Synthesis, spectroscopy, thermal behavior, and X-ray crystal structure of two lead(II) complexes with 4′-(4-tolyl)-2,2′;6′,2″-terpyridine (ttpy)

Abstract

Two new lead(II) complexes with 4′-(4-tolyl)-2,2′;6′,2″-terpyridine (ttpy), [Pb(ttpy)(µ-AcO)]2(PF6)2 (1) and [Pb(ttpy)(µ-AcO)I]2 (2), have been synthesized and characterized by CHN elemental analysis, 1H NMR, 13C NMR, IR spectroscopy, and structurally analyzed by X-ray single-crystal diffraction. The thermal stability of these compounds has been studied by thermal gravimetric analysis and differential thermal analysis. Single crystal X-ray analysis shows that 1 and 2 are dimeric units with Pb–(µ-AcO)2–Pb-type bridging, and the coordination number in 1 is six and in 2 is seven. The arrangement of donors suggests a gap in the coordination geometry around lead, possibly occupied by stereo-active lone pair of electrons on lead(II), so the coordination sphere is hemidirected. Furthermore, dimeric units are connected by a network of hydrogen bonds and π–π stacking as well. Electrochemical properties of free ligand and complexes have been investigated in the presence of tetrabutyl ammonium perchlorate as supporting electrolyte and by using a glassy carbon electrode. Both lead complexes show irreversible Pb(II) oxidation. Cyclic voltammetry indicates that these processes are diffusion-controlled. The data from electrochemical studies show that the total limiting current of each of the studied complexes corresponds to two-electron transfer.