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Combination of calix[4]arenes functionalized at the upper rim at the 5- and 17-positions with amino and formyl groups, respectively, gives a new series of "head-to-head" linked double calix[4]arenes in nearly quantitative yield. The X-ray structure of a modified double calix[4]arene is reported. The novel, highly preorganized receptor molecules complex silver(I) ions (K(ass) = 9.5 x 10(5) M(-)(1) in CDCl(3)); the selectivity of complexation was studied by supported liquid membrane transport experiments and chemically modified field effect transistor measurements.

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Reaction of tetrazolyl enolate 2 (HL2) with Cu(II) acetate yields the 3D‐coordination polymer 4 ([CuL22]n). the structure of which is unequivocally established by single‐crystal X‐ray diffraction. The formation of 4 is understandable if 2 or its enolate is considered as tridentate chelate ligand and if an intermediate formation of the coordinatively unsaturated copper(II) building block 6 is assumed. The monomers 6 are bidentate coordinating by the two CN groups, which leads to linking of monomers and to coordinative saturation at the copper(II) center of 6 with formation of three‐dimensional 4. Semicorrin 8 (HL4), however, reacts with Fe(II) to give the exceptional mononuclear tetrahedral chelate complex 10 (X‐ray). EPR and Mössbauer spectra of 4 and 10 are discussed.