The second-order nonlinear optical properties of novel triazolo[3,4-b] [1,3,4] thiadiazole derivative chromophores using DFT calculations

Many organic chromophores possess excellent nonlinear optical (NLO) properties. In spite of this, the performance of these chromophores in second-order nonlinear optical applications is limited due to the high symmetry and short dipole moment of the parent molecules, which can lead to a weak response or high susceptibility to molecular orientation dependency. To address this challenge, we designed a series of new [1,2,4] triazolo[3,4-b] [1,3,4] thiadiazole derivative chromophores C1-C7 and studied their second-order NLO property through density functional theory (DFT) by substitution of different donor functional groups. To this end, several hybrid functionals such as B3LYP/6-311 + + G (d, p), CAM B3LYP/6-311 + + G (d, p), and omega B97XD/6-311 + + G (d, p) were employed to carry out quantum chemical calculations, which included calculations and evaluations of frequency-dependent dipole moment, linear polarizability, and first hyperpolarizability values. In addition, natural bond orbital (NBO) analysis, intramolecular charge transfer (ICT) mechanism, electronic charge density analysis, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and vertical energy transitions are studied with time-independent and time-dependent level density functional theory. The results demonstrate that C7 is the most efficient chromophore among the other chromophores investigated, with a significant first hyperpolarizability value of 105,032.98 x 10(-34). This study provides insights into how to design second-order NLO active organic chromophores with better performance for optoelectronic applications.