Facile Self-Assembly of Neutral Dendritic Metallocycles via Oxygen-to-Platinum Coordination

A new approach for the fabrication of neutral dendritic metallocycles is described. By combining rigid 120° dicarboxylate donor linkers funtionalized with [G0]−[G3] Fréchet-type dendrons and complementary rigid 60° and 120° di-Pt(II) acceptor subunits, neutral rhomboidal metallodendrimers and hexagonal metallodendrimers, respectively, were prepared under mild conditions in high yields. The assemblies have well-defined shapes and sizes and were characterized by multinuclear NMR (1H and 31P), mass spectrometry (ESI (+)-TOF-MS and APPI(+)-TOF-MS), and elemental analysis. Isotopically resolved mass spectrometry data support the formation of the neutral [2 + 2] rhomboidal, and [3 + 3] hexagonal metallodendrimers, and NMR data are consistent with the formation of all ensembles. The structures of the [G0] and [G1] neutral rhomboidal metallodendrimers (3a and 3b) were unambiguously confirmed via single-crystal X-ray crystallography. The shape and size of [G3] neutral hexagonal metallodendrimer 5d was established with MMFF force-field simulations.