Nucleoside-based organogelators: gelation by the G–G base pair formation of alkylsilylated guanosine derivatives

2′,3′-O-Isopropylideneguanosine derivatives 1a–c having a bulky alkylsilyl moiety showed excellent gelation ability in alkane solvents. IR spectra of the gel clearly showed the absence of hydrogen bonding interaction at the C(6)double bond; length as m-dashO position and, together with a CD study, a G–G base pair formation by double N(2)H⋯N(3) and additional N(2)H⋯O(2′) hydrogen bonds was indicated. X-ray diffraction and SEM studies of the xerogel and AFM observation of the transferred gel suggested the formation of a two-dimensional supramolecular assembly 2 nm in thickness. The G–G base pair formation is discussed in terms of the molecular packing in the two-dimensional assemblies.