In this article, we study the behavior of an ionic liquid (IL) derived from pyridinium, 1-butyl-3-methylpyridinium tetrafluoroborate [b3mpy][BF4], in mixtures with water and with the first alkanols of the series from methanol to butan-1-ol, at the temperatures of (298.15 and 318.15) K. First, the miscibility regions with the alkanols were established at these two temperatures, determining experimentally the liquid−liquid equilibria and the upper critical solution temperature (UCST) for each binary mixture, confirming the quasiexponential variation of the UCST with the alkanol chain. The enthalpies were determined experimentally with a newly designed calorimetric cell, and the excess molar volumes were determined from densities, at (298.15 and 318.15) K. In all cases, the are positive with (d /dT)p > 0, whereas the are negative for mixtures with alkanols but positive for the mixture of IL + water. The thermal coefficient (d /dT)p > 0 was also positive in all cases. All data were correlated with a suitable polynomial equation, and the area and volume parameters of [b3mpy][BF4] were calculated. Finally, we give an interpretation of the results and of the behavior of the mixtures.

Calix[4]arenes at the upper rim substituted with two (thio)urea moieties, 2a-c and 4, or substituted with two acetamido groups, 5, adopt a pinched cone conformation in CDCl 3 solution. The pinched cone conformation is the result of diametrical, intramolecular hydrogen bonds and was studied by 1 H NMR dilution and variable-temperature experiments, NOESY spectroscopy, and FTIR experiments. The pinched cone conformation in these novel calix[4]arenes is stable in C 2 D 2 Cl 4 up to at least 120°C. The bis(ureido)calix[4]arenes 2b,c give a hydrogen-bonded dimer in the pinched cone conformation.

Calix[4]arenes diametrically substituted at the upper rim with two melamine units spontaneously form welldefined box-like assemblies in the presence of two equivalents of 5,5-diethylbarbituric acid. These assemblies, consisting of nine different components, are held together by 36 hydrogen bonds and are stable in apolar solvents at concentrations of up to 1 0 -4 M . This paper reports the first X-ray crystal structure, and the MALDI TOF mass spectra together with the complete 'H NMR spectroscopic characterization of these hydrogen-bonded assemblies. The crystal structure clearly shows that the assemblies are stereogenic, as a result of the antiparallel orientation of the two rosette motifs. Furthermore, the synthesis of twelve new l ,3-bis(melamine)calix[4]arenes carrying different numbers and types of functionalities at the upper rim is described. Detailed 'HNMR spectroscopic studies on the as-

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