Synthesis, structure, thermal studies on Zn(II), Cd(II) complexes of N-(2-pyridylmethyl)pyridine-2-carbaldimine and N-(2-pyridylmethyl)pyridine-2-methylketimine

The bivalent zinc and cadmium complexes of two Schiff bases N-(2-pyridylmethyl)pyridine-2-carbaldimine (L1), N-(2-pyridylmethyl)pyridine-2-methylketimine (L2), tridentate ligands with an N3 chromophore and coordinating with two five-membered chelate rings, were synthesized. Complexes [Zn(L1)(NO3)2] (1), [Zn(L2)(NO3)2] (2), [Cd(L1)(NO3)2(H2O)] (3) and [Cd(L2)(NO3)2(CH3OH)] (4) were characterized by X-ray crystallography. In 1 and 2, Zn(II) has a distorted square-pyramidal geometry where as in 3 and 4, Cd(II) possesses a pseudo-pentagonal-bipyramidal geometry. The following trends in the bond lengths are observed: M–Nim < M–Npy; Zn–N > Zn–O; Cd–N < Cd–O. The final residues from the thermogravimetric analysis are ZnO and CdO, the SEM studies revealed, respectively, their porous and spherical natures. The average activation energy (E) for the loss of pyridine rings obtained from the Friedman fitting of the DSC data, for 1, 2, 3, and 4 are 193.8(2), 114.5(3), 127.1(4), and 63.7(3) kJ mol−1 and their logarithmic pre-exponential factor (A) are 11.22, 5.31, 6.88, and 2.09, respectively.

Bivalent zinc and cadmium complexes based on two tridentate-N3 ligand were synthesized and structurally characterized. The final residual part of thermal decompositions are ZnO and CdO, the SEM studies revealed, respectively, their porous and spherical natures. The activation parameters obtained from the Friedman fitting of the DSC profiles for the loss of pyridine rings are reported.Figure optionsDownload as PowerPoint slide