College of Chemistry and Chemical Engineering, Qingdao University, Shandong 266071, P. R. China.
Dalton Trans. 2019 Mar 19;48(12):3955-3961. doi: 10.1039/c9dt00081j.
Two zinc-diphosphonates formed from extended dipyridine units di-3,6-(4'-pyridyl)-1,2,4,5-tetrazine (dipytz) and 1,4-di(pyridine-4-yl)benzene (pbyb), [H2-Hdpt][Zn3(HEDP)2(H2O)]·2H2O (1) and [Zn2(HEDP)(pbyb)0.5(H2O)]·H2O (2) were solvothermally prepared (HEDP = 1-hydroxyethylidenediphosphonate, Hdpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole). Compound 1 exhibits an anionic Zn-HEDP layer with protonated dipyridine fragments as the template. In 2, the HEDP ligands bridge Zn2+ ions to form neutral zincophosphonate layers as supramolecular building blocks (SBBs), which are further pillared by neutral pbyb moieties to generate the final 3D pillar-layer structure. Interestingly, in situ reactions have taken place in the formation of 1, and the starting material dipytz in situ transformed to Hdpt in the process of assembly and was captured in the resultant crystal. Although the structural constituents are non-photochromic, 2 features photochromic performance with a detectable color change from colorless to pink under the stimulus of UV light under ambient conditions. A reversible color change process has been realized via annealing the colored sample at 120 °C for half an hour or putting the colored sample in air for two hours.
两个锌-二膦酸盐由扩展的联吡啶单元二-3,6-(4'-吡啶基)-1,2,4,5-四嗪(dipytz)和 1,4-二(吡啶-4-基)苯(pbyb)形成，[H2-Hdpt][Zn3(HEDP)2(H2O)]·2H2O (1) 和 [Zn2(HEDP)(pbyb)0.5(H2O)]·H2O (2) 是通过溶剂热法制备的(HEDP = 1-羟乙基二膦酸，Hdpt = 1H-3,5-双(4-吡啶基)-1,2,4-三唑)。化合物 1 具有带质子化联吡啶片段的阴离子 Zn-HEDP 层作为模板。在 2 中，HEDP 配体桥联 Zn2+离子形成中性锌磷酸酯层作为超分子建筑块(SBBs)，进一步被中性 pbyb 部分柱化，生成最终的 3D 支柱层结构。有趣的是，在 1 的形成过程中发生了原位反应，起始物质 dipytz 在组装过程中就地转化为 Hdpt，并被捕获在所得晶体中。尽管结构成分是非光致变色的，但 2 具有光致变色性能，在环境条件下，在紫外光的刺激下，颜色从无色变为粉红色。通过将有色样品在 120°C 下退火半小时或将有色样品暴露在空气中两小时，可以实现可逆的颜色变化过程。
