Temperature-dependent IR and dielectric properties, and DFT calculations (FMOs and ELF), of 2-amino-3-nitropyridinium hydrogen sulfate monohydrate

This study investigates the structural, temperature-dependent IR and dielectric properties, along with the DFT calculations of 2-amino-3-nitropyridinium hydrogen sulfate monohydrate (abbreviated as 2A3NP) (C₅H₆N₃O₂)·HSO₄·H₂O, a compound with potential nonlinear optical applications. Single-crystal X-ray diffraction analyses confirm an orthorhombic, non-centrosymmetric structure, stabilized by hydrogen bonding between the organic cation, hydrogen sulfate anions, and water molecules. Temperature-dependent IR spectroscopy reveals shifts in vibrational modes associated with hydrogen bonding, reflecting molecular dynamics and thermal effects. Dielectric analysis shows temperature-sensitive conductivity, with proton hopping and relaxation processes. DFT calculation provides insights into the electronic structure, highlighting the HOMO-LUMO gap of 3.42 eV and electron localization, which aligns well with the optical results. These findings deepen our understanding of the temperature-dependent vibration bands and dielectric behavior of 2A3NP-based compounds and emphasize the compound's potential in electronic and optical applications where stability and controlled conductivity are essential.