COMPLEXATION PROPERTIES OF CALIXARENES IN LANGMUIR FILMS AT THE WATER-AIR INTERFACE

Calixarene molecules possess very interesting properties as ligands fo r ions and small organic molecules, and are used as models for host-gu est systems. This paper reports the results of a study on the complexa tion properties of three calixarenes: p-tert-butylcalix[6]arene (CALIX 6), p-tert-butylcalix[8]arene (CALIX8) and p-tert-butylcalix[6]arene h examide (C6AM), in Langmuir films at the water-air interface, in the p resence of Na+, K+, Ca+ and [C(NH2)(3)](+) (guanidinium) and in mixed monolayers with fullerene C-60. This study shows that the calixarenes' monolayers are strongly affected by the subphase composition. The ana lysis of the spreading isotherms shows the high selectivity of CALIX6 and C6AM for caesium and guanidinium cations, respectively. The compar ison of the limiting area values with CPK model calculation shows that CALIX6 and C6AM possess a rigid truncated-cone conformation, with dif ferent orientation at the water-air interface. The limiting areas foun d for CALIX8 monomolecular films agree with a perpendicular ''pleated loop'' conformation at the water-air interface. Electronic spectra on Langmuir-Blodgett films, and also spreading isotherms, show that the C ALIX8-C-60 1:1 complex is stable at the water-air interface. The compl ex is also formed after spreading an equimolecular mixture of CALIX8 a nd C-60 on the water surface.