Abstract
The homodinuclear [Fe(III)-Fe(III)] (2) and [Zn(II)-Zn(II)] (3) complexes of binucleating [N4O3] symmetrical ligand (1) of the formulation, H3L (L = 2,6-bis{[(2-hydroxybenzyl)(2-pyridylmethyl)amino]methyl}-4-t-butylphenolate), display purple acid phosphatase (PAP) and zinc phosphoesterase like activity. For the two complexes, the spectrophotometric titration and the ESI-MS studies supported the existence of an equilibrium between a triaquated species, {L[(H2O)Fe-III(mu-H2O)Fe-III(H2O)]}(3+) (2A) and {L[(H2O)Zn-II(mu-H2O)Zn-II(H2O)]}(+) (3A), a diaquated and monohydroxo species, {L[(H2O)Fe-III(mu-H2O)Fe-III(OH)]}(2+) (2B) and {L[(H2O)Zn-II(mu-H2O)Zn-II(OH)]} (3B), a monoaquated and dihydroxo species, {L[(H2O)Fe-III(mu-OH)Fe-III(OH)]}(+) (2C) and {L[(H2O)Zn-II(mu-OH)Zn-II(OH)]}(-) (3C), and a trihydroxo species, {L[(HO)Fe-III(mu-OH)Fe-III(OH)]} (2D) and {L[(HO)Zn-II(mu-OH)Zn-II(OH)]}(2-) (3D), depending upon the pH of the solution. Of these, the active species namely, a monoaquated and dihydroxo species, {L[(H2O)Fe-III(mu-OH)Fe-III(OH)]}(+) (2C) and {L[(H2O)Zn-II(mu-OH)Zn-II(OH)]}(-) (3C), hydrolyzed an activated substrate bis(2,4-dinitrophenyl)phosphate at the pH range of 5.5-10.5, displaying Michealis-Menton kinetics. Significantly enough, the catalyst-substrate adduct of the type {L[Fe-III(mu-OH)(mu-RPO4)Fe-III]} (2F) has been detected by ESI-MS for the dinuclear [Fe(III)-Fe(III)] complex (2). (C) 2018 Elsevier Ltd. All rights reserved.