Single‐Ion Magnetism in a Luminescent Er³⁺ β‐Diketonato Complex with Multiple Relaxation Mechanisms

Abstract

In the crystal structure of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)mono(bathophenanthroline)erbium(III), C 57 H 73 -ErN 2 O 6 , the Er 3+ ion is in an antiprismatic environment, surrounded by two N atoms and six O atoms. The β-diketonato ligands show structural disorder. The ac susceptibility studies conducted at frequencies from 33 to 9995 Hz and at temperatures from 1.7 to 10 K revealed that the application of a static [a]

Field-induced single-ion magnetic behaviour in a highly luminescent Er3+ complex

“…This fact can be explained by the magnetic anisotropy of the compound, which is further confirmed by the non-superimposition of the M vs. B/T curves at lower temperatures (Figure 6b). Clear evidence for slow relaxation of the magnetisation is also given by measuring the AC susceptibility components, ' and ", at fixed frequencies in the low temperature range, 1.6-10 K. In a similar fashion to what was observed in other Er 3+ complexes classified as SIMs [17], under zero DC field the in-phase component, ', was found to be almost frequency independent, while the out-of-phase component, '', presents a small frequency dependence with a local maximum shifting to higher temperatures as frequency increases (Figure 7a). The application of a small static magnetic field of 500 Oe drastically changes the relaxation dynamics with the occurrence of peaks in both ' and '' components, that which show strong frequency and temperature dependence (Figure 7b and Figure 7c).…”

“…When plotted with the correspondent inverse of temperature, these single relaxation times  have an activated temperature dependency (Figure 8b) that follows an Arrhenius law, (T) = 0·exp(Eeff/kBT) in the higher temperature range (dashed line), with a pre-exponential factor 0 = 1.73×10 -8 s and an effective relaxation barrier of Eeff = 26.8 K (18.6 cm -1 ) which are within the range of most of other well-known d- [33,34] and f-element SMMs [17,18,35]. In the lower temperature range, a clear deviation from this activated regime is noticed, likely due to the approaching of a quantum tunnelling regime expected to occur at lower temperatures.…”

“…At 1.6 K a clear opening of the magnetic hysteresis is observed as one moves away from zero field, revealing strong field dependence. The absence of coercivity can be due to an efficient quantum tunnelling of the magnetization occurring at zero field, probably caused by low symmetry components of the crystal field, as it was already observed in other mononuclear lanthanide [17,18,28] and uranium [29,30] compounds with SMM behaviour. At this temperature and up to 10 T, magnetization approaches a value of 7.9 μB, still far from the expected saturation value for a free Er 3+ ion.…”

“…There are some examples of lanthanide complexes where both luminescent emission and slow relaxation of the magnetization occur [11][12][13][14][15][16][17][18]. This configures these materials as multifunctional materials.…”

Highly luminescent pure-red-emitting fluorinated β-diketonate europium(III) complex for full solution-processed OLEDs

“…Eu-O and Eu-N distances and angles ( Table 2) are within normal ranges [26] and correspond to a distorted square antiprismatic geometry around Eu 3 þ . This type of geometry occurs frequently for trivalent lanthanide ions coordinated with diketonates [27][28][29][30][31][32][33][34]. The angle between the top and bottom square faces of the antiprism is 2.75(5)1.…”