Spectral Solvent Shift. II. Interactions of Variously Substituted Hydrocarbons with Polynuclear Aromatic Hydrocarbons

Nine electronic transitions in the chromophores naphthalene, azulene, and phenanthrene have been observed in 21 chlorinated hydrocarbons and chlorocarbons. The results support an interpretation of spectral shifts which considers interbond potentials between solvent and chromophore, involving bond polarizabilities and dipole moments. The results are generally in accord with the McRae solvent-shift theory. Exceptional behaviors of some of the transitions in azulene are attributable to changes in the magnitude of static dipole moment on excitation. The 1La transition of naphthacene has been observed in some 64 substituted hydrocarbons, the substituents ranging over nine groups. The results are also interpreted by a statistical theory using interbond (or intergroup) potentials. They are compared to the McRae theory, especially with respect to variation of the weighted mean wavelength parameter L0 and the quadratic Stark effect. The effect of the latter seems considerable while no effect of the former can be detected.