Effect of the sulphonic group position on the properties of monoazo dyes

The colour properties of monoazo dyes, analogues of C.I. Direct Red 23 (CI 29160), containing a sulphonic acid group in the diazo component have been examined. Optimisation of the molecule geometric structure was carried out by the AM 1 method, while the absorption maximum positions were calculated by the PPP-MO method. The calculated and found values are in good agreement . It has been found that the position of the sulphonic acid group significa ntly affects the molecule spatial structure and thereby the coupling effect . (C) 1999 Elsevier Science Ltd. All rights reserved.