Paramagnetic Complexes in Solution: The NMR Approach

Köhler, Frank H.

doi:10.1002/9780470034590.emrstm1229

Cited by 25 publications

(21 citation statements)

References 23 publications

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“…Here again, the changes in the chemical shifts mainly affect the proton signals located in the vicinity of the paramagnetic ion, bearing a significant amount of spin density. 42 …”

Section: Resultsmentioning

confidence: 99%

K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

Garnier

Jiménez

et al. 2016

Chem. Sci.

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“…Here again, the changes in the chemical shifts mainly affect the proton signals located in the vicinity of the paramagnetic ion, bearing a significant amount of spin density. 42 …”

Section: Resultsmentioning

confidence: 99%

K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

Garnier

Jiménez

et al. 2016

Chem. Sci.

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“…Ad etailed introduction to NMR spectroscopy of paramagnetic complexes is given in our previous works and elsewhere. [54][55][56][57][58][59][60][61] In the case of Ln complexesw ith diamagnetic ligands, the pseudocontact shift (pcs), which originates form magnetic dipole-dipolei nteractions betweenu npaired fe lectrons and nuclear spins, is the dominant contribution to the hyperfine shift. For Ln complexes with axial symmetry, pcs is expressed by Equation (1) (point dipole approximation), in which c ax is the axial component of the magnetic susceptibility tensor, r is the lengtho fv ector which connects the nucleusa nd the unpaired electrons and q is the angle between the vector r and the magnetic easy axis.…”

Section: Nmr Analysismentioning

confidence: 99%

Supramolecular Approach for Enhancing Single‐Molecule Magnet Properties of Terbium(III)‐Phthalocyaninato Double‐Decker Complexes with Crown Moieties

Horii

Kishiue

Damjanović

et al. 2018

Chemistry A European J

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A Tb -phthalocyaninato double-decker ([1] ) single-molecule magnet (SMM) having four 15-crown-5 moieties in one of the ligands was synthesized, and its dimerization and magnetic properties were studied in an attempt to utilize the supramolecular aggregation for enhancing the SMM properties. Aggregation of [1] to form [1 K ] in the presence of K ions was studied by using UV/Vis-NIR absorption and NMR spectroscopies. For the magnetic measurements, [1] and [1 K ] were dispersed in poly(methyl methacrylate) (PMMA). UV/Vis-NIR absorption measurements on the PMMA dispersed samples were used to track the formation of [1 K ] . Direct current (DC) magnetic susceptibility measurements revealed that there were ferromagnetic Tb-Tb interactions in [1 K ] , whereas there was no indication of ferromagnetic interactions in [1] . Upon the formation of [1 K ] from [1] and K ions, the temperature at which the magnetic hysteresis occurred increased from 7 to 15 K. In addition, the area of magnetic hysteresis became larger for [1 K ] , meaning that SMM properties of [1 K ] are superior to those of [1] . Alternating current (AC) magnetic measurements were used to confirm this observation. Magnetic relaxation times at 2 K increased 1000-fold upon dimerization of [1] to [1 K ] , demonstrating the effectiveness of using K ions to induce dimer formation for the improvement of the SMM properties.

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“…Multiple attempts to quantify the solution magnetism using the Evans method were unsuccessful (Evans, 1959); due to the low magnetic moments, only extremely small changes in chemical shift were observed and no quantitative data could be obtained. Sophisticated NMR methods are now available for the interpretation of paramagnetic complexes (Cremer & Burger, 2003;Kö hler, 2011). However, to date with these methods the NMR data could not be fitted to an equilibrium between a paramagnetic (tetrahedral) and a diamagnetic (square planar) complex, as has been done for related systems (Pignolet & Horrocks, 1969).…”

Section: Figurementioning

confidence: 99%

Structure, magnetism and colour in simple bis(phosphine)nickel(II) dihalide complexes: an experimental and theoretical investigation

et al. 2013

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The complex [1,2-bis(di-tert-butylphosphanyl)ethane-2 P,P 0 ]-diiodidonickel(II), [NiI 2 (C 18 H 40 P 2 ] or (dtbpe-2 P)NiI 2 , [dtbpe is 1,2-bis(di-tert-butylphosphanyl)ethane], is bright bluegreen in the solid state and in solution, but, contrary to the structure predicted for a blue or green nickel(II) bis(phosphine) complex, it is found to be close to square planar in the solid state. The solution structure is deduced to be similar, because the optical spectra measured in solution and in the solid state contain similar absorptions. In solution at room temperature, no 31 P{ 1 H} NMR resonance is observed, but the very small solid-state magnetic moment at temperatures down to 4 K indicates that the weak paramagnetism of this nickel(II) complex can be ascribed to temperature independent paramagnetism, and that the complex has no unpaired electrons. The red [1,2-bis(di-tert-butylphosphanyl)ethane-2 P,P 0 ]dichloridonickel(II), [NiCl 2 (C 18 H 40 P 2 ] or (dtbpe-2 P)NiCl 2 , is very close to square planar and very weakly paramagnetic in the solid state and in solution, while the maroon [1,2-bis(ditert-butylphosphanyl)ethane-2 P,P 0 ]dibromidonickel(II), [NiBr 2 (C 18 H 40 P 2 ] or (dtbpe-2 P)NiBr 2 , is isostructural with the diiodide in the solid state, and displays paramagnetism intermediate between that of the dichloride and the diiodide in the solid state and in solution. Density functional calculations demonstrate that distortion from an ideal square plane for these complexes occurs on a flat potential energy surface. The calculations reproduce the observed structures and colours, and explain the trends observed for these and similar complexes. Although theoretical investigation identified magnetic-dipole-allowed excitations that are characteristic for temperature-independent paramagnetism (TIP), theory predicts the molecules to be diamagnetic.

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Paramagnetic Complexes in Solution: The NMR Approach

Cited by 25 publications

References 23 publications

K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

Supramolecular Approach for Enhancing Single‐Molecule Magnet Properties of Terbium(III)‐Phthalocyaninato Double‐Decker Complexes with Crown Moieties

Structure, magnetism and colour in simple bis(phosphine)nickel(II) dihalide complexes: an experimental and theoretical investigation

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Paramagnetic Complexes in Solution: The NMR Approach

Cited by 25 publications

References 23 publications

K⊂{[FeII(Tp)(CN)3]4[CoIII(pzTp)]3[CoII(pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

K⊂{[FeII(Tp)(CN)3]4[CoIII(pzTp)]3[CoII(pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

Supramolecular Approach for Enhancing Single‐Molecule Magnet Properties of Terbium(III)‐Phthalocyaninato Double‐Decker Complexes with Crown Moieties

Structure, magnetism and colour in simple bis(phosphine)nickel(II) dihalide complexes: an experimental and theoretical investigation

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K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues