The crystals of N -salicylideneaniline (SA) and SA derivatives are classic functional materials that exhibit reversible colour changes (photochromism) and/or excited-state intramolecular proton transfer (ESIPT) fluorescence emission under ultraviolet (UV) light irradiation. In this study, a novel SA derivative was synthesised with an extended alkyl chain, N -(5-bromo-salicylidene)-3-aminoethylpyridine (5Br-SAEP). The photophysical properties of 5Br-SAEP were characterised in the crystalline state. The monohydrated crystal ( 1H ) of 5Br-SAEP was dehydrated to form the anhydrous crystal ( 1A ) at a relative humidity of less than 76%. The photochromic activity was switched by the dehydration phase transition from the non-photochromic 1H to the photochromic 1A . The quantum yield of fluorescence decreased significantly from 8% in 1H to 3% in 1A . The in situ change of photophysical properties occurred due to the change in the crystal structure. This indicated the potential of the solvated crystals of the SAEP derivatives for applications in novel switching or smart materials.

中文翻译：

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N-（5-溴-水杨基）-3-氨基乙基吡啶一水合晶体通过脱水相变的光物理性质变化

N-水杨基苯胺（SA）和SA衍生物的晶体是经典的功能材料，在紫外线（UV）照射下显示出可逆的颜色变化（光致变色）和/或激发态分子内质子转移（ESIPT）荧光发射。在这项研究中，合成了具有延长烷基链的新型SA衍生物N-（5-溴-水杨基亚烷基）-3-氨基乙基吡啶（5Br-SAEP）。在结晶状态下表征了5Br-SAEP的光物理性质。将5Br-SAEP的一水合晶体（1H）在小于76％的相对湿度下脱水以形成无水晶体（1A）。通过从非光致变色的1H到光致变色的1A的脱水相转变来切换光致变色的活性。荧光的量子产率从1H的8％显着降低到1A的3％。光物理性质的原位变化是由于晶体结构的变化而发生的。这表明了SAEP衍生物的溶剂化晶体在新型开关或智能材料中的应用潜力。