Thermally induced spin transition in tris(2-methoxy-1,10-phenanthroline)iron(II) perchlorate. Variable-temperature Moessbauer, magnetic susceptibility, and far-infrared measurements

1977 ◽  
Vol 16 (8) ◽  
pp. 1979-1984 ◽  
Author(s):  
J. Fleisch ◽  
P. Guetlich ◽  
K. M. Hasselbach
Keyword(s):  
Magnetic Susceptibility ◽  
Variable Temperature ◽  
Spin Transition ◽  
Far Infrared ◽  
Thermally Induced ◽  
Infrared Measurements

scholarly journals Time-Resolved Spectroscopy of Photo-Induced Electron Transfer in Dinuclear and Tetranuclear Fe/Co Prussian Blue Analogues

2020 ◽  
Author(s):  
Jennifer Zimara ◽  
Hendrik Stevens ◽  
Rainer Oswald ◽  
Serhiy Demeshko ◽  
Sebastian Dechert ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Prussian Blue ◽  
Variable Temperature ◽  
Spin Transition ◽  
Acetonitrile Solution ◽  
Time Resolved ◽  
Thermally Induced ◽  
Prussian Blue Analogues ◽  
Charge Transfer Dynamics

The dynamics of photo-driven charge transfer-induced spin transition (CTIST) in two Fe/Co Prussian Blue Analogues (PBAs) is revealed by femtosecond IR and UV/vis pump-probe spectroscopy. Depending on temperature the known tetranuclear square-type complex [Co<sub>2</sub>Fe<sub>2</sub>(CN)<sub>6</sub>(tp*)<sub>2</sub>(4,4’-dtbbpy)<sub>4</sub>](PF<sub>6</sub>)<sub>2</sub> (<b>1</b>) exists in two electronic states. In acetonitrile solution at <240 K the low temperature (<b>LT</b>) phase is prevalent consisting of low-spin Fe(II) and low-spin Co(III), [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>LS</sub>]<sub>2</sub>. Temperature rise causes thermally induced CTIST towards the high temperature (<b>HT</b>) phase consisting of low-spin Fe(III) and high-spin Co(II), [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>]<sub>2</sub>, being prevalent at >300 K. Photo-excitation into the intervalence charge transfer (IVCT) band of the <b>LT</b> phase at 800 nm induces electron transfer in one Fe-Co edge of PBA <b>1</b> and produces a [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>LS</sub>] intermediate which by spin crossover (SCO) is stabilized within 400 fs to a long-lived (>1 ns) [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>]. In contrast, IVCT excitation of the <b>HT</b> phase at 400 nm generates a [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>HS</sub>] species with a lifetime of 3.6 ps. Subsequent back-electron transfer populates the vibrationally hot ground state, which thermalizes within 8 ps. The newly synthesized dinuclear PBA, [CoFe(CN)<sub>3</sub>(tp*)(pz*<sub>4</sub>Lut)]ClO<sub>4</sub> (<b>2</b>), provides a benchmark of the <b>HT</b> phase of <b>1</b>, i.e. [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>], as verified by variable temperature magnetic susceptibility measurements and <sup>57</sup>Fe Mößbauer spectroscopy. The photo-induced charge transfer dynamics of PBA <b>2</b> indeed is almost identical to that of the <b>HT</b> phase of phase of PBA <b>1</b> with a lifetime of the excited [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>HS</sub>] species of 3.8 ps.

scholarly journals Time-Resolved Spectroscopy of Photo-Induced Electron Transfer in Dinuclear and Tetranuclear Fe/Co Prussian Blue Analogues

2020 ◽  
Author(s):  
Jennifer Zimara ◽  
Hendrik Stevens ◽  
Rainer Oswald ◽  
Serhiy Demeshko ◽  
Sebastian Dechert ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Prussian Blue ◽  
Variable Temperature ◽  
Spin Transition ◽  
Acetonitrile Solution ◽  
Time Resolved ◽  
Thermally Induced ◽  
Prussian Blue Analogues ◽  
Charge Transfer Dynamics

The dynamics of photo-driven charge transfer-induced spin transition (CTIST) in two Fe/Co Prussian Blue Analogues (PBAs) is revealed by femtosecond IR and UV/vis pump-probe spectroscopy. Depending on temperature the known tetranuclear square-type complex [Co<sub>2</sub>Fe<sub>2</sub>(CN)<sub>6</sub>(tp*)<sub>2</sub>(4,4’-dtbbpy)<sub>4</sub>](PF<sub>6</sub>)<sub>2</sub> (<b>1</b>) exists in two electronic states. In acetonitrile solution at <240 K the low temperature (<b>LT</b>) phase is prevalent consisting of low-spin Fe(II) and low-spin Co(III), [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>LS</sub>]<sub>2</sub>. Temperature rise causes thermally induced CTIST towards the high temperature (<b>HT</b>) phase consisting of low-spin Fe(III) and high-spin Co(II), [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>]<sub>2</sub>, being prevalent at >300 K. Photo-excitation into the intervalence charge transfer (IVCT) band of the <b>LT</b> phase at 800 nm induces electron transfer in one Fe-Co edge of PBA <b>1</b> and produces a [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>LS</sub>] intermediate which by spin crossover (SCO) is stabilized within 400 fs to a long-lived (>1 ns) [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>]. In contrast, IVCT excitation of the <b>HT</b> phase at 400 nm generates a [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>HS</sub>] species with a lifetime of 3.6 ps. Subsequent back-electron transfer populates the vibrationally hot ground state, which thermalizes within 8 ps. The newly synthesized dinuclear PBA, [CoFe(CN)<sub>3</sub>(tp*)(pz*<sub>4</sub>Lut)]ClO<sub>4</sub> (<b>2</b>), provides a benchmark of the <b>HT</b> phase of <b>1</b>, i.e. [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>], as verified by variable temperature magnetic susceptibility measurements and <sup>57</sup>Fe Mößbauer spectroscopy. The photo-induced charge transfer dynamics of PBA <b>2</b> indeed is almost identical to that of the <b>HT</b> phase of phase of PBA <b>1</b> with a lifetime of the excited [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>HS</sub>] species of 3.8 ps.

Thermally Induced High-Spin Low-Spin Transition in Co[Cr0.5Ga1.5]S4 Spinel

2011 ◽  
Vol 170 ◽  
pp. 9-12
Author(s):  
J. Krok-Kowalski ◽  
Ewa Maciążek ◽  
Tadeusz Groń ◽  
Andrzej W. Pacyna ◽  
Tadeusz Mydlarz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
High Spin ◽  
Inflection Point ◽  
Spin Transition ◽  
Spin Frustration ◽  
Strong Suppression ◽  
Thermally Induced ◽  
Tetrahedral Sites ◽  
Curie Temperature Tc

A high spin (HS) – low spin (LS) transition has been discovered in the Co[Cr0.5Ga1.5]S4 spinel, where the Co ions occupy tetrahedral sites and the Cr and Ga ions octahedral ones. The latter are diluted by the non-magnetic Ga-ions. Application of magnetic fields revealed ferrimagnetic order with a Curie temperature TC = 126 K, a strong suppression of the magnetic susceptibility () and a slight shift of TC to lower temperatures. A cusp at 15.6 K on the ac (T) curve suggests a spin frustration of the re-entrant type. Characteristic for the HS-LS transition is an inflection point at 150 K on the 1/(T) curve, a lack of the Curie-Weiss region above TC and a small value of the magnetization, 4.76 emu/g at 4.4 K and at a magnetic field of 57.5 kOe.

Cobalt(II) Mercury Tetrathiocyanate Complexes with Lewis Bases

1973 ◽  
Vol 51 (3) ◽  
pp. 438-447 ◽  
Author(s):  
R. Makhija ◽  
L. Pazdernik ◽  
R. Rivest
Keyword(s):  
Magnetic Susceptibility ◽  
Powder Diffraction ◽  
Elemental Analysis ◽  
Far Infrared ◽  
Crystalline Solid ◽  
Ultraviolet Spectroscopy ◽  
X Ray ◽  
Lewis Bases ◽  
Polydentate Ligands

A new series of octahedral cobalt(II) complexes are formed when CoX2(X = Cl, Br, I, SCN) reacts with Hg(SCN)2 in the presence of Lewis bases. These complexes of stoichiometry CoHg(SCN)4•2L (L = THF, dioxane, pyridine, aniline) are pink to violet solids which slowly decompose to the blue crystalline solid, CoHg(SCN)4, the stable magnetic susceptibility standard. On further reaction of CoHg(SCN)4•2THF with mono-, bi-, and polydentate ligands in dry ethanol, complexes of the following types are obtained: CoHg(SCN)4•2L (L = PΦ3), CoHg(SCN)4•2LL (LL = trien), CoHg(SCN)4•3LL (LL = en, bipy), and CoHg(SCN)4•4LL (LL = phen). The stoichiometry of these were determined by elemental analysis. Possible structures of these are discussed with the help of mid and far infrared, visible, and ultraviolet spectroscopy, magnetic susceptibility, and X-ray powder diffraction. Some new i.r. bands like Co—P, Co—N, and Hg—S are assigned in the low region.

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.

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