- Water-induced fluorescence quenching of mono- and dicyanoanilines
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Photophysical properties of monocyano- (2-, 3-, and 4-cyano) and dicyano- (3,4-, 3,5-, 2,3-, 2,4-, 2,5-, and 2,6-dicyano) anilines are investigated by fluorescence measurements. All the monocyanoanilines are virtually nonfluorescent in water (quantum yield 0.01); however, in nonaqueous solvents (cyclohexane, acetonitrile and ethanol), the fluorescence quantum yield is enhanced substantially. In contrast, dicyanoanilines investigated are highly fluorescent both in aqueous and nonaqueous environments. The photophysical data and MO calculations suggest that conformational changes in the amino group and variation of hydrogen-bonding interactions between the solute and solvent water upon electronic excitation are responsible for the water quenching in the monocyanoanilines.
- Oshima, Juro,Yoshihara, Toshitada,Tobita, Seiji
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p. 306 - 311
(2008/02/13)
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- XANTHINE OXIDASE INHIBITORS
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The invention relates to compounds of the following formula (I) or their salts: in which R1 represents OR4 or others, in which R4 is an alkyl group having 1-8 carbon atoms which may have a substituent or the like; R2 is halogen, nitro, cyano, carboxyl, or the like; R3 is hydrogen, halogen, hydroxyl, amino, carboxyl, or the like; X is NR11, oxygen, or sulfur, in which R11 is hydrogen, or an alkyl group having 1-8 carbon atom which may have a substituent; and each of Y and Z is CR12 or nitrogen, in which R12 has the same meaning as R3 above, and a xanthine oxidase inhibitor containing the compound as an active ingredient.
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- Synthesis of 3-Nitrophthalonitrile and Tetra-α-substituted
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An efficient synthesis of phthalocyanines prepared from ortho-substituted phthalonitriles is described.The precursor to these phthalocyanines, 3-nitrophthalonitrile, is a key reagent for syntheses of phthalonitriles substituted at the 3-position by means of nucleophilic aromatic substitutions.An example of this type of phthalocyanine, prepared from 3-(4-cumylphenoxy)phthalonitrile, is compared with the phthalocyanine derived from 4-(4-cumylphenoxy)phthalonitrile.Substitution of the phthalocyanine at this more sterically crowded site causes a 20 nm bathochromic shift of the Q-band (?-?* transition).
- George, Robert D.,Snow, Arthur W.
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p. 495 - 498
(2007/10/02)
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- Kinetic and equilibrium in the ammonolysis of substituted phthalimides
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Kinetic studies are reported for the base hydrolysis to phthalamic acid anions (H) and ammonolysis to phthalamides (A) for seven phthalimides (P): 1, unsubstituted; 2, 4-NO2; 3, 4-Cl; 4, 4-tBu; 5, 3-NO2; 6, 3-Me; 7, 3-Me3Si.The hydrolysis kinetics require two mechanisms, one which is first order in neutral imide and first order in hydroxide ion, and a second, which is important only in quite concentrated NaOH, which is first order in neutral phthalimide and second order in hydroxide ion.Ammonolysis kinetics for 1-5 revealed the rate law: Rate = kN ->.A mechanism is proposed with rate-determining breakdown of the anionic form of the tetrahedral intermediate derived by addition of NH3 to the phthalimide.The ammonolysis is reversible.The phthalamide hydrolyzes to the phthalamic acid via cyclization to an intermediate phthalimide, which is detected in concentrated base where its formation from phthalamide is more rapid than its subsequent hydrolysis.Rate constants for the cyclization follow the rate law: Rate = kcyc ->.This reaction is the microscopic reverse of the ammonolysis, and the ratio kN/kcyc provides the equilibrium constant Keq for the reaction P + NH3 = A.Values for 1-5 lie in the range 2 x 102 - 4 x 103.With 3-methylphthalimide, kinetics in aqueous ammonia do not obey a first-order relationship, but they could be analyzed by a scheme whereby the phthalimide is converted reversibly to the phthalamide and simultaneously undergoes an irreversible hydrolysis.The value of Keq in the system is 1.8.With 3-trimethylsilylphthalimide the value of Keq is further reduced to 0.01.The ammonolysis reaction does occur more quickly than hydrolysis but the equilibrium is so unfavorable that even in concentrated ammonia only a small amount of the phthalamide is ever formed.
- McClelland, Robert A.,Seaman, N. Esther,Duff, James M.,Branston, R. E.
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p. 121 - 128
(2007/10/02)
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