A physico-chemical approach to study the experimental and theoretical properties of l-ornithine monohydrochloride: An organic nonlinear optical material

Abstract

In the current work the authors report the experimental and theoretical investigation on l-ornithine monohydrochloride (LOHCL). Single crystals of LOHCL were grown by slow cooling technique and its crystal system was confirmed by powder X-ray diffraction analysis. The crystalline perfection was evaluated by high-resolution X-ray diffraction analysis which indicates that the crystalline perfection of the grown crystal is fairly good. Vibrational modes of LOHCL were identified by experimentally recorded and theoretically calculated FT-Raman and IR spectrums and found in good agreement with the reported values. Optical absorbance and reflectance were recorded by using UV–Vis–NIR spectrophotometer and various optical parameters were calculated. Detailed theoretical analysis was done by density functional theory (DFT) and time dependent TD-DFT using B3LYP/6-31G(d,p) level of method. HOMO-LUMO gap was found to be 6.09 eV whereas by experiment it is 4.8 eV. The excited state is more polar in comparison to ground state during excitation, dipole moment increases from 3.06 D in ground state to 3.90 D in excited state. The average polarizability (αtot), anisotropy of polarizability (Δα), first static and second order hyperpolarizability (βtot, β0, γ) were calculated. The total first hyperpolarizability of LOHCL is found to be 2 times higher than prototype urea molecule which is very promising for nonlinear optical applications.