Molecular design of calixarene part 4 - Synthesis of novel double-armed p-(tert-butyl)calix[4]arene-derived amides and their lead(II)(Pb2+)-selective-electrode properties

A series of novel double-armed p-(tert-butyl)calix[4]arenes. carrying benzo ylamido, 4-nitrobenzoylamido, isonicotinamido, alpha -naphthamido, acetamid o, propionamido. or butyramido groups (see 2-8, resp.) were synthesized in 80-86% yield by the reaction of the lower-rim 1,3-bis(aminoethoxy)-substitu ted calix[4]arenediol 1 with the cot-responding acylating agents. Their str uctures were established by elemental analysis, mass, IR, UV, and H-1-NMR s pectroscopy. Ion-selective electrodes (ISEs) for Ph2+ carrying 2-8 in a PVC membrane as neutral ionophore, were prepared, and their selectivity coeffi cients for Pb2+ (KPPb,Mpot) were determined against other heavy-metal ions, alkali and alkaline earth metal ions, and ammonium ions by means of the se paratesolution method. The results obtained indicated that the electrode,, based on the calix[4]arene-derived amides 2-8 as the neutral ionophores wer e all Ph-2 selective and exhibited almost theoretical Nernstian slopes, exc ept for 3 and 4. Typically, the Pb-2 -selective electrode based on 6-8 exhi bited almost Nernstian slopes for Pb-2 over a relatively wide concentration range and had a fast response time as well as a long lifetime. although th e silver ion interfered strongly. These ISEs based on 6-8 showed a relative ly good Pb2+ selectivity against most of the interfering cations examined, except for Ag+. The effect of the side-arm functions of calix[4]arene deriv atives 2-8 on the Nernstian slopes and on the selectivity coefficients for Pb2+ obtained with the Pb2+ ISEs based on 2-8 is discussed.