Mesogenic Coordination Polymers Based on Ru2(II,II)-Paddle-Wheel Units Exhibit High Electrical Conductivity

Abstract

We report the synthesis, characterization and properties of a series of coordination polymers (CP) in which paddle-wheel diruthenium (II,II) tetracarboxylate units are linked by tetrazine as axial ligand, a combination aimed to promote electron delocalization along the CP axis. The use of bulky equatorial 3,4,5-tri(alkoxy)benzoates (B3OCn, n=10, 14, 18) warranted the columnar liquid crystalline nature of the targeted Ru2(B3OCn)4tz CP, which allowed their processing as extruded fibers. The liquid crystalline phases of both the polymers and their Ru2(B3OCn)4 precursors have been studied by means of polarized optical microscopy, differential scanning calorimetry, X-ray diffraction and small and wide angle X-ray scattering. We suggest herein some models for the supramolecular organization in the hexagonal and rectangular columnar mesophases these CP exhibited. Extrusion form the CLC phase lead to fibers in which the columnar axes were colinear with the fiber axis at a macroscopic scale. Electrical conductivity measurements on these fibers revealed high values (0.4 S/m) for the targeted CP.