Metal cation- and anion-induced assembly: structures and luminescent properties

Abstract

Three complexes HgLBr₂ (1), [HgLI₂]·CH₃CN (2) and HgL(SCN)₂ (3) were synthesized by self-assembly of a multidentate ligand containing pyridyl and pyrazolyl groups, namely, 6-phenyl-4-(4-(1H-pyrazolyl)phenyl)-2,2′-bipyridine (abbreviated as L), with corresponding mercury(II) salts. While the ligand reacted with Cd(NCS)₂ and Co(NCS)₂, complexes [CdL₂(NCS)₂]·H₂O (4) and [CoL₂(NCS)₂]·CH₃OH (5) were obtained. The structures of these complexes were determined by X-ray crystallography. In 1 and 3, the hydrogen bonding or C–H⋯π interactions based on the anions and the pyrazolyl nitrogen atom contribute to the 2-D and 3-D structures, respectively. Compared with 1 and 3, no hydrogen bonding interaction based on the I⁻ anion can be found in 2. As a result, only the C–H⋯N hydrogen bonding interactions based on the pyrazolyl nitrogen atom link the molecules to form a 1-D structure. In complexes 3–5, the difference in their structures is attributed to the different metal center ions with diverse coordination modes. The results reveal that the anions and metal ions have great impact on the final structures of the supramolecular architectures. The relationships between the structures and luminescent properties were investigated in detail.