Surface-bound quadruple H-bonded dimers: formation and exchange kinetics

Direct and quantitative in-situ analysis of third-hand smoke in and on various matrices by ambient desorption corona beam ionization mass spectrometry

Third-hand smoke (THS) is composed of surface-deposited remnants resulting from tabacco-smoking. Because THS components have properties of remaining on, re-emitting from and reacting on and with surfaces, in-situ analysis of the components on different surfaces is both in high demand and challenging. The aim of this study is to establish desorption corona beam ionization (DCBI)-MS/MS as an analytical tool for THS research. To this end, an in-situ DCBI-MS/MS approach was developed for the quantitative analysis of typical THS environmental markers, i.e. nicotine and cotinine on different surfaces such as fruits, cotton clothing, glass, and toys etc. The limits of detection of nicotine and cotinine were both 1.4 μg m-2. Low-temperature DCBI-MS/MS was applied to the direct detection of THS on fingers without any skin damage. Smoking-related biomarkers analyses in urine were accomplished, with a 10 s DCBI analysis time. The on-surface tobacco-specific nitrosamines (TSNAs), such as 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal) (NNA), 4-(methylnitrosamino)-1-(3-pyridinyl)-1-butanone (NNK), and N-nitroso nornicotine (NNN) were in-situ successfully detected in dust samples.

Strain-Promoted Cycloaddition of Cyclopropenes with o-Quinones: A Rapid Click Reaction

Novel click reactions are of continued interest in fields as diverse as bio-conjugation, polymer science and surface chemistry. Qualification as a proper "click" reaction requires stringent criteria, including fast kinetics and high conversion, to be met. Herein, we report a novel strain-promoted cycloaddition between cyclopropenes and o-quinones in solution and on a surface. We demonstrate the "click character" of the reaction in solution and on surfaces for both monolayer and polymer brush functionalization.

Quantitative and Orthogonal Formation and Reactivity of SuFEx Platforms

The constraints of minute reactant amounts and the impossibility to remove any undesired surface‐bound products during monolayer functionalization of a surface necessitate the selection of efficient, modular and orthogonal reactions that lead to quantitative conversions. Herein, we explore the character of sulfur–fluoride exchange (SuFEx) reactions on a surface, and explore the applicability for quantitative and orthogonal surface functionalization. To this end, we demonstrate the use of ethenesulfonyl fluoride (ESF) as an efficient SuFEx linker for creating “SuFEx‐able” monolayer surfaces, enabling three distinct approaches to utilize SuFEx chemistry on a surface. The first approach relies on a di‐SuFEx loading allowing dual functionalization with a nucleophile, while the two latter approaches focus on dual (CuAAC–SuFEx/SPOCQ–SuFEx) click platforms. The resultant strategies allow facile attachment of two different substrates sequentially on the same platform. Along the way we also demonstrate the Michael addition of ethenesulfonyl fluoride to be a quantitative surface‐bound reaction, indicating significant promise in materials science for this reaction.

Kinetics of the Strain-Promoted Oxidation-Controlled Cycloalkyne-1,2-quinone Cycloaddition: Experimental and Theoretical Studies

Stimulated by its success in both bioconjugation and surface modification, we studied the strain-promoted oxidation-controlled cycloalkyne-1,2-quinone cycloaddition (SPOCQ) in three ways. First, the second-order rate constants and activation parameters (ΔH⧧) were determined of various cyclooctynes reacting with 4-tert-butyl-1,2-quinone in a SPOCQ reaction, yielding values for ΔH⧧ of 4.5, 7.3, and 12.1 kcal/mol, for bicyclo[6.1.0]non-4-yne (BCN), cyclooctyne (OCT), and dibenzoazacyclooctyne (DIBAC), respectively. Second, their reaction paths were investigated in detail by a range of quantum mechanical calculations. Single-configuration theoretical methods, like various DFT and a range of MP2-based methods, typically overestimate this barrier by 3-8 kcal/mol (after inclusion of zero-point energy, thermal, and solvation corrections), whereas MP2 itself underestimates the barrier significantly. Only dispersion-corrected DFT methods like B97D (yielding 4.9, 6.4, and 12.1 kcal/mol for these three reactions) and high-level CCSD(T) and multireference multiconfiguration AQCC ab initio approaches (both yielding 8.2 kcal/mol for BCN) give good approximations of experimental data. Finally, the multireference methods show that the radical character in the TS is rather small, thus rationalizing the use of single-reference methods like B97D and SCS-MP2 as intrinsically valid approaches.