A multi-O\u3csub\u3e2\u3c/sub\u3e complex derived from a copper(I) dendrimer

Abstract

\u3cp\u3eThe high-pressure reaction of 2-vinylpyridine with the primary amines of four consecutive generations of poly(propylene imine) dendrimers (DAB-dendr- (NH\u3csub\u3e2\u3c/sub\u3e)(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\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e was studied by \u3csup\u3e1\u3c/sup\u3eH NMR titration, and the complexation of all new dendrimers with Cu(II)(ClO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e 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 fourth-generation dendrimer DAB-dendr-(PY2)\u3csub\u3e32\u3c/sub\u3e in dichloromethane with [Cu(I)(CH\u3csub\u3e3\u3c/sub\u3eCN)\u3csub\u3e4\u3c/sub\u3e](ClO\u3csub\u3e4\u3c/sub\u3e) in acetonitrile revealed that approximately 30 Cu(I) ions were bound. Low-temperature UV/Vis spectroscopy of this complex in dichloromethane at -85°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.\u3c/p\u3