Synthesis, Spectral, Thermal and Structural Study of Monoaquabis(Acetylsalicylato-kappa O)bis(Nicotinamide-kappa N)Copper(II)

Abstract

The compound has been formed by mononuclear [Cu(C9H7O4)(2)(C6H6N2O)(2)(H2O)] units in which the metal ion as well as the water ligand lies on a twofold symmetry axis, so that only one acetylsalicylate ligand and one nicotinamide ligand are independent. The distortion from ideal five-coordinate geometries can be described best by the degree of trigonality tau. For a regular square-pyramidal (SQP) geometry the trigonality parameter is 0 and for a trigonal-bipyramidal (TBP) structure it increases to 1. The copper coordination geometry is that of a square pyramid (tau = 0.23), with the N atoms from nicotinamide ligands and the bonded carboxylate O atoms from acetylsalicylate ligands defining the quasi-planar square base. The apical site is occupied by the aqua ligand, a bond which coincides with the twofold symmetry axis and is thus exactly perpendicular to the basal plane. The thermal decomposition takes place in four steps: removing of moisture, dehydration of aqua ligand, the elimination of the nicotinamide (na) ligand and the decomposition of acetyl-groups and oxidation of salicylate ion ligands. In complex, all ligands are coordinated to the metal ion as monodendate. The IR spectra of the intermediate products showed similar results.