Influence of Peripheral Modification of Electron Acceptors in Nonfullerene (O-IDTBR1)-Based Derivatives on Nonlinear Optical Response: DFT/TDDFT Study

Fullerene-based organic compounds have been reported as useful materials with some limitations; nonetheless, fullerene-free compounds are primarily considered to be the most substantial materials for the development of modern technology. Therefore, in this study, a series of compounds (<b>NFBC2</b>-<b>NFBC7</b>) having an A<i>-</i>π-D architecture were designed for the first time from a synthesized nonfullerene (<b>O-IDTBR</b>) compound by changing different acceptor groups. The synthesized nonfullerene (<b>O-IDTBR1</b>) compound and its designed derivatives were optimized with frequency analyses at the M06/6-311G(d,p) level. These optimized structures were further characterized by different quantum chemical approaches. The study required that the designed compounds possess a low energy gap in comparison to that of <b>O-IDTBR1</b> (2.385 eV). Moreover, density of state (DOS) calculations supported the FMO analysis and displayed charge transfers from the HOMO to the LUMO in an effective manner. The λ_max values of the investigated chromophores were observed to be greater than that of the reference compound. Amazingly, the highest amplitude of linear polarizability ⟨α⟩ and first (β_tot) and second hyperpolarizability values were achieved by <b>NFBC6</b> at 1956.433, 2155888.013, and 7.868 × 10⁸ au, respectively, among all other derivatives. Effective NLO findings revealed that nonfullerene-based derivatives may contribute significantly to NLO technology.