Polynuclear Cobalt(II/III) Sulfites: Synthesis, Structure, and Magnetic Properties of the Octanuclear Cluster (NH4)11(Li⊂[Co4IICo4III(SO3)16(NH3)8])·10H2O Encapsulating a Lithium Cation

Cr-Ti Mixed Oxide Molecular Cages: Synthesis, Structure, Photoresponse, and Photocatalytic Properties

The solvothermal reaction of titanium isopropoxide and chromate in the presence of benzoate produced two novel host-guest clusters encapsulating Cs⁺ or H₃O⁺, (H₃O)@Ti₇Cr₁₄ and Cs@Ti₇Cr₁₄. The most remarkable feature is that the Ti₇O₇ ring is concentrically embraced by a Cr₁₄O₁₄ ring to form a rigid Ti₇Cr₁₄ host. ESI-MS and ¹³³Cs NMR revealed that the overall framework structures are preserved, whereas the benzoate ligands on the two clusters may be labile in solutions. Both (H₃O)@Ti₇Cr₁₄ and Cs@Ti₇Cr₁₄ exhibit good UV-vis light-responsive properties and photocatalytic activities, with absorption edges extending up to 780 nm. Cs@Ti₇Cr₁₄ is an effective visible-light-responsive photocatalyst in both the heterogeneous methylene dye degradation and homogeneous CO₂ cycloaddition reaction under mild conditions like room temperature and 1 bar of CO₂. According to the mechanism studies, Cs⁺, as a rigid guest, can significantly improve the photogenerated charge separation efficiency of the Ti₇Cr₁₄ host, thereby improving its interface charge separation properties, photocurrent, and photocatalytic activities. Our findings not only provide new members of heterometallic titanium oxide clusters to enrich the metal oxide cluster family but also open up new possibilities for their photoresponses, which may play an important role in solar energy harvesting for sustainable chemistry.

Soluble Complexes of Cobalt Oxide Fragments Bring the Unique CO2 Photoreduction Activity of a Bulk Material into the Flexible Domain of Molecular Science

The deposition of metal oxides is essential to the fabrication of numerous multicomponent solid-state devices and catalysts. However, the reproducible formation of homogeneous metal oxide films or of nanoparticle dispersions at solid interfaces remains an ongoing challenge. Here we report that molecular hexaniobate cluster anion complexes of structurally and electronically distinct fragments of cubic-spinel and monoclinic Co₃O₄ can serve as tractable yet well-defined functional analogues of bulk cobalt oxide. Notably, the energies of the highest-occupied and lowest-unoccupied molecular orbitals (HOMO and LUMO) of the molecular complexes, 1, closely match the valence- and conduction-band (VB and CB) energies of the parent bulk oxides. Use of 1 as a molecular analogue of the parent oxides is demonstrated by its remarkably simple deployment as a cocatalyst for direct Z-scheme reduction of CO₂ by solar light and water. Namely, evaporation of an aqueous solution of 1 on TiO₂-coated fluorinated tin oxide windows (TiO₂/FTO), immersion in wet acetonitrile, and irradiation by simulated solar light under an atmosphere of CO₂ give H₂, CO, and CH₄ in ratios nearly identical to those obtained using 20 nm spinel-Co₃O₄ nanocrystals, but 15 times more rapidly on a Co basis and more rapidly overall than other reported systems. Detailed investigation of the photocatalytic properties of 1 on TiO₂/FTO includes confirmation of a direct Z-scheme charge-carrier migration pathway by in situ irradiated X-ray photoelectron spectroscopy. More generally, the findings point to a potentially important new role for coordination chemistry that bridges the conceptual divide between molecular and solid-state science.

Tetranuclear cobalt(ii)-isonicotinic acid frameworks: selective CO2 capture, magnetic properties, and derived "Co3O4" exhibiting high performance in lithium ion batteries

Two new 3D cobalt metal-organic frameworks (MOFs), [Co4(CH3COO)(in)5(μ3-OH)2]·2H2O (1) and [Co4(SO4)2(in)4(DMF)2]·3DMF (2) (Hin = isonicotinic acid), have been prepared through the anion template method. Compound 1 consists of rare odd-number connected (9-connected) cubane-like SBUs, while compound 2 consists of 8-connected high-symmetry square-planar clusters. Magnetic studies indicate that compound 1 exhibits spin-canting antiferromagnetic ordering, while compound 2 shows antiferromagnetic behavior. At 273 K and 1 bar, compound 1 exhibits a high CO2 selectivity over CH4 and a significant CO2 uptake of 13.6 wt%, which is higher than that of 2 (8.5 wt%). Furthermore, compound 1 was then transformed into ultrasmall Co3O4 nanoparticles via simple but effective annealing treatment. Electrochemical measurements show that the Co3O4 nanospheres derived from compound 1 exhibited high and stable lithium storage properties (1100 mA h g-1 after 100 cycles at 200 mA g-1) and excellent rate capabilities.

Self-assembly, structures, magnetic properties and solution behaviors of six mixed-valence cobalt clusters

Six novel mixed-valence cobalt clusters with flexible {Co^II_xCo^III_y} cores have been constructed via in situ synthesis and stepwise synthesis routes. Their solution behaviors and possible assembly evolutions were detected by HRESI-MS. All of them also show interesting magnetic behaviours.

The first organically templated open-framework metal-sulfites with layered and three-dimensional diamondoid structures

The crystallographic signatures and characterization data of two novel organically templated open-framework zinc-sulfite (NH₃CH₂CH₂NH₃)[Zn₃(SO₃)₄], 1 and (CN₃H₆)₂[Zn(SO₃)₂], 2 are reported for the first time using different amines to generate 2D (for 1) and 3D (for 2) assemblies with 4, 6, 8 and 12-membered rings.

H-bond supported coordination polymers of transition metal sulfites with different dimensionalities

Three novel transition metal–sulfite coordination complexes are synthesized using different amines and the role of H-bonding to provide structures with different dimensionalities are discussed.

A new strategy for storage and transportation of sensitive high-energy materials: guest-dependent energy and sensitivity of 3D metal-organic-framework-based energetic compounds

Reaction of Co(II) with the nitrogen-rich ligand N,N-bis(1H-tetrazole-5-yl)-amine (H2bta) leads to a mixed-valence, 3D, porous, metal-organic framework (MOF)-based, energetic material with the nitrogen content of 51.78%, [Co9(bta)10(Hbta)2(H2O)10]n⋅(22 H2O)n (1). Compound 1 was thermohydrated to produce a new, stable, energetic material with the nitrogen content of 59.85% and heat of denotation of 4.537 kcal cm(-3), [Co9(bta)10(Hbta)2(H2O)10]n (2). Sensitivity tests show that 2 is more sensitivity to external stimuli than 1, reflecting guest-dependent energy and sensitivity of 3D, MOF-based, energetic materials. Less-sensitive 1 can be regarded as a more safe form for storage and transformation to sensitive 2.

3d-Metal derivatives of the [Cu(I)(SO3)4]7- ion: structure and magnetism

The Cu(SO(3))(4)(7-) anion, which consists of a tetrahedrally coordinated Cu(I) centre coordinated to four sulfur atoms, is able to act as a multidentate ligand in discrete and infinite supramolecular species. The slow oxidation of an aqueous solution of Na(7)Cu(SO(3))(4) yields a mixed oxidation state, 2D network of composition Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O. The addition of Cu(II) and 2,2'-bipyridine to an aqueous Na(7)Cu(SO(3))(4) solution leads to the formation of a pentanuclear complex of composition {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(+); a combination of hydrogen bonding and π-π stacking interactions leads to the generation of infinite parallel channels that are occupied by disordered nitrate anions and water molecules. A pair of Cu(SO(3))(4)(7-) anions each act as a tridentate ligand towards a single Mn(II) centre when Mn(II) ions are combined with an excess of Cu(SO(3))(4)(7-). An anionic pentanuclear complex of composition {[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)} is formed when Fe(II) is added to a Cu(+)/SO(3)(2-) solution. Hydrated ferrous [Fe(H(2)O)(6)(2+)] and sodium ions act as counterions for the complexes and are responsible for the formation of an extensive hydrogen bond network within the crystal. Magnetic susceptibility studies over the temperature range 2-300 K show that weak ferromagnetic coupling occurs within the Cu(II) containing chains of Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O, while zero coupling exists in the pentanuclear cluster {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(NO(3))·H(2)O. Weak Mn(II)-O-S-O-Mn(II) antiferromagnetic coupling occurs in Na(H(2)O)(6){[Cu(I)(SO(3))(4)][Mn(II)(H(2)O)(2)](3)}, the latter formed when Mn was in excess during synthesis. The compound, Na(3)(H(2)O)(6)[Fe(II)(H(2)O)(6)](2){[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)}·H(2)O, contained trace magnetic impurities that affected the expected magnetic behaviour.