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The Self‐Assembly of Lipophilic Guanosine Derivatives in Solution and on Solid Surfaces
Author(s) -
Gottarelli Giovanni,
Masiero Stefano,
Mezzina Elisabetta,
Pieraccini Silvia,
Rabe Jürgen P.,
Samorí Paolo,
Spada Gian Piero
Publication year - 2000
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 - 10.1002/1521-3765(20000901)6:17<3242::aid-chem3242>3.0.co;2-k
The self‐assembly of lipophilic deoxyguanosine derivatives 1 and 2 has been studied in solution by NMR spectroscopy and ESI‐MS (electrospray ionization mass spectrometry). NMR data show the existence of two types of self‐assembled, ribbonlike structures ( A and B ), which are connected at the guanine moieties through two different H‐bonded networks. The first species ( A ), which is stable in the solid state and characterised by cyclic NH(2)−O(6) and NH(1)−N(7) hydrogen bonds, is detected soon after dissolving the polycrystalline powder in rigorously anhydrous CDCl 3 . In solution it slowly undergoes a structural transition towards a thermodynamically stable ribbon characterised by NH(1)−O(6) and NH(2)−N(3) cyclic hydrogen bonds ( B ). On the other hand, at surfaces, self‐assembled ribbon nanostructures have been grown from solutions of derivative 1 both on mica and at the graphite–solution interface. They have been investigated by means of tapping mode scanning force microscopy (SFM) and scanning tunnelling microscopy (STM), respectively. SFM revealed dry, micrometer‐long nanoribbons with a molecular cross‐section, while STM imaging at submolecular resolution indicates a molecular packing of type A , like the one detected in the solid state. This indicates that, upon adsorption at the solid–liquid interface, the guanosine moieties undergo a structural rearrangement from a B‐ type to an A‐ type ribbon.