Publication Type Journal Article
Title Thioindigo, and sulfonated thioindigo derivatives as solvent polarity dependent fluorescent on-off systems
Authors Ricardo C. Pereira Marta Pineiro Adelino M. Galvão J. Sergio Seixas de Melo
Groups MPPM
Journal DYES AND PIGMENTS
Year 2018
Month November
Volume 158
Number
Pages 259-266
Abstract The synthesis of a novel series of 5,5 -sulfonamide thioindigo derivatives, including a new synthetic methodology (via microwave assisted synthesis), together with a comprehensive electronic spectral and photophysical characterization is described. The study made in solution, as a function of the solvent polarity, showed-rationalized by TDDFT calculations- that in nonpolar solvents the high efficiency of the radiative deactivation channel (50\% in dioxane and 70\% in benzene) is due to an S-1 (of pi,pi* origin) in the trans form, whereas in polar solvents the low fluorescence quantum yield (1\% or less) is due to the adiabatic stabilization of the trans and saddle S-1 forms, making the sloped type CI (Conical Intersection) with S-0 energetically accessible thus becoming an efficient competitive decay channel to the radiative pathway. It is shown that thioindigo and all the 5,5 -sulfonamide thioindigo derivatives exhibit on-off fluorescence that can be tuned by the solvent polarity. The presence of a dark cis form with an S-1 (of n,pi* origin) was confirmed by the appearance of a new absorption band, upon irradiation, assigned by TDDFT to an S-2 (of pi, pi* origin) state.
DOI http://dx.doi.org/10.1016/j.dyepig.2018.05.049
ISBN
Publisher
Book Title
ISSN 0143-7208
EISSN 1873-3743
Conference Name
Bibtex ID ISI:000439675800032
Observations
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