Slow magnetic relaxation in two mononuclear Mn(ii) complexes not governed by the over-barrier Orbach process

Abstract

Two hexacoordinate Mn(II) complexes containing a chelating residue of hexafluoroacetylacetone and (Cl-substituted) 4-phenoxypyridine show DC magnetic functions typical for S = 5/2 spin systems: g ~ 2, D – small....

Binuclear cobalt(ii) and two-dimensional manganese(ii) coordination compounds self-assembled by mixed bipyridine-tetracarboxylic ligands with single-ion magnet properties

“…The observed Mn–N/O bond lengths fall within a narrow range of 2.065–2.284 Å, which strongly suggests that the Mn 2+ ion is in a high spin state (Table S2, ESI†). 11 The result of the CSM calculation yielded a value of 5.235 (Table S5, ESI†), which indicates a significant distortion of the Oh symmetry (Fig. 2d).…”

“…3 In recent years, much interest has been focused on the design and construction of 3d and 4f SIMs. 4,5 After the initial discovery of slow relaxation in a Fe 2+ complex with a four-coordinate trigonal pyramidal structure, 6 numerous mononuclear 3d complexes featuring Co 1+/2+ , 7–9 Fe 1+/2+/3+ , 10 Mn 2+/3+ , 11,12 Ni 1+/2+ , 13 and other 3d metal centers, with varying coordination numbers and molecular symmetries, have been synthesized and identified as SIMs. The large magnetic anisotropy in these reported complexes plays a vital effect on slow magnetic relaxation.…”

“…However, some first transition species with isotropic spin ground states, such as Mn 2+ and Cu 2+ , can also show field-support SIM behavior because of the packed electronuclear spin states induced by the applied dc field and hyperfine interaction. 11,14,15 However, such slow-relaxing complexes remain extremely rare. 11…”

“…Compared with the mononuclear SIMs, the number of mentioned slow-relaxing multinuclear complexes and coordination polymers is relatively small. 11 For example, binuclear SIM systems are barely reported. We recently reported the first SIM metallocycle, which contains two non-magnetic-coupled Co 2+ ions in a distorted tetrahedral geometry.…”

Slow Magnetic Relaxation in Silver(II) Macrocyclic Systems

“…Magnetic bistability resulting from large magnetic anisotropy and spin has been extensively studied in the so-called single-molecule magnets (SMMs), but other systems exhibiting slow relaxation of magnetization with different origins, usually under an external applied field, are of current interest. These kinds of molecules are (i) the so-called quasi-isotropic slow-relaxing molecules, mainly related with half-filled shell d 5 (Mn II ) or f 7 (Gd III ) cations, − and (ii) the systems with S = 1 / 2 , restricted to some VO 2+ , Cu II derivatives, and one example for Ir IV or Fe III . − These families of molecules have in common that their slow magnetic relaxation cannot be explained as an overbarrier relaxation: the former because there is no possibility of significant anisotropy-dependent barrier and the latter because there are no available magnetic states apart from ± m S = 1 / 2 . In both cases, slow magnetic relaxation should be attributed to other magnetic relaxation paths.…”