Modulation of photophysics and photostability of cationic coumarin 1 dye upon inclusion with macrocyclic host cucurbit[7]uril

• Improvement in solubility, fluorescence intensity (24 times) and laser photostability of proton congener of coumarin 1 dye in water upon inclusion with the macrocyclic host cucurbit[7]uril (CB[7]) was observed.
• These new results on encapsulation of cationic coumarin 1 dye with CB[7] should pave the way to superior molecular probes as biological sensors and UV laser dye.

The investigations on modulated photophysics and photostability of proton congener of coumarin 1 dye (C1-NH+) upon inclusion with the macrocyclic host cucurbit[7]uril (CB[7]) were carried out. The higher solubility, binding constant and tighter inclusion geometry of the C1-NH+@CB[7] complex were confirmed than that of the complex of parent neutral coumarin 1(C1-N) molecule by absorption, steady state fluorescence, 1H NMR spectroscopy techniques and DFT molecular modeling. Photostability study of both forms of the dye@CB[7] complexes in water showed distinct behavior, upon excitation by third harmonic (at 355 nm) of a pulsed Nd:YAG laser. These new results on formation of stronger inclusion complex of the protonated coumarin 1 dye with the host CB[7], particularly significant improvement in its solubility, fluorescence intensity and photostability in water, should permit superior molecular scale aqueous biological probes, sensors and UV laser dye.

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