Multifunctional properties existing in Ln–nitronyl nitroxide single-chain magnets

Li, Hongdao; Liu, Xi; Jing, Pei; Tang, Jianke; Wang, Qi; Yang, Hai; Zhai, Lu; Niu, Yulan; Ding, Lifeng; Song, Zhenjun

doi:10.1039/d0tc04266h

Cited by 22 publications

(12 citation statements)

References 44 publications

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“…Molecular magnetic materials especially single-molecule magnets (SMMs) exhibit slow magnetic relaxation behavior at low temperatures. − With the continuous improvement of spin-reversal barrier and blocking temperature, SMMs have been expected to show increasing competitiveness in the fields of high-density information storage, quantum processing, and spintronics . It is an effective way to modulate the SMMs’ performance by the combination of lanthanide (Ln) centers and radical ligands. − The paramagnetic radicals can penetrate into the deeply buried 4f orbitals of Ln ions, which may facilitate the direct exchange coupling between Ln ions and radical spins. − However, this strategy usually requires burdensome synthetic methods (such as redox reactions triggered by chemical reagents) and is carried out under anhydrous and/or anaerobic conditions. Seeking a convenient way to control the magnetic behavior is crucial for the design of molecular devices.…”

Section: Introductionmentioning

confidence: 99%

Magnetic and Luminescent Dual Responses of Photochromic Hexaazamacrocyclic Lanthanide Complexes

et al. 2023

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Herein, hexaazamacrocyclic ligand LN6 was employed to construct a series of photochromic rare-earth complexes, [Ln(LN6)(NO3)2](BPh4) [1-Ln, Ln = Dy, Tb, Eu, Gd, Y; LN6 = (3E,5E,10E,12E)-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane-3,5,10,12-tetraene]. The behavior of photogenerated radicals of hexaazamacrocyclic ligands was revealed for the first time. Upon 365 nm light irradiation, complexes 1-Ln exhibit photochromic behavior induced by photogenerated radicals according to EPR and UV–vis analyses. Static and dynamic magnetic studies of 1-Dy and irradiated product 1-Dy* indicate weak ferromagnetic interactions among DyIII ions and photogenerated LN6 radicals, as well as slow magnetization relaxation behavior under a 2 kOe applied field. Further fitting analyses show that the magnetization relaxation in 1-Dy* is markedly different from 1-Dy. Time-dependent fluorescence measurements reveal the characteristic luminescence quenching dynamics of lanthanide in the photochromic process. Especially for irradiated product 1-Eu*, the luminescence is almost completely quenched within 5 min with a quenching efficiency of 98.4%. The results reported here provide a prospect for the design of radical-induced photochromic lanthanide single-molecule magnets and will promote the further development of multiresponsive photomagnetic materials.

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Section: Introductionmentioning

confidence: 99%

Magnetic and Luminescent Dual Responses of Photochromic Hexaazamacrocyclic Lanthanide Complexes

et al. 2023

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“…Nitronyl nitroxides are thermodynamically stable due to their electron-delocalized structure. Therefore, it is widely used as a spin carrier in the design of molecular magnetic materials, ,, with the expected AF or ferromagnetic (FM) spin-exchange interaction. , In previous works, the primary strategy was to obtain higher spin organic magnetic materials based on molecular topology, , like π-conjugated rigid molecules, − metal ion coordination molecules, , and self-assembled molecules. − …”

Section: Introductionmentioning

confidence: 99%

Spirobifluorene Mediating the Spin–Spin Coupling of Nitronyl Nitroxide Diradicals

et al. 2023

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To investigate the mechanism of this spiro conjugation magnetic behavior, we designed and synthesized three diradicals�22′SBF-NN, 44′SBF-NN, and 27SBF-NN. They are bridged by spirobifluorene and nitronyl nitroxide (NN) diradicals as the spin centers. Notably, by SQUID and electron paramagnetic resonance (EPR) zero-field splitting data analyses, the 22′SBF-NN and 27SBF-NN diradicals exhibit intramolecular, distinctly antiferromagnetic (AF) coupling, with 2J (22′SBF-NN) /k B = −5.86 K and 2J (27SBF-NN) /k B = −24.6 K, respectively. The AF of 22′SBF-NN is opposite to that predicted by the spin density alternation rule based on Hund's rule. Diradical intramolecular conjugation coupling bridged by spiro-carbon conjugation is discussed, in which the 22′SBF-NN is smaller than that of 27SBF-NN, corresponding to the room-temperature EPR characterization. This spiro conjugation is weaker than the traditional planar conjugation and generally leads to a weaker spin−spin coupling in the helical biradical molecule. The EPR spectrum of the 44′SBF-NN diradical shows a deformed nine-line curve, indicating intramolecular exchange coupling. The density functional theory calculation gives a very weak coupling constant of 2J calc / k B = 0.06 K, with ferromagnetic (FM) interaction as the proof, which is consistent with the spin-polarized prediction. Further analysis of magnetic susceptibility χ m and VT-EPR data shows that there is indeed an extremely weak FM interaction in the 44′ position diradical. We find the bridge, which is a 44′ substituted SBF structure, blocks the conjugation and contains a larger twist in steric hindrance, which also hampers sufficient spin density delocalization, resulting in a much weaker spin coupling interaction. Combined with the analysis of molecular orbital calculation results, the anomalous intramolecular AF coupling mechanism of 22′SBF-NN is further explained.

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Section: Introductionmentioning

confidence: 99%

“…9 In 2021, Li et al reported 1D chains [Ln(hfac) 3 (8-QNNIT)] n (Ln = Tb, Dy), which displayed SCM behaviors and optical or/and thermodynamics properties that coexist in the molecular unit. 10 Recently, investigations into SCMs have also focused on Cu-Ln-radical heterotrispin chains. 11 On the other hand, Ln-based complexes may be excellent candidates as fluorescent sensors for detecting toxic gases, small molecules, cations and anions due to the narrow and typical fluorescent emissions of some Ln(III) ions.…”

Section: Introductionmentioning

confidence: 99%

Slow magnetic relaxation and selective luminescence sensor of Ln-radical chain involving imidazole-substituted nitronyl nitroxide radical

et al. 2022

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Multifunctional properties existing in Ln–nitronyl nitroxide single-chain magnets

Abstract: Taking advantage of a nitronyl nitroxide radical ligand 8-QNNIT (1) (8-quinolyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) and the Ln(hfac)32H2O (LnIII = Tb 2 and Dy 3; hfac = hexafiuoroacetylacetonate), two Ln-radical one-dimensional chains [Ln(hfac)3(8-QNNIT)]n were...

Cited by 22 publications

References 44 publications

Magnetic and Luminescent Dual Responses of Photochromic Hexaazamacrocyclic Lanthanide Complexes

Magnetic and Luminescent Dual Responses of Photochromic Hexaazamacrocyclic Lanthanide Complexes

Spirobifluorene Mediating the Spin–Spin Coupling of Nitronyl Nitroxide Diradicals

Slow magnetic relaxation and selective luminescence sensor of Ln-radical chain involving imidazole-substituted nitronyl nitroxide radical

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