Mesoporous MOF Based on a Hexagonal Bipyramid Co8-Cluster: High Catalytic Efficiency on the Cycloaddition Reaction of CO2 with Bulky Epoxides

A mesoporous cobalt-based metal-organic framework (LCU-606) was synthesized based on a hexagonal bipyramid Co8(μ4-O)3 cluster and an N,N,N',N'-tetrakis-(4-benzoic acid)-1,4-phenylenediamine ligand (H4TBAP). LCU-606 featuring large pore diameters of 21.7 Å and exposed Lewis-acid metal sites could serve as an excellent heterogeneous catalyst for CO2 cycloaddition reaction with various epoxide substrates under mild conditions (1 atm CO2, 60 °C, and solvent free). In particular, when extending the substrates to bulkier ones, LCU-606 still shows high catalytic efficiency on account of the large pore aperture. Also, LCU-606 demonstrates high recyclability and stability in consecutive catalytic runs. Therefore, the high efficiency, recyclability, and generality on CO2 catalytic cycloaddition make LCU-606 a very promising heterogeneous catalyst for CO2 chemical fixation.

Syntheses, structures and magnetic properties of two CoII/NiII isostructural coordination polymers based on an asymmetric semirigid tricarboxylate ligand

Two new isostructural complexes, namely, poly[aqua[μ₃-2-(4-carboxyphenoxy)terephthalato-κ³O¹:O⁴:O^4'](1,10-phenanthroline-κ²N,N')cobalt(II)], [Co(C₁₅H₈O₇)(C₁₂H₈N₂)(H₂O)]_n or [Co(μ₃-Hcpota)(phen)(H₂O)]_n, I, and poly[aqua[μ₃-2-(4-carboxyphenoxy)terephthalato-κ³O¹:O⁴:O^4'](1,10-phenanthroline-κ²N,N')nickel(II)], [Ni(C₁₅H₈O₇)(C₁₂H₈N₂)(H₂O)]_n or [Ni(μ₃-Hcpota)(phen)(H₂O)]_n, II, have been synthesized by solvothermal reactions. Complexes I and II were fully characterized by IR spectroscopy, elemental analyses, thermogravimetric analyses, and powder and single-crystal X-ray diffraction. They both present two-dimensional structures based on [M₂(μ-COO)₂]²⁺ (M = Co^II or Ni^II) dinuclear metal units with a fes topology and a vertex symbol (4·8²). Interestingly, the positions of the two dimeric metal motifs and the two partially deprotonated Hcpota^2- ligands reproduce regular flying butterfly arrangements flipped upside down and sharing wings in the ab plane. Magnetic studies indicate antiferromagnetic interactions (J = -5.21 cm^-1 for I and -11.53 cm^-1 for II) in the dimeric units, with Co...Co and Ni...Ni distances of 4.397 (1) and 4.358 (1) Å, respectively, that are related to double syn-anti carboxylate bridges.

Crowding out: ligand modifications and their structure directing effects on brucite-like {Mx(μ3-OH)y} (M = Co(ii), Ni(ii)) core growth within polymetallic cages

Previous employment of the ligands 2-methoxy-6-[(methylimino)methyl]phenol (L₁H) and 2-methoxy-6-[(phenylimino)methyl]phenol (L₂H) has resulted in the self-assembly of pseudo metallocalix[6]arene complexes of general formulae: [M₇(μ₃-OH)₆(L_x)₆](NO₃)_y (M = Ni(ii), x = 1, y = 2 (1) and Co(ii/iii), x = 2, y = 3 (2)). Extrapolating upon this work, we report the coordination chemistry of ligands 2-methoxy-6-{[(2-methoxyphenyl)imino]methyl}phenol (L₃H), 2-[(benzylimino)methyl]-6-methoxyphenol (L₄H), 2-[(benzylamino)methyl]-6-methoxyphenol (L₅H) and 2-[(benzylamino)methyl]-4-bromo-6-methoxyphenol (L₆H), whose structures are modifications of ligands L_1-2H. These ligands are employed in the synthesis and characterisation of the dimetallic complex [Ni(ii)₂(L₃)₃(H₂O)](NO₃)·2H₂O·3MeOH (3); the monometallic complexes [Ni(ii)(L₄)₂] (4) and [Co(iii)(L₄)₃]·H₂O·MeOH (5a); and the tetranuclear pseudo metallocalix[4]arene complexes: [(NO₃)⊂Co(ii)₄(μ₃-OH)₂(L₅)₄(H₂O)₂](NO₃)·H₂O (6), [(NO₃)⊂Ni(ii)₄(μ₃-OH)₂(L₅)₄(H₂O)₂](NO₃)·H₂O (7) and [Ni(ii)₄(μ₃-OH)₂(L₆)₄(NO₃)₂]·MeCN (8). The tetrametallic 'butterfly' core topologies in 6-8 are discussed with respect to their structural and topological relationship with their heptanuclear [M₇] (M = Co(ii), Ni(ii)) pseudo metallocalix[6]arene ancestors (1 and 2).

Field-induced slow relaxation of magnetization in a distorted octahedral mononuclear high-spin Co(ii) complex

By adopting the strategy of mixed rigid ligands, two novel mononuclear complexes with distorted octahedral geometries are obtained. SIM-type slow magnetic relaxation behavior is observed in Co(ii)-based complexes.

Rare double spin canting antiferromagnetic behaviours in a [Co24] cluster

A fish-basket-shaped [Co₂₄] cluster, [Co₂₄(μ₃-O)₄(ampc)₄(μ₃-OH)₄(μ₂-OH)₄(NO₃)₅(HCO₂)₂₂(H₂O)₁₀]·[(HCO₂)·2(CH₃OH)·x(H₂O)], was woven by bridging oxygen atoms from O²⁻, OH⁻, NO₃⁻ and HCO₂⁻ groups, and stabilized terminally by a semi-rigid organic ligand 4′,4′-[(dimethylamino)dimethylene]-bis[(1,1′-biphenyl)-2-carboxylate] (ampc⁻).