Abstract:We synthesized the dinuclear and mononuclear dysprosium(III) complexes [{Dy(Tp) 2 } 2 (Cl 2 An)]·2CH 2 Cl 2 (1) and [Co(Cp) 2 ][Dy(Tp) 2 (Cl 2 An)] (3), where Cl 2 An 2− and Tp − are the chloranilate and hydrotris(pyrazolyl)borate ligand, respectively. In addition, the magnitude of the magnetic coupling between the lanthanide centers through the Cl 2 An 2− bridge has been probed through the synthesis of [{Gd(Tp) 2 } 2 (Cl 2 An)]·2CH 2 Cl 2 (2), which is a gadolinium(III) analogue of 1. Complexes 1-3 were characterized by infrared (IR) spectroscopy, elemental analysis, single-crystal X-ray diffraction, and SQUID measurements. IR and single-crystal X-ray structural analyses confirm that the coordination environments of the lanthanide(III) centers in 1 and 3 are similar to each other; i.e., eight-coordinated metal centers, each occupied by an N 6 O 2 donor set from two Tp − ligands and one Cl 2 An 2− ligand. The coordination geometries of the lanthanide(III) centers in 1 and 2 are distorted triangular dodecahedral, while that in the mononuclear complex 3 is square antiprismatic, where the Cl 2 An 2− ligand takes the bi-separated delocalized form in 1 and 2, and the o-quinone form in 3. Alternating-current (AC) magnetic studies clearly reveal that both 1 and 3 exhibit field-induced slow relaxations of magnetization that occur via Raman and direct processes. Complexes 1 and 3 exhibit different spin relaxation behavior, which reflects the coordination geometry around each Dy III center and its nuclearity, as well as the molecular packing in the crystal lattice. Although the magnetic analysis of 2 revealed negligible magnetic coupling, Cl 2 An 2− bridges with small biases may form in the dinuclear complexes, which play roles in the spin relaxation dynamics through dipolar interactions.

A series of chloralilate-bridged dinuclear lanthanide complexes of formula [{Ln III (Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 , where Cl 2 An 2− and Tp − represent the chloranilate and hydrotris (pyrazolyl)borate ligands, respectively, and Ln = Gd (1), Tb (2), Ho (3), Er (4), and Yb (5) was synthesized. All five complexes were characterized by an elemental analysis, infrared spectroscopy, single crystal X-ray diffraction, and SQUID measurements. The complexes 1-5 in the series were all isostructural. A comparison of the temperature dependence of the dc magnetic susceptibility data of these complexes revealed clear differences depending on the lanthanide center. Ac magnetic susceptibility measurements revealed that none of the five complexes exhibited a slow magnetic relaxation under a zero applied dc field. On the other hand, the Kramers systems (complexes 4 and 5) clearly displayed a slow magnetic relaxation under applied dc fields, suggesting field-induced single-molecule magnets that occur through Orbach and Raman relaxation processes. Magnetochemistry 2019, 5, 30 2 of 12 of the representative cluster-type SMM [Mn III 8 Mn IV 4 O 12 (CH 3 COO) 16 (H 2 O) 24 ]·2CH 3 COOH·4H 2 O, which is based on first-row transition metal ions [19,20].Recently, chloralilate (Cl 2 An 2− ) bridged dinuclear Ln III complexes of the formula [{Ln III (Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 (Tp − = hydrotris(pyrazolyl)borate) have been reported in the literature [21][22][23][24]. In these complexes, the Dy III analogue displays a slow magnetic relaxation under small applied dc magnetic fields, thus behaving as a field-induced SMM [22][23][24]. This paper reports the syntheses, structures, and magnetic properties of a series of Cl 2 An 2− bridged dinuclear Ln complexes of the formula [{Ln(Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 [Ln = Gd (1), Tb (2), Ho (3), Er (4), and Yb (5)] to systematically investigate the magnetic properties in other Ln III analogues of [{Ln III (Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 .