Evidence of Splitting 1,2,3-Triazole into an Alkyne and Azide by Low Mechanical Force in the Presence of Other Covalent Bonds

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© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The cycloaddition reaction of an alkyne and azide to form a 1,2,3-triazole is widely used in many areas. However, the stability of the triazole moiety under mechanical stress is unclear. To see if a triazole could be selectively split into an alkyne and azide in the presence of other typical covalent bonds, a mica surface functionalized with a molecule containing a triazole moiety in the middle and an activated ester at the end was prepared. An atomic force microscope (AFM) tip with amino groups on its surface was ramped over the mica surface at predefined locations, which could temporarily link the tip to the surface through amide bond formation. During retraction, the triazole or another bond in the linkage broke, and a force was recorded. The forces varied widely at different ramps from close to 0 pN to 860 pN due to nonspecific adhesions and to the inherent inconsistency of single bond rupture. If some of the forces were from triazole cycloreversion, there would be alkynes at the predefined ramping locations. The surface was reacted with an azide carboxylic acid followed by labeling with amino Au nanoparticles (AuNPs). AFM imaging revealed AuNPs at the predicted locations, which provided evidence that under certain conditions triazole could be split selectively in the presence of other bonds at forces below 860 pN.

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Chemistry - A European Journal