Steric and Electronic Effects in Basic Dyes

Absorption spectra of nine derivatives of Malachite Green containing two or three methoxy groups in the phenyl ring have been examined. In the absence of varying steric effects an excellent additive relationship is found between the electronic effects of the substituents and the position of the first electronic absorption band. Conformational changes brought about by crowding substituents are detected by an increase in intensity of the first band accompanied by a decrease in intensity of the second band.