Influence of Geometry on the Emitting Properties of 2,3-Naphthalimides

Pierre Valat, Véronique Wintgens, Jean Kossanyi, László Biczók, Attila Demeter, Tibór Bérces

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76 Citations (Scopus)

Abstract

The luminescence properties of 2,3-naphthalimides have been studied using picosecond and nanosecond spectroscopies. In acetonitrile solution N-phenyl-2,3-naphthalimide (3) is found to emit dual fluorescence with emission maxima at 385 and 490 nm, respectively. The short-wavelength emission corresponds to the known fluorescence of the naphthalimides and is demonstrated for 3 to originate from a molecular conformation in which the phenyl substituent and the naphthalimide skeleton are orthogonal to each other. The long-wavelength emission is assumed to originate from a singlet excited state formed by a ca. 90° rotation of the phenyl group so that the two moieties are coplanar. Only a small dipole moment change is found between this excited state and the ground state. Only short-wavelength emission is observed with a lifetime in the nanosecond range as in the case of 1 and 2 when phenyl rotation is blocked with a bulky ortho tert-butyl group (compound 4). Increasing the viscosity of a glycerol/ethanol medium enhances both the efficiency and the lifetime of the short-wavelength emission of 3. It appears that at 77 K the emission originates directly from the Franck-Condon state. At room temperature, the other two emitting species are shown to arise from the Franck-Condon state by competitive intramolecular geometrical relaxation processes. Structures 5 and 6 are tentatively put forward to explain the formation of naphthazepinedione 8 by a 2π + 2π photochemical cycloaddition reaction.

Original languageEnglish
Pages (from-to)946-953
Number of pages8
JournalJournal of the American Chemical Society
Volume114
Issue number3
DOIs
Publication statusPublished - Jan 1 1992

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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