Controlling photochemical and photophysical behavior of organic molecules within a water soluble host

In this study we have investigated the possibility of controlling photochemical and photophysical behavior of small organic molecules by encapsulation within the cage of a deep-cavity cavitand, octa acid. Octa acid is soluble in basic aqueous medium and its interior cavity is benzene like which enable it to encapsulate small organic molecules forming host-guest complexes. The nature and stoichiometry of these complexes depend upon the size and hydrophobicity of the guest molecules. We have shown that the excited state dynamics of green fluorescent protein (GFP) chromophore derivatives can be controlled by encapsulation within octa acid. Octa acid can also selectively stabilize high-energy cisoid conformer of 1,4-diaryl-1,3-butadienes. We have demonstrated that a triplet-triplet energy transfer could occur where the donor and acceptor are encapsulated within two different molecular container of octa acid. The association-dissociation dynamics of supramolecular capsular assemblies and formation of a hetero-capsular assembly were also studied. The work includes synthesis of gold nanoparticle (AuNP) stabilized with thiol functionalized deep cavity cavitand followed by their characterization. The photophysical studies showed that AuNP can influence the phosphorescence emission of guest molecules situated at close proximity through the formation of host-guest complexes with the cavitand bound on AuNP surfaces.