Silica-bound copper(II)triazacyclononane as a phosphate esterase: effect of linker length and surface hydrophobicity.
A series of silica-bound Cu(ii) triazacyclononane materials was prepared to study the effect of linker length and surface hydrophobicity on the hydrolysis of phosphate esters. The general synthetic approach for these heterogeneous reagents was rhodium-catalyzed hydrosilation between an alkenyl-modified triazacyclononane and hydride-modified silica followed by metallation with a Cu(ii) salt. Elemental analysis confirmed that organic functionalization of the silica gel was successful and provided an estimate of the surface concentration of triazacyclononane. EPR spectra were consistent with square pyramidal Cu(ii), indicating that Cu(ii) ions were bound to the immobilized macrocycles. The hydrolytic efficacies of these heterogeneous reagents were tested with bis(p-nitrophenyl)phosphate (BNPP) and diethyl 4-nitrophenyl phosphate (paraoxon). The agent that performed best was an octyl-linked, propanol-blocked material. This material had the most hydrophilic surface and the most accessible active site, achieving a rate maximum on par with the other materials, but in fewer cycles and without an induction period.
Bodsgard
Brett R
BR
Department of Chemistry, Saint Mary's University of Minnesota, Winona, Minnesota 55987, USA.
Clark
Robert W
RW
Ehrbar
Anthony W
AW
Burstyn
Judith N
JN
D003300:Copper / Q000737:chemistry*; D004950:Esterases / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
D004952:Esters; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D010710:Phosphates; C075712:1,4,7-triazacyclononane; D012822:Silicon Dioxide; D003300:Copper; D004950:Esterases