Hydrogen‐Bond and Metal–Ligand Coordination Bond Hybrid Supramolecular Capsules: Identification of Hemicapsular Intermediate and Dual Control of Guest Exchange Dynamics

Hybrid supramolecular capsules self‐assemble by simultaneously forming hydrogen and metal–ligand coordination bonds on mixing a C₂‐symmetrical cavitand (calix[4]resorcinarene‐based cavitands with ureide and terminal 4‐pyridyl units) with platinum or palladium complexes ([Pt(OTf)₂] or [Pd(OTf)₂] with chelating bisphosphines) in 1:1 ratio. Hemicapsular assemblies formed in the presence of excess amounts of cavitand relative to the platinum or palladium complexes are identified as intermediates in the above self‐assembly process by 2D‐NOESY spectroscopy. External‐anion‐assisted encapsulation of a neutral guest, 4,4′‐diiodobiphenyl, inside the hybrid supramolecular capsules accompanied conformational changes in the hydrogen‐bonding moieties. The in/out exchange ratio of the encapsulated guest depends on the bite angle of the bisphosphine ligand. Addition of DMSO accelerates guest exchange by weakening the hydrogen bonds in the encapsulation complex. Therefore, variations in the structure of the metal complex and amount of polar solvent exert dual control on the dynamics of the guest exchange.     

Molecular Structure and Mutual Recognition Between Host and Guest Molecules Found in the Crystal Structures of Oxacalix[4]arenes Complexed with Xylene Isomers

The crystal structures of two complexes of oxacalix[4]arene derivatives {p-isopropyl-dihomooxacalix[4]arene (IOC-4)and p-tert-butyldihomooxacalix[4]arene(BOC-4)} with xylene isomers have been determined byX-ray diffraction method. Furthermore, in order toestimate the strength of the mutual interactionsbetween host (IOC-4 and BOC-4) and guest (o-, m-and p-xylene), the heat of complex formation forthe IOC-4 : xylene complexes was calculated using a molecularorbital method, and a differential scanningcalorimetric investigation was performed forthe BOC-4 : xylene complexes.     

Armillariols A to C from the culture broth of Armillaria sp.

Three novel compounds were isolated from the culture broth of Armillaria sp. Their structures were elucidated mainly by spectroscopic data analyses. All the compounds regulated hypocotyl and root growth of lettuce.     

Convenient use of ortho-formylphenyl thioglycoside for regioselective conjugation with glycosyl acceptors towards regioselective 1,2-cis-glycosylation

A facile methodology is proposed for regioselective conjugation between glycosyl donors and acceptors towards the development of regioselective 1,2-cis-glycosylation method. ortho-Formylphenyl 1-thio-β-d-galactopyranoside was regioselectively tethered to methyl α-d-glucopyranoside under acidic condition to furnish an 4,6-O-arylidene acetal-linked conjugate. This conjugate can be readily converted to an ether-linked 4-O- or 6-O-derivative by regioselective cleavage of the acetal ring. In the glycosylation reaction, the ether-linked 4-OH conjugate was found to show excellent 1,2-cis selectivity via an intramolecular 1,9-transfer.     

Water adsorption-desorption isotherms of two-dimensional hexagonal mesoporous silica around freezing point

Zr-doped mesoporous silica with a diameter of approximately 3.8 nm was synthesized via an evaporation-induced self-assembly process, and the adsorption-desorption isotherms of water vapor were measured in the temperature range of 263-298 K. The measured adsorption-desorption isotherms below 273 K indicated that water confined in the mesopores did not freeze at any relative pressure. All isotherms had a steep curve, resulting from capillary condensation/evaporation, and a pronounced hysteresis. The hysteresis loop, which is associated with a delayed adsorption process, increased with a decrease in temperature. Furthermore, the curvature radius where capillary evaporation/condensation occurs was evaluated by the combined Kelvin and Gibbs-Tolman-Koening-Buff (GTKB) equations for the modification of the interfacial tension due to the interfacial curvature. The thickness of the water adsorption layer for capillary condensation was slightly larger, whereas that for capillary evaporation was slightly smaller than 0.7 nm.     

Coadsorption of NO and other small gases (H2 and CO) on polycrystalline rhodium surface

The coadsorption of NO and other small gases (H₂ and CO) on a polycrystalline Rh filament has been studied by thermal desorption mass spectroscopy, using ¹⁵NO. The sample was exposed to a mixture of nitric oxide and other gases with various concentrations of ¹⁵NO at room temperature. It is indicated that NO, CO and H₂ coadsorbs on the rhodium surface, and NO desorbs as N₂ and O₂. NO is adsorbed mainly in the dissociation at lower coverage and molecular adsorption becomes dominant at higher coverage. But the amount of desorbed O₂ was very small. The chemisorption of CO is affected by the chemisorbed NO. Thermal desorption of hydrogen is detected when the value of P_15NO/P_CO is very small. The hydrogen adsorbed on the rhodium surface is replaced by NO with a longer exposure time.     

On certain polylogarithmic double series

In this paper, we study certain polylogarithmic double series

Iridium-catalyzed borylation of benzene with diboron. Theoretical elucidation of catalytic cycle including unusual iridium(v) intermediate

Iridium-catalyzed borylation of benzene with diboron was theoretically investigated with the DFT method, where an iridium(I) boryl complex, Ir(Beg)(NN) 1, and an iridium(III) tris(boryl) complex, Ir(Beg)(3)(NN) 14, (eg (ethyleneglycolato) = -OCH(2)CH(2)O-, NN = HN=CHCH=NH (diim) or 2,2'-bipyridine (bpy)) were adopted as models of active species and B(2)(eg)(2) was adopted as a model of bis(pinacolato)diboron (pinacolato = -OCMe(2)CMe(2)O-). Oxidative addition of a benzene C-H sigma-bond to 1 takes place with an activation barrier (E(a)) of 11.2 kcal/mol, followed by reductive elimination of phenylborane, Ph-Beg, from Ir(Beg)(H)(Ph)(diim) with an activation barrier of 15.6 kcal/mol. Though the oxidative addition and the reductive elimination occur with moderate activation barriers, B(2)(eg)(2) much more easily reacts with 1 to afford 14 than does benzene, of which the activation barrier is very small (2.9 kcal/mol). Oxidative addition of the benzene C-H sigma-bond to 14 occurs with a moderate activation barrier of 24.2 kcal/mol to afford an unusual seven-coordinate iridium(V) complex, Ir(H)(Ph)(Beg)(3)(bpy) 16. From this complex, phenylborane Ph-Beg is produced through the reductive elimination with concomitant formation of IrH(Beg)(2)(bpy) 17, where the activation barrier is 4.9 kcal/mol. Complex 17 further reacts with diboron to form Ir(H)(Beg)(4)(bpy) (E(a) = 8.0 kcal/mol), followed by the reductive elimination of borane H-Beg (E(a) = 2.6 kcal/mol) to regenerate Ir(Beg)(3)(bpy), when diboron exists in excess in the reaction solution. After consumption of diboron, IrH(Beg)(2)(bpy) reacts with borane, H-Beg, to form Ir(H)(2)(Beg)(3) (E(a) = 21.3 kcal/mol) followed by the reductive elimination of H(2), to regenerate Ir(Beg)(3)(bpy) with concomitant formation of H(2). Formation of the iridium(III) tris(boryl) complex 14 from IrCl(diim) and diboron was also theoretically investigated; IrCl(diim) undergoes two steps of oxidative addition of diboron to afford a seven-coordinate iridium(V) complex, IrCl(Beg)(4)(NN), from which the reductive elimination of Cl-Beg takes place easily to afford 14. From these results, it should be clearly concluded that the iridium(III) tris(boryl) complex is an active species and an unusual iridium(V) species is involved as a key intermediate in the reaction. Detailed discussion is presented on the full catalytic cycle and the importance of a seven-coordinate iridium(V) intermediate.     

HEMATOPORPHYRIN DERIVATIVE UPTAKE BY ATHEROMA IN ATHEROSCLEROTIC RABBITS: THE SPECTRA OF FLUORESCENCE FROM HEMATOPORPHYRIN DERIVATIVE DEMONSTRATED BY AN EXCIMER DYE LASER

Abstract A new diagnostic and therapeutic endoscopic system consisting of an excimer pulse dye laser is presented. This report demonstrates the accumulation of hematoporphyrin derivative (HpD) in atheroma as shown by the fluorescence of HpD using this equipment. Atheroma was induced in the aorta of WHHL (Watanabe heritable hyperlipidemic) rabbits, 5 mg kg⁻¹ HpD was injected intravenously and the rabbits were sacrificed 24 h later. The aorta was dissected and the localization of HpD was examined. Characteristic peaks of the fluorescence of HpD at 630, 665 and 690 nm wavelength were detected in the atheromatous lesion. However, in the fatty plaque, the emission peak at 630 nm was lower and the 665 nm peak faded away. No fluorescence with peaks was detected in the normal area. The ratio of fluorescence intensity in atheroma, border zones and normal areas was 10.4 : 5.0 : 1.0. On normal rabbits made atherosclerotic by diet and balloon damage, an ultra thin endoscopic catheter was inserted from the descending aorta of atherosclerotic rabbits under anesthesia. Essentially the same data was obtained by these studies in vivo as was obtained in the in vitro studies. The above data suggests the possibility of future applications of this equipment for diagnosis of atheroma.     

Packing motifs and magneto-structural correlations in crystal structures of metallo-tetrakis(1,2,5-thiadiazole)porphyrazine series, MTTDPz (M=H2, Fe, Co, Ni, Cu, Zn)

Single crystals of tetrakis(thiadiazole)porphyrazine and the corresponding metal(II) derivatives, MTTDPz (M=H2, Fe, Co, Ni, Cu, and Zn) were grown by sublimation under reduced pressure with continuous N2 gas flow. Their structures, obtained by X-ray crystallographic analysis, depend significantly on the central metal ion, and the M=Ni and Cu derivatives exhibit polymorphism. They can be classified into three forms, alpha, beta, and gamma. The alpha form (M=H2, Ni, and Cu) is composed of two-dimensional hexagonal close packing formed by side-by-side contacts between thiadiazole rings, whereas the beta form (M=Fe, Co, and Zn) crystallizes into a one-dimensional coordination polymer. The gamma form (M=Ni and Cu) consists of a ladder structure caused by pi stacking, similar to the beta form of phthalocyanine, and by side-by-side contacts between thiadiazole rings. Although the crystal structures of the MTTDPz series exhibited multi-dimensional network structures, magnetic measurements revealed relatively weak exchange interactions, probably reflecting the long distances between the metal ions.