2D Multilayered π-stacked conjugated polymers based on a U-turn pseudo-geminal [2.2]paracyclophane scaffold

Abstract

4,15-Diethynyl, diethenyl and dihalo-substituted [2.2]paracyclophanes were explored as monomers to prepare polymers consisting of conjugated units held in a multi-tiered stacked arrangement. The pseudo-geminal substitution pattern of the [2.2]paracyclophane core affords a U-turn at the end of each tier in the polymeric architecture. This two-dimensional assembly of conjugated chains is similar to the organization of segments of conjugated polymers in the solid state. The broad fluorescence emission and large Stokes shift of the polymers compared to model unstacked linear analogs suggest that the excited state of the polymer undergoes energy transfer with mixing of π-orbitals to afford a “phane” electronic state. The magnitude of the Stokes shift of the polymers relative to the isomeric pseudo-parapolymers, in which stacking is limited to just the terminal rings of each tier, indicates the importance of the extended nature of the overlap of conjugated units on their electronic structure.