Synthesis and characterization of new Mn(II) and Cd(II) Schiff base complexes containing homopiperazine moiety: Spectral, X-ray crystal structural and theoretical studies

摘要

Two new symmetrical Mn(II) and Cd(II) pentaaza macrocyclic Schiff base complexes were prepared via templated [1 + 1] cyclocondensation of 2,6 diacetylpyridine and an amine containing homopiperazine moiety in the presence of related metal ions. These complexes have been characterized by elemental analysis, IR spectra, EI-MS, conductivity measurements and in the case of Cd(II) complex by H-1 and C-13 NMR spectroscopy. In addition, Crystal structures of complexes have been determined by X-ray crystallographic technique. This reveals that in the solid state both complexes adopt a distorted pentagonal pyramidal geometry, with the pentaaza macrocycle positioned in the equatorial plane and the chloride ion in the axial site. Also, the bonding situation between the [MCl](+) (M = Mn2+, Cd2+) fragment and Ligand (L) in [MLCl](+) (M = Mn, Cd) complexes, were carried out by NBO and energy-decomposition analysis (EDA), as well as its natural orbitals for chemical valence variation (EDA-NOCV). The results confirmed that the contribution of the electrostatic interactions in the M <- L bonds of the complexes is predominantly more than 50%. (C) 2015 Elsevier B.V. All rights reserved.