Multicolor, fluorescent self-healing gels were constructed through reacting carbon dots produced from different aldehyde precursors with branched polyethylenimine. The self-healing gels were formed through Schiff base reaction between the aldehyde units displayed upon the carbon dots’ surface and primary amine residues within the polyethylenimine network, generating imine bonds. The dynamic covalent imine bonds between the carbon dots and polymeric matrix endowed the gels with both excellent self-healing properties as well as high mechanical strength. Moreover, the viscoelastic properties of the gels could be intimately modulated by controlling the ratio between the carbon dots and polymer. The distinct fluorescence emissions of the gels, originating from the specific carbon dot constituents, were employed for fabrication of light emitters at different colors, particularly generating white light.

Conspectus The most important means for tuning and improving a catalyst’s properties is the delicate exchange of the ligand shell around the central metal atom. Perhaps for no other organometallic-catalyzed reaction is this statement more valid than for ruthenium-based olefin metathesis. Indeed, even the simple exchange of an oxygen atom for a sulfur atom in a chelated ruthenium benzylidene about a decade ago resulted in the development of extremely stable, photoactive catalysts. This Account presents our perspective on the development of dormant olefin metathesis catalysts that can be activated by external stimuli and, more specifically, the use of light as an attractive inducing agent. The insight gained from a deeper understanding of the properties of cis -dichlororuthenium benzylidenes opened the doorway for the systematic development of new and efficient light-activated olefin metathesis catalysts and catalytic chromatic-orthogonal synthetic schemes. Following this, ways to disrupt the ligand-to-metal bond to accelerate the isomerization process that produced the active precatalyst were actively pursued. Thus, we summarize herein the original thermal activation experiments and how they brought about the discoveries of photoactivation in the sulfur-chelated benzylidene family of catalysts. The specific wavelengths of light that were used to dissociate the sulfur–ruthenium bond allowed us to develop noncommutative catalytic chromatic-orthogonal processes and to combine other photochemical reactions with photoinduced olefin metathesis, including using external light-absorbing molecules as “sunscreens” to achieve novel selectivities. Alteration of the ligand sphere, including modifications of the N-heterocyclic carbene (NHC) ligand and the introduction of cyclic alkyl amino carbene (CAAC) ligands, produced more efficient light-induced activity and special chemical selectivity. The use of electron-rich sulfoxides and, more prominently, phosphites as the agents that induce latency widened the spectrum of light-induced olefin metathesis reactions even further by expanding the colors of light that may now be used to activate the catalysts, which can be used in applications such as stereolithography and 3D printing of tough metathesis-derived polymers.

A general and straightforward synthesis of a series of solution‐processable carbon nitride polymers is described with excellent and tunable optical and electronic properties. The high dispersibility of carbon nitride polymers functionalized with polycyclic aromatic hydrocarbons (PAH‐CNs) in common solvents permits their facile processing into thin films utilizing routine methods such as spin‐coating and drop‐casting. Moreover, altering the PAH group within the CN scaffold enables great tunability of their optical and electronic properties as well as a range of functionalities. This is illustrated by a variety of photoelectrochemical properties, electropolymerization ability, and photoswitching properties for the different PAH‐CNs. The easy processing and tunable properties allow the construction of advanced electronic structures, such as a heterojunction, which significantly improves the photoelectrochemical performance. The versatility of this solution‐processable platform holds promise for the applicability of CNs in new photoelectronic devices.

The development of selective olefin metathesis catalysts is crucial to achieving new synthetic pathways. Herein, we show that cis‐diiodo/sulfur‐chelated ruthenium benzylidenes do not react with strained cycloalkenes and internal olefins, but can effectively catalyze metathesis reactions of terminal dienes. Surprisingly, internal olefins may partake in olefin metathesis reactions once the ruthenium methylidene intermediate has been generated. This unexpected behavior allows the facile formation of strained cis‐cyclooctene by the RCM reaction of 1,9‐undecadiene. Moreover, cis‐1,4‐polybutadiene may be transformed into small cyclic molecules, including its smallest precursor, 1,5‐cyclooctadiene, by the use of this novel sequence. Norbornenes, including the reactive dicyclopentadiene (DCPD), remain unscathed even in the presence of terminal olefin substrates as they are too bulky to approach the diiodo ruthenium methylidene. The experimental results are accompanied by thorough DFT calculations.

A new and simple synthetic route is introduced to covalently functionalize the carbon nitride (CN) framework by the implementation of halogenated phenyl groups (Cl, Br and I), which serve as a chemically reactive center, within the CN framework. The covalent modification is demonstrated here by substituting phenyl and tert-butyl propionate onto the modified-CN framework through Suzuki and reductive-Heck cross-coupling reactions, respectively. The effective functionalization leads to a facile exfoliation of the CN framework into thinner layers and greatly enhances the dispersibility in many solvents as well as the photocatalytic activity compared to the unmodified CN. The general covalent modification opens the possibility for tailor-made design of dispersible CN materials, including their photophysical and chemical properties, toward their exploitation in many fields, such as photocatalysis, bio-imaging, sensing, and heterogeneous catalysis.