Synthesis of Rhenium Carbonyl Complexes Bearing Substituted Pyrrolyl Ligands

New Class of Hybrid Materials for Detection, Capture, and "On-Demand" Release of Carbon Monoxide

Carbon monoxide (CO) is both a substance hazardous to health and a side product of a number of industrial processes, such as methanol steam reforming and large-scale oxidation reactions. The separation of CO from nitrogen (N₂) in industrial processes is considered to be difficult because of the similarities of their electronic structures, sizes, and physicochemical properties (e.g., boiling points). Carbon monoxide is also a major poison in fuel cells because of its adsorption onto the active sites of the catalysts. It is therefore of the utmost economic importance to discover new materials that enable effective CO capture and release under mild conditions. However, methods to specifically absorb and easily release CO in the presence of contaminants, such as water, nitrogen, carbon dioxide, and oxygen, at ambient temperature are not available. Here, we report the simple and versatile fabrication of a new class of hybrid materials that allows capture and release of carbon monoxide under mild conditions. We found that carborane-containing metal complexes encapsulated in networks made of poly(dimethylsiloxane) react with CO, even when immersed in water, leading to dramatic color and infrared signature changes. Furthermore, we found that the CO can be easily released from the materials by simply dipping the networks into an organic solvent for less than 1 min, at ambient temperature and pressure, which not only offers a straightforward recycling method, but also a new method for the "on-demand" release of carbon monoxide. We illustrated the utilization of the on-demand release of CO from the networks by carrying out a carbonylation reaction on an electron-deficient metal complex that led to the formation of the CO-adduct, with concomitant recycling of the gel. We anticipate that our sponge-like materials and scalable methodology will open up new avenues for the storage, transport, and controlled release of CO, the silent killer and a major industrial poison.

Synthesis and Photobiological Activity of Ru(II) Dyads Derived from Pyrrole-2-carboxylate Thionoesters

The synthesis and characterization of a series of heteroleptic ruthenium(II) dyads derived from pyrrole-2-carboxylate thionoesters are reported. Ligands bearing a conjugated thiocarbonyl group were found to be more reactive toward Ru(II) complexation compared to analogous all-oxygen pyrrole-2-carboxylate esters, and salient features of the resulting complexes were determined using X-ray crystallography, electronic absorption, and NMR spectroscopy. Selected complexes were evaluated for their potential in photobiological applications, whereupon all compounds demonstrated in vitro photodynamic therapy effects in HL-60 and SK-MEL-28 cells, with low nanomolar activities observed, and exhibited some of the largest photocytotoxicity indices to date (>2000). Importantly, the Ru(II) dyads could be activated by relatively soft doses of visible (100 J cm^-2, 29 mW cm^-2) or red light (100 J cm^-2, 34 mW cm^-2), which is compatible with therapeutic applications. Some compounds even demonstrated up to five-fold selectivity for malignant cells over noncancerous cells. These complexes were also shown to photocleave, and in some cases unwind, DNA in cell-free experiments. Thus, this new class of Ru(II) dyads has the capacity to interact with and damage biological macromolecules in the cell, making them attractive agents for photodynamic therapy.

A combined experimental and DFT investigation on the structure and CO-releasing properties of mono and binuclear fac-ReI(CO)3 complexes with 5-pyridin-2-ylmethylene-amino uracils

New tricarbonyl rhenium(i) complexes with 5-substituted-6-amino-1,3-dimethyluracils are reported.

Intramolecular C-C Bond Coupling of Nitriles to a Diimine Ligand in Group 7 Metal Tricarbonyl Complexes

Dissolution of M(CO)3(Br)(L(Ar)) [L(Ar) = (2,6-Cl2-C6H3-NCMe)2CH2] in either acetonitrile [M = Mn, Re] or benzonitrile (M = Re) results in C-C coupling of the nitrile to the diimine ligand. When reacted with acetonitrile, the intermediate adduct [M(CO)3(NCCH3)(L(Ar))]Br forms and undergoes an intramolecular C-C coupling reaction between the nitrile carbon and the methylene carbon of the β-diimine ligand.

Synthesis of heteroleptic pyrrolide/bipyridyl complexes of ruthenium(II)

The synthesis and characterization of the first heteroleptic pyrrolide/2,2′-bipyridyl complexes of ruthenium(II) are reported. Pyrroles substituted at the 2-position with X = O functionality react with Ru(bipy)2Cl2·2H2O to form complexes in which the pyrrolide ligands chelate to Ru(II). The library of pyrroles includes 2-formyl, 2-keto, 2-carboxylato, 2-sulfinyl, and 2-sulfonyl derivatives.