Synthesis of mono-, di- and tetra-alkyne functionalized calix[4]arenes: reactions of these multipodal ligands with dicobalt octacarbonyl to give complexes which contain up to eight cobalt atoms.

The functionalized mono-alkyne cone-monopropargyl p-tert-butylcalix[4]arene was synthesized by the reaction of p-tert-butylcalix[4]arene with K(2)CO(3) and 3-bromo-1-propyne. More prolonged reaction times led to the formation of the 1,3 cone bis(propargyl)calix[4]arene . The tetra-alkyne species cone-tetrapropargyl p-tert-butylcalix[4]arene and its conformational isomer, 1,3-alternate-tetrapropargylcalix[4]arene may both be prepared via related reaction sequences. The structures of the molecules and were both re-determined by single crystal X-ray diffraction studies. All four functionalized calixarenes react rapidly with dicobalt octacarbonyl to give [(calix[4]arene).{Co(2)(CO)(6)}(n)] species (n = 1, 2 or 4) in which the alkyne functionalities of the propargylcalix[4]arenes are ligated to one or more [Co(2)(CO)(6)] groups. Two products could be harvested from the reaction of [Co(2)(CO)(8)] with the bis-propargyl-calixarene , depending on the reaction conditions and relative molar quantities of the reactants: complex , [1,3-cone bis(propargyl)calix[4]arene.{Co(2)(CO)(6)}(2)], in which each alkyne group is bonded to a [Co(2)(CO)(6)] group, and complex , [1,3-cone bis(propargyl)calix[4]arene.{Co(2)(CO)(6)}], which contains a unligated alkyne and an alkyne group bonded to a Co(2)(CO)(6) unit. The structures of the tetracobalt and octacobalt complexes and were established by single crystal X-ray diffraction studies.

Calix[4]arene-based, Hg2+ -induced intramolecular fluorescence resonance energy transfer chemosensor.

A novel calix[4]arene-based chemosensor 1 based on Hg2+-induced fluorescence resonance energy transfer (FRET) was synthesized, and its sensing behavior toward metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg2+ to a CH3CN solution of 1 gave a significantly enhanced fluorescence at approximately 575 nm via energy transfer (FRET-ON) from the pyrenyl excimer to a ring-opened rhodamine moiety. In contrast, addition of Al3+ induced a distinct increase of pyrenyl excimer emission ( approximately 475 nm), while no obvious FRET-ON phenomenon was observed. Different binding behaviors of 1 toward Hg2+ and Al3+ were also proposed for the interesting observation.

Self-inclusion in 5,11,17,23-tetra-tert-butyl-26,27,28-trihydroxy-25-(methoxycarbonylmethoxy)calix[4]arene chloroform trisolvate.

The title compound, C(47)H(60)O(6).3CHCl(3), is the first example of a lower-rim mono-ester calixarene derivative to be crystallographically characterized. The cone conformation adopted by the macrocycle is stabilized by three intramolecular hydrogen bonds. Self-inclusion of the methyl ester chain in the cavity of an adjacent molecule gives rise to infinite chains parallel to the c axis. C-H...pi interactions involving the methyl group most imbedded in the cavity contribute to the stabilization of the system.