SYNTHESIS, STRUCTURE, AND PHOTOPHYSICAL P ROPERTIES OF POLYARYLATED IMIDAZOLES AND OXAZOLES

23 tetraphenylimidazoles 1,2 and 11 triphenyloxazoles 4,5 with amino, nitro, methoxy, hydroxy, or halogeno substituents chiefly in the para position were prepared. The absorption and fluorescence emission prope rties were investigated in ethanolic solution. The effects of the subs tituents in 1,2 on the spectral shifts show that the arrangement of th e phenyl rings in 1 position is not coplanar in relation to the hetero cycle whereas the phenyl rings in 2 position are more coplanar. The sp ectral changes of compound 2a in solvents of various polarity (dielect ric constants 2,02-47,24) are almost negligible. The Stokes shift is m oderately increased. A remarkable increase in the fluorescence quantum yield is observed by chlorine substitution in phenyl ring 2.