Alternating phenylene and furan/pyrrole/thiophene units-based oligomers: A computational study of the structures and optoelectronic properties

Highlights: • Structure and properties of phenylene-furan, phenylene-pyrrole and phenylene-thiophene oligomers are explored computationally. • These oligomers form helical structures after a certain chain length. • Uv and CD spectra are reported. Structural and optoelectronic properties of phenylene-furan, phenylene-pyrrole and phenylene-thiophene oligomers are reported using density functional theory methods. Studies reveal that stabilities of conformers change with increasing chain length, and helical conformers are energetically feasible for large oligomers of the studied systems, due to stacking interactions between adjacent helical turns. Absorption spectra of helices are dominated by multiple number of electronic transitions other than the $S_0\to S_1$, involving orbitals other than the HOMO/LUMO. All studied helices are optically active having similar pattern of negative and positive peaks in the CD spectra.