Design and Synthesis of New Bithiophene Based Planar AIE Red Light Emitters: A Detailed Theoretical and Experimental Analysis**

Abstract

Bithiophene core with −CN substituted pyrazole and imidazole side chains yielding B1, B2, and B3 have been designed and synthesized viz Schiff's base condensation reaction. Molecules, at their solid-state exhibited red-light emission supporting AIE mechanism. The series exhibited the highest relative quantum yield of value 18.66 % by B1 with the lowest recorded for B3 exhibiting 2.4 %. DFT results reveal the synthesized molecules at their optimized ground state adopt a planar structure. Theoretical calculation further validates the molecules to adopt a slip-stacking type of molecular packing arrangement at its condensed state, conducive for AIE. A large π-π stacking distance between the lattice plane of 3.4 Å, 3.6 Å and 3.5 Å possessed by B1, B2, and B3 respectively, favors AIE. Computational calculation on electron and hole reorganization energy reveals the effective role of two −CN groups in altering the hole mobility in comparison with the other molecules in the series. © 2022 Wiley-VCH GmbH.