Synthesis of a new tetrapyridyl ligand and the characterization of three distinct metal- and hydrogen-bonding conformations

The design, synthesis, and complexation characteristics of the ligand 1,2,4,5-tetrakis-(2'-pyridylethynyl)benzene are described. Three distinct essentially planar conformations are demonstrated. Conformational flexibility allows the ligand to adopt an "in-in" conformation and complex silver(l) cations. On self-assembly with resorcinol, the ligand adopts an "out-out" conformation to accommodate the larger resorcinol molecule with pyridyl-hydroxyl hydrogen bonding. In contrast, an "in-out-in-out" conformation is adopted on complexation with 2,7-dinitrofluorenone through weak hydrogen bonds.