First order molecular hyperpolarizabilities and intramolecular charge transfer from vibrational spectra of NLO material: 2,6-dichloro-4-nitroaniline

Vibrational spectral analysis of the non-linear optical (NLO) material, 2,6-dichloro-4-nitroaniline (DCNA) has been carried out by using FT-IR and FT-Raman spectroscopic techniques. The Hartree-Fock(HF) and Density Functional Theoretical (DFT) computations have been performed at 6-311++G** level to derive equilibrium geometry, vibrational wavenumbers, intensities and first order hyperpolarizability. The optimized geometry, various bonding features and harmonic vibrational frequencies of DCNA have been investigated. Vibrational bands to the various structural groups and their significance were investigated by analyzing the vibrational spectra. Vibrational analysis reveals that simultaneous IR and Raman activation to the phenyl ring modes also provide evidence for the charge transfer interaction between the donors and acceptor can make the molecule polarized and the intramolecular charge transfer interaction must be responsible for the NLO properties of DCNA. The Mulliken atomic charge analysis was also made in the present study. The dipole moment (μ), polarizability (α) and the hyperpolarizability ( ) values of the investigated molecule have been computed using HF and B3LYP methods.