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Azobenzene dyes derived from various anilines and aminothiahetcrocycles azo-coupled with commercially important N,N-dicthyl-m-toluidine (T series) and N,N-diethyl-m-acetylaminoaniline (A series) are positively solvatochromic. The visible spectra of 16 pairs or derivatives have bccn measured in up to 22 solvents, and the transition energies related to Kamlet -Taft solvent polarity parameters. In general, A-series dyes are

If a diarylalkyne 4-XC6H,CzCR (R = Ph,,H,) or 1 -phenylpropyne in trifluoroacetic acid containing mercury( 11) trifluoroacetate is irradiated with U.V. light filtered through Pyrex glass, the e.s.r. spectrum of the corresponding azulene can be observed. The azulenes have been isolated and converted back into their radical cations by irradiation in trifluoroacetic acid, or in dichloromethane containing (4-BrC6H,),N+' or (2,4-Br, C, H, ), N +*.Possible mechanisms by which the azulenes are formed from the alkynes are discussed.