Growth, and characterization of the nonlinear optical crystal 2’, 3’-Di-O-acetyl-5’-deoxy-5-fluoro-N4- (pentyloxycarbonyl) cytidine: structural, optical, thermal, electrical, and molecular docking studies
摘要
A novel organic nonlinear optical (NLO) crystal, 2’,3’-Di-O-acetyl-5’-deoxy-5-fluoro-N4-(pentyloxycarbonyl) cytidine (DODFN), has been successfully synthesized and grown for the first time using a slow evaporation technique. This work uniquely combines experimental nonlinear optical, thermal, electrical, and mechanical characterization with density functional theory (DFT) analysis to establish DODFN’s potential in photonic device applications. Single crystal X-ray diffraction analysis revealed that DODFN crystallizes in the monoclinic system with a non-centrosymmetric space group P2₁, essential for second-order NLO activity. Powder XRD confirmed the crystalline nature with sharp peaks, particularly a prominent (100) reflection at 2θ ≈ 9.5°, indicating high phase purity. The presence of functional groups was verified using FTIR spectroscopy. UV–Visible absorption studies showed an optical transparency window in the range of 220–800 nm, with a lower cutoff wavelength at 228 nm, and an optical bandgap of 5.43 eV, confirming its suitability for photonic applications. Thermal stability up to 180 °C was confirmed using TGA/DTA analysis. AC conductivity increased from 2.1 × 10⁻⁸ to 9.3 × 10⁻⁷ S/m with frequency, while DC conductivity followed Arrhenius behavior with an activation energy of 0.56 eV. The Vickers microhardness test revealed that hardness increased with load, indicating reverse indentation size effect (RISE). Second harmonic generation (SHG) studies via the Kurtz–Perry powder method demonstrated a relative efficiency of 0.7 times that of KDP, confirming its second-order NLO behavior. Furthermore, DFT-based quantum chemical calculations including molecular electrostatic potential (MEP), HOMO–LUMO analysis, and energy gap evaluation supported the molecule’s polarizability and charge distribution essential for NLO activity. With a HOMO energy of –6.6589 eV and a LUMO value of –1.6901 eV, the compound has a modest energy gap of 4.9688 eV, suggesting balanced stability and reactivity, according to the quantum chemical analysis based on frontier molecular orbitals. Its electron affinity (1.6901 eV) and ionization energy (6.6589 eV) indicate effective electron-donating and receiving properties. Both the chemical potential (–4.1745 eV) and electronegativity (4.1745 eV) exhibit a modest propensity to attract electrons. The compound is a strong electrophile with potential chemical reactivity, as evidenced by its global hardness of 2.4844 eV, softness of 0.4025 eV⁻1, and electrophilicity index of 3.5072 eV. Good solubility and interaction with polar biological systems are supported by the mild polarity indicated by the dipole moment of 2.0475 Debye. Moreover, the most active chemicals manner of binding to the target Carbonic Anhydrase II protein (PDB-ID: 6LUX) was investigated by molecular docking studies.