title: Mechanistic implications in the phosphatase activity of Mannich-based dinuclear zinc complexes with theoretical modeling.
abstract: An "end-off" compartmental ligand has been synthesized by an abnormal Mannich reaction, namely, 2-[bis(2-methoxyethyl)aminomethyl]-4-isopropylphenol yielding three centrosymmetric binuclear μ-phenoxozinc(II) complexes having the molecular formula [Zn2(L)2X2] (Zn-1, Zn-2, and Zn-3), where X = Cl(-), Br (-), and I (-), respectively. X-ray crystallographic analysis shows that the ZnO3NX chromophores in each molecule form a slightly distorted trigonal-bipyramidal geometry (τ = 0.55-0.68) with an intermetallic distance of 3.068, 3.101, and 3.083 Å (1-3, respectively). The spectrophotometrical investigation on their phosphatase activity established that all three of them possess significant hydrolytic efficiency. Michaelis-Menten-derived kinetic parameters indicate that the competitiveness of the rate of P-O bond fission employing the phosphomonoester (4-nitrophenyl)phosphate in 97.5% N,N-dimethylformamide is 3 > 1 > 2 and the kcat value lies in the range 9.47-11.62 s(-1) at 298 K. Theoretical calculations involving three major active catalyst forms, such as the dimer-cis form (D-Cis), the dimer-trans form (D-Trans), and the monoform (M-1 and M-2), systematically interpret the reaction mechanism wherein the dimer-cis form with the binuclear-bridged hydroxide ion acting as the nucleophile and one water molecule playing a role in stabilizing the leaving group competes as the most favored pathway.
authors.affiliation: Department of Chemistry, University of Calcutta , 92 A.P.C. Road, Kolkata 700009, India.
authors.forename: Ria
authors.initials: R
authors.lastname: Sanyal
authors.forename: Xuepeng
authors.initials: X
authors.lastname: Zhang
authors.forename: Priyanka
authors.initials: P
authors.lastname: Kundu
authors.forename: Tanmay
authors.initials: T
authors.lastname: Chattopadhyay
authors.forename: Cunyuan
authors.initials: C
authors.lastname: Zhao
authors.forename: Franz A
authors.initials: FA
authors.lastname: Mautner
authors.forename: Debasis
authors.initials: D
authors.lastname: Das
mesh_terms: D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D011789:Quantum Theory; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009942:Organometallic Compounds; D010744:Phosphoric Monoester Hydrolases; D015032:Zinc