EFFECT OF THE TYPE OF LINKAGE BETWEEN PHENYL GROUPS ON THE STRUCTURE AND PHOTOCHEMICAL PROPERTIES OF 2,2-DIARYL-SUBSTITUTED PYRIDOANNELATED[2H]-CHROMENES

Three 2,2-diaryl-substituted pyridoannelated [2H]-chromenes have been studied by X-ray diffraction analysis. Bonding of the benzene rings th rough bridges of different nature and with different length affects su bstantially the orientation of the benzene rings, steric interactions at the C center, the conformation of the molecule, and the C-O bond le ngth. A correlation between the photocolorability of chromenes under s tudy and the orientation of the benzene rings with respect to the C-O bond, which provides different prerequisites to stabilization of the C (1)-centered cation formed upon cleavage of the C-O bond, was establis hed. The effect of the orientation of the benzene rings on the dark re action of ring closure was found.