Organic donor–acceptor (D–A) complexes with exceedingly narrow electronic band gaps are emerging as pivotal components for next-generation optoelectronic technologies. Here, we carry out an integrated quantum-chemical characterization of five freshly engineered D–A systems manifested through systematically varied donor, acceptor, and -bridge motifs. The optimized equilibrium geometries were refined at the B3LYP/6-31G(d,p) level, and pivotal electronic attributes were scrutinized by frontier molecular orbital inspection, energy-gap computation, stationary dipole moment analysis, and time-dependent density functional theory (TD-DFT) assessments of simulated ultraviolet–visible absorbance. Energy-gap values were calculated to span 1.43–2.98 eV, with the most contracted band gap of 1.43 eV appearing in the assembly of a julolidine donor, an extended selenophene linker, and an acceptor scaffold of cyanovinylene. Systematic evaluation of structure against measured property underscores the productive synergy between pronounced push–pull configuration and -expansion, which collectively refine the HOMO–LUMO separation and tailor the spectral response. The resultant guidelines, quantitatively anchored in molecular architecture manipulation, constitute a solid foundation for engineering high-efficiency, narrow-gap organic semiconductors engineered for both refined photovoltaic cells and near-infrared optoelectronic components.
Muslim et al. (Mon,) studied this question.