Poly(propylene imine) dendrimer complexes of Cu(II), Zn(II), and Co(III) as catalysts of hydrolysis of bis-(p-nitrophenyl) phosphate

Poly(propylene imine) dendrimers having 8, 32, and 64 primary amine end gro ups (D8, D32, and D64) form Cu(II), Zn(II), and Co(III) complexes that are identified spectrophotometrically. Solutions of D32 containing 2 or 4 prima ry amine groups per metal ion catalyze the hydrolysis of bis(p-nitrophenyl) phosphate in unbuffered NaClO4 solutions at 45 degrees C with rate maxima at pH 6.6-7.25. The observed rate constants for all 3.0 mM Co(III) and Cu(I I) complexes were about 7.10(-5) s(-1), and for 1.5 mM Zn(II) at 2 NH2/Zn w as 6.10(-5) s(-1). The results are consistent with the accepted mechanisms of electrophilic metal ion catalysis of hydrolysis of phosphate diesters by nucleophilic attack of metal-bound hydroxide ion on bis(p-nitrophenyl) pho sphate. (C) 1999 Elsevier Science B.V. All rights reserved.