Twisted intramolecular charge transfer and its contribution to the NLO activity of Diglycine Picrate: A vibrational spectroscopic study

• FT-IR and FT-Raman spectra of DGLP were recorded and analyzed.
• The Natural Bond Orbital (NBO) analysis explained the charge transfer interactions taking place within the molecule.
• The calculated first hyperpolarizability of DGLP is found to be 16 times that of urea.
• The HOMO–LUMO energy gap has been calculated.
• The value of band gap energy was estimated.

Single crystals of Diglycine Picrate (DGLP) were grown by slow evaporation technique and the vibrational spectral analysis is carried out using FT Raman and FT-IR spectroscopy, supported by Density Functional Theoretical (DFT) computations to derive equilibrium geometry, vibrational wavenumbers and first hyperpolarizability. The vibrational spectra confirm the existence of NH3+ in DGLP. The influence of Twisted Intramolecular Charge Transfer (TICT) caused by the strong ionic ground state hydrogen bonding between charged species making DGLP crystal to have the non-centrosymmetric structure has been discussed. The Natural Bond Orbital (NBO) analysis confirms the occurrence of strong intermolecular NH⋯O hydrogen bond. The HOMO–LUMO energy gap and the first order hyperpolarizability were calculated and it supports the nonlinear optical activity of the Diglycine Picrate crystal.

Vibrational spectral analysis of Diglycine Picrate is carried out using FT Raman and FT-IR spectroscopy, supported by Density Functional Theoretical (DFT) computations to derive equilibrium geometry, vibrational wavenumbers and first hyperpolarizability. The Natural Bond Orbital (NBO) analysis confirms the occurrence of a strong intermolecular NH⋯O hydrogen bonds. The HOMO–LUMO energy gap and the first order hyperpolarizability were calculated and it supports the nonlinear optical activity of the Diglycine Picrate crystal.Figure optionsDownload as PowerPoint slide