Sulphur-nitrogen chelating agents. VIII. Magnetic behaviour of some cobalt(II) complexes at the crossover region

1969 ◽  
Vol 22 (9) ◽  
pp. 1825 ◽  
Author(s):  
PSK Chia ◽  
SE Livingstone
Keyword(s):  
Field Strength ◽  
Thermal Equilibrium ◽  
Chelating Agents ◽  
Magnetic Behaviour ◽  
Ligand Field ◽  
Crossover Region ◽  
Methyl Group ◽  
Quantitative Treatment

The bis-ligand cobalt(II) complexes of 6-methylpyrid-2-yi-N-(2?- methylthio-phenyl)methyleneimine (SNNMe) are spin-free and the corresponding complexes of 2-pyridyl-N-(2?- methylthiophenyl)methyleneimine (SNN) are spin-paired. This difference in magnetic behaviour arises from a lower effective ligand field strength of SNNMe, presumably due to the steric inter-ligand interference introduced by the methyl group in the 6-position of SNNMe. The moments of the cobalt(II) complexes are dependent on temperature and the departures from the Curie-Weiss law are quite anomalous. No quantitative treatment is given for the anomalous magnetic behaviour; however, the results are best explained as a thermal equilibrium between the nearly equi-energetic spin-paired and spin-free states of the cobalt(II) atom.

The magnetic properties of the Tris(2-methyl-1,10-phenanthroline)iron(II) ion

1968 ◽  
Vol 21 (1) ◽  
pp. 83 ◽  
Author(s):  
HA Goodwin ◽  
RN Sylva
Keyword(s):  
Magnetic Properties ◽  
Thermal Equilibrium ◽  
Magnetic Moments ◽  
Anomalous Behaviour ◽  
Ligand Field ◽  
Temperature Dependent ◽  
Methyl Group ◽  
Temperature Range ◽  
Effective Strength

The magnetism of the salts [Fe mephen3]X2 (X = I-, ClO4-, BF4-, PF6-; mephen = 2-methyl- 1,l0-phenanthroline) has been investigated over the temperature range c. 100-300�K. The compounds exhibit anomalous behaviour, and this has been qualitatively interpreted as being the result of the presence of nearly equi-energetic ground terms 1A1 and 5T2 of the complexed iron(11) ion, a thermal equilibrium between these terms causing the magnetic moments to be markedly temperature dependent. This behaviour is apparently the result of the sterie hindrance to the coordination of an iron(11) ion induced by the presence of the methyl group in the ligand and the consequent lowering of the effective strength of the ligand field. The colour of the salts varies with temperature, and this has been discussed in terms of π-bonding between the iron(11) ion and the ligand.

Thio derivatives of β-diketones and their metal chelates. X. The anomalous paramagnetism of some iron(III) chelates of monothio-β-diketones

1968 ◽  
Vol 21 (8) ◽  
pp. 1987 ◽  
Author(s):  
RKY Ho ◽  
SE Livingstone
Keyword(s):  
Iron Atom ◽  
Thermal Equilibrium ◽  
Room Temperature ◽  
Magnetic Behaviour ◽  
The Other ◽  
Ligand Field ◽  
Pairing Energy ◽  
Temperature Dependent ◽  
Magnetic Susceptibilities ◽  
Derivatives Of

The magnetic susceptibilities of the iron(111) chelates Fe(R1CS=CHCOR2)3 (R1 = Ph, p-MeC6H4, p-MeOC6H4, p-BrC6H4, 2-thienyl, 2-furyl, R2 = CF3; R1 = Ph, R2 = Ph, OEt) have been investigated over a temperature range. The iron(111) complex of ethyl thiobenzoylacetate (R1 = Ph, R2 = OEt) is of the high-spin type and obeys the Curie-Weiss law with θ =-8�k. The moments of the other complexes vary between 2.31 and 6.61 B.M. at room temperature and are temperature-dependent, ranging from 1.86 to 4.07 B.M. at 80�k, depending on the nature of R1 and R2 This behaviour is postulated to be due to a thermal equilibrium between the nearly equi-energetic spin-paired (t5/2g) and spin-free (t3/2ge2/g) configurations of the iron atom, resulting from the approximately equal magnitudes of the ligand field (Δ) and the pairing energy (π) in these complexes. The ligand field and consequently the magnetic behaviour are sensitive to the nature of R1 and R2: electron-withdrawing groups appear to be the most effective in increasing the population of the spin-paired configuration.

Metal complexes of 1,10-phenanthroline derivatives. XII. Complexes of 2-Hydrazino-1,10-phenanthroline and related molecules

1981 ◽  
Vol 34 (2) ◽  
pp. 313 ◽  
Author(s):  
AS Abushamleh ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Metal Complexes ◽  
Spectral Data ◽  
Chelating Agents ◽  
Spin Transition ◽  
Crossover Region ◽  
Lower Field ◽  
Derivatives Of

2-Hydrazino- and 2-(N1-methylhydrazino)-1,10-phenanthroline have been prepared from 2-chloro-1,10-phenanthroline and the appropriate hydrazine. These tridentate chelating agents yield bis-(ligand) complexes with nickel(II) and iron(II). Spectral data for the nicke(II) complexes indicate that the field strength of the ligands is near the crossover region for iron(II). Magnetic and M�ssbauereffect data indicate that a 5T2 ↔ 1A1 spin transition occurs in salts of the complex of the methylhydrazine derivative, though a marked anion-dependence for this transition is observed. Benzaldehyde hydrazone derivatives of both hydrazines also yielded six-coordinate nickel (II) and iron (II) complexes, but these were of significantly lower field strength than the parent hydrazines.

The electronic spectra and magnetic behaviour of some dithiocacodylate complexes

1971 ◽  
Vol 24 (8) ◽  
pp. 1587 ◽  
Author(s):  
AT Casey ◽  
DJ Mackey ◽  
RL Martin
Keyword(s):  
Field Strength ◽  
Electronic Spectrum ◽  
Electronic Spectra ◽  
Magnetic Behaviour ◽  
The Other ◽  
Ligand Field ◽  
Ionic Character ◽  
Nephelauxetic Effect ◽  
Other Hand ◽  
Square Planar

The large nephelauxetic effect and low ligand field strength produced by the dithiocacodylate group [(CH3)2AsS2-] in complexes with Ni2+, Co2+, and Cr3+ is explained in terms of significant covalency of the metal- sulphur bonds. The Mn2+ compound, however, has properties consistent with considerable ionic character. ��� The electronic spectrum and magnetic behaviour of bisdithiocacodylato-cobalt(II) can be better interpreted in terms of tetrahedral rather than octahedral CoSx microsymmetry. On the other hand, the Ni2+ compound is square-planar and both the Mn2+ and Cr3+ compounds appear to be octahedrally coordinated by sulphur atoms.

scholarly journals Synthesis, Characterization and Photophysical Properties of a New 2,5-Di(aryl)phosphole Derivative and Their Trigonal Copper-Phosphole Complexes

2020 ◽  
Author(s):  
Neskarlys Rios ◽  
Franmerly Fuentes ◽  
Juan Manuel Garcia Garfido ◽  
Yomaira Otero
Keyword(s):  
Field Strength ◽  
Fluorescence Spectroscopy ◽  
Photophysical Properties ◽  
High Yield ◽  
Quantum Yields ◽  
Ligand Field ◽  
Emission Energy ◽  
Esi Ms

<div>A new phosphole derivative 2,5-di(2-quinolyl)-1-phenylphosphole (<b>1</b>) was synthesized by using the Fagan-Nugent method. Phosphole was obtained as an air stable solid in high yield (73%). Additionally, two new copper phosphole complexes [CuX(Phosphole)<sub>2</sub>] (X = Cl (<b>2a</b>), I (<b>2b</b>), Phosphole = <b>1</b>) have been synthesized by reaction of CuX (X = Cl, I) and phosphole derivative (<b>1</b>). All compound were characterized by NMR, ESI-MS, UV–Vis and fluorescence spectroscopy. The photophysical properties of all compounds were analyzed, UV-Vis spectra of the complexes <b>2a-b</b> shown π–π* transitions with shift very similar to the found in the free phosphole due to that their symmetrical structures inhibits efficient ILCT. We have found that the compounds <b>1</b>, <b>2a-b</b> exhibited fluorescence between 460 and 583 nm with quantum yields of Φ<sub>f</sub> = 0.04 – 0.11. The emission energy of <b>2b</b> is higher than <b>2a</b>, suggesting that λ<sub>max</sub> is affected by the ligand-field strength of the halogen ions in the complexes (I<sup>-</sup> < Cl<sup>-</sup> ).</div>

scholarly journals Synthesis, Characterization and Photophysical Properties of a New 2,5-Di(aryl)phosphole Derivative and Their Trigonal Copper-Phosphole Complexes

2020 ◽  
Author(s):  
Neskarlys Rios ◽  
Franmerly Fuentes ◽  
Juan Manuel Garcia Garfido ◽  
Yomaira Otero
Keyword(s):  
Field Strength ◽  
Fluorescence Spectroscopy ◽  
Photophysical Properties ◽  
High Yield ◽  
Quantum Yields ◽  
Ligand Field ◽  
Emission Energy ◽  
Esi Ms

<div>A new phosphole derivative 2,5-di(2-quinolyl)-1-phenylphosphole (<b>1</b>) was synthesized by using the Fagan-Nugent method. Phosphole was obtained as an air stable solid in high yield (73%). Additionally, two new copper phosphole complexes [CuX(Phosphole)<sub>2</sub>] (X = Cl (<b>2a</b>), I (<b>2b</b>), Phosphole = <b>1</b>) have been synthesized by reaction of CuX (X = Cl, I) and phosphole derivative (<b>1</b>). All compound were characterized by NMR, ESI-MS, UV–Vis and fluorescence spectroscopy. The photophysical properties of all compounds were analyzed, UV-Vis spectra of the complexes <b>2a-b</b> shown π–π* transitions with shift very similar to the found in the free phosphole due to that their symmetrical structures inhibits efficient ILCT. We have found that the compounds <b>1</b>, <b>2a-b</b> exhibited fluorescence between 460 and 583 nm with quantum yields of Φ<sub>f</sub> = 0.04 – 0.11. The emission energy of <b>2b</b> is higher than <b>2a</b>, suggesting that λ<sub>max</sub> is affected by the ligand-field strength of the halogen ions in the complexes (I<sup>-</sup> < Cl<sup>-</sup> ).</div>

Control of Ligand Field Strength through Intra- and Interligand Contact. Octahedral Iron(II) Poly(pyrazolyl)borate Complexes

1995 ◽  
Vol 34 (15) ◽  
pp. 3928-3934 ◽  
Author(s):  
Yoshiki Sohrin ◽  
Hisao Kokusen ◽  
Masakazu Matsui
Keyword(s):  
Field Strength ◽  
Ligand Field ◽  
Borate Complexes

Ligand-Field Strength and Symmetry-Restricted Covalency in CuIIComplexes - a Near-Edge X-ray Absorption Fine Structure Spectroscopy and Time-Dependent DFT Study

2015 ◽  
Vol 2015 (16) ◽  
pp. 2707-2713 ◽  
Author(s):  
Giulia Mangione ◽  
Luciano Pandolfo ◽  
Mauro Sambi ◽  
Giovanni Ligorio ◽  
Marco Vittorio Nardi ◽  
...  
Keyword(s):  
Fine Structure ◽  
Field Strength ◽  
Time Dependent ◽  
Dft Study ◽  
Ligand Field ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

Designing air-stable cyclometalated Fe(ii) complexes: stabilization via electrostatic effects

2019 ◽  
Vol 48 (2) ◽  
pp. 374-378 ◽  
Author(s):  
Daniel Charles Ashley ◽  
Sriparna Mukherjee ◽  
Elena Jakubikova
Keyword(s):  
Field Strength ◽  
Iron Complexes ◽  
Ligand Field ◽  
Electrostatic Effects

Substitution of EWGs onto the cyclometelated iron complexes electrostatically stabilizes the Fe(ii) center while still preserving the increased ligand field strength.

scholarly journals Tuning ligand field strength with pendent Lewis acids: access to high spin iron hydrides

2019 ◽  
Vol 10 (21) ◽  
pp. 5539-5545 ◽  
Author(s):  
John J. Kiernicki ◽  
James P. Shanahan ◽  
Matthias Zeller ◽  
Nathaniel K. Szymczak
Keyword(s):  
Field Strength ◽  
High Spin ◽  
Lewis Acids ◽  
Ligand Field ◽  
Acid Base ◽  
Biologically Relevant ◽  
High Spin Iron

Pendent borane Lewis acids provide an avenue for changing a ligand's field strength through acid/base interactions; this strategy was highlighted within a series of biologically-relevant high spin iron hydrides.

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