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

• Synthesis of two new symmetrical macrocyclic Schiff base complexes.
• X-ray crystal structure determination indicated a distorted pentagonal pyramidal geometry.
• Spectral studies of complexes were performed using different physiochemical techniques.
• The contribution of the electrostatic interactions in the M ← L bonds is more than 50%.

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 1H and 13C 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%.

Two new macrocyclic Schiff base complexes [MnLCl]ClO4 and [CdLCl]ClO4,were prepared via templated [1 + 1] cyclocondensation and characterized by a variety of spectroscopic methods. Crystal structures of these complexes reveal that in the solid state these complexes adopt a distorted pentagonal–pyramidal geometry. The theoretical results confirmed that the contribution of the electrostatic interactions in the M ← L bonds of the present complexes is predominantly more than 50%.Figure optionsDownload as PowerPoint slide