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Several di-and tetrafunctionalized anion receptors have been synthesized by attaching 2,2,2-trifluoroethanol binding groups at the upper rim of cone calix[4]arenes using two different synthetic procedures. The best results were obtained hy treating calix[4]arene formyl derivatives with trifluoromelhyitrimethylsilane and tetra butyl ammonium fluoride in dry THF. The bistrifluoroethanol calix[4]arene receptors are able to bind anions showing selectivity for carboxylates and dihydrogenphosphate but at a lower efficiency compared to analogous receptors hearing urea, sulfonamide or activated amide binding groups. The conformational properties of the free ligands and their acelate complexes have heen investigated hy Dynamic 'H NMR, Molecular Modeling and in one case, by X-ray crystallography. CaHx[4|arenes bearing cation coordinating groups at the lower rim and 2,2,2-trifluoroethanol moieties at the upper rim behave as ditopic receptors, since they bind simultaneously cation and anion and extracts ion pairs in organic media. In one case evidence was obtained that coordination of sodium metal ion at the lower rim enhances the binding of acetate anion at the upper rim (positive allosteric effect).

The synthesis and anion binding properties of several new cone calix[4]arenes having different flexibility and tetrafunctionalized at the upper rim with various type of hydrogen bonding donor groups such as thioureas (1-3), trifluoroacetamides (4, 5) and perfluorinated alcohols ( 6 ) are reported. The results obtained show that thiourea receptors are the most effective in the complexation of all anions and that the rigid cone compound 2 is more efficient than the mobile cone analog 1 in the binding of spherical anions, whereas the reverse is true for the complexation of tetrahedral H2P0i anion.

The product ion spectra obtained by electrospray ionization (ESI) ion trap instruments exhibit a higher number of fragment ions than those achieved by other ion-trap-based systems, indicating the presence of more effective energy deposition mechanisms. This behavior can be attributed to several different reasons, among which different initial internal energy of the precursor ions, pre-activation due to collisions taking place outside the trap, different target gas mixtures inside the trap, and different ion trap geometry were considered. Data obtained from experiments using a triple quadrupole instrument, CI-ion trap, and ESI-ion trap have been compared. The results so achieved seem to indicate that the presence inside the trap of neutral molecules of the solvent employed for the ESI process have a relevant role, promoting high energy deposition in the colliding ions.

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