Fluorescent Calixarene Scaffolds for Chemosensory Applications

Although organic guest complexation properties of hydrophobic calixarene scaffolds have been known for many years, their integration into useful probes for small-molecule analytes is significantly hindered by low association constants and lack of sensitive detection methods. Early work on incorporation of calixarene molecules into conjugated systems, either fluorescent or conductive, relied on the use of pendant groups primarily at the lower rim.¹ In such systems, the hydrophobic cavities are not engaged in the overall conjugation and no response based on host-guest complexation within the cavities has been reported. In this presentation, we describe our design of fully conjugated calixarene capsules where the 3D scaffolds serve as both receptor and fluorescent reporting units (Figure 1). Such extended conjugation is achieved by selective metal-catalyzed removal of oxygen atoms from the lower rim and their replacement with triple bonds.² We will also present strategies toward incorporation these new capsules into polymeric networks to achieve signal amplification via a molecular wire mechanism.³

Finally, we will discuss methods to regulate the affinity of conjugated scaffolds toward specific analytes by changing their electronic properties. Such design allows utilization of supramolecular molecules as molecular probes operating via host-guest complexation mechanism.

¹ Yu, H; Xu, B.; Swager, T. M. J. Am. Chem. Soc. 2003, 125, 1142−1143.

² (a) Al-Saraierh, H.; Miller, D. O.; Georghiou, P. E. J. Org. Chem. 2005, 70, 8273−8280; (b) Tzadka, E.; Goldberg, I.; Vigalok, A. Chem. Commun. 2009, 2041−2043.

³ Molad, A.; Goldberg, I.; Vigalok, A. J. Am. Chem. Soc. 2012, 134, 7290–7292.