%0 Journal Article
%A Rondão, Raquel
%A Sérgio Seixas de Melo, J.
%D 2013
%T Thio-Mayan-like Compounds:
Excited State Characterization
of Indigo Sulfur Derivatives in Solution and Incorporated in Palygorskite
and Sepiolite Clays
%U https://acs.figshare.com/articles/journal_contribution/Thio_Mayan_like_Compounds_Excited_State_Characterization_of_Indigo_Sulfur_Derivatives_in_Solution_and_Incorporated_in_Palygorskite_and_Sepiolite_Clays/2453044
%R 10.1021/jp306209y.s001
%2 https://acs.figshare.com/ndownloader/files/4095724
%K indigo
%K decay
%K conversion radiationless process
%K Ciba Brilliant Pink
%K clay
%K proton transfer process
%K CBP
%K photophysical behavior
%K fluorescence quantum yields
%K palygorskite
%K Indigo Sulfur Derivatives
%K TI
%K Excited State Characterization
%X Following what may mirror the recipe used by the ancient
Maya civilization,
consisting of a mixture of indigo and palygorskite, leading to the
organic/inorganic pigment known as Maya Blue, we have switched indigo
with thioindigo (TI) and a derivative (Ciba Brilliant
Pink, CBP) and synthesized what was Christianized as
“Maya Pink”. The spectral and photophysical behavior
of TI and CBP was investigated in solution
and solid state (in powder and incorporated in palygorskite clays).
In solution, TI was investigated in different organic
solvents (benzene, toluene, and dioxane) at room and low temperatures
and further compared with indigo. TI displays a different
spectral and photophysical behavior when compared to indigo: fluorescence
dominating the deactivation of the first excited singlet state (50–70%
depending on the solvent), with the S1〰→S0 internal conversion and the S1〰→T1 intersystem crossing deactivation channels representing the
remaining quanta loss. Moreover, whereas in the case
of indigo the proton transfer process in the excited state (between
the N–H and CO groups), involving the formation of
two excited species, leads to an efficient internal conversion radiationless
process, with TI this process is precluded leading to
a single exponential fluorescence decay. Incorporation of TI and CBP in palygorskite and sepiolite clays has showed
different photophysical properties with decrease of the fluorescence
quantum yields, a single exponential decay for TI and
a multiexponential decay for CBP in palygorskite. Based
on molecular fluorescence data, potential locations of TI and CBP in the clay are equated.
%I ACS Publications