Cation-p interactions are exploited in supramolecular chemistry, are implicated in the selective outcomes of certain reactions and can be involved in stabilising the tertiary structures of proteins. We used the fluorescence enhancement resulting from pyridinium-p interactions to probe the extent of cation-p interactions in a series of simple pyridine derivatives, and revealed a three-carbon linker (Leonard linker) gave the best fluorescent enhancement and interpreted this as to be the best intramolecular cation-p interaction construct.

Since alkylating agents are used to generate the pyridinium species we turned our attention to the detection of alkylating agents used the optimal propylene phenylalkylpyridine motif. Alkylating agents are common and versatile synthetic building blocks but present a possible environmental problem, as such the detection of low levels of alkylating agents represents an important analytical target. Upon exposure to various alkylating agents the pyridine converted to the corresponding pyridinium and fluorescence enhancements were observed.

Varying the pyridinium architecture and incorporating a boronic acid allows cation-p interactions to signal the presence of the diol pinacol. The formation of a pyridinium boronic ester from the corresponding boronic acid modulates the exiplex interaction manifesting itself as a fluorescence enhancement.

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