Dual reactivity based dynamic covalent chemistry: mechanisms and applications

Dynamic covalent chemistry (DCC) focuses on the reversible formation, breakage, and exchange of covalent bonds and assemblies, setting a bridge between irreversible organic synthesis and supramolecular chemistry and finding wide utility. In order to enhance structural and functional diversity and complexity, different types of dynamic covalent reactions (DCRs) are placed in one vessel, encompassing orthogonal DCC without crosstalk and communicating DCC with a shared reactive functional group. As a means of adding tautomers, widespread in chemistry, to interconnected DCRs and combining the features of orthogonal and communicating DCRs, a concept of dual reactivity based DCC and underlying structural and mechanistic insights are summarized. The manipulation of the distinct reactivity of structurally diverse ring-chain tautomers allows selective activation and switching of reaction pathways and corresponding DCRs (C-N, C-O, and C-S) and assemblies. The coupling with photoswitches further enables light-mediated formation and scission of multiple types of reversible covalent bonds. To showcase the capability of dual reactivity based DCC, the versatile applications in dynamic polymers and luminescent materials are presented, paving the way for future functionalization studies.

Polarity- and Pressure-Induced Emission from a Benzophenone-Based Luminophore

Since strong polarity usually causes emission quenching, materials with polarity-induced emission (PIE) are rarely reported despite their important applications in polar environments. Herein, an N-phenylcarbazole-substituted benzophenone derivative (BP-3-Cz) with a twisted electron donor-acceptor (D-A) structure is synthesized. The incorporation of heteroatoms into the twisted π-conjugated D-A backbone simultaneously endows BP-3-Cz with obvious polarity- and pressure-induced emission. Spectral analysis, X-ray diffraction, differential scanning calorimetry, and quantum chemical calculation results confirm that BP-3-Cz has special optical features related to the molecular conformation change and excited state turning to planarized intramolecular charge transfer with an increase in polarity or applied pressure. These findings contribute to the understanding of the PIE mechanism and the design of new PIE materials.

Tuning the selectivity of amino acid recognition with dynamic covalent bond constrained fluorophores in aqueous media

The recognition and discrimination of amino acids are generating continuous interest due to their importance. Herein we developed a series of dynamic covalent reaction constrained aldehyde-derived fluorescent probes for the binding of amino acids with tunable selectivity. Diverse emission behaviors were obtained via pH triggered movement of ring-chain tautomerization equilibrium of aldehyde probes. By taking advantage of the distinct pK_a and reactivity of aldehyde probes and amino acids, unique fluorescence signaling patterns were generated, and the selectivity for amino acid recognition was further modulated. The selective recognition of Cys/Hcy was attained at pH 7.4 as a result of thiazolidine formation. The manipulation of the reactivity at pH 10 enabled the realization of high selectivity for His and Cys, respectively. Moreover, pH and redox stimuli-responsive dynamic covalent networks were constructed for the regulation of amino acid recognition. The strategies and results described should be appealing in many aspects, including dynamic assemblies, molecular sensing, biological labeling, and smart materials.

Dynamic Covalent Chemistry Constrained Diphenylethenes: Control over Reactivity and Luminescence in both Solution and Solid State

Diarylethenes (DAEs) are an important class of building blocks in chemistry and materials science, and hence, their modulation and functionalization are of critical significance. Here we demonstrate a general strategy...