Issue 21, 2019

Mechanism of magnetisation relaxation in {M III2Dy III2} (M = Cr, Mn, Fe, Al) “Butterfly” complexes: how important are the transition metal ions here?

Abstract

We describe the synthesis, characterisation and magnetic studies of four tetranuclear, isostructural “butterfly” heterometallic complexes: [MIII2LnIII23-OH)2(p-Me-PhCO2)6(L)2] (H2L = 2,2′-((pyridin-2-ylmethyl)azanediyl)bis(ethan-1-ol), M = Cr, Ln = Dy (1), Y (2), M = Mn, Ln = Dy (3), Y (4)), which extend our previous study on the analogous 5 {Fe2Dy2}, 6 {Fe2Y2} and 7 {Al2Dy2} compounds. We also present data on the yttrium diluted 7 {Al2Dy2}: 8 {Al2Dy0.18Y1.82}. Compounds dc and ac magnetic susceptibility data reveal single-molecule magnet (SMM) behaviour for complex 3 {Mn2Dy2}, in the absence of an external magnetic field, with an anisotropy barrier Ueff of 19.2 K, while complex 1 {Cr2Dy2}, shows no ac signals even under applied dc field, indicating absence of SMM behaviour. The diluted sample 8 {Al2Dy0.18Y1.82} shows field induced SMM behaviour with an anisotropy barrier Ueff of 69.3 K. Furthermore, the theoretical magnetic properties of [MIII2LnIII23-OH)2(p-Me-PhCO2)6(L)2] (M = Cr, 1 or Mn, 3) and their isostructural complexes: [MIII2DyIII23-OH)2(p-Me-PhCO2)6(L)2] (M = Fe, 5 or Al, 7) are discussed and compared. To understand the experimental observations for this family, DFT and ab initio CASSCF + RASSI-SO calculations were performed. The experimental and theoretical calculations suggest that altering the 3dIII ions can affect the single-ion properties and the nature and the magnitude of the 3dIII–3dIII, 3dIII–DyIII and DyIII–DyIII magnetic coupling, thus quenching the quantum tunneling of magnetisation (QTM) significantly, thereby improving the SMM properties within this motif. This is the first systematic study looking at variation and therefore role of trivalent transition metal ions, as well as the diamgnetic AlIII ion, on slow relaxation of magnetisation within a series of isostructural 3d–4f butterfly compounds.

Graphical abstract: Mechanism of magnetisation relaxation in {MIII2DyIII2} (M = Cr, Mn, Fe, Al) “Butterfly” complexes: how important are the transition metal ions here?

Supplementary files

Article information

Article type
Edge Article
Submitted
30 Nov 2018
Accepted
04 Apr 2019
First published
16 Apr 2019
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2019,10, 5528-5538

Mechanism of magnetisation relaxation in {MIII2DyIII2} (M = Cr, Mn, Fe, Al) “Butterfly” complexes: how important are the transition metal ions here?

Y. Peng, M. K. Singh, V. Mereacre, C. E. Anson, G. Rajaraman and A. K. Powell, Chem. Sci., 2019, 10, 5528 DOI: 10.1039/C8SC05362F

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