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.

Four 2p-4f Ln-radical complexes, [(NIT-2-Pm)Ln(hfac)]·0.5CH (NIT-2-Pm = 2-pyrimidyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-oxide, hfac = hexafluoroacetylacetonato, Ln = Tb (1), Dy (2), Ho (3) and Er (4)), and four 4f-2p-4f Ln-radical-Ln complexes, [(μ-NIT-2-Pm)Ln(hfac)(HO)]·0.5CH (Ln = Tb (5), Dy (6), Ho (7) and Er (8)) have been synthesized and characterized structurally and magnetically. These compounds can be selectively obtained by controlling the reaction ratio of Ln(hfac)·2HO to the radical ligand NIT-2-Pm. The crystal structures show that in the former four complexes 1-4, the NIT-2-Pm radical acts as a terminal bidentate ligand chelating to one Ln ion, while in 5-8, the NIT-2-Pm acts as a bridging ligand linking two Ln ions to form a binuclear three-spin system. Magnetic studies revealed that complexes 1-4 and 6 show frequency-dependent ac magnetic susceptibilities, suggesting a possible single-molecule magnet behavior. To the best of our knowledge, complexes 3 and 4 are the first Ho-NIT and Er-NIT compounds showing slow magnetic relaxation. Compounds 5-8 represent a rare family of compounds showing the NIT bridged 4f-2p-4f three-spin motif, while complex 6 is a rare NIT bridged multinuclear lanthanide compound possessing SMM-like behaviour. Ab initio calculations were performed on all these complexes. The fitting of the magnetic susceptibilities of these compounds suggests weak antiferromagnetic coupling between the Ln and NIT radical in 1-8 and weak ferromagnetic Ln-Ln interactions in 5-8.

Crystal structures and magnetic properties of three one-dimensional (1D) azido-bridged cobalt(II) chains with different amide ligands (L), [Co(N)(DMF)] (1), [Co(N)(DEF)] (2), and [Co(N)(DIPF)] (3) (DMF = N,N-dimethylformamide, DEF = N,N-diethylformamide, and DIPF = N,N-diisopropylformamide), are reported to investigate the influence of L on their structures and magnetic properties. Single-crystal X-ray crystallographic analysis revealed that, although 1-3 all consist of cobalt chains bridged by end-on (EO) azides, the coordination geometry of the Co ions and the repeating units of the 1D structures are quite different. As the size of L increases, the ratio of L to Co decreases from 6:4 in 1 to 5:4 and 4:4 in 2 and 3, respectively. In 1, two [CoNO] and two [CoNO] distorted octahedra form the {[CoNO][CoNO][CoNO]} tetramers (denoted as CoA), which are linked to each other by sharing the N-N edge to form the chain. Similarly, the chain structure of 3 is constructed from a similar tetramer unit {[CoN][CoNO][CoN]} (denoted as CoB), where half of the Co centers are in the [CoN] trigonal bipyramid because of the larger steric effect of the DIPF ligand, while, for compound 2 of the medium-sized amide, it has the transition structure between those of 1 and 3. The chain is composed of two different repeating units: CoA unit similar to that in 1 and CoB unit similar to that in 3. Because of their similar structures, compounds 1-3 exhibit analogical magnetic properties. Direct-current magnetic measurements demonstrated that all compounds show intrachain ferromagnetic coupling through the EO azides and interchain anti-ferromagnetic interactions. Alternating-current data revealed the slow magnetic relaxation in the anti-ferromagnetic ordered phases. While compound 1 exhibits spin glass behavior, compounds 2 and 3 behave as the single-chain magnets. This difference might come from the interference of the anti-ferromagnetic ordering on the magnetic dynamic of the magnetic chain.