Synthetic Supercontainers Exhibit Distinct Solution versus Solid State Guest-Binding Behavior
Synthetic Supercontainers Exhibit Distinct Solution versus Solid State Guest-Binding Behavior
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DOI：
10.1021/ja502839b
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发表时间：
2014-05-21
影响因子：
15
通讯作者：
Wang, Zhenqiang
中科院分区：
文献类型：
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作者：
Dai, Feng-Rong;Sambasivam, Uma;Wang, Zhenqiang
在均相溶液和液-液、固-液、固-气界面上研究了一类新的合成超容器的相依赖性主客体结合行为。合成主体，即II型金属有机超容器（MOSC），由二价金属离子、1，4-苯二甲酸酯（BDC）连接体和磺酰基杯[4]芳烃基容器前体的组装体构建。MOSC的一个成员，MOSC-II-tBu-Ni，其衍生自Ni（II）、BDC和对叔丁基磺酰基杯[4]芳烃（TBSC），在棒上的空间群R（3）中结晶，并采用伪面心立方（fcc）堆积，而其他MOSC，包括TBSC类似物MOSC-II-tBu-Co，对叔戊基磺酰基杯[4]芳烃（TPSC）类似物MOSC-II-tPen-Ni/Co，和对叔辛基磺酰基杯[4]芳烃（TOSC）类似物MOSC-II-tOc-Ni/Mg/Co，均属于I4/m空间群，并呈现赝体心立方（bcc）堆积模式。然而，这种固态结构的多样性并没有反映在它们的溶液主客体化学中，如由溶液中的M0 SC-II-tBu-Ni和M0 SC-II-tBu-Co的类似结合性质所证明的。两种MOSC显示出相当的结合常数和吸附钙。7当量的亚甲蓝（MB）和约1.5当量的水。30当量阿司匹林的氯仿溶液相比之下，固态MOSC的客体结合行为揭示了更多的变化。在固液界面处，MOSC-II-tBu-Co吸附Ca. S当量的MB从水溶液中以比MOSC-II-tBu-Ni快得多的速率。然而，在固-气界面处，MOSC-II-tBu-Ni具有比MOSC-II-tBu-Co更高的气体吸收，这与从晶体结构推断的它们的总体孔隙率相矛盾。这种差异是由于溶剂排空后MOSC的固态包装部分塌陷造成的。据推测，孔隙塌陷的程度与MOSC的分子大小相关，即，MOSC越大，孔隙率损失就越严重。相同的原理可以使在较大的MOSC-II-tPen-Co和MOSC-II-tOC-Ni/Mg/Co分子中看到的可忽略的N-2和O-2吸附合理化。MOSC-II-tPen-Ni具有中等分子尺寸，并以这样的方式承受部分结构崩溃，即所得的孔尺寸允许包含动力学上较小的O-2（3.46埃），但排除较大的N-2（3.64埃），解释了观察到的显著的O-2/N-2吸附选择性。
The phase-dependent host-guest binding behavior of a new family of synthetic supercontainers has been probed in homogeneous solution and at liquid-liquid, solid-liquid, and solid-gas interfaces. The synthetic hosts, namely, type II metal-organic supercontainers (MOSCs), are constructed from the assembly of divalent metal ions, 1,4-benzenedicarboxylate (BDC) linker, and sulfonylcalix[4]arene-based container precursors. One member of the MOSCs, MOSC-II-tBu-Ni, which is derived from Ni(II), BDC, and p-tert-butylsulfonylcalix[4] arene (TBSC), crystallizes in the space group R (3) over bar and adopts pseudo face-centered cubic (fcc) packing, whereas other MOSCs, including TBSC analogue MOSC-II-tBu-Co, p-tert-pentylsulfonylcalix[4]arene (TPSC) analogues MOSC-II-tPen-Ni/Co, and p-tert-octylsulfonylcalix[4]arene (TOSC) analogues MOSC-II-tOc-Ni/Mg/Co, all crystallize in the space group I4/m and assume a pseudo body-centered cubic (bcc) packing mode. This solid-state structural diversity is nevertheless not reflected in their solution host-guest chemistry, as evidenced by the similar binding properties of MOSC-II-tBu-Ni and MOSC-II-tBu-Co in solution. Both MOSCs show comparable binding constants and adsorb ca. 7 equiv of methylene blue (MB) and ca. 30 equiv of aspirin in chloroform. In contrast, the guest-binding behavior of the MOSCs in solid state reveals much more variations. At the solid-liquid interface, MOSC-II-tBu-Co adsorb ca. S equiv of MB from an aqueous solution at a substantially faster rate than MOSC-II-tBu-Ni does. However, at the solid-gas interface, MOSC-II-tBu-Ni has higher gas uptake than MOSC-II-tBu-Co, contradicting their overall porosity inferred from the crystal structures. This discrepancy is attributed to the partial collapse of the solid-state packing of the MOSCs upon solvent evacuation. It is postulated that the degree of porosity collapse correlates with the molecular size of the MOSCs, i.e., the larger the MOSCs, the more severe they suffer from the loss of porosity. The same principle can rationalize the negligible N-2 and O-2 adsorption seen in the larger MOSC-II-tPen-Co and MOSC-II-tOC-Ni/Mg/Co molecules. MOSC-II-tPen-Ni features an intermediate molecular size and endures a partial structural collapse in such a way that the resulting pore dimension permits the inclusion of kinetically smaller O-2 (3.46 angstrom) but excludes larger N-2 (3.64 angstrom), explaining the observed remarkable O-2/N-2 adsorption selectivity.