Heterodinuclear Zn(II)-Fe(III) and Homodinuclear M(II)-M(II) [M = Zn and Ni] complexes of a Bicompartmental [NO] ligand as synthetic mimics of the hydrolase family of enzymes.

Heterodinuclear mixed valence [Zn(II)-Fe(III)] and the homodinuclear [Zn(II)-Zn(II)] and [Ni(II)-Ni(II)] complexes of a bicompartmental ligand containing a bridging phenoxy as a O-donor and four pyridyl moieties and two amine moieties as the N-donors exhibit phosphoester hydrolysis activity similar to the hydrolase family of enzymes. While the heterodinuclear [Zn(II)-Fe(III)] (2) complex was obtained by the sequential addition of Fe(NO)∙9HO and Zn(OAc)∙2HO to the ligand 2,6‑bis{[bis(2‑pyridylmethyl)amino]methyl}‑4‑t‑butylphenol (HL) (1) in moderate yield of 37%, the homodinuclear [Zn(II)-Zn(II)] (3) and [Ni(II)-Ni(II)] (4) complexes were obtained by the direct reaction of the ligand (1) with Zn(OAc)∙2HO and Ni(OAc)∙2HO respectively, in good to moderate yields (43-63%). Based on the spectrophotometric titration and the mass spectrometry studies, a monoaquated and dihydroxo species 2C, 3C and 4C has been identified as the catalytically active species responsible for the phosphodiester hydrolysis of the bis(2,4 - dinitrophenyl)phosphate (2,4 - BDNPP) substrate in the pH range 5.5-10.5. The kinetic studies further revealed that the homodinuclear [Ni(II)-Ni(II)] complexes (4) (k = 1.26 × 10 s) is more active by 39 times than the homodinuclear [Zn(II)-Zn(II)] complexes (3) (k = 3.20 × 10 s) and 27 times more active than the heterodinuclear [Zn(II)-Fe(III)] complex (2) (k = 4.62 × 10 s) in the phosphodiester hydrolysis activity. Significantly enough, the catalyst-substrate adduct species (2E, 2F and 3F) containing a metal bound bis(2,4‑dinitrophenyl)phosphate has been detected by mass spectrometry for the first time.