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Exceptionallyflexible inclusion compound having three-dimensional(3D) solvent-accessible voids was built from single 1,3-ethylene diamidebridged p-tert-butyl-calix[4]arene. The robustnessof the crystalline order originates from a fascinating square-gridframework of open molecular capsules that is built entirely from vander Waals forces and weak hydrogen bonding. Yet, its flexibility isinduced by a controlled solvent-directed “breathing behavior”.The 3D network of channels generates extrinsic voids sufficientlyelastic to trap different sizes of alcohol molecules. Careful extractionof solvent from these voids produces 3D nanoporous molecular crystalswith controlled pore size. [ABSTRACT FROM AUTHOR]

Abstract: Attaching azacrown bridges on calixarene platform generates calix(aza)crown family. This article reviews synthetic routes for their design and discusses their ion-binding properties by means of coordination and stability constants. [Copyright &y& Elsevier]

Abstract: Both the consequences of 1,3-cyclization of calix[4]arenes by diamide formation, and the effect of 2- and 2,4-alkoxycarbonylmethylation of two 1,3-bridged calix[4]azacrowns on their metal ion-binding capacities have been studied by synthesis of the derivatives in their cone conformation and measurement of the stability constants for their complexation in a range of alkaline earth and transition metal cations. In these two cases, the conformation of the ligand in the solid state has been defined in detail by a crystal structure determination. In the first case, a tubular architecture performing methanol channels is displayed, however, in the second case a zigzag architecture generated by a chloroform network connecting calixarene molecules is present. Speciation in solution appears to be limited to the formation of 1:2 and/or 1:1 and/or 2:1 (M–L) complexes, depending on the system, with values of the stability constants determined by absorption spectroscopy in acetonitrile, lying in the ranges log β 12 ca. 10, log β 11 ca. 2–5, and log β 21 ca. 7–9. There is evidence for selectivity toward Cu(II) and for some unexpected anion effects. None of these ligands appear to be an efficient extractant for the metals as their picrate. [Copyright &y& Elsevier]

Two calix[4]azacrowns, capped with two aminopolyamide bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log β11 ≈ 5–6 and log β12 ≈ 10. The structural changes of the ligands upon La(III) complexation were probed by ¹H NMR spectroscopy. The two ligands were observed to have opposite fluorescence behaviors, namely, fluorescence enhancement (via blocking of photoinduced electron transfer from amine groups) or quenching (via lanthanide-chromophore interactions) upon metal ion complexation. Long-lived lanthanide luminescence was sensitized by excitation in the π,π* band of the aromatic moieties of the ligands. The direct involvement of the antenna triplet state was demonstrated via quenching of the ligand phosphorescence by Tb(III). Generally, Eu(III) luminescence was weak (Φlum ≤ 0.01%) and much shorter lived (τlum = 0.36 ms) than the Tb(III) emission. The latter, on the other hand, reached lifetimes of up to 2.60 ms and quantum yields as high as 12% for one of the ligands. Water/deuterium oxide exchange experiments showed the presence of only one solvent molecule in the coordination sphere of the lanthanides. However, Eu(III) luminescence was efficiently quenched by NH oscillators and the presence of a ligand-to-metal charge transfer state. Near-infrared luminescence of Nd(III) was also generated by energy-transfer sensitization. [ABSTRACT FROM AUTHOR]

Review: 103 refs. [ABSTRACT FROM AUTHOR]