Mononuclear rare-earth tris-β-diketonato complexes RE­(tta)3dme [RE = Y (1), La (2), Dy (3), or Eu (4); Htta = 2-thenoylacetone; dme = 1,2-dimethoxyethane] react cleanly at room temperature in a 1:1 molar ratio with the heteroditopic divergent ligand 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine N-oxide (pyterpyNO) to yield RE2(tta)6(pyterpyNO) n , where n = 2 for RE = Y (5), Dy (6), or Eu (7) and n = 3 for RE = La (8). The crystal structure of 5 revealed a dinuclear compound with two pyterpyNO’s bridging through the oxygen atom in a hypodentate mode leaving the terpyridine moieties uncoordinated. Using a metal:pyterpyNO molar ratio of 2 for RE = Y (9), Dy (10), or Eu (11), it was possible to isolate the molecular complexes RE4(tta)12(pyterpyNO)2, while using a 5:3 molar ratio, the product La5(tta)12(pyterpyNO)3 (12) can be obtained. 89Y nuclear magnetic resonance spectroscopy revealed two different yttrium centers at room temperature for 9. An X-ray diffraction study of 10 showed a symmetrical tetranuclear structure resulting from the coordination of two Dy­(tta)3 fragments to the two hypodentate terpyridines of the dinuclear unit and presenting two different coordination sites for metals with coordination numbers of 8 and 9. Magnetic studies of 6 and 10 revealed the presence of an antiferromagnetic interaction between the two Dy­(III) atoms bound by the NO bridges. These compounds displayed a slow relaxing magnetization through Orbach (6) and Raman (10) processes in the absence of an applied magnetic field; the rate increased upon application of a 1 kOe field. 7 and 11 showed a bright red emission typical of Eu3+. The two complexes have similar emission properties mainly determined by the employed β-diketonato ligands.

The synthesis of dinuclear molecular complexes [Eu2(dbm)6(bipyMO)2], 1, [Tb2(dbm)6(bipyMO)2], 2, [Eu2(tta)6(bipyMO)2], 3 [Eu2(hfac)6(bipyMO)3], 4, [Tb2(hfac)6(bipyMO)3], 5 is here reported (bipyMO = 4,4′‐bipyridine N‐oxide, Hdbm = dibenzoylmethane, Htta = thenoyltrifluoroacetone, Hhfac = hexafluoroacetylacetone). The products were obtained in mild conditions and with high yields reacting anhydrous lanthanide β‐diketonates and bipyMO in 1:1 or 1.5 molar ratio in toluene. X‐ray single crystal studies on 2, 3, 4 showed that the heterotopic ligands are hypodentate, bridging the two lanthanide centres exclusively through the oxygen atom. Photoluminescence studies show bright red emissions from europium derivatives with absolute quantum yields up to 44 %.

A family of homodinuclear Ln 3+ (Ln 3+ = Gd 3+ , Eu 3+ ) luminescent complexes with the general formula [Ln 2 (β-diketonato) 6 ( N -oxide) y ] has been developed to study the effect of the β-diketonato and N -oxide ligands on their thermometric properties. The investigated complexes are [Ln 2 (tta) 6 (pyrzMO) 2 ] (Ln = Eu ( 1 ·C 7 H 8 ), Gd ( 5 )), [Ln 2 (dbm) 6 (pyrzMO) 2 ] (Ln = Eu ( 2 ), Gd ( 6 )), [Ln 2 (bta) 6 (pyrzMO) 2 ] (Ln = Eu ( 3 ), Gd ( 7 )), [Ln 2 (hfac) 6 (pyrzMO) 3 ] (Ln = Eu ( 4 ), Gd ( 8 )) (pyrzMO = pyrazine N -oxide, Htta = thenoyltrifluoroacetone, Hdbm = dibenzoylmethane, Hbta = benzoyltrifluoroacetone, Hhfac = hexafluoroacetylacetone, C 7 H 8 = toluene), and their 4,4′-bipyridine N -oxide (bipyMO) analogues. Europium complexes emit a bright red light under UV radiation at room temperature, whose intensity displays a strong temperature ( T ) dependence between 223 and 373 K. This remarkable variation is exploited to develop a series of luminescent thermometers by using the integrated intensity of the 5 D 0 → 7 F 2 europium transition as the thermometric parameter (Δ). The effect of different β-diketonato and N -oxide ligands is investigated with particular regard to the shape of thermometer calibration (Δ vs T ) and relative thermal sensitivity curves: i.e.. the change in Δ per degree of temperature variation usually indicated as S r (% K –1 ). The thermometric properties are determined by the presence of two nonradiative deactivation channels, back energy transfer (BEnT) from Eu 3+ to the ligand triplet levels and ligand to metal charge transfer (LMCT). In the complexes bearing tta and dbm ligands, whose triplet energy is ca. 20000 cm –1 , both deactivation channels are active in the same temperature range, and both contribute to determine the thermometric properties. Conversely, with bta and hfac ligands the response of the europium luminescence to temperature variation is ruled by LMCT channels since the high triplet energy (>2...