Issue 22, 2016

Syntheses, structures, and magnetic properties of three new chain compounds based on a pentagonal bipyramidal Co(ii) building block

Abstract

Starting from the pentagonal bipyramidal single-ion magnet [Co(tdmmb)(H2O)2][BF4]2 and a series of linear bridging ligands of different lengths, three new cobalt(II) one-dimensional (1D) coordination polymers, [Co(tdmmb)(pyz)][BF4]2·CH3CN·H2O (1), [Co(tdmmb)(apy)][BF4]2·2CH3CN (2), and [Co(tdmmb)(bpe)][BF4]2·3CH3CN (3) (tdmmb = 1,3,10,12-tetramethyl-1,2,11,12-tetra-aza[3](2,6)pyridino[3](2,9)-1,10-phenanthrolinophan-2,10-diene) (pyz = pyrazine) (apy = 4-aminopyridine) (bpe = 1,2-di(4-pyridyl)ethane)), have been synthesized and characterized structurally and magnetically. Symmetric ligands pyz and bpe result in the nearly linear chains in 1 and 3, while the asymmetric ligand apy leads to the zig-zag chain in 2. As the length of the ligands increases, the intrachain Co⋯Co distance also increases, i.e. 7.56, 7.70, and 13.85 Å for 1–3, respectively. Magnetic investigation revealed the gradual decrease in the magnetic interactions between the Co2+ ions from 1 to 3, along with the increase in the intrachain Co–Co distances. Due to the existence of the weak antiferromagnetic (AF) interaction, the SIM behavior of the starting material is surpressed in compounds 1 and 2, and they show a simple paramagnetic behavior. While for 3, field-induced slow magnetic relaxation was observed at a low temperature with an energy barrier of Ueff = 19 K. This observation suggests that the magnetic interaction between the Co2+ centers in 3 is negligible, consistent with the very long Co–Co distance in 3. These 1D compounds are rare chain compounds composed of metal centers with a nearly D5h symmetry. Notably, compound 3 is the second example of a 1D Co(II) chain compound displaying a SIM behaviour. These studies illustrated that the magnetic interaction between the SIMs can be used to tune slow magnetic relaxation.

Graphical abstract: Syntheses, structures, and magnetic properties of three new chain compounds based on a pentagonal bipyramidal Co(ii) building block

Supplementary files

Article information

Article type
Paper
Submitted
31 dec 2015
Accepted
03 feb 2016
First published
03 feb 2016

CrystEngComm, 2016,18, 4150-4157

Syntheses, structures, and magnetic properties of three new chain compounds based on a pentagonal bipyramidal Co(II) building block

D. Shao, L. Shi, S. Zhang, X. Zhao, D. Wu, X. Wei and X. Wang, CrystEngComm, 2016, 18, 4150 DOI: 10.1039/C5CE02594J

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