Synthesis, Spectroscopic and Thermal Characterization of New ...

Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry, 35:483–490, 2005 Copyright # 2005 Taylor & Francis, Inc. ISSN: 0094-5714 print/1532-2440 online DOI: 10.1081/SIM-200067043

Synthesis, Spectroscopic and Thermal Characterization of New Sulfasalazine Metal Complexes Ahmed A. Soliman Department of Chemistry, Faculty of Science, UAE University, Al-Ain, UAE

Gehad G. Mohamed, Wafaa M. Hosny, and Mohamed A. El-Mawgood Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt

The complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) with sulfasalazine (H3L) were studied in the solution and in the solid states. The stability constants of the metal complexes were calculated pH-metrically. The solid products were isolated and characterized by elemental, i.r, molar conductance, magnetic moment, diffused reflectance and thermal analyses. The mono- and biscomplexes were isolated with the formula [M(L)(H2O)n]mH2O and [M(HL)2(H2O)n]mH2O, respectively, where H2L is sulfasalazine, n 5 0,2 or 3, m 5 0,1,2,3 or 4 and M 5 Co, Ni, Cu, Zn and Cd. The mono- and bis-iron(III) complexes were found to have the formulae [M(L)Cl(H2O)3].2H2O and [M(HL)2Cl(H2O)].H2O, respectively. Keywords

metal complexes, sulfasalazine

INTRODUCTION Sulfa drugs had attracted special attention from their therapeutic importance as they were used against a wide spectrum of bacterial ailments (Clyson et al., 1967; Beerlev et al., 1960; Tarbini, 1967; Hoffman la Roche Co., 1967; Schmidt, 1969; Tarbini, 1967; Vaichulis, 1966; Shoukry and Shoukry, 1991). Also, some sulfa drugs were used in the treatment of cancer, malaria, leprosy and tuberculosis (Hoffman La Roche Co., 1967). Although the complexes of some sulfa drugs have been investigated in the solid state, relatively little is reported about their solution chemistry, in particular mixedligand complexes (Shoukry and Shoukry, 1991; Hosny, 1999). The formation and characterization of binary and mixed-ligand complexes involving iminodiacetic acid and sulfa drugs such as sulfadiazine and sulfadiamidine were

Received 3 December 2004; accepted 3 April 2005. Address correspondence to Ahmed A. Soliman, Department of Chemistry, Faculty of Science, UAE University, P.O. Box 17551, Al-Ain, UAE. E-mail: [email protected]

investigated (Shoukry and Shoukry, 1991; Hosny, 1999; Hosny, 1997). Binary and ternary complexes of transition metals are commonly found in biological media and might play important roles in process as diverse as the catalytic interaction of viruses with bacterial cell walls, the transport and storage of oxygen, etc. (Hosny, 1997). The present study was undertaken to throw more light on the chelation behavior of sulfasalazine (H3L) towards some d-block elements, which may help in better understanding of the mode of chelation of sulfasalazine (Structure 1). For this purpose, the complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) with sulfasalazine are studied in solution and in the solid state. The stability constants of the complexes were evaluated and the structures of the isolated solid complexes are elucidated using IR, magnetic susceptibility, solid reflectance, mass spectral measurements and thermogravimetric analysis. EXPERIMENTAL All chemicals used throughout the work were of the highest purity available. They included sulfasalazine (Sigma), cobalt acetate tetrahydrate (BDH), copper acetate monohydrate (Merck), zinc acetate dihydrate (BDH), nickle chloride hexahydrate (BDH), cadmium acetate (Ubichem), ferric chloride hexahydrate (Ubichem), potassium hydroxide (BDH), sodium chloride (Merck), hydrochloric acid (Merck), EDTAdisodium salt (Sigma), zinc oxide (Analar), ammonium chloride (Merck) and ammonium hydroxide (Merck). The organic solvents used included absolute ethyl alcohol (BDH) and diethyl ether (Aldrich). Elemental analyses (C, H, N) were performed in the Microanalytical Center at Cairo University, and were repeated twice. The i.r. spectra were recorded as KBr discs using 1430 Perkin-Elmer FT-IR spectrometer in the wave number region 4000 –400 cm21. The molar magnetic susceptibilites of the powdered samples were measured using the

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A. A. SOLIMAN ET AL.

ionized. In addition, the sulfonamide NH (pKa 11.1) does not participate in bonding due to structure complication. Hence, sulfasalazine can be symbolized as HL2, structure 2.

STRUCTURE 1. H3L.

Faraday method (magnetic susceptibility balance –Sherwood were made by Pascal’s constant using Hg[Co (SCN)4] as calibrant). Thermogravimetric analysis (TGA) of the complexes was carried out in a dynamic nitrogen atmosphere (20 ml min21) with a heating rate of 108C min21 using a Shimadzu TGA-50H analyzer. The diffused reflectance spectra were recorded using a Shimadzu 3101pc spectrophotometer; the spectra were recorded as BaSO4 disks. The molar conductance measurements of the complexes were carried out in DMF using a Genway 4200 conductivity meter. The pH-metric titrations were carried out in an alcohol-water mixture (50% v/v) at 258C and ionic strength of 0.1 M (achieved by the addition of appropriate amounts of 1 M NaCl) using Genway 3020 pH/T meter type. The pH meter was calibrated before each titration using standard buffers of pH ¼ 4, 7 and 9. The ionization constants of the investigated ligand and the stability constants of its metal chelates with Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) were determined using the technique of Sarin and Munshi (1972) and Irving and Rossotti (1953; 1954). Metal contents of the complexes were determined by titration against standard EDTA after complete decomposition of the complexes with aqua regia in 50 mL digestion flasks. Preparation of Solid Complexes of Sulfasalazine Metal complexes were synthesized by the addition of a hot ethanolic solution (608C) of the appropriate metal chloride, nitrate or acetate (25 mL, 0.1 mmol) to a hot ammoniacal ethanolic solution of sulfasalazine (25 mL, 0.1 mmol) for the monocomplexes (1 : 1) or (25 mL, 0.2 mmol) for the biscomplexes (1 : 2). The mixture was stirred for 1 hour and left in the refrigerator overnight whereby the complexes were precipitated. The isolated complexes were filtered, washed thoroughly with ethanol and then with diethyl ether. The solid complexes were dried in a vacuum desiccator over anhydrous calcium chloride. The results of elemental analysis are in good agreement with the calculated ones for the proposed structures. Sulfasalazine has four ionization constants as reported (Nygard et al., 1966); 0.62, 2.9, 8.7 and 11.1, corresponding to the deprotonation of the protonated pyridine nitrogen, carboxylic OH, phenolic OH and sulfonamide hydrogen, respectively. The free carboxylic form of sulfasalazine is insoluble in water or ethanol so that ammoniacal ethanolic solutions were used (pH ¼ 6.0) in which the carboxylic acid group is

RESULTS AND DISCUSSION The results of elemental analyses (Tables 1 and 2) were found to be in good agreement with the suggested formulae of the complexes. The stability constants (Table 3) of the monocomplexes (1:1), logK1, were found to be in the order of Ni(II), Co(II), Zn(II), Cd(II), Cu(II), Fe(III). This is in accordance with the increasing charge on the metal ions, and hence the increasing of their coordination affinities. On the other hand, the order of the stability constants of the biscomplexes (1 : 2), logK2 were in the order of Co(II), Cd(II), Zn(II), Cu(II), Ni(II), Fe(III), which more or less follows the same trend as those of monocomplexes. The free energy changes for the formation of the mono- and biscomplexes at 258C were of high negative values, which reflect the spontaneous nature of the complex formation reactions. IR Spectra of the Metal Complexes The IR data are shown in Tables 4 and 5. The bands were assigned on the basis of a careful comparison of the spectra of the complexes with that of the free ligand. The IR spectrum of sulfasalazine showed a medium broad band at 3438 cm21, which was attributed to the phenolic OH and carboxylic OH groups. As the ammonium salt of sulfasalazine is used in the preparation of complexes, the stretching vibration of the carboxylic OH is no longer to be considered. In addition, the existence of water of hydration and/or water of coordination in the spectra of the complexes rendered it difficult to get conclusion from the changes expected to the vibration of the phenolic OH group. The shift of the n(C–O) of the phenolic group, from 1281 cm21 in the free ligand to 1268– 1258 cm21 in the complexes indicates the participation of the phenolic group in complex formation (Soliman and Linert, 1999). The phenolic OH was found deprotonated in the monocomplexes, which was apparent from the absence of the d (OH) in-plane bending (1394 cm21 in the free HL2 ligand (Soliman and Linert, 1999). On the other hand, this band was found, but shifted in the spectra of

STRUCTURE 2. HL2((R ¼ –N2PhSO2NHPy); Py ¼ pyridine).

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CHARACTERIZATION OF NEW SULFASALAZINE COMPLEXES

TABLE 1 Analytical and physical data of the 1 : 1(M : L) monocomplexes of sulfasalazine Molar mass (MS m/z)

Compound [Fe(L) Cl (H2O)3] . 2H2O C18H22N4O10SClFe [Co(L) (H2O)2] . H2O C18H18N4O8SCo [Ni(L)(H2O)2] . 4H2O C18H24N4O11SNi [Cu (L) (H2O)2] . 3H2O C18H22N4O10Scu [Zn(L) (H2O)2] . H2O C18H18N4O8SZn [Cd(L) (H2O)2] . 4H2O C18H24N4O11SCd

576.8 (577.0) 508.9 (509.0) 535.0 (549.5) 549.5 (549.5) 580.0 (515.3) 580.0 (616.4)

Color (% yield) Yellow (85.0) Dark brown (70.0) Yellow (72.0) Green (82.0) Yellow (76.0) Yellow (82.0)

Found (calcd.) % C

H

N

M

37.89 (37.44) 41.94 (42.44) 38.62 (38.39) 38.92 (39.31) 41.41 (41.91) 35.45 (35.04)

3.48 (3.81) 3.20 (3.54) 4.11 (4.26) 4.10 (4.00) 3.20 (3.49) 3.69 (3.89)

10.04 (9.71) 10.65 (11.0) 9.44 (9.95) 9.86 (10.19) 10.50 (10.86) 9.13 (9.08)

9.89 (9.68) 11.33 (11.57) 10.28 (10.41) 10.99 (11.55) 12.28 (12.67) 17.94 (18.23)

the biscomplexes, which indicates that the phenolic OH participates in coordination without proton displacement. The presence of water molecules in the complexes is ascertained by the appearance of n(OH) as a broad band within the range 3500– 3000 cm21, and g(OH) in the range 965 –914 cm21. The other bending vibration of the water molecule d(OH) is usually around 1600 cm21, which always interfers with the skeleton vibration of the benzene ring (C¼C vibration). The spectrum of the sulfasalazine ligand showed sharp bands at 1618 and 1427 cm21 assigned to asymmetric and symmetric stretching vibration of the carboxylate moiety, respectively. These two bands are either slightly shifted to lower frequencies or decreased markedly in intensity, indicating the participation

meff (B. M.)

Lm V21 cm2 mol21

6.5

30.0

5.1

17.5

3.5

low range

2.2

6.3

Diam.

4.9

Diam.

7.2

of the carboxylate group in complex formation (Sandhu and Verma, 1987). The other ligand vibrations (O¼S¼O, – N¼N –) remained unchanged or slightly shifted, which may be attributed to the electronic density changes on these groups after complex formation (Santi et al., 1993). The participation of the phenolic and carboxylic group was also confirmed by the appearance of new bands in the complexes in the 472– 432 cm21 regions, which were assigned to the n(M – O) stretching vibrations (Mohamed, 2001). Molar Conductivity Measurements The molar conductivity values for all complexes (Tables 1 and 2) were found to be in the range

TABLE 2 Analytical and physical data of the 1 : 2 (M : L) biscomplexes of sulfasalazine Complex [Fe(HL)2 Cl H2O] . H2O C36H30N8O12S2 ClFe [Co(HL)2 (H2O)2] C36H30N8O12S2Co [Ni(HL)2 (H2O)2] . 2H2O C36H34N8O14S2Ni [Cu (HL)2 (H2O)2] . 2H2O C36H34N8O14S2Cu [Zn(HL)2] . 4H2O C36H34N8O14 S2Zn [Cd(HL)2] . 6H2O C36H38N8O16S2Cd

Molar mass 920.8 (921.2) 888.9 (890.2) 924.6 (922.5) 929.5 (929.0) 931.3 (932.1) 1014.4 (1012.5)

Color (% yield) Dark brown (70.0) Yellow (72.0) Yellow (75.0) Green (82.0) Yellow (76.0) Yellow (82.0)

Found (calcd.) % C

H

N

M

46.54 (46.91) 48.11 (48.59) 46.85 (46.72) 46.10 (46.47) 45.92 (46.38) 42.10 (42.59)

3.66 (3.25) 3.58 (3.37) 3.95 (3.68) 3.55 (3.66) 4.07 (3.65) 3.80 (3.75)

12.47 (12.16) 12.92 (12.59) 11.93 (12.11) 12.06 (12.04) 11.90 (12.02) 10.93 (11.04)

5.87 (6.05) 6.98 (6.63) 6.33 (6.37) 6.81 (6.83) 6.87 (7.01) 10.89 (11.08)

meff (B.M.)

Lm V21 cm2 mol21

6.0

2.6

4.9

7.8

3.7

7.0

2.45

18.2

Diam.

6.2

Diam.

6.4

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TABLE 3 Formation constants of sulfasalazine complexes Metal ion

LogK1

LogK2

2DG1 kJmol21

2DG2 kJmol21

Fe(III) Co(II) Ni(II) Cu(II) Zn(II) Cd(II)

17.98 5.50 5.07 9.30 7.42 8.13

16.65 4.82 8.81 8.20 6.51 6.12

100.44 30.73 28.32 51.95 41.45 45.42

93.01 26.93 49.22 45.81 36.37 34.19

2.60– 30.0 V21 cm2 mol21. These relatively low values indicate the non-electrolytic nature of these complexes (Filo et al., 1987). The neutrality of the complexes can be accounted for by both the carboxylate and the deprotonated phenolic OH groups in the monocomplexes and the carboxylate in the biscomplexes. Magnetic Susceptibility Measurements The magnetic moment values are calculated and reported in Tables 1 and 2. [Fe(HL)Cl(H2O)3]2H2O and [Fe(HL)2 (H2O)Cl].H2O complexes have meff values of 6.5 and 6.05 B.M., which assumes a high spin octahedral geometry (Hay et al., 2003). [Co(L)(H2O)2]H2O monocomplex has magnetic moment of 5.10 B.M., which is in agreement with the values for high tetrahedral Co (II) complexes (Masoud et al., 2004). [Co(HL)2(H2O)2].2H2O biscomplex has meff. of 4.91 B.M., which assumes a high spin octahedral geometry (Cotton and Wilkinson, 1980). The high magnetic moment value may arise from spin – spin coupling and/or crystal distortion. [Ni(HL)2(H2O)2]2H2O biscomplex has meff of 3.66 B.M., which suggests an octahedral geometry (Manonmani et al., 2001) while [Ni(L)(H2O)2]4H2O monocomplex has meff of 3.51 B.M., which is consistent with the tetrahedral geometry with an orbital contribution to the magnetic moment (Moustafa, 1997). [Cu(L)(H2O)2]. 2H2O monocomplex has meff ¼ 2.48 B.M., assuming a distorted octahedral structure

(Cotton and Wilkinson, 1980). The meff of [Cu(HL)2(H2O)2]. 2H2O monocomplex is 2.1 B.M., which assumes a tetrahedral geometry for this complex (Cotton and Wilkinson, 1980). Thermogravimetric Studies The iron monocomplex [Fe(L)Cl(H2O)3]2H2O was thermally decomposed in three successive decomposition steps within the temperature range 50– 6608C. The first two decomposition steps with an estimated mass loss of 18.16% within the temperature range 50– 3108C may be attributed to the liberation of two hydrated, two coordinated water molecules and the chlorine atom (calcd. mass loss ¼ 18.61%). The energies of activation were 69.0 and 55.0 kJmol21 for the first and second steps, respectively. The third step found within the temperature range 310– 6608C with an estimated mass loss of 69.08% (calcd. mass loss 68.40%), which is reasonably accounted for by the removal of one coordinated water molecule along with the decomposition of the ligand molecule ending with a final oxide residue of 1/2Fe2O3 and associated with activation energy of 114.0 kJmol21. The total estimated mass loss was 87.24% (total calcd. mass loss ¼ 87.00%). The iron biscomplex with the general formula [Fe(HL)2 (H2O)Cl].H2O is thermally decomposed in three successive decomposition steps. The first estimated mass loss of 5.55% within the temperature range 30 –1508C may be attributed

TABLE 4 Selected IR data for the sulfasalazine and its monocomplexes Compound Ligand Fe(1:1) Co(1:1) Ni(1:1) Cu(1:1) Zn(1:1) Cd(1:1)

n(C –O)

d(OH)

nasy.(COO)

1281 s 1259 s 1261 s 1260 s 1267 s 1261 s 1258 s

1394 s 1394 s 1391 s 1398 s 1392 s 1392 s 1390 s

1618 s 1616 s 1599 s 1600 sh 1603 s 1605 s 1593 s

nsym.(COO)

n(N55N)

nasy.(SO2)

1427 s 1425 s 1420 s 1420 s 1421 s 1435 s 1433 s

1585 s — 1560 sm disapp. 1560 s 1562 s 1560 sm

1358 s 1358 s 1360 s 1354 s 1350 sh 1350 sh 1350 s

nsym.(SO2) 1173 s 1175 s 1175 s 1174 s 1176 s 1175 s 1170 sm

n(M – O) — 440 m 449 m 440 m 460 s 450 s 472 s

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TABLE 5 Selected IR data for sulfasalazine and its 1:2 biscomplexes Compound Ligand Fe(1:2) Co(1:2) Ni(1:2) Cu(1:2) Zn(1:2) Cd(1:2)

n(C– O)

d(OH)

nasy.(COO)

nsym.(COO)

1281 s 1278 s 1261 s 1269 s 1271 s 1267 s 1259 s

1394 s 1394 s 1391 s 1387 s 1392 s 1387 s 1390 s

1618 s 1618 s 1599 s 1597 s 1601 s 1599 s 1600 s

1427 s 1427 s 1418 s 1433 m 1423 s 1435 m 1429 s

n(N55N)

nasy.(SO2)

1585 s 1589 s 1560 m 1533 s 1562 m 1531 s 1560 w

1358 s 1358 s 1360 vs 1352 s 1360 s 1356 s 1352 w

nsym.(SO2)

n(M –O)

1173 s 1173 s 1175 s 1175 s 1173 s 1175 s 1170 s

— 432 m 448 m 432 m 430 s 450 s 450 s

s ¼ strong, sh ¼ shoulder, m ¼ medium, w ¼ weak and vs ¼ very strong.

to the liberation of one hydrated water molecule and the chlorine atom (calcd. mass loss ¼ 5.82%). The energy of activation of this step is 69.44 kJmol21. The second and third steps occur within the temperature range 150– 8458C with an estimated mass loss 85.34% (calcd. mass loss 85.70%) are reasonably accounted for by the decomposition of one coordinated water molecule and two ligand molecules leaving 1/2Fe2O3 residue with an activation energies of 136.0 and 157.0 kJmol21. The total estimated mass loss was 90.69% (total calcd. mass loss ¼ 91.52%). The cobalt (II) monocomplex [Co(L)(H2O)2]H2O, was thermally decomposed in two successive steps. The first estimated mass loss of 10.25% within the temperature range 30– 2158C, may be attributed to the liberation of one hydrated and two coordinated water molecules (calcd. mass loss ¼ 10.63%). The activation energy of this step is 53.0 kJmol21. The second step occurred within the temperature range 215 – 8008C with an estimated mass loss 73.08% (calcd. mass loss of 73.23%), which is accounted for by the decomposition of ligand molecule leaving 1/2 Co2O3 residue with an activation energy of 108.0 kJmol21. The thermogram of cobalt biscomplex, [Co(HL)2(H2O)2]. 2H2O, gave a decomposition pattern of four stages. The first estimated mass loss of 4.12% occurs within the temperature range 25– 1308C and corresponds to the loss of two hydrated water molecules (calcd. mass loss ¼ 4.05%) with an activation energy of 44.82 kJmol21. The subsequent steps within the temperature range 150 – 7508C with an estimated mass loss of 86.95% (calcd. mass loss ¼ 87.22%) may reasonably account for the loss of two ligand molecules leaving 1/2Co2O3 residue with a total activation energy of 401 kJmol21. The total estimated mass loss is 90.49% (total calcd. mass loss ¼ 89.76%). The TG curve of the Ni(II) monocomplex showed that [Ni(L)(H2O)2]4H2O decomposed in five close steps. The first estimated mass loss of 19.06% within the temperature range 30– 1108C (calcd. mass loss 19.18%) may be attributed to the loss of four molecules of hydrated, and two molecules of coordinated, water. The energy of activation of this step is

47 kJmol21. The remaining decomposition steps occur within the temperature range 110– 6608C with an estimated mass loss of 68.0% (calcd. mass loss ¼ 67.50%) that correspond to the loss of ligand molecules leaving NiO residue with activation energies of 135, 131, 106 and 110 kJmol21 for the 2nd, 3rd, 4th and 5th steps, respectively. The Ni(II) biscomplex, [Ni(HL)2(H2O)2]2H2O, decomposes in four steps. The first estimated mass loss of 8.18% within the temperature range 20– 1308C (calcd. mass loss 7.78%) may be attributed to the loss of two hydrated and two coordinated water molecules. The energy of activation of this step is 92 kJmol21. The remaining steps occur within the temperature range 130– 6508C with an estimated mass loss of 83% (calcd. mass loss ¼ 84.10%), which may correspond to the loss of two ligand molecules leaving NiO residue with activation energy of 85 kJmol21. The total estimated mass loss is 91.18% (total calcd. mass loss ¼ 91.88%). [Cu(L)(H2O)2] . 2H2O was thermally decomposed in two successive decomposition steps. The first estimated mass loss of 6.70% within the temperature range 25 –1108C may be attributed to the liberation of two molecules of hydrated water (calcd. mass loss 6.77%). The energy of activation of this step is 67.00 kJmol21. The second step occurs within the temperature range 110– 5758C with an estimated mass loss of 78.34% (calcd. mass loss 78.27%) and activation energy of 119.0 kJmol21, which corresponds to the loss of two coordinated water molecules, and ligand molecules leaving CuO residue with a total estimated mass loss of 86.57% (total calcd. mass loss ¼ 88.00%). [Cu(HL)2(H2O)2].2H2O was thermally decomposed in three successive steps. The first estimated mass loss of 5.63% within the temperature range 30– 2258C may reasonably be attributed to the liberation of two molecules of hydrated water and one molecules of coordinated water (calcd. mass loss ¼ 5.81%). The energy of activation of this step is 44.32 kJmol21. The second and third steps occur within the temperature range 225 –8008C with an estimated mass loss of 85.23% (calcd. mass loss ¼ 85.64%) and activation energies of 96.0 and 128.0 kJmol21, which correspond to the loss of one

488


coordinated water molecule and two ligand molecules leaving metal oxide residue (CuO), with a total estimated mass loss of 90.86% (total calcd. mass loss ¼ 91.44%). Zinc (II) complex [Zn(L)(H2O)2]H2O, was thermally decomposed in three successive steps. The first estimated mass loss of 3.85% within the temperature range 35 – 1158C may be attributed to the liberation of one hydrated water molecule (calcd. mass loss 3.49%). The energy of activation of this step is 50.02 kJmol21. The second and third steps occur within the temperature range 280– 7808C with an estimated mass loss of 80.24% (calcd. mass loss ¼ 80.69%) and activation energies of 112 and 114 kJmol21, and are accounted for by the decomposition of two coordinated water and ligand molecules leaving ZnO as a residue. The total estimated mass loss is 84.89% (total calcd. mass loss ¼ 84.18%). The thermogram of zinc biscomplex, [Zn(HL)2(H2O)2]. 2H2O, showed a decomposition pattern of five stages. The first and second steps with estimated mass loss of 7.35% found within the temperature range 25 – 2008C corresponding

to the loss of two hydrated and two coordinated water molecules (calcd. mass loss ¼ 7.73%). The activation energies of these two dehydration steps are 45.79 and 89.90 kJmol21, respectively. The remaining decomposition steps occurred within the temperature range 250– 7508C with an estimated mass loss of 83.65%, and was attributed to loss of two ligand molecules leaving ZnO as a residue (calcd. mass loss ¼ 83.57%). The sum of the activation energies for the last three decomposition steps is 566.55 kJmol21. The total estimated mass loss is 91.18% (total calcd. mass loss ¼ 91.30%). The TG curve of the Cd(II) monocomplex [Cd(L)(H2O)2] . 2H2O, indicated that the complex thermally decomposed in four steps. The first estimated mass loss of 5.77% within the temperature range 25– 1408C (calcd. mass loss 6.21%) may be attributed to loss of two molecules of hydrated water. The energy of activation of this step is 33.49 kJmol21. The second step found in the temperature range 140 –355 with an estimated weight loss of 6.00%

TABLE 6 Band positions (n, cm21) and d-d transitions of sulfasalazine complexes (1:1 and 1:2) Band position; cm21 1023 Complex [Fe(SSZ)Cl(H2O)3]H2O

Co(II)

1:1

1:2

21.50 17.57

21.10 17.42

12.12 17.45 11.43

12.50

Cu(II)

— — — 22.88 14.22 15.87

6

Geometry

A1 g ! T2 g(G) A1 g ! 5T1 g

Octahedral

A2(F) ! 4T1(F) A2(F) ! 4T2(P) 4 A2(F) ! 4T2(F) 4 T1 g(F) ! 4T2 g(P) 4 T1 g(F) ! 4E2 g(F) 4 T1 g(F) ! 4T2 g(F) L ! M CT

Tetrahedral

6

4 4

22.99 13.99 12.53 27.17 Ni(II)

d-d transition

19.19 15.82 11.63 — — —

3

A2 g ! 3T1 g (P) A2 g ! 3T1 g (F) 3 A 2 g ! 3T2 g 1 A1 g ! 1B1 g 1 A1 g ! 1A2 g 3 T1(F) ! 3T1(P) 2

16.45

Octahedral

3

2

16.03 13.19 17.51 27.03

Octahedral

Eg ! 2T2 g B1 g ! 2A1 g

L ! M CT B1 g ! 2B2 g 2 B 1 g ! 2Eg 2 B1 g ! 2A1 g

Tetrahedral

Square planar

2

Octahedral


(calcd. mass loss 6.21%) and activation energy of 92.91 kJmol21 is due to the removal of two coordinated water molecules. The last two steps occur within the temperature range 355–9008C with an estimated mass loss 65.96% (calcd. mass loss 65.52%) and activation energies of 204.15 and 161.25 kJmol21, which correspond to the loss of ligand molecule leaving metal oxide residue (CdO) with a total estimated mass loss of 77.73% (total calcd. mass loss 77.94%). Cadmium biscomplex [Cd(HL)2(H2O)2] . 4H2O decomposition took place in four steps. The first and second estimated mass losses of 10.96% may be accounted for by the loss of four hydrated and two coordinated water molecules (calcd. mass loss 10.65%) within the temperature range 30 – 2358C. The activation energies of these dehydration steps are 33.99 and 104.85 kJmol21. This is followed by two thermal decomposition steps within the temperature range 235– 8158C with an estimated mass loss of 77.10% (calcd. mass loss 76.73%) and activation energies of 90.75 and 93.81 kJmol21, which are due to the complete decomposition

489

of the two ligand molecules leaving CdO as residue. The total estimated mass loss is found to be 88.06% (total calcd. mass loss ¼ 87.38%).

Diffused Reflectance Measurements From the diffuse reflectance spectra (Table 6), it is observed that the 1 : 1 and 1 : 2 Fe(III)-complexes exhibit a band at (21.51 – 21.10) 103 cm21, which may be assigned to the 6 A1 g ! T2 g(G) transition in octahedral geometry of the complexes (Moustafa, 1997). The 6A1 g ! 5T1 g transition appears to be split into two bands at (12.12 – 12.50) 1023 cm21 and (17.57 – 17.42) 103 cm21. Three spin allowed transition bands,4A2 (F) ! 4T2 (F) (n1); 4 A2 (F) ! 4T1 (F) (n2) and 4A2 (F) ! 4T1 (P) (n3) are expected for tetrahedral symmetry of Co(II)(1 : 1)complex. In the present case, only two bands at 11.43 1023 cm21 and 17.45 103 cm21 have been observed in the diffuse reflectance spectrum of Co(II) 1 : 1 complex, which is assigned to n2 and n3,

SCH. 1. Structures of complexes (I–V) (water of hydration is not included).

490


respectively, as n1 occurs in the range 3000– 5000 cm21 (Kapahi et al., 1978). For Co(II) (1 : 2) complex, the reflectance spectrum shows three bands at 12.53 103 cm21, 13.99 103 cm21 and 22.99 103 cm21, which are assigned to 4T1 g(F) ! 4T2 g(F), 4T1 g(F) ! 4E2 g(F) and 4T1 g(F) ! 4T2 g(P) transitions, respectively, assuming an octahedral geometry for Co(II)(1 : 2) complex. The band at 27.17 103 cm21 refers to ligand to metal charge transfer (LMCT) (Cotton and Wilkinson, 1980). The 1 : 1 Ni(II) complex exhibits medium intensity broad bands at 14.22 103 cm21 and 22.88 103 cm21, attributed to the 1A1 g ! 1A2 g and 1A1 g ! 1B1 g transitions, respectively (Iskander et al., 2000). The observed band in the region 15.87 103 cm21; attributed to the 3T1(F) ! 3T1(P), reveals that Ni(II) has tetrahedral configuration (Badiger et al., 1995). The electronic spectrum of the 1 : 2 Ni(II) complex displays three bands in the solid reflectance spectra as follows: 11.63 103 cm21; 3A2 g ! 3T2 g (n1), 15.82 103 cm21; 3A2 g ! 3T1 g (F) (n2) and 19.19 103 cm21; 3A2 g ! 3T1 g (P)(n3). This indicates octahedral geometry of the 1 : 2 Ni complex (Velusamy et al., 1998; Ali et al., 1997). The spectrum of the 1 : 1 Cu –complex shows a broad band at 16.03 103 cm – 1 assigned to 2Eg ! 2T2 g transition and broad band at 13.19 103 cm – 1, which is assigned to 2B1 g ! 2A1 g, as well as a shoulder band at 17.51 103 cm21 characteristic of a square planar geometry for Cu-complex with dx22y2 ground state (Iskander et al., 2000; Reddy and Reddy, 2000). In addition, a moderately intense peak observed at 27.03 103 cm – 1 is due to LMCT (Manonmani et al., 2000). The reflectance spectrum of the 1 : 2 Cu-complex consists of a broad and low intensity shoulder band at 16.45 103 cm – 1 that forms part of the charge transfer band. The 2Eg and 2T2 g states of the octahedral Cu(II) ion (d9) split under the influence of the tetragonal distortion to three transitions; 2B1 g ! 2B2 g; 2B1 g ! 2Eg and 2 B1 g ! 2A1 g to remain unresolved in the spectra (Kohout et al., 1999). It is concluded that all three transitions lie within the single broad envelope centered at the same range previously mentioned. This assignment is in agreement with the general observation that Cu(II) d-d transitions are normally close in energy (Bury et al., 1987).

CONCLUSION The structures (I –V) of the investigated mono- and biscomplexes of sulfasalazine were suggested based on the results of elemental analyses, i.r., molar conductance, magnetic moment and solid reflectance and thermal analysis (TGA). The structures (I – V) were drawn in Scheme 1. All the complexes isolated are neutral as confirmed by the molar conductance measurements. For the monocomplexes, the chelation is brought by the deprotonation of both the phenolic-OH

and carboxylic-OH groups. For the biscomplexes, the chelation is brought by the deprotonation of the carboxylic-OH only and the phenolic-OH participates in coordination without proton displacement. In general, sulfasalazine can be regarded as a bidentate, mono- or dianionic ligand. REFERENCES Ali, M. M.; Majumder, S. S. M. H.; Butcher, R. J.; Jasinski, J. P.; Jasinski, J. M. Polyhedron 1997, 16 (16), 2749. Badiger, B. M.; Angadi, S. D.; Patil, S. A.; Kulkarni, V. H. J. Indian Chem. Soc. 1995, 72, 801. Beerlev, W. N.; Pelers, W.; Mager, K. Ann. Trop. Med. Parasite 1960, 26, 288. Bury, A.; Underhill, A. E.; Kemp, D. R.; O’Shea, N. J.; Smith, J. P.; Gomm, P. S. Inorg. Chim. Acta 1987, 138, 85. Clyson, D. B.; Pringle, J. A. S.; Ranses, G. M. Biochem. Pharmacol. 1967, 16, 614. Filo, J. J.; Terron, A.; Mulet, D.; Merno, V. Inorg. Chimica Acta 1987, 135, 197. Hay, M. T.; Hainaut, B. J.; Geib, S. J. Inorg. Chem. Communications 2003, 6 (5), 431. Hoffman La Roche Co. Swiss Patent, 416648, 1967. Hosny, W. M. Synth. React. Inorg. Met.-Org. Chem. 1997, 27, 197. Hosny, W. M. Synth. React. Inorg. Met.-Org. Chem. 1999, 29, 361. Irving, H.; Rossitti, H. S. J. Chem. Soc. 1953, 3997. Irving, H.; Rossitti, H. S. J. Chem. Soc. 1954, 2904. Iskander, M. F.; Khalil, T. E.; Werner, R.; Haase, W.; Svoboda, I.; Fuess, H. Polyhedron 2000, 19, 949. Kapahi, A.; Pandeya, K. P.; Singh, R. P. J. Inorg. Nucl. Chem. 1978, 40, 355. Kohout, J.; Hvastijova, M.; Kozisek, J.; Diaz, J. G.; Volko, M.; Jager, L.; Svoboda, I. Inorg. Chim. Acta 1999, 287, 186. Manonmani, J.; Thirumurugan, R.; Kandaswamy, M.; Kuppayee, M.; Raj, S. S. S.; Ponnuswamy, M. N.; Shanmugam, G.; Fun, H. K. Polyhedron 2000, 19, 2011. Manonmani, J.; Thirumurugan, R.; Kandaswamy, M.; Narayanan, V.; Shanmuga, S.; Raj, S.; Ponnuswamy, M. N.; Shanmugan, G.; Fun, H. K. Polyhedron 2001, 20 (26 – 27), 3039. Masoud, M. S.; AbouElenein, S. A.; Ayad, M. E.; Goher, A. S. Spectrochim. Acta 2004, A 60, 77. Mohamed, G. G. Spectrochim. Acta, Part A 2001, 57, 1643. Moustafa, M. M. J. Thermal Anal. 1997, 50, 463. Nygard, B.; Olofsson, J.; Sandberg, M. Acta Pharmaceutica Suecica 1966, 3, 313. Reddy, P. S.; Reddy, K. H. Polyhedron 2000, 19, 1687. Sandhu, G. K.; Verma, S. P. Polyhedron 1987, 6 (3), 587. Santi, E.; Torre, M. H.; Kremer, E.; Etcheverry, S. B.; Baran, E. J. Vib. Spectrosc. 1993, 5, 285. Schmidt, L. H. Ann. Rev. Microbiol. 1969, 23, 427. Shoukry, M. M.; Shoukry, E. M. Int. J. Chem. 1991, 2, 81. Soliman, A.; Linert, W. Thermochim. Acta 1999, 338, 67. Sarin, R.; Munshi, K. N. J. Inorg. Nucl. Chem. 1972, 34, 581. Tarbini, G. Inst. Congr. Chemother. Proc. 5th 1967, 2 (2), 909. Tarbini, G. Proc. Int. Cong. Chemotherapy 1967, 2, 909. Vaichulis, A. U.S. Patent, 1966; Vol. 3272, p. 352. Velusamy, M.; Palaniandavar, M.; Thomas, K. R.J. Polyhedron 1998, 17 (13 – 14), 2179.