Directional growth, physicochemical and quantum chemical investigations on pyridinium 2-carboxylate: 4-nitrophenol (P2C4N) single crystal for nonlinear optical (NLO) applications

An organic nonlinear optical (NLO) single crystal of pyridinium 2-carboxylate: 4-nitrophenol (P2C4N) was grown by the Sankaranarayanan-Ramasamy (SR) method using the (1 1 -1) plane. A transparent crystal of size 180 mm in length and 10 mm in diameter was grown over a period of 60 days. The lattice parameters and the molecular structure of the grown crystal were confirmed by single crystal XRD and nuclear magnetic resonance (NMR) spectrum analysis, respectively. The crystalline perfection of the SR method-grown crystal was evaluated by HRXRD analysis; from the observed results, it is evident that the crystal quality is quite good. UV-Vis-NIR analysis shows that the SR method-grown crystal has good transparency (90%) in the visible and NIR regions. The band gap of the title crystal was estimated by the Tauc's plot method and was found to be 3 eV. The title material is thermally stable up to 141 degrees C, and it demonstrates positive photoconductive behaviour. Vickers microhardness studies revealed that the grown crystal can be categorized as a soft material. The laser damage threshold of P2C4N was found to be 2.9 GW cm(-2), which shows that the grown crystal possesses excellent resistance to high power radiation. Z-Scan studies proved that the grown crystal possesses self-defocusing effects and negative nonlinearity. The theoretical spectra were calculated using the B3LYP/cc-pVTZ basis set and were compared with the experimental FT-IR and FT-Raman spectra of the title molecule. The full vibrational assignments of the observed spectra have been proposed by normal coordinate analysis (NCA) followed by force-field calculations. Quantum chemical studies, such as optimized geometry, HOMO-LUMO, natural bonding orbital (NBO) analysis, AIM analysis, hyperpolarizability and molecular electrostatic potential (MEP) were performed for the title molecule. The results are discussed in detail

Bioactive Small Molecule, Piperazinium Bis(4-Hydroxybenzenesulphonate) upon Spectral Investigation, Hirshfeld Surface Analysis, Molecular Docking and ADMET Prediction: A Complement DFT Calculations

Piperazinium bis (4-hydroxybenzenesulphonate) (P4HBS) was studied using FT-IR, FT-Raman, UV spectra, and quantum chemical calculations. To obtain the geometry of the molecule, computational methods were used with the Gaussian’09w package and B3LYP/cc-pVTZ as the basis set. The stretching wave number of hydrogen bond donor NH2+ and hydrogen bond acceptor SO3− is red shifted due to protonation, according to vibrational analysis. Frontier molecular orbital analysis was used to confirm the molecule’s molecular reactivity and kinetic stability. The electronic transition observed in the UV-visible spectrum, which was measured experimentally, was identified using TD-DFT. MEP plot, Fukui function. Natural population analysis confirm that OH groups and SO3 groups are electrophilic attack sites, while hydrogen atoms in the Piperazinium ring are nucleophilic attack sites. The Independent Gradient Model (IGM) and Hirshfeld surface analysis were used to determine the weak van der Waals and strong intermolecular hydrogen bonding interactions, respectively. The antifungal activity against the fungus Candida albicans and Aspergillus flaves was determined by the disk diffusion technique. Through binding energy, molecular docking studies were performed to identify the effective lead compound against the C. albicans fungal pathogen. ADMET properties with improved pharmacokinetic properties were predicted.</p