Kinetic analysis of carboxy ester hydrolysis by a dinuclear Zn(II) complex.
A dinuclear Zn(II) complex with hexaaza macrocyclic ligand bearing two 2-hydroxypropyl pendants, 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxypropyl)-tricyclo [22,2,2,2(11,14)]triaconta-11,13,24,26,27,29-hexane (L) was synthesized and studied as a catalyst of the cleavage of 4-nitrophenyl acetate (NA). X-ray diffraction analysis of [Zn(2)LCl(2)]Cl(2)(.)6H(2)O revealed that Zn(II) adopts a trigonal-bipyramidal geometry. The complexation constants of L with Zn(II) have been determined at 298 K by means of potentiometric titration. [Zn(2)H(-2)L](2+) is the dominant species in aqueous solution around pH 8. The Zn(2)L-promoted hydrolysis of NA showed a second-order rate constant of 0.33 M(-1)s(-1) at pH 9.0, and the main promoter species are concluded to be the deprotonated species [Zn(2)H(-2)L](2+).
Huang
Jin
J
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China. chem1121@netra.nju.edu.cn
Li
Dong-Feng
DF
Li
Shu-An
SA
Yang
De-Xi
DX
Sun
Wei-Yin
WY
Tang
Wen-Xia
WX