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Molecular structure and vibrational spectra of phenolphthalein and its dianion

2001; Elsevier BV; Volume: 57; Issue: 2 Linguagem: Inglês

10.1016/s1386-1425(00)00371-1

1873-3557

Ko‐Ki Kunimoto, Hiromasa Sugiura, Toshiyuki Kato, Hitoshi Senda, Akio Kuwae, Kazuhiko Hanai,

Traditional and Medicinal Uses of Annonaceae

Infrared (IR) and Raman spectra of phenolphthalein (PP) and its dianion form (sodium and potassium salts) were studied both in the solid state and in aqueous solution. Band assignments were carried out on the basis of the isotope shifts of the ring deuterated and 13C-substituted derivatives. Spectral analyses reveal that the PP dianion exists as mixtures of the benzenoid form (colorless) and the quinonoid form (colored) in the solid state and in aqueous solution, while the neutral PP solely takes the gamma-lactone form. This work provides the first vibrational spectroscopic evidence for the coexistence of the two species in the PP dianions.