The synthesis of three chiral calixarene derivatives is described. One of these, an (S)-di-2-naphthylprolinol tetramer, is shown to exhibit significant ability to discriminate between enantiomers of 1-phenylethylamine (PEA) and norephedrine on the basis of the quenching of the (S)-di-2-naphthylprolinol fluorescence emission in chloroform. The chiral discrimination appears to arise from preorganization of the four (S)-di-2-naphthylprolinol substituents on the calixarene, which define a three-dimensional chiral space. The ability to measure the enantiomeric composition of PEA and norephedrine to within an error of 4.1% and 2.6%, respectively, on the basis of a single fluorescence measurement is demonstrated.

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The detection of gaseous ammonia using an optical evanescent wave sensor coated with a PVC film containing a chromogenic calixarene (nitrophenylazophenol calix[4]arene) is described. On addition of various concentrations of ammonia gas, the absorbance maximum shifts to 500 nm, which is characteristic of deprotonation of the chromogenic group. The sensitivity of the sensor to ammonia varied depending on whether the free ligand or lithium complex was used in the membrane. Intermediate sensitivities can be generated by varying the mole ratio of lithium to calixarene. The response time of the lithium complex measured at 520 nm to a 5-50 ppm change in ammonia concentration is fast (several minutes to steady state) but the signal is slow to return to the baseline when the gas is replaced by nitrogen.

A poly(viny1 chloride) (PVC) electrode containing a calix[4]arene phosphine oxide [ c ~~~x -( O C H ~C H ~P O P ~~) ~]as the ionophore which is selective for Eum in the presence of a high background of Na+ and other common ions is described. The selectivity and response of this electrode is compared with that of an electrode incorporating the tetramethyl ester calix[4]arene by injection experiments. Flow injection is also used to demonstrate the selectivity of the tetraphosphine oxide calix[4]arene for europium(nr).Calixarenes are an exceptionally interesting group of molecules for study as complexation agents for lanthanides in solution.14 These macrocycles display several features (such as availability in different cavity sizes, large numbers of donor groups, ability to have additional oxygen and nitrogen sites and combinations thereof) favourable to ion-binding of lanthanides. However, unlike alkali and alkaline-earth complexation, high selectivity among lanthanide cations is difficult to achieve. Recent work7 on new applications of chemically modified calixarenes has revealed that lower rim phosphine oxide derivatives of the type shown below have an appreciable affinity for certain lanthanides and actinides in extraction experiments from aqueous solution into dichloromethane, notably EuII', PuIv and AmrV. In view of the growing interest in the development of calixarene-based sensors we have encapsulated the p-tert-butylcalix[4]arene phosphine oxide 1 in a polymeric poly(viny1 chloride) (PVC) membrane and But B"'Paper 51056341