Synthesis, Spectral, Thermal and Structural Study of Monoaquabis(Acetylsalicylato-κO)bis(Nicotinamide-κN)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 τ. 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 (τ = 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. The compound is formed by mononuclear [Cu(C9H7O4)2(C6H6N2O)2(H2O)] units, in which the metal ion as well as the water ligand lie on a twofold symmetry axis, so that only one acetylsalicylate ligand and one nicotinamide ligand are independent. The framework of compound is put in order as layers. The distortion from ideal five-coordinate geometries can be best described by the degree of trigonality τ.