Selective host–guest chemistry, self-assembly and conformational preferences of m -xylene macrocycles probed by ion-mobility spectrometry mass spectrometry
Selective host–guest chemistry, self-assembly and conformational preferences of m -xylene macrocycles probed by ion-mobility spectrometry mass spectrometry
复制标题
通过离子淌度质谱法探测间二甲苯大环的选择性主客体化学、自组装和构象偏好
DOI：
10.1039/c9cp06938k
复制
发表时间：
2020
影响因子：
3.3
通讯作者：
Do, Thanh D.
中科院分区：
文献类型：
--
作者：
Link, Benjamin A.;Sindt, Ammon J.;Shimizu, Linda S.;Do, Thanh D.
我们证明了离子迁移谱-质谱（IMS-MS）是一种强大的工具，用于询问和保存选择性化学反应，包括在溶液中形成的间二甲苯大环的非共价和主-客体配合物。该技术揭示了含硫脲大环MXT与Zn2+在四面体配位环境中形成具有Zn-S键的离轴夹心结构阳离子的二聚体配合物的独特优势。用尿素取代硫脲生成MXU， MXU与中性DMSO宾客形成高阶寡聚，并在每种低聚物大小下检测到弱结合相互作用。观察到该大环的自组装路径与晶体组装一致。尿素进一步转化为方酰胺产生MXS，这是一种罕见的探测溶液中硫酸盐的受体。MXS的单体和二聚体均观察到紧密的配合物，其中HSO4−与宿主的结合强于SO42−。HSO4−在结合腔中的位置与报道的SO42−晶体结构成180°反转。MXS二聚体与HSO4 -形成棱柱状结构，表现出与两个MXS大环的8个胺质子的强接触。通过消除分子间干扰，我们检测到MXS的低能量结构，其碰撞截面（CCS）与顺式-反式和顺式方酰胺-胺相匹配，这两种结构在结晶试验中都没有观察到。这些实验共同揭示了大环化学的多个方面，包括构象灵活性、自组装和配体结合；所有都在一个分析中。我们的研究结果说明了一种廉价且广泛适用的方法来研究定义大环形状和结合的弱但重要的相互作用。
We demonstrated ion-mobility spectrometry mass spectrometry (IMS-MS) as a powerful tool for interrogating and preserving selective chemistry including non-covalent and host–guest complexes of m-xylene macrocycles formed in solution. The technique readily revealed the unique favorability of a thiourea-containing macrocycle MXT to Zn2+ to form a dimer complex with the cation in an off-axis sandwich structure having the Zn–S bonds in a tetrahedral coordination environment. Replacing thiourea with urea generates MXU which formed high-order oligomerization with weak binding interactions to neutral DMSO guests detected at every oligomer size. The self-assembly pathway observed for this macrocycle is consistent with the crystalline assembly. Further transformation of urea into squaramide produces MXS, a rare receptor for probing sulfate in solution. Tight complexes were observed for both monomeric and dimeric of MXS in which HSO4− bound stronger than SO42− to the host. The position of HSO4− at the binding cavity is a 180° inversion of the reported crystallographic SO42−. The MXS dimer formed a prism-like shape with HSO4− exhibiting strong contacts with the 8 amine protons of two MXS macrocycles. By eliminating intermolecular interferences, we detected the low energy structures of MXS with collisional cross section (CCS) matching cis–trans and cis–cis squaramides-amines, both were not observed in crystallization trials. The experiments collectively unravel multiple facets of macrocycle chemistry including conformational flexibility, self-assembly and ligand binding; all in one analysis. Our findings illustrate an inexpensive and widely applicable approach to investigate weak but important interactions that define the shape and binding of macrocycles.