Molecular structure, vibrational, photophysical and nonlinear optical properties of L-threoninium picrate: A first-principles study

In this work, different computational methods such as HF, B3LYP, range separated functionals (CAM-B3LYP and LC-BLYP) with 6-31G* basis set were applied to investigate the electronic, spectroscopic and nonlinear optical properties of L-threoninium picrate (LTHP) molecule for the first time. The calculated values of IR and Raman vibrational frequencies were found to be in a good agreement with the 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 molecule. The excitation energy value calculated by CAM-B3LYP is found to be at 351 nm which is in close agreement with the experimental values. The total/partial DOS (T/PDOS) was determined using GGA/BLYP. The total dipole moment ({\mu}tot), static total and anisotropy of polarizability ({\alpha}tot, {\Delta}{\alpha}) and static first hyperpolarizability (\b{eta}0, \b{eta}tot) values were calculated and compared with the reference compound. The {\mu}tot and \b{eta}tot are found to be 3 and 51 time higher than urea molecule respectively. The FMOs, molecular electrostatic potential (MEP), global reactivity descriptors were also calculated and discussed. All these results suggest that the L-threoninium picrate would be a good candidate for optoelectronic device applications.