Directed self-assembly using inorganic coordination chemistry is an attractive approach for making functional supramolecular structures. In this article, the synthesis and characterization of Ru(bpy)32+ compounds derivatized with aminoethylglycine (aeg) substituents containing pendant bipyridine (bpy) ligands is presented. The free bpy ligands in these complexes are available for metal chelation to form coordinative cross-links; addition of Cu2+ or Zn2+ assembles heterometallic structures containing two or three transition-metal complexes. Control over relative placement of metal complexes is accomplished using two strategies: two bipyridine-containing aeg strands tethered to Ru(bpy)32+ allow intramolecular coordination and result in a dimetallic hairpin motif. Ru(bpy)32+ modified with a single strand forms intermolecular cross-links forming the trimetallic complex. Each of these is characterized by a range of methods, and their photophysical properties are compared. These data, and comparison to an acetyl aegmodified Ru(bpy) 32+ complex, confirm that the metal ions cross-link bpy-containing aeg strands. Heterometallic complexes containing bound Cu 2+ cause a dramatic reduction in the Ru(bpy)32+ quantum yields and lifetimes. In contrast, the Ru(bpy)32+ hairpin with coordinated Zn2+ has only a slight decrease in quantum yield but no change in lifetime, which could be a result of steric impacts on structure in the dimetallic species. Analogous effects are not observed in the trimetallic Ru-Zn-Ru structures in which this constraint is absent. Each of these heterometallic structures represents a facile and reconfigurable means to construct multimetallic structures by metal-coordination-based self-assembly of modular artificial peptide units.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry