Rational design of multi-sided Y-shaped triazine derivatives with enhanced NLO response via charge transfer dynamics and solvent engineering
摘要
The exploration of triazine derivatives in nonlinear optics (NLO) has gained remarkable momentum in recent years. Their distinctive structural framework, featuring donor-acceptor systems connected by a π-conjugated bridge, has placed them at the forefront of advanced material innovation. We have conducted a theoretical study on two series of triazine-based NLO systems: symmetrical (1 S to 4 S) and asymmetrically substituted (1 A to 4 A) triazine derivatives, employing density functional theory (DFT). Among all the derivatives, 4 A exhibits the highest linear isotropic (αiso) and anisotropic polarizability (αaniso) as 104.1 × 10− 24 esu and 85.65 × 10− 24 esu, respectively. Furthermore, the asymmetrically substituted 4 A, showcases the largest static third-order NLO polarizability < γ > value of 716.6 × 10− 36 esu, which is nearly 108 times higher than that of the prototype NLO molecule, para-nitroaniline, calculated under the same theoretical conditions. The solvent dynamics of the compounds indicate that < γ > values increase by ~ 2–3 times, underscoring that the conductor-like screening model (COSMO) tends to inflate the NLO response compared to the gas and implicit solvation phases. The dynamic < γ > value for the top-performing NLO system, 4 A, was computed over a broad spectrum of laser wavelengths (1907 –489 nm). For the EFISHG process, the < γ > is observed to be 565.29 × 10− 36 esu and 648.27 × 10− 36 esu at 1907 nm and 1500 nm, respectively. TD-DFT calculations reveal the lowest transition energy of 3.564 eV, significantly enhancing the NLO efficiency of 4 A. The frontier molecular orbitals (FMOs) indicated a decrease in crucial orbital energy gap due to influence of donor-acceptor attached to the triazine core, with values ranging between 6.68 eV-5.38 eV. Our findings suggest that the designed triazine-based NLO systems hold great promise, likely evoking interest among researches in the optoelectronics domain. potentially sparking interest among researchers in the field of optoelectronics.