Study of chemical reactivity and molecular interactions of the hydrochlorothiazide-4-aminobenzoic acid cocrystal using spectroscopic and quantum chemical approaches.

In this study, the molecular, electronic, and chemical properties of the drug hydrochlorothiazide (HCTZ) are determined after cocrystallization with 4-aminobenzoic acid (4-ABA). Analysis has been performed to understand how those variations lead to alteration of physical properties and chemical reactivity in the cocrystal HCTZ-4ABA. IR and Raman characterizations were performed along with quantum chemical calculations. A theoretical investigation of hydrogen bonding interactions in HCTZ-4ABA has been conducted using two functionals: B3LYP and wB97X-D. The results obtained by B3LYP and wB97X-D are compared which leads to the conclusion that B3LYP is the best applied function (density functional theory) to obtain suitable results for spectroscopy. The chemical reactivity descriptors are used to understand various aspects of pharmaceutical properties. Natural bond orbital (NBO) analysis and quantum theory of atoms (QTAIM) are used to analyze nature and strength of hydrogen bonding in HCTZ-4ABA. QTAIM analyzed moderate role of hydrogen bonding interactions in HCTZ-4ABA. The calculated HOMO-LUMO energy gap shows that HCTZ-4ABA is chemically more active than HCTZ drug. These chemical parameters suggest that HCTZ-4ABA is chemically more reactive and softer than HCTZ. The results of this study suggest that cocrystals can be a good alternative for enhancing physicochemical properties of a drug without altering its therapeutic properties.

Density Functional Theory Study of Cu6 Nanoclusters as a Phenylalanine Detector.

Research on amino acids is an attractive area because of their application in metabolism, cancer treatment, growth, and repair of body tissue, and RNA and DNA syntheses. Twenty amino acids are primarily responsible for protein synthesis. In our study, we used a Cu6 nanocluster as an amino acid detector. For the investigation, we adsorbed amino acids on the Cu6 nanocluster and studied their UV-visible spectra. It is observed that all of the Cu6-amino acid complexes have peaks at near 380 nm wavelength except the Cu-phenylalanine complex, where two UV-visible peaks are found at wavelengths 351 nm (excitation energy 3.49 eV) and 403 nm (excitation energy 3.02 eV), respectively, which originated from the HOMO - 2 to LUMO (28%) and HOMO - 1 to LUMO (38%) transitions. Due to this unique transition, the Cu6 nanocluster can be used for the detection of the phenylalanine amino acid out of the 20 amino acids.