A Homochiral {CoΙΙ16CoΙΙΙ4} SupertetrahedralT4Cluster from a Racemic Ligand with Ferromagnetic Behavior and High Photocatalytic Activity

Coordination-Driven Heterochiral Self-Assembly: Construction of Cd(II) Coordination Polymers with Sorption Behaviors for Iodine and Dyes

A racemic bispyridyl ligand (L) was synthesized via a Schiff base condensation reaction. Four Cd(II) complexes, {[CdL2Cl2]·2DMF}n (1), [CdLI2]n (2), {[CdL2Br2]·4H2O}n (3), and {[CdL2(H2O)2](NO3)2·2CH3OH·8H2O}n (4), were synthesized and further characterized based on this ligand. Single-crystal structures show that the coordination-driven assembly of the bispyridyl ligand with Cd(II) salts bearing different counteranions can lead to multidimensional coordination polymers via a heterochiral self-discrimination process. Complex 1 exists as a one-dimensional (1D) looped chain polymer, and complex 2 exists as a 1D zigzag chain polymer. Complex 3 is a 2D grid coordination polymer, and complex 4 exists as a 3D framework polymer. Furthermore, the iodine sorption capacities of the four complexes were investigated in the solution of n-hexane and water as well as in the iodine steam. The dye sorption behaviors were investigated in water, which showed that complex 2 exhibited good adsorption for crystal violet (CV), while complex 4 had good adsorption capability toward direct yellow 4 (DY).

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

Designed assembly of heterometallic zeolite-like framework materials from two different supertetrahedral metal clusters

This work demonstrates a feasible strategy for the synthesis of new zeolite-like framework materials. With the strategy of using two different supertetrahedral clusters as secondary building units, two new heterometallic zeolite-like frameworks with isomeric structures but tunable topologies were first made. Besides, the porous nature and the proton conduction performance of the new materials were further studied.

High nuclearity structurally - related Mn supertetrahedral T4 aggregates

The simultaneous employment of 1,3-propanediol and di-2-pyridyl ketone in Mn carboxylate chemistry has provided access to three new, structurally-related [Mn₂₄] and [Mn₂₃] clusters. They are based on nanosized supertetrahedal T4 Mn/O structural cores and exhibit slow relaxation of magnetization below 3.5 K.

Cubes on a string: a series of linear coordination polymers with cubane-like nodes and dicarboxylate linkers

A series of semicrystalline and amorphous one-dimensional (1D) polymeric chains consisting of cubane-like CoII4L4 units (L = S-1,2-bis(benzimidazol-2-yl)ethanol) and dicarboxylates were synthesized and characterized by single crystal diffraction and X-ray total scattering. The polycationic chains are composed of [Co4L4(dicarboxylate)]2+ monomeric units, while one molecular dicarboxylate counterion is balancing the charge of each monomer. The linear compound series has five members, and the crystal structures were solved for [Co4L4(tph)](tph) and [Co4L4(ndc)](ndc), where tph = terephthalate and ndc = 2,6-naphthalenedicarboxylate. Partly crystalline compounds were produced by slow assembly at elevated temperature (over days), while the amorphous compounds were formed by fast precipitation (within minutes). Pair distribution function (PDF) analysis based on X-ray total scattering data reveals the presence of the cubane-like entity in both the amorphous and semicrystalline samples. While the powders are non-porous, precipitation is a fast and versatile method to produce compounds with cubane-like centres with moderate surface areas of 17-49 m2 g-1 allowing for surface chemical reactions. The powders have a high concentration of Lewis base sites as verified by their selective adsorption of CO2 over N2. The use of an amorphous cubane-like polymer for the electrocatalytic oxygen evolution reaction was demonstrated.

Structural characterization and magnetic property studies of a mixed-valence {CoIIICo} complex with a μ4-oxo tetrahedral {Co} motif

We have synthesized and structurally characterized a new mixed valence pentanuclear Co complex, bearing a rare μ4-O-tetrahedral CoII4 unit, by employing a pyridine-like Schiff base ligand. We have performed DC magnetic susceptibility and magnetization measurements over polycrystalline samples and chemical quantum computations in order to understand the exchange interaction pattern within Co(ii) sites and ground state magnetic anisotropy. This new complex shows an overall antiferromagnetic exchange interaction whose strength strongly depends on the local symmetry of Co(ii) sites. Also, local ion magnetic anisotropy reveals a strongly axial behaviour with the lowest Kramers doublet (KD) at each Co(ii) ion sufficiently isolated from excited states at low temperatures. Two Co(ii) sites show tetrahedral symmetry and the spin only formalism including axial zero-field splitting (ZFS) term properly described them; on the other hand, the other two Co(ii) sites have distorted octahedral and square base pyramidal coordination spheres, and a strong orbital contribution leads to a failure of the spin only formalism. A model of four Seff = 1/2 exchange interacting sites is necessary in order to account for low temperature magnetization behaviour. In view of the strongly anisotropic KD states, the exchange interactions are forced to be modelled as anisotropic ones. Overall, experimental data and quantum chemical computations are in good agreement, supporting the proposed model for magnetic behaviour.

A Chiral and Polar Single-Molecule Magnet: Synthesis, Structure, and Tracking of Its Formation Using Mass Spectrometry

The solvothermal reaction of cobalt(II) sulfate with S, S-1,2- bis(1-methyl-1 H-benzo[ d]imidazol-2-yl)ethane-1,2-diol, (H₂L), neutralized with triethylamine (Et₃N) in a mixture of methanol and water (2:1), resulted in triangular red crystals of [Co^II₇(L)₃(SO₄)₃(OH)₂(H₂O)₉]·4H₂O·3CH₃OH (Co₇). It is formed of chiral and polar clusters crystallizing in the R₃ space group. Co₇ consists of apex-shared asymmetric dicubane units where all of the metals adopt an octahedral coordination and the three ligands wrap diagonally around the unit. One end of the cluster is bonded by six water molecules and the other end by three monodentate sulfates. The head-to-tail packing through extended H-bonds leads to polar chains. The ligand has lost two protons, adopts a cis-conformation, and is coordinated to five metals around the waist of the dicubane. Electrospray ionization mass spectrometry (ESI-MS) of solutions of the reaction as a function of time reveals the possible step-by-step assembly process of the cluster: the initial product [Co^II(HL)(SO₄)]^2- combines with CoSO₄, forming [Co^II₂(HL)(SO₄)₂]^2-, and then, upon addition of Et₃N, dimerizes through a [OH]^- bridge to [Co^II₄(HL)₂(OH)(CH₃OH)₂(SO₄)₃]^- followed by capture of one Co²⁺ and one CoSO₄ to form [Co^II₆(L)₂(OH)(CH₃O)(SO₄)₄]^2- before eventually binding to CoL to form [Co^II₇(L)₃(OH)₂(SO₄)₄]^2-. These results allow us to propose a possible process for the formation of Co₇, which is a good example for chiral multidentate chelating ligand-controlled assembly of clusters. Magnetization measurements as a function of the temperature, field, and ac-frequency reveal ferromagnetic coupled moments and single-molecule magnetism (SMM).

Spontaneous Resolution by Crystallization of an Octanuclear Iron(III) Complex Using Only Racemic Reagents

The P and M enantiomers of the octanuclear [Fe₈ (μ₄ -O)₄ (μ-4-Cl-pz)₁₂ Cl₄ ] complex, having T symmetry, were resolved by temporary substitution of chloride ligands by racemic 4-^s Bu-phenolates and subsequent crystallization, where the (S)- and (R)-phenolates coordinate selectively to the M and P complexes, respectively. The complexes were characterized by circular dichroism analysis and X-ray structure determination. This work constitutes a rare example of enantiomeric recognition resulting in spontaneous resolution upon crystallization.