Quantum chemical investigation on molecular structure, vibrational, photophysical and nonlinear optical properties of l-threoninium picrate: an admirable contender for nonlinear applications

In this work, very first attempt has been made to investigate the electronic, spectroscopic and nonlinear optical properties of l-threoninium picrate (LTHP) molecule by exploiting vital computational methods such as HF, B3LYP and range-separated functionals (CAM-B3LYP and LC-BLYP) with 6-31G* basis set. The calculated values of IR and Raman vibrational frequencies were found to be in a good agreement with experimental results. Time-dependent density functional theory has been applied to calculate the electronic and photophysical properties such as excitation energy, dipole moment and frontier molecular orbital (FMO) energies of LTHP. The excitation energy value calculated by CAM-B3LYP is at ~ 351 nm that in close harmony with experimental value (i.e., 356 nm). Total/partial DOS was determined using GGA/BLYP. The values of μ_tot, α_tot, Δα, β₀ and β_tot were estimated and discussed. The μ_tot and β_tot are found to be 3 and 51 times higher than urea molecule, respectively. The FMOs, molecular electrostatic potential and global reactivity descriptors were also calculated and discussed. All these results suggest that the LTHP would be a good candidate for optoelectronic applications.