POLY-HETERO-OMEGA-FUNCTIONALIZED ALKANETHIOLATE-STABILIZED GOLD CLUSTER COMPOUNDS

This paper describes two synthetic approaches, simultaneous and stepwi se exchange, to poly-hetero-omega-functionalized monolayer-protected c luster compounds (MPC's), as well their spectroscopic and electrochemi cal characterization. Poly-hetero-omega-functionalization of MPC's pro vides a framework within which to study intra-and intermolecular clust er chemistry and to design multistep, mutually supporting catalytic an d electron donor/acceptor reactions on cluster surfaces. Factors affec ting the extent of exchange (measured by NMR) include the steric bulk of the omega-functional group as well as the chain lengths of the prot ecting and incoming ligands. Poly-hetero-omega-functionalized clusters can incorporate mixed redox functions as illustrated by microelectrod e voltammetry of a poly-ferrocene/anthraquinone mixed cluster. The clu ster voltammetric waves lie at potentials consistent with those observ ed in dilute solutions of the unbound electroactive thiols, within the uncertainty of the Ag quasi-reference electrode potential. Diffusion coefficients and hydrodynamic radii suggest that the outer parts of th e cluster chains may be free-draining. This research demonstrates that 3D-SAMs with mixed omega-functionalized alkanethiolate ligands (both redox and nonredox active) can be synthesized and characterized and pr ovides the groundwork for synthesis of ''nanofactory'' cluster compoun ds designed to exhibit mutually supporting, multistep chemical and red ox catalytic reactions, and for an enhanced capacity to study function al group reactivities at organized monolayer interfaces.