A Multi-O_2 Complex Derived from a Copper (I)Dendrimer

摘要

The high-pressure reaction of 2-vinylpyridine with the primary amines of four consecutive generations of poly(propylene imine)dendrimers (DAB-dendr-(NH_2)_n)(n=4,8,16,32)yielded dendrimers with bis[2-(2-pyridyl)ethyl]amine (PY2) ligands. The complexation of the new dendrimers with metal ions was investigated by a variety of techniques. The reaction of the first- and fourth-generation dendrimers (n=4 and 32, respectively)with Zn~(II)(ClO_4)_2 was studied by ~1H NMR titration, and the complexation of all new dendrimers with Cu~(II)(ClO_4)_2 was investigated by UV/Vis and EPR spectroscopy. Quantitative coordination of one metal ion per PY2 group was demonstrated in all cases. A UV/Vis titration of the fourthgeneration dendrimer DAB-dendr(PY2)_(32) in dichloromethane with [Cu~I(CH_3CN)_4](ClO_4)in acetonitrile revealed that approximately 30 Cu~1 ions were bound. Low-temperature UV/Vis spectroscopy of this complex in dichloromethane at -85deg C in the presence of dioxygen showed that approximately 60-70% of the copper centers can bind dioxygen, corresponding to 10-11 of these molecules per dendrimer molecule. This complex can be considered a synthetic analogue of hemocyanin, the copper-containing oxygen transport protein from the hemolymph of molluscs and arthropods.