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Graphical abstract:

The geometries, electrostatic potential, Mulliken charge analysis, Natural Bond Orbital analysis and polarizabilities of propyl-para-hydroxybenzoate were calculated using B3LYP functional with 6-311++G(d,p) basis set. The calculated geometries are well matched with the experimental values. The Mullliken atomic charge analysis shows that the eventual charges are contained in the molecule. The NBO analysis explains the intramolecular charge transfer in the PHB molecule. The bonding features of the molecule were analyzed with the aid of Hirshfeld surface analysis. The frontier molecular orbital analysis showed the charge transfer obtained within the molecule. The calculated hyperpolarizability of the PHB molecule was 6.977E −30esu and it was 8.9 times that of standard urea molecule.

Ethyl-para-hydroxybenzoate (EHB) single crystals have been grown by slow evaporation solution technique (SEST) using methanol as a solvent. The grown crystal was subjected to single crystal X-ray diffraction analysis, confirming that the crystal belongs to monoclinic structure. The grown crystal was characterized by powder X-ray diffraction analysis. The functional groups present in the EHB crystal have been identified using FTIR spectrum analysis. The laser damage threshold of EHB crystal was measured. The mechanical strength of the grown EHB crystal was measured using Vickers microhardness, no cracks have been observed up to 100 g of load. The optical transparency of the grown EHB crystal has been measured by UV-Vis-NIR spectrophotometer. The refractive index of grown EHB single crystal is 1.6610. The dielectric permittivity and dielectric loss of the EHB single crystal were studied as function of frequency and temperature. The thermogravimetric analysis (TG) and differential thermal analysis (DTA) were studied. The melting point of EHB was 123˚C. The luminescence behavior of EHB single crystal has been analyzed by photoluminescence analysis.