Au_(25) Nanoclusters Capped by Photoactive Aib-based Peptide Ligands

摘要

Nanostructured materials are essential elements of new technologies and biomedical research. Monolayer-protected gold nanoclusters (MPC) with a core diameter <1.5 nm are of particular interest because electronic-band energetics leads to quantum confinement effects, thereby causing these MFCs to display molecule-like properties, such as a well defined HOMO-LUMO gap [1,2]. The monolayer not only protects the core from particle aggregation but also furnishes a way to control the electrochemical, optical, and chemical properties of the MPC itself. Peptides based on the α-aminoisobutyric (Aib) acid unit are very interesting molecules because they form stiff 3]o-helices and also they are short [3]. Thiolated Aib peptides can be used to stabilize particularly small MPCs [4] and we showed that, due to their strong dipole moment, these peptides affect the MPC energy levels and thus its electrochemical behavior [51. Here we report the synthesis and properties of gold MPCs modified by ligand exchange with a thiolated azoben-zene peptide, HS-CH2CH2-Ph-N=N-Ph-CO-Aib3-NH/Bu. We speculated that trans-cis isomerization of the N=N bond would have changed the orientation of the peptide dipole moment with respect to the nanoparticle core and, consequently, modified the MPC properties.