Spectral and electronic properties of π-conjugated oligomers and polymers of Poly (o-chloroaniline-co-o-toluidine) calculated with density functional theory

•DFT and TD-DFT calculations of poly(o-chloroaniline-co-o-toluidine).•Estimation of spectral and electronic properties like IPs, EAs, HOMOs, LUMOs and band gaps.•Correlation between the experimental and theoretical spectral properties.•Effect of donor-acceptor groups on the conductivity of the copolymer.

Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations have been carried out at the oligomers of poly(o-chloroaniline-co-o-toluidine)(POTOC), poly(o-chloroaniline)(POC) and poly(o-toluidine) (POT). This work discusses conductivity, structural parameters, spectral properties, electronic properties like IPs, EAs, HOMOs, LUMOs and band gaps of POTOC, POT and POC by the application of density functional theory to their oligomers up to eight repeating units. The simulated vibrational frequencies at B3LYP/6-31G (d) along with their assignments are correlated with experimental frequencies. The UV–vis spectra are simulated with TD-DFT 6-31G (+d p) level of theory. For polymeric studies, the electronic properties of oligomers were extrapolated through second degree polynomial fit equation. The calculated band gap of POTOC is 3.836 eV while those of POC and POT are 3.456 eV and 3.641 eV, respectively. The larger band gap, low delocalization of HOMO–LUMO orbital over entire frame work, lower extent of conjugation and hypsoochromic shift in UV–vis spectra of POTOC as compared to POT and POC showed that donor-acceptor concept is not playing any role in POTOC and its conductivity after doping might not be increased as compared to the respective homo-polymers.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide