Guest Molecules Confined in Amphipathic Crystals as Revealed by X-ray Diffraction and MAS NMR

Multinuclear 1H−13C heterocorrelated (HETCOR) NMR spectroscopy combined with X-ray diffraction revealed the unusual dual properties of identical guest molecules confined in two crystallographically distinct host cavities within single crystals based on hexagonal frameworks comprising guanidinium ions and organomonosulfonates. The environments of the two cavities differ substantially, as one is lined by the highly polar quasihexagonal guanidinium-sulfonate network, while the other is defined by walls consisting of nonpolar aromatic groups. The effect of these different environments on the NMR properties of the guest molecules is evident from chemical shift data and two-dimensional HETCOR spectra. The large magnetic susceptibility effect due to ring currents of the aromatic hosts enables determination of the host−guest distances and suggests intermolecular CH···π interactions. The 13C relaxation times reveal the molecular dynamics of the guests in two nanoscale environments that differ with respect to shape and dimensionality.

多核1H−13C异核相关（HETCOR）核磁共振波谱法结合X射线衍射研究表明，在由胍离子与有机单磺酸盐构筑的六方骨架单晶中，限域于两种晶体学不同主体空腔内的同一客体分子展现出反常的双重特性。两种空腔的环境差异显著：其一内壁为高度极化的准六方胍-磺酸盐网络，另一者的内壁则由非极性芳香基团构成。上述不同环境对客体分子核磁共振性质的影响，可通过化学位移数据与二维HETCOR谱图得以体现。芳香主体环电流引发的显著磁化率效应，可用于测定主客体间距，同时也印证了分子间CH···π相互作用的存在。13C弛豫时间则揭示了客体分子在形状与维度均存在差异的两种纳米尺度空腔内的分子动力学行为。