A sub-monolayer CdS shell on PbS quantum dots (QDs) enhances triplet energy transfer (TET) by suppressing competitive charge transfer from QDs to molecules. The CdS shell increases the linear photon upconversion quantum yield (QY) from 3.5 % for PbS QDs to 5.0 % for PbS/CdS QDs when functionalized with a tetracene acceptor, 5-CT. While transient absorption spectroscopy reveals that both PbS and PbS/CdS QDs show the formation of the 5-CT triplet (with rates of 5.91±0.60 ns and 1.03±0.09 ns respectively), ultrafast hole transfer occurs only from PbS QDs to 5-CT. Although the CdS shell decreases the TET rate, it enhances TET efficiency from 60.3±6.1 % to 71.8±6.2 % by suppressing hole transfer. Furthermore, the CdS shell prolongs the lifetime of the 5-CT triplet and thus enhances TET from 5-CT to the rubrene emitter, further bolstering the upconverison QY.

The multielectron reduction of small molecules (e.g., CO) is a key aspect of fuel synthesis from renewable electricity. Transition metals have been researched extensively in this role due to their intrinsic redox properties and reactivity, but more recently, strategies that forego transition metal ions for p-block elements have emerged. In this vein, we report an analogue of boranthrene (9,10-diboraanthracene) stabilized by N-heterocyclic carbenes and its one- and two-electron oxidized congeners. This platform exhibits reversible, two-electron redox chemistry at mild potentials and reacts with O, CO, and ethylene via formal [4+2] cycloaddition to the central diborabutadiene core. In an area traditionally dominated by transition metals, these results outline an approach for the redox activation of small molecules at mild potentials based on conjugated, light element scaffolds.

No abstract

Gold is unique among the transition metals in that it is stable as an isolated anion (auride). Despite this fact, the coordination chemistry of anionic gold is virtually nonexistent, and this unique oxidation state is not readily exploited in conventional solution chemistry owing to its high reactivity. Through the use of a new molecular scaffold based on diboraanthracene (B P , 1), we have overcome these issues by avoiding the intermediacy of zerovalent gold and stabilizing the highly reduced gold anion through acceptor interactions. We have thus synthesized a molecular boroauride [(B P )Au] ([2] ) and showed its reversible conversion between Au and Au states. Through a combination of spectroscopic and computational studies, we show the neutral state to be a Au complex with a ligand radical anion. Bonding analyses (NBO and QTAIM) and the isolobal relationship between gold and hydrogen provide support for the description of [2] as a boroauride complex.

3 )), and Mo(NAr)(CMePh)(Pyrrolide)(OHMT). X-ray studies reveal that in five compounds the alkylidene isomer (A) is that in which the phenyl group in the alkylidene points toward the imido nitrogen. In Mo(NAr)(CMePh)(OC 6 F 5 ) 2 (MeCN) the isomer in which the methyl group points toward the imido nitrogen (isomer B) has cocrystallized with isomer A (12%). In two 14e compounds that contain isomer A the Mo=C-C angles differ by 30-36°, consistent with a Mo … C-H agostic interaction. Several of the complexes reported here react readily with ethylene, 1-decene, or cyclooctene to give the expected products, thus confirming their viability as initiators or intermediates in metathesis reactions.