LEAD VERSUS CADMIUM SELECTIVITY OF ION-SELECTIVE ELECTRODES BASED ON THIOPHOSPHORYLATED CALIX[6]ARENE IONOPHORES

Reaction of p-tert-butylcalix[6]arene 1 with diethoxythiophosphoryl ch loride under different conditions gives mono (2), 1,3-bis- (3), 1,4-bi s- (4), and pentakis(thiophosphates) 5 in yields of 25-69%. The substi tution patterns of calix[6]arenes 3 and 4 can be determined indirectly from the corresponding, partly dehydroxylated calix[6]arenes 9 and 10 , respectively. Reaction of 1,4-bis(thiophosphate) 4 with dimethyl sul fate gives the tetramethylated calix[6]arene 6 in 42% yield, 1,3,5-Tri methyl- (13) and 1,2-dimethyl-p-tert-butylcalix[6]arene (14) react wit h diethoxythiophosphoryl chloride to give the corresponding methylated thiophosphates 7 and 8 in 37% and 81% yield, respectively. ion select ive electrodes containing thiophosphate substituted calix[6]arenes (2- 8) show the highest selectivity for Pb(II) cation (log K-Pb,Cd(Pot) = -2.65) with 1,3-bis(thiophosphate) 3.