Syntheses and skeletal transformations of NCNH- and NCN-bridged tetrairidium(III) cages

The diiridium complex [Cp*IrCl2]2 (Cp* = eta5-C5Me5) reacts with 2 equiv of Na(NCNH) at room temperature to afford the 16-membered macrocyclic tetrairidium complex [Cp*IrCl(mu2-NCNH-N,N')]4 (1a). Treatment of 1a with 4 equiv of triethylamine at room temperature leads to the formation of the "C3-elongated cubane-like" tetrairidium complex [Cp*Ir(mu3-NCN-N,N,N')3(IrCp*)3(mu3-NCN-N,N,N)] (2) as the major product, which is further converted into the cubane-type complex [Cp*Ir(mu3-NCN-N,N,N)]4 (3) on refluxing in p-xylene. The molecular structures of [Cp*IrI(mu3-NCNH-N,N')]4.C7H8 (1b.C7H8), 2.0.5C7H8, and 3 have been determined by X-ray analyses.     

Structural order in perfluoropentacene thin films and heterostructures with pentacene

Synchrotron x-ray diffraction reciprocal space mapping was performed on perfluoropentacene (PFP) thin films on SiO2 in order to determine the crystal structure of a novel, substrate-induced thin film phase to be monoclinic with unit cell parameters of a = 15.76 +/- 0.02 A, b = 4.51 +/- 0.02 A, c = 11.48 +/- 0.02 A, and beta = 90.4 +/- 0.1 degrees . Moreover, layered and co-deposited heterostructures of PFP and pentacene (P) were investigated by specular and grazing-incidence x-ray diffraction, atomic force microscopy, and Fourier-transform infrared spectroscopy. For a ca. three-monolayers-thick PFP film grown on a P underlayer, slightly increased lattice spacing was found. In contrast, co-deposited P/PFP films form a new mixed-crystal structure with no detectable degree of phase separation. These results highlight the structural complexity of these technically relevant molecular heterojunctions for use in organic electronics.     

Triarylethene-based extended pi-systems: programmable synthesis and photophysical properties

[reaction: see text] On the basis of an efficient Pd-catalyzed triarylation to a vinylsilane platform, four types of structurally well-defined triarylethene-based extended pi-systems have been prepared very rapidly. From a compound library constructed by the present method, it was possible to find a number of interesting fluorescent materials, as well as interesting fluorescent properties such as aggregation-induced enhanced emission. A useful method for the rapid synthesis and property evaluation has also been developed.     

Ferromagnetic fluctuation and possible triplet superconductivity in NaxCoO2.yH2O: fluctuation-exchange study of the multiorbital Hubbard model

Spin and charge fluctuations and superconductivity in NaxCoO2.yH(2)O are studied based on a multiorbital Hubbard model. Tight-binding parameters are determined to reproduce the results of band calculations. By applying the fluctuation-exchange approximation, we show that the Hund's-rule coupling between the Co t(2g) orbitals causes ferromagnetic (FM) spin fluctuation. Triplet fy((y(2)-3x(2)))-wave and p-wave pairings are favored by this FM fluctuation on the hole-pocket band. We propose that, in NaxCoO2.yH(2)O, the Co t(2g) orbitals and interorbital Hund's-rule coupling play important roles on the triplet pairing, and this compound can be a first example of the triplet superconductor in which the orbital degrees of freedom play substantial roles.     

Syntheses of (−)-8-EPI-Swainsonine and (−)-1,8-DI-FPI-Swainsonine,Stereoisomers of Indolizidine Alkaloid,Swainsonine

Recently, we have completed a total synthesis of swainsonine (l), (1S,2S,8R,8aR)-1,2,8-trihydroxyoctahydroindolizine, which exhibits remarkable physiological effects such as an α-mannosidase inhibitory activity, an immunoregulating activity and so on. In order to elucidate a relationship between structures and physiological activities, a congener of swainsonine has been synthesized. In this communication, we wish to report a synthesis of (-)-8-epi-swainsonine (2) and (-)-1,8-di-epi-swainsonine (2) from methyl 3-acetamido-2-0-acetyl-4,6-0-benzylidene-3-deoxy-α-D-glucopyranoside (4) and methyl 3-acetamido-2-0-acetyl-3-deoxy-4,6-di-0-mesyl-α-glucopyranoside-(14), respectively.     

Synthesis and structures of heterobimetallic Ir2M (M=Pd, Pt) sulfido clusters and their catalytic activity for regioselective addition of alcohols to internal 1-aryl-1-alkynes

The heterobimetallic trinuclear sulfido clusters [(Cp*Ir)₂(μ₃-S)₂MCl₂] (M=Pd (3), Pt (4); Cp*=η⁵-C₅Me₅) were synthesized from the dinuclear hydrogensulfido complex [Cp*IrCl(μ-SH)₂IrCp*Cl] (2) and [MCl₂(COD)] (COD=cycloocta-1,5-diene), while the reaction of 2 with [Pd(PPh₃)₄] afforded the cationic trinuclear cluster [(Cp*Ir)₂(μ₃-S)₂PdCl(PPh₃)]Cl (5). Clusters 3 and 4 reacted with PPh₃ to give a series of mono and dicationic clusters including 5, while the dicationic clusters [(Cp*Ir)₂(μ₃-S)₂M(dppe)][BPh₄]₂ (M=Pd (9), Pt (10); DPPE=Ph₂PCH₂CH₂PPh₂) were obtained by the reaction with dppe followed by anion metathesis. The molecular structures of 5·CH₂Cl₂, 9·CH₃COCH₃, and 10·CH₃COCH₃ were determined by X-ray crystallography. Clusters 3 and 4 were found to catalyze the addition of alcohols to alkynes to give the corresponding acetals. Internal 1-aryl-1-alkynes were transformed by cluster 3 into the corresponding 2,2-dialkoxy-1-arylalkanes with high regioselectivity up to 99:1, while cluster 4 was a much less regioselective catalyst.     

A Chiral Synthesis of (+)-Pseudoconhydrine

(+)-Pseudoconhydrine, one of hemlock alkaloids, has been synthesized from methyl 2-acetamido-2,3,4-trideoxy-α-D-erythro-hexopyranoside by an eleven step reaction sequence. An intramolecular nucleophilic attack of the nitrogen atom on 2-acetamido-5-0-benzyl-2,3,4-trideoxy-6-0-tosyl-D-reythro-hexose diethyl di-thioacetal to the terminal tosyloxymethylene group proceeded smoothly and gave the desired disubstituted piperidine compound. A conversion of the thioacetal group into an aldehyde, a two-carbon elongation by Wittig olefination, and a successive hydro-genation completed the chiral synthesis of the title alkaloid.     

Supramolecular dye inclusion single crystals created from 2,3,6-trimethyl-β-cyclodextrin and porphyrins

In Nature, chromophoric groups play various roles, such as oxygen carriers, electron donors, light sensitizers, which are achieved in many cases by control of their aggregation modes in proteins. Host-guest chemistry between cyclodextrins and porphyrins has attracted great interest from supramolecular chemists because of their unique structures and functions that mimic those of proteins with chromophoric prosthetic groups. To mimic Nature's contrivances, the host-guest systems between cyclodextrins and porphyrins have frequently been studied. It is really surprising, however, that to date no detailed structural information of these complexes has been obtained from single-crystal analysis. In 2011, we reported the first successful isolation of a dye inclusion single crystal (DISC) between 2,3,6-trimethyl-β-cyclodextrin (TMβCD) and 5,10,15,20-tetrapyridylporphyrin (TPyP), and analyzed its X-ray crystal structure. The crystal structure revealed not only the real complex mode but also the attractive orientation of TPyP in the DISC. Herein, we present new strategies to prepare DISCs of TMβCD for several porphyrins and provide crystal structures, details of the complex modes, and optical properties. We believe that the present study has various important implications not only for the basic crystal analysis of inclusion complexes but also for potential applications that use these single crystals.