Donor moieties with D–π–a framing modulated electronic and nonlinear optical properties for non-fullerene-based chromophores

Herein, a series of non-fullerene-based substantial chromophores (FHD1-FHD6) with a D-π-A framework was designed from a synthesized non-fullerene compound (FH) <i>via</i> structural tailoring with various donor moieties. The FH and its designed derivatives were optimized with frequency analysis at the M06/6-311G (d,p) level to confirm their true minima on potential energy surfaces. These optimized geometries were utilized to perform further analyses, such as absorption, natural bonding orbital (NBO), frontier molecular orbital (FMO), and nonlinear orbital (NLO) analyses at the aforesaid level. Quantum chemical study revealed that all the designed chromophores exhibited a lower band gap than that of the parent molecule with the exception of FHD3. Furthermore, density of states (DOS) analysis supported the findings from the FMO study, and this agreement revealed that the efficient charge was transferred from the HOMO to the LUMO. The NBO investigations disclosed that all the compounds comprised donor moieties with positive charges and acceptors having negative charges. Interestingly, π-conjugated linkers were also found with positive charges, showing an effective donating property. These NBO findings explicated that FHD1-FHD6 exhibited an efficient push-pull mechanism. The <i>λ</i> _max values of the designed chromophores were observed to be greater than the reference compound. The average polarizability 〈<i>α</i>〉, first hyperpolarizability (<i>β</i> _tot), and second hyperpolarizability 〈<i>γ</i>〉 values of FHD2 were found to be 2.170 × 10^-22, 3.150 × 10^-27, and 4.275 × 10^-32 esu, respectively, while all the other derivatives had been reported in the relevant range. Efficient NLO data revealed that FH-based derivatives may contribute significantly toward NLO technology.