一次元金属錯体の電子状態及び物性に対する面内配位子のヒドロキシ基の効果

要約のみTohoku University山下正廣課

Crystal structures of di-μ-chlorido-bis­({(E)-5-(ethyl­amino)-4-methyl-2-[(pyridin-2-yl)diazen­yl]phen­o­lato}copper(II)) and chlorido­bis­(1,10-phen­anthroline)copper(II) chloride tetra­hydrate

The dark-red title complex crystallized from an equimolar methanol solution of (E)-5-(ethyl­amino)-4-methyl-2-[(pyridin-2-yl)diazen­yl]phenol and CuCl2(phen) (phen = 1,10-phenanthroline) as a centrosymmetric dimer, [CuCl(C14H15N4O)]2. The Cu atoms are bridged by two Cl ligands and have a slightly distorted square-pyramidal coordination, where two N atoms from the azo and the pyridine moieties, a phenolic O and a Cl atom comprise the base and the other Cl occupies the apex position. The apical Cu—Cl bond, 2.6192 (4) Å, is longer than the basal one, 2.2985 (3) Å, due to Jahn–Teller distortion. The dimers are associated via weak inter­molecular hydrogen bonds and π–π stacking inter­actions between phenyl and pyridine rings. A monomeric by-product of the same reaction, [CuCl(phen)2]Cl·4H2O, has a trigonal–bipyramidal coordination of Cu with equatorial Cl ligand, and extensive outer-sphere disorder. In the structure of 4, the packing of cations leaves continuous channels containing disordered Cl− anions and solvent mol­ecules. The identity of the solvent (water or a water/methanol mixture) was not certain. The disordered anion/solvent regions comprise 28% of the unit-cell volume. The disorder was approximated by five partly occupied positions of the Cl− anion and ten positions of O atoms with a total occupancy of 3, giving a total of 48 electrons per asymmetric unit, in agreement with the integral electron density of 47.8 electrons in the disordered region, as was estimated using the BYPASS-type solvent-masking program [van der Sluis & Spek (1990). Acta Cryst. A46, 194–201]

Investigating Ligand Sphere Perturbations on Mn^III–Alkylperoxo Complexes

Manganese catalysts that activate hydrogen peroxide carry out several different hydrocarbon oxidation reactions with high stereoselectivity. The commonly proposed mechanism for these reactions involves a key manganese(III)-hydroperoxo intermediate, which decays via O–O bond heterolysis to generate a Mn(V)–oxo species that institutes substrate oxidation. Due to the scarcity of characterized MnIII–hydroperoxo complexes, MnIII–alkylperoxo complexes are employed to understand factors that affect the mechanism of the O–O cleavage. Herein, we report a series of novel complexes, including two room-temperature-stable MnIII–alkylperoxo species, supported by a new amide-containing pentadentate ligand (6Medpaq5NO2). We use a combination of spectroscopic methods and density functional theory computations to probe the effects of the electronic changes in the ligand sphere trans to the hydroxo and alkylperoxo units to thermal stability and reactivity. The structural characterizations for both MnII(OTf)(6Medpaq5NO2) and [MnIII(OH)(6Medpaq5NO2)](OTf) were obtained via single-crystal X-ray crystallography. A perturbation to the ligand sphere allowed for a marked increase in reactivity towards an organic substrate, a modest change in the distribution of the O–O cleavage products from homolytic and heterolytic pathways, and little change in thermal stability

Constraining Flexibility in the MIL-88 Topology through Integration of 3-Dimensional Linkers

ABSTRACT: Metal−organic frameworks (MOFs) make up a class of crystalline, nanoporous materials that are recognized for their tunability. While some MOFs demonstrate flexibility, this characteristic can pose challenges in achieving precise pore control or establishing permanent porosity. Specifically, MIL-88B is notable for its high flexibility, as it is constructed from metal trimer clusters and two- dimensional linkers (2DLs) featuring planar, aromatic cores, allowing significant structural changes. In this study, we synthesized two new MOFs, NU-2010 and NU-2011, which are structurally analogous to MIL-88B but incorporate ditopic three-dimensional linkers (3DLs) with sterically bulky cores and higher symmetry. Our aim was to investigate whether the introduction of 3DLs could mitigate the flexibility observed in MIL-88B. We employed a combination of single-crystal and powder X-ray diffraction techniques to assess the flexibility of MIL-88B, NU-2010, and NU-2011 under various conditions, including thermal activation, solvent exchange, and temperature changes. Our findings indicate that incorporating 3DLs significantly reduces the framework flexibility in NU-2010 and NU-2011 relative to MIL-88B