Introducing the various electron withdrawing functions in trigging the optical nonlinearity of benzodithiophene based chromophores: A quantum chemical approach

The nonlinear optical (NLO) characteristics exhibited by organic compounds hold significant value in the realm of photonics and optoelectronics applications. Herein, the Density Functional Theory method at MPW1PW91/6-311G (d,p) functional was utilized to evaluate the electronic and NLO behavior of novel compounds i.e., MTPBR1 having A-π-D-π-A and MTPBD2-MTPBD9 with D1-π-D2-π-A configurations. Quantum chemical computations revealed that structural tailoring of all the designed chromophores demonstrate reduced bandgaps with greater absorption properties than MTPBR1. The efficacy of charge transfer from the donor to the acceptor through a spacer was investigated using frontier molecular orbitals calculations. These calculations were substantiated by analyses of density of states and transition density matrices. Natural bonding orbitals indicated molecular stability in designed molecules due to hyper-conjugative interactions and extended conjugation. Among all the derivatives, MTPBD8 exhibited the lowest energy bandgap (1.891 eV) with bathochromic shift of 723.868 nm in chloroform and 546.688 nm in gaseous phase, and the highest global softness of 0.529 eV−1. MTPBD5 displayed the highest dipole moment (µtot) at 22.815 D. MTPBD2, MTPBD3, MTPBD5 and MTPBD8 demonstrated consistent linear polarizability 〈α〉 at 3.4 × 10−22 esu. Notably, MTPBD8 calculated the highest first and second hyperpolarizability (βtot, γtot) at 9.6 × 10–27 and 4.302 × 10−32 esu, respectively. To conclude, the novel chromophores, particularly MTPBD8, showed remarkable NLO properties, demonstrating their potential use in advanced nonlinear optical devices.