Research on single-crystal-to-single-crystal photoaddition and extension of Schmidt's rule in topological chemistry

Abstract

In this article, we report the synthesis of a MOF containing multiple CC bonds geometrical features by adjusting the reactant ratio of the synthetic system. The photochemical addition studies revealed that the ligand 1,4-bis[2-(4-pyridyl)ethenyl]benzene can undergo photoisomerization under UV irradiation, and the θ angle between the CC bonds can be changed by about 85°, so that the CC pairs that do not conform to Schmidt's rule can be transformed into the conforming state, and then the 2 + 2 photoaddition can occur. We found that the θ angle range suitable for photoaddition includes not only the 0–15° range, but also the potential 85 ± 15° range. Furthermore, it is not the CC pair that best conforms to Schmidt's rule that gives priority to the photoaddition, but the one that enables the lowest total energy in the crystal to occur.