Magnetic circular dichroism of some benzene derivatives

The MCD spectra of phloroglucin, 1,3,5-trimethoxybenzene, 1,3,5-tricyanobenzene, 1,3,5-trinitrobenzene, 1,3,5-benzenetricarboxylic acid and 1,3,5-benzenetricarbonyl chloride were measured. For the ¹E′ ← ¹A′₁ transition of phloroglucin or 1,3,5-tricyanobenzene and the ¹E′ ← ¹A′ transition of 1,3,5-trimethoxybenzene, the Faraday A term was observed and the A/D value was extracted. However, 1,3,5-trinitrobenzene, 1,3,5-benzenetricarboxylic acid and 1,3,5-benzenetricarbonyl chloride showed no magnetic circular dichroism in this spectral region. The magnetic moments in the ¹E′ states of these molecules seem to be quenched by the effects of substituents. The magnetic moments in the ¹E′ states of benzene derivatives are sensitive to substitution in the benzene ring.