Luminescence characteristics and structure of substituted 4-amino- N-aminonaphthalimids

Abstract

Electronic structure of the excited states of substituted 4-amino- N-aminonaphthalimids is investigated in the all valence electron CNDO/S approximation. The spin–orbit coupling matrix elements between singlet and triplet states are calculated. It is established that the luminescence characteristics of the compounds under study are determined both by the type of the molecular orbital prevailing in the fluorescing state and by the radiationless conversion rate. The geometric structures of the substituted 4-amino- N-aminonaphthalimids are obtained in the AM1 approximation with full geometry optimization. Particular attention is paid to the torsion angles between the substituents and the plane of the chromophore system as well as to the distance between the hydrogen atoms of the substituents in the imid part of the molecule and the oxygen atoms of the carbonyls.