Synthetic and structural investigations of Cd(II) complexes of tetradentate pyrimidine based Schiff base ligand: Insight through non-covalent interactions, TDDFT calculation and Hirshfeld surface analysis

Abstract

Two new Cd(II) complexes [Cd(L) (H2O)2]·(ClO4)2 (1) and [Cd(L) (SCN)2]·(H2O) (2) involving pyrimidine based tetradentate schiff base ligand 2,2'-((2E, 2′E)-2,2'-(butane-2,3-diylidene)bis (hydrazin-1-yl-2-ylidene))bis (4,6-dimethylpyrimidine) (L) are reported in this work. Both the complexes 1 and 2 are synthesized and characterized by elemental analyses, UV, IR, single crystal X-ray diffraction studies accordingly. Both of them are pseudooctahedral in geometry. In this report we want to highlight the variation of supramolecular non-covalent interactions in the solid state as a consequence of both apical ligand substitution (replacement of neutral aqua molecules by thiocyanate ion) and substitution of noncoordinating anionic counterions by coordinating anions. Complex 1 exhibits H-bonding, π … π stacking, CH … π and anion … π interaction whereas complex 2 displays π … π stacking and CH … π interaction only. The electronic transitions of both 1 and 2 were recorded and the electronic distribution of HOMO - LUMO can be rationalized theoretically (through time-dependent density functional theory (TDDFT)).