Abstract
The first use of methyl 2-pyridyl ketoxime (mepaoH) in homometallic lanthanide(III) [Ln(III)] chemistry is described. The 1:2 reactions of Ln(NO3)3·nH2O (Ln = Nd, Eu, Gd, Tb, Dy; n = 5, 6) and mepaoH in MeCN have provided access to complexes [Ln2(O2CMe)4(NO3)2(mepaoH)2] (Ln = Nd, 1; Ln = Eu, 2; Ln = Gd, 3; Ln = Tb, 4; Ln = Dy, 5); the acetato ligands derive from the LnIII—mediated hydrolysis of MeCN. The 1:1 and 1:2 reactions between Dy(O2CMe)3·4H2O and mepaoH in MeOH/MeCN led to the all-acetato complex [Dy2(O2CMe)6(mepaoH)2] (6). Treatment of 6 with one equivalent of HNO3 gave 5. The structures of 1, 5, and 6 were solved by single-crystal X-ray crystallography. Elemental analyses and IR spectroscopy provide strong evidence that 2–4 display similar structural characteristics with 1 and 5. The structures of 1–5 consist of dinuclear molecules in which the two LnIII centers are bridged by two bidentate bridging (η1:η1:μ2) and two chelating-bridging (η1:η2:μ2) acetate groups. The LnIII atoms are each chelated by a N,N’-bidentate mepaoH ligand and a near-symmetrical bidentate nitrato group. The molecular structure of 6 is similar to that of 5, the main difference being the presence of two chelating acetato groups in the former instead of the two chelating nitrato groups in the latter. The geometry of the 9-coordinate LnIII centers in 1, 5 and 6 can be best described as a muffin-type (MFF-9). The 3D lattices of the isomorphous 1 and 5 are built through H-bonding, π⋯π stacking and C-H⋯π interactions, while the 3D architecture of 6 is stabilized by H bonds. The IR spectra of the complexes are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The Eu(III) complex 2 displays a red, metal-ion centered emission in the solid state; the TbIII atom in solid 4 emits light in the same region with the ligand. Magnetic susceptibility studies in the 2.0–300 K range reveal weak antiferromagnetic intramolecular GdIII…GdIII exchange interactions in 3; the J value is −0.09(1) cm−1 based on the spin Hamiltonian Ĥ = −J(ŜGd1·ŜGd2).
Highlights
Introduction conditions of the Creative CommonsOximes are versatile organic molecules containing the >C=N-OH group, which have been extensively used as efficient reagents in analytical chemistry and as excellent ligands in inorganic chemistry
NH4 (NO3 ); the H2 O present in the mixtures of the optimized reactions (Section 3) is enough to keep the NH4 (NO3 ) byproduct soluble, and (ii) employment of distilled MeCN as solvent leads to lower yields and serious contamination of the products by ammonium nitrate
A slurry of [Dy2 (O2 CMe)62 ] (6) (0.285 g, 0.30 mmol) in MeCN was treated in the hood with 2N HNO3 (0.35 mL, 0.70 mmol HNO3 )
Summary
Oximes are versatile organic molecules containing the >C=N-OH group, which have been extensively used as efficient reagents in analytical chemistry and as excellent ligands in inorganic chemistry. One of the first uses of oximes in metal chemistry was the gravimetric determioxime form. Oximato metal complexes are central “players” in several aspects of coordination [3,4,5] and and bioinorganic chemistry, molecular magnetism [8,9,10,11], catalysis [12,13], and the bioinorganic [6,7] [6,7]. (b) the metal-mediated/promoted/assisted reactivity these [28,29,30], ligands complexes,. LnIII2 compounds continue to attract the intense attention of many chemistry groups around thearound world the because they are ideal systems forsystems providing inorganic chemistry groups world because theymodel are ideal model for answers to fundamental questions regarding the origin of a certain physical, spectroscopic, providing answers to fundamental questions regarding the origin of a certainIIIphysical, or catalytic property, i.e., if such properties the whole molecule (two Ln centers) or half of it (a single Ln ion) [47]
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