Luminescent complexes of heavy metals such as iridium, platinum, and ruthenium play an important role in photocatalysis and energy conversion applications as well as organic light-emitting diodes (OLEDs). Achieving comparable performance from more–earth-abundant copper requires overcoming the weak spin-orbit coupling of the light metal as well as limiting the high reorganization energies typical in copper(I) [Cu(I)] complexes. Here we report that two-coordinate Cu(I) complexes with redox active ligands in coplanar conformation manifest suppressed nonradiative decay, reduced structural reorganization, and sufficient orbital overlap for efficient charge transfer. We achieve photoluminescence efficiencies >99% and microsecond lifetimes, which lead to an efficient blue-emitting OLED. Photophysical analysis and simulations reveal a temperature-dependent interplay between emissive singlet and triplet charge-transfer states and amide-localized triplet states.

A systematic study is presented on the physical and photophysical properties of isoelectronic and isostructural Cu, Ag, and Au complexes with a common amide (N-carbazolyl) and two different carbene ligands (i.e., CAAC = (5R,6S)-2-(2,6-diisopropylphenyl)-6-isopropyl-3,3,9-trimethyl-2-azaspiro­[4.5]­decan-2-ylidene, MAC = 1,3-bis­(2,6-diisopropylphenyl)-5,5-dimethyl-4-keto-tetrahydropyridylidene). The crystal structures of the (carbene)­M(I)(N-carbazolyl) (MCAAC) and (MAC)­M(I)(N-carbazolyl) (MMAC) complexes show coplanar carbene and carbzole ligands and C–M–N bond angles of ∼180°. The electrochemical properties and energies for charge transfer (CT) absorption and emission compounds are not significantly affected by the choice of metal ion. All six of the (carbene)­M­(Cz) complexes examined here display high photoluminescence quantum yields of 0.8–1.0. The compounds have short emission lifetimes (τ = 0.33–2.8 μs) that fall in the order Ag < Au < Cu, with the lifetimes of (carbene)­Ag­(Cz) roughly a factor of 10 shorter than for (carbene)­Cu­(Cz) complexes. Detailed temperature-dependent photophysical measurements (5–325 K) were carried out to determine the singlet and triplet emission lifetimes (τfl and τph, respectively) and the energy difference between the singlet and triplet excited state, ΔE S1–T1. The τfl values range between 20 and 85 ns, and the τph values are in the 50–200 μs regime. The emission at room temperature is due exclusively to E-type delayed fluorescence or TADF (i.e., ). The emission rate at room temperature is fully governed by ΔE S1–T1, with the silver complexes giving ΔE S1–T1 values of 150–180 cm–1 (18–23 meV), whereas the gold and copper complexes give values of 570–590 cm–1 (70–73 meV).

Contrary to recent reports, the dehydrocoupling of pinacol borane and 9-borabicyclononane with a variety of amines, alcohols and thiols can be achieved under mild conditions without catalyst. This process involves the formation of Lewis acid-base adducts featuring a hydridic B-H in close proximity to an acidic Nu-H.

Through kinetic measurements, catalytic and stoichiometric experiments, as well as DFT calculations, we compare the catalytic activity of gold complexes supported by a variety of ligands (R3P, NHC, CAAC-5, CAAC-6, BiCAAC) in the hydroamination and hydrohydrazination of alkynes. This study provides a rationale for the superior efficiency of a gold complex bearing a bicyclic (alkyl)(amino)carbene (BiCAAC). We demonstrate that this ligand motif, which is readily available, provides a durable gold catalyst able to compete with sophisticated state-of-the-art phosphine and NHC ligands, which feature secondary interaction capabilities.

The concept of isomerism is essential to chemistry and allows defining molecules with an identical composition but different connectivity (bonds) between their atoms (constitutional isomers) and/or a different arrangement in space (stereoisomers). The reaction of phosphanyl ketenes, (NHP)-P=C=O (NHP=N-heterocyclic phosphenium) with N-heterocyclic carbenes (NHCs) leads to phosphaheteroallenes (NHP)-O-P=C=NHC in which the PCO unit has been isomerized to OPC. Based on the isolation of several intermediates and DFT calculations, a mechanism for this fundamental isomerisation process is proposed.