Synthesis and Physicochemical Study of Solid Complexes of Ti(IV), Zr(IV), and Zn(II) with Chrysin

Article abstract of DOI:10.1023/A:1025665225524

Previously unknown solid complexes of Ti(IV), Zr(IV), and Zn(II) with chrysin were isolated, identified, and studied by thermogravimetric analysis and by UV-Vis, IR, and NMR spectroscopy.

Full text of DOI:10.1023/A:1025665225524

Russian Journal of General Chemistry, Vol. 73, No. 4, 2003, pp. 634 637. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 4, 2003,
pp. 671 675.
Original Russian Text Copyright
2003 by Pusz, Nitka, Kopacz, Korenman.
Synthesis and Physicochemical Study of Solid Complexes
of Ti(IV), Zr(IV), and Zn(II) with Chrysin
J. Pusz, B. Nitka, S. Kopacz, and Ya. I. Korenman
Polytechnic University, Rzeszow, Poland
Voronezh State Technological Academy, Voronezh, Russia
Received April 21, 2001
Abstract Previously unknown solid complexes of Ti(IV), Zr(IV), and Zn(II) with chrysin were isolated,
identified, and studied by thermogravimetric analysis and by UV-Vis, IR, and NMR spectroscopy.
Flavonoids are vegetable dyes absent in animal
cells but present in virtually all plants, in particular, in
fruits, flowers, leaves, and wood. Flavonoids are meth-
oxy and glycoside derivatives of flavone (2-phenyl- -
benzopyrone); they contain a system of two aromatic
rings linked by a triangular aliphatic chain [1, 2].
and Zn(II) with chrysin, determined their composition,
and studied their physicochemical properties.
Previously unknown solid complexes of Ti(IV),
Zr(IV), and Zn(II) with chrysin were prepared by
mixing hot solutions of the appropriate starting com-
pounds. The complexes are yellow. Their composi-
tions were determined by elemental (Table 1), thermo-
gravimetric, complexometric, and gravimetric anal-
yses and are as follows: Ti(C15H9O4)4, Zr(C15H9O4)4
8H2O, and Zn(C15H9O4)2 2H2O.
Flavonoids containing OH groups at the C atoms
in positions 3, 5, 3 , and 4 exhibit increased biological
activity and form stable complexes with metals. This
property is used for treating heavy metal poisonings
[3]. Thanks to the complexing power, flavonoids are
also used as dyes in textile industry and as reagents
for photometric and gravimetric determination of
many metals [4].
The physicochemical properties of the complexes
were studied by thermogravimetric analysis (Table 2)
and by UV-Vis (Table 3), IR (Table 4), and NMR
spectroscopy (Table 5).
The thermal decomposition of chrysin and its
Ti(IV), Zr(IV), and Zn(II) complexes was studied in
air in the range 293 1273 K. Chrysin is an anhydrous
compound and shows no effects due to dehydration
in the range 293 553 K. Starting from 578 K, chrysin
starts to decompose exothermally in several stages.
The decomposition is complete at 1095 K (100%
weight loss).
The best known and most widely used flavonoids
are quercetin, morin, rutin, and their sulfo derivatives
[5 8]. Less studied is chrysin ([5,7-dihydroxyflavone,
C15H10O4), which, similar to the above-mentioned
flavonoids, is insoluble in water;, this hinders its
use, e.g., in analytical chemistry.
Data on the structure and physicochemical proper-
ties of solid metal chrysin complexes are scarce [9].
We have prepared solid complexes of Ti(IV), Zr(IV),
The Zr(IV) and Zn(II) complexes undergo endo-
thermic dehydration in the range 293 593 K; the
Table 1. Analytical data for chrysin and its compounds with Ti(IV), Zr(IV), and Zn(II)a
Found, %
Calculated, %
Compound
Color
C
H
Mb
H2O
C
H
Mb
H2O
C15H10O4 (chrysin)
Ti(C15H9O4)4
Zr(C15H9O4)4 8H2O
Zn(C15H9O4)2 2H2O
Beige
Yellow
71.18
68.33
57.47
59.81
3.65
3.51
3.52
3.16
70.85
67.93
57.78
59.45
3.96
3.42
4.21
3.63
4.18
7.80
10.46
4.51
7.21
10.76
10.50
6.50
11.56
5.94
a
b
Derivatographic data.
M is metal.
1070-3632/03/7304-0634$25.00 2003 MAIK Nauka/Interperiodica

SYNTHESIS AND PHYSICOCHEMICAL STUDY OF SOLID COMPLEXES
635
Table 2. Temperatures of thermal decomposition of chrysin and its complexes with Ti(IV), Zr(IV), and Zn(II)a
Final decomposi-
tion product
DTA
DTG
Compound
Chrysin
Ti(C15H9O4)4
Zr(C15H9O4)4 8H2O
Zn(C15H9O4)2 2H2O
T1, K
T
, K
T
, K
T2, K
Tf, K
min
min
578 1095
493 1033
393 1133
593 1183
1095
1033
1133
1183
TiO2
ZrO2
ZnO
293 393
313 593
350
533
353
523
a
(T ) Temperature range of dehydration (endothermic effect); (T ) temperature range of decomposition of the anhydrous compound
1
2
DTA DTG
and combustion of organics to give the final product; (T
, T
) temperatures corresponding to the minimum in the DTA and
min
min
DTG curves; (T ) temperature of formation of the final product.
f
Table 3. Parameters of absorption bandsa of chrysin and its complexes with Ti(IV), Zr(IV), and Zn(II) in methanol;
5
6
6
5
concentrations 3.2 10 , 7.6 10 , 7.6 10 , and 2.1 10 M, respectively; l 1 cm
Chrysin Ti(C15H9O4)4 Zr(C15H9O4)4 8H2O
Zn(C15H9O4)2 2H2O
0
max
0
max
0
max
0
max
31600
37000
40500b
46600
16775
40000
20000
44160
31500
37000
40700b
47400
33260
116240
61120
32000
37300
40700b
47400
52900
132200
66500
32000
37000
40500b
46600
22380
55240
28095
56190
130600
167400
a
1
1
1 b
(
) Band center, cm ; (
) molar extinction coefficient at the band maximum, l mol cm
.
Inflection.
0
max
1
Table 4. Vibration bands (cm ) of the strongest bands in the IR spectra of chrysin and its complexes with Ti(IV), Zr(IV),
and Zn(II)
Chrysin
Ti(C15H9O4)4
Zr(C15H9O4)4 8H2O
Zn(C15H9O4)2 2H2O
Assignmenta
3600 2400
1652
1612
1576
1556
1500
1175
908
3600 2400
1652
1612
1576
1556
1500
1165
908
3600 2400
1654
1613
1577
1555
1499
1356
908
3600 2400
1652
1613
1576
1555
1499
1175
908
OH
C=O
C=C
C H
C H
840
844
843
845
808
808
807
815
a
( ) Stretching, ( ) in-plane bending, and ( ) out-of-plane bending vibrations.
Ti(iV) complex, which is anhydrous, shows no such
effect. At higher temperatures the anhydrous com-
pounds decompose, with burn-out of the organics and
formation of metal oxide. The process yielding TiO2,
ZrO2, and ZnO is complete at 1033, 1133, and
1183 K, respectively.
in methanolic solutions. The electronic absorption
spectrum of chrysin in the range 200 700 nm con-
tains two strong bands (
214 and 270 nm) and a
max
weaker band at 316 nm. It is known that these bands
are due to * transitions in the ligand molecule.
The band positions in the spectra of the metal chrysin
complexes are virtually the same as in the spectrum of
free chrysin.
The electronic absorption spectra of the Ti(IV),
Zr(IV), and Zn(II) chrysin complexes were measured
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 4 2003

636
PUSZ et al.
Table 5. Chemical shifts in the 13C NMR spectra
The intensity of the absorption bands of the com-
plexes is higher compared to the free ligand and regu-
larly increases in the order Zn < Ti < Zr. The in-
creased molar extinction coefficients of the complexes
are apparently due to changes in the electron density
distribution in the benzene and -pyrone rings.
( C, ppm) of chrysin and its solid Zr(IV) complex
Chrysin,
solution
Zr(IV)
chrysin
complex
Assign-
ment
a
Chrysin (
)
in DMSO
The IR spectra of the Ti(IV), Zr(IV), and Zn(II)
chrysin compounds are complex (Table 4). No shift
of the carbonyl absorption band is observed upon
coordination of chrysin with the metals. The other
parts of the spectra of free chrysin and its metal com-
plexes also differ insignificantly.
C2
163.50
105.30
182.00
161.40
99.20
164.76 ( 1.2)
103.17 (+2.1)
181.99
160.90
99.19
164.90
94.48
156.94 (+2.9)
103.17
129.85
164.58
103.22
181.92
160.90
99.38
C3
C4=O
C5 OH
C6
C7 OH
C8
164.50
94.40
164.58
94.36
The solid-state NMR spectra of chrysin and its
Zr(IV) complex (Table 5) virtually coincide.
C9
159.80
103.90
130.80
126.50
129.30
132.16
156.80
103.22
130.01
125.87
130.01
133.77
C10
C1
Our results, even in combination with published
data [10 13], do not allow determination of the coor-
dination mode of chrysin. Available data on com-
plexes of p, d, and f metals with quercetin, morin, and
their sulfo derivatives suggest that the corresponding
ions are bound via four CO groups and five C OH
groups. Analytical (Table 1) and derivatographic
(Table 2) data suggest that chrysin forms characteris-
tic [14] eight-coordinate complexes with Ti(IV) and
Zr(IV) and a four-coordinate complex with Zn(II):
C2
125.94
129.85
133.96 ( 1.8)
C3
C4
a
=
(solution)
(solid state).
EXPERIMENTAL
In physicochemical studies we used a Beckman
DU-640 UV-Vis spectrophotometer (the United
States), an MOM-3427T derivatograph (Hungary),
a Carlo Erba EA-1108 apparatus for elemental analy-
sis (Hungary), a Specord IR-80M spectrophotometer
(Germany), a Bruker MSL-300 NMR spectrometer
(the United States), a Perkin Elmer-3100 atomic
absorption spectrometer (the United States), and a
Radelkis OP-8/1 pH meter (Hungary).
HO
O
O
O
OH
O
O
O
O
O
M
O
In the experiments, we used the following chemi-
cals: TiCl4, density 1.73 g cm ; ZnCl2, analytically
O
O
O
3
HO
pure grade; zinc metal, analytically pure grade;
ZrOCl2 8H2O, pure grade; chrysin, pure grade;
Na2EDTA, analytically pure grade; potassium metal,
analytically pure grade; dimethyl sulfoxide (DMSO),
analytically pure grade; sulfuric acid, 0.05 M; con-
centrated perchloric acid; concentrated hydrochloric
acid; concentrated aqueous ammonia; Xylenol Orange,
1 : 100 mixture with NaCl; methanol, analytically
pure grade; and 96% ethanol, analytically pure grade.
OH
HO
O
O
O
Initial solutions. A 1.0 M Ti(IV) solution was pre-
pared by diluting the required amount of TiCl4 with
double-distilled water. A 0.038 M Zr(IV) solution was
prepared by dissolving ZrOCl2 8H2O in sulfuric acid.
A 0.5 M ZnCl2 solution was prepared by dissolving
ZnCl2 in ethanol. The saturated solution of chrysin
in ethanol was prepared on heating.
Zn
O
O
O
OH
A 0.2 M solution of K in ethanol was prepared by
gradual addition of 0.7820 g of K metal to 100 ml of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 4 2003

SYNTHESIS AND PHYSICOCHEMICAL STUDY OF SOLID COMPLEXES
637
96% ethanol; the resulting solution was filtered. The
reference solution containing 0.0150 M Zn(II) was
prepared by dissolving 1.9613 g of Zn metal in 30 ml
of HCl; the volume was brought to 2.0 l with double-
distilled water.
DTG 1/5, DTA 1/3; and Zn(II) compounds, TG
200 mg, DTG 1/10, and DTA 1/10.
The electronic absorption spectra of Ti(IV), Zr(IV),
and Zn(II) chrysin complexes were taken in methanol
(Table 3). The IR spectra (KBr pellets) were recorded
1
A 0.0150 M solution of Na2EDTA was prepared
by dissolving 11.1672 g of the salt in 0.2 l of double-
distilled water. The solution concentration was deter-
mined by titration with a zinc reference solution in the
presence of Xylenol Orange.
in the range 4000 400 cm . The frequencies of
selected absorption bands in the IR spectra are listed
in Table 4.
The 13C NMR spectra of chrysin and its solid
Zr(IV) complex were recorded at 75.5 MHz. Measure-
ment conditions: rotor diameter 4 mm, frequency
7.4 kHz, contact time 3 s, spectral width 20 kHz.
The chemical shifts were measured relative to the CO
signal of glycine (176.03 ppm) and recalculated rela-
tive to TMS (Table 5).
Synthesis of the complexes. To prepare the Ti(VI)
and Zr(IV) chrysin complexes, solutions of metal salts
in amounts corresponding to the metal-to-ligand ratio
M : L = 1 : 4 were added with heating and stirring
to 200 ml of a saturated aqueous-ethanolic solution of
chrysin. The mixtures were cooled, an ammonia solu-
tion was added to pH 6 7, and the precipitates were
filtered off, washed several times with water and
aqueous ethanol (1 : 1), centrifuged, and dried in air
at room temperature.
REFERENCES
1. Jerzmanowska, Z., Wiad. Chem., 1973, vol. 27, no. 9,
p. 624.
2. Wilska-Jeszka, J., Wiad. Chem., 1959, vol. 13, no. 6,
To prepare the Zn(II) chrysin complex, a reference
solution of ZnCl2 in amount corresponding to the
ratio M : L = 1 : 2 was added with stirring to 300 ml
of a hot saturated solution of chrysin containing a
solution of K in ethanol. The precipitate was centri-
fuged, washed several times with aqueous ethanol
(1 : 1), and dried in air at room temperature.
p. 289.
3. Korkuc, A., Wiad. Chem., 1969, vol. 23, no. 5, p. 345.
4. Nevskaya, E.M. and Nazarenko, V.A., Zh. Anal. Khim.,
1972, vol. 27, no. 8, p. 1699.
5. Kopacz, M., Zesz. Nauk. Politech. Rzeszow, 1989,
vol. 55, no. 4, p. 1.
6. Kopacz, M., Nitka, B., Pusz, J., and Kopacz, S., Zh.
Org. Khim., 1983, vol. 19, no. 8, p. 1681.
Identification of the complexes. The composition
and structure of the complexes were determined by
elemental and thermogravimetric analysis and by
UV-Vis, IR, and NMR spectroscopy.
7. Pusz, J., Kopacz, M., and Kopacz, S., Zh. Neorg.
Khim., 1988, vol. 33, no. 10, p. 2573.
8. Pusz, J., Kopacz, M., and Kopacz, S., Koord. Khim.,
The content of C and H in the complexes was
determined by a standard gravimetric procedure with
an apparatus for elemental analysis.
1990, vol. 16, no. 7, p. 966.
9. Pusz, J. and Nitka, B., Microchem. J., 1997, vol. 56,
p. 373.
10. Pribil, R., Die komplexometrische Titration, Leipzig:
The metal percentage was determined complexo-
metrically (EDTA titration) after decomposition of the
complexes with perchloric acid, gravimetrically (after
combustion at 1193 1213 K), and by atomic spectros-
copy (after decomposition with perchloric acid).
Grundstoffindustrie, 1960.
11. Marby, F.J., Markham, K.R., and Thomas, M.B., The
Systemic Identification of Flavonoids, New York:
Springer, 1970.
12. Porter, L.J. and Markham, K.R., J. Am. Chem. Soc.,
Thermal decomposition of chrysin and its Ti(IV),
Zr(IV), and Zn(II) complexes was studied in the tem-
perature range 293 1273 K. Samples were heated at
1970, vol. 92, no. 2, p. 344.
13. Porter, L.J. and Markham, K.R., J. Am. Chem. Soc.,
1
1970, vol. 92, no. 5, p. 1309.
a rate of 1 deg min in air; the device sensitivity lev-
els were as follows: Ti(IV) compounds, TG 100 mg,
DTG 1/5, DTA 1/10; Zr(IV) compounds, TG 200 mg,
14. Bartecki, A., Chemia pierwiastkow przejsciowych,
Warsaw: Naukowo-Techniczne, 1987.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 4 2003