Design of a flexible ligand for the construction of a one-dimensional metal-organic coordination polymer

Abstract

A new ligand LH (where LH = N-(picolinoyl)-biurate) has been prepared and characterized. The presence of three amide linkages make this ligand sufficiently flexible to act as N, N, O donor tridentate blocking ligand in the formation of a one dimensional metal-ligand layer like structure. Reaction of LH and dicyanamide (dca) with Co(NO 3) 2 · 6H 2O gives [CoL(dca)] n ( 1). In this compound picolinamide modulated ligand L coordinated the central Co(II) ion in a meridonal-fashion. The single crystal X-ray crystallography revealed that in 1, dca acts as μ 1,5− singly bridging ligand whereas μ 1,5− doubly bridging is the more common type. This gives rise to the 1D undulated waves like structure. The Co(II) centre is surrounded in a distorted square pyramidal coordination geometry. The variable temperature magnetic (VTM) susceptibility measurements show that the global feature of the χ M T versus T curve for 1 is characteristic of very weak antiferromagnetic interactions through the dicyanamide ligand and between 300 and 5 K the best fit parameter was determined as J = −3.52 cm −1. The X-ray structure, VTM study and UV–Vis spectrum of the compound show that 1 is a low-spin square-pyramidal compound whereas high-spin compounds are more common for the five coordinated cobalt (II) compounds. The X-band EPR spectrum of 1 at room temperature shows only one isotropic band centred at g = 2.08.