The utility and selectivity of the catalyst [Ru(COD)(L(1))Br2] (1) bearing a fused π-conjugated imidazo[1,2-a][1,8]naphthyridine-based abnormal N-heterocyclic carbene ligand L(1) is demonstrated toward selective oxidation of C═C bonds to aldehydes and C≡C bonds to α-diketones in an EtOAc/CH3CN/H2O solvent mixture at room temperature using a wide range of substrates, including highly functionalized sugar- and amino acid-derived compounds.

Ultrathin films of 2-ferrocenyl-1,3-dithiolane and 2-ferrocenyl-1,3-dithiane (Fcs), which are chemically inert at ambient conditions, are studied on the basal plane of highly oriented pyrolytic graphite (HOPG) using atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Films are prepared by drop-casting using Fcs dissolved in different solvents. Films prepared from methanol and dichloromethane show structural polymorphs on HOPG, while those prepared from ethanol, acetone, and dimethylformamide show an exclusive selection of one of the polymorphs. The selection of growth patterns of Fcs shows interesting correlation to the bulk solubility of molecules in the corresponding solvents and the solvent boiling point. The growth of Fcs at the submonolayer coverage is templated by the surface symmetry, and the molecular level packing on the surface is understood using high-resolution AFM, STM, and the bulk crystal packing of the molecules.

Cesium lead halide perovskite nanocrystals (PNCs) have enjoyed enormous attention in optoelectronics and photovoltaics. However, instability under polar conditions and limited energy/charge transport due to long-chain capping ligands restrict their large-scale applications. We have engineered a short-chain multidentate bolaamphiphilic ligand (NKE-3), which provides synergistic passivation of the perovskite surface by one multidentate ionic terminal and localizes water molecules by another multidentate ionic terminal, leading to a watersuspended colloidal solution of PNCs. NKE-3 allows efficient long-range dipole-based fluorescence resonance energy transfer (FRET) from perovskites to Rhodamine B isothiocyanate (RITC) in water, with FRET efficiencies ranging from 96% to 98%. We calculated the FRET rate using the acceptor's rise-time component, as it ensures no contamination from FRET-inactive donors. Moreover, we tuned the emission maxima of PNCs through halide exchange to optimize FRET efficiency. Such energy funneling to a suitable molecular photocatalyst is imperative for PNCs' potential applications.

Strategically designed surface modifiers that produce stable perovskite nanocrystals (NCs) and allow efficient charge extraction in polar solvents are critical for perovskite photocatalysis. We designed a multifunctional bolaamphiphilic ligand (NKE-12) with multidentate ionic groups at both ends, which significantly increases the colloidal stability of CsPbBr3 NCs in an aqueous medium without affecting their structural integrity and catalytic attributes. Ligand deconstruction via K and E fragmented ligands revealed synergistic actions of the cationic and anionic functionalities in surface passivation, phase separation, and water localization away from the surface of NKE-12-modified CsPbBr3 NCs. Multidimensional nuclear magnetic resonance experiments and contact angle measurements further suggested surface interactions and improved hydrophilicity via ionic terminal groups that account for water stability. Photogenerated hole-transfer dynamics of CsPbBr3/​NKE-12 NCs to a probe molecule 6,7-dihydroxy­coumarin was studied using transient absorption spectroscopy. Overall, this study paves the way for ligand design principles for surface engineering to develop water-stable perovskite photocatalysts.

Cesium lead halide (CsPbX3) perovskites, having stood out for solar cell applications, are now garnering attention in the field of photocatalysis as well. With a fundamental challenge in photocatalysis of...