Structural diversity in mercury(II) coordination complexes with asymmetrical hydrazone-based ligands derived from pyridine

•Three novel Hg(II) complexes of asymmetrical hydrazone–pyridine based ligands are obtained.•The coordination architecture depends on the position of N atoms in the pyridine moieties.•The crystal structure is stabilized by N/O–H⋯N/O/I hydrogen bonds and π⋯π interactions.

Three novel Hg(II) complexes 1–3 of asymmetrical hydrazone–pyridine based ligands, L1–L3, with distinct coordination structures have been prepared and characterized by a single crystal X-ray diffraction, elemental and thermal analysis, and IR spectroscopy. The complexes form either discrete units with one (1) or two (2) organic ligands, or one-dimensional polymers (3). Hence the ligands can be regarded as chelating (1), mono-dentate (2) or bridging (3) agents. The mercury center is essentially neutralized in each complex by two iodide anions. The coordination in complexes 2 and 3 adopts deformed tetrahedral shapes. In contrast the Hg(II) cation in complex 1 binds three coplanar ligating atoms (O,N,N) and, as with pincer ligands, its coordination polyhedron is supplemented with two I− anions in apical positions. The structural diversity in these complexes is strongly influenced by the position of N atom in pyridine derived moieties. The crystal structure is stabilized by N/O–H⋯N/O/I hydrogen bonds and π⋯π interactions.

Graphical abstractSynthesis, characterization and crystal structures of three novel Hg(II) complexes of asymmetrical hydrazone–pyridine based ligands have been investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide