CeTiO2N oxynitride perovskite: paramagnetic 14N MAS NMR without paramagnetic shifts

14N magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of diamagnetic LaTiO2N perovskite oxynitride and its paramagnetic counterpart CeTiO2N are presented. The latter, to the best of our knowledge, constitutes the first high-resolution 14N MAS NMR spectrum collected from a paramagnetic solid material. The unpaired 4f-electrons in CeTiO2N do not induce a paramagnetic 14N NMR shift. This is remarkable given the direct Ce−N contacts in the structure for which ab initio calculations predict substantial Ce→14N contact shift interaction. The same effect is revealed with 14N MAS NMR for SrWO2N (unpaired 5d-electrons).

Analysis of reduced paramagnetic shifts as an effective tool in NMR spectroscopy

A recently introduced concept of reduced paramagnetic shifts (RPS) in NMR spectroscopy is applied here to a series of paramagnetic complexes with different metal ions, such as iron(II), iron(III) and...

Synthesis, Structure, and Magnetic Properties of Linear Trinuclear CuII and NiII Complexes of Porphyrin Analogues Embedded with Binaphthol Units

A porphyrin analogue embedded with (S)-1,1′-bi-2-naphthol units was synthesized without reducing optical purity of the original binaphthol unit. This new macrocyclic ligand provides the hexaanionic N4O4 coordination environment that enables a linear array of three metal ions. That is, it provides the square planar O4 donor set for the central metal site and the distorted square planar N2O2 donor set for the terminal metal sites. In fact, a CuII3 complex with a Cu(1)–Cu(2) distance of 2.910 Å, a Cu(1)–Cu(2)–Cu(1′) angle of 174.7°, and a very planar Cu2O2 diamond core was obtained. The variable-temperature 1H-NMR study of the CuII3 complex showed increasing paramagnetic shifts for the naphthyl protons as temperature increased, which suggests strong antiferromagnetic coupling of CuII ions. The temperature dependence of the magnetic susceptibility indicated antiferromagnetic coupling both for the CuII3 complex (J = −434 cm−1) and for the NiII3 complex (J = −49 cm−1). The linear (L)M(µ-OR)2M(µ-OR)2M(L) core in a rigid macrocycle cavity made of aromatic components provides robust metal complexes that undergo reversible ligation at the apical sites of the central metal.

Paramagnetic 14N MAS NMR without Paramagnetic Shifts: Remarkable Lattice of LaTiO2N and CeTiO2N Oxynitride Perovskites

¹⁴N magic-angle spinning (MAS) NMR spectra of diamagnetic LaTiO₂N perovskite oxynitride and its paramag-<br>netic counterpart CeTiO₂N are presented. The latter, to the<br>best of our knowledge, constitutes the first high-resolution ¹⁴N MAS NMR spectrum collected from paramagnetic solid material. Induced paramagnetic ¹⁴N NMR shift due to unpaired 4<i>f</i> -electrons in CeTiO₂N is non-existent, which is remarkable given the severe paramagnetic effects on surface proton species revealed by ¹H NMR, and direct Ce−N contacts in the structure. <i>Ab initio</i> molecular orbital calculations predict substantial Ce→¹⁴N contact shift interaction under these circumstances, therefore, cannot explain the unprecedented ¹⁴N NMR spectrum of CeTiO₂N.

Paramagnetic 14N MAS NMR without Paramagnetic Shifts: Remarkable Lattice of LaTiO2N and CeTiO2N Oxynitride Perovskites

¹⁴N magic-angle spinning (MAS) NMR spectra of diamagnetic LaTiO₂N perovskite oxynitride and its paramag-<br>netic counterpart CeTiO₂N are presented. The latter, to the<br>best of our knowledge, constitutes the first high-resolution ¹⁴N MAS NMR spectrum collected from paramagnetic solid material. Induced paramagnetic ¹⁴N NMR shift due to unpaired 4<i>f</i> -electrons in CeTiO₂N is non-existent, which is remarkable given the severe paramagnetic effects on surface proton species revealed by ¹H NMR, and direct Ce−N contacts in the structure. <i>Ab initio</i> molecular orbital calculations predict substantial Ce→¹⁴N contact shift interaction under these circumstances, therefore, cannot explain the unprecedented ¹⁴N NMR spectrum of CeTiO₂N.

Remarkable reversal of 13C-NMR assignment in d1, d2 compared to d8, d9 acetylacetonate complexes: analysis and explanation based on solid-state MAS NMR and computations

The variation in 13C NMR paramagnetic shifts as a function of d-electron configuration was explained by NMR shielding calculations.

Terbium(III) Phthalocyaninato Multiple-Decker Complexes in High Oxidation States: Correlation Between Electronic, Structural and Magnetic Properties and Unexpected Triplet Biradical States

<p>Herein we present a comprehensive study of the highly oxidized species of multiple-decker complexes composed of Tb(III) and Cd(II) ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating <i>n</i>-butoxy chains. Paramagnetic ¹H NMR measurements for the series of triple, quadruple and quintuple-decker complexes revealed that ligand oxidations lead to a decrease in magnetic anisotropy, as predicted from <i>ab initio</i> calculations. Unusual paramagnetic shifts were observed in +2<i>e</i> charged quadruple and quintuple-decker complexes, indicating that those two species are actually triplet biradicals. The X-ray structural analysis for the series of oxidized multiple-decker complexes revealed that all the species show an axial compression induced by the ligand oxidations, resulting in the bowl-shaped distortion of the ligands, in agreement with predictions from DFT calculations. Magnetic measurements revealed that the series of complexes show single-molecule magnet (SMM) properties, which are controlled by the multi-step redox induced structural changes.</p>

Terbium(III) Phthalocyaninato Multiple-Decker Complexes in High Oxidation States: Correlation Between Electronic, Structural and Magnetic Properties and Unexpected Triplet Biradical States

<p>Herein we present a comprehensive study of the highly oxidized species of multiple-decker complexes composed of Tb(III) and Cd(II) ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating <i>n</i>-butoxy chains. Paramagnetic ¹H NMR measurements for the series of triple, quadruple and quintuple-decker complexes revealed that ligand oxidations lead to a decrease in magnetic anisotropy, as predicted from <i>ab initio</i> calculations. Unusual paramagnetic shifts were observed in +2<i>e</i> charged quadruple and quintuple-decker complexes, indicating that those two species are actually triplet biradicals. The X-ray structural analysis for the series of oxidized multiple-decker complexes revealed that all the species show an axial compression induced by the ligand oxidations, resulting in the bowl-shaped distortion of the ligands, in agreement with predictions from DFT calculations. Magnetic measurements revealed that the series of complexes show single-molecule magnet (SMM) properties, which are controlled by the multi-step redox induced structural changes.</p>

Synthesis and Structures of Rare Earth 3-(4′-Methylbenzoyl)-propanoate Complexes – New Corrosion Inhibitors

A series of rare earth 3-(4′-methylbenzoyl)propanoate (mbp–) complexes [RE(mbp)3(H2O)] (RE = rare earth = Y, La, Ce, Nd, Ho, Er) have been prepared by either metathesis reactions between the corresponding rare earth chloride and Na(mbp) or protolysis of rare earth acetates by the free acid. Single-crystal X-ray diffraction studies of [RE(mbp)3(H2O)] (RE = Ce, Nd) and [Ce(mbp)3(dmso)] reveal a 1D carboxylate-bridged polymeric structure in the solid state, featuring 9-coordinate rare earth ions. X-ray powder diffraction patterns of the bulk materials indicates that all of the [RE(mbp)3(H2O)] complexes except RE = La are isomorphous. Hence, there is no structural change from the complex with RE = Ce to that with RE = Er despite the lanthanoid contraction. The 1H NMR spectra of the RE = Ho or Er complexes in (CD3)2SO show large paramagnetic shifts and broadening of the CH2 resonances, indicating the retention of substantial carboxylate coordination in solution.