M₂⁴⁺ paddlewheel clusters as junction points in single-chain nanoparticles

We report the formation of well-defined copper and molybdenum single-chain nanoparticles, exhibiting metal clusters (M₂⁴⁺) as junction points. Upon addition of dimetallic precursor complexes [Cu₂(OAc)₄] and [Mo₂(OAc)₄], carboxylic acid functionalized polymer chains collapse into nanoparticles containing a M₂⁴⁺ (M = Cu, Mo) centered paddlewheel folding moiety. This synthetic strategy allows a high crosslinking per metal unit and the incorporation of an adjustable number of dimetallic centers into a single polymer chain. The successful formation of M₂-SCNPs is evidenced by size exclusion chromatography and diffusion-ordered NMR spectroscopy. Detailed insight into the dimetallic folding unit is provided by ¹H/²H NMR-, IR-, Raman- and UV-Vis spectroscopy as well as comparative analyses of molecular dicopper and dimolybdenum model-complexes. For the first time, M₂⁴⁺ paddlewheel folding motifs, including quadruple bonded dimetallic units, as in the case of Mo₂⁴⁺, are utilized as structure forming elements in the realm of SCNP chemistry.