Functionalized Nitronyl Nitroxide Biradicals for the Construction of 3d–4f Heterometallic Compounds

Abstract

Functionalized nitronyl nitroxide biradical ligands incorporating pyridine groups hold Co and Ln ions together, creating biradical-based 3d-4f tetranuclear complexes [LnCo(hfac)(NITPhPybis)] [Ln = Gd (1), Tb (2), Dy (3), and Ho (4); NITPhPybis = 5-(4-pyridyl)-1,3-bis(1'-oxyl-3'-oxido-4',4',5',5'-tetramethyl-4,5-hydro-1 H-imidazol-2-yl)benzene; hfac = hexafluoroacetylacetonate]. These complexes have a centrosymmetric cyclic molecular structure in which two biradicals perform as tetradentate ligands to bind two Co and two Ln ions, resulting in a rare octaspin system. Direct-current (dc) magnetic susceptibility studies reveal that the strong antiferromagnetic Co-NO magnetic exchange dominates the present magnetic system, while magnetic coupling of Gd-ON is ferromagnetic. Analysis of the magnetic data of the Gd complex allows us to determine the magnetic parameters through the appropriate magnetic model. Alternating-current (ac) magnetic susceptibility investigations indicate that 2 displays frequency-dependent out-of-phase signals under a zero dc field, while ac magnetic susceptibilities of 3 show field-induced frequency dependence, which is a typical feature of slow relaxation of the magnetization. Complexes 1-4 represent the first nitronyl nitroxide biradical-based 3d-4f compounds.

Two-Dimensional Nitronyl Nitroxide–Cu Networks Based on Multi-Dentate Nitronyl Nitroxides: Structures and Magnetic Properties

“…Multi-dentate radicals bisNITPhPy [31] and NIT-3Py-5-4Py [53] were prepared according to the related literature. Elemental analyses of both 2D Cu complexes were implemented by means of Perkin-Elmer elemental analytical equipment.…”

“…The metal-radical heterospin strategy, in which metal ions link with stable organic radicals, is extremely fascinating for designing molecular magnetic materials [1][2][3][4][5][6]. Based on this kind of heterospin approach, 3d [7][8][9], 4f [10][11][12][13][14][15][16][17], and 3d-4f [18][19][20][21][22][23] compounds have been obtained so far by employing various organic radicals, such as N 2 3− [15,16], HAN 3− [24], TTF + [25], thiadiazoyl [14], and nitronyl nitroxide radical ligands [6,7,10,13,19,23,[26][27][28][29][30][31][32]. In particular, nitronyl nitroxide radicals are often used as building blocks to construct metal compounds with various topology structures due to the substituent groups of nitronyl nitroxides being able to effectively regulate the spatial arrangement of magnetic building blocks [33].…”

A series of Salen‐type homodinuclear lanthanide complexes and their slow magnetic relaxation in Dy2 and Ho2

“…For complexes 1 and 2 , at 300 K, the experimental χ M T values of 15.79 and 23.53 cm 3 K mol –1 are in good agreement with the theoretical values of two uncoupled Gd 3+ ions ( 8 S 7/2 , S = 7/2, L = 0, g = 2, C = 15.76 cm 3 K mol –1 ) and Tb 3+ ions ( 7 F 6 , S = 3, L = 3, g = 3/2, C = 23.64 cm 3 K mol −1 ), respectively. For complexes 3 and 4 , at room temperature, the experimental χ M T values are 27.30 and 27.92 cm 3 K mol –1 , which are slightly smaller than the expected values of two uncoupled Dy 3+ ions ( 6 H 15/2 , S = 5/2, L = 5, g = 4/3, C = 28.34 cm 3 K mol −1 ), and Ho 3+ ions ( 5 I 8 , S = 2, L = 6, g = 5/4, C = 28.14 cm 3 K mol −1 ), respectively . Upon cooling, the χ M T values of complexes 1–4 gradually decrease to 14.64, 21.73, 24.77, 25.32 cm 3 K mol –1 at 70 K. With further cooling, the χ M T values of complexes 1 – 4 are drastically reduced.…”

Tuning slow magnetic relaxation behaviour in a {Dy2}-based one-dimensional chain via crystal field perturbation

“…S9 and S10 †) maybe derive from their different coordination numbers and geometry congurations and symmetries of the central Dy(III) ion. The effective energy barrier (U eff ) and relaxation time (s 0 ) of 1 and 2 can be obtained by tting ln(c 00 /c 0 ) vs. 1/T data with the following equation: ln(c 00 /c 0 ) ¼ ln(us 0 ) + E a /(k B T), [33][34][35] and the excellent linear tting between ln(c 00 /c 0 ) and 1/T can be depicted at different frequencies, yield U eff z 16.44 K and 8.02 K, s 0 z 3.25 Â 10 À6 s and 5.6 Â 10 À5 s for 1 and 2, respectively. The different effective energy barrier and relaxation time for 1 and 2 are due to the different anisotropy of their Dy(III) ions from subtle crystal eld perturbation caused by the change of one chelated acetate in 1 by one NCS À ligand (Fig.…”