Preparation of 2,3-Dibromo-1H-indenes and Tetrabromodihydro-s-indacenes as Synthetic Building Blocks.

The acid-induced intramolecular cyclization of 1,1-disubstituted 3-aryl-2,3-dibromoallylalcohols affords 2,3-dibromo-1H-indene derivatives. This method is also applicable to the preparation of tetrabromodihydro-s-indacenes. The thus obtained multi-brominated compounds can serve as versatile synthetic building blocks to obtain a variety of indene and indacene derivatives, as demonstrated by the synthesis of dialkylmethylene-bridged oligo(phenylenevinylene)s, which feature attractive photophysical properties.

Photocatalytic and electrocatalytic hydrogen production using nickel complexes supported by hemilabile and non-innocent ligands.

Nickel complexes with non-innocent ligands generated by one-electron reduction of octahedral Schiff base nickel(ii) complexes with hemilabile ligands exhibited excellent catalytic activities of over 5000 TONs through a metal-ligand cooperation mechanism for hydrogen evolution from water under visible light irradiation.

Photooxidation Reactions of Cyclometalated Palladium(II) and Platinum(II) Complexes.

New C,N,S-cyclometalated palladium(II) and platinum(II) complexes have been synthesized and their structural, electrochemical, and photochemical properties examined. The blue color of these complexes in solution changed to yellow under visible-light irradiation. By measurement of the absorption spectra for quantifying changes in color, isosbestic points for each complex clearly indicated the presence of only two species responsible for the change of color. X-ray analysis revealed that the visible-light-induced yellow species were S-oxygenated sulfinato complexes. Photosensitized generation of singlet oxygen (1O2) was confirmed by the direct detection of singlet oxygen luminescence at 1275 nm. The present cyclometalated palladium(II) and platinum(II) complexes are efficient photosensitizers of singlet oxygen, which rapidly reacts with coordinating sulfur atoms.

Molecular Design of a Chiral Brønsted Acid with Two Different Acidic Sites: Regio-, Diastereo-, and Enantioselective Hetero-Diels-Alder Reaction of Azopyridinecarboxylate with Amidodienes Catalyzed by Chiral Carboxylic Acid-Monophosphoric Acid.

A chiral Brønsted acid containing two different acidic sites, chiral carboxylic acid-monophosphoric acid 1a, was designed to be a new and effective concept in catalytic asymmetric hetero-Diels-Alder reactions of azopyridinecarboxylate with amidodienes. The multipoint hydrogen-bonding interactions among the carboxylic acid, monophosphoric acid, azopyridinecarboxylate, and amidodiene achieved high catalytic and chiral efficiency, producing substituted 1,2,3,6-tetrahydropyridazines with excellent stereocontrol in a single step. This constitutes the first example of regio-, diastereo-, and enantioselective azo-hetero-Diels-Alder reactions by chiral Brønsted acid catalysis.

Self-assembled construction of a sheet-type coordination polymer bearing cationic M2L4 cages: creation of channel-like space for removal of ClO4(-) and NO3(-) from aqueous solutions.

Treatment of CuCl2 with a bis-benzimidazole-type ligand, p-bbiteb, afforded a new 2D coordination polymer bearing cationic Cu2L4 cages on the sheet framework. The regular arrangement of the cages created channel-like space for anions. The compound removed ClO4(-) and NO3(-) from aqueous solutions by exchange with Cl(-) in the channels.

Efficient removal of perchlorate ion from water by a water-insoluble M2L4 type compound.

Reaction of CuSO4·5H2O with 1,3-bis(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (m-bbitrb) provides a new positively charged M2L4 type molecule, [SO4⊂Cu2(m-bbitrb)4]SO4. This compound includes SO4(2-) inside and outside the cationic cage. Despite this compound being insoluble in water, it shows highly efficient perchlorate removal activity from water by the exchange with SO4(2-) outside the cage.

Two new coordination polymers, a trinuclear metal complex and their interconversion depending on the solvent.

Two new 1-D coordination polymers and a discrete trinuclear complex with a double-ring framework were synthesized and structurally characterized. The unique irreversible conversion from one of the 1-D coordination polymers to the trinuclear complex by contact with MeCN is described.

Biomimic O2 activation hydroxylates a meso-carbon of the porphyrin ring regioselectively under mild conditions.

The reaction site of the Co(II) porphyrin created by an amide group and coordinating 1,2-dimethylimidazole at the fifth site activated an O2 molecule, and then hydroxylated the meso-carbon of the ligand. The biomimic O2 activation under mild conditions is described.

Solvent-soluble coordination polymer that reconstructs cyclic frameworks that trap a kinetically labile [Cu(CO3)2]2- unit.

A new 2D coordination polymer consisting of Cu(II) ions, bis-imidazole-type ligands, and CO3(2-) was prepared. This compound converted to new pentanuclear complexes with cyclic frameworks, which trapped a kinetically labile [Cu(CO3)2](2-) unit, by recrystallization from MeOH/Et2O or EtOH/Et2O.

Syntheses and characterization of new nickel coordination polymers with 4,4'-dipyridylsulfide. Dynamic rearrangements of one-dimensional chains responding to external stimuli: temperature variation and guest releases/re-inclusions.

Crystal structures and dynamic rearrangements of one-dimensional coordination polymers with 4,4'-dipyridylsulfide (dps) have been studied. Reaction of Ni(NO(3))(2)·6H(2)O with dps in EtOH yielded [Ni(dps)(2)(NO(3))(2)] ·EtOH (1), which had channels filled with guest EtOH molecules among the four Ni(dps)(2) chains. This coordination polymer reversibly transformed the channel structure responding to temperature variations. Immersion of 1 in m-xylene released guest EtOH molecules to yield a guest-free coordination polymer [Ni(dps)(2)(NO(3))(2)] (2a), which was also obtained by treatment of Ni(NO(3))(2)·6H(2)O with dps in MeOH. On the other hand, removal of the guest molecules from 1 upon heating at 130 °C under reduced pressure produced a guest-free coordination polymer [Ni(dps)(2)(NO(3))(2)] (2b). Although the 2a and 2b guest-free coordination polymers have the same formula, they showed differences in the assembled structures of the one-dimensional chains. Exposure of 2b to EtOH vapor reproduced 1, while 2a did not convert to 1 in a similar reaction. Reaction of Ni(NO(3))(2)·6H(2)O with dps in acetone provided [Ni(dps)(NO(3))(2)(H(2)O)] ·Me(2)CO (4) with no channel structure. When MeOH or acetone was used as a reaction solvent, the [Ni(dps)(2)(NO(3))(2)] · (guest molecule) type coordination polymer, which was observed in 1, was not formed. Nevertheless, the reaction of Ni(NO(3))(2)·6H(2)O with dps in MeOH/acetone mixed solution produced [Ni(dps)(2)(NO(3))(2)]·0.5(MeOH·acetone) (5), which has an isostructural Ni-dps framework to 1.