A wide array of natural resveratrol dimers was prepared by the regioselective oxidative coupling reaction of 3,5-di-(tertbutyl)resveratrol using several types of metal oxidants (Ag 2 O, Ag 2 CO 3 , MnO 2 , and FeCl 3 ·6H 2 O) in different solvent systems (benzene-acetone and dichloromethane). Subsequent debutylation of these coupling products resulted in racemic pallidol and ampelosin F.
Mono-, Tetra-and octanuclear transition metal complexes of in situ generated schiff base ligands containing up to 12 coordinating atoms: syntheses, structures and magnetism{ By the reaction of an alkoxyl containing tetraamine, 1,3-bis[(2-aminoethyl)amino]-2-propanol, with various aldehydes, O-vanillin and 2,6-diformyl-4-cresol, in the presence of various metal cations, four novel complexes were synthesized and structurally characterized. Complexes [CoHL 1 ](ClO 4 )?2MeOH(1) and [NiH 2 L 2 ](ClO 4 ) 2 ?0.5MeOH (2) have mononuclear structures, with the linear di-Schiff base ligand (HL 1 ) 22 and mono-Schiff base ligand H 2 L 2 generated from in situ reactions under various pH conditions. In complexes [Ni 4 L 3 (SCN) 3 (MeOH)]Cl?2.5MeOH (3), and [Cu 8 (H 2 L 3 ) 2 (OH) 4 (ClO 4 )](SCN) 6 (ClO 4 )?8H 2 O (4), an interesting 32-membered dodecadentate macrocyclic ligand H 4 L 3 comprising four Schiff base CLN double bonds was generated by a ''2+2'' type condensation reaction between the tetraamine and the dialdehyde. Complex 3 has a tetranuclear Ni 4 coordination structure with all 12 coordinating atoms of (L 3 ) 42 utilized for coordination, and the alkoxyl groups are deprotonated and coordinated in a bridging mode. Complex 4 exhibits an octanuclear Cu 8 coordination structure, with a ClO 4 2 bridging two tetranuclear [Cu 4 H 2 L 3 (OH) 2 ] 4+ moieties through four weak axial Cu-O coordination bonds. In complex 4, only 10 coordinating atoms of (L 3 ) 42 are utilized for coordination, with the two alkoxyl groups left neutral and noncoordinated. It is noteworthy that H 4 L 3 has two long saturated chains in the molecule. Therefore, it has good flexibility and tends to have a nonplanar structure. Variable temperature magnetic data for 3 and 4 indicated the existence of antiferromagnetic interactions, which were discussed based on the structural results. { Electronic supplementary information (ESI) available: X-ray Crystallographic files (CIF format), selected bond lengths and angles for complexes and magnetic exchange pathways for 4. CCDC reference numbers 886465-886468. See
Single crystals of Ho2O3-doped Y2O3 stabilized ZrO2 (YSZ) with different Y2O3 and Ho2O3 contents were grown by the optical floating zone method. XRD and Raman spectra were measured and showed that crystal samples all had tetragonal structures. Measurements of positron annihilation lifetime spectra indicated that the increase in Y2O3 concentration led to the increases of defects and mean positron lifetime, which enhanced the scattering of light and reduced the luminous intensity and the quantum yield (QY) of the crystal. Under the excitation at 446 nm, photoluminescence (PL) spectra of Ho2O3-doped YSZ crystals showed emission peaks at 540, 551, 670, and 757 nm corresponding to Ho3+ transitions from 5S2, 5F4, 5F5, and 5I4 excited states to the 5I8 ground state, respectively. At low Ho2O3-doped concentrations (0.10–0.50 mol%), the overall emission intensity increased with Ho2O3 contents, reached the maximum value at 0.50 mol%, then decreased with higher Ho2O3 contents, probably as a result of increased non-radiative relaxation caused by increased interactions between Ho3+ ions. Quenching of the PL occurred at Ho2O3 concentrations > 0.5 mol% and due to the electric dipole–dipole interaction. The calculated chromaticity coordinates (CIE) were approximately (0.307, 0.683) and the color purity achieved 99.6%. The results showed that Ho2O3: YSZ crystals were suitable for green light-emitting devices.
In the title compound, C14H11BrN2O2, the mean planes of the two benzene rings are almost parallel to each other, making a dihedral angle of 4.09 (1)°. An intramolecular O—H⋯N hydrogen bond occurs. In the crystal, intermolecular O—H⋯N and C—H⋯O hydrogen bonds link the molecules into a chain-like supramolecular structure.
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