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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]

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]

• Acid dissociation constants fit well with Hammett constant. • Introduction of a substituent reduces the toxicity compared to the unsubstituted one. • Solvatochromism behaviour is mainly attributed to solvent dipolarity/polarizability. • Structural activity relationship is recognized by correlating toxicity to total energy. A series of (1H-benzimidazol-2-ylmethyl)-N-(4-phenyl)amine derivatives incorporating different electron-donating and withdrawing groups (X = 4 OCH 3 (1), 4 CH 3 (2), H (3), 4 Cl (4), and 4 Br (5)) on the para -position of the phenyl substituent was prepared, characterized and screened for their potential antimicrobial activity against some microbes. The substituent effect on the spectroscopic data (vibrational modes and NMR resonances) is well established by fitting with the Hammett constant. The unsubstituted derivative 4 exhibited comparable activity (MIC = 0.26 μM) to the standard tetracycline (MIC = 0.18 μM) against Staphylococcus aureus. Introduction of a substituent to the phenyl ring led to diminishing of the antibacterial activity. The substituent effect on the electron structure of 1–5 was investigated by TDDFT calculations. The acid dissociation constants of the ionizable NH group correlate well with Kubota's σ− parameter (R2 = 0.9196). The solvatochromism behavior of 1–5 , in solvents of different polarity and hydrogen-bond tendency, was investigated by linear solvation–energy relationship equation analysis. Correlation between various quantum chemical descriptors, and antibacterial activity was carried out to verify a structural activity relation for this series of benzimidazole derivatives. Image, graphical abstract [ABSTRACT FROM AUTHOR]