Tatiana B Kouznetsova

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The mechanically accelerated ring-opening reaction of spiropyran to a colored merocyanine provides a useful method by which to image the molecular scale stress/strain distribution within a polymer, but the magnitude of the forces necessary for activation has yet to be quantified. Here, we report single molecule force spectroscopy studies of two spiropyran(More)
Mechanical forces along a polymer backbone can be used to bring about remarkable reactivity in embedded mechanically active functional groups, but little attention has been paid to how a given polymer backbone delivers that force to the reactant. Here, single-molecule force spectroscopy was used to directly quantify and compare the forces associated with(More)
Mechanical forces, applied via covalent polymer mechanochemistry, have been used to bias reaction pathways and activate otherwise inaccessible reactions. Here, single-molecule polymer mechanochemistry is used to induce the disrotatory outward ring opening of a cis-dialkyl substituted syn-chloro-gem-chlorofluorocyclopropane, in violation of the(More)
Single-molecule force spectroscopy (SMFS) of multi-mechanophore polymers has been used to provide kinetic and mechanistic insights into mechanochemical reactions. Whereas biological systems have benefitted from force clamp spectroscopy, synthetic polymers have been studied primarily with constant-velocity methods. Here, force clamp SMFS is applied to the(More)
Covalent polymer mechanochemistry offers promising opportunities for the control and engineering of reactivity. To date, covalent mechanochemistry has largely been limited to individual reactions, but it also presents potential for intricate reaction systems and feedback loops. Here we report a molecular architecture, in which a cyclobutane mechanophore(More)
The mechanochemical activation of cis-gem-difluorocyclopropane (cis-gDFC) mechanophore in toluene was characterized with single-molecule force spectroscopy. Unlike previously reported behavior in methyl benzoate (MB), two transitions are observed in the force vs extension curves of cis-gDFC polymers in toluene. The first transition occurs at the same force(More)
Forbidden reactions, such as those that violate orbital symmetry effects as captured in the Woodward-Hoffmann rules, remain an ongoing challenge for experimental characterization, because when the competing allowed pathway is available the reactions are intrinsically difficult to trigger. Recent developments in covalent mechanochemistry have opened the door(More)
Mechanical forces have previously been used to drive reactions along pathways that violate the orbital symmetry effects captured in the Woodward-Hoffmann rules. Here, we show that a polymer "lever arm effect" can provide a mechanical advantage in accelerating the symmetry forbidden disrotatory ring opening of benzocyclobutene (BCB). Addition of an(More)
The dynamics of reactions at or in the immediate vicinity of transition states are critical to reaction rates and product distributions, but direct experimental probes of those dynamics are rare. Here, s-trans, s-trans 1,3-diradicaloid transition states are trapped by tension along the backbone of purely cis-substituted gem-difluorocyclopropanated(More)
Molecular mechanisms by which to increase the activity of a mechanophore might provide access to new chemical reactions and enhanced stress-responsive behavior in mechanochemically active polymeric materials. Here, single-molecule force spectroscopy reveals that the force-induced acceleration of the electrocyclic ring opening of gem-dichlorocyclopropanes(More)