Self-assembled structures of bent-shaped π-conjugated compounds: effect of siloxane groups for nano-segregation

Abstract

Controlling nanostructures of organic compounds is an essential issue for optimization of functions such as ferroelectricity, and mass transport and carrier transport properties. The competition and interplay of various intermolecular interactions play key roles in the formation of fine structures. Herein, we discuss the tuning of layer and columnar structures of polar bent-shaped molecules. Two types of bent-shaped π-conjugated compounds were synthesized. While alkenyl-terminated compound 1 forms layered assemblies, disiloxy-terminated compound 2 forms nanofibres. The bulky disiloxane units should contribute to the decrease of crystallinity and the inhibition of two-dimensional layer structures. The morphology of the columnar self-assemblies of compound 2 is quite different from that of the layered aggregates of compound 1. Furthermore, the morphology of the equimolar mixture 1/2 is changed in relation to the aggregation rate. The introduction of the bent-shaped skeleton and bulky disiloxane units successfully tunes the nanostructures. These results suggest the utility of the bent-type molecular shape and oligosiloxane units to form fine nano-segregated structures.