title: Co-existence of Distinct Supramolecular Assemblies in Solution and in the Solid State.
abstract: 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.
authors.affiliation: Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK.
authors.forename: G N Manjunatha
authors.initials: GN
authors.lastname: Reddy
authors.affiliation: Dipartimento di Chimica "Giacomo Ciamician", Alma Mater Studiorum, Università di Bologna, 40126, Bologna, Italy.
authors.forename: Aida
authors.initials: A
authors.lastname: Huqi
authors.affiliation: Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK.
authors.forename: Dinu
authors.initials: D
authors.lastname: Iuga
authors.affiliation: JEOL (UK), Silver Court, Watchmead, Welwyn Garden City, AL7 1LT, UK.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sakurai
authors.affiliation: Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Marsh
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Jeffery T
authors.initials: JT
authors.lastname: Davis
authors.affiliation: Dipartimento di Chimica "Giacomo Ciamician", Alma Mater Studiorum, Università di Bologna, 40126, Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Masiero
authors.affiliation: Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK.
authors.forename: Steven P
authors.identifier: http://orcid.org/0000-0003-2069-8496
authors.initials: SP
authors.lastname: Brown
keywords: 2D double-quantum spectroscopy; NMR spectroscopy; fast magic-angle spinning; self-assembly; supramolecular chemistry