Novel eight-coordinated Cd(II) complexes with two homologous pyridine alcohols : crystal structure, spectroscopic and thermal properties

Two novel cadmium(II) complexes with homologous pyridine alcohols: $[Cd(2-EtOHPy)_{2}(NO_{3})_{2}]$ (1) and $[Cd(2-EtOHPy)_{2}(NO_{3})_{2}]$ (2) have been prepared and characterized by elemental analysis, X-ray crystallo- graphic studies, spectroscopic (IR, $^{1}\textrm{H}$ and $^{13}\textrm{C}$ NMR) and thermal properties. IR, NMR and X-ray analysis have confirmed a bidentate fashion of coordination of heteroaromatic alcohols with Cd(II) ions. 2-MeO- HPy bound directly to the central ion by N, O-donor atoms giving five-membered chelate ring but 2- EtOHPy formed less stable six-membered chelate ring. In the complex (1) and (2) bidentate nitrate ligands are arranged in cis position for organic ligands. In both cases cadmium(II) ions are eight-coordi- nated and shape of coordination polyhedral can be described as pseudo-dodecahedron ($CdN_{2}O_{6}$ chromo- phore type). The crystal packing of Cd(II) complexes are stabilized by intermolecular classical hydrogen bonds of O–H$\cdots$O and non-classical C–H$\cdots$O type. In addition, there are $\pi$–$\pi$ stacking interactions between almost parallel-displaced pyridine rings of 2-hydroxymethylpyridine in the two neighbouring complex (1) molecules but the hydrogen interactions in (2) are formed by C–H donor group of Py rings and $\pi$-electron system of neighbouring one.