posted on 2023-11-30, 21:16authored byBohan Tang, Mike Pauls, Christoph Bannwarth, Stefan Hecht
Multiple hydrogen-bonding motifs serve as important building
blocks
for molecular recognition and self-assembly. Herein, a photoswitchable
quadruple hydrogen-bonding motif featuring near-complete, reversible,
and thermostable conversion between DADA and AADD arrays associated
with an alteration of their dimerization constants by over 3 orders
of magnitude is reported. The system is based on a diarylethene featuring
a ureidopyrimidin-4-ol moiety, which upon photoinduced ring closure
and associated loss of aromaticity undergoes enol–keto tautomerization
to a ureidopyrimidinone moiety. The latter causes a transformation
of the hydrogen-bonding arrays and significantly weakens the free
energy of dimerization in the case of the closed isomer. This photoswitchable
quadruple hydrogen-bonding motif should allow us to spatially and
temporarily direct self-assembly and supramolecular polymerization
processes by light.