Macrocyclic mononuclear Ni(II) and macroacyclic tetranuclear Cu(II) complexes: Dimerization of binuclear Cu(II) complexes with help of perchlorate anions

Abstract

New macroacyclic Cu(II) and macrocyclic Ni(II) complexes, [Cu2L1(ClO4)2]2 (1) and [NiClL2]ClO4 (2), respectively, have been synthesized (H2L1 and H2L2 = Schiff bases). The Schiff bases H2L1and H2L2 were prepared by the reaction of 2-[3-(formyl phenoxy)-2-hydroxy propoxy]benzaldehyde and propanol amine and propylene diamine respectively. Single crystal X-ray structure analysis of 1 showed that the complex is tetranuclear, with two binuclear Cu(II) units connected through coordination of deprotonated OH groups of one of the propanol amine arms of each unit to the other one. In the structure of each binuclear fragment, none of the donor atoms of the potentially heptadentate (N2O5) ligand remained uncoordinated, and one oxygen atom is bridged between the two Cu(II) ions. In addition, the crystal structure analysis shows that two perchlorate ions are coordinated to the Cu(II) metal centers. DFT studies show that the coordinated perchlorate anions have the key role in the dimerization of the binuclear Cu(II) species that give rise to complex 1. X-ray structure analysis of 2 shows that it is a macrocyclic complex where all nitrogen and oxygen atoms of the potentially pentadentate (N2O3) ligand are coordinated to the Ni(II) central ion. In addition to the macrocyclic Schiff base ligand, a chloride ion is also coordinated to the Ni(II) ion.