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Two‐coordinate carbene Cu(Ι) amide complexes with sterically bulky groups such as the diisopropyl phenyl (dipp) on the carbenes have been shown to have comparable performance to the phosphorescent emitters bearing heavy atoms such as iridium and platinum. These bulky groups enforce a coplanar molecular structure and suppress the nonradiative decay rates. Here, three different two‐coordinate Cu(Ι) complexes were investigated that bear a common thiazole carbene, 3‐(2,6‐diisopropylphenyl)‐4,5‐dimethylthiazol‐2‐ylidene, with only a single dipp group, and carbazolyl ligands with substituents of varying steric bulk ortho to N. These substituents have a negligible impact on luminescence energies of the complexes but serve to modulate the rotation barriers along the metal–ligand coordinate bond. The geometric arrangement of ligands (syn‐ or anti‐conformer) in complexes with alkyl substituents were found to differ, being syn in the solid state versus anti in solution as revealed by crystallographic analysis and nuclear magnetic resonance spectroscopy. In addition, calculations were performed to determine potential energy surfaces for different conformations of the three complexes to provide a theoretical evaluation of rotation barriers around the metal–ligand bond axis. The relationship between rotation barriers and photophysical properties demonstrate that rates for nonradiative decay decrease with increasing bulk of the substituents on the carbazolyl ligand. [ABSTRACT FROM AUTHOR]

The photoluminescence properties of organic–inorganic pyridinium lead bromide [(pyH)PbBr3] and iodide [(pyH)PbI3] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX6 octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX3 chains to the pyridinium cations. Both compounds display extremely weak luminescence at room temperature that becomes strongly enhanced upon cooling to 77 K. Broad, featureless low energy emission (λem > 600 nm) in both compounds have large Stokes shifts [1.1 eV for (pyH)PbBr3 and 0.46 eV for (pyH)PbI3] and are assigned to transitions from self-trapped excitons on the inorganic chains whereas emission at higher energy in (pyH)PbBr3 (λem = 450 nm) is assigned to luminescence from a free exciton state. Analysis of data from temperature-dependent luminescence intensity measurements gives activation energies (Ea) for non-radiative decay of the self-trapped excitons in (pyH)PbBr3 and (pyH)PbI3, (Ea = 0.077 eV and 0.103 eV, respectively) and for the free exciton in (pyH)PbBr3 (Ea = 0.010 eV). Analysis of temperature dependent luminescence lifetime data indicates another non-radiative decay process in (pyH)PbI3 at higher temperatures (Ea = 0.17 eV). A large increase in the luminescence lifetime of (pyH)PbI3 below 80 K is consistent with thermalization between triplet sublevels. Analysis of the luminescence power dependence for (pyH)PbI3 shows superlinear response suggestive of quenching by static traps. [ABSTRACT FROM AUTHOR]

This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl (SB-C) or triphenylsilyl (SB-Si) 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)3 and green Ir(ppy)3 phosphorescent devices were fabricated using these materials as hosts. Surprisingly, SB-Si demonstrated superior charge-transporting ability compared to SB-C, despite having similar energies for their valence orbitals. In particular, SB-Si proved to be a highly effective host for both blue and green devices, resulting in maximum efficiencies of 12.6% for the Ir(tpz)3 device and 9.6% for the Ir(ppy)3 device. These results highlight the benefits of appending the triphenylsilyl moiety onto host materials and underscore the importance of considering the morphology of hosts in the design of efficient PHOLEDs. [ABSTRACT FROM AUTHOR]

A series of twelve two-coordinate coinage metal, Cu, Ag and Au, complexes with carbene-metal-amide structures were prepared. The complexes all display thermal assisted delayed fluorescence (TADF) emission at room temperature from interligand charge transfer (ICT) excited state with short lifetimes (less than 2 μs) and photoluminescent quantum yields that reach near unity. Owing to the involvement of the substituents in the emissive transitions and different metal ion volume, the natural transition orbital (NTO) overlap of the emissive state can be adjusted in a wide range from 0.21 to 0.41. Investigations on the relationship between the NTO overlap of the emissive state and key TADF photophysical properties demonstrated that both singlet–triplet energy gap and radiative decay rate of S1 state increase along with the NTO overlap exponentially. Consequently, the overall TADF radiative decay rate leads to a maximum when plotted against the NTO overlap, giving the ideal zone from 0.25 to 0.30 for high TADF radiative decay rate in this class of two-coordinate coinage metal complex luminophores. [ABSTRACT FROM AUTHOR]

The thermally unstable, primary perfluoroalcohols, CF3OH, C2F5OH, and nC3F7OH, were conveniently prepared from the corresponding carbonyl compounds in anhydrous HF solution. Experimental values for the reaction enthalpies and entropies were derived from the temperature dependence of the RfCOF+HF⇄RfCF2OH (Rf=F, CF3, CF3CF2) equilibria by NMR spectroscopy. Electronic structure calculations of the gas‐phase and solution reaction energies, gas‐phase acidities and heats of formation were carried out at the G3MP2 level, showing that these compounds are strong acids. Protonation of these alcohols in HF/SbF5 produced the perfluoroalkyl oxonium salts RfCF2OH2+SbF6−. Highly acidic alcohols: The thermally unstable primary perfluorinated alcohols, CF3OH, C2F5OH, and nC3F7OH, and their oxonium salts were prepared from the corresponding carbonyl compounds in anhydrous HF and superacidic HF/SbF5 solutions. NMR spectroscopy allowed for the determination of experimental energy values obtained from the temperature dependence of the equilibria. Theoretical calculation of energetics, gas‐phase acidities and heats of formation at the G3MP2 level showed the strong acidic nature of these alcohols. [ABSTRACT FROM AUTHOR]

The thermally unstable α-fluoroalcohol undecafluorocyclohexanol (c-C6F11OH) was prepared by addition of hydrogen fluoride to the corresponding ketone. c-C6F10(CF3)OH was obtained by protonation of its alkoxide [NMe4]+[C7F13O]−. Decafluorocyclohexane-1,1-diol (c-C6F10(OH)2) was prepared by acidic workup of the corresponding alkoxide [NMe4]+[C6F11O]− with sulfuric acid, which yielded (c-C6F10(OH)2) and fluorosulfonic acid. The structures of c-C6F10(CF3)OH·2H2O and of (c-C6F10(OH)2) were elucidated by single-crystal X-ray and gas-phase electron-diffraction studies. [ABSTRACT FROM AUTHOR]

Abstract: The first X‐ray crystal structure of an α‐fluoroalcohol is reported. Heptafluorocyclobutanol was obtained in quantitative yield from hexafluorocyclobutanone by HF addition in anhydrous hydrogen fluoride. The compound was characterized by its X‐ray single crystal structure. Heptafluorocyclobutanol readily undergoes hydrolysis to hexafluorocyclobutane‐1,1‐diol, which was also structurally characterized by X‐ray diffraction. [ABSTRACT FROM AUTHOR]

Perfluoroalcohols: Although thermally unstable, these alcohols can be readily accessed through equilibria of the corresponding acyl fluorides with HF in anhydrous HF solution. These equilibria can be shifted to the side of the alcohols by trapping them as oxonium salts, ethers or alkoxides, thus making these reactions synthetically useful. More information can be found in the Communication by K. O. Christe et al. on page 16742. [ABSTRACT FROM AUTHOR]