Fluorescence spectroscopic and kinetic study of triethylamine exciplex formation with ethanol

Exciplex formation of triethylamine with ethanol and with deuterated ethanol at low alcohol concentrations in hydrocarbon solutions is shown by steady state and time-resolved fluorescence spectroscopy. The observed spectra and the decay kinetics show the appearance of three exciplex structures which can be discriminated by temperature and deuterium isotope effects. The spectrum of the primarily formed 1:1 heterodimer overlaps significantly with the monomer spectrum (spectral shift is 800 cm −1 ) and equivalent associations are found with tetrahydrofuran. The photophysical parameters change only slightly on complexation. Two further exciplex emissions with large spectral shifts compared with the monomer (4500 cm −1 and 9000 cm −1 ) arise at ethanol concentrations above 0.02 M, together with a diminution of the quantum yield. Complexation with non-deuterated ethanol leads primarily to high energy emissive structures and equilibrium is attained, as they decay with a common lifetime. Deuteration of ethanol results in a stabilization of the lowest energy exciplex, which is populated irreversibly. Exciplex structures are discussed, with reference to ab inition model calculations.