Steric and Electronic Effects on the Structure and Photophysical Properties of Hg(II) Complexes.

Since many factors influence the coordination around a metal center, steric and electronic effects of the ligands mainly determine the connectivity and, thus, the final arrangement. This is emphasized on Hg(II) centers, which have a zero point stabilization energy and, thus, a flexible coordination environment. Therefore, the unrestricted Hg(II) geometry facilitates the predominance of the ligands during the structural inception. Herein, we synthesized and characterized a series of six Hg(II) complexes with general formula (Hg(Pip)(dPy)) (Pip = piperonylate, dPy = 3-phenylpyridine (3-phpy) (), 4-phenylpyridine (4-phpy) (), 2,2'-bipyridine (2,2'-bipy) (), 1,10-phenanthroline (1,10-phen) (), 2,2':6',2'-terpyridine (terpy) (), or di(2-picolyl)amine (dpa) ()). The elucidation of their crystal structures revealed the arrangement of three monomers (, , and ), one dimer (), and two coordination polymers ( and ) depending on the steric requirements of the dPy and predominance of the ligands. Besides, the study of their photophysical properties in solution supported by TD-DFT calculations enabled us to understand their electronic effects and the influence of the structural arrangement on them.