Toward the Photostability Mechanism of Intramolecular Hydrogen Bond Systems. 4. 3(5)-(1'-Hydroxy-2'-naphthyl)pyrazoles and 3(5)-(2'-Hydroxy-1'-naphthyl)pyrazoles
摘要:
Two new families of compounds, the 3(5)-(1'-hydroxy-2'-naphthyl)pyrazoles (a series) and the 3(5)-(2'-hydroxy-1'-naphthyl)pyrazoles (b series), have been synthesized and fully characterized. The use of NMR (H-1 and C-13) and UV (absorption and emission) spectroscopies in different solvents led us to determine the major tautomers, the coplanarity of both rings (naphthyl and pyrazolyl) if present, and the existence of hydrogen bonds. The photostability of a representative set of such derivatives was also determined, showing that the existence of an intramolecular hydrogen bond (IMHB) is not an essential condition for providing UV stability. Moreover when such an IMHB is present in the molecule, the photostability is not dependent on whether the proton is transferred or not.
Toward the Photostability Mechanism of Intramolecular Hydrogen Bond Systems. 4. 3(5)-(1'-Hydroxy-2'-naphthyl)pyrazoles and 3(5)-(2'-Hydroxy-1'-naphthyl)pyrazoles
摘要:
Two new families of compounds, the 3(5)-(1'-hydroxy-2'-naphthyl)pyrazoles (a series) and the 3(5)-(2'-hydroxy-1'-naphthyl)pyrazoles (b series), have been synthesized and fully characterized. The use of NMR (H-1 and C-13) and UV (absorption and emission) spectroscopies in different solvents led us to determine the major tautomers, the coplanarity of both rings (naphthyl and pyrazolyl) if present, and the existence of hydrogen bonds. The photostability of a representative set of such derivatives was also determined, showing that the existence of an intramolecular hydrogen bond (IMHB) is not an essential condition for providing UV stability. Moreover when such an IMHB is present in the molecule, the photostability is not dependent on whether the proton is transferred or not.