How Ions Arrange in Solution: Detailed Insight from NMR Spectroscopy of Paramagnetic Ion Pairs

Damjanović, Marko; Morita, Tohru; Horii, Yoji; Katoh, Keiichi; Yamashita, Masahiro; Enders, Markus

doi:10.1002/cphc.201600804

Cited by 5 publications

(2 citation statements)

References 74 publications

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“…Due to the geometric factor in Equation (1), the 1 H signals of [1Na 4 ] 4+ showed a negative paramagnetic shift. Based on previous works, the signals around −120 ppm can be reliably assigned to the aromatic α‐protons in Pc (H α Pc ) and the crownPc (H α crPc ) . From the crystal structure of [1] 0 , r and θ values of the aromatic protons were obtained for use in Equation (1).…”

Section: Resultsmentioning

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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Section: Resultsmentioning

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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“…Ishikawa et al combined paramagnetic NMR shifts and SQUID magnetization data in order to obtain LF parameters in phthalocyaninide (Pc)-based double- and triple-decker compounds. , This allowed for the prediction and validation of the SMM behavior for Pc 2 Tb, which had the highest anisotropy barrier to date and is one of the most studied SMM systems. In the last years, NMR has been applied in a growing number of studies for the investigation of SMMs and related compounds. − In this work, a purely NMR-based method for determination of the LF parameters in cyclooctatetraenide-based lanthanide double-decker complexes is described. This class of SMMs was first introduced by Long, Murugesu, and co-workers. − The methodology presented here is based on the fact that each of the 2 J + 1 substates is connected to a magnetic anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Ligand-Field Energy Splitting in Lanthanide-Based Single-Molecule Magnets by NMR Spectroscopy

et al. 2017

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A method for the experimental determination of ligand-field (LF) energy splitting in mononuclear lanthanide complexes, based purely on variable-temperature NMR spectroscopy, was developed. The application of this method in an isostructural series of anionic lanthanide bis(cyclooctatetraenide) double-decker compounds bearing large rigid substituents is demonstrated. Using the three-nuclei plot approach devised by Reilley, the isostructurality of the compound series and the identical orientation of the magnetic main axis of all Ln ions in the series Tb to Tm are demonstrated. Measurement of the H NMR spectra of partially deuterated analogues of the complexes permitted determination of the axial magnetic susceptibility anisotropies χ for all five ions in the temperature range from 185 to 335 K. For this purpose, analysis of the hyperfine shifts was combined with structural models derived from density functional theory calculations. In a final step, the temperature dependence of the χ values was used for determination of the three axial LF parameters, adapting a method employed previously for phthalocyanine-based systems. The temperature dependence dictated by the LF parameters determined by this NMR-based approach is compared to the results of recently published ab initio calculations of the system, indicating reasonable agreement of both methods. For all ions except Dy, the NMR method determines the same m ground state as the calculations and the order and energies of the excited states match well. However, the sign of the magnetic anisotropy of the dysprosium complex in the temperature range evaluated here is not correctly predicted by the published calculations but can be described accurately by the NMR approach. This shows that our experimental method for determination of the LF parameters is an ideal complementation to other theoretical and experimental methods.

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On the Synthesis and Reduction of Trigonal Halido Bis(silylamido) Metalates of Chromium to Cobalt

2021

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A series of halido bis(silylamido) metalates of chromium to cobalt is reported. Reaction of [NBu4]Br with linear metal silylamides ML2 (M=Mn−Co, L=−N(SiMe3)2, −N(Dipp)SiMe3; Dipp=2,6‐iPr−C6H3) leads to NBu4[M(Br)L2] whereas for chromium either intramolecular deprotonation (L=−N(SiMe3)2) or ligand exchange (L=−N(Dipp)SiMe3) is observed. Attempts for their reduction with KC8 showed in part the formation of linear metal(I) silylamide complexes but also degradation. In contrast, analogous compounds bearing a [K{18c6}]+ counter ion of cobalt and iron, obtained from reaction of anionic linear metal(I) complexes [M{N(SiMe3)2}2]− with allyl bromide – can be cleanly reduced. The adduct formation studies are also extended to benzyl potassium yielding [KM(Bn)L2] (M=Mn, Co) and subsequently the salt separated [K{18c6}][M(Bn)L2] using 18‐crown‐6 as sequestrating agent.

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How Ions Arrange in Solution: Detailed Insight from NMR Spectroscopy of Paramagnetic Ion Pairs

Cited by 5 publications

References 74 publications

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

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

Ligand-Field Energy Splitting in Lanthanide-Based Single-Molecule Magnets by NMR Spectroscopy

On the Synthesis and Reduction of Trigonal Halido Bis(silylamido) Metalates of Chromium to Cobalt

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