Electronic energy transfer in supersonic jet expanded naphthalene-(CH2)n-anthracene bichromophoric molecules

A study of intramolecular electronic energy transfer (Intra-EET) has provided evidence, for the first time, of a dramatic difference in Intra-EET efficiency results obtained under jet cooled and room temperature solution conditions. This was observed with anthracene-(CH2)n-naphthalene bichromophoric molecules, A1N (n = 1) and A3N (n = 3). The rich fluorescence excitation spectrum of the naphthalene moiety in A1N indicates an inefficient EET process whose rate constant is substantially slower than that of the naphthalene moiety fluorescence. It was shown that the EET rate depends on a specific vibronic excitation that affects the molecular conformation, and was found to be at least two orders of magnitude slower in A1N molecule compared to A3N.