XANES studies of monosubstituted benzhydrazide complexes of copper

K x-ray absorption near-edge structure (XANES) studies were carried out on nine samples of monosubstituted benzhydrazide complexes of copper, viz. copper(II) benzhydrazide, o-, m- and phydroxybenzhydrazide, o-, m- and p-nitrobenzhydrazide and o- and p-chlorobenzhydrazide. These complexes are known for their pharmacological activity as antitubercular agents, antibacterial agents and as fungicides. In the three categories of substituted benzhydrazides the ionicity is found to increase in the order para > meta > ortho. Our studies revealed that the substituted complexes are less ionic than the parent complex. Among the three groups, hydroxy-substituted complexes are more ionic than nitro- and chloro-substituted hydrazides. Splitting of the principal absorption maximum (1s --> 4p) takes place in most of these complexes. The splitting into two components has been assigned to the transitions 1s --> A*(4p(z)) and 1s B*(4p(x), 4p(y)). The estimated bandgap values for these complexes decrease in the order ortho > meta > para. The present studies indicate that as the chemical shift values increase in all the three groups, the bandgap energy values decrease. Copyright (C) 2004 John Wiley Sons, Ltd.