Tarek H. El-Assaad

Redox flow batteries (RFBs) have emerged as significant energy storage systems amid the growing adoption of renewable energy. However, the advancement of all-organic RFBs is hindered by material crossover, limited energy density, and the time-consuming selection of suitable electrolyte partners. To address these challenges, bipolar redox-active organic molecules (BRMs) show promise for charge storage in symmetric organic redox flow batteries (SORFBs), although their development can be complex and tedious. In this study, we report an approach aimed at streamlining the identification of suitable compounds through an examination of the organophotocatalyst literature, illustrated through six acridinium compounds exhibiting stable redox states. These compounds were thoroughly characterized in electrochemical cells and subjected to cycling tests in fully symmetric flow batteries. Notably, a trisubstituted electron-rich acridinium compound emerged as a potential candidate, demonstrating over 20 days of cycling stability. Given the extensive library of organic catalysts and the advantages of SORFB designs, this approach will prove to be essential for developing an innovative electrochemical storage system.

We disclose a four-step oxidize-condense-oxidize-condense synthesis pathway to prepare nonsymmetric pyrene-fused pyrazaacenes (PPAs) using our recently discovered oxidation conditions for 2,7-di-tert-butylpyrene. The new pathway results in marked improvements in yields and simplifies purification as compared with the sequential condensation strategy previously employed to make these compounds.

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.

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.

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.

Diketopyrrolopyrrole and isoindigo are commercially important dyes that have recently found broad application as electron acceptor and light‐absorbing groups in organic semiconductors. Their self‐assembly into specific supramolecular structures to control optoelectronic properties has been hampered by limited options for substitution and their high propensity for crystallization. Reported here is a molecular design that directs self‐assembly into previously elusive columnar mesophases of π‐π stacking cores. Although attachment of bis(trisoctyloxyphenyl)‐1,3,5‐triazine groups to both ends of diketopyrrolopyrrole‐thiophene and isoindigo cores generated mesomorphic dyes of similar overall shapes and dimensions, distinct differences in their mesomorphism and optoelectronic properties were observed.

Thin film structural features of TQPP-Me and TQPP-OC ₁₂ as explored by spectroscopic and ellipsometric techniques.