Abstract
The partially hydrophilic and hydrophobic tripodal ligands, tris(hydroxy-2-benzimidazolylmethyl)amine
L1h and tris(2-benzimidazolyl)amine
L1 were used for the preparation of biomimetic complex of carbonic anhydrase. The CO
2 hydration using [L1hZn(OH)]ClO
4
·
1.5H
2O provided the zinc-bound and free HCO
3
−s, which were formed by nucleophilic attack of Zn–OH toward CO
2 in dimethyl sulfoxide (DMSO). The phenolic OH in
L1h can recognize water molecules through hydrogen bonds to facilitate the collection of the water molecules around a biomimetic zinc compound; the molecular structure of [L1hZn(OH)]
+ was revealed. The packing diagram has demonstrated the all the water molecules are hydrogen bonded to each phenolic OH. The nucleophilic attack of zinc-bound OH
− to substrate is used to catalyze the CO
2 hydration and phosphoester hydrolysis. The carbonic anhydrase model compound [L1Zn(OH
2)]
2+ was applied for the hydrolysis of phosphoesters, parathion and bis(
p-nitrophenyl)phosphate (BNPP
−). The low reactivity of [L1Zn(OH)]
+ for parathion hydrolysis is attributed to the stability of the intermediate [L1Zn(OP(S)(OEt)
2)]
+. Since the structures of the intermediates [L1Zn(OH
2)](BNPP)
2 (
1) and [L1Zn(OP(S)(OEt)
2)]ClO
4 (
2) formed on the way of hydrolysis are too stable to realize the catalytic cycle and are not active for hydrolysis, carbonic anhydrase model compound [L1Zn(OH
2)]
2+ was not suitable for phosphoester hydrolysis; the zinc model compound surrounded by three benzimidazolyl groups is used to have the steric hindrance for bulky substrate, such as parathion and BNPP
−.