Bhandari Pallab, Modak Ritwik, Bhattacharyya Soumalya, Zangrando Ennio, Mukherjee Partha Sarathi
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.
Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste 34127, Italy.
JACS Au. 2021 Nov 8;1(12):2242-2248. doi: 10.1021/jacsau.1c00361. eCollection 2021 Dec 27.
Two tetragonal molecular barrels and were successfully synthesized by coordination-driven self-assembly of a tetrapyridyl donor () of the thiazolo[5,4-]thiazole backbone with -blocked 90° Pd(II) and Pt(II) acceptors, respectively. The single-crystal structure analysis of revealed the formation of a two-face opened tetragonal Pd molecular barrel architecture. In contrast, the isostructural Pt(II) barrel () is water-soluble. The large confined hydrophobic molecular cavity including wide open windows and good water solubility of the barrel made it a potential molecular container for the encapsulation of guests with different sizes and properties. This has been exploited to encapsulate and stabilize the open form of a photochromic molecule () in water, while the same photochromic molecule exists exclusively in a cyclic zwitterionic form in aqueous medium in the absence of the barrel . This cyclic form is very stable in water and does not go back to its parent open form under common external stimuli. Surprisingly, reverse switching of the cyclic form to a colored hydrophobic open form was also possible instantly in water upon addition of the solid barrel into an aqueous solution of . Such a fast reverse isomerization of an irreversible process in aqueous medium by utilizing host-guest interaction of the barrel and the guest is interesting. The barrel was also capable of encapsulating the water-insoluble radical initiator in aqueous medium.
通过噻唑并[5,4 - ]噻唑骨架的四吡啶供体（）与 - 封端的90°钯（II）和铂（II）受体分别进行配位驱动的自组装，成功合成了两个四方分子桶和。对的单晶结构分析揭示了两面开放的四方钯分子桶结构的形成。相比之下，同构的铂（II）桶（）是水溶性的。桶具有大的受限疏水分子腔，包括宽开口窗口且水溶性良好，这使其成为封装具有不同尺寸和性质客体的潜在分子容器。这已被用于在水中封装和稳定光致变色分子（）的开放形式，而在没有桶的情况下，相同的光致变色分子在水性介质中仅以环状两性离子形式存在。这种环状形式在水中非常稳定，在常见外部刺激下不会变回其母体开放形式。令人惊讶的是，将固体桶加入到的水溶液中后，在水中环状形式也能立即快速反向转变为有色疏水开放形式。通过利用桶与客体之间的主客体相互作用，在水性介质中使不可逆过程实现如此快速的反向异构化是很有趣的。桶还能够在水性介质中封装水不溶性自由基引发剂。
