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Co‐existence of Distinct Supramolecular Assemblies in Solution and in the Solid State
Author(s) -
Reddy G. N. Manjunatha,
Huqi Aida,
Iuga Dinu,
Sakurai Satoshi,
Marsh Andrew,
Davis Jeffery T.,
Masiero Stefano,
Brown Steven P.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201604832
Subject(s) - supramolecular chemistry , chemistry , crystallography , hydrogen bond , nuclear magnetic resonance spectroscopy , solid state nuclear magnetic resonance , intermolecular force , ribbon , nmr spectra database , magic angle spinning , stereochemistry , spectral line , molecule , crystal structure , organic chemistry , materials science , nuclear magnetic resonance , physics , astronomy , composite material
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 2D 1 H 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 + , Sr 2+ ) 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.