5
0,0
4
3
1
4
6
3
7
2
5
5
Fig. 2 TG, DTG, and DTA curves of compound (2) in air
7
300
400
500
1,5
wavelength, nm
Fig. 4 Absorption spectra in visible and ultraviolet ranges of water and
methanol solutions of rutin and rutin–Fe(III) complexes (l = 1 cm): 1
rutin in water, 2 rutin in methanol (c = 3.00 9 10-5 mol dm-3), 3
Fe(OH)2(C27H29O16)ꢀ8H2O, (3) (water), 4 Fe(OH)2(C27H29O16)ꢀ8H2O,
4
3
6
1,0
(3) (methanol),
5
[Fe6(OH)2(4H2O)(C15H7O12)SO4]ꢀ10H2O, (4)
4
(water), 6 [Fe6(OH)2(4H2O)(C15H7O12)SO4]ꢀ10H2O, (4) (methanol),
5
7
solution from above complex precipitate [Fe6(OH)2(4H2O)
3
(C15H7O12)SO4]ꢀ10H2O after 96 h. Saturated solutions unless stress
differently
0,5
6
5
2
1
precipitate. It was found that the composition of the com-
plexes depends on the synthesis conditions. If there is an
excess of ligand in the solution, (1) FeOH(C27H29O16)ꢀ
5H2O and (3) Fe(OH)2(C27H29O16)ꢀ8H2O complexes
appear. However, in the case of metal cation excess, a iron
complexes of the (2) Fe2OH(C27H27O16)ꢀ9H2O and (4)
[Fe6(OH)2(4H2O)(C15H7O12)SO4]ꢀ10H2O compositions are
formed.
0,0
300
400
500
600
700
wavelength, nm
Fig. 3 Absorption spectra in visible and ultraviolet ranges of water
and methanol solutions of rutin and rutin–Fe(II) complexes
(l = 1 cm): 1 rutin in water, 2 rutin in methanol (c = 3.00 9
10-5 mol dm-3), 3 FeOH(C27H29O16)ꢀ5H2O, (1) (water), 4 FeOH
(C27H29O16)ꢀ5H2O, (1) (methanol), 5 Fe2OH(C27H27O16)ꢀ9H2O, (2)
(water), 6 Fe2OH(C27H27O16)ꢀ9H2O, (2) (methanol). Saturated solu-
tions unless stress differently
Compounds directly after educe from reaction mixture
are well soluble in water, slightly in methanol. After being
air dried, they are sparingly soluble in water as well as
methanol (solubility of the order of 10-6 mol dm-3 at
293 K). Better solubility of wet compounds is the cause of
appearance of intermolecular hydrogen bonds. In [16], it
was stated that intermolecular hydrogen bonds have an
influence on solubility of flavone in ethanol.
per molecule of complexes (1)–(4), respectively. The
effective magnetic moments were calculated using the
formula: leff = 2.83(vM ꢀ T)1/2 B.M., where vM magnetic
susceptibility of the iron ions with an allowance for dia-
magnetism, T temperature in K. For the investigated
compounds, the Weiss constants (H) were calculated from
the least squares fitting of the 1/vM versus T curves. The
Curie constants (C) were determined from vM ꢀ T = f(T)
dependence for T equals 300 K.
In [17–19], it was stated that apart from complexation,
the oxidation reactions between some metal ions and
flavonoids occur. Polihydroxyflavones are oxidizing to
quinones in presence of mostly metal cations on the highest
oxidation numbers. Ability to reduction is related to redox
potential and number of hydroxyl group in flavonoid
molecule. Less amount of OH group reduces possibility of
hydrogen loss and because of that it reduces ability for
flavonoid oxidation and metal reduction. The presence in
ring C 2C=3C bound coupling with 4C=O is also very
important. The presence of oxidized form of flavonoid
could be stated by spectrophotometric method; if in
Results and discussion
Synthesis of the complexes of Fe(II) and Fe(III) with
rutin
Due to mixing methanol-aqueous solutions of iron cations
and rutin at pH = 5.5, black, amorphous deposits
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Struct Chem (2010) 21:323–330
327
Table 2 UV–Vis and IR spectra of rutin and the complexes of rutin with Fe(II) and Fe(III)
Compound UV–Vis
Wavelength (nm)
Water
Band I Band II Band III Band IV Band I Band II Band III 4C=O 2C=3C 9C–O–2C M–O
IR band
m (cm-1
)
Methanol
M–OH
–
Rutin
(1)
–
353
413
406
397
336
–
258
274
273
270
256
–
361
406
367
367
385
258
275
268
263
274
1653s 1598s
1131w
1120w
1121m
–
556
556
556
–
–
556
556
556
556
1648sh
1618s
1648sh
1618s
1648sh
1618s
1618s
408w
408w
408w
290w
290w
–
(2)
–
1121m
1121m
1119s
(3)
–
(4)
294
412m-br 290w
Intensity of bands is given by s = strong, m = medium, w = weak; sh, shoulder on strong band; br, broad
UV–Vis range band on kmax in the range 284–294 nm
appears [19].
and iron(III) was checked by means of 2,20-bipyridine and
ammonium thiocyanate, respectively. The analysis reveals
that in compounds (1) and (2) occurs iron(II), compound
(3) includes iron(III), (4) is the mixed valence compound
and in this connection could be semiconductor [22]; ten-
tatively carry out conductivity test confirms this
presumption.
In connection with above mentioned, in this article for
all syntheses, UV–Vis spectra for solution from above
complex precipitate were performed. It was stated that only
in the case of iron(III) complex (cM:cL = 5:1) already after
8 h synthesis conduction the oxidation of rutin occurs.
Equilibrium of process establishes after 96 h (Fig. 4).
Under the investigation conditions, the aqua-complexes
of iron(II), hydroxo-complexes of iron(III), and ligands,
rutin ions, sulfate(VI), and hydroxyl ions may occur. The
Thermogravimetric analysis
Thermogravimetric investigation confirmed the elementary
analysis results and the composition of the complexes
obtained. The acquired temperature data with regard to the
composition of the investigated compounds (see Table 1)
seem to indicate that the compounds are subject to gradual
decomposition with a rise in temperature. The occurrence
of endothermal effects (DTA curve) is due to the separation
of crystallization water in the temperature range 293–
463 K. Further stages of the thermal changes are due to the
loss of function groups or the destabilization of the com-
plex structure and burning of organic ligands. The total
value of these effects is observed as exothermic effects on
the DTA curve. Above 1053 K, the final decomposition
product, Fe2O3, was formed (see Table 1). The thermolysis
of (4) complex did not reach equilibrium state in the tested
temperature range.
þ
border pH value of hydroxo-complex formation (pH
)
½MOHꢁ
amounts to pKw—2 - logb1, where b1 is a first stability
constant of appropriate hydroxo-complex [20]. For the
þ
investigated metal ions, the pH
values are equal:
½MOHꢁ
þ
–
–
pH
pH
¼ 7:5ðlog b1 ¼ 4:5Þ;
½FeOHꢁ
½FeOHꢁ
2þ ¼ 1:0ðlog b1 ¼ 11:0Þ:
Taking into consideration the above-mentioned data, it
seems probable that mixed complexes were formed where
flavonoid, sulfate(VI), hydroxyl ions, and water molecule
are the ligands. As an example, complexation for (3) were
described with the following equations:
Â
Ã
Â
Ã
FeðH2OÞ 3þþ H2O ꢀ FeðH2OÞ OH þ H3Oþ; ð1Þ
2þ
6
5
Â
Ã
Â
Ãþ
FeðH2OÞ OH 2þþ H2O ꢀ FeðH2OÞ ðOHÞ þ H3Oþ;
5
4
2
ð2Þ
Electronic spectra
Â
Ãþ
FeðH2OÞ4ðOHÞ2 þ H3Lꢂ ꢀ FeðOHÞ2ðH3LÞ þ 4H2O;
UV–Vis spectra of the rutin and the investigated complexes
were taken in water and methanol (Figs. 3 and 4). The rutin
spectrum in methanol (water) has two p ? p* intensive
absorption transfer bands. According to [23, 24], band I, at
361 (353) nm, is considered to be associated with
ð3Þ
where H3L-—rutin ion existed in solution at pH 5.5 [21].
For aqueous solutions of obtained compounds, the
qualitative tests were performed. The presence of iron(II)
123

328
Struct Chem (2010) 21:323–330
absorption due to the ring B cinnamoyl system (with 3C-
sugar group), and band II, at 258 nm, with absorption
involving the A ring (with 5C–OH group) benzoyl system.
In the spectra of (1) FeOH(C27H29O16)ꢀ5H2O, (2)
Fe2OH(C27H27O16)ꢀ9H2O, and (3) Fe(OH)2(C27H29O16)ꢀ
8H2O taken in methanol band I are bathochromically
shifted by 45, 6, and 6 nm, respectively, and band II at
258 nm are shifted by 17, 10, and 5 nm, respectively.
The observed changes at bands position might be the
evidence for the metal ion being bound by appropriate part
of ligand molecule. Coordination of iron in 4C=O and
C5–OH position for compound (1) causes the largest bands
shift. Next, in the case of (3), substitution of iron ion in ring
B shifts the ligand bands insignificant. The compound (2)
has two iron ions bounded by 4C=O and C5–OH as well as
C30–OH and C40–OH [25–27].
oxidized form of rutin (quinone) and is the complex of
strong field [30].
Infrared spectra
The IR spectra of the investigated compounds were made
within the range 4000–50 cm-1. As diagnostic frequen-
cies, the vibration frequencies of the carbonyl [4C=O
and etheric 9C–O–2C– groups, and also Fe–O as well as
Fe–OH bounds (see Table 2) were taken into consider-
ation. Complexity of flavonoids IR spectra makes the
interpretation difficult. In rutin, spectrum in the same
frequencies range bands of sugar moiety and aglycone is
observed. Spectra of compounds (1)–(3) are similar. The
different character of (4) spectra confirms its different
structure.
However, in (4) [Fe6(OH)2(4H2O)(C15H7O12)SO4]ꢀ
10H2O, the lack of sugar group in the position C3–OH makes
possible a different way of metal binding which results in dif-
ferent shift values: 24 nm for band II and 16 nm for band I.
Besides, in the spectra of all complexes, there is an
intensive at about 556 nm which arises from overlapping
charge-transfer band L ? M and d–d transitions.
In the spectra of water solutions of (1)–(3) compounds,
the same direction of band shift as in methanol is observed,
but their values are much higher; for band II 60, 53, and
44 nm, respectively. These data are a result of different
solvation of the central ion in water and methanol [28].
In (4), band II is hipsochromically shifted by 17 nm, a
position of band IV is practically unchangeable, the new
band at 294 nm is observed—this band is connected with
oxidized form of rutin. These data strongly suggest that the
quinone arising from rutin is the ligand (Scheme 1) and
Fe2? and Fe3? are chelated by 5C–OH, 4C=O and 30C–OH,
40C–OH systems.
As a result of coordination of iron by rutin, an
overlapping band [4C=O (1653 cm-1) with 2C=3C
(1598 cm-1) occurs and a strong band at 1618 cm-1 is
observed. Additionally, in spectra compounds (1)–(3) a
shoulder at 1648 cm-1 appears. Symmetrical vibrations
band of etheric group in ring C of rutin is split into two
frequencies at 1131 and 1120 cm-1. In spectra of com-
plexes, this splitting is not observed but the intensity is
changed; this band appears in the range 1121–1119 cm-1
.
These facts suggest that the oxygen in ring C does not take
part in the metal bond; appears a resonance amplifying
bound C–O [31].
For compounds (1)–(3), a new band at 408 cm-1
appears, it is related to Fe–O vibration. For (4), this band
occurs at 412 cm-1 shows medium intensity and is sig-
nificantly broad which may be a result of Fe–O–Fe inter-
action [32, 33].
The confirmation of formation obtained compounds as
hydroxycomplexes is the occurrence of frequencies of
Fe–OH group in the far infrared (290 cm-1) [34].
FIR spectra were recorded in order to characterize the
participation of sugar group in metal binding and metal–
metal bridge formation. The lack of strong, broad band at
200 cm-1 is the evidence of lack metal–sugar bound [35].
In the range 260–170 cm-1 [34], there is no additional
vibration connected with metal–metal interaction.
Similar to methanolic solutions, for all obtain complexes
a new band at 556 nm was observed.
On the basis of UV–Vis spectra in methanol, the values
of splitting in ligands field (D) [29] were calculated: (1)
21750 cm-1, (2) 22100 cm-1, (3) 22600 cm-1 as well as
(4) 26700 cm-1. Obtained D pointed that described com-
pounds (1)–(3) are the complexes of medium field formed
by the same ligand (rutin ion); however, (4) was formed by
Scheme 1 Oxidation of rutin
by iron(III)
OH
OH
2' 3'
8
1'
4'
O
O
3+
Fe
2
3
HO
7
HO
OH
O
5'
6'
6
O
O
Rutinoside
5
4
OH
O
OH
O
123

Struct Chem (2010) 21:323–330
Magnetic measurements
329
metal–metal interactions may occur which can be observed
as decrease in magnetic moment [38].
In order to estimate magnetic properties, the oxidation
number of metal ions, and the structure of the iron–rutin
complexes, the magnetic measurements were carried out.
Dependences vM = f(T) and leff = f(T) for all examinated
compounds are analogous, shown in Fig. 5.
Complexes (1) and (2) obey Curie law, and the
appropriate Curie constants (C) amount to 2.2 and
2.8 cm3 K mol-1
.
Compounds (3) and (4) obey the Curie–Weiss law;
C and Weiss constants (h) are equal: for (3) C =
4.8 cm3 K mol-1
;
h = -8.7 K; and for (4) C =
On the basis of vM = f(T), one may say that for
complexes (1)–(4) as T increased, vM smoothly lowered
and then tended to a plateau at ca. 100 K. Then the vM
values are 2.42 9 10-2, 3.05 9 10-2, 4.26 9 10-2, and
7.75 9 10-2 cm3 K mol-1, respectively. Calculated val-
ues of magnetic moments pointed that the obtained com-
plexes are paramagnetic. The values of effective magnetic
moments [M.B.] at 300 and 1.9 K are (1) 4.82, 3.14, (2)
5.45, 3.43, (3) 6.18, 3.21, and (4) 8.60, 3.18.
9.2 cm3 K mol-1; h = -14.3 K. This is probably the
consequence of antiferromagnetic spin interaction [for
compounds (3) and (4), the Weiss constants have a nega-
tive sign] or CF splitting of the paramagnetic spin state—
complexes (1) and (2) [37, 39, 40].
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123

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