A p-tert-butylcalix[4]arene functionalised at its lower rim with ether-amide pendant arms acts as an inorganic–organic receptor: structural and photophysical properties of its lanthanide complexes

Abstract

The new narrow-rim functionalised receptor 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis[2-(diethylcarbamoylmethoxy) III is 9-co-ordinated, being bound to the four ether and four carbonyl functions and to a water molecule itself H-bonded to the phenolic ether functions, which rigidifies the cavity formed by the pendant arms. Additionally, an ether molecule is inserted into the hydrophobic cavity defined by the aromatic rings. Both NMR (La, Lu) and luminescence (Eu, Tb) data point to a fairly high local symmetry at the metal centre, while lifetime determinations are consistent with the co-ordination of an inner-sphere water molecule. The new ligand sensitises the luminescence of the Tb III ion (Q abs = 5.8% in acetonitrile, τ F = 1.42 ms) while the probable presence of a LMCT state severely limits such a process for Eu III : Q abs = 2.0%, τ F = 0.73 ms.

Tuning the Stoichiometry of Lanthanide Complexes with Calixarenes: Bimetallic Complexes with a Calix[6]arene Bearing Ether‐Amide Pendant Arms

“…4 indeed showed the compound adopting a cone conformation in solution, in which the four complexing arms are held together in closed proximity, thereby providing a suitable octadentate coordination site for lanthanide cations. [14] The X-ray crystal structure of the lutetium complex further showed that a water molecule was encapsulated in the cavity formed by the four dioxo-ethylene bridges (OϪC1ϪC2ϪO), with H-bonding interactions between this water molecule and the oxygen atoms. Interestingly, an elemental analysis of free A 4 bL 4 revealed the presence of one water molecule, even after the drying process.…”

“…Synthesis and Characterization of the Substituted Calixarene A 6 L 6 The branched calix [6]arene A 6 L 6 (Scheme 1) was obtained in two steps via a Williamson reaction (Scheme 2) from the brominated pendant arm ABr, synthesised as described previously, [14] and the calix [6]arene H 6 L 6 . The hexasodium derivative of calix [6]arene was prepared in toluene, demonstrating that this salt can be formed in a non-polar solvent despite the high fluxionality of calix [6] ) indicates complete functionalization of the phenoxide groups.…”

“…In addition, the crystal structure of the Lu III 1:1 complex shows the coordination cavity predisposed to further accommodate one water molecule hydrogen-bonded to the oxygen atoms of the phenol units, which rigidifies the induced cavity, and binds the metal ion. [14] The phosphanylyl-substituted calixarenes B n bL n (n ϭ 4, 6) form complexes with 1:1 and 1:2 Ln III ligand ratios having significant stability in acetonitrile, [15,16] and interesting luminescent [15,16] and 4fϪ5f separation [17] properties. Several derivatized calix [6]arenes have been tested in extraction studies [18Ϫ20] and, in our case, B 6 bL 6 proved to be a better extracting agent than B 4 bL 4 .…”

A p-tert-butylcalix[6]arene bearing phosphinoyl pendant arms for the complexation and sensitisation of lanthanide ions

“…In addition, the coordination cavity for the Ln() ion is tightened by a water molecule hydrogen bonded to the phenolic oxygen atoms and rigidifying it, so that the calixarene behaves as a good sensitiser of the Tb() luminescence. 11 Replacing the ether-amide substituents by dimethylphosphinoylmethylene pendant arms leads to B 4 bL 4 (Scheme 1), which interacts more strongly with Ln() ions, forming both 1 : 1 and 1 : 2 complexes in acetonitrile; in this case, solvent composition strongly influences the solvation state of the macrocyclic edifices. molecular mechanics and molecular dynamics calculations.…”

“…With respect to the latter, our research program has focused on calixarenes bearing either ether amide 11 or phosphinoyl 12 groups. In previous papers we have reported on the interaction between A 4 bL 4 , a p-tert-butylcalix [4]arene substituted at the narrow rim with ether-amide pendant arms (Scheme 1).…”