Mesoscopic-scale sheet-like assembly: critical role of inter-tape hydrogen bonds in the organogel formation and gel–liquid crystal transition of an alkylsilylated deoxyguanosine–dodecane system

Abstract

2′-Deoxy-3′,5′-bis-O-(octyldiisopropylsilyl)guanosine (1) showed a good gelation ability for non-polar solvents like alkanes. Atomic force micrography of the organogel showed the formation of mesoscopic-scale sheet-like assemblies, whose width and height were 50–300 and 2.5 nm, respectively. From the IR spectral analysis and crystallographic data of reference compounds, the gel was shown to have a structural hierarchy with different levels of hydrogen bonds, i.e., a one-dimensional tape motif with double hydrogen bonds between guanine units and a mesoscopic-scale sheet-like assembly with hydrogen bonds between adjacent tape motifs. Formation of the sheet structure was shown to be essential for the gelation process. On heating, the concentrated 1–dodecane (37–63 wt%) gel showed gel (G)–lamellar liquid crystal (L)–isotropic fluid (I) phase, and the G–L transition was ascribed to the cleavage of the inter-tape hydrogen bonds.