New Cu(II)4 and Zn(II)4 complexes: Synthesis, characterization and magnetic and biological studies

Two new isomorphous tetranuclear complexes [Cu4L2(4,4'-bipy)(2)]center dot(CIO4)(4)center dot 2CH(3)CN center dot 2H(2)O (1) and [Zn4L2(4,4'-bipy)(2)]center dot(CIO4)(3)center dot CH3O center dot 4H(2)O (2) have been obtained and fully characterized (where bipy = bipyridine, H2L = macrocycle is the [2+2] condensation product of 2,6-diformyl-4-fluoro-phenol and 1,4-diaminobutane). They exhibit wheel-like configuration in which two 4,4'-bipy molecules connect two dinuclear [M2L](2+) units. The interactions of the complexes with calf thymus DNA were studied by UV-Vis and CD spectroscopic techniques. The binding constants of 1 and 2 are 2.27 x 10(6) and 3.89 x 10(5) M-1, respectively. The magnetic measurement of 1 reveals that there are strong antiferromagnetic coupling (J = -272.6 cm(-1)) between two Cu(II) ions in the macrocyclic unit and ferromagnetic interaction (j' = 41.7) between the Cu(II) ions in two adjacent macrocyclic units. Furthermore, the cyclic voltammogram of 1 shows that it undergoes two quasi-reversible processes with the half wave potentials -0.232 and -0.606 V. respectively. (C) 2011 Elsevier Ltd. All rights reserved.