New Aryl‐Substituted 2,2′‐Bithiophenes: Synthesis, Optoelectronic Properties and DFT Studies

Abstract

Phenyl‐ and thien‐2‐yl‐[2, 2′‐bithiophen]‐5‐yl)(thiophen‐2‐yl)methanones were synthesized by the condensation of 2‐thienyldithioester with the corresponding methyl ketones followed by cyclization with 2‐bromoacetylthiophene. Also, condensation of 2‐thienyldithioester with methyl ketones followed by treatment with methyl iodide gave β‐thien‐2‐yl‐β‐methylthio‐α,β‐unsaturated ketones, which reacted with the Simmons‐Smith reagent to give corresponding 4‐phenyl‐ and thien‐2‐yl‐2,2′‐bithiophenes. The optoelectronic properties of these bithiophene derivatives were studied by UV‐Vis absorption, fluorescence spectroscopy and cyclic voltammetry. The lowest‐energy conformations of these new compounds in the ground and first excited states, the electronic origins of their UV‐Vis absorption and fluorescence emission bands, and related frontier molecular orbital (FMO) properties were elucidated by density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations. Furthermore, these aryl‐substituted bithiophenes were treated with anhydrous ferric chloride to undergo oxidative polymerization, and the fluorescence properties of the resulting polymeric products are also reported herein.