Synthesis, characterization and biological evaluation of new manganese metal carbonyl compounds that contain sulfur and selenium ligands as a promising new class of CORMs.

Three new manganese carbonyl compounds with heavy atom donors were synthesized and their potential use as photoCORMS was evaluated. Interestingly, all compounds had an elusive binding mode, in which the ligands adopted a κ2-X coordination (where X = S or Se), confirmed both by X-ray crystallography and IR spectroscopy. The stability of the title compounds in the dark was determined by monitoring the changes in the UV spectra of the compounds in both dichloromethane and acetonitrile. These studies show that in coordinating solvents there is an exchange of the bromide bonded to the metal centre by a solvent molecule, which is evidenced by the changes in the UV and IR spectra and by DFT analysis. EDA and natural bond order analyses were conducted to evaluate the influence of the heavy atom donors in the first coordination sphere of the compounds. Photoexcitation at 380 nm demonstrated that all compounds showed release of all three COs, as seen in the photoproducts detected by IR spectroscopy. Furthermore, CO release was observed when the photoCORMs were incubated with living cells, and we observed a CO-dependent inhibition of cell viability.

Synthesis and Solvatochromism of Substituted 4-(Nitrostyryl)phenolate Dyes.

4-(Nitrostyryl)phenols 2a-9a were synthesized, and by deprotonation in solution, the solvatochromic phenolates 2b-9b were formed. Their absorption bands in the vis region of the spectra are due to π-π* electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO-LUMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C═C bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, which is interpreted in terms of the ability of the media to stabilize their electronic ground and excited states to different extents. The Catalán multiparameter equation is used in the interpretation of the solvatochromic data, revealing that the most important contribution to the solute/solvent interaction is the hydrogen-bond donor acidity of the solvent.

A novel strategy for chromogenic chemosensors highly selective toward cyanide based on its reaction with 4-(2,4-dinitrobenzylideneamino)benzenes or 2,4-dinitrostilbenes.

N-(2,4-dinitrobenzylidene)-4-methoxyaniline (1), 4-(N,N-dimethylamine)-N-(2,4-dinitrobenzylidene)aniline (2), 2,4-dinitro-4'-methoxystilbene (3), and 2,4-dinitro-4'-(dimethylamino)stilbene (4) were synthesized and studied in dimethyl sulfoxide in a novel strategy as anionic chromogenic chemosensors. The color of the solutions of these compounds changed only in the presence of cyanide. The kinetic studies were performed with compounds 1-3 in an excess of cyanide. Higher second-order rate constant values were obtained for the compounds containing a methoxy group in relation to the compounds with a dimethylamino substituent, since the methoxy group donates electronic density to the 2,4-dinitrophenyl electron-accepting group less easily compared with the dimethylamino group. Stilbenes generally have greater structural rigidity than imines, facilitating the action of the substituents through the mesomeric effect. The data obtained indicate that the anion acts as a nucleophile, being responsible for CN bond breaking. The CC bridge is not broken in the stilbene dyes, but cyanide performs a nucleophilic attack on the 2,4-dinitrophenyl group.