Three-dimensional frameworks built from hydrogen bonds and π-π stacking interactions:: structural and spectral study on Co(II) complexes of 1,5-diazacyclooctane (DACO) functionalized by heterocyclic pendants

A series of penta-coordinated Co(II) complexes of 1,5-diazacyclooctane (DACO) functionalized by additional imidazole or pyridine donor pendants, [(CoLCl)-Cl-1](ClO4).H2O(1), [(CoLCl)-Cl-2](ClO4) (2) and [(CoLCl)-Cl-3](ClO4) (3), where L-1 = 1,5-bis(imidazole-4-ylmethyl)-DACO, L-2 = 1,5-bis(N-1-methylimidazol-2-ylmethyl)-DACO and L-3 = 1,5-bis(pyridyl-2-ylmethyl)-DACO, have been synthesized and characterized by IR spectra, elemental analyses, conductance, thermal analyses and UV-Vis techniques. The structures of complexes 1 and 2 have been determined by X-ray crystallography. In all the mononuclear complexes, each Co(II) center is penta-coordinated due to the boat/chair configuration of the DACO rings and quite stable to oxidation. The most striking feature of complexes 1 and 2 is the formation of different 3D networks with channels through hydrogen-bonding and pi-pi stacking interaction. The solution behaviors of all the complexes have been further analyzed in detail. (C) 2001 Elsevier Science Ltd. All rights reserved.