Self-Assembled Pd(II) Barrels as Containers for Transient Merocyanine form and Reverse Thermochromism of Spiropyran,Journal of the American Chemical Society

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Self-Assembled Pd(II) Barrels as Containers for Transient Merocyanine form and Reverse Thermochromism of Spiropyran
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-06-06 , DOI: 10.1021/jacs.8b03946
Prodip Howlader ₁ , Bijnaneswar Mondal ₁ , Prioti Choudhury Purba ₁ , Ennio Zangrando ₂ , Partha Sarathi Mukherjee ₁

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Self-assembly of a cis-blocked Pd(II) 90° ditopic acceptor [ cis-(tmeda)Pd(NO3)2] (M) with a tetradentate donor L1 [benzene-1,4-di(4-terpyridine)] in 2:1 molar ratio yielded two isometric molecular barrels MB1 and MB3 in DMSO [tmeda = N, N, N' N'-tetramethylethane-1,2-diamine]. Exclusive formation of the symmetrical tetrafacial barrel (MB1) was achieved when the self-assembly was performed in aqueous medium. The presence of a large confined cavity makes MB1 a potential molecular container. Spiropyran (SP) compounds exist in stable closed spiro form in visible light and convert to transient open merocyanine (MC) form upon irradiation with UV-light or upon strong heating. The transient MC form readily converts to the stable closed SP form in visible light. MB1 has been employed as a safe container to store the planar and unstable merocyanine isomers (MC1/2) of different spiropyran molecules (SP1/2) [SP1/2 = 6-bromo-spiropyran and 6-nitrospiropyran] for several days. The transient MC forms (MC1 and MC2) were found to be stable inside the molecular container MB1 under visible light and even in the presence of different stimuli such as heat and UV light for a long time. Such stabilization of MC forms inside the confined cavity of MB1 is noteworthy. This phenomenon was generalized by utilizing a carbazole-based molecular barrel (MB2) as a host, which also showed a similar stabilization of transient MC form in visible light at room temperature. Moreover, reverse thermochromism was observed as a result of heating of the MC1 ⊂ MB2 complex, which de-encapsulates the guest in the form of SP1 to give a colorless solution. Moreover, both the host molecules (MB1, MB2) were capable of stabilizing transient MC2 even in the solid state. Such stabilization of transient MC forms in the solid state and transformation of SP forms to MC forms in the solid state in the presence of molecular barrel are remarkable, and these properties have been employed in developing a magic ink.

中文翻译：

自组装 Pd(II) 桶作为瞬态部花青形式和螺吡喃的反向热致变色的容器

自组装顺式封闭的 Pd(II) 90° 双位受体 [cis-(tmeda)Pd(NO3)2] (M) 与四齿供体 L1 [苯-1,4-二(4-三联吡啶)]以 2:1 的摩尔比在 DMSO [tmeda = N, N, N' N'-四甲基乙烷-1,2-二胺] 中产生两个等距分子桶 MB1 和 MB3。当在水性介质中进行自组装时，实现了对称四面桶 (MB1) 的独家形成。大密闭腔的存在使 MB1 成为潜在的分子容器。螺吡喃 (SP) 化合物在可见光下以稳定的封闭螺形式存在，并在紫外线照射或强烈加热时转化为瞬态开放部花青 (MC) 形式。瞬态 MC 形式在可见光下很容易转换为稳定的封闭 SP 形式。MB1 已被用作安全容器来存储不同螺吡喃分子 (SP1/2) [SP1/2 = 6-溴-螺吡喃和 6-硝基螺吡喃] 的平面和不稳定部花青异构体 (MC1/2) 数天。发现瞬态 MC 形式（MC1 和 MC2）在可见光下甚至在不同刺激（如热和紫外光）的存在下在分子容器 MB1 内保持稳定。MB1 密闭腔内 MC 形式的这种稳定性值得注意。这种现象是通过利用咔唑基分子桶 (MB2) 作为主体来推广的，其在室温下在可见光下也显示出类似的瞬态 MC 形式的稳定性。此外，由于加热 MC1 ⊂ MB2 复合物，观察到反向热致变色，它以 SP1 的形式解封客体，得到无色溶液。此外，两种宿主分子（MB1、MB2）即使在固态下也能稳定瞬态 MC2。在分子桶的存在下，固态中瞬态 MC 形式的这种稳定和 SP 形式向固态中的 MC 形式的转变是显着的，并且这些特性已被用于开发魔术墨水。

更新日期：2018-06-06

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