Photo-alignment Property of Azobenzene-containing Polyimide Films Swollen by Alkyl-amine

Photo-alignment efficiency of polyimide containing azobenzene in the backbone structure (Azo-PI) is significantly enhanced by exposing the precursor (polyamic acid: Azo-PAA) film to alkyl-amine vapor prior to photo-alignment. In this study, we have investigated the relationships between the alkyl-amine vapor treatment time, the swelling ratio of Azo-PAA films, and the photo-induced in-plane anisotropy. We found that: the Azo-PAA film swells on exposure to alkyl-amine vapor, and the swelling finally saturates; and the photo-induced in-plane anisotropy is correlated very closely with the swelling ratio. In addition, we pointed out the importance of the process order of alkyl-amine vapor treatment and photo-alignment.     

Molecular-level chiral discrimination and induction

The review describes the mechanism of chiral discrimination of racemic amines upon crystallization and the induction of chirality in organic reactions by using them as chiral auxiliaries. In order to form conglomerates, which can be resolved into the two enantiomers upon alternative seeding, both formation and packing of 2₁-columns are essentially very important. On the other hand, in order to achieve high efficiency in resolution through diastereomeric salt formation, which is the most practical method, one of a pair of diastereomeric salts derived from a racemic amine and an enantiomerically pure resolving agent should at least have two 2₁-columns and planar boundary surfaces in its crystal structure. On the basis of this knowledge, we developed several artificial chiral auxiliaries such as erythro-2-amino-1,2-diphenylethanol,cis-2-amino-1-acenaphthenol, andcis-2-amino-3,3-dimethyl-1-indanol. These were found to be very efficient chiral auxiliaries in asymmetric inductions: alkylation of chiral imines, catalytic borane-reduction, and alkylation of chiral N-acylated oxazolidinone.     

A topological isomer of ferrocene: Theoretical approach for transition metal complexes with conjugated all trans cyclodecapentaene

We demonstrate the ability of all-trans DPEN as a suitable ligand for transition metals by DFT computation [B3LYP/6-311+G(2d,p) and BP86 level]. The iron complex Fe(DPEN) is a unique topological isomer of ferrocene.     

Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation

A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)₂ (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.     

2,2′-Bipyridyl formation from 2-arylpyridines through bimetallic diyttrium intermediate

An alkylyttrium complex supported by an N,N′-bis(2,6-diisopropylphenyl)ethylenediamido ligand, (ArNCH₂CH₂NAr)Y(CH₂SiMe₃)(THF)₂ (1, Ar = 2,6-ⁱPr₂C₆H₃), activated an ortho-phenyl C–H bond of 2-phenylpyridine (2a) to form a (2-pyridylphenyl)yttrium complex (3a) containing a five-membered metallacycle. Subsequently, a unique C(sp²)–C(sp²) coupling of 2-phenylpyridine proceeded through a bimetallic yttrium intermediate, derived from an intramolecular shift of the yttrium center to an ortho-position of the pyridine ring in 3a, to yield a bimetallic yttrium complex (4a) bridged by two-electron reduced 6,6′-diphenyl-2,2′-bipyridyl. Aryl substituents at the ortho-position of the pyridine ring were key in order to destabilize the μ,κ²-(C,N)-pyridyldiyttrium intermediate prior to the C(sp²)–C(sp²) bond formation.     

One‐Step Borylation of 1,3‐Diaryloxybenzenes Towards Efficient Materials for Organic Light‐Emitting Diodes

The development of a one‐step borylation of 1,3‐diaryloxybenzenes, yielding novel boron‐containing polycyclic aromatic compounds, is reported. The resulting boron‐containing compounds possess high singlet‐triplet excitation energies as a result of localized frontier molecular orbitals induced by boron and oxygen. Using these compounds as a host material, we successfully prepared phosphorescent organic light‐emitting diodes exhibiting high efficiency and adequate lifetimes. Moreover, using the present one‐step borylation, we succeeded in the synthesis of an efficient, thermally activated delayed fluorescence emitter and boron‐fused benzo[6]helicene.     

Construction of carbocyclic ring of indoles using ruthenium-catalyzed ring-closing olefin metathesis

The selective synthesis of substituted indoles was achieved by the ring-closing olefin metathesis (RCM)/elimination sequence or the RCM/tautomerization sequence of functionalized pyrrole precursors. The RCM/elimination sequence was also applied to double ring closure to yield a substituted carbazole.     

Oxidant-free direct coupling of internal alkynes and 2-alkylpyridine via double C-H activations by alkylhafnium complexes

We have developed a novel oxidant-free direct cross-coupling reaction of 2,6-lutidine and internal alkynes leading to five-membered carbocyclic compounds mediated by nonmetallocene cationic hafnium alkyl complexes. Mechanistic studies of the coupling reaction showed that the reaction begins with C(sp(3))-H bond activation via σ-bond metathesis, after which the coordinatively unsaturated hafnium center mediates further insertion, migration, and β-H elimination reactions to give five-membered carbocycles from readily available substrates.     

Interaction of ferrocene moieties across a square Pt4 unit: synthesis, characterization, and electrochemical properties of carboxylate-bridged bimetallic Pt4Fe(n) (n = 2, 3, and 4) complexes

Four types of square Pt(4) complexes bearing two or more ferrocenecarboxylate ligands--[Pt(4)(μ-OCOCH(3))(4)(μ-OCOC(5)H(4)FeCp)(4)] (6); [Pt(4)(μ-OCOCH(3))(4)(μ-OCOC(5)H(4)FeCp)(3)(μ-ArNCHNAr)], where ArNCHNAr = N,N'-diarylformamidinate) (7); trans-[Pt(4)(μ-OCOCH(3))(4)(μ-OCOC(5)H(4)FeCp)(2)(μ-ArNCHNAr)(2)] (8); and cis-[Pt(4)(μ-OCOCH(3))(4)(μ-OCOC(5)H(4)FeCp)(2)(κ(4)-N(4)-DArBp)(2)], where DArBp = 1,3-bis(benzamidinato)propane (9)--were successfully prepared via reactions of [FeCp(η(5)-C(5)H(4)COOH)] (5) with the corresponding square Pt(4) complexes, which have labile in-plane acetate ligands. The newly prepared Pt(4) complexes (6-9) with ferrocene moieties as pendants were characterized by nuclear magnetic resonance (NMR) spectroscopy, mass spectroscopy (MS), combustion analyses, and single-crystal X-ray analysis for 6, some of the trans-Pt(4)Fe(2)8, and the cis-Pt(4)Fe(2) complexes 9. Weak interactions between two ferrocene moieties across the Pt(4) core, providing ΔE(1/2) values and K(c) constants, were revealed electrochemically, using cyclic and differential-pulse voltammetry in dichloromethane containing [(n)Bu(4)N][BAr(F)(4)] (where Ar(F) = C(6)H(3)(CF(3))(2)-3,5), which was a better supporting electrolyte for such an interaction than [(n)Bu(4)N][PF(6)].