Cadmium (II) macrocyclic Schiff-base complexes containing piperazine moiety: Synthesis, spectroscopic, X-ray structure, theoretical and antibacterial studies

Abstract The new Cd(II) macrocyclic Schiff-base complexes were prepared via the metal templated [1 + 1] cyclocondensation of 2,2'-(piperazine-1,4-diylbis (methylene))dianiline (A) and 2,6-pyridinedicarbaldehyde or 2,6-diacetylpyridine. The products were characterized by elemental analysis, mass spectrometry and spectroscopic methods such as: FT-IR, 1 H and 13 C-NMR, the crystal structure of [CdL 1 (ClO 4 ) 2 ](CH 3 CN) (1) complex was also obtained by single-crystal X-ray crystallography. The complexes were tested for in vitro antibacterial properties against some bacteria. The complexes had antibacterial properties and in some cases were active even more than standards. The geometries of the [CdL n (ClO 4 ) 2 ], (n = 1,2) complexes have been optimized at the BP86/def2-SVP level of theory. Also the nature of Cd←L n (n = 1, 2) bonds in [CdL n (ClO 4 ) 2 ], (n = 1,2) complexes are studied with the help of NBO and Energy decomposition analysis (EDA). Results showed that the nature of metal-ligand bond in the complexes is slightly more electrostatic with a contribution of about 52% in total interaction energy.