Dinuclear zinc complexes of phenol-based "end-off" compartmental ligands: Synthesis, structures and phosphatase-like activity

The phenol-based compartmental ligands of the "end-off " type, 2,6-bis{N-[2-(dimethylamino)ethyl]iminomethyl}-4 -methylphenol (HL1), 2-{N-[2-(dimethylamino)ethyl]iminomethyl}-6-{N-methyl-N-[2-(dimethylamino)ethyl]aminomethyl}-4-bromophenol (HL2), 2,6-bis{2-[(2-pyridyl)ethyl]iminomethyl}-4-methylphenol (HL3) and 2-[N,N-di(2-pyridylmethyl)aminomethyl]-6- {N-[2-(dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL4), have formed dinuclear zinc complexes: [Zn-2(L-1)(AcO)(2)]PF6 (1), [Zn-2(L-1)(NCS)(3)] (2), [Zn-2(L-2)(AcO)(2)]PF6 (3), [Zn-2(L-2)(NCS)(3)] (4), [Zn-2(L-3)(AcO)(2)]PF6 (5), [Zn-2(L-3),(NCs)(3)] (6), [Zn-2(L-4)(AcO)(2)]ClO4 (7), [Zn-2(L-4)(AcO)(NCS)(2)] (8) and [Zn-2(L-4)(NCs)(3)] (9). The crystal structures of 1,5.(DMF)(0.5)(2PrOH)(0.5), 7 . CHCl3, 8 . (2-PrOH) and 9 . 3CHCl(3) have been determined. Complexes 1 and 5.(DMF)(0.5)(2-PrOH)(0.5) have a di-mu -acetato-mu -phenolato-dizinc(II) core comprised of two square-pyramidal Zn centers. 7 . CHCl3 has a similar dinuclear core, but it is comprised of one square-pyramidal Zn and one pseudo-octahedral Zn. 8 . (2-PrOH) has a mu -acetato-mu -phenolato-dizinc(II) core with a unidentate thiocyanato-N group on each Zn. 9 . 3CHCl(3) exists in two different crystals: one has a mu -thiocyanato-N-mu -phenolato-dizinc(II) core, whereas the other has a mu -phenolato-dizinc(II) core. The diacetato complexes, 1, 3, 5 and 7, are stable in solution. Hydrolytic activities of the complexes toward tris(p-nitrophenyl) phosphate (TNP) have been studied in aqueous DMF by means of UV-visible spectroscopic and P-31 NMR methods. Complexes 1, 3 and 5 have an activity to hydrolyze TNP into bis(p-nitrophenyl) hydrogen-phosphate (HBNP) in aqueous DMF. In contrast, 7 showed little hydrolytic activity toward TNP in aqueous DMF.