Exploring the ON/OFF nonlinear optical (NLO) response in tetracene-based chromophores: A DFT study on solvent and frequency-dependent NLO properties for switching applications

Tetracene-based nonlinear optical (NLO) materials are an ambient field of interest in optoelectronic technology. Inspired by this material, we theoretically designed D-D-A framework molecules (ZO and ZO-1 to ZO-16) with auxiliary donor and acceptor screening of solo tetracene linear surface and investigated their reactivity, electrical properties, solvent-dependent optical and ON/OFF NLO properties utilizing DFT simulations. The CPCM and IEFPCM model is used to examine how entire spectrum of medium polarity, ranging from less polar to more polar solvents (chloroform (epsilon = 4.71) < tetrahydrofuran (epsilon = 7.43) < DMSO (epsilon = 46.83 < water (epsilon = 78.36)) affect the optical absorption and NLO characteristics (beta(tot), alpha(tot), and mu(tot)) of suggested compounds (ZO and ZO-1 to ZO-16). Furthermore, natural bond orbital analysis (NBO) and topological analysis (MEP, ELF, and LOL) were used to explain the NLO results. Regarding the charge transfer robustness, ZO-9, a promising tetracene derivative, is identified as an appealing second-order NLO candidate, with the lowest energy gap (1.642 eV) and largest lambda(max) (546.692 nm) among all investigated derivatives. Moreover, the solvent-dependent optical absorption spectrum shows that polar solvent (THF) alleviates the lambda(max) from 273.081 nm to 707.511 nm in ZO-11. Similarly, solvent also influences the NLO properties in all designed compounds, especially in ZO-9, which displayed giant beta(total) = 7.244 x 10(5) in chloroform, 8.640 x 10(5) in THF, 1.153 x 10(6) in DMSO, and 1.180 x 10(6) in water as well as in gas (1.993 x 10(5)). Additionally, the results of the second harmonic generation (SHG) beta(-2 omega, omega, omega) and the electro-optical Pockels effect (EOPE) beta(-omega,omega,0) computed at the frequencies of omega = 1064 nm (0.0428 au) and omega = 532 nm (0.0856 au) validates that all tetracene based derivatives are excellent NLO candidates for laser working condition and switching applications.