Xiaohui Liu,Chudong Chen,Yonghong Xiao,Xianli Li,Ke Xu,Xin Lian,Jin Z. Zhang,Binbin Luo
In this work, two zero-dimensional (0D) metal halide hybrids L2ZnBr4 [1, L = (E)-4-(2-(1H-pyrrol-3-yl)vinyl)-1-methylpyridin-1-ium] and L6Pb3Br12 (2) 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 L. Interestingly, compared to the complete photocycloaddition of L in 1, only two-thirds of L monomers could be photodimerized in 2 because of the difference in L orientation. 1 shows reversible photochromic behavior including rapid response time, few cracks, high conversion rate, and good reaction reversibility, while 2 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 L results in the distinct shift of photoluminescence of 1 and 2, 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 1. These findings provide new insights into the design of stimuli-responsive multifunctional materials.
Organic-inorganic hybrid halides (OIHH) have garnered considerable attention as promising photo-functional materials. Nevertheless, the rational design of OIHH with tailored optical properties remains a formidable challenge. Herein, the synthesis of Sb 3+ -doped (benzamidine) 2 InCl 5 (H 2 O) crystals exhibiting intense visible-light emission is reported. Furthermore, photochromism (PC) and afterglow are achieved by exploiting intermolecular charge transfer between guest water and C═N + ─H group within the crystalline lattice. Radicals with a characteristic absorption band at 520 nm are generated by photo-irradiation, which causes PC, while the energy stored in the long-lived radicals gradually transfers to Sb 3+ centers, yielding an afterglow effect. Repeatable optical writing/erasing processes are demonstrated based on the reversible PC effect. In addition, a multi-level information encryption scheme is proposed based on the multiplexed integration of fluorescence color, PC, and afterglow. Therefore, this work not only develops a novel OIHH system but also offers a universal strategy for engineering photo-responsive functionalities by intermolecular charge transfer. While water promotes free radical reactions, it simultaneously accelerates PC bleaching, presenting a challenge that requires further research to resolve this dichotomy.
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