EXCITED-STATE PROPERTIES OF PRETWISTED 7-DIETHYLAMINO COUMARINYL BENZOPYRANO PYRIDINE - AN EXPERIMENTAL AND AM1 STUDY

A detailed investigation of the photophysical properties of a new coum arin heterodimer: rinyl)-5-oxo-4-methyl[1]benzopyrano(3,4-c)pyridine ( CBP) has been performed in a range of nonpolar and polar solvents at r oom temperature. In addition, the influence of temperature on the exci ted state properties of CBP in dichloromethane, methanol and dimethyls ulfoxide has also been investigated. These studies indicate that the f luorescence of the dye is from the pre-twisted intramolecular charge t ransfer (ICT) state. AM1 semiempirical calculations performed for CBP in the ground, excited singlet and triplet states are in conformity wi th the experimental results. The presence of second coumarin is found to introduce a larger charge transfer character to the parent coumarin molecule when compared to other diethylamino coumarins. From this stu dy it is also evident that such coumarin hetero dimers behave more lik e any other single absorbing and emitting chromophoric-systems. (C) 19 98 Elsevier Science S.A. All rights reserved.