Poly (propylene imine) Dendrimer Complexes of Cu(II), Zn(II), and Co(III), as Catlyst of Hydrolysis of p-Nitrophenyl Diphenyl Phosphate

摘要

Poly (propylene imine) dendrimers having 8, 32, and 64 primary amine end groups form diamino Cu(II), diamino Zn(II), and tetramino Co(III) complexes that are identified spectrophotometrically and titrimetrically. The dendrimer-metal ion complexes catlyze the hydrolysis of p-nitrophenyl diphenyl phosphate in zwitterionic buffer solutions at pH V<= 8.1 with relative activies Cu(II) > Zn (II) > Co(III). The rates of hydrolysis are faster with sodium perchlorate than with sodium chloride to control ionic strength.In soldium perchlorate solutions with Cu(II) teh rates increase with increasing size of the dendrimer. In sodium chloride solutions with Cu(II) the rates decrease with increasing size of the dendrimer. Rate constants in buffered sodium chloride solutions of dendrimers and 1.0 mM Cu(II) are 1.3-6.3 times faster than in the absence of Cu(II). The fastest hydrolyses occurred at a dendrimer primary amine to Cu(II) ratio NH_2/Cu <= 2. At NH_2/Cu = 4 and with the 1,4,7,10-tetraazacyclodencane complex of Cu(II) hydrolysis rates were much much slower.