Metal chelates with some cellulose derivatives; part IV. Structural chemistry of HEC complexes

Abstract

Reactions of hydroxyethyl cellulose (HEC) with CrIII, NiII, CoII, or CuII chlorides in aqueous medium yielded complexes with formulae [M(HEC)Cl m .nH2O], wherem=1 or 2 andn=2 or 3. HEC acted as a uninegatively charged bidentate ligand in the case of CrIII and NiII, and as a neutral ligand in the case of CoII and CuII complexes. The spectra showed that the binding sites in CrIII and NiII complexes were the ether oxygen between two ethoxyl groups and the oxygen of the hydroxyl group; while in the CoII and CuII complexes the binding sites were the oxygen of ethoxyl groups and the primary alcoholic O atom of glucopyranose rings. These complexes would most likely exhibit octahedral geometry with CrIII, NiII, and CoII, but square planar configuration in the case of the CuII complex. The ligand parameters of the CrIII, NiII, and CoII metal chelates were calculated in different solvents and at different temperatures. The thermal stability of the above complexes was investigated and the overall thermodynamics functions ΔG0, ΔH0, and ΔS0, associated with complex formation, were estimated.