Effect of robust π–π stacking synthon on the formation of mercury coordination compounds; an unusual pseudo-square planar geometry

Abstract

In this study, three Hg(II) complexes, [HgCl2(L(2-naph))]n, 1, [HgBr2(L(2-naph))]n, 2 and [HgI2(L(2-naph))2], 3 where L(2-naph) is N-(naphthalene-2-yl)pyrazine-2-carboxamide ligand have been synthesized and characterized. X-ray single crystal diffraction analysis of these compounds reveals that 1 and 2 are isostructural coordination polymers and 3 is a discrete compound. In comparison to homologue complexes containing N-(naphthalene-1-yl)pyrazine-2-carboxamide ligand, interestingly, structural analysis clearly shows that displacing substituent position plays an important role in the formation of the supramolecular organization of molecular complexes. The common feature in the crystal packing of these complexes is that there is a strong tendency to form π-π stacking interaction between pyrazine and naphthalene rings. These π-π stacking interaction synthons affect the coordination geometry and structural assembly. Also, theoretical methods show the π-π stacking interaction energies within a range of -64.13 to -70.51 kJ mol(-1). It is notable that in 3, cooperation of intermolecular π-π stacking synthon and intramolecular C-H(pyz)···I-Hg hydrogen bond resulted in the formation of unusual pseudo-square planar geometry around the Hg(II) center. This study reveals an undeniable contribution of π-π stacking interaction to the organization and stabilization of some of the crystal structures reported here.

Coordination Polymers with Intramolecular Fluorine-Involved Contacts in Two-Dimensional Sheet Windows

“…During our research program aiming at the understanding of the role of intermolecular interactions in the crystal packing of mercury coordination compounds containing pyrazine carboxamide ligands, − we have synthesized, characterized, and investigated a series of designed complexes in the present work, in order to gain a deeper understanding on the crucial role of fluorine-involved interactions in the supramolecular architecture of coordination compounds including fluorinated ligands. In this article, a series of N -(fluorinatedphenyl)-2-pyrazinecarboxamide ligands, L 2‑F , L 2,5‑F , L 3‑F , L 2,3,4‑F , L 3,4,5‑F , L 2,3,4,5‑F , and L 2,6‑F , Scheme , carrying fluorine atoms on the phenyl ring, have been employed for the synthesis of six isostructural two-dimensional polymeric mercury­(II) coordination complexes 1 – 6 and a discrete complex 7 , in order to get insights into the investigation of fluorine-involved interactions on the structural assemblies.…”

Hg(II) coordination complexes containing the tris(2-pyridylmethyl)amine ligand: Synthesis, characterization and crystal structure analysis

“…In the course of these investigations, a quite unexpected sevenfold coordination of a hydrated Hg(II) complex in aqueous solution has been revealed [6]. Also, there are some examples reported in the literature describing the influence of weak intermolecular interactions on the coordination geometry of the metal center and the formation of unusual coordination geometries around the Hg(II) ion [7][8][9].…”

Halide bridged organophosphorus complexes of HgX2 (X: I, Br and Cl): Synthesis, structure and theoretical studies

“…In the course of these investigations, a quite unexpected sevenfold coordination of a hydrated mercury (II) complex in aqueous solution has been revealed [6]. Moreover, there are some examples reported in the literature describing the influence of weak intermolecular interactions on the coordination geometry of the metal center and the formation of unusual coordination geometries around the mercury (II) ion [7][8][9][10][11][12][13][14][15]. Several of phosphate acid complexes have been studied as promising materials for second harmonic generation [16,17].…”