Pentanuclear MII–MnII (M = Ni and Cu) complexes of N2O2 donor ligands with a variation of carboxylate anions: syntheses, structures, magnetic properties and catecholase-like activities. (26th August 2022)

• Record Type: Journal Article
• Authors: Ganguly, Sayantan; Bhunia, Pradip; Mayans, Júlia; Ghosh, Ashutosh
• Is Part Of: New journal of chemistry. Volume 46:Number 36(2022)
• Page Start: 17260
• Page End: 17271
• Publication Date: 2022-08-26
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/d2nj02215j
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : One NiII2MnII3 and two CuII2MnII3 complexes have been synthesized using N2 O2 donor ligands. The former complex exhibits spin crossover at 2 K temperature. All the complexes exhibit catecholase-like activities. Abstract : One new heterometallic nickel(ii )–manganese(ii ) complex [(NiL 1 )2 Mn3 (C6 H5 CO2 )6 ] (1 ) and two new copper(ii )–manganese(ii ) complexes[(CuL 1 )2 Mn3 ( m -(NO2 )C6 H4 CO2 )6 ] (2 ) and [{CuL 2 (H2 O)}2 Mn3 ( m -(NO2 )C6 H4 CO2 )6 ] (3 ) have been synthesized and structurally characterized using [NiL 1 ]/[CuL 1 ]/[CuL 2 ] as a metalloligand (where H2 L 1 = N, N ′-bis(2-hydroxynaphthyl-methylidene)-1, 3-propanediamine, H2 L 2 = N, N ′-bis(methyl-2-hydroxynaphthyl-methylidene)-1, 3-propanediamine). Crystal structure analyses show that in all three pentanuclear complexes two [NiL 1 ]/[CuL 1 ]/[CuL 2 ] units are coordinated to the terminal Mn II centres of a linear trinuclear MnII3 core i.e. [Mn3 (C6 H5 CO2 )6 ] (for 1 )/[Mn3 ( m -(NO2 )C6 H4 CO2 )6 ] (for 2 and 3 ) through bis-phenoxido bridges. All three complexes (1–3 ) mimic catecholase-like activity in the oxidation of 3, 5-di- tert -butyl catechol (3, 5-DTBC) as the substrate with turnover numbers ( k cat ) of 734, 450 and 358 h −1, respectively. A plausible mechanism of this catalytic oxidase reaction is proposed on the basis of mass spectral evidence. The temperature-dependent (2–300 K) dc molar magnetic susceptibility measurements of 1 reveal that the Mn–Mn centres of the [Mn3 (C6 H5 CO2 )6 ] unit are antiferromagnetically coupled with an exchange coupling constant ( J ) value of −0.70 cm −1 . Isothermal magnetization experiments of 1 at 2 K suggest a change in the ground spin state from S = 5/2 to S = 7/2 upon increasing the magnetic field at 5 T because of the presence of low-lying excited spin states due to the low value of the coupling constant ( J ). Complexes 2 and 3 have similar structures and thus magnetic characterization of 2 has only been performed. It shows antiferromagnetic exchange interactions between the Cu–Mn centres ( J 1 = −28.5 cm −1 ) and also between the metal centres in the MnII3 core unit ( J 2 = −2.11 cm −1 ).