Synthesis of organometallic Ru(II) and Fe(II) complexes containing fused rings hemi-helical ligands as chromophores. Evaluation of non-linear optical properties by HRS

Iron(II)-cyclopentadienyl compounds are cytotoxic against colon adenocarcinoma cell lines: Ethylenebis(diphenylphosphane) vs. triphenylphosphane

Structure-activity studies aiming to understand the role of each coligand in the formulation of new metallodrugs is an important subject. In that frame, six new compounds with general formula [Fe(η5-C5H5)(dppe)(L)][CF3SO3] with L = benzonitriles (1-4) or carbon monoxide (5) and compound [Fe(η5-C5H5)(CO)(PPh3)2][CF3SO3] (6) were synthesized and compared with three other previously reported compounds [Fe(η5-C5H5)(CO)(L)(PPh3)][CF3SO3]. We were particularly interested in assessing the effect of dppe vs. (PPh3 + CO) for this set of compounds. For that, all compounds were tested against two human colon adenocarcinoma cell lines, Colo205 and the refractile Colo320 (expressing ABCB1, an efflux pump causing multidrug resistance), showing IC50 values in the micromolar range. The presence of dppe in the compound's coordination sphere over (PPh3 + CO) allows for more redox stable compounds showing higher cytotoxicity and selectivity, with improved cytotoxicity towards resistant cells that is not related to the inhibition of ABCB1. Further studies with GSH and H2O2 for selected compounds indicated that their antioxidant ability is not probably the main responsible for their cytotoxicity.

pH-Switchability and Second-Order Nonlinear Optical Properties of Monocyclopentadienylruthenium(II)/iron(II) Tetrazoles/Tetrazolates: Synthesis, Characterization, and Time-Dependent Density Functional Theory Calculations

Tetrazole/tetrazolate monocyclopentadienyliron(II) and ruthenium(II) compounds of general formulas [(η⁵-C₅H₅)M(dppe)(N₄(H)CC₆H₄NO₂)][PF₆]/[(η⁵-C₅H₅)M(dppe)(N₄CC₆H₄NO₂)] were investigated for their pH-switching second-order nonlinear optical (SONLO) properties. Compounds [(η⁵-C₅H₅)M(dppe)(N₄CC₆H₄NO₂)] (M = Fe, Ru) and compound [(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)][PF₆] were fully characterized by (¹H-, ¹³C-, ³¹P-) NMR, cyclic voltammetry, and elemental analysis, and compounds [(η⁵-C₅H₅)Fe(dppe)(N₄CC₆H₄NO₂)] and [(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)][PF₆] were further characterized by single-crystal X-ray diffraction; the synthesis of [(η⁵-C₅H₅)Fe(dppe)(N₄(H)CC₆H₄NO₂)][PF₆] was unsuccessful. Time-dependent density functional theory calculations were performed using PBE0 and CAM-B3LYP functionals to evaluate the first hyperpolarizability (β_tot) of the tetrazole/tetrazolate complexes and for a detailed analysis of the experimental data. Both functionals predict (i) high first hyperpolarizabilities for the tetrazolate complexes [(η⁵-C₅H₅)M(dppe)(N₄CC₆H₄NO₂)], with β_tot[Ru] ≈ 1.2β_tot[Fe], and (ii) a 3-fold reduction in β_tot[Ru] upon protonation, in complex [(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)]⁺, forecasting [(η⁵-C₅H₅)Ru(dppe)(N₄CC₆H₄NO₂)]/[(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)]⁺ complexes as on/off, pH-switchable SONLO forms.

A non-photochemical route to synthesize simple benzo[1,2-b:4,3-b′]dithiophenes: FeCl3-mediated cyclization of dithienyl ethenes

The FeCl₃-mediated cyclization of α,α′-disubstituted Z-alkenes as a general and non-photochemical route to synthesize benzo[1,2-b:4,3-b′]dithiophene derivatives.

Studies of the Antiproliferative Activity of Ruthenium (II) Cyclopentadienyl-Derived Complexes with Nitrogen Coordinated Ligands

Four cationic ruthenium(II) complexes with the formula [Ru(eta(5)-C(5)H(5))(PPh(3))(2)](+), with L = 5-phenyl-1H-tetrazole (TzH) 1, imidazole (ImH) 2, benzo[1,2-b;4,3-b'] dithio-phen-2-carbonitrile (Bzt) 3, and [5-(2-thiophen-2-yl)-vinyl]-thiophene-2-carbonitrile] (Tvt) 4 were prepared and characterized in view to evaluate their potentialities as antitumor agents. Studies by Circular Dichroism indicated changes in the secondary structure of ct-DNA. Changes in the tertiary structure of pBR322 plasmid DNA were also observed in gel electrophoresis experiment and the images obtained by atomic force microscopy (AFM) suggest strong interaction with pBR322 plasmid DNA; the observed decreasing of the viscosity with time indicates that the complexes do not intercalate between DNA base pairs. Compounds 1, 2, and 3 showed much higher cytotoxicity than the cisplatin against human leukaemia cancer cells (HL-60 cells).