Electrochemical and phosphorescent properties of new Ir(III) complexes coordinated by various bipyridine derivatives.

Four useful polypyridine iridium(III) complexes in the form of [IrCl2L2]+ were prepared and their spectroscopic and electrochemical properties as well as X-ray crystallography were investigated. The ligands used were L = 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-diphenyl-2,2'-bipyridine, 1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 2,2'-biquinoline. Synthetic methods were developed by a sequential ligand-replacement, which occurred in the reaction vessel using a microwave oven. All complexes showed that LUMOs are based on the pi-system contribution of the polypyridine ligand for [IrCl2(bpy)2]+, [IrCl2(dmbpy)2]+, [IrCl2(dpbpy)2]+, [IrCl2(phen)2]+, [IrCl2(dpphen)2]+ and [IrCl2(bqn)2]+. The HOMOs are also localized on the polypyridine ligand in the iridium complexes. It was found that [IrCl2L2]+ emits intense phosphorescence at room temperature. In particular, the use of dpbpy as ancillary ligands extends the lifetime (660 ns) of the 3(pi-pi*) excited states of Ir(III) polypyridine complexes. The complex [IrCl2(bqn)2]+ with electron acceptor substituents shows a large red-shift to 622 nm. It is noticed that iridium polypyridine complexes show intense emissions at various colors, such as yellow for [IrCl2(dmbpy)2]+ and red for [IrCl2(bqn)2]+ which can be applied to photosensitizers. The spectroscopic and electrochemical details are also reported herein.     

Electrochemical and luminescent properties of new mononuclear ruthenium(II) and binuclear iridium(III)-ruthenium(II) terpyridine complexes.

Hexafluorophosphate salts of mononuclear complexes [Ru(II)Cl(L)(terpy)]+ (L = dmbpy (1); dpbpy (2), sambpy (3), and dpp (7), and binuclear complexes [Ru(II)2Cl2(dpp)(terpy)2]2+ (8) and [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+ (9) were prepared and characterized. Abbreviations of the ligands are bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, dpbpy = 4,4'-diphenyl-2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, sambpy = 4,4'-bis((S)-(+)-alpha-1-phenylethylamido)-2,2'-bipyridine, and terpy = 2,2':6',2'-terpyridine. The absorption spectra of 8 and 9 are dominated by ligand-centered bands in the UV region and by metal-to-ligand charge-transfer bands in the visible region. The details of their spectroscopic and electrochemical properties were investigated. In both binuclear complexes, it has been found that the HOMO is based on the Ru metal, and LUMO is dpp-based. [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+, indicating intense emission at room temperature, and a lifetime of 154 ns. The long lifetime of this bimetallic chromophore makes it a useful component in the design of supramolecular complexes.     

Emergent radiation from an inhomogeneous,plane-parallel planetary atmosphere calculated by using the “adding” method

The method of computation of diffuse reflection radiation from an inhomogeneous, plane-parallel planetary atmosphere is discussed by using the “adding” method. If the atmosphere is simulated by a number of homogeneous sublayers, the diffusely reflected radiation from the atmosphere can be expressed in terms of the reflection and the transmission matrices of radiation of sublayers. This method can be easily extended to the problem including aerosol distribution with height variation. Polarization is also included.     

Relative rotational motion between alpha-Cyclodextrin Derivatives and a stiff axle molecule

Novel [2]rotaxanes bearing alpha-cyclodextrin (alpha-CD) derivatives and a diphenylacetylene axis molecule with trinitrobenzene as a bulky stopper have been prepared to investigate the relative rotary movement of a ring relative to an axis molecule and that of an axis molecule in a ring by NMR techniques. [2]Rotaxanes 2 and 3 were composed of alpha-CD derivatives (2: 6-phenyl-amide-alpha-CD; 3: 6-stilbene-amide-alpha-CD). The protons of alpha-CDs in rotaxanes were thoroughly assigned by the two-dimensional NMR techniques (TOCSY, COSY, ROESY, HMQC, and HMBC). The protons of alpha-CD in rotaxane 1 did not show splitting, whereas the resonance peak shifts and splitting for the corresponding protons of alpha-CD derivatives in rotaxanes 2 and 3 were observed by the shielding and deshielding effects from a diphenylacetylene axis molecule. The splitting of resonance peaks was closely related to the rotary movements of alpha-CDs and an axis molecule. We supposed that alpha-CD in rotaxane 1 rotates freely around a diphenylacetylene axis molecule, and vice versa, whereas the rotary movement of alpha-CD derivatives and the axis molecules of rotaxanes 2 and 3 were restricted by the steric repulsion between the substituent group of alpha-CD and the stopper group of an axis molecule. To estimate the relative rotary movement of CDs and an axis molecule in rotaxanes, the rotational correlation time (tauc) of rotaxanes was measured by 13C NMR. The results indicate that the corresponding rotary movement of the modified alpha-CD and the axis molecules in rotaxanes 2 and 3 depends on the size of the substituent group.     

An artificial molecular chaperone: poly-pseudo-rotaxane with an extensible axle

Poly-pseudo-rotaxanes CDs contains as a subset 1 (CDs; cyclodextrins, 1; poly(delta-valerolactone) having single beta-CD at the end of the polymer chain) initiate polymerization of delta-valerolactone (delta-VL) in the solid state when CDs (alpha-CD, beta-CD, and 2,6-di-O-methyl-beta-CD) are threaded onto the polymer chain. 1 without threaded CDs did not show any polymerization ability for delta-VL. An adamantane molecule (Ad) inhibited the polymerization ability of CDs contains as a subset 1 for delta-VL, indicating that beta-CD at the end of CDs contains as a subset 1 could not bind delta-VL because the beta-CD cavity was occupied by Ad. It should be noted that the insertion reaction and the polymerization took place inside the beta-CD cavity at the end of CDs contains as a subset 1 and that the formation of poly-pseudo-rotaxane is necessary for the initiation of delta-VL. The structures of beta-CD contains as a subset 1 and 1 were characterized by powder X-ray diffraction measurements and solid-state NMR spectroscopies. The polymer chain of beta-CD contains as a subset 1 was found to elongate in the solid state, whereas the polymer chain of 1 formed a random coil conformation. 1 was deactivated for the polymerization by blocking the active cavity of beta-CD with the polymer chain. CDs threaded onto 1 are immune to the initiation of delta-VL directly but have an essential role to fold the polymer chain in a proper way as an artificial chaperone.     

Measurement of krypton-85 in the atmosphere with a portable apparatus

A portable apparatus was developed for the rapid collection, separation and counting of krypton-85 in the environmental air samples. The apparatus consists of a molecular sieve trap for the elimination of H₂O and CO₂, a charcoal trap for the collection of krypton, a chromatographic column for the isolation of krypton in the air sample and a vial for the dissolution of krypton in the scintillation solution. With this apparatus, krypton can be collected from half a cubic meter of air with 94% recovery in about 3 hrs. The measurements of krypton-85 have been done several times in Fukuoka area between the periods Jan. 30, 1981 and Dec. 9, 1981. And then, the krypton-85 concentration was found to be approximately 21 pCi/m³ air. The results were compared with those obtained by foregin investigators.     

HYDROGEN PEROXIDE MEDIATES UV-INDUCED IMPAIRMENT OF ANTIGEN PRESENTATION IN A MURINE EPIDERMAL-DERIVED DENDRITIC CELL LINE

Abstract— Ultraviolet-B (290–320 nm) radiation is known to impair the antigen-presenting cell (APC) function of Langerhans cells (LC), skin-specific members of the dendritic cell (DC) family. We sought to address mechanisms of this effect, focusing on the role played by hydrogen peroxide. For this purpose, we used a newly established murine DC line, XS52, which resembles epidermal LC in several respects. The APC capacity of XS52 cells, using two different CD4* T cell clones as responders, was inhibited significantly (>50%) by exposure to UV radiation (unfiltered FS20 sunlamps) at relatively small fluences (50–100 J/m²). Ultraviolet radiation also inhibited growth factor-dependent proliferation of XS52 cells. On the other hand, cell surface phenotype was relatively well preserved after irradiation; expression levels of B7-1 and B7-2 were reduced slightly, while other molecules ( e.g. Ia, CD54, CD1 la and CD18) were not affected. With respect to the role played by hydrogen peroxide, pretreatment with purified catalase (900 U/mL) prevented UV-induced inhibition of APC function. Short-term exposure to 3 miM H₂0₂ or f-butyl H₂0₂ mimicked UV radiation by inhibiting APC function. Finally, intrinsic catalase activity was substantially lower in XS52 cells compared with Pam 212 keratinocytes. These results indicate that the generation of hydrogen peroxide alone is sufficient to produce some, but not all, of the deleterious effects of UV radiation on DC derived from the skin.