Issue 6, 2015

New tricopper(ii) cores self-assembled from aminoalcohol biobuffers and homophthalic acid: synthesis, structural and topological features, magnetic properties and mild catalytic oxidation of cyclic and linear C5–C8 alkanes

Abstract

Two new crystalline materials [Cu32-H3bis-tris)22-Hhpa)2]·H2O (1) and [Cu32-H2tea)22-hpa)(μ3-hpa)]n (2) bearing distinct tricopper(II) cores were easily generated by the aqueous medium self-assembly method from copper(II) nitrate, bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (H5bis-tris) or triethanolamine (H3tea) aminoalcohol biobuffers and homophthalic acid (H2hpa). The obtained products were characterised by IR, UV-vis and EPR spectroscopy, ESI-MS(±), thermogravimetric, elemental and single crystal X-ray diffraction analysis. Apart from possessing different dimensionality, the crystal structures of the discrete 0D trimer 1 and the zigzag 1D coordination polymer 2 show distinct symmetric [Cu3(μ-O)4(μ-COO)2] and asymmetric [Cu3(μ-O)3(μ-COO)2] tricopper(II) cores, respectively. An intense pattern of intermolecular O–H⋯O hydrogen bonds provides a 0D → 3D (1) or 1D → 2D (2) extension of the structures into intricate topologically unique H-bonded nets. After additional simplification, these were classified as a uninodal 6-connected 3D framework with the snk topology in 1 and a binodal 3,5-connected 2D layer with the 3,5L50 topology in 2. Variable-temperature magnetic susceptibility studies indicate a predominant ferromagnetic coupling [J = 39.1(1) and 29.5(1) cm−1 for 1 and 2, respectively] within the mixed-bridged tricopper(II) cores. Both compounds 1 and 2 were also applied as rather efficient bio-inspired pre-catalysts for the mild homogeneous oxidation, by aqueous H2O2 at 50 °C in acidic MeCN–H2O medium, of cyclic (cyclopentane, cyclohexane, cycloheptane and cyclooctane) and linear (n-pentane, n-hexane, n-heptane and n-octane) alkanes to the corresponding alcohols and ketones with overall yields up to 26% based on the alkane. The effects of different reaction parameters (type of pre-catalyst and acid promoter, reaction time and substrate scope) and various selectivity features were investigated and discussed, supporting a free-radical mechanism in the present alkane oxidations.

Graphical abstract: New tricopper(ii) cores self-assembled from aminoalcohol biobuffers and homophthalic acid: synthesis, structural and topological features, magnetic properties and mild catalytic oxidation of cyclic and linear C5–C8 alkanes

Supplementary files

Article information

Article type
Research Article
Submitted
04 дек 2014
Accepted
27 мар 2015
First published
30 мар 2015

Inorg. Chem. Front., 2015,2, 525-537

New tricopper(II) cores self-assembled from aminoalcohol biobuffers and homophthalic acid: synthesis, structural and topological features, magnetic properties and mild catalytic oxidation of cyclic and linear C5–C8 alkanes

S. S. P. Dias, M. V. Kirillova, V. André, J. Kłak and A. M. Kirillov, Inorg. Chem. Front., 2015, 2, 525 DOI: 10.1039/C4QI00220B

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