Characterization of a newly synthesized organic nonlinear optical crystal: Benzoyl valine

Herein the synthesis and the crystal growth of benzoyl valine (BV), an organic nonlinear optical (NLO) material for frequency conversion was grown by slow evaporation solution growth technique at room temperature has been reported. The compound was prepared by Stockman method of benzoylation. The solubility curve shows linear nature up to a temperature of 313 K. XRD study reveals that the crystal belongs to monoclinic system with P2₁ non-centrosymmetric space group. The fundamental vibrational frequency of various functional groups (400-4000 cm^-1) in the crystal was determined from FTIR analysis. ¹H and ¹³C NMR spectral studies reveal the presence of proton and carbon network in the grown crystalline sample. The optical behaviour of the crystal was ascertained by optical UV absorption spectral studies. The UV cut off region (λ_max) lies around 200 nm and the crystal is absolutely transparent from 220-800 nm suggesting its application as NLO material. The thermal stability of the crystal was determined by thermogravimetric and differential thermal analyses. Laser damage threshold of BV was found to be 0.34 GW/cm² and hence BV can be used in frequency doubler system. Photoconductivity study of BV revealed negative photoconductiviting nature of the sample. The microhardness studies confirm that BV has a moderate Vickers hardness number (VHN) value in comparison to the other organic NLO crystals.