plate. Then, vanadium tetrafluoride (1 mmol) dissolved in 25 ml of methanol was added into the reaction flask dropwise with constant stirring. The reaction mixture had pH 3. The resulting mixture was refluxed for 2 h and kept overnight with stirring at room temperature. The solvent was removed on a rotary apparatus under reduced pressure. The solid product was recrystallized
in a methanol-«-hexane (1 : 1) mixture. The general chemical reaction is given below:
VF4 + 2RCOOH g XfhaTh; ■ V(RCOO)2F2,
(iii) Overnight stirring
where R = Rx-R6.
CH^Q
H3C CH3
(R1)
CH^tT
a^cHr
(R2)
H3C—N
CH3
(R3)
H3C
CH-CH2
H3C
CHI
CH3
(R5)
Cl
CH—N N-CH2-CH2-°-CH
2
(R6)
C2H5 N.
№
(R4) O
Method 2. Ligands in the form of sodium salt were converted to the corresponding acid by dissolving them in distilled water, and concentrated HCl was added dropwise. White precipitates obtained were washed with distilled water, in dried air, and checked for the melting point. The complexes were synthesized by the method mentioned above. The general chemical reactions are given below:
RCOONa + H2O
HCL,
where R = R7, R8.
RNa + H2O HC'conC 7, 8
RCOOH + NaCl,
ROH + NaCl,
___ CH2-
Q^O
C'
(R7)
CH3CO-CH2—CH
3 2 I
C6H5
(R8)
o—
Table 1. The elemental analysis data and some physical properties of the vanadium(IV) complexes
Compound Empirical formula Mol. weight Yield, % M.p., °C Ohm-1 cm2 mol-1 Contents (calcd/found), %
C H N V**
I VF2C3oH2iAN2 569 70 226-8 0.049 63.2/63.4 4.9/4.7 4.9/5.0 8.95/8.63
II VF2C32H26O6 595 72 * 0.045 64.5/64.1 4.3/4.8
III VF4C30H24O4 575 75 94-6 0.015 62.6/62.1 4.1/4.6 8.60/8.37
IV VF4C34H38O6N6 753 76 224-6 0.262 54.1/53.9 5.0/5.8 11.1/11.7 6.78/6.39
V VF2C26H34O4 499 80 86-8 0.052 62.5/62.9 6.8/6.1 10.20/10.41
VI VF2C42H52O6N4CI6 1010 82 142-6 0.082 49.9/50.4 5.1/4.8 5.5/5.9
VII VF2C28H20O4N2CI4 679 75 162-6 0.199 49.4/49.8 2.9/3.1 4.1/4.5 8.38/8.53
VIII VF2C38H30O8 703 77 170 0.043 64.8/64.1 4.2/4.9 7.25/7.99
* Gel-like state.
** The estimation of vanadium was done by using atomic emission spectroscopy (ICP-AES).
RESULTS AND DISCUSSION
Physical properties. The reaction of vanadium(IV) fluoride with nonsteroidal antiinflammatory drugs in dry methanol at pH 3 resulted in the formation of complexes of general formula VF2L2 (where L are Lx-L8 in complexes I-VIII, respectively). The synthesized complexes were in the crystalline solid/gel-like state, green-colored, and fairly stable at room temperature. They show good solubility in common organic solvents. The molar conductance values of all the synthesized
Table 2. UV-visible spectral data for the vanadium(IV) complexes
Absorption bands (v, cm x)
Compound band I 2E "— 2B2 band II 2B1 — 2B2 band III 2^1 — 2B2 chargetransfer bands
I 12484 16752 28490 35842 44943
II 12658 17530 27777 41841 47619
III 12468 33557 39215
IV 11737 16778 27777 35842 45454
V 12391 16750 27777 36764 45454
VI 13003 25510 36630 42553
VII 12269 17730 27777 35842 45454
VIII 12556 16556 25062 35211 43859
complexes determined in methanol at room temperature suggest the nonelectrolytic nature of the complexes. The elemental analysis data and some physical properties of vanadium(IV) complexes are given in Table 1.
The UV-visible spectra for all the synthesized complexes were recorded in methanol and are shown in Table 2. The vanadium(IV) complexes generally exhibit three bands due to d-d transitions. These bands are not well developed. It seems more probable that the first two transitions lie under the envelope of the band I [9]. Band III is not observed but is thought to be buried beneath the low-energy tail of the strongly intense charge-transfer band [10], and when it is observed that it is generally a shoulder, so that its maximum position is known with least accuracy [11]. All other bands above 30000 cm-1 are charge-transfer in origin.
The assignments of electronic absorption spectral bands of the vanadium (IV) complexes were a matter of controversy [12, 13]. According to ordering of the energy levels (Ballhausen and Gray scheme), band I in a range of 11737-13003 cm-1 results from the B2 —► E transition. Band II in a range of 16556-17730 cm-1 is assigned to the B2 —- B1 transition, and band III in a range of25062-28490 cm-1 is attributed to the B2 —► A1 transition. The shift of the B2 —»- E and B2 —► B1 bands to the red and blue regions, respectively, compared with that of VF4, agrees with carboxylate coordination to the metal center [14, 15]. Other bands above 30000 cm-1 are charge-transfer in origin.
Infrared spectroscopy. The most important features of the infrared spectra of the complexes and corresponding free ligands are shown in Table 3. The presence of various ring vibrations and C-H absorption makes the spectra fairly complicated for complete assignments of individual bands. The important absorption frequencies are v(O-H), v(N-H), v(C=O), vs(COO), vs(COO), v(V-O), and v(V-F). The values assigned to these bands are in accordance with the values reported in literature [16, 17]. The complexation of
Table 3. Infrared spectral data (cm *) for ligands and their vanadium(IV) complexes
Compound v(O-H) v(N H) v(COO) Av v(V-O) v(V-F) v(C=O)
asym. sym.
L1 3415 3313 1652 1329 323
I 3310 1577 1385 192 569 475
L2 3439 1697 1379 318 1730
II 1653 1449 204 595 484 1723
L3 3405 1702 1383 319
III 1692 1478 130 575 471
L4 3440 1630 1269 361 1717
IV 1577 1385 192 528 463 1715
L5 3426 1719 1420 299
V 1710 1510 200 586 421
L6 3415 1741 1434 307
VI 1624 1425 199 510 476
L7 3415 3324 1724 1420 304
VII 3324 1693 1504 189 580 400
L8 3415 1707
VIII 504 441 1707
Table 4. Antibacterial activity data for vanadium(IV) complexes
Zone of inhibition, mm
Name of bacteria* I II III IV V VI VII VIII standard drug**
Escherichia coli 30 25 25 25 25 25 18 20 30
Bacillus subtilis 28 24 24 30 25 25 15 20 33
Shigella flexenari 25 24 24 25 20 25 20 20 27
Staphylococcus aureus 25 25 25 25 20 22 20 18 33
Pseudomonas aeruginosa 10 20 20 25 20 20 20 22 24
Salmonella typhi 20 20 20 25 20 15 20 20 25
* Concentration of sample is 3 mg/ml of DMSO. ** Imipenum is 10 ^g/disc.
vanadium (IV) fluoride with the ligands is confirmed by the disappearance of the v(O-H) band in the spectra of the complexes occurring at 3440-3405 cm-1, which is characteristic of carboxylic acids. The complexation of vanadium with an oxygen donor ligand is also confirmed by the appearance of the v(V-O) band in the range 595-504 cm-1. The v(V-F) band appeared in the range 484-400 cm-1. The v(COO) stretching vibrations are important to predict the bonding mode of the ligand. The peak for v(COO) in the region 1741-1630 cm-1 for carboxylic acids was shifted to lower-frequency side showing complexation. The lowering of vas(COO) and rise of vs(COO) for the carboxylate group show the bi-dentate nature of the ligand in the complexes [18]. The difference Av of vas(COO) and vs(COO) stretching values for complexes I-VII fall in the range 204-130 cm-1 and shows that the ligands act as bidentate. The strong
bands observed at 1707-1730 cm-1 can be assigned to v(C=O) of other than carboxylate group ligands L2, L4, and L8, which remains practically unchanged after com-plexation. The overall IR spectral evidence suggests that all the ligands act as bidentate and are coordinated through the carboxylic oxygen atoms, forming an octahedral structure.
Thermal analyses data confirms the bidentate nature of ligand in vanadium (IV) complexes in solid state too. The thermocomposition data can be directly received at author Saqip Ali - e-mail: drsa54@yahoo.com
Biological activity. All the synthesized complexes were estimated for their microbial toxicity against a set of bacterial and fungal strains. The antibacterial activity of the complexes was tested using the agar well-diffusion method [19], and the results are given in Table 4.
Table 5. Antifungal activity*** data for the vanadium(IV) complexes
Inhibition, %
Name of fungus I II III IV V VI VII VIII standard drug MIC***, M£/ml
Trichophyton longifusus 40 40 45 35 35 65 40 70 Miconazole 70
Candida albicans 60 40 60 75 75 75 75 75 Miconazole 110.8
Aspergillus flavus 0 0 0 0 0 0 0 0 Amphotericum B 20
Microsporum canis 60 0 40 0 0 0 0 30 Miconazole 98.4
Fusarium solani 55 0 30 40 40 50 40 50 Miconazole 73.25
Candida glaberata 65 60 65 60 75 70 75 75 Miconazole 110.8
* Incubation period 7 days. ** Incubation temp. 27°C. *** Concentration of sample 200 |lg/ml of DMSO.
The results show that all the complexes have significant antibacterial activity.
The antifungal tests were carried out by using the agar tube dilution protocol method [20]. The antifungal results of the synthesized complexes are given in Table 5. All the complexes showed significant antifungal activity against
Trichophyton longifusus, Candida albicans, Fusarium solani, and Candida glaberata. The complexes show moderate activity against Microsporum canis. All the complexes are inactive against Aspergillus flavus.
So by interpreting the spectroscopic results, we proposed the octahedral geometry for synthesized complexes I-VIII:
F
^O. I /O. r-CK; ^C-R
| O
F
ACKNOWLEDGMENT
This work was supported by the Higher Education Commission (Islamabad), project no. 20-130/Acad (R)/03-415.
REFERENCES
1. Thompson, K.H., McNeill, J.H., and Orvig, C. Chem. Rev., 1991, vol. 99, p. 2561.
2. Vanadium Compounds, Their Biochemistry and Therapeutic Applications, Tracy, A.S., Crans, D.C., Eds., ACS Symponsium Series 711, Washington: ACS Publishers, 1998.
3. Kiss, T., Buglyo, P., Micera, G., et al., Dalton Trans., 1993, no. 12. p. 1849.
4. Kiss, T., Buglyó, P., Senna, D., Micera, G., DeCock, P., and Dewaele, D., Inorg. Chim. Acta, 1995, vol. 239, no. 1-2, p. 145.
5. Gilman, A.G., (ed.), Las Bases Farmacológicas de Ia Therapeutica, Vol. 2, McGraw-Hill Intermericanna, Méjico, 1996.
6. Sorenson, J.R., J. Med. Chem, 1976, vol. 1
Для дальнейшего прочтения статьи необходимо приобрести полный текст. Статьи высылаются в формате PDF на указанную при оплате почту. Время доставки составляет менее 10 минут. Стоимость одной статьи — 150 рублей.