Reflectance bathochromic displacement

The molecule has several chromophores able to reflect the modifications of ionisable groups the C=0 of COOH, the aromatic phenolic ring and the sulphonamide one. At pH 2.6 the ORD curve corresponds to the non-ionised molecule. One can distinguish a COTTON effect at 280 nm that is associated with one of the aromatic bands in this region of the spectrum and a more important positive one at 225 nm. Up to pH 4.8 only a slight displacement of the curve from 250 to 350 nm without any apparent modification of the aromatic COTTON effects is observed. This displacement is due to a modification in the C=0 the absorption band of which is at 200 nm. At pH 10.70 ionisation of the phenol causes a bathochrome displacement of the COTTON... 

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