The new narrow-rim functionalised receptor 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis[2-(diethylcarbamoylmethoxy)ethoxy]calix[4]arene (A4bL4) has been synthesised. NMR spectra show it to adopt a cone conformation in solution with a time-averaged C4v symmetry. A4bL4 reacts with trivalent lanthanide ions in acetonitrile to yield 1 ∶ 1 complexes with logK1 in the range 8.6–9.6, as demonstrated by ES-MS, 1H- and 13C-NMR data. Complexes with Ln = Eu, Gd, Tb, and Lu have been isolated and the crystal structure of [Lu(A4bL4)(H2O)](CF3SO3)3·2Et2O shows the metal ion encapsulated in the cavity formed by the four arms. LuIII 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 TbIII ion (Qabs
= 5.8% in acetonitrile, τF
= 1.42 ms) while the probable presence of a LMCT state severely limits such a process for EuIII: Qabs
= 2.0%, τF
= 0.73 ms.