Simultaneous Thermally Stimulated Delayed Phosphorescence (TSDP) and Thermally Activated Delayed Fluorescence (TADF) in a Two-Coordinated Au(I) Bimetallic Complex Featuring a Tandem Carbene Structure.

A bimetallic, two-coordinated carbene-metal-amine (cMa) Au(I) complex featuring a twisted tandem carbene structure (NHC-Au-NHC-Au-carbazolyl) was synthesized. The molecular structure in single crystals revealed a large dihedral angle between the two carbene ligands, while the bridged carbene NHC and carbazolyl (Cz) ligands were coplanar. A bluish green thermally stimulated delayed phosphorescence (TSDP) was observed in crystals with an emission lifetime over 70 μs, which can be attributed to the spin allowed diabatic population of a high-lying emissive triplet state from the LE characterized low-lying ones.

Structural Diversity in 2-(2-Aminoethyl)pyridine-Based Lead Iodide Hybrids.

While 2D metal-organic hybrids have emerged as promising solar absorbers due to their improved moisture stability, their inferior transport properties limit their potential translation into devices. We report a new hybrid containing 2-(2-ammonioethyl)pyridine [(2-AEP)], forming a 2D hybrid with the composition (2-AEP)PbI. The organic bilayer comprises of (2-AEP), which is arranged in a face-to-face stacking that promotes π-π interactions between neighboring pyridyl rings.

Two-Coordinate Thermally Activated Delayed Fluorescence Coinage Metal Complexes: Molecular Design, Photophysical Characters, and Device Application.

Since the emergence of the first green light emission from a fluorescent thin-film organic light emitting diode (OLED) in the mid-1980s, a global consumer market for OLED displays has flourished over the past few decades. This growth can primarily be attributed to the development of noble metal phosphorescent emitters that facilitated remarkable gains in electrical conversion efficiency, a broadened color gamut, and vibrant image quality for OLED displays. Despite these achievements, the limited abundance of noble metals in the Earth's crust has spurred ongoing efforts to discover cost-effective electroluminescent materials.

Bis-oxazoline derivatives as ancillary ligands for bis-cyclometalated iridium complexes.

Organometallic iridium complexes with two cyclometalated ligands (ĈN) and one bis-oxazoline derived ancillary ligand (L^X), . (ĈN)Ir(L^X), are reported. The ĈN ligands are 1-phenylpyrazoline (ppz), 2-(4,6-difluorophenyl)pyridine (Fppy), 2-phenylpyridine (ppy), 1-phenylisoquinoline (piq).

Luminescent Bimetallic Two-Coordinate Gold(I) Complexes Utilizing Janus Carbenes.

A series of bimetallic carbene-metal-amide (cMa) complexes have been prepared with bridging biscarbene ligands to serve as a model for the design of luminescent materials with large oscillator strengths and small energy differences between the singlet and triplet states (Δ). The complexes have a general structure (RN)Au(:carbene─carbene:)Au(NR). The bimetallic complexes show solvation-dependent absorption and emission that is analyzed in detail.

Temperature dependence of radiative and non-radiative decay in the luminescence of one-dimensional pyridinium lead halide hybrids.

The photoluminescence properties of organic-inorganic pyridinium lead bromide [(pyH)PbBr] and iodide [(pyH)PbI] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX chains to the pyridinium cations.

A Comparison between Triphenylmethyl and Triphenylsilyl Spirobifluorenyl Hosts: Synthesis, Photophysics and Performance in Phosphorescent Organic Light-Emitting Diodes.

This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl () or triphenylsilyl () moieties for use as host materials in phosphorescent organic light-emitting diodes (PHOLED). Both molecules have similar high triplet energies and large energy gaps. Blue Ir(tpz) and green Ir(ppy) phosphorescent devices were fabricated using these materials as hosts.

Two-Coordinate Coinage Metal Complexes as Solar Photosensitizers.

Generating sustainable fuel from sunlight plays an important role in meeting the energy demands of the modern age. Herein, we report two-coordinate carbene-metal-amide (cMa, M = Cu(I) and Au(I)) complexes that can be used as sensitizers to promote the light-driven reduction of water to hydrogen. The cMa complexes studied here absorb visible photons (ε > 10 M cm), maintain long excited-state lifetimes (τ ∼ 0.

Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic-Organic Hybrids.

We report the growth and photophysical characterization of two polar hybrid lead halide phases, methylenedianiline lead iodide and bromide, (MDA)PbI and (MDA)PbBr, respectively. The phases crystallize in noncentrosymmetric space group 2, which produces a highly oriented molecular dipole moment that gives rise to second harmonic generation (SHG) upon excitation at 1064 nm. While both compositions are isostructural, the size dependence of the SHG signal suggests that the bromide exhibits a stronger phase-matching response whereas the iodide exhibits a significantly weaker non-phase-matching signal.

π-Extended Ligands in Two-Coordinate Coinage Metal Complexes.

Two-coordinate carbene-M-amide (cMa, M = Cu, Ag, Au) complexes have emerged as highly efficient luminescent materials for use in a variety of photonic applications due to their extremely fast radiative rates through thermally activated delayed fluorescence (TADF) from an interligand charge transfer (ICT) process. A series of cMa derivatives was prepared to examine the variables that affect the radiative rate, with the goal of understanding the parameters that control the radiative TADF process in these materials. We find that blue-emissive complexes with high photoluminescence efficiencies (Φ > 0.

Metal-Catalyzed and Metal-Free Nucleophilic Substitution of 7-I-BH.

In this work, two pathways of reactivity are investigated to generate site-specific substitutions at the B7 vertex of the luminescent boron cluster, -BH. First, a palladium-catalyzed cross-coupling reaction utilizing the precursor 7-I-BH and a series of model nucleophiles was developed, ultimately producing several B-N- and B-O-substituted species. Interestingly, the B-I bond in this cluster can also be substituted in an uncatalyzed fashion, leading to the formation of various B-N, B-O, and B-S products.

π-Extension of heterocycles a Pd-catalyzed heterocyclic aryne annulation: π-extended donors for TADF emitters.

We report the annulation of heterocyclic building blocks to access π-extended polycyclic aromatic hydrocarbons (PAHs). The method involves the trapping of short-lived hetarynes with catalytically-generated biaryl palladium intermediates and allows for the concise appendage of three or more fused aromatic rings about a central heterocyclic building block. Our studies focus on annulating the indole and carbazole heterocycles through the use of indolyne and carbazolyne chemistry, respectively, the latter of which required the synthesis of a new carbazolyne precursor.

Benchmarking the dynamic luminescence properties and UV stability of BH-based materials.

The dynamic photoluminescence properties, and potential quenching mechanisms, of -BH, 4,4'-Br--BH, and 4,4'-I--BH are investigated in solution and polymer films. UV stability studies of the neat powders show no decomposition occurring after intense 7 day light soaking. In contrast, clusters incorporated into polymer films are found to degrade into smaller borane fragments under the same irradiation conditions.

Molecular Alignment of Homoleptic Iridium Phosphors in Organic Light-Emitting Diodes.

The orientation of facial (fac) tris-cyclometalated iridium complexes in doped films prepared by vacuum deposition is investigated by altering the physical shape and electronic asymmetry in the molecular structure. Angle-dependent photoluminescence spectroscopy and Fourier-plane imaging microscopy show that the orientation of roughly spherical fac-tris(2-phenylpyridyl)iridium (Ir(ppy) ) is isotropic, whereas complexes that are oblate spheroids, fac-tris(mesityl-2-phenyl-1H-imidazole)iridium (Ir(mi) ) and fac-tris((3,5-dimethyl-[1,1'-biphenyl]-4-yl)-2-phenyl-1H-imidazole)iridium (Ir(mip) ), have a net horizontal alignment of their transition dipole moments. Optical anisotropy factors of 0.

A Luminescent Two-Coordinate Au Bimetallic Complex with a Tandem-Carbene Structure: A Molecular Design for the Enhancement of TADF Radiative Decay Rate.

A luminescent bimetallic Au complex comprised of N-heterocyclic carbene (NHC) and carbazole (Cz) ligands, that is, (NHC')Au(NHC)AuCz has been synthesized and studied. Both carbene ligands in the bimetallic complex act as electron acceptors in tandem to increase the energy separation between the ground and excited state, which is higher than those found in either monometallic analogue, (NHC)AuCz and (NHC')AuCz. A coplanar geometry designed into the tandem complex ensures sufficient electronic coupling between the π-orbitals of the ligands to impart a strong oscillator strength to the singlet intra-ligand charge-transfer ( ICT) transition.

Synthesis and Characterization of Zinc(II) Complexes Bearing 4-Acridinol and 1-Phenazinol Ligands.

The synthesis and characterization of zinc(II) chelates bearing acridin-4-ol (), phenazin-1-ol (), and benzo[]phenazin-1-ol () are presented. The formation of homoleptic () or heteroleptic () products can be controlled by stochiometric or excess amounts of zinc(II) acetylacetonate monohydrate, Zn(acac), respectively. Electrochemical and photophysical studies show that the homoleptic complexes (, , and ) have ligand-centered properties inherited from the corresponding free ligands.

Influence of Dimethyl Sulfoxide on the Structural Topology during Crystallization of PbI.

Hybrid metal-organic halides are an exciting class of materials that offer the opportunity to examine how fundamental aspects of chemical bonding can influence the structural topology. In this work, we describe how solvent adducts of lead halides can influence the crystallization and subsequent annealing of these hybrid phases. While the size and shape of organic molecules are known to govern the final topology of the hybrid, we show that the affinity of solvent molecules for Pb ions may also play a previously underappreciated role.

Highly Efficient Deep Blue Luminescence of 2-Coordinate Coinage Metal Complexes Bearing Bulky NHC Benzimidazolyl Carbene.

The structural, photophysical and electrochemical properties of three luminescent 2-coordinate coinage metal (i.e., M = Cu, Ag, Au) complexes bearing a sterically bulky benzimidazolyl carbene, 1,3-bis(2,6-diisopropylphenyl)-1-H-benzo[d]imidazol-2-ylidene (), and carbazolide (Cz) as the anionic ligand were investigated.

Vibrational Sum Frequency Generation Study of the Interference Effect on a Thin Film of 4,4'-Bis(-carbazolyl)-1,1'-biphenyl (CBP) and Its Interfacial Orientation.

Molecular organization of vapor-deposited organic molecules in the active layer of organic light-emitting diodes (OLEDs) has been a matter of great interest as it directly influences various optoelectronic properties and the overall performance of the devices. Contrary to the general assumption of isotropic molecular orientation in vacuum-deposited thin-film OLEDs, it is possible to achieve an anisotropic molecular distribution at or near the surface under controlled experimental conditions. In this study, we have used interface-specific vibrational sum frequency generation (VSFG) spectroscopy to determine the orientation of a low-molecular weight OLED material, 4,4'-bis(-carbazolyl)-1,1'-biphenyl (CBP), at free (air) and buried (CaF) interfaces.

A molecular boron cluster-based chromophore with dual emission.

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2, yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid. In contrast to the unsubstituted parent compound, 4-Br-anti-B18H21 possesses dual emission upon excitation with UV light and exhibits fluorescence at 410 nm and phosphorescence at 503 nm, with Φtotal = 0.07 in oxygen-free cyclohexane.

Enhancement of the Luminescent Efficiency in Carbene-Au-Aryl Complexes by the Restriction of Renner-Teller Distortion and Bond Rotation.

A series of (carbene)Au(aryl) complexes are reported. The nature of the lowest excited state in these complexes changes character from metal-to-ligand charge transfer (MLCT) to interligand charge transfer (ICT) with increasing electron-donating strength of the aryl ligand. Complexes that have the MLCT lowest excited state undergo a Renner-Teller bending distortion upon excitation.