A reaction cycle for redox-mediated, Ni-catalyzed aryl etherification is proposed under both photoredox and electrochemically mediated conditions. We demonstrate that a self-sustained Ni(I/III) cycle is operative in both cases by chemically synthesizing and characterizing a common paramagnetic Ni intermediate and establishing its catalytic activity. Furthermore, deleterious pathways leading to off-cycle Ni(II) species have been identified, allowing us to discover optimized conditions for achieving self-sustained reactivity at a ∼15-fold increase in the quantum yield and a ∼3-fold increase in the faradaic yield. These results highlight the importance of leveraging insight of complete reaction cycles for increasing the efficiency of redox-mediated reactions.

A laboratory experiment visually exploring two opposite basic principles of fluorescence of aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) is demonstrated. The students would prepared two salicylaldehyde-based Schiff bases through a simple one-pot condensation reaction of one equiv of 1,2-diamine with 2 equiv of salicylaldehyde. The resulting fluorescent dyes have similar chemical structures but possess ACQ and AIE properties, respectively. Their ACQ/AIE properties and pH sensing applications would then examined by visually qualitative analysis (UV lamp, light-emitting diode, and naked eye) and quantitative analysis (fluorometer). Finally, in a deeper level, X-ray single crystal structure analysis was utilized to reveal the inherent relationships between molecular structures/molecular arrangements and ACQ/AIE properties. This lesson is suitable for many areas of chemistry, especially for organic and analytical chemistry.

Self-sustained Ni I/III cycles are established as ap otentially general paradigm in photoredox Ni-catalyzed carbonheteroatom cross-coupling reactions through as trategy that allows us to recapitulate photoredox-like reactivity in the absence of light across aw ide range of substrates in the amination, etherification, and esterification of aryl bromides, the latter of whichh as remained, hitherto,e lusive under thermal Ni catalysis.M oreover,t he accessibility of esterification in the absence of light is especially notable because previous mechanistic studies on this transformation under photoredox conditions have unanimously invoked energytransfer-mediated pathways.

Photoredox-mediated nickel-catalyzed cross-couplings have evolved as a new effective strategy to forge carbon− heteroatom bonds that are difficult to access with traditional methods. Experimental mechanistic studies are challenging because these reactions involve multiple highly reactive intermediates and perplexing reaction pathways, engendering competing, but unverified, proposals for substrate conversions. Here, we report a comprehensive mechanistic study of photoredox nickel-catalyzed C−S cross-coupling based on time-resolved transient absorption spectroscopy, Stern−Volmer quenching, and quantum yield measurements. We have (i) discovered a self-sustained productive Ni(I/III) cycle leading to a quantum yield Φ > 1; (ii) found that pyridinium iodide, formed in situ, serves as the dominant quencher for the excited state photocatalyst and a critical redox mediator to facilitate the formation of the active Ni(I) catalyst; and (iii) observed critical intermediates and determined the rate constants associated with their reactivity. Not only do the findings reveal a complete reaction cycle for C−S cross-coupling, but the mechanistic insights have also allowed for the reaction efficiency to be optimized and the substrate scope to be expanded from aryl iodides to include aryl bromides, thus broadening the applicability of photoredox C−S cross-coupling chemistry.

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A novel unsymmetrical phthalimide-containing phthalonitrile (PIPN) was successfully synthesized. The chemical structure of the PIPN monomer was confirmed by various spectroscopic techniques. Rheology and differential scanning calorimetry (DSC) revealed that the self-promoted curing reaction of the PIPN was an extremely sluggish process. The fully cured PIPN polymers showed excellent thermal properties revealed by thermogravimetric analysis (TGA) and DSC. IR and solid-state UV-Vis diffusion reflectance spectra confirmed the formation of the triazine and phthalocyanine ring during the curing reaction.Rheometric studies suggested that the curing reaction of phthalonitrile with a phthalimide group was faster compared to the reaction with a benzimidazole ring, and a nucleophilic addition reaction mechanism was successfully introduced to explain this phenomenon.

Nickel-catalysed aryl amination and etherification are driven with sunlight using a surface-modified carbon nitride to extend the absorption of the photocatalyst such that they may be driven with solar light.

The reaction mechanism and the origin of the selectivity for the photocatalytic intermolecular anti-Markovnikov hydroamination of unactivated alkenes with primary amines to furnish secondary amines have been revealed by time-resolved laser kinetics measurements of the key reaction intermediates. We show that backelectron transfer (BET) between the photogenerated aminium radical cation (ARC) and reduced photocatalyst complex (Ir(II)) is nearly absent due to rapid deprotonation of the ARC on the sub-100 ns time scale. The selectivity for primary amine alkylation is derived from the faster addition of the primary ARCs (as compared to secondary ARCs) to alkenes. The turnover of the photocatalyst occurs via the reaction between Ir(II) and a thiyl radical; the in situ formation of an offcycle disulfide from thiyl radicals suppresses this turnover, diminishing the efficiency of the reaction. With these detailed mechanistic insights, the turnover of the photocatalyst has been optimized, resulting in a >10-fold improvement in the quantum yield. These improvements enabled the development of a scalable flow protocol, demonstrating a potential strategy for practical applications with improved energy efficiency and cost-effectiveness.