The first alternating MnII–MnIII 1D chain: structure, magnetic properties and catalytic oxidase activities

Abstract

An unprecedented one-dimensional mixed-valence chain, [{Mn^III(L)₂}{Mn^II(bpy)₂}(ClO₄)(H₂O)_0.5]_∞ (H₂L = N-salicylidene-L-alanine and bpy = 2,2′-bipyridine), has been synthesized. The complex has been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis, and variable-temperature magnetic measurements. The structural analysis reveals that the [Mn(bpy)₂]²⁺ unit is linked to the pendent carboxylate arm of the [Mn^III(L)₂]⁻ unit to produce a unique syn–anti carboxylate bridged 1D coordination polymer. Variable-temperature (2–300 K) magnetic susceptibility measurements show the presence of antiferromagnetic interaction between the Mn^III and Mn^II centres with J = −0.98(2) cm⁻¹. Using 3,5-di-tert-butylcatechol (3,5-DTBC) and o-aminophenol (OAPH) as the substrates, the catecholase-like activity and phenoxazinone synthase-like activity of the complex have been studied; the turnover numbers (k_cat) for these oxidase reactions have been calculated to be 126.9 and 738.0 h⁻¹, respectively.