Extended Open-Chain Polyenides as Versatile Delocalized Anion Ligands for Metal Chain Clusters

Although small cyclic- and open-chain unsaturated hydrocarbon anions such as cyclopentadienide and open-chain pentadienide are used as the strongly electron-donating auxiliary ligands for metal complexes, more extended π-conjugated unsaturated hydrocarbon anions have rarely been used in coordination chemistry, despite their potential ability to serve as the multiply bridging π-ligands for metal clusters. This work reports isolation of metal chain clusters bearing the multi-dentate, open-chain extended unsaturated hydrocarbon anion ligands. The extended open-chain π-conjugated polyenyl ligands could effectively stabilize oxidized palladium chains, including an unprecedented [Pd₄]⁴⁺ chain.     

Multinuclear magnetic resonance studies of five silver(I) trinuclear pyrazolate complexes

Structural Chemistry - Experimental multinuclear determination of the chemical shifts, especially 15N and 109Ag, of five silver(I) trinuclear pyrazolate complexes, (PzAg)3, coupled with ZORA...     

Preparation of new photosensitive Nb2O5 gel films modified with benzoylacetone and properties of heat-treated films

In this study, in order to develop a new photosensitive gel film, Nb₂O₅ gel films including a chelate ring were prepared by the sol?Cgel method. Photosensitive and patterning properties of the gel films were investigated. Properties such as refractive index for annealed films were also evaluated. In the electronic absorption spectra of the gel films, the absorption peak assigned a chelate ring was observed at 353?nm, this peak intensity decreased by UV irradiation. From this result, the obtained gel films exhibit photosensitivity. Fine patterns (minimal width of about 2???m) could be fabricated. It was found that the value of refractive index reaches a maximum of 2.25 for the film heat-treated at 800?°C.     

Sigmatropic Rearrangements of Hypervalent‐Iodine‐Tethered Intermediates for the Synthesis of Biaryls

Metal‐free dehydrogenative couplings of aryliodanes with phenols to afford 2‐hydroxy‐2′‐iodobiaryls have been developed. This reaction proceeds through ligand exchange on the hypervalent iodine atom followed by a [3,3] sigmatropic rearrangement and with complete regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, enables the convenient conversion of iodoarenes into desirable biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π‐extended furans and a substituted [5]helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic, with C?C bond formation and I?O bond cleavage proceeding in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, renders the iodine atom more cationic and thus accelerates the sigmatropic rearrangement.     

Room‐Temperature Phosphorescence‐active Boronate Particles: Characterization and Ratiometric Afterglow‐sensing Behavior by Surface Grafting of Rhodamine B

We found that boronate particles ( BP ), as a self‐assembled system prepared by sequential dehydration of benzene‐1,4‐diboronic acid with pentaerythritol, showed greenish room‐temperature phosphorescence (RTP). This emission was observed in both solid and dispersion state in water. To understand the RTP properties, X‐ray crystallographic analysis, and density functional theory (DFT) and time‐dependent DFT at M06‐2X/6‐31G(d,p) level were performed using 3,9‐dibenzo‐2,4,8,10‐tetraoxa‐3,9‐diboraspiro[5.5]undecane ( 1 ) as a model compound. Our interest in functionalizing the RTP‐active particles led us to graft Rhodamine B onto their surface. The resulting system emitted a dual afterglow via a Förster‐type resonance energy transfer process from the BP in the excited triplet state to Rhodamine B acting as an acceptor fluorophore. This emission behavior was used for ratiometric afterglow sensing of water content in THF with a detection limit of 0.28 %, indicating that this study could pave the way for a new strategy for developing color‐variable afterglow chemosensors for various analytes.     

Iridium-Catalyzed Regio- and Enantioselective Hydroarylation of Alkenyl Ethers by Olefin Isomerization

Iridium-catalyzed hydroarylation of alkenyl ethers, such as allylic and homoallylic ethers, by C−H bond activation gave high yields of the corresponding addition products, where the aryl groups were selectively installed at the α-carbon atom to the alkoxy group. The reaction involves an isomerization of the alkenyl ethers into the corresponding 1-alkenyl ethers, which then undergo the regio- and enantioselective hydroarylation.