EXPERIMENTAL AND THEORETICAL STUDY OF THE STYRYLBENZOPYRYLIUM CHROMOPHORE

Structural transformations of 7-hydroxy-4'-methoxystyrylbenzopyrylium chloride have been investigated in buffer solutions of pH 2.00-11.00. The reactivity and aromatic stability of this and related styrylbenzopyrylium salts are predicted using standard HMO calculations and the concept of hardness, and correlated with experimental findings. Electronic spectra are calculated using the PPP method. Several model compounds are proposed, which are expected to exhibit high stability and low reactivity, and whose solutions should be red coloured.