Photocycloaddition of Zero-Dimensional Metal Halide Hybrids with Reversible Photochromism.

In this work, two zero-dimensional (0D) metal halide hybrids ZnBr [, = ()-4-(2-(1-pyrrol-3-yl)vinyl)-1-methylpyridin-1-ium] and PbBr () were prepared, which demonstrated photochromism and photoinduced cracking. Upon irradiation at 450 nm, a single crystal-to-single crystal transformation occurred as a result of the [2 + 2] photocycloaddition of . Interestingly, compared to the complete photocycloaddition of in , only two-thirds of monomers could be photodimerized in because of the difference in orientation. shows reversible photochromic behavior including rapid response time, few cracks, high conversion rate, and good reaction reversibility, while exhibits no significant color change but distinct photoinduced cracking because of the large local lattice strain induced by inhomogeneous and anisotropic deformation. Moreover, the photocycloaddition of results in the distinct shift of photoluminescence of and , attributed to the variation in conjugation of π electrons and distortion of metal halide clusters. As a proof-of-concept, reversible optical writing is demonstrated for . These findings provide new insights into the design of stimuli-responsive multifunctional materials.