Metal ion controlled synthesis of 16-and 18-membered binuclear octaazamacrocyclic complexes with Co(II), Ni(II), Cu(II) and Zn(II): a comparative spectroscopic approach to DNA binding to Cu(II) complexes

A series of 16- and 18-membered binuclear octaazamacrocyclic complexes, [M(2)L(1)(NO(3))(4)] and [M(2)L(2)(NO(3))(4)] (M = Co(II), Ni(II), Cu(II), Zn(II), L(1) = = 3,8,11,16-tetramethyl-1,2,4,7,9,10,12,15-octaaza-3,7,11,15-cyclohexadecatetraene and L(2) = 3,9,12,18-tetramethyl-1,2,4,8,10,11,13,17-octaaza-3,8,12,17-cyclooctadecatetraene) were synthesized by metal template condensation of N,N'-diacetylhydrazine with 1,2-diaminoethane and 1,3-diaminopropane in methanol. The formation of macrocyclic ligand frameworks, the bonding of the macrocyclic moieties in the complexes and the overall geometry of the complexes were deduced based on the results obtained from elemental analyses as well as molar conductivity, FTIR, (1)H-, (13)C-NMR, EPR, ESI-mass, UV-Vis spectral studies and magnetic measurements. An octahedral geometry is proposed for all the complexes, while a distortion in the octahedral geometry was registered for the Cu(II) complexes. Comparative fluorescence and UV-Vis studies on the Cu(II) complexes proved a significant binding to calf thymus DNA.