Facile synthesis of new divergent imidazole-containing ligands for a 1-D cobalt(II) coordination polymer

Abstract

A new divergent ligand (3a) containing a triaryl core and two imidazole side-arms has been designed and synthesized. The synthetic procedure utilizes a two-step strategy, i.e. the Kröhnke condensation, followed by a Cu-catalyzed Ullman-type coupling. This synthetic strategy allows the facile introduction of various substituents on the 4-position of the central pyridine in the ligands, which was proved by the synthesis of a ligand analog (3b). The new ligands were well characterized by spectroscopic methods and X-ray structural analysis was carried out for 3a. Reaction of 3a with Co(NCS)2 by a layering method afforded single crystals of a coordination polymer 5, which was structurally characterized by X-ray diffraction. 5 is composed of two ligands and one Co(NCS)2 in its asymmetric unit and features a 1-D coordination polymer with nano-scale metallomacrocyles. The structure of 5 is found to be quite different from all known coordination networks composed of Co(NCS)2 and closely related divergent ligands.