Photoreactive salt cocrystal: N+-H•••N hydrogen bond and cation-π interactions support a cascade-like photodimerization of a 4-stilbazole

We describe hydrogen bonds (i.e., N+-H center dot center dot center dot N) in combination with cation center dot center dot center dot pi interactions to enable a cascade-like [2 + 2] photodimerization of 4-stilbazole in a salt cocrystal. A four-component crystal assembly is composed of photoactive pyridinium ion pair 4-stilbzH(+) (4-stilbz = trans-1-(4-pyridyl)-2-(phenyl)ethylene) and photostable molecule pair 4-stilbz. UV irradiation gives rctt-1,2-bis(4-pyridyl)-3,4-bis(phenyl)cyclobutane (4-pyr-ph-cb) in quantitative yield. An intermediate structure 2(4-stilbz)center dot(4-pyr-ph-cb)2H(+) is isolated that undergoes a partial single-crystal-to-single-crystal transformation. The single-crystal X-ray data provides a snapshot of movements in the salt cocrystal in the course of the photodimerization.

Automated summary

By utilizing hydrogen bonds and cation⋯π interactions, a cascade-like [2 + 2] photodimerization of 4-stilbazole in a salt cocrystal is achieved with high yield. The single-crystal X-ray data provides insights into the movements during the photodimerization process in the salt cocrystal.