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Communication | Special issue | Vol 76, No. 1, 2008, pp.161-168
Published online, 17th April, 2008
DOI: 10.3987/COM-08-S(N)22
Proton Dissociation-Induced Tautomerization of 4-Substituted 7-Hydroxycoumarin and Its Bridged Dimer in the Ground Stage

Hirohide Umeto, Kanna Kobayashi, Tetsutaro Igarashi, and Tadamitsu Sakurai*

*Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, Kanagawa-ku, Yokohama 221-8686, Japan


An investigation was undertaken to elucidate solvent effects on the intramolecular interaction between the 7-hydroxycoumarin chromophores in the title bridged dimer in the presence of tertiary amine. Analysis of equilibrium constants for the proton dissociation and proton dissociation-induced tautomerization of the title coumarin derivatives confirmed that both the hydroxycoumarin anion and the tautomer anion derived from the bridged dimer in methanol and acetonitrile are stabilized through the intramolecular hydrogen bonding interaction while dimethyl sulfoxide enables these anions to behave independently by its strong solvation effect.