Hierarchical Assembly of a {Co24} Cluster from Two Vertex-Fused {Co13} Clusters and Their Single-Molecule Magnetism

Unexpected formation of a dodecanuclear {CoII6CuII6} nanowheel under ambient conditions: magneto-structural correlations

We report the unique heterobimetallic dodecanuclear oxamate-based {CoII6CuII6} nanowheel obtained using an environmentally friendly synthetic protocol. The effective Hamiltonian methodology employed herein allows the rationalisation of magnetic isotropic or anisotropic metal clusters, being a significant advance for future studies of exciting properties only observed at low and ultralow temperatures.

Hierarchical Construction and Magnetic Difference of {Co12M12} (M = Co2+/Cd2+) Aggregates from {Co14} Cluster-Based Precursors in the Presence of Homo/Heterometal Salts

The controllable construction and function expansion of some sophisticated aggregations represent a current hot topic in scientific research. In this paper, using a prefabricated {Co₁₄} cluster as a synthetic precursor, a homometallic {Co₂₄} and a heterometallic {Co₁₂Cd₁₂} giant cluster possessing similar dual-[M₁₂] (M = Co/Cd) skeletons was prepared by reacting the precursor with excess CoCl₂ and Cd(OAc)₂ salts, respectively. The detailed structural information on {Co₂₄} and {Co₁₂Cd₁₂} was characterized by single-crystal X-ray diffraction and further analyzed by X-ray photoelectron spectroscopy, inductively coupled plasma-mass spectroscopy, and scanning electron microscopy with energy dispersive X-ray (EDX) spectroscopy in the solid state. Compared to the {Co₁₄} precursor, magnetic difference revealed that spin-canting and magnetic ordering had been enhanced in {Co₂₄} and suppressed in {Co₁₂Cd₁₂} when dotted with diamagnetic Cd²⁺ ions.

Modulating Magnetic and Photoluminescence Properties in 2-Aminonicotinate-Based Bifunctional Coordination Polymers by Merging 3d Metal Ions

Herein, the synthesis and study of bifunctional coordination polymers (CPs) with both magnetic and photoluminescence properties, derived from a heterometallic environment, are reported. As a starting point, three isostructural monometallic CPs with the formula [M(μ-2ani)₂ ]_n (M^II =Mn (1_Mn ), Co (3_Co ) and Ni (4_Ni ); 2ani=2-aminonicotinate), crystallise as chiral 2D-layered structures stacked by means of supramolecular interactions. These compounds show high thermal stability in the solid state (above 350 °C), despite which, in aqueous solution, compound 1_Mn is shown to partially transform into a novel 1D chain CP with the formula [Mn(2ani)₂ (μ-H₂ O)₂ ]_n (2_Mn ). A study of the direct current (dc) magnetic properties of 1_Mn , 3_Co and 4_Ni reveals a spin-canted structure derived from antisymmetric antiferromagnetic weak exchanges along the chiral network (as confirmed by DFT calculations) and magnetic anisotropy of the ions, in such a way that long-range ordering is observed with variable magnitude for the spin carriers. Moreover, compounds 3_Co and 4_Ni show no frequency-dependent alternating current (ac) susceptibility curves under zero dc field; this is characteristic behaviour of a glassy state that may be partially supressed for 3_Co by applying an external dc field. To overcome long-range magnetic ordering, Co^II ions are diluted in a diamagnetic Zn^II -based matrix, which enables single-molecule magnet behaviour. Interestingly, this strategy allows a bifunctional Co_x Zn_1-x 2ani material, which is imbued with a strong photoluminescent emitting capacity, as characterised by an intense blue light followed by a green afterglow, to be obtained.

Magnetic and Photoluminescent Sensors Based on Metal-Organic Frameworks Built up from 2-aminoisonicotinate

In this work, three isostructural metal-organic frameworks based on first row transition metal ions and 2-aminoisonicotinate (2ain) ligands, namely, {[M(μ-2ain)₂]·DMF}_n [M^II = Co (1), Ni (2), Zn (3)], are evaluated for their sensing capacity of various solvents and metal ions by monitoring the modulation of their magnetic and photoluminescence properties. The crystal structure consists of an open diamond-like topological 3D framework that leaves huge voids, which allows crystallizing two-fold interpenetrated architecture that still retains large porosity. Magnetic measurements performed on 1 reveal the occurrence of field-induced spin-glass behaviour characterized by a frequency-independent relaxation. Solvent-exchange experiments lead successfully to the replacement of lattice molecules by DMSO and MeOH, which, on its part, show dominating SIM behaviour with low blocking temperatures but substantially high energy barriers for the reversal of the magnetization. Photoluminescence studied at variable temperature on compound 3 show its capacity to provide bright blue emission under UV excitation, which proceeds through a ligand-centred charge transfer mechanism as confirmed by time-dependent DFT calculations. Turn-off and/or shift of the emission is observed for suspensions of 3 in different solvents and aqueous solutions containing metal ions.

A novel sandwich shaped {CoIII2CoII12MoV24} cluster with a CoII4 triangle encapsulated in two capped CoIIICoII4MoV12O40 fragments

A novel discrete {Co₁₄Mo₂₄} nanoscaled cluster, with a triangle Co₄ core encapsulated in two novel capped Co-substituted Keggin-type Co₅Mo₁₂O₄₀ anions, was isolated from alkaline methanol solution. And the HRESI-MS of {Co₁₄Mo₂₄} cluster was recorded.

The stepwise substitution in the hierarchical building of {Co11Cd6} cluster-based MOFs from {Co14} precursor

A heterometallic aggregation of {Co₁₁Cd₆} can be hierarchical built from a {Co₁₄} precursor directly. HRESI-MS technique was used to track the stepwise Cd²⁺-capture: {Co₁₄} → {Co₈} → {Co₈Cd₂} → {Co₈Cd₃} → {Co₈Cd₄} → {Co₈Cd₅} → {Co₈Cd₆} → {Co₁₁Cd₆}.

Tetrahedral μ4-chloride and in situ generated octahedral μ6-sulfide templating Co8 complexes with different distortions of the cube

Herein two unprecedented octanuclear Co8 clusters are presented, [Cl@Co8 (TEOA)4(CH3CN)Cl3] (1) and [S@Co8(DEOA)6(NCS)2] (2) (H3TEOA = triethanolamine, H2DEOA = diethanolamine), in which tetrahedral μ4-chloride and in situ generated octahedral μ6-sulfide are used as templates. In spite of them being derivatives of cubes, eight Co atoms in 1 consist of two co-centered tetrahedra of different sizes, whereas in 2 they appear as a rhombohedron formed via elongating a cube along the C3-axis direction. Strong intra-cluster antiferromagnetic interactions were found.