Single crystals capable of undergoing two distinct chemical transformations are rare, and achieving two distinct transformations controlled by two different stimuli is unprecedented. Here, we report an M:BPE co-crystal formed through complementary hydrogen bonding between the carboxylic acid group of M and the pyridyl group of BPE, further reinforced by C─H···O and C─H···N interactions. Monomer M contains azide and alkyne groups that undergo a heat-driven topochemical click reaction, while BPE features an olefin that enables light-driven topochemical 2+2 dimerization. Upon heating, M in the co-crystal undergoes a regiospecific click reaction in a single-crystal-to-single-crystal manner to yield a 1,4-triazolyl-linked cyclic dimer. In contrast, photoirradiation drives the BPE units in the co-crystal to undergo 2+2 photodimerization, yielding the rctt isomer. This stimulus-dependent behavior represents the first example of orthogonal reactivity within a single crystal mediated by different external stimuli.
Balakrishnan et al. (Fri,) studied this question.