Pyridinium calixarenes

Pyridinium salts can also be used as synthons in crystal engineering, with the electron-deficient Jt-system interacting with electron-rich aromatic systems. Whether the interactions are either intermolecular or intramolecular is determined by the substituents on the pyridinium ring, as demonstrated by the bispyridinium salts 133 <2003EJO4528> and the pyridinium-appended calixarenes 134 <2006TL181>. 

A method for introducing a pyridinium residue into a calixarene involves the... 

One of the first examples of calixarene-capped AuNPs employed for host-guest studies was published by Arduini and co-workers in 2005 [30]. The calixarene derivatives chosen for these studies were l,3-diaIkoxycalix[4]arenes, which were known to form endo-cavity inclusion complexes with tetraalkylammonium and N-alkyl pyridinium ion pairs in weakly polar solvents [31, 32]. 

Zanoni reported on the assembly of AuNPs on calixarene-based SAMs [85]. A silicon surface (Si) was functionalized with a calix[6]arene derivative bearing three undecenyl chains on the lower rim and three phenylurea moieties on the upper rim (Ce). The so-produced SAMs form stable complexes with a redox-active molecule that consists of a 4,4 -bypiridinium unit linked by a dodecyl chain to another pyridinium ring (A). This surface showed binding towards AuNPs functionalized with a calix[4]arene derivative (C4) (Fig. 37.15). The presence of the di-topic guests allows for the reversible and hierarchical assembly of the AuNPs on the Si surface. Moreover, the nanoparticles were demonstrated to be electrochemically removed from the Si/Ce/A surface. 

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