BINUCLEAR COMPLEXES OF A NEW HEXADENTATE MACROCYCLIC LIGAND - THE CRYSTAL AND MOLECULAR-STRUCTURE OF [LCU2(CH3CO2)2](CLO4)2.5H2O

The 30-membered hexaaza macrocylic ligand, L (L = 3,7,11,18,22,26-hexaazatricyclo-[26.2.2.2(13,16)tetratriaconta-1(31),13(33),14,16(34),28(32),29-hexaene), is capable of forming binuclear complexes with the divalent transition metal ions Ni, Cu and Zn. The two metal ions are bound by the two dipropylenetriamine units of the macrocycle. Extra coordination sites on the metal ions can be occupied by exogenous ligands such as acetate, chloride and thiocyanate. The crystal structure of one of the di-copper complexes is described: [LCu2(CH3CO2)2](ClO4)2.5H2O crystallizes in the monoclinic space group P2(1)/c (No. 14), with a = 9.369(2), b = 17.644(3), c = 27.466(3) angstrom, beta = 92.90(1)-degrees, U = 4534.7 angstrom3 and Z = 4. The Cu1 ... Cu2 separation is 8.40(3) angstrom. The access for potential exogenous bridging ligands, to the cavity between the copper ions, is somewhat restricted by the two phenyl units of the macrocycle which appear almost parallel in the structure. The redox potential of the couple L(Cu2+)2/L(Cu+)2, recorded by cyclic voltammetry for the chloride adduct, [LCu2Cl2]Cl2.5H2O, is -0.061 V versus SCE in DMF.