CHARACTERISATION OF SOME MIXED LIGAND COMPLEXES OF IMIDES AND AMINO ACIDS

Abstract

The work embodied in this thesis is on the inter action of transition metal ions with organic ligands containing one or more salt forming groups e.g. (I)-C00H(II)-NH(III)-0H(IV)-SH etc The chelates of such ligands are of great importance from analytical, medicinal and industrial point of view. The studies aim at investigating the nature, structure and solubi lity of the complexes. A part of the thesis is devoted to their thermodynamical studies. The ligands used are imides, aminoacids, amines and phenols. A major portion of the thesis is devoted to the preparation of mixed ligand complexes and their characterisation on the basis of chemical analysis, I.R., electronic spectra, Mossbauer spectroscopy, conductance and magnetic measure ment. The thesis has been divided into three sections, viz., A, B and C• SECTION - A This section comprises of two chapters. Chapter - I : This chapter deals with the characterisation of the complexes formed by the interaction of potassium hexathiocyanatochromate(IIl) with iminodiacetic and diethylenetriaminepentaacetic acids. The complexes K2[Cr(NCS)3(C4H504N)] and K3[Cr(NCS)4( C^H^Oj^) ] could ii n be prepared in the solid form and characterised on the jasis of various physico-chemical studies. The values of 10 Dq was found to be 17000 and 18000 cm for the first and second complex respectively. The values of B, p35 and L«F«S.E. have also been calculated from the bands obtained in the electronic spectra of the complexes. I.R. spectra of the complexes indicated the coordina tion of thiocyanate through N and of iminodiacetic acid through NH and carboxyl groups. While diethylenetriaminepentaacetic acid is coordinated through carboxyl groups and behave as a bidentate ligand. Chapter - II : This chapter describes the results on the studies of mixed ligand complexes of Cr(IIl) with nitrilotriacetic acid as primary and some phenols and phenolic acids as secondary ligands. On the basis of conductance, polarographic, I.R., electronic spectra and magnetic studies, the complexes of the type K2[Cr(NTA)(P)2] and K?[Cr(NTA)(A-A)] where NTA = nitrilotriacetate, P = deprotonated phenol, 4-chlorophenol, 4-nitrophenol, o-cresol, hydroquinone and a-naphthol and A-A = pyrogallol, pyrocatechol, alizarin, salicylic acid, 4-aminosalicylic acid and 4-sulphosalicylic acid were found to have an octahedral structure. The coordinating power of these phenolic compounds was in the order : hydroquinone > 4-nitrophenol > phenols 4-aminosalicylic acid > 4-chlorophenol4*pyrogallol*»pyrocatechol«* o-cresol ill "^salicylic acid«ft<f4-sulphosalicylic acid > a-naphthol > clizrm. SECTION - B This section comprises of two chapters. Chapter - I : In this chapter are Incorporated the results of Mossbauer studies on the mixed ligand complexes of Fe(lII) phthalimide with some amino-acids (histidine, anthranilic acid, glutamic acid, arginine, cysteine and methionine). The complexes having the formulae NH4[Fe( C8H402N)3( C^H^O^S) (H20) ] , K[Fe( CgH402N)2 (C5H?04N) (H20)2] , K[Fe( CgH402N)3( C3H602NS) (H20) ] , [Fe( C8H402N)2( C6H13N402) (H20)2] , [Fe( CgH^)^ C^N^) (H20)2] and [Fe( CgH^^^C^OgN) (H20)23 could bs prepared in the solid form. I.R. spectra of the complexes indicated the coordination of phthalimide through nitrogen and of amino-acid through amino and carboxyl groups, while cysteine and methionine were found to coordinate through sulphyhydril and carboxyl groups. Two bands at around 810 and 640 cm" due to wagging and rocking modes of coordinated water were observed in the spectra of all the complexes. The values of magnetic moments lies in between 5.50 - 6.00 B.M. The electronic spectra of all the complexes in butanol gave three bands at 29500, 34000 and 39000 cm""1 corresponding to the transitions IV 6AAlg—>>4TTlg(P)> 6AAlg~->>4TTlg^F) and 6AAlg >4TT2g<F) reS~ pectively. The values of isomer shift around 0.38 mm sec"" indicated a greater electron density at the nucleus- The values of quadrupole splitting in the range 0.47 - 0.68 mm seo indicated the presence of different types of ligands inside the coordination sphere. Chapter -. II : This chapter deals with the preparation and characterisation of mixed ligand complexes of platinum(Il) palladium(ll), platinum(IV), iridium(IIl) and rhodium(IIl) with phthalimide as primary and dipyridyl and o-phenanthroline as secondary ligands. Complexes of the type [M(H)Ph2A], [M(lV)Ph4A] and [M(IIl)Ph3(H20)A] where Ph = phthalimide (deprotonated) and A = dipyridyl or o~phenanthroline, could be isolated in solid form and characterised. Pt(Il) and Pd(ll) complexes were of square planar structure. The values of a^, zv> and a^ have been calculated for these complexes. The absorp™ tion spectra of diamagnetic octahedrally coordinated d metal ions i.e. Pt(IV), Ir(IIl) and Rh(lII), gave three d-d transitions. Two of these are spin-allowed bands involving 1. .1™ and 1. JU transition and . Alg—> rlg Alg * i2g the third spin-prohibited band is 1 - 3_ . The Alg~~* lg values of ligand field stabilisation energy and Racah parameters B and C and nephelauxetic ratio p have also been calculated. The values of ligand field splitting energy and hence the stability of the complexes decrease in the order : Pt(IV) > Ir(IIl) > Rh(lll). I.R. spectra of the complexes indicated the coordina tion of phthalimide through nitrogen and the presence of dipyridyl and o-phenanthroline inside the coordina tion sphere. In the case of Rh(IIl) and Ir(lll) com plexes, the coordinated water molecule gave the bands at 650 and 860 cm"1. SECTION - C This section also comprises of two chapters. Chapter - I : This chapter has been devoted to the thermodynamical studies of cysteinate complexes of rhodium(IIl) and osmium(VIIl) • The thermodynamical stability cons tants of the metal complexes have been determined by Bjerrum' -Calvin titration technique as adopted by Irving and Rossotti. The values of aF, aH and aS were calculated from the temperature coefficient of the equilibrium constants. A comparative study of the complexes of these metal ions with 2-mercaptopropanoic acid and cc-alanine have also been carried out. Analysis of thermodynamical data indicated the coordination of cysteine through sulphydril and carboxyl groups. The complexes of cysteine could also be isolated in the .solid form and their I.R. studies also confirmed the coordination through sulphydril and carboxyl groups. VI The electronic spectrum of Rh(IIl) complex gave :wo spin-allowed bands at 19100 and 25500 cm" and a spin-forbidden band, at 14410 cm"1. The values of 10 Dq9 B, p, Cand L.F.S.E., (K cals.mole"1) were found to be 21445, 400, 0.55, 2345 and 24.50 respectively. Osmium (VIII) complex also gave three bands at 26000, 28850 and 36000 cm"1 which seems, to have arisen due to charge transfer. Chapter - II : This chapter has been devoted to the analytical use of cysteine in the spectrophotometry determination of osmium(VIIl). The yellowish brown complex exhibits a maximum absorbance at 370 nm in the pH range 4.0-5.2. Beer's law is obeyed from 1.0-60.0 ppm, the opt. range for accurate determinations being from 5.0-55.0 ppm. The Sandell' s sensitivity of the reaction is 0.132 p.g/cm and the molar absorptivity of the complex is 1429 K mole"1 cm"1. The apparent stability constant of 1:1 complex was found to be 1.2589 x 109 at 25 + 1°C A large number of ions do not interfere in the determina tion of Os(VIII) by this method.