Studies Of Valerohydroxamic And ' Isovalerohydroxamic Acids And Of Their Complexes With Some Biologicaly Important Metal Ions

ABSTRACT

Valerohydroxamic and Isovalerohydroxamic acids were

synthesised and recrystallised from ethylacetate. They were

characterised by melting point, pka and spectral (IR NMR) studies.

Their melting points are 77.78°C and 76.77°C for valerohydroxamic

acid and isovalerohydroxamic acid respectively and their pka values

at 0.1mol dm-3 at 28°C are 9.50+0.01 and 9.51+0.01 for

valerohydroxamic acid and isovalerohydroxamic acid respectively.

The IR and NMR (1H and 13C) for both valerohydroxamic and

Isovalerohyrdoxamic acids are in accord with the theoretical

prediction and observable patterns of the reported alkylhydroxamic

acids.

Their complexes with the following metal ions; Al3+, Co3+,

Co2+, Cu2+, Fe3+, Mn2+, V02+, and Zn2+, were prepared in good yield.

The complexes were characterised using solution, conductivity and

spectra (IR, electrical) studies. Their relatively low melting points in

the range of 142 - 215°C is suggestive of a weak interaction

between the species. The complexes are soluble in almost all the

polar organic solvents in which they were tested with the exception

of their Co3+ and Cu2+ complexes which are only sparingly soluble

and their low conductivity values in the range of 0.002 - 0.025

Scm2 mol-1 implies that they are non electrolyte in ethanol. The

xvii

absence of isosbestic points and the shape of the graphical r-ank

matrix analysis indicate that the complexes are made of single

species in solution. The Job's plot for the systems indicate a 1:2 and

1:3 metal-ligand ratio for the divalent and trivalent metal ions

respectively. The IR studies of the complexes show chelation by

coordination via the ketonic oxygen and the oxygen of the NHO-.

The electronic spectra of the transition metal complexes indicate

octahedral coordination for CoH, Co2+, Fe3+, Cu2+, Ni2+ and V02+

complexes, while the Cu2+ complexes may possibly be of a square

planar coordination.

The microbial activity of the ligands and their metal complexes

were tested against the following microbes; Sa, Es, Ps, Bs and Ca.

Valerohydroxamic acid was positive against Es and Bs, while

Isovalerohydroxamic acid was negative against all the micr-obes.

The Co2+ - Valerohydroxamate was positive against Sa and Ps, while

Co2+- Isovalerohydroxamate tested positive against Sa only. The

Co3+- Isovalerohydroxamate was positive against Sa, Ps and Ca,

while the Co3+ - Valerohydroxamate tested positive against Sa and

Bs and Fe3+ - Valerohydroxamate was positive against Sa and Ca.

All activity were low at a dose concentration of 1000􀅘L9/ml.