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A simple, sensitive and rapid method was developed for the quantitative analysis of sparfloxacin in its pharmaceutical formulations through the formation of charge transfer complexes with π-acceptor systems. The Lambert–Beer’s law was obeyed in the concentration ranges of 7–70 and 10–50 μg/mL sparfloxacin for 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and tetracyanoquinodimethane. Structural characterization of the isolated solid CT complexes was carried out by IR, 1 H NMR, UV–Vis. and MS. The experimental studies were complemented by quantum chemical calculations at DFT level of theory. The electronic structures were investigated by TD-DFT calculations. Natural bond orbital analysis and molecular electrostatic potential maps were helpful in assigning the CT route. The formation constant, molar extinction coefficient, oscillator strength, dipole moment, standard free energy and ionization potential were calculated. [ABSTRACT FROM AUTHOR]

Abstract: Comprehensive theoretical and experimental structural studies on N-(4,6-dimethyl-pyrimidin-2-yl)-4-[(2-hydroxy-benzylidene)-amino]benzenesulfonamide (SMS) have been carried out by elemental analysis, FT IR, 1H NMR, UV–Vis. and MS. Optimized molecular structure and harmonic vibrational frequencies have been investigated by DFT/B3LYP and HF methods combined with 6-31G(d) basis set. Stability of the molecule arises from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond has been analyzed using natural bond orbital (NBO) analysis. Electronic structures were discussed by TD-DFT method and the descriptions of frontier molecular orbitals and the relocation of the electron density were determined. 1H NMR chemical shifts were computed by Gauge-invariant atomic orbital (GIAO) method in both gas and DMSO media, using the polarizable continuum model (PCM). Structure–activity relationship has been used to correlate biological activity with some appropriate quantum descriptors such as E HOMO, E LUMO, energy gap, dipole moment (μ), global hardness (η), softness (S), electrophilicity index (ω), molecular polarizability (α), Mulliken electronegativity (χ), Mulliken charge (Qi ) and molecular electrostatic potential (MEP). [Copyright &y& Elsevier]

[MnLCl(H2O)3]·H2O complex (HL=4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide, sulfamethazine) has been synthesized and characterized by elemental analysis, TG/DTA, MS, FT-IR, UV–Vis, magnetic, electrochemical, and X-ray powder diffraction. The experimental studies were complemented by quantum chemical calculations at DFT/B3LYP level of theory. Sulfamethazine behaves as a mono-negatively bidentate ligand and interacts with Mn(II) ion through sulfonamidic (N15) and pyrimidic (N23) nitrogen atoms. Electronic structures were investigated using TD-DFT method and the descriptions of frontier molecular orbitals and the relocation of the electron density were determined. The voltammogram of NaL shows one irreversible one-electron process due to oxidation of p-amino group, and one anodic peak characteristic of reduction of - SO2 group. The synthesized complex, in comparison to the parent drug, was screened for its antibacterial activity. [ABSTRACT FROM AUTHOR]