MONO-METALLOCENE AND BIS-METALLOCENE CALIX[4]ARENE HYDROPHOBIC RECEPTOR MOLECULES - THEIR SYNTHESIS, STRUCTURE AND ELECTROCHEMICAL PROPERTIES

The condensation of ferrocene carbonylchloride (1) with p-t-butylcalix[4]arene (2) and calix[4]arene (3), and that of cobalticinium carbonylchloride chloride (6) with 2, leads to the corresponding new redox-active bis-ferrocene calix[4]arenes (4 and 5) and the mono-substituted cobalticinium analogue 7. An X-ray diffraction study of 5 shows the calix[4]arene is in a cone conformation. Cyclic voltammetric and coulometric studies in acetonitrile reveal that 4 and 5 undergo reversible two electron oxidations at +0.90 V (versus SCE), suggesting that the two respective ferrocene moieties are oxidised in one step; 7 exhibits a reversible one electron reduction at -0.45 V. Variable temperature 1H NMR studies show 4, 5 and 7 to exist in rigid cone conformations in solution. 1H NMR complexation studies (CD3CN) showed that none of the metallocene calix[4]arene receptors form solution host-guest complexes with t-butylamine and benzylamine. © 1989