X-ray Magnetic Circular Dichroism (XMCD) Study of a Methoxide-Bridged DyIII-CrIII Cluster Obtained by Fluoride Abstraction from cis-[(CrIIIF2(phen)2]+

Jan Dreiser, Kasper Steen Pedersen, Torben Birk, Magnus Schau-Magnussen, Cinthia Piamonteze, Stefano Rusponi, Thomas Weyhermueller, Harald Brune, Frithjof Nolting, Jesper Bendix

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Abstract

An isostructural series of dinuclear chromium(III)-lanthanide(III) clusters is formed by fluoride abstraction of cis-[CrF2(phen)2]+ by Ln3+ resulting in LnF3 and methoxide-bridged Cr-Ln clusters (Ln = Nd (1), Tb (2), Dy (3)) of formula [CrIII(phen)2(μ-MeO)2Ln(NO3)4xMeOH (x = 2-2.73). In contrast to fluoride, methoxide bridges in a nonlinear fashion, which facilitates chelation. For 3, X-ray magnetic circular dichroism (XMCD) provides element-specific magnetization curves that are compared to cluster magnetization and susceptibility data acquired by SQUID magnetometry. The combination of XMCD and SQUID is able to resolve very small magnetic coupling values and reveals a weak CrIII-DyIII coupling of j = -0.04(3) cm-1. The DyIII ion has a ground-state Kramers doublet of mJ = +/- 13/2, and the first excited doublet is found to be mj = +/- 11/2 at an energy of delta = 57(21) cm-1. The CrIII ion exhibits a uniaxial anisotropy of DCr = 1.7(1.0) cm-1. Further, we observe that a weak anisotropic coupling of dipolar origin is sufficient to model the data, suggesting that methoxide bridges do not play a significant role in the magnetic coupling for the present systems.
Original languageEnglish
JournalJournal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
Volume116
Issue number30
Pages (from-to)7842-7847
ISSN1089-5639
DOIs
Publication statusPublished - 2012
Externally publishedYes

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