Structural, spectral and nonlinear optical analysis of cytosinium dihydrogen phosphite crystal

Cytosinium dihydrogen phosphite (CDHP), a semiorganic crystal has been grown by slowly evaporating the solvent. It crystallizes in triclinic system with non-centrosymmetric space group P1. Optical transmittance study of CDHP shows its transmitting ability from 277 to 1100 nm. Fourier Transform Infrared and Raman spectral analysis establishes the vibrations of functional groups present in CDHP. Presence of H₂PO₃⁻ ion’s characteristic vibrations ensures the formation of CDHP crystal. Nuclear Magnetic Resonance (NMR) spectral analysis elucidates the proton and carbon environment and the molecular structure of CDHP has been confirmed. Second harmonic generation (SHG) efficiency has been measured using Kurtz and Perry powder method. SHG efficiency of CDHP is 0.88 times that of KDP. Photoluminescence emission spectrum suggests suitability of CDHP crystal to design UV fluorescence detection, UV filter and optoelectronic devices. The third order nonlinear optical (NLO) parameters have been analysed by Z-scan technique which reveals the self-defocusing and saturable absorption nature of CDHP. The third order NLO susceptibility (χ³) is determined as 1.0633 \(\times\) $\times$ 10^–7 esu. Presence of N–H…O and O–H…O hydrogen bonds in CDHP crystal is the reason for this high χ³ value. The results reveals that the crystal can be used in laser Q-switching, optical sensors and optoelectronic applications. Thermal stability of CDHP is analysed by thermogravimetric and differential thermal analysis (TG/DTA).