Synthesis and photochromic properties of 9-(4-substituted)phenoxy-naphthaceno[5,6-bc]pyran-2,8-diones derived from phenoxynaphthacenequinones

A series of novel 9-(4-substituted)phenoxy-naphthaceno[5,6-bc]pyran-2,8-diones were synthesized and their structures were confirmed using elemental analysis and the IR, 1H NMR and MS spectra. The photochromism of these compounds was observed in DMSO, DMF, CH2Cl2, CHCl3, benzene and toluene. The trans forms had an absorption maximum in the range of 419–422 nm, while the ana forms had two large absorption maxima in the ranges 489–492 nm and 524–526 nm. The λmax and isosbestic points were affected little by the electronic properties of the substituents on the phenoxy group. However, the formation of the photostationary state was strongly influenced by the polarity of the substituents.