Closed nanocontainer enables thioketones to phosphoresce at room temperature in aqueous solution

Jayaraj, Nithyanandhan ; Maddipatla, Murthy V. S. N. ; Prabhakar, Rajeev ; Jockusch, Steffen ; Turro, N. J. ; Ramamurthy, V. (2010) Closed nanocontainer enables thioketones to phosphoresce at room temperature in aqueous solution The Journal of Physical Chemistry B, 114 (45). pp. 14320-14328. ISSN 1520-6106

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp911698s

Related URL: http://dx.doi.org/10.1021/jp911698s

Abstract

Thiocarbonyl compounds possess unusual photophysical properties: they fluoresce from S2, phosphoresce from T1 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.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:55868
Deposited On:19 Aug 2011 07:53
Last Modified:19 Aug 2011 07:53

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