Lanthanide–Nitronyl Nitroxide Chains Derived from Multidentate Nitronyl Nitroxides

Abstract

Unprecedented lanthanide (Ln)-radical loop-chain coordination polymers were achieved using multidentate pyridyl- or triazole- substituted nitronyl nitroxide ligands. Their magnetic units consist of ferromagnetic [LnRadical] moieties, leading for the dysprosium(III) derivatives to slow relaxation of magnetization, which was found to be dependent on the heterocyclic ligands.

Enhancing Magnetic Behaviors of Dysprosium Single-Molecule Magnets from Crystal Field Perturbation by Deprotonating Schiff-Base Ligand

“…While no signals were observed, which might be ascribed to quantum tunneling of the magnetization (QTM), , a 1000 Oe dc field was utilized to suppress the QTM effect, χ′ and χ″ signals vs temperature plots (Figure S7 and S9) and frequency dependencies plots (Figures and ) in both complexes can be observed, suggesting the typical slow magnetic relaxation behaviors of SMMs. As for 1 , the effective energy barrier U eff of 20.63 K and relaxation times τ 0 of 2.69 × 10 –7 s were obtained by fitting ln τ vs 1/ T data (Figure c, relaxation time τ was derived from the frequency-dependence plots) based on eq , which considers only Orbach and QTM processes with τ QTM = 8.1 × e –4 s. , Semicircular Cole–Cole ( χ″ vs χ′ ) plots in the range of 2.0–4.0 K (Figure d) was also fitted by generalized Debye model to get α = 0.25–0.33, implying a narrow distribution of relaxation times. …”

“…Two series of relaxation times and α parameters derived from frequency-dependence measurements were fitted separately in the sum of two modified Debye functions eq . For the FR phase in Figure c, fitting ln τ vs 1/ T plots with eq considering Orbach and QTM processes , yields U eff = 28.49 K and τ 0 = 6.22 × 10 –7 s with parameter τ QTM = 0.0065 s. The α values for the FR phase are in the range of 0.08–0.38. Meanwhile for the SR phase, fitting ln τ vs 1/ T plots with eq obtained U eff = 57.52 K and τ 0 = 1.53 × 10 –12 s with τ QTM = 0.0048 s. The α values for the SR phase were afforded in the range of 0.15–0.65, implying a wide distribution of relaxation times.…”

Regulating Spin Dynamics of Nitronyl Nitroxide Biradical Lanthanide Complexes through Introducing Different Transition Metals

“…The obtained positive J 1 reveals ferromagnetic interaction in the Gd III -nitroxide moiety, which is consistent with previous reports in the literature. [22,23] Notably, J 2 is a combination of two kinds of magnetic couplings, namely, the antiferromagnetic exchange between two NO units via Gd Ш ion and the ferromagnetic interaction between two NIT units through m-phenylene ring according to spin polarization (Scheme S1). [24] The negative value of J 2 reflects that the former plays a major role.…”

Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

“…In 2018, K. R. Dunbar et al, reported the first metallacycle [Dy 3 (hfac) 6 (bptz −• ) 3 ](bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; hfac = hexafluoroacetylacetonate) exhibiting temperature-dependent out-of-phase (χ") signals in the high-frequency range [15]. Noticeable, most of radical-Ln based molecular nanomagnets are constructed using mono-radicals [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], and the employments of biradicals are less common [23][24][25][26][27][28]. Nitronyl nitroxide biradical-Ln approach, one hand, can result in interesting spin topology in which the unique magnetic behavior could be observed.…”