Youngmin You

Phosphorescent Ir(III) complexes attract enormous attention because they allow highly efficient electrophosphorescence. In pursuing the development of Ir(III) complexes during the last decade, significant progress has been made in terms of the colour-tunability, thermal- and photo-stability, phase homogeneity, and phosphorescence efficiency. By far, extensive synthetic efforts have been focused on the molecular design of ligands to achieve a wide range of phosphorescence colour that is compatibl

We report a novel color tuning methodology in the electrophosphorescent iridium complex by substituting one cyclometalating ligand to an ancillary ligand as an emitting center. Highly efficient exothermic inter-ligand energy transfer (ILET) from the MLCT3 state produced between iridium and cyclometalating 2-(2,4-difluorophenyl)pyridine to LX3 state of the ancillary ligand offers a chance to access a wider range of color from sky blue (478 nm) to red (666 nm). Characteristic shapes of photolumine

A phosphorescent sensor based on a multichromophoric iridium(III) complex was synthesized and characterized. The construct exhibits concomitant changes in its phosphorescence intensity ratio and phosphorescence lifetime in response to copper(II) ion. The sensor, which is reversible and selective, is able to quantify copper(II) ions in aqueous media, and it detects intracellular copper ratiometrically.

A new phosphorescent zinc sensor (ZIrF) was constructed, based on an Ir(III) complex bearing two 2-(2,4-difluorophenyl)pyridine (dfppy) cyclometalating ligands and a neutral 1,10-phenanthroline (phen) ligand. A zinc-specific di(2-picolyl)amine (DPA) receptor was introduced at the 4-position of the phen ligand via a methylene linker. The cationic Ir(III) complex exhibited dual phosphorescence bands in CH(3)CN solutions originating from blue and yellow emission of the dfppy and phen ligands, respe

Abstract Difluoroalkylated aromatics are important structural motifs in pharmaceutical and agrochemical applications. Herein, we report their synthesis by a mild, efficient, and convenient method using visible light photoredox catalysis. A variety of unactivated aromatics were difluoroalkylated with ethyl 2‐bromo‐2,2‐difluoroacetate (BrCF 2 CO 2 Et) in the presence of the triscyclometalated Ir complex fac ‐[Ir(ppy) 3 ] under visible light irradiation at room temperature. It is shown that reactio

Abstract Two transformations initiated by photoinduced one‐electron transfer to α‐bromo ketones have been demonstrated. Hantzsch esters donate one electron to α‐bromo ketones under photoirradiation, promoting reductive debromination. Subsequent reactions of the resulting radical species of the ketones with molecular oxygen and Hantzsch esters lead to α‐hydroxylation or debromination, respectively. The relative dominance of the two pathways depends profoundly on the reaction conditions, including

Phosphorescence signaling provides a valuable alternative to conventional bioimaging based on fluorescence. The benefits of using phosphorescent molecules include improved sensitivity and capabilities for effective elimination of background signals by time-gated acquisition. Cyclometalated Ir(III) complexes are promising candidates for facilitating phosphorescent bioimaging because they provide synthetic versatility and excellent phosphorescence properties. In this Forum Article, we present our

Degradation of organic materials is responsible for the short operation lifetimes of organic light-emitting devices, but the mechanism by which such degradation is initiated has yet to be fully established. Here we report a new mechanism for degradation of emitting layers in blue-phosphorescent devices. We investigate binary mixtures of a wide bandgap host and a series of novel Ir(III) complex dopants having N-heterocyclocarbenic ligands. Our mechanistic study reveals the charge-neutral generati

A highly phosphorescent Ir(III) complex, containing a dimesitylboryl group in its coordinative phenylpyridine ligand, exhibited a phosphorescence colorimetric and ratiometric fluoride ion-selective sensing behavior and enabled facile signal purification through time-gated acquisition. Poly(methylmethacrylate) films doped with the Ir(III) complex were used to successfully detect fluoride ion in aqueous media.

An investigation of the photophysics of Ir(III) complexes with controlled ligand structures and our quantum chemical calculations attest that the most probable explanation for the reported 'aggregation-induced phosphorescent emission', which was originally claimed to be related to an intermolecular excimer, is restricted intramolecular motion.

The incorporation of a trifluoromethyl group into an existing scaffold can provide an effective strategy for designing new drugs and agrochemicals. Among the numerous approaches to trifluoromethylation, radical trifluoromethylation mediated by visible light-driven photoredox catalysis has gathered significant interest as it offers unique opportunities for circumventing the drawbacks encountered in conventional methods. A limited understanding of the mechanism and molecular parameters that contro

Growing evidence indicates intermediacy of singlet dioxygen (1O2) in a variety of pathophysiological processes. 1O2 has also found great utility of destructive actions for clinical and environmental applications. However, many details of the molecular mechanisms mediated by 1O2 remain insufficiently understood. Efforts to elucidate the 1O2 chemistry have been hampered by the lack of chemical tools capable of generation and detection of 1O2. In this review, I summarize the recent advances in the

Reductive N–O bond cleavage has been widely explored for providing either N or O radical species for various coupling processes. Despite significant advances, this photoredox pathway is less appealing due to poor atom economy owing to the loss of one fragment during the transformation. In this regard, the homolytic N–O bond cleavage by an energy-transfer pathway to provide two key radicals would be highly desirable for overcoming the limitations of the use of one fragment. We report an exclusive

We have characterized a series of highly phosphorescent cyclometalated heteroleptic Ir(III) complexes containing emitting (chromophoric) ancillary ligands with appropriate triplet levels below that of the cyclometalating ligand. We directly observed relatively rapid (ca. 6−7 ns-1) exothermic interligand energy transfer (ILET) from the cyclometalating ligand to the emitting ancillary ligand by time-resolved spectroscopy, which afforded a novel strategy of emission color tuning. Characteristic ILE