Triplet-Triplet Annihilation Upconversion from Red to Blue Light Using a TADF Sensitizer Based Polymer.

Molecules capable of thermally activated delayed fluorescence (TADF) can exhibit triplet lifetimes on the order of μs-ms as well as low energy losses in the intersystem crossing (ISC) process. As a result, they have great potential to be used as sensitizers in triplet-triplet annihilation upconversion (TTA-UC) systems with high anti-Stokes shifts, replacing traditional phosphorescent sensitizers. In this study, we employ a red-absorbing boron difluoride curcuminoid-based TADF molecule as the sensitizer and a 9,10-diphenylanthracene derivative as the annihilator.

Thermally activated delayed fluorescence materials as organic photosensitizers.

Photosensitizer molecules play a crucial role in materials and life sciences. Efforts to improve their performance and reduce the associated costs are therefore vital for advancing environmentally friendly light-driven technologies. In this Feature Article, we describe the use of photosensitizers that make use of thermally activated delayed fluorescence (TADF), their benefits compared to conventional fluorescent and phosphorescent sensitizers, and the efforts of our group and others to develop emitters with application-tailored properties.

Preparation of Patterned and Multilayer Thin Films for Organic Electronics via Oxygen-Tolerant SI-PET-RAFT.

An oxygen-tolerant approach is described for preparing surface-tethered polymer films of organic semiconductors directly from electrode substrates using polymer brush photolithography. A photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) approach was used to prepare multiblock polymer architectures with the structures of multi-layer organic light-emitting diodes (OLEDs), including electron-transport, emissive, and hole-transport layers. The preparation of thermally activated delayed fluorescence (TADF) and thermally assisted fluorescence (TAF) trilayer OLED architectures are described.

Thermally Assisted Fluorescent Polymers: Polycyclic Aromatic Materials for High Color Purity and White-Light Emission.

Thermally activated delayed fluorescence (TADF) sensitization of fluorescence is a promising strategy to improve the color purity and operational lifetime of conventional TADF organic light-emitting diodes (OLEDs). Here, we propose a new design strategy for TADF-sensitized fluorescence based on acrylic polymers with a pendant energy-harvesting host, a TADF sensitizer, and fluorescent emitter monomers. Fluorescent emitters were rationally designed from a series of homologous polycyclic aromatic amines, resulting in efficient and color-pure polymeric fluorophores capable of harvesting both singlet and triplet excitons.

Color-Tunable Thermally Activated Delayed Fluorescence in Oxadiazole-Based Acrylic Copolymers: Photophysical Properties and Applications in Ratiometric Oxygen Sensing.

Polymer-based emitters are a promising route to the production of low-cost, scalable solution-processable luminescent materials. Here we describe a series of acrylic oxadiazole-based donor-acceptor monomers with tunable emission from blue to orange, with quantum yields as high as 96%. By introducing structural constraints that limit donor-acceptor orbital overlap, thermally activated delayed fluorescence (TADF) was observed in these materials.

Preparation and luminescence properties of a M heterometallic coinage metal chalcogenide cluster.

A hexadeca-nuclear, N-heterocyclic carbene stabilized gold(i)-copper(i)-sulfido cluster is reported, which emits yellow-orange in the solid state. The nature of this emission is examined, supported by combined theoretical and spectroscopic studies.

Highly Electron-Deficient Pyridinium-Nitrones for Rapid and Tunable Inverse-Electron-Demand Strain-Promoted Alkyne-Nitrone Cycloaddition.

Highly accelerated inverse-electron-demand strain-promoted alkyne-nitrone cycloaddition (IED SPANC) between a stable cyclooctyne (bicyclo[6.1.0]nonyne (BCN)) and nitrones delocalized into a -pyridinium functionality is reported, with the most electron-deficient "pyridinium-nitrone" displaying among the most rapid cycloadditions to BCN that is currently reported.

Tuning the Metal/Chalcogen Composition in Copper(I)-Chalcogenide Clusters with Cyclic (Alkyl)(amino)carbene Ligands.

A series of phosphorescent homo- and heterometallic copper(I)-chalcogenide clusters stabilized by cyclic (alkyl)(amino)carbene ligands [CuM(μ-E)(CAAC)] (M = Cu, Ag, Au; E = S, Se) has been synthesized by the reaction of the new copper(I) trimethylsilylchalcogenolate compounds [(CAAC)CuESiMe] with ligand-supported group 11 acetates. The clusters are emissive at 77 K in solution and the solid state, with emission colors that depend on the metal/chalcogen composition. Electronic structure calculations point to a common [(M+E)LCT] emissive state for the series.

NHC Ligated Group 11 Metal-Arylthiolates Containing an Azide Functionality Amenable to "Click" Reaction Chemistry.

The reaction of N-heterocyclic carbene (NHC) Group 11 metal complexes, [(NHC)M-X] (X = chloride, acetate), with the new azide-modified arylthiol 1-HSCH-2,5-Me-4-NCH-CH, 1 (for M = Au; X = Cl), or 1-MeSiSCH-2,5-Me-4-NCH-CH, 2 (for M = Cu, X = Cl; M = Ag, X = OAc), affords the "clickable" NHC-metal thiolates [( Pr-bimy)Au-(1-SCH-2,5-Me-4-NCH-CH)], 5; [(IPr)Au-(1-SCH-2,5-Me-4-NCH-CH)], 6; [(IPr)Ag-(1-SCH-2,5-Me-4-NCH-CH)], 7; and [(IPr)Cu-(1-SCH-2,5-Me-4-NCH-CH)], 8 ( Pr-bimy = 1,3-di-isopropylbenzimidazol-2-ylidene, IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2-ylidene). Single-crystal X-ray analysis of all metal complexes show that they are two-coordinate, nearly linear, with a terminally bonded thiolate ligand possessing an accessible azide (-N) moiety. The strain-promoted alkyne-azide cycloaddition (SPAAC) reaction of complex 6 with bicyclo[6.

A N-Heterocyclic Carbene-Stabilized Coinage Metal-Chalcogenide Framework with Tunable Optical Properties.

A new class of coinage-metal chalcogenide compounds [AuM(μ-E)(IPr)] (M = Ag, Au; E = S, Se, Te) has been synthesized from the combination of N-heterocyclic carbene-ligated gold(I) trimethylsilylchalcogenolates [(IPr)AuESiMe] and ligand-supported metal acetates. Phosphorescence is observed from these clusters in glassy 2-methyltetrahydrofuran and in the solid state at 77 K, with emission energies that depend on the selection of metal/chalcogen ion composition. The ability to tune the emission is attributed to electronic transitions of mixed ligand-to-metal-metal-charge-transfer (IPr → AuM) and interligand (IPr → E) phosphorescence character, as revealed by time-dependent density functional theory computations.

A Controlled Route to a Luminescent 3 d -5 d Sulfido Cluster Containing Unique AuCu (μ -S) Motifs.

The first examples of gold(I) trimethylsilylchalcogenolate complexes were synthesized and their reactivity showcased in the preparation of a novel gold-copper-sulfur cluster [Au Cu S (dppm) ] (dppm=bis(diphenylphosphino)methane). The unprecedented structural chemistry of this compound gives rise to interesting optoelectronic properties, including long-lived orange luminescence in the solid state. Through time-dependent density functional theory calculations, this emission is shown to originate from ligand-to-metal charge transfer facilitated by Au⋅⋅⋅Cu metallophilic bonding.

Origin of the step structure of molecular exchange-correlation potentials.

The exact exchange-correlation potential of a stretched heteronuclear diatomic molecule exhibits a localized upshift in the region around the more electronegative atom; by this device the Kohn-Sham scheme ensures that the molecule dissociates into neutral atoms. Baerends and co-workers showed earlier that the upshift originates in the response part of the exchange-correlation potential. We describe a reliable numerical method for constructing the response potential of a given many-electron system and report accurate plots of this quantity.

White light generation using Förster resonance energy transfer between 3-hydroxyisoquinoline and Nile Red.

Simple composite films consisting of a polymer blended with organic emitters have the potential for broad-band "white" light emission that can be used for general lighting applications. In the present work, a simple mixture of 3-hydroxyisoquinoline (HIQ) with Nile Red (NR) in a polymeric matrix of polyvinyl alcohol (PVA) is used to generate white light through a non-radiative excitation energy transfer (NREET) mechanism. NREET between HIQ and NR doped in PVA films is investigated using a combination of steady state and time resolved fluorescence spectroscopic methods.