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Abstract Persulfides (RSS^–) and thioselenides (RSSe^–) play important roles in biological S and Se transfer reactions, and their interactions with Lewis acidic moieties exert control over reactivity. Here, we report the synthesis and reactivity of mononuclear Zn²⁺persulfide and thioselenide complexes from a unified synthetic strategy of using isolable dichalcogenide precursors. Highlighting the benefits of replacing S with Se, we use⁷⁷Se NMR spectroscopy to reveal the effects of Lewis acid coordination (K⁺, Na⁺, Zn²⁺) on the electronic environment of the terminal Se of the thioselenide (R–S_β–Se_α^–). Coordination of RSSe^–to Zn²⁺polarizes the Se─S bond, rendering the internal sulfur atom (R–S_β–Se_α^–) susceptible to nucleophilic attack and resulting in selenide (Se^2–) release. We also prepared a mononuclear Zn²⁺persulfide complex and probed differences in persulfide nucleophilicity when compared to the parent thiolate. Alkylation of the Zn²⁺persulfide is considerably faster than the Zn²⁺thiolate, supporting the proposed nucleophilicity enhancement of persulfides due to the α‐effect, and providing new insights into persulfide reactivity when coordinated to metals. Taken together, these investigations highlight the utility of small molecule synthetic models in advancing insights into the biological chemistry of metal dichaclogenides. 

Abstract Hydrogen sulfide (H₂S) and nitric oxide (NO) are important gaseous biological signaling molecules that are involved in complex cellular pathways. A number of physiological processes require both H₂S and NO, which has led to the proposal that different H₂S/NO⋅ crosstalk species, including thionitrite (SNO⁻) and perthionitrite (SSNO⁻), are responsible for this observed codependence. Despite the importance of these S/N hybrid species, the reported properties and characterization, as well as the fundamental pathways of formation and subsequent reactivity, remain poorly understood. Herein we report new experimental insights into the fundamental reaction chemistry of pathways to form SNO⁻and SSNO⁻, including mechanisms for proton‐mediated interconversion. In addition, we demonstrate new modes of reactivity with other sulfur‐containing potential crosstalk species, including carbonyl sulfide (COS). 

Abstract Cucurbit[n]urils (CB[n]s) are cyclic macrocycles with rich host‐guest chemistry. In many cases, guest binding in CB[n]s results in host structural deformations. Unfortunately, measuring such deformations remains a major challenge, with only a handful of manual estimations reported in the literature. To address this challenge, we have developed the public program ElliptiCB[n], which is available on GitHub, that provides a robust and automated method for measuring the elliptical deformations in CB[n] hosts. We outline the development and validation of this approach, apply ElliptiCB[n] to measure the ellipticity of the 1113 available CB[n] structures from the Cambridge Structural Database (CSD), and directly investigate the structural deformations of CB[5], CB[6], CB[7], CB[8], and CB[10] hosts. We also report the general landscape of accessible CB[n] elliptical deformations and compare ellipticity distributions across CB[n] hosts and host‐guest complexes. We found that in almost all cases guest binding significantly impacts the distribution of host ellipticity distributions and that these distributions are dissimilar across host‐guest complexes of differently sized CB[n]s. We anticipate that this work will provide a useful approach for understanding of the flexibility of CB[n] hosts and will also enable future measurement and standardization of ellipticity measurements of CB[n]s.