MASS-SENSITIVE SOLVENT VAPOR DETECTION WITH CALIX[4]RESORCINARENES - TUNING SENSITIVITY AND PREDICTING SENSOR EFFECTS

Preorganized calix[4]resorcinarenes forming vaselike cavities are test ed with respect to their chemical sensing capabilities as coatings on mass-sensitive devices. A synthetically modified vaselike host molecul e with a definite cavity morphology forms densely packed layers for me asurements with a SAW oscillator, In contrast to this detection of sur face phenomena with ultrathin layers, QCM resonators require bulky mic roporous coatings with a high vapor permeability. Thus, short response times are attained even for layers using hulk effects, which are nece ssary to compensate the smaller sensitivity of the QCM. A 3-fold subst itution of a basic calix[4]resorcinarene cavity with 2,3-dichloroquino xaline provides a one-side-opened structure forming a molecular entran ce for the easy access of analyte molecules. In combination with aliph atic spacers, this material fulfills the required demands of high sens itivity and short response times, and the detection of solvents in the gas phase to 2.5 ppm is realized. The sensor effects of the establish ed coatings are correlated to host-guest stabilization enthalpies whic h were calculated by force field methods. An improved thermodynamic mo del that considers entropies of condensation is tested successfully fo r the prediction of the sensor behavior.