Complexes C7 Research Articles

Regioselective cycloruthenation of N‐(benzylidene)benzylamines: Enantiopure catalysts for transfer hydrogenation

The reaction between N‐(benzylidene)benzylamines (p‐RC6H4CH=NCH2C6H5; R = Cl, H, NO2, F, OMe), [RuCl2(η6‐p‐cymene)]2 and potassium acetate has cleanly furnished the corresponding cycloruthenated complexes C1–C5. The process is completely regioselective, with the formation in all cases of the endo‐derivative, independently of the substituent of the aromatic ring. The five‐membered endo‐metallacycles C6 and C7 can also be obtained from the enantiopure imines (RC)‐p‐RC6H4CH=NCHMeC10H7 (R = Cl, H, respectively) working under similar conditions. The crystal structures of the seven metallated compounds have been determined by X‐ray diffraction. These complexes are active as catalyst precursors for the reduction of acetophenone and benzophenone by transfer hydrogenation. An enantiomeric excess of up to 77% at room temperature has been obtained with the complex C7 in the reduction of acetophenone.

Synthesis and characterization of cobalt (II) pincer complexes and their application as dyes in dye-sensitized solar cells

A series of eight cobalt(II) pincer complexes were prepared by using NNN tridentate and NN bidentate pincer ligand systems. All the ligands and complexes were completely characterized using various spectroscopic techniques and analytical methods including single crystal X-ray analysis. Optimization of the molecular structures of all the compounds was done by B3LYP computational method and the HOMO-LUMO energy gaps of the compounds were calculated. The optical band-gaps of the cobalt complexes were determined by using electronic spectral data and the corresponding electrochemical gaps were obtained from cyclic voltammetry studies. All the cobalt (II) complexes were used as dyes in the dye-sensitized solar cell and the photovoltaic parameters of the constructed solar cells were investigated. Complex C7, comprising of bis(benzimidazole) system with an ethylene backbone exhibited highest power conversion efficiency among the tested compounds.

Synthesis and In Vitro Studies of Photoactivatable Semisquaraine-type Pt(II) Complexes.

The synthesis, full characterization, photochemical properties, and cytotoxic activity toward cisplatin-resistant cancer cell lines of new semisquaraine-type Pt(II) complexes are presented. The synthesis of eight semisquaraine-type ligands has been carried out by means of an innovative, straightforward methodology. A thorough structural NMR and X-ray diffraction analysis of the new ligands and complexes has been done. Density functional theory calculations have allowed to assign the trans configuration of the platinum center. Through the structural modification of the ligands, it has been possible to synthesize some complexes, which have turned out to be photoactive at wavelengths that allow their activation in cell cultures and, importantly, two of them show remarkable solubility in biological media. Photodegradation processes have been studied in depth, including the structural identification of photoproducts, thus justifying the changes observed after irradiation. From biological assessment, complexes C7 and C8 have been demonstrated to behave as promising photoactivatable compounds in the assayed cancer cell lines. Upon photoactivation, both complexes are capable of inducing a higher cytotoxic effect on the tested cells compared with nonphotoactivated compounds. Among the observed results, it is remarkable to note that C7 showed a PI > 50 in HeLa cells, and C8 showed a PI > 40 in A2780 cells, being also effective over cisplatin-resistant A2780cis cells (PI = 7 and PI = 4, respectively). The mechanism of action of these complexes has been studied, revealing that these photoactivated platinum complexes would actually present a combined mode of action, a therapeutically potential advantage.

Synthesis and efficacy of copper(II) complexes bearing N(4)-substituted thiosemicarbazide and diimine co-ligands on plasmid DNA and HeLa cell lines

This present work deals with the synthesizes of nine novel thiosemicarbazone copper(II) complexes {[Cu(L)2]Cl C3, [Cu(L)(bpy)]Cl C4?C6, [Cu(L) (phen)]Cl C7?C9 (where, L = H(L1)?H(L3), H(L1) = (E)-N-methyl-2- -(1-phenyl-2-((5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl)thio)ethylidene)hydrazinecarbothioamide, H(L2) = (E)-N-ethyl-2-(1-phenyl-2-((5-(pyridin-3-yl)-4H- -1,2,4-triazol-3-yl)thio)ethylidene) hydrazinecarbothioamide, H(L3) = (E)-N- -phenyl-2-(1-phenyl-2-((5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl)thio)ethylidene) hydrazinecarbothioamide, bpy = 2,2?-bipyridyl and phen = 1,10-phenanthroline) with improved pharmacological results. The synthesized complexes were characterized by various spectral-analytical techniques. The structure of the copper(II) complexes C1?C9 was proposed by EPR spectroscopy. It confirmed the square planar coordination around Cu(II) complexes. The antibacterial screening of the complexes revealed that complexes C7 and C8 demonstrated significant activity against Gram-positive (B. thuringiensis) and Gram-negative (E. coli) bacteria. The concentration-dependent DNA cleavage activity of supercoiled (SC) pUC18 DNA exhibited complete DNA degradation effect on complex C6 at a minimum concentration of 40 ?M. In vitro cytotoxic results showed that the mixed ligand copper(II) complexes C4, C5 and C7 exhibited higher effects on human cervical cancer cell lines, HeLa, when compared to cisplatin. Hence, the results obtained from each biological screening indicated the superior biological efficacy of the mixed ligand copper(II) complexes bearing diimine moieties. It could be considered as a promising alternative to an existing anticancer drug.