Quantum yields of photocoloration and molar absorption coefficients of ferrocenyl substituted benzo and dibenzochromenes. Comparisonwith their phenyl-homologues

摘要

The photochromic properties of three ferrocenyl-[2H]-benzopyrans were investigated undermonochromatic irradiation and compared with those of their phenyl homologues. The UV/visible spectra ofthe closed and open forms are reported together with the quantum yields of photocoloration. It was shownthat the ferrocenyl- substitution induces the formation of a new band in the 500–700 nm range in the openforms, however, it does not affect significantly the UV spectra of the closed forms. Ferrocenyl- substitutionwas also shown to increase the thermal bleaching rate constants and to decrease the photocoloration quantumyields. For most compounds, photochromic behaviour was not sensitive to the irradiation wavelength.However, for the methyl ferrocenyl chromene, the open form spectrum was slightly dependent of the irradiationwavelength. The influence of the ferrocenyl group and other structural features on the photochromicproperties are discussed.