Symmetrically Disubstituted Bithiophene Derivatives of 1,3,4-Oxadiazole, 1,3,4-Thiadiazole, and 1,2,4-Triazole – Spectroscopic, Electrochemical, and Spectroelectrochemical Properties

• Published in: Journal of physical chemistry. C Vol. 118; no. 43; pp. 25176 - 25189
• Main Authors: Kurowska, Aleksandra, Kostyuchenko, Anastasia S, Zassowski, Pawel, Skorka, Lukasz, Yurpalov, Viacheslav L, Fisyuk, Alexander S, Pron, Adam, Domagala, Wojciech
• Format: Journal Article
• Language: English
• Published: American Chemical Society 30-10-2014
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp507838c

Electrochemical and spectroelectrochemical properties of a series of new penta-ring donor–acceptor compounds, comprising 1,3,4-oxadiazole, 1,3,4-thiadiazole, and 1,2,4-triazole central ring, symmetrically connected to substituted bithiophenes, were investigated. Aromaticity and electrophilic–nucleophilic traits of the aza-heterocyclic units, fostering inductive and resonance effects that translate to conjugation enhancement and electron (de)­localization, were found a major factor determining the key electron properties of ionization potential (IP) and electron affinity (EA) of these molecules. Replacing the alkyl thiophene substituent for an alkoxy one afforded certain control over the two parameters as well. All studied compounds were found to undergo electrochemical polymerization giving p- and n-dopable products, featuring good electrochemical reversibility of their oxidative doping process, as demonstrated by cyclic voltammetry and UV–vis–NIR, EPR spectroelectrochemistry. While electropolymerization of entities differing in the heterodiazole unit was found to conserve the EA value, the IP parameter of polymerization products was found to decrease by 0.6–0.7 eV, affording an asymmetric narrowing of the frontier energy levels gap. Aided by quantum chemical computations, the effects of structure tailoring of the investigated systems are rationalized, pointing to conscious ways of shaping the electronic properties of thiophene class polymers using synthetically convenient heterodiazole π-conjugated units.