Impact of extended π-conjugated acceptor moieties on non-linear optical behavior in polar medium for optimal designed 4,4-dimethyl-4H-indeno[1,2-b] thiophene based materials

In the current study, the organic compounds (D2-D9) with D1–π–D2–π–A configuration were designed by structural modeling with various end-capped acceptor moieties for nonlinear optical (NLO) study. TD-DFT/DFT approaches at CAM-B3LYP/6-311G(d,p) level were accomplished to investigate the NLO behavior of these compounds. For this, various analyses: frontier molecular orbitals (FMOs), density of states (DOS), UV–Vis absorption, natural bond orbitals (NBOs), transition density matrix (TDMs) and non-linear optical (NLO) investigations were performed. These findings revealed that all designed chromophores exhibited comparable band gaps (3.962–4.182 eV) and absorption spectra (λ max = 441.6–460.7 nm) with reference chromophore (band gap = 4.008 eV). An efficient charge transfer from central core in HOMO was transferred towards terminal acceptors in LUMO that was also supported by DOS and TDM maps. Among all studied chromophores, the significant linear and nonlinear polarizability properties were examined in D5 (<α>=2.213 × 10-22 esu), D6 (βtot = 3.339 × 10-28 esu) and D4 (γ tot = 3.068 × 10-33 esu) chromophores. The NLO results indicated that the designed compounds (D5, D6 and D4) possess promising NLO behavior via effective charge delocalization. It is inferred that the current computational work might be helpful for further developments in non-linear optic field.