TY - JOUR
T1 - Closed nanocontainer enables thioketones to phosphoresce at room temperature in aqueous solution
AU - Jayaraj, Nithyanandhan
AU - Maddipatla, Murthy V.S.N.
AU - Prabhakar, Rajeev
AU - Jockusch, Steffen
AU - Turro, N. J.
AU - Ramamurthy, V.
PY - 2010/12/8
Y1 - 2010/12/8
N2 - Thiocarbonyl compounds possess unusual photophysical properties: they fluoresce from S2, phosphoresce from Ti only at extremely low concentrations in solution at room temperature, have unit quantum yield of intersystem crossing from S1 to T1, undergo self-quenching at diffusion-controlled rates, and are quenched by ground-state oxygen leading to self-destruction. In this article, we are concerned with finding a new method to observe phosphorescence from thioketones at room temperature in aqueous solution at high concentrations. To achieve this goal, one needs to find ways to eliminate diffusion-limited self-quenching and oxygen quenching. We present here a general strategy that has allowed us to record phopshorescence from a number of thioketones in aqueous solution at room temperature. The method involves encapsulation of thioketone molecules within a "closed nanocontainer" made up of two cavitand molecules known by its trivial name as octa acid. In these supramolecular complexes, despite two thiocarbonyl compounds being present in close proximity, no self-quenching occurs within the confined space due to curtailment of their rotational freedom. Although phosphorescence could also be observed when these thioketones are included in open containers, such as cucurbiturils and cyclodextrines, the closed container made up of octa acid is found to be the best medium to observe phosphorescence from thioketones whose excited state chemistry is essentially controlled by self-quenching.
AB - Thiocarbonyl compounds possess unusual photophysical properties: they fluoresce from S2, phosphoresce from Ti only at extremely low concentrations in solution at room temperature, have unit quantum yield of intersystem crossing from S1 to T1, undergo self-quenching at diffusion-controlled rates, and are quenched by ground-state oxygen leading to self-destruction. In this article, we are concerned with finding a new method to observe phosphorescence from thioketones at room temperature in aqueous solution at high concentrations. To achieve this goal, one needs to find ways to eliminate diffusion-limited self-quenching and oxygen quenching. We present here a general strategy that has allowed us to record phopshorescence from a number of thioketones in aqueous solution at room temperature. The method involves encapsulation of thioketone molecules within a "closed nanocontainer" made up of two cavitand molecules known by its trivial name as octa acid. In these supramolecular complexes, despite two thiocarbonyl compounds being present in close proximity, no self-quenching occurs within the confined space due to curtailment of their rotational freedom. Although phosphorescence could also be observed when these thioketones are included in open containers, such as cucurbiturils and cyclodextrines, the closed container made up of octa acid is found to be the best medium to observe phosphorescence from thioketones whose excited state chemistry is essentially controlled by self-quenching.
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U2 - 10.1021/jp911698s
DO - 10.1021/jp911698s
M3 - Article
C2 - 20356085
AN - SCOPUS:78650116517
VL - 114
SP - 14320
EP - 14328
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
SN - 1520-6106
IS - 45
ER -