Synthesis of Self-Assembling Molecules for Functional Materials

The research carried out during these three years was developed as part of the MolArNet Project, supported by the European Commission, which aims at giving a first demonstration of molecular Quantum-dot Cellular Automata (QCA) elementary devices as a feasible approach to unconventional computation. Here we describe the design and synthesis of novel alkyl substituted guanosine-ferrocene derivatives, and their self-assembly at the solid/liquid interface on highly oriented pyrolitic graphite (HOPG). Supramolecular self-assembly of these derivatives has been accomplished in solutions by NMR and CD spectroscopy and on surface by STM and AFM techniques. We have shown that supramolecular structures formed by ferrocene-exposing guanosines in solutions and at surfaces can be tuned by introducing sterically demanding substituents, ranging from G-ribbons to G4 cation-free architectures. This self-assembly is governed by the formation of H-bonds between guanosines that dictates the spatial localization of ferrocenes, ultimately forming 1D conjugated arrays that may be employed as prototypes of supramolecular nanowires. In this thesis we also explored the possibility of using porphyrin derivatives carrying ferrocene residues directly connected to the porphin core, as alternative approach to QCA implementation. Preliminary electrochemical studies using cyclic voltammetry show that porphyrins can be used as a two/four dots cells. During the period at the University of Maryland, in the Prof. Jeffery Davis’ research group, I worked on the synthesis and characterization of specific dyes, containing azobenzene groups, in order to insert them in the guanosine hydrogels. These dyes are capable, in principle, to change their conformation in a reversible way, through an external light stimulus. Thus, it could be possible to obtain photoresponsive hydrophilic gels, able to break and reform themselves in a controlled manner.