Spectroscopic properties of aromatic dicarboximides. Part1.—N—H and N-methyl-substituted naphthalimides

Abstract

The photophysical properties of the N-H and N-methyl derivatives of 1,2-, 2,3-and 1,8-naphthalimides have been studied. The shift of the fluorescence emission position as a function of the solvent polarity indicates only a weak variation of dipole moment for the excited state compared with the corresponding value in the ground state (5.7 D for 26, 2.8 D for 36 and <2 D for 46, 1 D z 3.33564 x C m, and 26, 36 and 46 are N-methyl-1,2naphthalimide, N-methyl-2,3-naphthalimide and N-methyl-1 ,&naphthalimide). However, important modifications of the photophysical properties are observed which depend on the relative position of the dicarboximide moiety on the naphthalene ring: the intersystem crossing rate constant of 46 increases dramatically by three orders of magnitude compared with that of 26 ; simultaneously, the fluorescence quantum yield decreases from 0.77 to 0.03, although the corresponding rate constant, k,, increases. This difference is found to arise from the energy gap between the lowest '(n,n*) singlet excited state and the upper 3(n,n*) triplet state, which is of the order of 9 kcal mol-' for 26 and less than 2 kcal mol-' for 46 in acetonitrile solution. Protic solvents increase the energy difference between the n,n* and n,n* states thus decreasing the mixing of the two levels; as a consequence, the lifetime of 46 is increased, i.e. from <60 ps in hexane to 2.1 ns in trifluoroethanol. A triplet-triplet annihilation process occurs with the N-methyl derivatives 36 and 46 which leads to a monomer delayed fluorescence with the former, and mainly to a delayed excimer emission with the latter.

Synthesis and Photophysical Characterizations of Thermal -Stable Naphthalene Benzimidazoles

“…Highest quantum yield observed for NB_II (Φ f = 0.60). The presence of electron donating substituents may also increase the separation between the singlet (S 1 ) and its closer triplet excited state, thus decreasing the intersystem crossing (ISC) and favoring the fluorescence deactivation channel [24][25][26][27][28][29][30][31][32] (Figs. 5 and 6).…”

1,8-Naphthalimides for non-doping OLEDs: the tunable emission color from blue, green to red

“…Elemental analysis data were obtained on a Perkin-Elmer 240c instrument. Fluorescence lifetimes of compounds were measured by [35] 379(0.03) NP-OCH 3 [36] 480 NP-piperazin [20] 515(0.03) NP-N(CH 3 ) 2 [23] 538…”

“…NP-REF was prepared by condensation of 2-butyl-6-hydrazino-benzo-[de]-isoquinoline-1,3-dione with acetaldehyde [20]. NiH: 1,8-naphthalimide [35]; NP-OCH 3 : 4-methyoxyl-Nbutyl-1,8-naphthalimide [36]; NP-piperazin: 4-(4 -methyl-piperazin-1-yl)-N-butyl-1,8-naphthalimide [20]; NP-N(CH 3 ) 2 : 4-dimethylamino-Nbutyl-1,8-naphthalimide [23].…”

Determination of Water Content in Organic Solvents by Naphthalimide Derivative Fluorescent Probe

“…2,3 It is commonly acknowledged that solvent-dependent spectral changes can arise from either general or specific solvent effects. 4 The first effect results from interactions of the dipole moment of the fluorophore with the reactive field induced in the surrounding solvent.…”