Coordination arrays - Synthesis and characterization of tetranuclear complexes of grid-type

A series of tetranuclear metal complexes of grid-type consisting of four bis-tridentate ligands and four divalent transition metal ions were synthesized and characterized. The H-1 NMR spectra of diamagnetic complexes containing Zn(II), Cd(II), Fe(II), and Ru(II) was correlated to the radius of the metal ion. The UV-vis and electrochemical results indicated that the bridging ligand pi* orbital and the d(pi) metal orbital are stabilized by complexation of more than one metal ion. Furthermore, the Co(II) and Fe(II) grids exhibit metal-metal interaction mediated by the bis-tridentate ligands as indicated by electrochemical and spectroscopic methods. These results provide guidelines for the design of larger grids bearing several metal centres in a square arrangement, which also represent potential components of molecular electronic devices.