Structural, Optical, and Dielectric Properties of 2,5-DCAP Single Crystals

Abstract

The organic nonlinear optical (NLO) material 2,5-Dichloroanilinium Picrate (2,5-DCAP) was synthesized and grown as a single crystal using the slow solvent evaporation method. The structure was confirmed via single-crystal X-ray diffraction, revealing a monoclinic system with non- centrosymmetric space group Cc, suitable for second harmonic generation (SHG). Optical studies using UV-Vis-NIR spectroscopy demonstrated excellent transparency and a UV cut-off wavelength at 215 nm, with an optical band gap of 5.77 eV. SHG analysis confirmed efficient frequency doubling, with an SHG output 1.2 times that of potassium dihydrogen phosphate (KDP), indicating phase-matchable behavior. Vickers micro- hardness testing revealed load-dependent mechanical properties, with the material classified as soft based on the work hardening coefficient. Di- electric measurements indicated low dielectric constant and loss at high frequencies, reflecting high optical quality and low defect density. The combined structural, optical, mechanical, and dielectric properties suggest that 2,5-DCAP is a promising candidate for photonic and electro-optic device applications.