Calixphyrins are a class of hybrid molecules that lie at the structural crossroads between porphyrins and calixpyrroles. Porphyrins, long known for their versatile metal cation coordination chemistry, are macrocycles that contain only sp2-hybridized bridging meso carbon atoms within their framework. Calix[n]pyrroles, on the other hand, are porphyrin analogs that contain pyrroles bridged exclusively by sp3 meso carbon centers, and in recent years have been shown to display remarkable anion-binding properties. Calix[n]phyrins bear analogy to both the porphyrins and calixpyrroles and are macrocyclic analogs that contain a mixture of sp2- and sp3-hybridized meso carbon bridges. This leads to partial interruptions in the conjugation pathway of the molecule, introduces novel structural features, and leads to interesting anion and cation recognition properties. It also allows for modular syntheses. In the present paper, the chemistry of calix[n]phyrins, still at an early stage of exploration, is reviewed.

Self-assembled monolayers (SAMs) on glass were used as a platform to sequentially deposit fluorophores and small molecules for ion sensing. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. The resulting libraries are easily measured and show varied responses to a series of both cations and anions. This technology is transferable from the macro-to the microscale both via microcontact printing (µCP), where the fluorophore is printed onto a glass surface, and via direct attachment of the fluorophore to microchannel walls. The ease of miniaturization of this technology may make the generation of a wide variety of simple yet efficient microarrays possible.

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A novel material for sensing cations in water via fluorescence spectroscopy is presented. The material consists of a glass substrate functionalized with a series of fluorescent self-assembled monolayers. Parallel modification with pairs of fluorophore-binding molecules of monolayers formed on glass yield a library of sensitive glass substrates. Measurements of the changes in fluorescence intensity of the layers upon addition of aqueous solutions of Cu 2+ , Co 2+ , Ca 2+ and Pb 2+ confirmed the ability of the monolayer library to produce a ''fingerprint'' response for separate analytes with a high reproducibility. This new protocol for fabrication of sensitive probes in glass is suitable for array fabrication in small size substrates. Additionally, the covalent attachment of the fluorophore moieties to the monolayer allows monitoring of the integrity of the monolayer in time in contact with solutions. To the best of our knowledge this is the first example of sensing of cations in water by a self-assembled monolayer on glass.

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