The preparation and spectroscopic properties of some di- and tri-substituted 1,3,5-triphenyl-2-pyrazolines and related 2-pyrazolines

Abstract

The effect of substituents on the absorption and fluorescence properties of a number of di-and tri-para-substituted 1,3,5-triphenyl-2-pyrazolines, several substituted 1,3,5,5-tetraphenyl- and trans-l,3,4,5-tetraphenyl-2-pyrazolines, and some 1,3-diphenyl-trans-3a,4,5,6,7,7a-hexahydro-4,7- methano-1H-indazoles in cyclohexane and in methanol has been studied. Certain electron-with-drawing substituents, namely, cyano, methylsulfonyl or methoxycarbonyl, have a marked effect. Such substituents located (Å) in the 1-phenyl ring give pyrazolines exhibiting blue fluorescence which is quenched if a cyano group is also present in the 5-phenyl ring, (B) in the 3-phenyl ring give fluorescent yellow compounds which can be considered as dyes, and (c) in the 5-phenyl ring cause quenching of the fluorescence (unless an electron-withdrawing group is also present in the 3-phenyl ring).