Metal complexes of 1,10-phenanthroline derivatives. IX. 5T2 ↔ 1A1 spin transitions in iron(II) complexes of 2-(1,10-phenanthrolin-2-yl)thiazole derivatives

1975 ◽  
Vol 28 (1) ◽  
pp. 33 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather ◽  
FE Smith
Keyword(s):  
Metal Atom ◽  
Chelating Agents ◽  
Spin Transition ◽  
Nickel Complexes ◽  
Close Approach ◽  
Crossover Region ◽  
Thiazole Derivatives ◽  
Pyridyl Group ◽  
Spin Pairing ◽  
Experimental Temperature Range

The preparation of the tridentate chelating agents 2-(1,10- phenanthrolin-2-yl)thiazole, 2-(1,10-phenanthrolin-2-yl)-4-(2- pyridyl)thiazole 2-(1,10-phenanthrolin-2-yl)thiazolidine and 2-(1,10- phenanthrolin-2-yl)benzothiazole is described. Data from the spectra of the bis-ligand nickel complexes indicate that the ligands all have field strengths in the iron(II) crossover region. The temperature dependence of the magnetism of the bis-ligand iron(II) complexes reveals that, except for the complexes of the pyridylthiazole, a smooth, temperature-induced 5T2 ↔ 1A1 transition occurs in these compounds. For no complex is the transition complete within the experimental temperature range (83-363 K). The complex of the pyridylthiazole is high-spin throughout the range, the uncoordinated pyridyl group hindering the close approach of ligand and metal atom necessary for spin-pairing. The ability of the other ligands to induce a spin transition is primarily a consequence of distortions in the environment about the metal atom arising from coordination of the five- membered thiazole or related ring.

Metal complexes of 1,10-phenanthroline derivatives. X. 5T2 ↔ 1A1 transitions in iron(II) complexes of 2-(1,10-Phenanthrolin-2-yl)imidazole derivatives

1975 ◽  
Vol 28 (3) ◽  
pp. 505 ◽  
Author(s):  
DW Mather ◽  
HA Goodwin
Keyword(s):  
Metal Complexes ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Chelating Agents ◽  
Elevated Temperatures ◽  
Magnetic Moments ◽  
Spin Transition ◽  
Benzimidazole Derivative ◽  
Crossover Region ◽  
Experimental Temperature Range

The preparation of the tridentate chelating agents 2-(1,10- phenanthrolin-2-yl)imidazoline and 2-(1,10-phenanthrolin-2- yl)benzimidazole and their bis-ligand complexes with iron(II) and nickel(II) is described. The latter ligand coordinates as either a neutral or anionic tridentate. Data from the spectra of the nickel(II) complexes indicate that the ligands have field strengths in the iron(II) crossover region. The temperature dependence of the magnetism of the imidazoline iron(II) complex reveals a gradual, temperature- induced 5T2 ↔ 1A1 transition which is not complete within the experimental temperature range (83-363 K). Both the cationic and neutral iron(II) complexes of the benzimidazole derivative are essentially low-spin at room temperature but a significant increase in their magnetic moments at elevated temperatures indicates that a spin transition may be occurring in these compounds too.

Anomalous magnetism of iron(II) complexes of methyl-substituted pyridylthiazoles

1972 ◽  
Vol 25 (4) ◽  
pp. 715 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather
Keyword(s):  
Magnetic Properties ◽  
Temperature Dependence ◽  
High Spin ◽  
Metal Atom ◽  
Electronic Spectra ◽  
Chelating Agents ◽  
Strong Dependence ◽  
Chelating Agent ◽  
Crossover Region ◽  
Field Strengths

Bis-ligand iron(11) and nickel(11) complexes of the potentially tridentate chelating agents 2-(3-methyl-2-pyridylamino)-4-(2-pyridyl)thiazole and 2-(4-methyl- 2-pyridylamino)-4-(2-pyridyl)thiazole are described. The electronic spectra of the nickel(11) complexes show that the field strengths of the ligands are in the neighbourhood of the Crossover region for iron(11). The magnetic properties of the cationic iron(11) complexes are anomalous and consistent with a spin-equilibrium involving the nearly equi-energetic 5T2 and 1A1 states of the metal atom. The magnetism shows a strong dependence on the associated anion. 2-(6-Methyl-2-pyridylamino)-4- (2-pyridyl)thiazole is also described. In its bis-ligand iron(11) complexes it functions as a bidentate chelating agent and the complexes are high-spin. All three ligands may be deprotonated to yield inner complexes with iron(11) which in some instances have anomalous magnetic properties associated with the presence of a spin-equilibrium. 2-(6-Methyl-2-pyridyl)-4-(2-pyridyl)thiaole and its bis-ligand iron(11) and nickel(11) complexes are also described. The iron(11) complexes are high-spin and show normal temperature dependence of their magnetism.

Metal complexes of 1,10-Phenanthroline derivatives. VII. Complexes of 1,10-Phenanthroline-2-carbaldehyde hydrazones

1974 ◽  
Vol 27 (5) ◽  
pp. 965 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather
Keyword(s):  
Field Strength ◽  
Metal Complexes ◽  
High Spin ◽  
Spin State ◽  
Spin Transition ◽  
Pronounced Change ◽  
Temperature Range ◽  
Spin Pairing ◽  
Bivalent Iron ◽  
Experimental Temperature Range

A series of substituted hydrazones derived from 1,l0-phenanthroline-2-carbaldehyde and their bis-ligand complexes with bivalent iron and nickel are described. The hydrazones show a gradation in field strength and this is reflected in the spin-state of the iron complexes. The methylhydrazone complex is essentially low-spin over the temperature range 83-363 K but the presence of some spin-free species at high temperatures is evident. Within the same range the dimethylhydrazone complex is essentially high-spin but undergoes significant spin-pairing and the phenylhydrazone complex displays a complete 5T2 → 1A1 spin transition. This transition is very sharp, resulting in a pronounced change in the magnetism, and colour, of the complex within a few degrees. Complexes of the 2-pyridylhydrazone, the methylphenylhydrazone and the diphenylhydrazone are high-spin over the entire experimental temperature range.

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.

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.

Coordination of Hydrazone Derivatives of 2,2'-Bipyridine-6-carbaldehyde. Electronic and Structural Aspects of the Iron(II), Cobalt(II) and Nickel(II) Complexes

1991 ◽  
Vol 44 (3) ◽  
pp. 331 ◽  
Author(s):  
D Onggo ◽  
DC Craig ◽  
AD Rae ◽  
HA Goodwin
Keyword(s):  
Metal Atom ◽  
Magnetic Moments ◽  
Spin Transition ◽  
Azomethine Nitrogen ◽  
Ligand Molecule ◽  
Monoclinic Space Group ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Derivatives Of ◽  
Structural Aspects

Iron(II), cobalt(II) and nickel(II) [MN6]2+ type complexes of the tridentate terimine ligands 2,2′-bipyridine-6-carbaldehyde phenylhydrazone ( bph ) and 2,2′-bipyridine-6-carbaldehyde 2-pyridylhydrazone ( bpyh ) have been prepared. The electronic spectrum of the [NiN6]2+ species indicates that the field strength of these ligands is near that at the iron(II) singlet/quintet crossover. Magnetic and Mossbauer spectral data reveal that salts of [Fe( bph )2]2+ are essentially low spin, while those of [Fe( bpyh )2]2+ are high spin. Salts of [Co( bph )2]2+ have strongly temperature-dependent magnetic moments which indicate a thermally induced doublet ↔ quartet spin transition in the metal atom. The structure of [Ni( bph )2][ClO4]2 reveals meridional coordination of the tridentate units, the azomethine nitrogen of the hydrazone moiety being bound to the metal atom. There is significant twisting (8.3°) of the two pyridyl rings in each ligand molecule about the interring bridge. The [NiN6]2+ fragment is tetragonally compressed and the mean Ni-N distance is 2.09 Ǻ. [Ni( bph )2][ClO4]2 is monoclinic, space group C2/c, Z = 4, a 23.949(3), b 7.868(1), c 21.303(3)Ǻ, β 117.95(2)°.

scholarly journals Compressional behavior and spin state of δ-(Al,Fe)OOH at high pressures

2019 ◽  
Vol 104 (9) ◽  
pp. 1273-1284 ◽  
Author(s):  
Itaru Ohira ◽  
Jennifer M. Jackson ◽  
Natalia V. Solomatova ◽  
Wolfgang Sturhahn ◽  
Gregory J. Finkelstein ◽  
...  
Keyword(s):  
Solid Solution ◽  
Spin Crossover ◽  
High Pressures ◽  
Spin Transition ◽  
Heterogeneous Structure ◽  
Spin States ◽  
Hydrogen Transport ◽  
Crossover Region ◽  
Volume Collapse ◽  
Deep Interior

Abstract Hydrogen transport from the surface to the deep interior and distribution in the mantle are important in the evolution and dynamics of the Earth. An aluminum oxy-hydroxide, δ-AlOOH, might influence hydrogen transport in the deep mantle because of its high stability extending to lower mantle conditions. The compressional behavior and spin states of δ-(Al,Fe3+)OOH phases were investigated with synchrotron X-ray diffraction and Mössbauer spectroscopy under high pressure and room temperature. Pressure-volume (P-V) profiles of the δ-(Al0.908(9)57Fe0.045(1))OOH1.14(3) [Fe/(Al+Fe) = 0.047(10), δ-Fe5] and the δ-(Al0.832(5)57Fe0.117(1))OOH1.15(3) [Fe/(Al+Fe) = 0.123(2), δ-Fe12] show that these hydrous phases undergo two distinct structural transitions involving changes in hydrogen bonding environments and a high- to low-spin crossover in Fe3+. A change of axial compressibility accompanied by a transition from an ordered (P21nm) to disordered hydrogen bond (Pnnm) occurs near 10 GPa for both δ-Fe5 and δ-Fe12 samples. Through this transition, the crystallographic a and b axes become stiffer, whereas the c axis does not show such a change, as observed in pure δ-AlOOH. A volume collapse due to a transition from high- to low-spin states in the Fe3+ ions is complete below 32–40 GPa in δ-Fe5 and δ-Fe12, which i ~10 GPa lower than that reported for pure ε-FeOOH. Evaluation of the Mössbauer spectra of δ-(Al0.824(10)57Fe0.126(4))OOH1.15(4) [Fe/(Al+Fe) = 0.133(3), δ-Fe13] also indicate a spin transition between 32–45 GPa. Phases in the δ-(Al,Fe)OOH solid solution with similar iron concentrations as those studied here could cause an anomalously high ρ/νΦ ratio (bulk sound velocity, defined as K/ρ at depths corresponding to the spin crossover region (~900 to ~1000 km depth), whereas outside the spin crossover region a low ρ/νΦ anomaly would be expected. These results suggest that the δ-(Al,Fe)OOH solid solution may play an important role in understanding the heterogeneous structure of the deep Earth.

Metal complexes of 1,10-phenanthroline derivatives. VI. Complexes of iron, cobalt, nickel, and copper with 1,10-Phenanthroline-2-carbothioamide or N Phenyl-1,10-phenanthroline-2-carbothioamide

1973 ◽  
Vol 26 (12) ◽  
pp. 2623 ◽  
Author(s):  
HA Goodwin ◽  
DW Mather ◽  
FE Smith
Keyword(s):  
Temperature Dependence ◽  
Chelating Agents ◽  
Strong Field ◽  
Spin Transition ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Iron Cobalt ◽  
Phenyl Derivative ◽  
Cobalt Nickel ◽  
Thioamide Group

Mono- and bis-ligand complexes of iron, cobalt, nickel and mono-ligand complexes of copper with the tridentate chelating agents 1,10- phenanthroline-2-carbo-thioamide and N-phenyl-1,10-phenanthroline-2- carbothioamide are described. Both ligands produce a strong field with iron(II) and the bis-ligand complexes of cobalt(II) and the former display a temperature-induced spin transition resulting in an anomalous temperature-dependence of their magnetism. In all the mono-ligand complexes the metal atom is believed to be six-coordinate. Both ligands may be deprotonated in their complexes and deprotonation of the N- phenyl derivative occurs spontaneously when it interacts with cobalt(II) or copper(II), the reaction with cobalt being accompanied by oxidation of the metal. Both ligands coordinate through the sulphur atoms of the thioamide group.

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