Does oligomerization in fused thiophene affect reactivity and aromaticity?

Abstract

Reactivity and aromaticity of a few fused thiophene oligomers and their conformers are discussed in the light of density functional theory (DFT) and conceptual density functional theory. Reactivity parameters, such as hardness (η) and electrophilicity (ω), chemical potential (μ) and energy of the HOMO (highest occupied molecular orbital) have been studied. Oligomerization raises the E HOMO of the species, which in turn increases the reactivity of the oligomers. The absorption spectra of the species are analysed using TDDFT (time dependent density functional theory). The absorption peaks show red shift with increasing size of the oligomers. Aromaticity of the species is gauged by nucleus independent chemical shift (NICS). The out-of-plane component, (NICS zz) values advocate higher aromatic character at longer distance whereas, NICS supports the reverse.

A study of the global and local aromaticity of hetero[8]circulenes

“…The trend in CRE values suggests that the number of fused thiophene units correlates with a decrease in CRE values: thiophene unit ( c 2 to c 9 ; 0.08618β) > two thiophene units ( c 18 to c 25 ; 0.01153β) > three annulated thiophene units ( c 18 to c 25 ; 0.00177β). Our conclusions align with a study by Purkayastha et al, 51 who used the DFT method to study the ring stability of thiophene oligomers, confirming our findings about the local aromaticity of 1 . Similar behavior in local aromaticity is observed in 2 and 3 , suggesting that these compounds are primarily stabilized by the eight heterocyclic five‐membered units based on their CRE values.…”