PHOTOPHYSICAL PROPERTIES OF A HEXADODECYLOXY-SUBSTITUTED TRIARYLPYRYLIUM SALT - SELF-ASSOCIATION IN SOLUTION

The photophysical properties of a triarylpyrylium salt bearing six dodecyloxy peripheral chains and able to form organized assemblies (columnar liquid crystals, Langmuir-Blodgett films) have been studied in dichloromethane and n-heptane solutions. It is shown that self-association occurs in n-heptane, the aggregate size increasing with concentration. Aggregate growth induces a hypsochromic shift in the absorption spectra and a bathochromic shift in the fluorescence spectra. The continuous variation of the spectroscopic properties with the size of the aggregates proves the existence of very strong long-range interactions, due to the ionic nature of the chromophores. Both absorption and fluorescence probably involve localized excited states.