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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: Two new charge transfer complexes (L1,2 →DDQ; L1 =(1H-benzimidazol-2-ylmethyl)-N-phenyl amine, L2 =(1H-benzimidazol-2-ylmethyl)-(4-nitro-phenyl)-amine, and DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone) have been synthesized and characterized by a variety of physico-chemical techniques. The experimental studies were complemented by quantum chemical calculations at DFT/B3LYP level of theory. Electronic structures were investigated by TD-DFT method and the descriptions of frontier molecular orbitals and the relocation of the electron density were determined. Stability of the molecule arises from hyperconjugative interactions, charge delocalization and hydrogen bonding has been analyzed using natural bond orbital (NBO) analysis. 1H NMR chemical shifts were computed at B3LYP/6-311+G(2d,p) level of theory by Gauge-invariant atomic orbital (GIAO) in DMSO as a solvent using the polarizable continuum model (PCM). Photometric titration was carried out to shed more light about the stoichiometry of the formed complexes in the solution. Spectral data were analyzed in terms of formation constant, molar extinction coefficient, oscillator strength, dipole moment, standard free energy, and ionization potential. [Copyright &y& Elsevier]

• Square-pyramidal Zn(II) azide complexes. • Based on TDDFT calculations, the lowest E transition is assigned to LLCT (N 3 →Terpy). • NBO analysis supported charge transfer from coordination sites toward Zn(II). • MEP maps showed that azido ligands have roles in the cycloaddition reaction. Square-pyramidal Zn(II) azide complexes with the formula of [Zn n (N 3) 2n L] (n = 1; L = 4′-(2-pyridyl)-2,2′:6′,2′'-terpyridine (LPy), 4′-(4-phenylmorpholine)-2,2′:6′,2′'-terpyridine (LMorph), and n = 2; L = 1,4- bis (2,2′:6′,2′'-terpyridin-4′-yl)benzene (LBPY)) were synthesized, and structurally characterized using different spectroscopic and analytical tools. Ground-state geometry optimization and harmonic vibrational analysis were carried out at two different levels of theory (B3LYP/LANL2DZ and CAM-B3LYP/def2-SVP) to gather insights into the local minimum structures. Natural bond orbital (NBO) analyses revealed that the electronic population of the 3d orbitals of Zn(II) ion is corresponding to the oxidation state of Zn(I), not Zn(II), in agreement with the ligand to metal charge transfer. Molecular electrostatic potential energy maps showed that the azido ligand may act as a nucleophile in the cycloaddition coupling with electron poor dipolar molecules. The electronic structure and transitions were investigated by executing time dependent density functional theory (TDDFT) calculations. [Display omitted] [ABSTRACT FROM AUTHOR]