Probing optical and magnetic properties via subtle stereoelectronic effects in mononuclear Dy^III-complexes

Abstract

Tapping into the secondary coordination environment of mononuclear DyIII-complexes leads to drastic changes in luminescence and magnetism. Visualization of effects induced by stereoelectronics on the opto-magnetic properties was achieved through...

Modulating Two Pairs of Chiral DyIII Enantiomers by Distinct β-Diketone Ligands to Show Giant Differences in Single-Ion Magnet Performance and Nonlinear Optical Response

“…It is well recognized that the strong ligand field (LF) with large electron density in the axial position and the weak LF with small electron density in the equatorial position are helpful for the enhancement of the ground-state magnetic anisotropy. ,, Compared with R -1-Dy , there are two strong electron-withdrawing −CF 3 groups in the axial position in R -2-Dy , thus leading to a weaker axial LF and a smaller magnetic anisotropy in R -2-Dy , which is directly associated with the observation of a smaller U eff value for R -2-Dy . In addition, recent research showed that when a C–H moiety in the pyridine ring of an equatorial ligand PyAm (PyAm = 2-amidinopyridine) is replaced by a nitrogen atom, the resulting mononuclear eight-coordinated Dy III -β-diketonate complex [Dy­(acac) 3 (PmAm)] (acac – = acetylacetonate, PmAm = 2-amidinopyrimidine) presents significantly enhanced SIM performance compared to [Dy­(acac) 3 (PyAm)], which can be attributed to the weakening of the equatorial ligand field due to the electron–acceptor feature of the N-containing aromatic heterocyclic ligand . This phenomenon was also observed in other mononuclear eight-coordinated Dy III -β-diketonate SIMs, for example, [Dy­(acac) 3 (phen)] ( U eff = 64 K, phen = 1,10-phenanthroline) vs [Dy­(acac) 3 (dpq)] ( U eff = 136 K, dpq = dipyrazine­[2,3- f :2′,3′- h ]­quinoxaline .…”

“…19,80,81 Compared with R-1-Dy, there are two strong electron-withdrawing −CF 3 groups in the axial position in R-2-Dy, thus leading to a weaker axial LF and a smaller magnetic anisotropy in R-2-Dy, which is directly associated with the observation of a smaller U eff value for R-2-Dy. In addition, recent research showed that when a C−H moiety in the pyridine ring of an equatorial ligand PyAm (PyAm = 2amidinopyridine) is replaced by a nitrogen atom, the resulting mononuclear eight-coordinated Dy III -β-diketonate complex [Dy(acac) 3 (PmAm)] (acac − = acetylacetonate, PmAm = 2amidinopyrimidine) presents significantly enhanced SIM performance compared to [Dy(acac) 3 (PyAm)], 82 which can be attributed to the weakening of the equatorial ligand field due to the electron−acceptor feature of the N-containing aromatic heterocyclic ligand. 83 S10.…”

Luminescence thermometry in a Dy4 single molecule magnet

“…It is worth mentioning that there are few examples of Dy III -based SMM optical thermometers in the literature, and most of these examples based their luminescent thermometric features on solely Dy III emissions. 7 b ,11,12,15,17 Our system accesses the thermometric characteristics involving the ligand ascribed to the triplet emission in combination with Dy III emission and, to the best of our knowledge, there is only one example in the literature that shares this feature. 7 b As can be seen in Table 1, this related compound is a dinuclear dysprosium complex, and, although the number of homodi- or polynuclear dysprosium SMMs is very low, the data may suggest that this phenomenon is more favoured in SMMs with more than one Dy III ion than in SIMs of the same metal.…”

“…One way to overcome this impasse is to build microdevices with materials capable of also acting as in situ thermometers. In this sense, there are some very recent publications that try to provide solutions for the measurement of temperature in molecular magnets, making use of luminescent thermometry, [7][8][9][10][11][12][13][14][15][16][17] and some of the achievements were summarised by Murugesu and colaborators. 18 Among these works, most studies have been carried out with homodinuclear compounds of Dy III , 7b Tb III , 7c or Yb III .…”

“…Thus, some of us have published the first mononuclear Yb III compound with slow relaxation of magnetization and luminescent thermometry, 10 which currently accompanies other two complexes of the same metal. 13 Additionally, some other mononuclear dysprosium compounds have been published, 11,12,17 as well as a mononuclear Nd III complex, 8 which combine their character as single ion magnets (SIMs) and their luminescent thermometric capacity. Accordingly, the field of the SMMs as luminescent thermometers is still in its beginnings.…”