Structural, thermal and spectroscopic properties of supramolecular coordination solids

Molecules in metal isonicotinate tetrahydrates, M(NC5H4-p-CO2)(2).4H(2)O with M = Mn, Fe, Co, Ni, Cu, Zn, consisting of the hexacoordinate complexes trans-[M(NC5H4-p-CO2)(2)(OH2)(4)], participate in exhaustive hydrogen-bond formation among themselves to lead to a robust 3D supramolecular network in the solid state. Solid-state diffuse reflectance UV-Vis-NIR spectra of the complexes have been assigned to ligand field and charge transfer transitions. Sharp weight loss due to dehydration, as shown by TGA of Cu(NC5H4-p-CO2)(2).4H(2)O, suggests the suitability of this complex for the gravimetric estimation of copper.