Abstract
Steady state fluorescence depolarization measurements in a solid matrix of poly(methyl methacrylate) (PMMA) and molecular dynamics (MD) calculations were used to study the efficiency of intramolecular nonradiative singlet energy transfer between naphthalene groups in trichromophoric model compounds for polyesters derived from 2,6-naphthalene dicarboxylic acid and five aliphatic glycols. The five trichromophoric compounds studied are denoted by N-(CH 2 ) inn -N′-(CH 2 ) inn -N, where N and N′ are 2-naphthoyl and 2,6-dinaprithoyl groups, respectively, and n = 2–6. Measurements of the quantum yields for fluorescence ( θ ) and overlap integrals ( J ) in two monochromophoric compounds, methyl 2-naphthoate and dimethyl 2,6-naphthoate, as models for N and N′, respectively, were performed to estimate the Forster radius ( R 0 ) for the possible (N→N,N′→N and N→N′) transfers between chromophores. Variation with n of the anisotropy of the fluorescence when the compounds are dispersed in a solid matrix of glassy PMMA shows that the efficiency of these transfers depends on the number of methylene groups in the flexible spacer between N and N′. An analysis of MD simulations for the five model compounds was performed in order to evaluate several parameters related to the efficiency of the transfer. The experimental and theoretical variation of such parameters with n is consistent with an estimated r 0 of about 14 A for N→N′, which is the most efficient transfer in these compounds.
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