First principal studies of spectroscopic (IR and Raman, UV–visible), molecular structure, linear and nonlinear optical properties of l-arginine p-nitrobenzoate monohydrate (LANB): A new non-centrosymmetric material

• The stable molecular geometry of LANB has been obtained by B3LYP and CAM-B3LYP level of theory using 6-31G∗ basis set.
• The dipole moment of LANB (4.124 a.u.) was found to be 3 times higher than urea.
• The absorption wavelength calculated by TDDFT study was found to be 268 nm.
• The energy gap (EHOMO–ELUMO) was calculated and found to be 4.3 eV.
• Total first hyperpolarizability (βtot) of LANB (1.630 × 10−30 esu) was found to be 4 times higher than prototype urea molecule.

In current work, the authors have been applied the density functional theory (DFT) using B3LYP and CAM-B3LYP exchange–correlation functional with 6-31G∗ basis set on l-arginine p-nitrobenzoate monohydrate (LANB) molecule for the first time to optimize its geometry and study the spectroscopic, electronic structure, nonlinear optical properties. Vibrational modes were found in good agreement with experimental reports. The calculated UV spectra by B3LYP/6-31G∗ and CAM-B3LYP/6-31G∗ level of theory shows an electronic transition at ∼268 nm (4.63 eV) and 264 nm (4.70 eV) respectively. To explain the charge interaction taking place within the molecule highest occupied molecular orbital and lowest unoccupied molecular orbital were analyzed and their calculated energy gap was found to be 4.3 eV with an oscillatory strength 0.3796 at B3LYP/6-31G∗ level of theory. The dipole moment (μtot), average and anisotropy of polarizability (αtot, Δα) and static and total first hyperpolarizability (β0, βtot) values were calculated. The value of μtot and βtot are found to be 4.124D and 1.630 × 10−30 esu and 4.127D and 1.133 × 10−30 esu using B3LYP/6-31G∗ and CAM-B3LYP/6-31G∗ functional respectively. The value of βtot is >4 and >3 times higher than prototype urea molecule calculated at both level of theory, respectively. The molecular electrostatic potential (MEP), frontier molecular orbital’s (FMOs), global reactivity descriptors and thermodynamic properties are also calculated and discussed. The properties of LANB calculated at B3LYP are in good correlation with experimental than the CAM-B3LYP level of theory. The obtained results show that LANB molecule can be treated as a good candidate for nonlinear optical devices.

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