Moreover, simple shaking of 1:2 and 1:4 solid mixtures of 1,6-diol and the chalcones resulted in up to 90% photoconversion following UV-irradiation. The reactive solids based on 1,6-diol also formed via dry grinding. The 1,6-diol assembled the olefins within solid-state cavities supported by the bulky tetraphenyl-substituents of the host. The diol interacted with chalcones to generate photoactive hydrogen-bonded solids. Seminal work of Toda has reported on the reactivity properties of host–guest complexes formed with the divergent ditopic host 1,1,6,6-tetraphenyl-hexa-2,4-diyne-1,6-diol ( 1,6-diol). In both cases, the catalysts functioned as convergent ditopic receptors with reactivity occurring within zero-dimensional (0D), or discrete, hydrogen-bonded structures. The approach to supramolecular catalysis was performed mechanochemically via vortex grinding. Supramolecular catalysis of the photodimerization involving 4,4′-bpe was also realized using ditopic organoboronic acids as templates. The ditopic hydrogen-bond-donor 4,6-dichloro-resorcinol ( 4,6-diCl-res) was used in catalytic amounts as a template to achieve a photodimerization of trans-1,2-bis (4-pyridyl) ethylene ( 4,4′-bpe). We have recently demonstrated that intermolecular photodimerizations can be directed using principles of supramolecular catalysis in the solvent-free environment of the solid state.
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