Configurational and Conformational Aspects in the Excimer Formation of Bis(carbazoles)

J. Vandendriessche, S. Toppet, N. Boens, F. C. De Schryver, P. Palmans, Hiroshi Masuhara

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Abstract

Intramolecular excimer formation of 1,3-di-N-carbazolylpropane and of meso- and rac-2,4-di-N-carbazolylpentane in isopentane and isooctane has been investigated. Thermodynamic and kinetic data are obtained by stationary-state and time-correlated fluorescence measurements as a function of temperature. The differences in the emission spectra are explained by considering the starting ground-state conformations as revealed by 1H NMR data. meso-2,4-Di-N-carbazolylpentane has only the TG/GT conformation in the studied temperature region (180–350 K). The excimer conformation with total overlap of the chromophores (TT, λmaxem = 420 nm) is reached via one rotation. rac-2,4-Di-N-carbazolylpentane has two conformations (TT and GG). The TT conformation of rac-2,4-di-N-carbazolylpentane is the more stable one (ΔG = 5.1 kJ/mol) and is the precursor of the TT partial overlap excimer (λmaxem = 370 nm). For 1,3-di-N-carbazolylpropane a distribution is assumed between the tt and tg±; conformations. The excimer conformation (g±g±, λmaxem = 420 nm) in l,3-di-N-carbazolylpropane is reached via one (tg± → g±g±) or two rotations (tt→tg± → g±g±).

Original languageEnglish
Pages (from-to)8057-8064
Number of pages8
JournalJournal of the American Chemical Society
Volume106
Issue number26
DOIs
StatePublished - 1 Dec 1984

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