Radically Enhanced Dual Recognition
Radically Enhanced Dual Recognition
复制标题
DOI：
10.1002/anie.202109647
复制
发表时间：
2021-09-07
影响因子：
16.6
通讯作者：
Stoddart, J. Fraser
中科院分区：
文献类型：
--
作者：
Chen, Xiao-Yang;Mao, Haochuan;Stoddart, J. Fraser
紫精自由基阳离子（V.+）和环双（百草枯-对亚苯基）双自由基二价阳离子（CBPQT（2（.+）已经被广泛地研究和用于机械联锁分子（MIMs）和人工分子机器（AMM）的构建。一对V.+的选择性识别然而，使用自由基配对相互作用仍然是一个巨大的挑战。在此，我们报告了两个甲基紫精自由基阳离子（MV.+）的有效包封。在大小匹配的双自由基双阳离子主体--即环双（百草枯-2，6-萘）（2（.+））中，也就是说，CBPQN（2（.+））。这种双重识别过程的核心是选择2，6-双亚甲基萘连接体并入双自由基双阳离子主体中。它们提供了CBPQN（2（.+））中两个联吡啶鎓自由基阳离子之间的空间适合于结合两个MV.+具有相对短的（3.05-3.25埃）自由基配对距离。发现大小匹配的双自由基双阳离子主体与两个MV+表现出高度选择性和合作缔合。在MeCN中在室温下。四自由基四阳离子包合物的形成-即[CBPQN的（MV）（2）子集]（4（）（.+））- 通过VT H-1 NMR以及通过EPR光谱法证实。[CBPQN的（MV）（2）子集]（4（）（.+））的固态超结构揭示了三种不同V.+之间的结合距离（3.05，3.24，3.05埃）的不均匀分布，这表明自由基配对相互作用的定位对两个MV的堆积有很大影响。+在双自由基双阳离子宿主中。我们的研究结果构成了一个罕见的例子，结合两个自由基客人具有高亲和力和协同性，使用主机-客人自由基配对相互作用。此外，它们开辟了利用tetrakisradical四价阳离子包合络合物作为新的、正交的和氧化还原可切换的识别基序用于构建MIM和AMM的可能性。
Complexation between a viologen radical cation (V.+) and cyclobis(paraquat-p-phenylene) diradical dication (CBPQT(2(.+))) has been investigated and utilized extensively in the construction of mechanically interlocked molecules (MIMs) and artificial molecular machines (AMMs). The selective recognition of a pair of V.+ using radical-pairing interactions, however, remains a formidable challenge. Herein, we report the efficient encapsulation of two methyl viologen radical cations (MV.+) in a size-matched bisradical dicationic host - namely, cyclobis(paraquat-2,6-naphthalene)(2(.+)), i.e., CBPQN(2(.+)). Central to this dual recognition process was the choice of 2,6-bismethylenenaphthalene linkers for incorporation into the bisradical dicationic host. They provide the space between the two bipyridinium radical cations in CBPQN(2(.+)) suitable for binding two MV.+ with relatively short (3.05-3.25 angstrom) radical-pairing distances. The size-matched bisradical dicationic host was found to exhibit highly selective and cooperative association with the two MV.+ in MeCN at room temperature. The formation of the tetrakisradical tetracationic inclusion complex - namely, [(MV)(2)subset of CBPQN](4()(.+)) - in MeCN was confirmed by VT H-1 NMR, as well as by EPR spectroscopy. The solid-state superstructure of [(MV)(2)subset of CBPQN](4()(.+)) reveals an uneven distribution of the binding distances (3.05, 3.24, 3.05 angstrom) between the three different V.+, suggesting that localization of the radical-pairing interactions has a strong influence on the packing of the two MV.+ inside the bisradical dicationic host. Our findings constitute a rare example of binding two radical guests with high affinity and cooperativity using host-guest radical-pairing interactions. Moreover, they open up possibilities of harnessing the tetrakisradical tetracationic inclusion complex as a new, orthogonal and redox-switchable recognition motif for the construction of MIMs and AMMs.