Abstract
Three di-nuclear DyIII complexes [Dy2(H2L)2(tfa)]·Cl·3DMF (1), [Dy2(H2L)2(MeO)(SCN)]·MeOH (2) and [Dy2(H2L)2(MeOH)Cl]·Cl·2MeOH (3) were synthesized and structurally and magnetically characterized. The Dy1/Dy2 centers in these complexes are all nine-coordinate with spherical capped square antiprism (local C4v symmetry) environments. All complexes display single-molecule magnet (SMM) behavior under zero applied dc field with their properties dependent on the nature of the magnetic interactions between the DyIII ions. Ab initio calculations substantiate that all DyIII ions show a weakly axial crystal-field environment with the exception of one of the DyIII ions in complex 2. The ground Kramers doublets show modest amounts of quantum tunneling of magnetization that gets blocked by the interaction between the DyIII ions, leading to a thermally activated slow relaxation of magnetization. The interaction between the ions is ferromagnetic and mostly originates from the dipolar interaction. However, anti-ferromagnetic intermolecular interaction plays an important role and in the case of complex 2 it is sufficiently strong to mask the ferromagnetic intramolecular interaction.
Highlights
Single-molecule magnets (SMMs) are molecules with nanomagnetic functionality.[1,2,3,4,5] Unlike classical ferromagnetism, the magnetic behavior is characterized by slow relaxation of magnetization of individual molecules rather than the collective behavior of an ensemble of paramagnetic atoms in a magnetic domain
The donor and acceptor atoms of the hydrogen bonds that form the dimer pairs are all the oxygen atoms located in the equivalent position of the diethanolamine moiety from adjoining ligands
Cl− is bound to two O-donors that originated from a diethanolamine of one dimer and a guest MeOH molecule around it
Summary
Single-molecule magnets (SMMs) are molecules with nanomagnetic functionality.[1,2,3,4,5] Unlike classical ferromagnetism, the magnetic behavior is characterized by slow relaxation of magnetization of individual molecules rather than the collective behavior of an ensemble of paramagnetic atoms in a magnetic domain. The isothermal magnetization measured as a function of field measured at different temperatures for 1–3 does not superimpose completely, suggesting the possibility of a low-lying excited state arising from the exchange interaction.[66] No obvious magnetic hysteresis was observed above 1.9 K (Fig. S5†).
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