Slow Magnetic Relaxation and Spin‐Crossover Behavior in a Bicomponent Ion‐Pair Cobalt(II) Complex

Abstract

A bicomponent ion‐pair molecule compound [Co(Brphterpy)2][Co(NCS)4]·2MeCN was designed and prepared for the construction of multistable functional materials. Due to the different coordination geometries of the cationic and anionic CoII ions, this compound exhibits both thermally induced spin crossover (SCO) and field‐induced single‐ion magnetism (SIM). This represents a rare example of a two‐component system with the coexistence of SIM and SCO behaviors and suggests a simple, yet very efficient strategy for the construction of multistable molecular materials.

Two Interpenetrated Cobalt(II) Metal–Organic Frameworks with Guest-Dependent Structures and Field-Induced Single-Ion Magnet Behaviors

“…The highest U eff has now over 1000 cm –1 (1277 cm –1 ), and the highest blocking temperature (60 K) is approaching the boiling point of liquid nitrogen. , Besides the lanthanide SIMs, SIMs with 3d metal centers have also aroused a growing interest. After the first Fe II SIM in 2010, a large amount of 3d SIMs with different metal centers have been reported. − Among all these SIMs, the Co­(II) complexes are of special interest. For this Kramers ion, slow magnetic relaxation can always be observed under a dc field, provided the existence of significant magnetic anisotropy. , This character makes the design of the Co II SIMs somehow easier and has resulted in a range of Co II SIMs, not only in the structurally isolated single-ion systems − but also in the extended coordination polymers, such as in the one-dimensional (1D), − two-dimensional (2D), − and even three-dimensional (3D) metal–organic frameworks (MOFs). , Actually, studies of the SMM properties in the MOFs materials could lead to great chances to systematically tune the magnetic properties of SMMs. , On the one hand, SMMs, even those with rather large volumes, can be loaded into the cavity of the MOFs.…”

Effect of Coordination Geometry on Magnetic Properties in a Series of Cobalt(II) Complexes and Structural Transformation in Mother Liquor

“…Thus, in order to minimize the probability of the quantum relaxation pathway in zero dc field and to estimate the energy barrier accurately, the ac susceptibility was measured under different dc fields. It is worth mentioning that no slow relaxation of magnetization was detected in the case of complex 1 from ac susceptibility measurements even by using a 6000 Oe dc magnetic field (Figure S21), although slow relaxation of magnetization has recently been reported in [Co­(N3) 2 ]­[Co­(NCS) 4 ] (N3 = tridentate N-donor ligand) types of complexes as well as in the [Co­(NCS) 4 ] 2– unit with different metal cation complexes. − …”

Tuning chain topologies and magnetic anisotropy in one-dimensional cobalt(ii) coordination polymers via distinct dicarboxylates

“…In fact, due to both the spin and the orbital contributions to the magnetic moment, Co 2+ ions in various coordination geometries and environments usually have significant magnetic anisotropy. Thus, this metal source is widely used for the design and preparation of molecular magnetic materials, including SIMs, 8 a – d SMMs, 9 single-chain magnets (SCMs), 10 spin-crossover complexes, 11 and magnetic ordering materials. 12…”