Anion binding, aryl-extended cyclotriguaiacylenes and an aryl-bridged cryptophane that provides snapshots of a molecular gating mechanism

作者：Holman K Travis^*; Drake Stephen D; Steed Jonathan W; Orr G William; Atwood Jerry L

来源：Supramolecular Chemistry, 2010, 22(11-12): 870-890.

DOI：10.1080/10610278.2010.514615

• cyclotriveratrylene
• cryptophane
• encapsulation
• gating
• penetrated ion pair

Cyclotriguaiacylene, (+/-)-CTG, reacted with a series of [(5-C5H5)FeII(6-chloroarenes)]+ to yield a family of aryl-extended, [(5-C5H5)FeII]+-functionalised cavitands (+/-)-23+. Crystal structures of [BF4]- or mixed [BF4]-/[PF6]- salts of these cavitands shed light on their conformational dynamics and anion binding properties. These hosts adopt conformations that project the [(5-C5H5)FeII(6-arene)]+ substituents 'up' from the rim of the cavitand, creating deep cavities that are occupied by a [BF4]- anion. Hosts (+/-)-2a-f3+ appear to show some selectivity for the formation of penetrated ion pairs with [BF4]- in preference to [PF6]-. The compounds were photochemically demetalated, giving aryl-extended CTGs (+/-)-3a-d,f. The crystal structure of (+/-)-3a reveals that the molecule forms a centrosymmetric, self-included dimer in the solid state. Cryptophanes syn-5 and (+/-)-anti-4 were synthesised by the photochemically induced demetalation of the putative metalated cryptophanes syn-4[PF6]3 and (+/-)-anti-4[PF6]3, obtained by the 'capping' of the cavitand (+/-)-2d3+ by (+/-)-CTG. Single crystal structures of five different solvates of (+/-)-anti-5 reveal host-guest encapsulated complexes that are interpreted as revealing 'snapshots' of the molecular gating process. The first crystallographically characterised example of an empty cryptophane, namely (+/-)-anti-5, reveals that this host can also readily adopt a conformation that fills the bulk of its own cavity.

• 出版日期2010