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As part of our continuing interest in the chemistry of cationic antimony Lewis acids as ligands for late transition metals, we have now investigated the synthesis of platinum complexes featuring a triarylstibine ligand substituted by an o-[(dimethylamino)methyl]phenyl group referred to as ArN. More specifically, we describe the synthesis of the amino stibine ligand Ph2SbArN (L) and its platinum dichloride complex [LPtCl]Cl which exists as a chloride salt and which shows weak coordination of the amino group to the antimony center. We also report the conversion of [LPtCl]Cl into a tricationic complex [LHPt(SMe2)]3+ which has been isolated as a tris-triflate salt after reaction of [LPtCl]Cl with SMe2, HOTf and AgOTf. Finally, we show that [LHPt(SMe2)][OTf]3 acts as a catalyst for the cyclization of 2-allyl-2-(2-propynyl)malonate. 

Three copper redox shuttles ([Cu( 1 )] 2+/1+ , [Cu( 2 )] 2+/1+ , and [Cu( 3 )] 2+/1+ ) featuring tetradentate ligands were synthesized and evaluated computationally, electrochemically, and in dye-sensitized solar cell (DSC) devices using a benchmark organic dye, Y123 . Neutral polyaromatic ligands with limited flexibility were targeted as a strategy to improve solar-to-electrical energy conversion by reducing voltage losses associated with redox shuttle electron transfer events. Inner-sphere electron transfer reorganization energies ( λ ) were computed quantum chemically and compared to the commonly used [Co(bpy) 3 ] 3+/2+ redox shuttle which has a reported λ value of 0.61 eV. The geometrically constrained biphenyl-based Cu redox shuttles investigated here have lower reorganization energies (0.34–0.53 eV) and thus can potentially operate with lower driving forces for dye regeneration (Δ G reg ) in DSC devices when compared to [Co(bpy) 3 ] 3+/2+ -based devices. The rigid tetradentate ligand design promotes more efficient electron transfer reactions leading to an improved J SC (14.1 mA cm −2 ), higher stability due to the chelate effect, and a decrease in V lossOC for one of the copper redox shuttle-based devices. 

The photocatalytic reduction of CO2 can generate a number of products with CO and HCO2− being two of the most commonly observed. Frequently, the selective formation of one of these products is presumed to be the result of catalyst design. However, several common variables are present when exploring the photocatalytic CO2 reduction reaction. In order to better understand the origin of selectivity in this reaction, the choices of solvent, electron and proton source, photosensitizer (PS), and catalyst were evaluated in photocatalytic CO2 reduction reactions. Intriguingly, highly selective catalysts for CO or HCO2− under one set of conditions can be transformed by these environmental choices into becoming highly selective for the opposite product while retaining high turnover numbers. This highlights the importance of carefully considering reaction conditions before ascribing catalyst selectivity to an inherent molecular design property. 

The first examples of a CNC pincer ligands with a central pyridinol derived ring were recently reported.  The differences in catalytic reactivity between CNC ligands with a central pyridine ring vs. a pyridinol derived ring are substantial and highly active and robust catalysts have been synthesized and studied.  In these pincer ligands, the 4-substituent can be OMe, OH, or O , and these latter two options allow for altered catalyst properties as a function of proton concn.  Catalytic studies have used ruthenium(II), nickel(II), and other transition metals.  We have made metal complexes that can be protonated or deprotonated reversibly in situ to switch on or off the photocatalytic performance towards CO redn.  Furthermore, the methoxy group on the pyridine ring offers unique catalysis advantages not seen with the unsubstituted analog.  Our best catalysts offer selective CO formation, >300 turnover cycles, and a 40 h lifetime.  Highly active self-sensitized catalysts have recently been developed.  Steric and electronic ligand effects are being studied with these catalysts by exptl. and computational methods.