Photocapture of dynamic hydrogen‐bonded assemblies

Abstract

Recent advances in the continuing study of [2+2] photodimerization reactions in supramolecular, non-covalent systems are presented. The covalent photocapture of small dynamic assemblies which are formed using weak hydrogen-bonding interactions between two different complementary units, barbiturates and melamines, is discussed. One unit serves as a photo-inert supramolecular template capable of bringing two photoactive units together using multiple hydrogen-bonds. The second type of unit unites the corresponding, complementary hydrogen-bonding motif with a photoactive unit. Irradiation of the supramolecular assemblies leads to photodimerization of adjacent units and generation of an imprinted site for the template. Moieties which are adapted to participate in photodimerization reactions are styrene, cinnamate, stilbene and fullerene units. The results are interpreted on the basis of topochemical reaction control.

Templated Photochemistry: Toward Catalysts Enhancing the Efficiency and Selectivity of Photoreactions in Homogeneous Solutions

“…A diaminotriazine−barbiturate-based assembly was successfully used for dimerization of cinnamates and stilbenes. , The hydrogen-bonding pattern of the diaminotriazine present in molecules 44 was complementary to that of barbituric acid 45 . In its presence, several hydrogen-bonded dimers and trimers can form.…”

A Photoresponsive Supramolecular G-Quadruplex

“…The reason why irradiation of 1 16 enables a [2 + 2] cycloaddition reaction is the increased proximity of four pairs of chalconyl double bonds in the supramolecule (Figure a). , The formation of a single diastereomer of 2 and the negligible formation of cis - 1 are indicative of the kinetic stability, well-defined spatial orientation of the double bonds, and the relatively crowded environment within 1 16 . Molecular modeling studies suggest the stereochemistry around the cyclobutyl moiety in 2 is the so-called δ-truxinate due to the relative orientation of the olefins prior to the dimerization (Figure S26). Minimization of the dimer by itself, followed by its superposition over the structure of 1 4 2 4 , shows minimal deviations in the overall geometry of the subunits (Figure S26).…”