Synthesis and Characterization of the Thiazolidinone and/or Thiourea substituted Amine Complexes of Cu (II)

Introduction

Thiazolidinones are the derivatives of thiazolidine which belong to an important group of heterocyclic compounds containing sulfur and nitrogen in a five member ring. The nucleus is also known as wonder nucleus because it gives out different derivatives with all different types of biological activities.

Chemistry of complexes derived by partial or complete replacement of strongly coordinated ammonia, halogen, cyanide or thiocyanate by organic ligands like Schiff’s bases have rare mention ^[1-3] in literature. Products obtained by replacement of ammonia of  ammine complexes of copper(׀׀), with  2-(2-hydroxy benzoyl)-3-N-(2-mercaptyl)-1-Thiazolidin-4-one (1) or 2-(2-hydroxy benzoyl)-3-N-(2-Pyridinyl)-1-Thiazolidin-4-one(2) alone and along with thiourea have not been described hitherto and we now report their synthesis. Product(s), isolated as binary mixture(s) were resolved by column chromatography.

Experimental

Materials and Methods

Thiazolidinones (1) and (2) were prepared by known methods ^[4] of cyclocondensation of respective ketoanils with thioglycolic acid and  purified by recrystallization. Ammine complex Cu(NH₃)₄]Cl₂ was prepared and purified by  King’s methods ^[5]. Metal Chloride and other chemicals (Aldrich, Qualigen and BDH) were used as supplied except solvents which were used after distillation.

Preparation of Complexes

Complexes resulting from partial replacement of coordinated ammonia by (1) or (2) alone and along with thiourea were prepared by mixing ethanoic solutions of ligands (0.1 mol each) with aqueous ethanoic (70%) solutions of ammine complexes (0.1 mol) in presence of NH₃ (5 cm³).   a-fraction of ligand (1) and thiourea substituted ammine complexes of Cu (׀׀)  precipitated immediately or after refluxing the reaction mixture (4-6hrs) .The products were washed with EtOH/Me₂CO and dried in hot air oven at 80°C; b-fraction isolated from filtrates on concentration and crystallization was washed with EtOH/AcOH-Toluene(3:1 v/v) Et₂O and dried at 100^◦C Ligand (2) substituted ammine complexes of Cu(׀׀) crystallized from their reaction mixtures after their 6-12 hrs refluxing. rom the reaction mixture containing (2), thiourea and [Cu(NH3)₄]Cl₂, Cu₃(C₁₅H₁₁N₂O₃S)Cl₆.2H₂O was precipitated immediately whereas Cu(SCN₂H₄)(C₁₅H₁₁N₂O₃S)Cl₂.5H₂O, was isolated on refluxing, concentrating and crystallizing the filterate.

Resolution of Binary Complexes

Chromatography was undertaken in a column (50cm length, 2cm diameter) containing silica gel (50-100 mesh, BDH) in AcOH-C₆H₆(2:1 v/v). The binary products were dissolved in dimethylsulphoxide  and loaded in the column, and the fast moving component eluted. The slow moving component was eluted with an appropriate solvent. Eluates were evaporated to dryness under reduced pressure.

Analysis and Physical Measurements

C_,H and N analysis were done on Vario-el-׀׀׀ Element-R. Melting points determined in open glass capillaries were uncorrected, infrared spectra were recorded on Thermo Nicolet Nexus FT-IR  spectrometer in Nujol whereas reflectance spectra were recorded on a Carl-Zeiss VSU-2P spectrophotometer in MgO. Conductometric measurements on standard solutions of complexes in DMSO were made on Toshniwal Conductivity Bridge using a dip-type cell. Magnetic susceptibilities for solids were measured in vibrational magnetometer. Molecular weights were determined by micro Rast’s method ^[6] using Camphor solvent.

Results and Discussion

Analysis and molecular weights data are in conformity of proposed molecular formulae. Silver nitrate test revealed non-electrolytic nature of complexes.

IR spectrum of (1) together with ammonia and thiourea exhibits frequencies of C-N (cyclic), C-S-C (cyclic) and SH groups at 1600 cm^-1 690cm^-1 and 2670cm^-1 respectively. Considerable lowering in C-N(cyclic) frequency and disappearance of SH band in complexes led to the inference that (1) is coordinated with metal ions through its thiazolidinone ring nitrogen and deprotonated mercaptyl group. New low frequency peaks corresponding to M-N and M-S stretches appeared in the spectra of complexes supported the participation of these groups in coordination. Ligand (2) displays νC = O(cyclic) and νC=N(cyclic) vibrations at 1600 cm^-1 and 1590cm^-1 respectively. In the complexes obtained by partial or complete substitution of ammonia by (2) alone or along with SCN₂H₄, thiazolidinone ring carbonyl group peak disappeared and pyridine ring C=N group frequency lowered considerably. This suggests coordination of thiazolidinone ring carbonyl oxygen after its enolization and pyridine ring nitrogen. Two new low frequency bands corresponding to M-O and M-N stretches confirm this inference. In the products obtained by partial substitution of ammonia by (1) or (2) an additional band of νM-N is observed. If two nitrogens are coordinated one is from thiazolidinone ring or pyridine ring and other should be from ammonia. The low symmetrical deformation (ca. 1608 cm^-1) and rocking(ca. 842 cm^-1) vibrations of coordinated ammonia confirm this. In the IR spectra of complexes involving (1) or (2), NH₃ and SCN₂H₄, unperturbed additional ammine frequencies and a new low frequency band (260 cm^-1) suggest bonding of SCN₂H₄ through sulphur.

Coordination of monodentate chlorine is indicated by νM-Cl band occurring in 300 cm^-1 -320 cm^-1  region whereas chlorine bridged polynuclear structures are supported by either a well-defined νM-Cl-M peak or a broad peak arising by mixing of closely spaced νM-Cl peak. Lattice water exhibits symmetrical and anti-symmetrical stretching and bonding vibrations in 3321cm^-1 to3442cm^-1  and1600cm^-1 to1625cm^-1 ranges respectively, whereas coordinated water displays ρ_t,  ρ_w and ρ_r vibrations in825cm^-1-995cm^-1 range.M-OH₂ bands, which generally occur in 200cm^-1 to450cm^-1 region, could not be clearly identified owing to presence of νM-N, νM-Cl and νM-S bands in this region.

Analytical data of Complexes

1.  [Cu(NH₃) (C₁₆H₁₂NO₃S₂)(H₂O)₂Cl].4 H₂O 

Colour : Grey; M.P:190ºC. Anal Calcd.:  C,34.65; H, 4.87; N,5.05. Found: C, 34.72; H,4.87; N,5.05. Mol.wt: Calcd: 554; Found:555. IR(cm-¹) : νC-N(cyclic), 1500; νC-S-C, 702sh; νM-NH3 and/or M-O, 529; νM-N, 457; νM-Cl, 300; νM-S, 270.

2. [Cu(NH₃)( C₁₆H₁₂NO₃S₂)₂(H₂O)]. H₂O

Colour : Grey; M.P:209ºC. Anal Calcd.:  C,24.72; H, 2.44; N,5.40. Found: C, 24.77; H,2.85; N,5.40. Mol.wt: Calcd: 777; Found:769. IR(cm-¹) : νC-N(cyclic), 1505; νC-S-C, 650; νM-NH3 and/or M-O, 544; νM-N, 457; νM-S, 290.

3. [Cu(NH₃) (SCN₂H₄) (C₁₆H₁₂NO₃S₂)( H₂O)Cl].H₂O

Colour : Green black; M.P:240ºC. Anal Calcd.:  C,36.55; H, 4.48; N,10.03. Found: C, 35.99; H,4.33; N,10.15. Mol.wt: Calcd: 558; Found:555. IR(cm-¹) : νC-N(cyclic), 1511; νC-S-C, 667; νM-NH3 and/or M-O, 527; νM-N, 433; νM-Cl, 300; νM-S, 285 and 260.

4. [Cu₂(NH₃) (C₁₅H₁₁N₂O₃S) (H₂O) ₃Cl₄]

Colour : Brown; M.P : 238ºC. Anal Calcd.:  C,30.76; H, 2.29; N,7.17. Found: C, 30.92; H,2.20; N,7.22. Mol.wt: Calcd: 585; Found : 588. IR(cm-¹) : νC-N(cyclic), 1625br; νC-S-C, 675; νC=N,1433; νM-NH3 and/or M-O, 500 and 467br; νM-N, 417, 467br; νM-Cl, 300 and 280.

5. [Cu₃(C₁₅H₁₁N₂O₃S)Cl₆].2(H₂O)

Colour : Grey; M.P : >300ºC. Anal Calcd.: C,24.37; H, 2.03; N,3.79. Found: C, 24.05; H,2.44; N,3.83. Mol.wt: Calcd: 775; Found : 769. IR(cm-¹) :  νC-S-C, 674; νC=N,1449; νM-NH₃ and/or M-O, 483br;  νM-N, 434; νM-Cl, 295br.

6. [Cu(SCN₂H₄)( C₁₅H₁₁N₂O₃S)( H₂O)Cl₂]. 4H₂O

Colour : brown; M.P:200ºC. Anal Calcd.:  C,32.02; H, 4.17; N,9.34. Found: C, 31.62; H,4.27; N,9.28. Mol.wt: Calcd: 599; Found:588. IR(cm-¹) : νC-N(cyclic), 1608; νC=N,1466; νM-NH3 and/or M-O, 500 and 475br; νM-N, 417; νM-Cl, 305; νM-S, 260.

Band frequencies, assignments and values of ligand field parameters obtained by standard treatment ^[8] are in table 1.

Table 1. Magnetic Moment and Reflectance Spectra of Complexes.

Complexes	MagneticMoment(μeff)BM	Reflectance Spectra		10Dq(cm-1)
		Band(cm-1)	Assignment
[Cu(NH3) (C16H12NO3S2)(H2O)2Cl].4H2O	2.00	12563 1538523364 24510 25253 26667 2732240816 47619	2T2g← 2Eg                                   2B2g←2B1g          2Eg Metal← Ligand Charge Transfer	12563
[Cu(NH3)(C16H12NO3S2)2(H2O)].H2O	1.95	12626 1292027548 28409 34483 3533640162	2T2g← 2EgMetal←Ligand Charge Transfer	12920
[Cu(NH3)(SCN2H4)(C16H12NO3S2)(H2O)Cl].H2O	1.89	12579 1310621786 23202 2381027933 35336 3787940323 43668 48780	2T2g← 2Eg                                 2A1g←2B1g 2B2g←               2Bg←Metal← Ligand Charge Transfer	12579
[Cu2(NH3) (C15H11N2O3S) (H2O) 3Cl4]	1.67	12920 20964 21552 2352928248  3623240816 45455 47170	2T2g←2Eg    2A1g←2B1g 2B2g←              2Eg←Metal← Ligand Charge Transfer	12920
[Cu3(C15H11N2O3S)Cl6].2(H2O)	1.70	16367 16694 1733140650 48547	2A1g←2Bg    2B2g←              2Eg←Metal← Ligand Charge Transfer	–
[Cu(SCN2H4)(C15H11N2O3S)(H2O)Cl2].4H2O	1.85	12594 12920 26455 27174 28090 40323 47170 50000	2T2g← 2EgMetal← Ligand Charge Transfer	12920

 

The magnetic moment and reflectance spectrum of [Cu₃(C₁₅H₁₁N₂O₃S)].2H₂O displaying three d-d transition bands in 16367-17331 cm^-1 range, characteristic of  D_4h symmetry ^[1,9], indicate its square-planar geometry. All other copper (׀׀) complexes displaying one or two broad bands in 12516-15385 cm^-1 range and othertwo or three bands in 16367-24510 cm^-1 region indicate ^[10]  their distorted octahedral stereochemistry involving  ² T_2g ← ²E_g transitions; the ²E_g state being susceptible to John-Teller distortion may account for the broad peak structure.

References

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5. A.King in A.J.E. Welch(Ed.), Inorganic Preparation, Allen and Unwin, London, 1950.
6. S.Glasstone, A Text Book of Physical Chemistry, Macmillan and co. London, 1974
7. R.K.Upadhyay, D.Sc.Thesis, C.C.S University, Merrut, 1994.
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9. N.M. Karayaumis, C.M.Milkulski, I.L. Pytlewski and M.M.Labes, J. Inorganic nucl Chem.,1972, 34, 3139.
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