Pyrrole studies. X. The preparation and electronic spectra of phenyldipyrromethenes

Abstract

The NH frequency and the electronic spectra of 22 phenyldipyrromethenes have been measured. The spectral data confirm the presence of steric interaction between phenyl groups in the 3,3?-positions, but it was not possible to ascertain whether the interaction is relieved by a loss of coplanarity of the dipyrromethene system or by rotation of the dipyrromethene rings. The synthesis of 12 new phenyl-pyrroles is also described.