Synthesis of Functionalized Calix[4]arene Ligands Incorporating BipyridineN,N′-Dioxide Chromophores and Luminescence of Their Lanthanide Complexes

Abstract

Members of a new family of lanthanide complexes of the cone‐shaped podand 1 and the barrel‐shaped cryptand 2, based on calix[4]arenes incorporating bipyridine N,N′‐dioxide chromophores, have been synthesized and characterized. The complexes were found to be stable in water and coordinating solvents. High molar absorption coefficients {ϵ = 28000 and 36000 M−1cm−1 for [Eu(1)]3+ and [Eu(2)]3+, respectively} and high metal luminescence quantum yields {Φ = 0.19 and 0.11 for [Eu(1)]3+ and [Eu(2)]3+, respectively} were obtained. The effect of OH oscillators, attached at the lower rim of the calixarenes, on the non‐radiative deactivation to the ground state has been demonstrated.

Time-Resolved Luminescence in Aqueous Solution − New Europium Labels Derived from Macro(bi)cyclic Ligands with Aminocarboxylic Units

“…[36] These results suggested that a combination of template and entropy effects was operative in this cyclization process. The formulations [Na (15)] ϩ and [Na (16)] ϩ were consistent with the Elemental analyses and spectral properties. Ester and amide participation in sodium binding was established by IR spectroscopy, comparing the solid state spectra of the complexes and those of the open chain compounds 11 and 12, in which no intramolecular H-bonding occurs.…”

“…In this macrocyclization reaction, it is interesting to note that replacement of ethyl ester groups by benzyl groups in the diamine compound (14 vs. 13) produced a better cyclization yield. As a matter of fact, treatment of dibromide 7 with the diamine 14, carried out under conditions identical to those for the formation of [Na (15)] ϩ , gave [Na (16)] ϩ in 93% isolated yield. This might be the result of restricted conformational freedom in 14, caused by the bulkier benzyl groups, and consequently a smaller loss of internal entropy in the cyclization process.…”

“…On the other hand, the 13 C chemical shift of the benzylic CH 2 signals is of particular diagnostic value and was used to distinguish between the cis and the trans configurations (benzyl group vs. carbonyl group) of the amide linkages in macrocyclic polylactams (δ ഠ 48 and 51, respectively). [37] In [Na (15)] ϩ and [Na (16)] ϩ complexes, the observation of a low field signal (δ Ն 51) for benzylic carbons indicated the presence of a conformer with both lactam groups assuming the trans configuration. This convergent arrangement of the lactam groups may be considered as the result of the interaction of the amide carbonyl groups and the sodium ion.…”

Deciphering Three Beneficial Effects of 2,2′-Bipyridine-N,N′-Dioxide on the Luminescence Sensitization of Lanthanide(III) Hexafluoroacetylacetonate Ternary Complexes

“…We have selected this ligand because 2,2 0 -bipyridine-N,N 0 -dioxide is an efficient chromophore for the sensitization of lanthanide luminescence either as such, 32,33 or when grafted onto podands 34 or calix [4]arenes. 35 Indeed, the preferred binding of Ln III ions, which are hard Lewis acids, to oxygen-donor ligands make them ideal for the design of efficient luminescent materials because high bond-valence contribution of the O-donors leads to more 4f orbital mixing and thus to luminescence enhancement. Here, a detailed analysis of the relevant sensitization parameters for Ln = Eu allows us to decipher the role of the ancillary ligand with respect to vibrational quenching removal, contribution to energy transfer, and radiative lifetime shortening resulting in the large luminescence enhancement observed when going from [Ln(hfa) 3 3 (bpyO2)] 3 0.5C 6 H 6 (1) of satisfying quality could be obtained by slow evaporation of the corresponding ternary complex in benzene.…”

Ferromagnetic coupling in a novel dicyanamide-bridged dinuclear gadolinium(III) complex [Gd2(dca)4(OH)2 (NITpPy)4] (NITpPy=4-pyridyl-nitronyl nitroxide radical)

“…The coordination chemistry of rare earth elements has attracted the interest of researchers in materials science because of their luminescence [1][2][3][4][5][6] and magnetic properties [6][7][8][9][10][11][12][13][14][15][16][17]. Due to their large magnetic moment of the most the lanthanide(III) cations together with the magnetic anisotropy makes these complexes very appealing in the preparation of magnetic materials.…”