Slow relaxation of the magnetization in a {CoIIIMnIII} heterometallic brick-wall network. (15th May 2021)

• Record Type: Journal Article
• Authors: Alexandru, Maria-Gabriela; Visinescu, Diana; Shova, Sergiu; Stiriba, Salah-Eddine; Cano, Joan; Lloret, Francesc; Julve, Miguel
• Is Part Of: Polyhedron. Volume 200(2021)
• Publication Date: 2021-05-15
• Subjects: Hererometallic complexes -- Cobalt(III) complexes -- Manganese(III) complexes -- Cyanide compounds -- 2, 5-bis(2-pyridyl)pyrazine complexes -- Single-ion magnets; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2021.115118
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: By the assembling of the cyanide-bearing dicobalt(III) anion, [Co2 III (μ-2, 5-dpp)(CN)8 ] 2−, as a metalloligand with [Mn(salen)(H2 O)] + cation, a heterobimetallic 2-D compound of formula [{Mn III (salen)}2 {(μ-NC)4 Co2 III (μ-2, 5-dpp)(CN)4 }] n (1 ), showing slow magnetic relaxation, was formed. Abstract: The use of the cyanide-bearing dicobalt(III) complex (PPh4 )2 [Co2 III (μ−2, 5-dpp)(CN)8 ] as a metalloligand towards [Mn(salen)(H2 O)]ClO4 afforded the heterobimetallic two-dimensional compound of formula [{Mn III (salen)}2 {(μ-NC)4 Co2 III (μ−2, 5-dpp)(CN)4 }] n (1 ) [PPh4 + = teraphenylphosphonium cation, 2, 5-dpp = 2, 5-bis(2-pyridyl)pyrazine and H2 salen = N, N' -ethylenebis(salicylideneimine)] whose structure has been determined by single crystal X-ray diffraction. Compound 1 exhibits a neutral brick-wall structure, where each [Co2 III (μ−2, 5-dpp)(CN)8 ] 2− unit adopts a tetrakis-monodentate bridging mode towards four {Mn III (salen)} + fragments through four of its eight cyanide ligands. Each cobalt(III) ion is six-coordinate with one pyrazine- and one pyridine-nitrogen atoms of the 2, 5-dpp molecule and four cyanide-carbon atoms describing a somewhat distorted octahedral surrounding. The two crystallographically independent manganese(III) ions are also six-coordinate in an elongated octahedral environment with two imino-nitrogen and two phenoxo-oxygen atoms occupying the equatorial positions and two cyanide-nitrogen atoms filling the axial sites. Variable-temperature direct- (1.9–300 K) and alternating-current (2.0–5.0 K) magnetic measurements of 1 show the occurrence of magnetically isolated manganese(III) ions with a local negative zero-field splitting ( D = −5.87 cm −1 ) and slow magnetic relaxation, this compound being a new example of field-induced Single-Ion Magnet (SIM). The analysis of the ac magnetic data of 1 under an applied dc field of 5000 G reveals that the value of the energy barrier ( E a ) to reverse the magnetization direction and that of the pre-exponential factor (τ0 ) are 10.8 cm −1 and 2.7 × 10 −8 s, respectively. These values compare well with those reported for the few examples of manganese(III)-based SIMs nowadays.