CO Reduction Catalysts on Gold Electrode Surfaces Influenced by Large Electric Fields.

Attaching molecular catalysts to metal and semiconductor electrodes is a promising approach to developing new catalytic electrodes with combined advantages of molecular and heterogeneous catalysts. However, the effect of the interfacial electric field on the stability, activity, and selectivity of the catalysts is often poorly understood due to the complexity of interfaces. In this work, we examine the strength of the interfacial field at the binding site of CO reduction catalysts including Re(S-2,2'-bipyridine)(CO)Cl and Mn(S-2,2'-bipyridine)(CO)Br immobilized on Au electrodes.

Short-Range Catalyst-Surface Interactions Revealed by Heterodyne Two-Dimensional Sum Frequency Generation Spectroscopy.

Heterodyne 2D sum frequency generation spectroscopy is used to study a model CO2 reduction catalyst, Re(diCN-bpy) (CO)3Cl, as a monolayer on a gold surface. We show that short-range interactions with the surface can cause substantial line-shape differences between vibrational bands from the same molecules. We explain this interaction as the result of couplings between CO vibrational modes of the catalyst molecules and the image dipoles on gold surface, which are sensitive to the relative distance between the molecule and the surface.

Synthesis, Spectroscopy, and Electrochemistry of (α-Diimine)M(CO)Br, M = Mn, Re, Complexes: Ligands Isoelectronic to Bipyridyl Show Differences in CO Reduction.

The synthesis and characterization of new Mn(I)- and Re(I)-centered organometallic complexes fashioned with 1,4-diazabutadiene (DAB) ligands is reported. Ten compounds of the type -(α-diimine)M(CO)Br (M = Mn, Re) were obtained in moderate to excellent yield (35-80%) and high purity from the coordination of the five ligands with M(CO)Br in refluxing ethanol. Despite the electronic similarity of DAB to 2,2'-bipyridyl, the complexes described herein were poor mediators of electrochemical CO conversion to CO, but provide insight into the role of redox-active ligands in catalysis.

Improved Spectral Coverage and Fluorescence Quenching in Donor-acceptor Systems Involving Indolo[3-2-b]carbazole and Boron-dipyrromethene or Diketopyrrolopyrrole.

A novel π-conjugated triad and a polymer incorporating indolo[3,2-b]-carbazole (ICZ) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge-transfer state.