Structure and Phase Transition of 4,7-Bis-(4′-cyano-biphenyl-4-yl)-[1, 10]phenanthroline

Abstract

4,7-Bis-(4′-cyano-biphenyl-4-yl)-[1, 10]phenanthroline (cnbiphphen) is synthesized from a palladium mediated coupling between 4-cyanobenzene boronic acid and 4,7-bis(4-bromophenyl)-[1,10]phenanthroline. The single crystal X-ray structure was measured at both 298(2) K and 90(2) K. The asymmetric unit of the title compound in the low-temperature phase, C38H22N 4 . HCCl3, is comprised of one cnbiphphen molecule and one chloroform solvent molecule. Additional symmetry relates one-half of the title compound to the other at room temperature. During cooling the structure experiences a reversible phase transition from A 2/a (different setting of C 2/c, with a and c exchanged to match lattice parameters of both phases) to P 21/c. The crystal packing of the title compound consists primarily of electronic charge interactions between the cyano moieties. The chloroform solvent mol-ecule is situated in a cavity between two phenanthroline systems and is associated to two nitrogen atoms of cnbiphphen molecules through Cl3C–H⋯Nphen van der Waals interaction. The synthesis, structure, analytical characterization, optical properties and phase transition of 4,7-bis-(4’-cyano-biphenyl-4-yl)-[1,10]phenanthroline is presented.