Influence of CB[n] complexation on the quenching of 2,4,6-triphenylpyrylium excited states by Fe²⁺ ions
2013
Montes-Navajas, Pedro | Garcia, Hermenegildo
This manuscript focuses on the influence that the addition of Fe²⁺ as electron donor quencher exerts on the photophysics of 2,4,6-triphenylpyrylium (TP⁺) depending on the formation or not of supramolecular inclusion complexes with cucurbit[n]uril (n: 7 or 8). ¹H-NMR spectroscopy does not provide evidence supporting the formation of a ternary TP⁺@CB[n]–Fe²⁺ complex. Emission quenching studies indicate that the prevalent deactivation mechanism for the quenching of TP⁺ emission by Fe²⁺ is by increasing the ionic strength of the solution, with no evidence for the occurrence of dynamic quenching. Laser flash photolysis indicates that while the triplet excited state of TP⁺ is instantaneously quenched by Fe²⁺ in the absence of CB[n], formation of the TP⁺@CB[n] inclusion complex protects TP⁺ triplet excited state from quenching, an effect that is more pronounced in the case of CB[8] due to the deeper penetration and more complete encapsulation of the heterocyclic pyrylium core inside the larger CB[8] capsule.
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