Influence of dipole moments on light-emitting features of cardo-type 1H-pyrazolo[3,4-b]quinolines

Several 1H-pyrazolo[3,4-b]quinoline derivatives were synthesized from 9,9′-di(p-aminophenyl)fluorene as possible dye chromophore for the organic light-emitting diodes. All the compounds exhibit strong fluorescence in solution and in solid state as well. The maximally achieved brightness was 65 Cd/m2 and spectral range of electroluminescence (EL) covers the wavelength ranges from 420 up to 470 nm. The prepared compounds were used as dye luminophores in poly(N-vinylcarbazole) (PVK) matrix for single-layer EL light-emitting device. Principal goal of the work consists in an establishment of a possibility to operate by their light-emitting features (spectral positions of emitting lines, efficiency of electroluminescence, brightness, etc.) by appropriate changes of state dipole moments of the particular chromophore determined by semi-empirical quantum chemical calculations. The principal physical mechanism of such effects is explained within dipole-dipole interactions between the dye chromophores and PVK polymer chains.