Premium
An Unsymmetric Ligand with a N 5 O 2 Donor Set and Its Corresponding Dizinc Complex: A Structural and Functional Phosphoesterase Model
Author(s) -
Das Biswanath,
Daver Henrik,
PyrkoszBulska Monika,
GumiennaKontecka Elzbieta,
Himo Fahmi,
Nordlander Ebbe
Publication year - 2018
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201701416
Subject(s) - chemistry , deprotonation , hydroxide , zinc , nucleophile , hydrolysis , ligand (biochemistry) , potentiometric titration , catalysis , medicinal chemistry , stereochemistry , inorganic chemistry , ion , organic chemistry , biochemistry , receptor
To mimic the active sites of the hydrolytic enzyme zinc phosphotriesterase, a new dinucleating unsymmetric ligand, PICIMP (2‐{[2‐hydroxy‐5‐methyl‐3‐({[(1‐methyl‐1 H ‐imidazol‐2‐yl)methyl](pyridin‐2‐ylmethyl)amino}methyl)benzyl][(1‐methyl‐1 H ‐imidazol‐2‐yl)methyl]amino}acetic acid), has been synthesized and characterized. The hydrolytic efficacy of the complex solution (PICIMP/ZnCl 2 = 1:2) has been investigated using bis‐(2,4‐dinitrophenyl)phosphate (BDNPP), a DNA analogue substrate. Speciation studies were undertaken by potentiometric titrations at varying pH for both the ligand and the corresponding dizinc complex to elucidate the formation of the active hydrolysis catalyst; these studies reveal that the dinuclear zinc(II) complexes, [Zn 2 (PICIMP)] 2+ and [Zn 2 (PICIMP)(OH)] + predominate in solution above pH 4. The obtained p K a of 7.44 for the deprotonation of water suggests formation of a bridging hydroxide between the two Zn II ions. Kinetic investigations of BDNPP hydrolysis over the pH range 5.5–10.5 have been performed. The cumulative results indicate the hydroxo‐bridged dinuclear Zn II complex [Zn 2 (PICIMP)(µ‐OH)] + as the effective catalyst. Density functional theory calculations were performed to investigate the detailed reaction mechanism. The calculations suggest that the bridging hydroxide becomes terminally coordinated to one of the zinc ions before performing the nucleophilic attack in the reaction.