Field-Induced Slow Magnetic Relaxation of a Six-Coordinate Mononuclear Manganese(II) and Cobalt(II) Oxamate Complexes

Abstract

Two air-stable, isostructural, mononuclear six-coordinate manganese­(II) and cobalt­(II) oxamate complexes, [M(4-HOpa)2(H2O)2] [4-HOpa = N-4-hydroxyphenyloxamate; M= Mn2+ (1) or Co2+ (2)], exhibit field-induced slow magnetic relaxation. A bottleneck process is observed throughout the temperature range of 2–20 K for 1, while for 2, it dominates only at low temperatures (2–4 K). Additionally, the Raman process [n = 6.9(2)] is responsible for an increase in the relaxation time at higher temperatures to 2.

Layered Uranyl Phosphonates Encapsulating Co(II)/Mn(II)/Zn(II) Ions: Exfoliation into Nanosheets and Its Impact on Magnetic and Luminescent Properties

“…For CoU , the simulation is done using the | D | value obtained by SQUID (67.2 cm −1 ), while adjusting the zero‐field splitting parameter E and intrinsic g values, which gives an axial g‐tensor ( g x = g y =2.58(2), g z =2.42(2)), and | E |=16.8(2) cm −1 ( E / D ∼0.22)) (Figure 8). Because D >0, the m s =±1/2 doublet is below the m s =±3/2 doublet and 2 D represents the energy separation between the ±1/2 and ±3/2 doublets arising from second‐order spin‐orbit coupling (SOC) of the quartet ground state of the axially distorted octahedral Co 2+ [68] . We also measured the HF‐EPR of CoU‐190 and CoU‐ns but the curves cannot be reasonably analyzed.…”

“…2) in the temperature range 1.8-2.8 K. The best fits gave C = 231.2 K À 2.72 s À 1 , n = 2.72 for MnU, C = 808.9 K À 1.98 s À 1 , n = 1.98 for MnU-170, and C = 274.5 K À 3.05 s À 1 , n = 3.05 for MnU-ns. Notably, only a handful examples of Mn(II) complexes were reported to show fieldinduced slow magnetic relaxation (Table S9), [66][67][68] attributed to the magnetically isotropic nature of the high spin Mn(II) ion with very small zero-field splitting. It is interesting that MnU-ns shows very similar magnetic dynamics to its crystalline counterpart, unlike the case of CoU-ns.…”

“…Because D > 0, the m s = � 1/2 doublet is below the m s = � 3/2 doublet and 2D represents the energy separation between the � 1/2 and � 3/2 doublets arising from second-order spin-orbit coupling (SOC) of the quartet ground state of the axially distorted octahedral Co 2 + . [68] We also measured the HF-EPR of CoU-190 and CoU-ns but the curves cannot be reasonably analyzed.…”

Hexacoordinate high-spin Fe(iii) complexes composed of a pentadentate amino-type ligand and pseudohalido coligands

“…Recently, in a couple of S = 5/2 spin systems (Mn( ii ), Fe( iii )) a slow magnetic relaxation supported by the external magnetic field has been detected 3–5 This phenomenon is a “dance on thin ice” as well.…”

Solvothermal synthesis, structure and magnetic properties of heterometallic coordination polymers based on a phenolato-oxamato co-bidentate-tridentate ligand

“…11,12 Similar issues have been observed with the para-substitued phenyloxamate ligands, with either carboxylato or hydroxido additional groups where the oxamate and the additional coordinating groups are only partially or not at all binding (Scheme 1, b-e). [13][14][15][16] On the other hand, the ortho-substituted carboxylato-phenyloxamate ligand has been reported entirely coordinating in homometallic copper-based polymers (Scheme 1g). 17 These observations led us to recently investigate the reactivity of the ortho-subsituted N-(2-hydoxyphenyl)oxamic acid (H3ohpma).…”