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New ligand (Z)-2-(1-methyl-2-(pyridine-2-ylmethylene)hydrazinyl)benzoxazole ( L ) reacts with Fe(II) ions what results in formation of mononuclear complexes of 2:1 stoichiometry (complexes 1 and 2 ), which crystallize in the rare space group Ia–3d (No. 230) with solvent–acetonitrile–molecules in the crystal structure. Obtained complexes were studied in terms of their properties in the solid state concerning thermal stability and magnetism. N 3 -donor Schiff base type L is a strong crystal field ligand, therefore both obtained Fe(II) complexes are diamagnetic at room temperature what has been confirmed by magnetic susceptibility measurements and Mössbauer spectroscopy. However, the reversible LS ( 1 A 1 ) ↔ HS ( 5 T 2 ) spin-transitions may be observed starting above room temperature, remaining incomplete even up to 400 K. The thermal stability and electronic reflectance spectra of complexes were determined as well. [ABSTRACT FROM AUTHOR]

The first representatives of pentanuclear carbacylamidophosphate complexes of composition Ln 5 L 6 (μ-L) 4 (μ 3 -OH) 4 (μ 4 -OH) (Ln III = Eu (1), Gd (2), Tb (3), L − = dimethylbenzoylamidophosphate ion [C 6 H 5 C(O)–N–P(O)(OCH 3 ) 2 ] − ) were obtained. The single crystal X-ray analysis revealed that polynuclear core of 1 contains five europium ions, connected by the μ 3 - and μ 4 -hydroxo groups and carbacylamidophosphate ligands. Compounds 1 – 3 were found to be isostructural. Temperature dependencies of magnetic susceptibility ( χ M ) of the compounds 1 and 2 could be explained by spin-orbit coupling of Eu III ions or antiferromagnetic exchange interactions of four Gd III ions located in the base of Gd 5 pyramid, respectively. In the case of 3, the value of χ M increases with temperature decreasing from 300 K to 50 K, and then falls down during temperature decrease till 2 K. Such behavior can be explained by comparable contribution of spin-orbit coupling and exchange interactions. No signs of single-molecule magnet behavior for 3 were found at 2 K. Phosphorescence, emission and excitation spectra at 298 K and 77 K for the complexes were measured, as well as luminescence decay times were determined. The compounds 1 and 3 showed intense luminescence with decay time at 298 K equal to 0.66 and 1.44 ms respectively. Intrinsic quantum yield for 1 determined from its emission spectrum was found to be 25%. [ABSTRACT FROM AUTHOR]

Eu III and Tb III complexes with a benzoate and a tripod N 7 ligand, [Ln III (H 3 L)benzoate](ClO 4 ) 2 ·H 2 O·2MeOH (Ln III = Eu III and Tb III ; H 3 L = tris[2-(((imidazol-4-yl)methylidene)amino)ethyl]amine), were synthesized and crystallized into an isomorphous structure. Each Ln III ion is coordinated by one tripod ligand and one benzoate, resulting in a nona-coordinated capped square antiprism geometry. The solid-state emission spectra displayed sharp bands of the f–f transitions. Tb III complex exhibits a magnetic anisotropy and the ac susceptibility measurements exhibited an out-of-phase signal under 1000 G bias field, indicative slow relaxation of magnetization. [ABSTRACT FROM AUTHOR]