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Substituent effect of phenylacetic acid coligands perturbed structures and magnetic properties observed in two triple-bridged azido-Cu(II) chain compounds with ferromagnetic ordering and slow magnetic relaxation

Abstract

Based on two fluoro-substituted phenylacetate isomers, o-fluorophenylacetic acid (o-Hfpa) and p-fluorophenylacetic acid (p-Hfpa), two new Cu(II)-azido compounds, [Cu(o-fpa)(N3)(C2H5OH)]n (1) and [Cu(p-fpa)(N3)(C2H5OH)]n (2), have been prepared, and structurally and magnetically characterized. Single-crystal structure analyses indicate that compounds 1 and 2 consist of 1D chain-like coordination networks in which adjacent copper cations are linked by the alternating triple-bridges of μ-1,1-azido, syn,syn-carboxylate and μ2-ethanol. For two title compounds, the diverse charge distributions on the carboxyl groups caused by distinct substituent effects of two phenylacetate coligands lead to the different structural parameters of intrachain Cu-Cu distances (3.218 Å for 1 and 3.168 Å for 2) and Cu-N-Cu angles (106.82° for 1 and 104.81° for 2), further resulting in the disparity of magnetic behaviors. The dominant ferromagnetic couplings between neighbouring Cu(II) ions in two compounds (J = 87.08 cm-1 for 1, J = 66.05 cm-1 for 2) is due to the counter-complementarity of the multiple superexchange pathways, contributing to inspiring plots of ferromagnetic order (Tc = 11.0 K for 1, 9.5 K for 2) and slow magnetic relaxation that are rarely observed in most of the reported azido-Cu(II) architectures. Heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in compounds 1 and 2. Magneto-structural relationships of 1 and 2 are investigated as well. Moreover, DFT calculations (using different methods and basis sets) have been performed on both compounds to provide the qualitatively and quantitatively theoretical explanation of the magnetic behaviors.

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Publication details

The article was received on 13 Apr 2017, accepted on 18 May 2017 and first published on 18 May 2017


Article type: Paper
DOI: 10.1039/C7DT01338H
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Substituent effect of phenylacetic acid coligands perturbed structures and magnetic properties observed in two triple-bridged azido-Cu(II) chain compounds with ferromagnetic ordering and slow magnetic relaxation

    X. Liu, X. Ma, P. Cen, Y. Wu, C. Zhang, Q. Shi, W. Song, G. Xie and S. Chen, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01338H

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