Metallodendrimers in three oxidation states with electronically interacting metals and stabilization of size-selected gold nanoparticles.

Metallodendrimers containing redox-robust centres may have applications in molecular redox recognition, sensing, biosensing and catalysis. So far, however, no metallodendrimer is known in several oxidation states. Here we report metallodendrimers with two electronically communicating iron centres that are stable and isolated in both the Fe(II) and Fe(III) oxidation states, and in addition as class-II mixed-valent Fe(II)Fe(III) complexes. These dendrons are branched to arene-centred dendrimer cores either by Sonogashira coupling or 'click' reactions. The latter reaction involves the introduction of intradendritic 1,2,3-triazolyl ligands, which allows investigation of the selective role of these ligands in intradendritic Au(III) coordination and Au(0) nanoparticle stabilization. As a result, and using the various metallodendrimers with different oxidation states, small Au(0) nanoparticles are intradendritically stabilized by the triazole ligands, whereas with the related non-'click' dendrimers large Au(0) nanoparticles are formed outside the dendrimers and stabilized by a group of dendrimers.