Chirality of aromatic bis-imides from their circular dichroism spectra

It is demonstrated that chirality of molecules composed of 1,2,4,5-benzenet etracarboxydiimide (pyromellitic diimide) or 1,4,5,8-naphthalenetetracarbox y-diimide units is reflected by their exciton Cotton effects. The analysis is based on the calculated (ZINDO/S) excited states of the model diimide ch romophores la and 2a. Rotation of the diimide chromophores around the C-N b ond in diimides 3-5 is evaluated from the dynamic H-1 NMR data. A compariso n of chiroptical properties of bis-diimides 3-5 with the CD spectra of bis- imides 6-8 is also presented. (C) 2000 Wiley-Liss, Inc.