Zinc(II) and Mercury(II) Complexes of Pyrazole-Based NNN-Type Ligands: Syntheses, X-ray Structures, Thermal Analyses and DFT Studies



Monomeric zinc(II) and mercury(II) complexes containing tripodal nitrogen donor ligand 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine (btmpp) were synthesized, and characterized by elemental and spectroscopic (IR, UV/Vis) analyses, TG-DTA and single-crystal X-ray diffraction studies. X-ray analyses of the complexes [Zn(btmpp)Cl2] (2) and [Hg(btmpp)(SCN)2] (3) showed that both structures crystallize in space group P21/c with a = 7.9722(6), b = 18.3084(13), c = 13.3117(9) Å and Z = 4 for 2 and a = 8.7830(3), b = 21.1489(7), c = 12.0682(4) Å and Z = 4 for 3. Both monomeric units contain pentacoordinate metal ions in distorted square-pyramidal arrangement. The structures of complexes 2 and 3 were also computed with DFT methods at B3LYP/LanL2DZ level and are in good agreement with the experimental values obtained from X-ray analysis. The NPa charge distributions, HOMO–LUMO gaps, and dipole moments for 1, 2, and 3 were also reported. Natural bond orbital analyses were performed to reveal local charges and charge transfers in 1, 2, and 3.