Synthesis, structure, magnetism, and hydrolase and catecholase activity of a new trinuclear copper(II) complex

Abstract In this paper we report the synthesis of the new multidentate N,O-donor ligand H 3 L_2pyald = ( N , N ′-bis-(2-pyridylmethyl)-(2-hydroxy-3-carbonyl-5-methylbenzyl)-1,3-propanediamine-2-ol) and its first trinuclear copper(II) complex, [Cu 3 (L_2pyald)( μ -OAc)](ClO 4 ) 2 ( 1 ). The structure of 1 was determined by X-ray crystallography and variable-temperature magnetic data in the temperature range of 4–300 K indicate weak antiferromagnetism ( J 1,2  ≅ −1.0 cm −1 ) between the Cu(1) and Cu(2) centers bridged by the μ -alkoxo and μ -acetate groups and weak ferromagnetic coupling ( J 1,3  =  J 2,3  ≅ + 4.0 cm −1 ) involving the {Cu(1)( μ -phenoxo)Cu(3)} and {Cu(2)( μ -phenoxo)Cu(3)} structural units. Complex 1 shows significant catalytic activity towards the hydrolysis of the model substrate bis(2,4-dinitrophenyl)phosphate (2,4-BDNPP) as well as catechol oxidase activity since it efficiently catalyzes the oxidation of 3,5-di- tert -butylcatechol to 3,5-di- tert -butyl- o -benzoquinone by dioxygen. A comparison of the catalytic efficiency of 1 with its dinuclear parent complex [Cu 2 (H 2 bbppnol)( μ -OAc)] 2+ (H 3 bbppnol =  N , N ′, N , N ′-bis[(2-hydroxybenzyl)(2-methylpyridyl)]-1,3-propanediamine-2-ol) reveals that the hydrolase efficiency ( k cat / K M ) is 12 times higher for 1 , while the catecholase efficiencies of these two compounds are similar.