Rational design of BODIPY-carbazole analogues in the context of D-π-A approach for facile charge transport: A DFT/TD-DFT study

Abstract

In this paper, we have examined the influence of torsional rigidity on the optoelectronic properties by imposing furan, pyrrole and thiophene unit on the BODIPY-carbazole based donor-acceptor systems employing density functional theory (DFT) formalism. We have designed 12 small conjugated molecules based on the donor (carbazole)-acceptor (BODIPY) approach using furan, pyrrole and thiophene unit as the bridging units. To study the torsional rigidity imparted by the bridging units we have performed potential energy surface (PES) analysis. Our study explores that among the bridging units furan and thiophene impart maximum and minimum rigidity on the systems respectively. Different parameters viz. distortion energy (ΔEdis), HOMO-LUMO gap (ΔH−L values), ionization potential (IP), electron affinity (EA), bond length alteration (BLA) parameters, dipole moment values, reorganization energies for holes (λh) and electrons (λe), electronic coupling matrix element (V), charge transfer rate (kct), hopping mobility (μhop), radiative decay rate (kr) etc. have been calculated. The absorption and emission spectra of the BODIPY based compounds have been studied using TD-DFT. NTO analysis have also been performed for the dominant electronic transitions. Our calculations predict that compounds possessing pyrrole unit as the bridging unit and compounds in which BODIPY unit is meso substituted with pyrrole unit possesses greater amount of conjugation and as a result exhibit facile charge transport.