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The synthesis of ligand LH3 based on a disymmetrically substituted terpyridine core functionalised by a carboxylic acid in the 6-position and a bis(carboxymethyl)aminomethyl function in the 6″-position is described. The coordination behaviour of this heptadentate (4N/3O) ligand with lanthanide cations (Ln = Eu, Gd and Tb) was studied in solution showing the formation of complexes with [LnL] stoichiometry. Complexes with general formula [LnL(H2O)2] were isolated from neutral water solutions containing equimolar amounts of cations and ligands, and the complexes were characterized in the solid state (elemental analysis, IR) and in solution (mass spectrometry). The photo-physical properties of the luminescent complexes of Eu and Tb were studied in water solution by means of absorption, steady state and time-resolved emission spectroscopies. Evolution of the luminescence lifetimes of the Eu and Tb complexes in H2O and D2O reveals the presence of two water molecules coordinated in the first coordination sphere of the cations. Despite this important hydration number, the overall luminescence quantum yields of the complexes remained elevated, especially in the case of Tb (Φ = 22.0 and 6.5% respectively for Tb and Eu). Upon crystallisation the Gd complex formed dimeric species in which two gadolinium atoms are each heptacoordinated by one ligand, the coordination sphere being completed by a single water molecule and a bridging carboxylate function, pointing to different behaviours in the solid and liquid states. [ABSTRACT FROM AUTHOR]

A novel family of homodinuclear complexes of the general formula [Ln2L2(X)2] (where Ln = Nd3+, Pr3+, Sm3+and Tb3+for 1, 2, 3and 4, respectively and X, the coordinated NO3−or Cl−anion) has been synthesised from the corresponding lanthanide(III) salts with the pentadentate dianionic Schiff base ligand, H2L [N1,N3-bis(salicylideneimino)diethylenetriamine], that exhibits a N3O2donor set. Single crystal X-ray diffraction studies evidenced the isostructurality of this family of centrosymmetric neutral dinuclear entities where the Ln(III) metal centres are coupled together by two phenolato oxygen atoms belonging to two units of ligand (H2L). Interestingly, the two other phenolato groups of H2L are mono-coordinated to the metal ions. Temperature dependence (2-300K) magnetic susceptibility studies suggest the presence of an antiferromagnetic interaction operating viadouble phenolato bridges. Photoluminescence activities of the complexes have been studied and compared with their precursor ligand. All the complexes have been characterised with microanalytical and several spectroscopic techniques. [ABSTRACT FROM AUTHOR]

A new ligand based on a p - tert -butylcalix[4]arene functionalised with three 6-carboxylato-2,2′-bipyridine arms reacted with lanthanide(III) cations to form 2:2 complexes in the solid state, whereas in solution, a concentration-dependent equilibrium is observed between 2:2 and 1:1 species, as evidenced by ES-MS and metal luminescence measurements. In the X-ray molecular structure of the terbium complex two branched calixarene platforms share one pendant arm in order to provide a neutral dimeric structure which is held together by a strong hydrogen bonded network together with efficient π-π stacking of two pyridine rings belonging to each ligand. [ABSTRACT FROM AUTHOR]