An experimental and theoretical study of the photophysical properties and the dipole moments of methoxynitronaphthalenes

Isomeric methoxynitronaphthalenes (MNN, 14 possible isomers, cf. Scheme 1) were studied theoretically and experimentally. PPP calculations were carrie d out for all possible isomers and the results were compared with the exper imental electronic absorption, fluorescence, and phosphorence spectra of se lected isomers. Also the phosphorescence lifetimes were determined. Theoret ical ground-state dipole moments of MNN were obtained as a combination of t he pi-component (PPP method) and the sigma-component (a vector sum of sigma -bond and group moments). The experimental groundstate dipole moments were measured for a series of MNN (on a dipole meter) and compared with the theo retical values. The effect of solvent polarity upon the electronic absorpti on and Fluorescence spectra of selected MNN was studied and the solvatochro mic method using the Bakhshiev and Kawski-Chamma-Viallet equations and the ground-state dipole moments was employed to obtain the experimental first e xcited singlet-state dipole moments.