Copper(II) coordination compounds with ferulic acid

The first two molecular structures of the ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid, C10H10O4) coordination compounds are presented, namely, [Cu2(C10H9O4)4(CH3CN)2] 1 and [Cu2(C10H9O4)4(C6H6N2O)2]·4CH3CN (C6H6N2O = nicotinamide) 2. Both compounds were synthesised from the starting mixture of Cu2O and CuCl upon copper oxidation in the acetonitrile solution. The single-crystal X-ray diffraction analysis of 1 and 2 reveals the binuclear structure of the ‘paddle–wheel’ type for both complexes. 1 and 2 are unstable outside mother liquid due to loosely bound acetonitrile molecules. The final products of decomposition are [Cu2(C10H9O4)4] 1a and [Cu2(C10H9O4)4(C6H6N2O)2] 2a, which were characterized by several physico-chemical methods. The triplet X-band EPR spectra of 1a and 2a, showing signals BZ1 ∼ 15 mT, B⊥2 ∼ 460 mT and BZ2 ∼ 580 mT, are in agreement with the expected data for the binuclear tetracarboxylate units, found in the structures of the parent complexes 1 and 2. Together with the room temperature magnetic susceptibility data, μeff/B.M. 1.40 (1a), 1.48 (2a), the EPR spectra analysis confirm the antiferromagnetic interaction in 1a and 2a. This is suggesting preservation and stability of the paddle–wheel structures in 1a and 2a.

Graphical abstractThe first two molecular structures of the ferulic acid coordination compounds in [Cu2(C10H9O4)4(CH3CN)2] 1 and [Cu2(C10H9O4)4(C6H6N2O)2]·4CH3CN (C6H6N2O = nicotinamide) 2 are presented. Both compounds were synthesised from the starting copper(I) upon copper oxidation in the acetonitrile solution. They are unstable outside mother liquid giving final [Cu2(C10H9O4)4] 1a and [Cu2(C10H9O4)4(C6H6N2O)2] 2a. The triplet S = 1 EPR spectra and μeff ∼ 1.45 B.M. confirm the antiferromagnetic interaction in the final products, and consequently a preservation and stability of the paddle–wheel structures in 1a and 2a by ‘oxidative’ copper(II) cations and ‘antioxidative’ ferulic acid anions.Figure optionsDownload full-size imageDownload as PowerPoint slide