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From a Dy(III) Single Molecule Magnet (SMM) to a Ferromagnetic [Mn(II)Dy(III)Mn(II)] Trinuclear Complex

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journal contribution
posted on 20.02.2016, 11:34 by Asamanjoy Bhunia, Michael T. Gamer, Liviu Ungur, Liviu F. Chibotaru, Annie K. Powell, Yanhua Lan, Peter W. Roesky, Fabian Menges, Christoph Riehn, Gereon Niedner-Schatteburg
The Schiff base compound 2,2′-{[(2-aminoethyl)­imino]­bis­[2,1-ethanediyl-nitriloethylidyne]}­bis-2-hydroxy-benzoic acid (H4L) as a proligand was prepared in situ. This proligand has three potential coordination pockets which make it possible to accommodate from one to three metal ions allowing for the possible formation of mono-, di-, and trinuclear complexes. Reaction of in situ prepared H4L with Dy­(NO3)3·5H2O resulted in the formation of a mononuclear complex [Dy­(H3L)2]­(NO3)·(EtOH)·8­(H2O) (1), which shows SMM behavior. In contrast, reaction of in situ prepared H4L with Mn­(ClO4)2·6H2O and Dy­(NO3)3·5H2O in the presence of a base resulted in a trinuclear mixed 3d–4f complex (NHEt3)2[Dy­{Mn­(L)}2]­(ClO4)·2­(H2O) (2). At low temperatures, compound 2 is a weak ferromagnet. Thus, the SMM behavior of compound 1 can be switched off by incorporating two Mn­(II) ions in close proximity either side of the Dy­(III). This quenching behavior is ascribed to the presence of the weak ferromagnetic interactions between the Mn­(II) and Dy­(III) ions, which at T > 2 K act as a fluctuating field causing the reversal of magnetization on the dysprosium ion. Mass spectrometric ion signals related to compounds 1 and 2 were both detected in positive and negative ion modes via electrospray ionization mass spectrometry. Hydrogen/deuterium exchange (HDX) reactions with ND3 were performed in a FT-ICR Penning-trap mass spectrometer.