通过由溶剂决定的弱超分子相互作用折叠或聚集的大合成分子,ACS Omega

当前位置： X-MOL 学术 › ACS Omega › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

通过由溶剂决定的弱超分子相互作用折叠或聚集的大合成分子
ACS Omega ( IF 3.7 ) Pub Date : 2019-06-11 00:00:00 , DOI: 10.1021/acsomega.9b01050
Cristina Oliveras-González ₁ , Mathieu Linares _{2,

2,

2} , David B Amabilino _{3,

4} , Narcis Avarvari ₁

Affiliation

在弱溶剂化介质中，大盘状分子之间的弱非共价相互作用通常会导致分子彼此堆叠的纤维的形成。在这里，我们表明，大芳香族部分之间的特定手性间隔基团通常导致柱状堆叠，在这种情况下，在相对极性的溶剂中产生分子内折叠结构，但在非常非极性的溶剂中形成有限的聚集体。显示这种行为的分子具有C ₃对称苯-1,3,5-三(3,3'-二酰氨基-2,2'-联吡啶) (BTAB) 核心，并通过短手性间隔基附加三个金属卟啉单元。通过该化合物在溶液中的圆二色性 (CD) 光谱可以明显看出相当明确的发色团排列，其中观察到清晰的卟啉激子耦合带。在分子分散的极性较大的溶剂中，由于分子内折叠，观察到相对较弱的 CD 信号，这一特征已通过分子模型得到证实。通过测量C ₂对称类似物的CD来确认分子内折叠。通常预计在非极性溶剂中以手性排列堆叠的C ₃对称 BTAB核心没有显示 CD 的迹象，表明没有通过它进行手性转移（尽管 2,2'-联吡啶的预期平面构象）单位通过NMR波谱法确认）。卟啉结合在由手性单元间隔的 3,3'-二氨基-2,2'-联吡啶部分上，使得后者无法通过超分子 π-π 堆积进行组装。相反，建模表明，由于范德华相互作用，三个金属卟啉单元相互作用，有利于它们比 BTAB 单元更紧密的相互作用。原子力显微镜显示，与具有相同核心的分子的其他例子相比，C ₃对称分子更倾向于盘状聚集体（而不是纤维状一维聚集体）。封闭结构是通过卟啉环的非定向互锁形成的。刚性核心和卟啉部分之间的手性间隔基对于确定极性或极性较小溶剂中的结果无疑很重要，因为模型显示分子中的这种连接具有两种有利的构象，使分子相对平坦或凸出。

"点击查看英文标题和摘要"

Large Synthetic Molecule that either Folds or Aggregates through Weak Supramolecular Interactions Determined by Solvent

Weak noncovalent interactions between large disclike molecules in poorly solvating media generally lead to the formation of fibers where the molecules stack atop one another. Here, we show that a particular chiral spacing group between large aromatic moieties, which usually lead to columnar stacks, in this case gives rise to an intramolecularly folded structure in relatively polar solvents, but in very apolar solvents forms finite aggregates. The molecule that displays this behavior has a C₃ symmetric benzene-1,3,5-tris(3,3′-diamido-2,2′-bipyridine) (BTAB) core with three metalloporphyrin units appended to it through short chiral spacers. Quite well-defined chromophore arrangements are evident by circular dichroism (CD) spectroscopy of this compound in solution, where clear exciton coupled bands of porphyrins are observed. In more polar solvents where the molecules are dispersed, a relatively weak CD signal is observed as a result of intramolecular folding, a feature confirmed by molecular modeling. The intramolecular folding was confirmed by measuring the CD of a C₂ symmetric analogue. The C₃ symmetric BTAB cores that would normally be expected to stack in a chiral arrangement in apolar solvents show no indication of CD, suggesting that there is no transfer of chirality through it (although the expected planar conformation of the 2,2′-bipyridine unit is confirmed by NMR spectroscopy). The incorporation of the porphyrins on the 3,3′-diamino-2,2′-bipyridine moiety spaced by a chiral unit leaves the latter incapable of assembling through supramolecular π–π stacking. Rather, modeling indicates that the three metalloporphyrin units interact, thanks to van der Waals interactions, favoring their close interactions over that of the BTAB units. Atomic force microscopy shows that, in contrast to other examples of molecules with the same core, disclike aggregates (rather than fibrillar one dimensional aggregates) are favored by the C₃ symmetric molecule. The closed structures are formed through nondirectional interlocking of porphyrin rings. The chiral spacer between the rigid core and the porphyrin moieties is undoubtedly important in determining the outcome in polar or less polar solvents, as modeling shows that this joint in the molecule has two favored conformations that render the molecule relatively flat or convex.

更新日期：2019-06-11

点击分享查看原文

点击收藏

公开下载

阅读更多本刊最新论文本刊介绍/投稿指南

全部期刊列表>>