Authors Tsurkan, M. ; Jungnickel, C. ; Schlierf, M. ; Werner, C.
Title Forbidden chemistry: Two-photon pathway in [2+2] cycloaddition of maleimides
Date 06.07.2017
Number 53705
Abstract Two-photon excitation provides high spatial resolution in three dimensions of the corresponding chemical or physical processes, allowing submicrometer structuring in stereolithography and three-dimensional (3D) microfabrication. While studying two-photon structuring applications, we observed an undescribed phenomenon in photochemistry that dictates reactivity of maleimide groups in two-photon mode. A low-absorbance transition formerly ignored in classical photochemistry has been found for maleimides. This transition was assigned to symmetry-breaking donor–acceptor complex formation, which revealed a formally forbidden pathway in [2+2] cycloaddition reactions of maleimide moieties. This synthetic pathway allowed for the creation of hydrogel materials under physiological conditions at low laser excitation energy (0.1 J/cm2 at 800 nm) without the use of photoinitiators, which makes it truly two-photon click chemistry.
Publisher Journal of the American Chemical Society
Citation Journal of the American Chemical Society 139 (2017) 10184-10187

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