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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]

Highlights: [•] The unit-cell of PQC is built by two molecules of different conformations. [•] DFT/B3LYP gives better agreement than HF method. [•] MCF7 cell line is more sensitive to PQC than HCT and HEPG2. [•] PQC has several sites for electrophilic attack. [•] The inclusion of solvation to NMR calculations is essential for acidic protons. [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]

Abstract: (1H-benzimidazol-2-ylmethyl)-(4-methoxyl-phenyl)-amine (L1), (1H-benzimidazol-2-ylmethyl)-(4-methyl-phenyl)-amine (L2) and their Pd(II) and Pt(II) complexes have been synthesized as potential anticancer compounds and their structures were elucidated using a variety of physico-chemical techniques. Theoretical calculations invoking geometry optimization, vibrational assignments, 1H NMR, charge distribution and molecular orbital description HOMO and LUMO were done using density functional theory. Natural bond orbital analysis (NBO) method was performed to provide details about the type of hybridization and the nature of bonding in the studied complexes. Strong coordination bonds (LP(1)N11→σ*(Md (LP(1)N21→σ*(M=Pd or Pt) result from donation of electron density from a lone pair orbital on the nitrogen atoms to the acceptor metal molecular orbitals. The experimental results and the calculated molecular parameters revealed square-planar geometries around the metallic centre through the pyridine-type nitrogen of the benzimidazole ring and secondary amino group and two chlorine atoms. The activation thermodynamic parameters were calculated using non-isothermal methods. The synthesized ligands, in comparison to their metal complexes were screened for their antibacterial activity. In addition, the studied complexes showed activity against three cell lines of different origin, breast cancer (MCF-7), Colon Carcinoma (HCT) and human heptacellular carcinoma (Hep-G2) comparable to cis-platin. [Copyright &y& Elsevier]