Coexistence of Distinct Supramolecular Assemblies in Solution and in the Solid State
Coexistence of Distinct Supramolecular Assemblies in Solution and in the Solid State
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不同超分子组装体在溶液和固态中的共存
DOI：
10.1002/chem.201605975
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Reddy G
中科院分区：
文献类型：
--
作者：
Reddy G
亲脂性鸟苷衍生物在溶液和固体状态下形成了不同的超分子组装体，包括亚稳态物质。根据阳离子、阴离子和盐浓度的性质，在氯仿中形成结构不同的基于G-四重态的组装体，如通过圆二色谱和时程扩散有序NMR光谱数据表征的。有趣的是，即使在氯仿中稳定G-四重态的钾离子的存在也不足以将这些组装体完全保持在固态，导致形成混合的四重态和带状组装体，如快速魔角旋转（MAS）NMR光谱所揭示的。不同的N-H N和N-H O分子间氢键相互作用驱动四重态和带状自组装，导致明显不同的2D 1H固态NMR光谱，从而有助于直接识别混合组装体。溶解NMR实验证实四重态和带状相互转化是可逆的-进一步证明了在固态到溶液态转变时亲脂性核苷的自组装过程中发生的变化，反之亦然。对不同阳离子（K+、Sr 2+）和阴离子（苦味酸盐、乙酸盐和碘化物）络合作用的系统研究强调，稳定溶液或固态结构的存在可能并不反映同一超分子实体在另一相中的稳定性。
The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G‐quartet‐based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion‐ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G‐quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon‐like assemblies as revealed by fast magic‐angle spinning (MAS) NMR spectroscopy. Distinct N−H⋅⋅⋅N and N−H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon‐like self‐assembly resulting in markedly different 2D1H solid‐state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible–further demonstrating the changes that occur in the self‐assembly process of a lipophilic nucleoside upon a solid‐state to solution‐state transition and vice versa. A systematic study for complexation with different cations (K+, Sr2+) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid‐state structure may not reflect the stability of the same supramolecular entity in another phase.