Organic solid photochromism by photoreduction mechanism: Polar aprotic viologen copolymers

Copolymers of vinyl viologens such as N-vinylbenzyl-N′-yalkyl and N-(γ-methyacryloyloxy)propyl-N′-propyl-4,4′-bipyridinium dihalides and polar aprotic comonomers such as N-vinyl-2-pyrrolidone (VP) and N,N-dimethylacrylamide (DMA) were prepared by the copolymerizations of vinyl viologens with DMA and the chemical modifications of VP copolymers containing reactive halogens. Copolymers containing various viologen anions such as Br^?, BF, SO, and I^? were also prepared by the anion exchange of copolymers containing Cl^?. The photocolor developments of these aprotic copolymers in the film state were completely reversible and faster than for the corresponding copolymers with protic comonomers such as acrylamide and 2-hydroxyethyl acrylate, all with characteristic absorption spectra attributable to single radical cations.     

Cellular uptake and photocytotoxicity of glycoconjugated porphyrins in HeLa cells

Thirty-two glycoconjugated porphyrins were synthesized by a modification of Lindsey method in the presence of Zn(OAc)(2).2H(2)O as a template. The Zn(2+) ion template strategy improved the yield about three-fold in the case of meta-substituted tetraphenylporphyrins. In addition, free-base porphyrins were obtained almost quantitatively by demetalation with 4 M HCl. Sixteen deacetylated glycoconjugated porphyrins were tested as candidate photodynamic therapy (PDT) drugs using HeLa cells. Most of the deacetylated glycoconjugated porphyrins showed higher cellular uptake than tetraphenylporphyrin tetrasulfonic acid (TPPS), and 5,10,15,20-tetrakis[4-(beta-D-arabinopyranosyloxy)phenyl]porphyrin (p-5d) in particular showed 18.5-fold higher uptake than TPPS. The photocytotoxicity of 5,10,15,20-tetrakis[4-(beta-D-glucopyranosyloxy)phenyl]porphyrin (p-5a), p-5d and TPPS was examined with HeLa cells, using a light dose of 16 J/cm(2). These photosensitizers had no cytotoxicity in the dark, but their photocytotoxicity increased in the order of TPPS < p-5a < p-5d. These results suggest p-5d is a good candidate for a PDT drug.     

SOLVENT EFFECT ON SPHEROIDENE IN NONPOLAR AND POLAR SOLUTIONS AND THE ENVIRONMENT OF SPHEROIDENE IN THE LIGHT-HARVESTING COMPLEXES OF Rhodobacter sphaeroides 2.4.1 AS REVEALED BY THE ENERGY OF THE 1Ag−→1Bu+ ABSORPTION AND THE FREQUENCIES OF THE VIBRONICALLY COUPLED C=C STRETCHING RAMAN LINES IN THE 1Ag− AND 1Bu− STATES

Abstract –The ¹A_g^?→¹B_u⁺ electronic absorption band and the vibronically coupled, C=C stretching Raman lines in the ¹A_g^? and 2¹A_g^? states were recorded for spheroidene free in nonpolar and polar solvents as well as for spheroidene bound to the LH1 and LH2 complexes of Rhodobacter sphaeroides 2.4.1. The ¹B_u⁺ energy exhibited a linear dependence on R(n) = (n² - 1)/(n²+ 2) in both nonpolar and polar solvents; the line for polar solvents had a gentler slope and crossed the line for nonpolar solvents at R(n) = 0.3. The above characteristic of polar solvents was ascribed to the electric field generated by fluctuation of the solvent permanent dipoles; it stabilizes the ¹B_u⁺ energy and reduces the polarizability of the solvent. The vibronically coupled, C=C stretching frequencies in the ¹A_g^? and 2¹A_g^? states [ν(A_g) and [ν(2A_g)] also showed similar dependence on R(n), which is explained in terms of vibronic coupling among the ¹A_g^?, 2¹A_g^? and 3¹A_g^? states. The environment of spheroidene in the LH2 and LH1 complexes was assessed on the basis of the ¹B_u⁺ energy and the ν(A_g) and [ν(2A_g) frequencies: Spheroidene in the LH2 complex is located in an environment with high polarizability, while spheroidene in the LH1 complex is located in an environment with lower polarizability.     

Zirconocene-catalyzed alkylative dimerization of 2-methylene-1,3-dithiane via a single electron transfer process to provide symmetrical vic-bis(dithiane)s

A mixture of tertiary alkyl halide and 2-methylene-1,3-dithiane was treated with butylmagnesium bromide in the presence of a catalytic amount of zirconocene dichloride. The reaction resulted in alkylative dimerization to yield the corresponding vic-bis(dithiane). The reaction would proceed as follows. A single electron transfer from low-valent zirconocene to alkyl halide would generate the corresponding alkyl radical. The radical adds to 2-methylene-1,3-dithiane to afford the corresponding radical stabilized by the two sulfur atoms. A couple of the stable radicals finally undergo dimerization.     

Second hyperpolarizability of phenalenyl radical system involving acetylene π-conjugated bridge

The static second hyperpolarizability (γ) of a singlet diradical system involving phenalenyl radicals linked with acetylene π-conjugated bridge, BPLE, is investigated as well as reference closed-shell systems, BPRY1 and BPRY2, by the hybrid density functional theory method. The γ value of BPLE with intermediate diradical character is shown to be about four times as large as that of BPRY1 with similar π-conjugation length and to be about twice as large as that of BPRY2 with longer π-conjugation length. This feature is in agreement with our prediction that the molecules with intermediate diradical characters enhance γ values compared to the closed-shell molecules.     

Fabrication of novel multilayered thin films based on inclusion complex formation between amylose derivatives and guest polymers

Novel types of layer-by-layer (LbL) assembly films were successfully fabricated onto a solid substrate through the inclusion complex formation between partially 2,3- O-methylated amyloses (MAs) and polytetrahydrofuran (PTHF). The formation of the LbL assembly films was confirmed by quartz crystal microbalance (QCM) analysis, atomic force microscopy (AFM) observation, and X-ray diffraction (XRD) measurement. The film formation was significantly affected by the methylation degree of amylose. When MAs with 8 and 20% methylation were used as hosts, the formation of LbL assembly films with PTHF was clearly observed. On the other hand, MAs with more than 33% methylation barely formed LbL assembly films with PTHF.     

Asymmetric total synthesis of (+)-curcutetraol and (+)-sydonol

The asymmetric total syntheses of (+)-curcutetraol and (+)-sydonol, phenolic bisabolane-type sesquiterpenoids having chiral tertiary alcohol moiety in the o-position of a phenol, were achieved in high enantiomeric excesses (99% ee). The chiral tertiary benzylic alcohol moiety of these compounds was constructed by an asymmetric synthesis using an easily available chiral aminal, (−)-(2R,5S)-2-methoxycarbonyl-3-phenyl-1,3-diazabicyclo[3.3.0]octane. The absolute configurations of both (+)-curcutetraol and (+)-sydonol have been assumed to be S-configuration based on the stereochemical course of the well established asymmetric synthesis used in the syntheses.     

Production of the neutron-rich hypernucleus 10LambdaLi in the (pi-,K+) double charge-exchange reaction

In order to produce a neutron-rich Lambda hypernucleus for the first time, we carried out an experiment by utilizing the (pi-,K+) double charge-exchange reaction on a 10B target. We observed the production of a 10LambdaLi hypernucleus. The cross section for the Lambda bound region was found to be 11.3+/-1.9 nb/sr with the 1.2 GeV/c incident momentum, which is compared with the 10LambdaB hypernucleus production cross section, 7.8+/-0.3 microb/sr, in the (pi+,K+) reaction with a 1.05 GeV/c incident momentum beam.     

Colorimetric detection of histidine in aqueous solution by Ni2+ complex of a thiazolylazo dye based on indicator displacement mechanism

A colorimetric naked-eye chemosensor for histidine (His) was established by mixing a thiazolylazo dye and Ni²⁺ in a 1:1?M ratio (TAMSMB-Ni²⁺). Due to the interaction of Ni²⁺ with His, TAMSMB was regenerated upon the addition of His to TAMSMB-Ni²⁺ to lead a significant hypsochromic shift in absorption spectra accompanied by a visual color change from red to yellow which can be directly observed by the naked eye. On the other hands, other amino acids did not trigger any significant changes in absorption properties and solution color. Moreover, it exhibited the selective recognition of His without obvious interference from other amino acids. Thus, TAMSMB-Ni²⁺ can act as a simple and efficient colorimetric chemosensor for His with sensitivity and selectivity in aqueous solution.     

Recent advances in reactions between arynes and organosulfur compounds

The recent progress made on transformations involving the reactions between aryne intermediates and organosulfur compounds has been reviewed. A wide variety of aromatic organosulfurs are now synthesizable by generating arynes in the presence of organosulfur compounds. Organosulfurs have distinctive reactivities with arynes, which depend on the sulfur atom’s valence state, that is, S(II), S(IV), and S(VI), as well as the presence or absence of other intra- or intermolecular reactive moieties. These novel transformations have enabled the diversity-oriented synthesis of unique aromatic organosulfurs that were once difficult to prepare by the conventional methods, paving the way for the development of molecules that are beneficial across numerous disciplines, including pharmaceutical science and materials science.