The singlet-quintet transition in Tris[2-(pyridin-2-yl)benzothiazole]iron(II) Bis(tetraphenylborate)

1984 ◽  
Vol 37 (6) ◽  
pp. 1157 ◽  
Author(s):  
AT Baker ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Spectral Data ◽  
Magnetic Moment ◽  
Spin Transition ◽  
Empirical Treatment ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Thiazole Derivative

The tris[2-(pyridin-2-yl)benzothiazole]iron(II) ion has been isolated as the tetraphenylborate salt which is stable in the atmosphere for short periods. The deep red complex displays a temperature-dependent magnetic moment and thermochroism which are associated with a thermally induced singlet (1A1) ↔ quintet (5T2) spin transition. An empirical treatment of the transition, which is continuous, yields ∆H and ∆S values of 22.7 kJ mol-1 and 91 JK-1 mol-1 over the range 275-364 K. Spectral data for the corresponding nickel(11) complex confirm the intermediate nature of the field strength of the benzothiazole and indicate that it is a weaker ligand than the corresponding thiazole derivative.

Steric Effects of the Spin State of Iron(II) in Complexes of Substituted Bipyridine Derivatives

1991 ◽  
Vol 44 (11) ◽  
pp. 1539 ◽  
Author(s):  
D Onggo ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Spectral Data ◽  
Thermal Equilibrium ◽  
Steric Effects ◽  
Spin States ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Thermally Induced ◽  
Infrared Spectral ◽  
Derivatives Of

Iron(II) and nickel(II) complexes of dimethyl 2,2′-bipyridine-3,3′-dicarboxylate (dmbc), 1,1′-biisoquinoline (biq), 6,6′-dimethyl-2,2′-bipyridine (dmbpy) and 4,4′6,6′-tetramethyl-2,2′- bipyridine (tmbpy) have been prepared. [FeN6]2+ derivatives of dmbc and biq were isolated as solid salts. These show anomalous temperature dependence of their magnetism and Mossbauer spectra which has been interpreted in terms of a thermally induced singlet (1A1) ↔ quintet (5T2) transition. The transition is also observed for [Fe(biq)3][BF4]2 in solution and has been analysed in terms of a thermal equilibrium involving the two spin states. Electronic spectral data for the [NiN6]2+ derivatives indicate values for the field strength of these ligands which are consistent with the appearance of the transition in the iron(II) species. Both dmbpy and tmbpy yield only bis(ligand) complexes with either iron(II) or nickel(II). Infrared spectral data suggest that in these complexes the associated perchlorate or fluoroborate anions are coordinated, which leads to distorted six-coordinate structures. A similar iron(II) complex was isolated with 2,9-dimethyl-1,10-phenanthroline.

Metal-Complexes of 1,10-Phenanthroline Derivatives. XV. Complexes of 2-(3,5-Dimethylpyrazol-1-yl)-1,10-phenanthroline

1988 ◽  
Vol 41 (6) ◽  
pp. 873 ◽  
Author(s):  
AS Abushamleh ◽  
HA Goodwin
Keyword(s):  
Magnetic Properties ◽  
Solid State ◽  
Spectral Data ◽  
High Spin ◽  
Nickel Complex ◽  
Spin Transition ◽  
Critical Value ◽  
Magnetic Data ◽  
Strong Temperature Dependence ◽  
Thermally Induced

Iron(II) and nickel(II) bis ( ligand ) complexes of 2-(3,5-dimethylpyrazol-1-yl)-1,10-phenanthroline (L) have been prepared. The field strength of L as determined from spectral data for the nickel complex is in the range encompassing the critical value at the singlet (1A1) ↔ quintet (5T2) crossover for iron(II). The magnetic properties of the iron(II) complex both in solution and in the solid state are anomalous, and indicative of the occurrence of a thermally induced spin transition. Mossbauer spectral data confirm this, and reveal separate contributions from the singlet and quintet species with a strong temperature-dependence of their relative intensities. Magnetic data for the complex in solution are consistent with a simple high spin ↔ low spin equilibrium, and lead to values of ΔH = 23�0.5 kJ mol-1 and ΔS = 66�5 J K-1 mol-1 for the low spin → high spin transformation.

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)°.

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.

Iron(II) Mononuclear Materials Containing Functionalised Dipyridylamino-Substituted Triazine Ligands: Structure, Magnetism and Spin Crossover

2012 ◽  
Vol 65 (7) ◽  
pp. 874 ◽  
Author(s):  
Hayley S. Scott ◽  
Tamsyn M. Ross ◽  
Stuart R. Batten ◽  
Ian A. Gass ◽  
Boujemaa Moubaraki ◽  
...  
Keyword(s):  
Field Strength ◽  
Crystal Field ◽  
Spin Crossover ◽  
Spin Transition ◽  
Magnetic Behaviour ◽  
Crossover Effect ◽  
Thermally Induced ◽  
Crystal Field Strength ◽  
Nitrogen Donor ◽  
Packing Interactions

The spin crossover effect in iron(II) materials containing the di-2-pyridylamine functional group has been investigated for the new nitrile-functionalised ligand DTAC (2,2′,2″,2″′-((6-(di(pyridin-2-yl)amino)-1,3,5-triazine-2,4 diyl)bis(azanetriyl))tetra acetonitrile). This ligand has successfully been incorporated into a family of materials of the general formula trans-[Fe(DTAC)2(anion)2], wherein we have systematically varied the trans-nitrogen donor anion from NCS, NCSe, N(CN)2 (dca; dicyanamide) to NCBH3 – thus forming the four mononuclear materials trans-[Fe(DTAC)2(NCS)2]·6MeCN (1), trans-[Fe(DTAC)2(NCSe)2]·6MeCN (2), trans-[Fe(DTAC)2(N(CN)2)2] (3) and trans-[Fe(DTAC)2 (NCBH3)2]·3MeCN (4)). We find that the materials with a weaker crystal field strength anion remain high spin over all temperatures (1 and 2) whereas the materials containing stronger crystal field strength anions undergo a thermally induced spin crossover (3 and 4). Structural analysis revealed that the packing interactions in the solid state and the degree of solvation also play a large role in the observed magnetic behaviour. Indeed, aged or rapidly precipitated samples of 2 show a spin transition above room temperature.

scholarly journals Solvent-induced on/off switching of intramolecular electron transfer in a cyanide-bridged trigonal bipyramidal complex

2016 ◽  
Vol 45 (43) ◽  
pp. 17104-17107 ◽  
Author(s):  
Rong-Jia Wei ◽  
Ryohei Nakahara ◽  
Jamie M. Cameron ◽  
Graham N. Newton ◽  
Takuya Shiga ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Spin Transition ◽  
Intramolecular Electron Transfer ◽  
Thermally Induced ◽  
Trigonal Bipyramidal ◽  
Transition Behaviour

A cyanide-bridged trigonal bipyramidal [Co3Fe2] cluster shows solvent-driven reversible on/off switching of its thermally induced electron-transfer-coupled spin transition behaviour.

Ternary Antimonides RE4T7Sb6 (RE=Gd–Lu; T =Ru, Rh) with Cubic U4Re7Si6-type Structure

2013 ◽  
Vol 68 (9) ◽  
pp. 971-978 ◽  
Author(s):  
Inga Schellenberg ◽  
Ute Ch. Rodewald ◽  
Christian Schwickert ◽  
Matthias Eul ◽  
Rainer Pöttgen
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystal ◽  
Magnetic Moment ◽  
Induction Furnace ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Antiferromagnetic Ordering ◽  
Arc Melting ◽  
Intermediate Valent

The ternary antimonides RE4T7Sb6 (RE=Gd-Lu; T =Ru, Rh) have been synthesized from the elements by arc-melting and subsequent annealing in an induction furnace. The samples have been characterized by powder X-ray diffraction. Four structures were refined on the basis of single-crystal X-ray diffractometer data: U4Re7Si6 type, space group Im3m with a=862.9(2) pm, wR2=0.0296, 163 F2 values for Er4Ru7Sb6; a=864.1(1) pm, wR2=0.1423, 153 F2 values for Yb4Ru7Sb6; a=872.0(2) pm, wR2=0.0427, 172 F2 values for Tb4Rh7Sb6; and a=868.0(2) pm, wR2=0.0529, 154 F2 values for Er4Rh7Sb6, with 10 variables per refinement. The structures have T1@Sb6 octahedra and slightly distorted RE@T26Sb6 cuboctahedra as building units. The distorted cuboctahedra are condensed via all trapezoidal faces, and this network leaves octahedral voids for the T1 atoms. The ruthenium-based series of compounds was studied by temperature-dependent magnetic susceptibility measurements. Lu4Ru7Sb6 is Pauli-paramagnetic. The antimonides RE4Ru7Sb6 with RE=Dy, Ho, Er, and Tm show Curie-Weiss paramagnetism. Antiferromagnetic ordering occurs at 10.0(5), 5.1(5) and 4.0(5) K for Dy4Ru7Sb6, Ho4Ru7Sb6 and Er4Ru7Sb6, respectively, while Tm4Ru7Sb6 remains paramagnetic. Yb4Ru7Sb6 is an intermediate-valent compound with a reduced magnetic moment of 3.71(1) μB per Yb as compared to 4.54 μB for a free Yb3+ ion

Basic Chromium(III) Formate: Reaction of Chromiiim(III) Chloride with Formic Acid

1979 ◽  
Vol 34 (2) ◽  
pp. 160-162 ◽  
Author(s):  
R. C. Paul ◽  
P. Kapoor ◽  
. B. Baidya ◽  
R. Kapoor
Keyword(s):  
Formic Acid ◽  
Spectral Data ◽  
Magnetic Moment ◽  
Title Compound ◽  
Temperature Range ◽  
Infrared Spectral ◽  
Anhydrous Formic Acid

Abstract Chromium(III) Chloride, Basic Chromium(III) Formate, IR, Thermogravimetry, Magnetic Moment Chromium(III) chloride reacts with anhydrous formic acid to give basic chromium(III) formate [Cr3O(OOCH)6(H2O)2(HCOOH)](OOCH), HCOOH. Its reactions with bases (B) give compounds of the general composition [Cr30(C00CH)6(B)3](00CH). The title compound has been characterized by infrared spectral data, temperature range (266-110K) magnetic moment and thermogravimetry.

Iron(II) and Nickel(II) Complexes of 2,6-Di(thiazol-2-yl)pyridine and Related Ligands

1991 ◽  
Vol 44 (8) ◽  
pp. 1041 ◽  
Author(s):  
AT Baker ◽  
P Singh ◽  
V Vignevich
Keyword(s):  
High Spin ◽  
Room Temperature ◽  
Spin Transition ◽  
Magnetic Behaviour ◽  
Diethyl Acetal ◽  
Thermally Induced ◽  
Field Strengths

2,6-Di(thiazol-2-yl]pyridine (1a), 2,6-di(4-methylthiazol-2-yl)pyridine (1b) and 2,6-di(2-imid-azolin-2-yl)pyridine (3) have been prepared by the reaction of pyridine-2,6-dicarbothioamide with bromoacetaldehyde diethyl acetal, bromoacetone and ethylenediamine, severally. Bis ( ligand ) iron(II) and nickel(II) complexes of all ligands have been prepared. The bis ( ligand ) iron(II) complexes of (1a) and (3) are low-spin whereas that of (1b) is high-spin at room temperature and undergoes a thermally induced spin transition. The field strengths of the ligands , determined from the spectra of their nickel(II) complexes, correlate well with the observed magnetic behaviour of their iron(II) complexes. The field strengths of (1a) and (1b) are found to be marginally less than those of the isomeric ligands 2,6-di(thiazol-4-yl)pyridine (2a) and 2,6-di(2-methylthiazol-4-yl)pyridine (2b).

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