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Either of two different isomeric products can be selectively obtained by photochemical 2+2 cycloaddition of 1,4-bis2-(4-pyridyl)ethenyl-benzene within a porous coordination polymer (PCP). The cycloaddition product obtained depends on the temperature at which irradiation occurs. A rare temperature-induced phase transition alters the conformation of the photoactive ligand in the PCP, and thereby the positions at which cycloaddition occurs. We show that the multistimulus responsive nature of this particular PCP is due to the flexibility of the ligands employed.
Claassens et al. (Tue,) studied this question.