Ultrafast Excited State Dynamics Investigation of N,N-dimethyl-6-propionyl-2-naphthylamine Hydrogen-bonded Complexes
Suppressing the formation of twisted intramolecular charge transfer(TICT)can markedly improve the flu-orescence intensity and photostability of luminescent materials.However,accurate methods for predicting the pres-ence of TICT are currently lacking.This paper investigated the excited state dynamics of N,N-dimethyl-6-propionyl-2-naphthylamine(PRODAN)across various solvents utilized the Kamlet-Taft theory,coupled with both steady-state and transient absorption spectroscopy,complemented by quantitative calculations.The analysis of steady-state spectra re-vealed that the primary determinant of the Stokes redshift in the PRODAN complexes is the solvent's polarity and hydro-gen-donating capacity.Transient absorption spectra provided insights into fast timescales(τ1 and τ2),corresponding to the formation of intramolecular charge transfer and TICT processes,while slower timescales(τ3 and τ4)were associat-ed with solvation and fluorescence radiation processes.Furthermore,experimental findings demonstrated that an in-crease in solvent polarity and hydrogen-donating ability expeditiously influences the dynamics processes within PRO-DAN hydrogen-bonded complexes.Theoretical computations solidified these observations,confirming the formation of a stable TICT state in highly polar and strongly hydrogen-donating methanol solvent.These insights not only contribute to our understanding of the ultrafast dynamics of PRODAN but also provide valuable guidance for the strategic design of fluorescent probe molecules and thoughtful solvent selection in the field of fluorescence research.
twisted intramolecular charge transferexcited state dynamicstransient absorption spectroscopyquantum chemical calculation
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