Coordinative, conformational and motional behaviour of triazine-based ligand strands on binding of Pb(II) cations

The coordinative behaviour of two bis(hydrazone)triazine-based ligands in the presence of Pb(II) was investigated. Free ligand, pincer-like and stick-like complexes' X-ray structures are described. The ligands adopt a pyridine-like coordinative behaviour for Pb(II)/ligand molar ratio equal to 1/2 and 1/1, and a pyrimidine-like coordinative behaviour for Pb(II)/ligand molar ratio equal to 2/1. The complexation processes are reversible and may be modulated by external stimuli. They generate conformational and motional behaviour through interconversion of three entities, free ligand, pincer and stick complex. (C) 2008 Elsevier Ltd. All rights reserved.