The relationship between the steric hindrance and absorption spectrum of fluoran dyes. Part II

The steric hindrance at the 2-position of the fluoran ring and its influenc e on the electronic absorption spectrum were studied by semiemprical MO cal culations. All fluoran dyes in this study gave two or more conformers by us ing structure optimization. Spectral changes and band shapes with respect t o the steric hindrance of the amino group at the 2-position are discussed o n the basis of calculations performed for a variety of conformations. A goo d correlation between the wavelengths of separated peaks and those of calcu lated peaks was obtained.