Triphenylamine‐Based Pyridine N‐Oxide and Pyridinium Salts for Size‐Selective Recognition of Dicarboxylates

Triphenylamine‐based receptors 1 – 3 have been designed and synthesized for the recognition of dicarboxylates. The correct dispositions of the binding groups in both 1 and 2 under 4,4′‐dicarbonyltriphenylamine spacer enable them to bind aliphatic dicarboxylates of different chain lengths with moderate binding constant values. In the binding event, triphenylamine‐based pyridinium salt 2 is found to be more effective than triphenylamine‐based pyridine N ‐oxide 1 and shows selectivity for long‐chain pimelate. Binding takes place at charged sites with concomitant PET‐based (photo‐induced electron transfer) quenching of emission of triphenylamine motif. The binding was monitored in DMSO using 1 H NMR, UV/Vis and fluorescence spectroscopic methods. Efficiency of pyridinium binding site over the others in the present study has been rationalised by invoking theoretical results. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)