Pyrene was derivatized in positions 1, 3, 6, and 8 to yield a series of nine tetraarylpyrenes for which absorption, emission, emission lifetimes and solvatochromism in solution were determined. The fluorescence quantum yields in thin films and crystalline state, electrochemistry, and quantum-chemical calculations were completed for the series along with the X-ray crystal structure analysis of compounds 1, 2, 4, 5, 7, and 9. Compounds 2, 3, 4 as well as 7 were identified as the most suitable candidates for OLED application. Notably, in an unoptimized single-layer device geometry, these compounds exhibited blue electroluminescence coupled with impressively low turn-on voltages and high maximum luminances such as 2.8 V and 13 542 cd m⁻² at 8.2 V for compound 2, respectively.

Dioxiranes are multi-tasking reagents with mild and selective oxygen transfer attributes. These oxidants are accessed from the reaction of ketones with an oxidant and are employed stoichiometrically or catalytically (in situ) for numerous transformations such as oxidations, epoxidations, C–H hydroxylation, etc. The oxidations involve a broad spectrum of substrates such as alcohols, amines, phenols, silanes, phosphines, etc. Similarly, the epoxidation of olefins, alkynes, allenes and arenes is achieved efficiently, where alkene epoxidation can be regioselective, chemoselective, stereoselective, and stereospecific. Furthermore, C–H hydroxylation using dioxiranes proceeds in both an inter- and intramolecular fashion producing a variety of potent molecules that are difficult to access using other means. Dioxiranes are used for the synthesis of various natural products, drugs, and biomolecules. This review covers all the aforementioned aspects of dioxirane chemistry along with the historical development, characteristics, and reaction mechanisms of dioxirane-mediated transformations established over the last five decades.

2,7-Bis(3,3′′,6,6′′-tetra(tert-butyl)-9′H-9,3′:6′,9′′-tercarbazol-9-yl)-4,5,9,10-tetrahydropyrene (3) and 2,7-bis(3,3′′,6,6′′-tetra(tert-butyl)-9′H-9,3′:6′,9′′-tercarbazol-9-yl)pyrene (4), along with a model compound, 3,3′′,6,6′′-tetra(tert-butyl)-9′-(4-(tert-butyl)phenyl)-9′H-9,3′:6′,9′′-tercarbazole (6), have been synthesized using microwave-assisted palladium-catalyzed coupling and compared to analogous 3,6-di(tert-butyl)carbazol-9-yl species (1, 2, and 5). Time-dependent density functional theory (TDDFT) calculations reveal absorption with quadrupolar (ter)carbazole-to-bridge CT character for 1–4. Compound 4 is unusual in showing dual fluorescence in a number of solvents; the longer wavelength feature of which is markedly more solvatochromic than the bands of the other compounds. Following the observed three oxidations on the TCz model compound 6, compounds 3 and 4 can be electrochemically reversibly oxidized to hexacations with four oxidation and three oxidation steps in a 2 : 2 : 1 : 1 and a 2 : 2 : 2 current ratio, respectively. Tercarbazole derivatives 3 and 4 have been used as the emissive layers of simple solution-processed few-layer organic light-emitting diodes.

We disclose an unprecedented single-step metal-free green oxidation of 2,7-di-tert-butylpyrene selectively into either the corresponding 4,5-dione or 4,5,9,10-tetraone, two key building blocks used for organic optoelectronic applications using hypervalent iodine oxyacids. This new method results in dramatic improvements in terms of yield, selectivity (dione vs. tetraone), ease of workup, cost and toxicity.