First Report on Crystal Engineering of Hg(II) Halides with Fully Substituted 3,4-Pyridinedicarboxamides: Generation of Two-Dimensional Coordination Polymers and Linear Zig-Zag Chains of Mercury Metal Ions

Abstract

Two new ligands N,N,N′,N′-tetraisopropyl/tetraisobutyl-3,4-pyridinedicarboxamide L1–L2 and six of their Hg(II)X2 complexes (where X = Cl–, Br–, and I–) have been synthesized and characterized. Single crystal X-ray structures of three complexes of L1 (1–3) with HgCl2/Br2/I2 and two complexes of L2 (4–5) with HgCl2/Br2 show that these are two-dimensional (2D) coordination polymers, with three different (one new) topologies and five coordinated Hg(II) ions, in square pyramidal coordination. Complex 6, of L2 with HgI2, is a dimer with a four coordinated tetrahedral Hg(II) ion. The ligands behave as two- or three-connecting linkers for forming coordination polymers (CPs) but only one-connector in the dimer. Various types of hydrogen bonding and other noncovalent interactions have been calculated, analyzed, and discussed for all the complexes and the ligand L1. Although the large size and soft character of iodide coupled with the steric effects of large isobutyl groups are mainly responsible for a change in the...