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Paper | Regular issue | Vol 55, No. 12, 2001, pp.2325-2340
Published online, 1st January, 1970
DOI: 10.3987/COM-01-9345
Hammett Type Correlations for Intramolecular Charge Transfer (ICT) Dipole Moments of 4’-Substituted 9-Styrylacridines in the Ground State and in the Excited State

Mohamed El Azami, Najib Bitit,* Abdelali Kerbal, Souad Lahlou, Saadia Aït Lyazidi, Jean-Pierre Desvergne, Henri Bouas-Laurent,* and Dario Bassani

*Laboratoire de Chimie Organique et Organometallique, CNRS UMR 5802, Université Bordeaux, I, 351 cours de la Libération, 33405 Talence Cedex, France

Abstract

9-Styrylacridine (1a) and a series of 4’-substituted 9-styrylacridines (1b-f) (substituent : Me, OMe, NMe2, Cl, NO2) have been prepared to study their spectroscopic properties in several solvents of different dipolarity. They show strong Stokes shifts from the ground state to the S1 excited state (Δν = - 5400 to - 8700 cm-1) which denotes an important change of conformation in the fluorescing state. AM1 calculations suggest that the coplanarity increases in the S1 state. The fluorescence spectra exhibit a positive solvatochromism, allowing the determination of excited state dipole moment (μE). Hammett correlations between σπ and μG (ground state dipole moments) and μE respectively, show that the electronic influence of substituent on the internal charge transfer (ICT) is ca. 3 times stronger in the S1 excited state than in the ground state.