Incarcerated excited states

They observed major differences in the photophysical properties of CA upon incarceration. The surrounding host lead to a red-shift of the absorption spectrum and reduced the 

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In Pina s work, 2,3-butanedione is trapped inside hemicarcerand 63 to give the corresponding hemicarceplex, and the reactions with several electron donors are investigated in order to elucidate the effect of the encapsulation on the rates of the electron transfer to the triplet excited state of the guest. The determination of phosphorescence quenching lifetimes of free and incarcerated 2,3-butanedione reveals that quenching for uncomplexed 2,3-butanedione occurs at the diffusion-controlled limits for any donor quencher (e.g., amines), whereas in the case of the encapsulated substrate the rate constants are lower (ranging between 3.5 x 10 and 4 X 10 s ) and display an approximately linear dependence upon the oxidation potential of the external quencher. In particular, rate constants decrease with the... 

In section 9.3.2, we have seen that spectral shifts of incarcerated guests can provide insight into the electronic and spatial characteristics of the inner phase. Of special interest to the photophysical community are also excited state lifetimes of molecules enclosed in constrained media. Investigation of these systems may lead to the development of novel photophysical probes for immunoassays and devices for information storage or solar-energy conversion. Parola et al. investigated the photophysical properties of 9-cyanoanthracene (CA) inside hemicarcerand 26 (Figures 9.3 and 9.34). ... 

Equations 9.1 and 9.2 schematically describe energy and electron transfer quenching of an incarcerated triplet excited state HostOG(Tl) with a bulk phase quencher Q " ... 

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