1,3-Alternate, the Smart Conformation of Calix[4]arenes

An artificial sodium ion channel from calix[4]arene in the 1,3-alternate conformation

“…Calix [4]arene-cholic acid conjugates have been shown to transport Na + across vesicle membranes with the rate constant for the 1,3-alt conformer an order of magnitude higher than the cone [24]. This agrees with other examples that suggest 1,3-alt calix [4]arenes exhibit enhanced ionophoricity [25]. In this work we report on the synthesis and behaviour of an amphiphilic 1,3-alt calix [4]arene derivative designed to probe the influence of conformation on metal ion selectivity and transmembrane transport.…”

1,3‐Alternate Calix[4]arene as a Homobinuclear Ditopic Fluorescent Chemosensor for Ag+ Ions

“…The rotation of the methylene bridges of calix[4]arene makes its conformation mobile which offers four possible conformational isomers: cone, partial cone, 1,2‐ and 1,3‐alternates 5a. Among these conformers, the 1,3‐alternate conformation, called “smart” conformation of calix[4]arene,6a has been proved as a useful scaffold for its versatility on applications, such as nanotubes,6b–c dendrimers,6d–e and molecular syringes 6f–g. 7a With symmetrical or unsymmetrical functionalization on both sides of 1,3‐alternate calix[4]arene, two binding sites as a potential ditopic ligand are provided, which can accommodate two cations with the help of phenolic oxygen or two π‐donor aromatic rings through cation–π interactions (Figure 1).…”

Polycyclic aromatic hydrocarbons as test probes to investigate the retention behavior of 1,3-alternate calix[4]arene silica-bonded stationary phases

“…The five evaluated stationary phases contain supramolecular selectors consisting of two building blocks designed to determine how its presence in close proximity influences the column properties. The first block is a calix[4]arene moiety locked in a 1,3‐ alternate conformation, which creates ordered hydrophobic channels capable to form inclusion complexes with analytes of appropriate size and shape. The second block comprises different types of aromatic moieties: naphthoyl ([CalixNph] 25,27‐bis[naphthoyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene), phenyl additionally derivatized in the para position by electron‐withdrawing substituents such as p ‐chlorobenzyl ([CalixBzCl] 25,27‐bis[ p ‐chlorobenzyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene), p ‐nitrobenzyl (CalixBzNO 2 ), and pentafluorobenzyl (CalixBzF 5 ) or aliphatic n ‐hexyl groups ([CalixHex] 25,27‐bis[hexyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene) positioned at the upper rim of the calixarene scaffold.…”