岩田 理

Novel photosensitized dyes having trifluoromethylacrylic acid as an acceptor-anchor moiety (MCL26-29) are synthesized. These dyes seem to suppress the back-donation currents from the conduction band of TiO2 semiconductor to the electrolyte. Their fabricated dye-sensitized solar cells (DSCs) show high IPCE performances (MCL27; over 80% between 400-520 nm, max 90% at 465 nm). In particular, the high IPCE properties are compared with more than 80 article examples.

Novel photosensitized dyes containing 4-trifluoromethylthiazole-5-carboxylic acid as an acceptor are synthesized. Stilbene-type dyes with this acceptor show high performance as dye-sensitized solar cells. The trifluoromethyl group is assumed to act as a suppressor of electron back-donation from the TiO2 conduction band to the electrolyte and as an accelerator of charge separation in the photoexcited state.

ortho-Azacrown-substituted (tetrafluorophenyl)imidazo[1,2-a] pyridine (2) in an acetonitrile solution emits 380 nm light in the presence of Li(+) cation and emits 460 nm light in the presence of Zn(2+), Mg(2+) or H(+) cation. In contrast, para-azacrownsubstituted analogue (1) emits three different fluorescent lights responding to Li(+), Zn(2+) or H(+) cation, respectively; 388 nm light to Li(+) cation, 433 nm light to Zn(2+) cation or 469 nm light to H(+) cation.

When the photochromism of 2-(3'-pyridylmethylene)-7-ethylbenzo[b]thiophen-3(2H)-ones (4) was investigated, high thermal stability of the E isomer of 4, 4(E) and good repeatability of the photoinduced E,Z-isomerization were found. Association constants of the 1: 1 complexations of 4(Z) and 4(E) with the ureidoporphyrin 1 and with the pentafluorobenzamidoporphyrin 2 were evaluated. We found that I captures 4(E) preferentially to 4(Z) and, reversely, 2 prefers 4(Z) to 4(E). On the basis of these differences in the binding ability, we concluded that the repeatable movement of the. hemithioindigo, so-called the hemithioindigo shuttle, between two kinds of porphyrins was controlled by the photoirradiation. These movements were applied to create a molecular switch for changes in the quinone distribution between two kinds of porphyrins.

Photoirradiation of the pentafluorophenyl-substituted Z-hemithioindigo 1 causes a novel type of photoinduced cyclization, to produce the intramolecularly cyclized alcohol 2 and its dehydrated ether 3. For this photoinduced cyclization, the o-fluorine atoms of the phenyl group of 1 are found to be crucial. (C) 2007 Elsevier B.V. All rights reserved.

2-(3,4,5,6-Tetrafluoro-2-hydroxyphenyl)imidazo[1,2-a]pyridine (1) emits long wavelength light around 540 nm both in polar and in nonpolar solvents. Zn2+ perchlorate in acetonitrile causes the intermediate wavelength emission around 430 nm, which is ascribed to the species where the imidazole nitrogen atom and the phenolate oxygen atom bridge Zn2+. In the presence of Hg(2+)and Al3+ perchlorates, short wavelength emission around 370 nm is strongly increased and this fluorescent enhancement is attributable not to the coordination of Hg2+ and Al3+ to 1 but to the formation of the salt of perchloric acid of 1.

2-(2-Hydroxyfluorophenyl)benzoxazole having an imidazole moiety 1 was synthesized by the two step reactions starting from 2-(pentafluorophenyl)benzoxazole. Protonation at the 3-imidazole nitrogen atom of 1 enhances the green emission around 500 nm, where the positive character caused by the protonation is inductively communicated to the hydroxy group, to recover its intramolecular hydrogen bonding, leading to the ESIPT process. Addition of Al3+ or Zn2+ to 1 enhances both the green emission and the blue emission around 450 nm in chloroform-acetonitrile. (c) 2006 Elsevier B.V. All rights reserved.

The benzoyl-substituted hemithioindigo 1 with Z-configuration was obtained as the sole product from the reaction of 7-ethylbenzo[b]thiophen-3(2H)-one with phenylglyoxal. Irradiation of 1 produced the [2+4] cycloadduct 2, instead of the usual Z-E isomerization product. The cycloadduct 2 is completely dissociated back to 1 on heating; the interconversion between 1 and 2 shows good repeatability. This reversible property is applied to the molecular switch in the hydrogen-bonded quinone recognition of the 5,15-cis-bis(ureidophenyl)porphyrin 3.

The large difference in the binding affinity of tetramethoxy-p-benzoquinone between 5,15-cis-bis(ureidophenyl)porphyrin and its zinc-porphyrin analogue enables construction of a reversible system in which tetramethoxy-p-benzoquinone moves between 5,15-cis-bis(ureidophenyl)porphyrin and the zinc-porphyrin as a quinone shuttle and a nitrate ion works as a chemical switch. Copyright (C) 2005 Society of Porphyrins & Phthalocyanines.

Benzoyl-substituted hemithioindigo 1 has a novel type of photochromic behavior based on the formation of the photoinduced [2+4] cycloadduct; that is, irradiation of 1 produces the cycloadduct 2 with all trans-configurations between the adjacent carbonyl moieties; this is completely dissociated back to 1 on heating.

The photochromism of porphyrin caused by putting on and off hydrogen chloride, which is generated by the photodegradation of solvent, is investigated. The effect of solvent and porphyrin substituent on the photochromism is surveyed and 50% 2-chloroethanol in ethyl acetate is found to be suitable as solvent from the viewpoints of the quick generation of hydrogen chloride by irradiation and the facile abstraction of hydrogen chloride from the porphyrin hydrochloride salt on heating, 5, 10, 15, 20-tetrakis (4-trifluoromethylphenye)porphyrin (CF<SUB>3</SUB>TPP) being fitted because of its light resistance. The photochromic system consisted of CF<SUB>3</SUB>TPP and 50% 2-chloroethanol reveals to be stable to the repeated putting on and off hydrogen chloride.

The peak potentials (Ep) of 3-substituted pyrido[1′,2′:l,2]imidazo[4,5-b]pyrazine and pyrido[1′,2′:l,2]imidazo[4,5-b]quinoxaline derivatives are sufficiently correlated with Hammett substituent constant σm and with the PM3 calculated LUMO energy levels, and the linear relationship between electron potentials of 9-substituted pyridoimidazoquinoxalines and the LUMO energy levels is also found out.

Novel fluorescent pyrido[1',2':1,2]imidazo[4,5-b]pyrazine derivatives having a crown ether side-arm, 1a, b, recognise alkaline earth metal cations and thiocyanate anions coincidentally, making a function as an AND logic gate which has fluorescence quenching output.

Additions of various carbanion nucleophiles to 3,3,3-trifluoro-1-nitropropene (1) proceeded regiospecifically at the C-2 position of 1 to give the corresponding adducts. The nitro group of the adducts, derived from the reactions with acetylacetone and ethyl acetoacetate, was reduced to the corresponding amines, which were cyclized in situ to the 3-(trifluoromethyl)pyrrole derivatives.

Synthesis of pyrido[1′,2′:1,2]imidazo[4,5‐b]quinoxalines by the facile cyclizations of 2,3‐dichloroquinoxalines with 2‐aminopyridines and of 2‐amino‐3‐chloroquinoxalines with various substituted pyridines is described. Copyright © 1992 Journal of Heterocyclic Chemistry

Trifluoromethyl (CF3) -1, 3- dipolar compounds such as nitrile oxide, imines, ylides, nitrones, and azomethine ylides are applied as the building blocks of various CF3- azoles. Their reactivity, particularly regio- and stereoselectivity of the cycloadditions, is discussed mainly on the basis of the interaction between the frontier orbitals of CF3- dipolar compounds, some of which are calculated by the CNDO/2 methods, and those of the dipolarophiles. The initially produced CF3-isoxazoles are utilized as the synthetic intermediates. For example, a variety of CF3-isoxazoloazines are prepared from the condensations of 3-CF3-5-amino-4-methoxycarbonylisoxazoles and the potential of 3-CF3-isoxazolines as the precursors of CF3 -1, 3- aminoalcohols are demonstrated. Moreover, CF3-hydrazides, imidoyl chlorides, and hydrazones are also applied as the building blocks of CF3- tetrahydro-1, 3, 4, 2-oxadiazaphospholes, Reissert analogue salts, and 4-hydroxypyrazoles, respectively. © 1987, The Society of Synthetic Organic Chemistry, Japan. All rights reserved.