scholarly journals Structural Insights into the Two-Step Spin-Crossover Compound Fe(3,4-dimethyl-pyridine)2[Ag(CN)2]2

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 316 ◽  
Author(s):  
José Alberto Rodríguez-Velamazán ◽  
Kosuke Kitase ◽  
Elías Palacios ◽  
Miguel Castro ◽  
Ángel Fernández-Blanco ◽  
...  
Keyword(s):  
High Spin ◽  
Spin Crossover ◽  
Spin Transition ◽  
Long Range Order ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Step Transition ◽  
Structural Insights ◽  
Spin Species

The crystal structure of the polymeric spin crossover compound Fe(3,4-dimethyl-pyridine)2[Ag(CN)2]2 has been solved and its temperature dependence followed by means of single-crystal and powder X-ray diffraction. This compound presents a two-step spin transition with relatively abrupt steps centred at ca. 170 K and 145 K and a plateau at around 155 K. The origin of the two-step transition is discussed in light of these structural studies. The observations are compatible with a mostly disordered state between the two steps, consisting of mixing of high-spin and low-spin species, while weak substructure reflections in the mixed phase could indicate some degree of long-range order of the high-spin and low-spin sites.

Structural Investigation of the Photoinduced Spin Transition in the [Fe(PM-BiA)2(NCS)2] Compound

2006 ◽  
Vol 112 ◽  
pp. 81-88 ◽  
Author(s):  
Kouhei Ichiyanagi ◽  
Johan Hebert ◽  
Loic Toupet ◽  
Hérve Cailleau ◽  
Eric Collet ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
High Spin ◽  
Thermal Equilibrium ◽  
Molecular Crystal ◽  
Structural Investigation ◽  
Spin Transition ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
X Ray

We investigated the thermo- and photo-induced phase transitions between low spin (LS) and high spin (HS) states of the molecular crystal of [Fe(PM-BiA)2(NCS)2] in the orthorhombic form, by using X-ray diffraction. The structure of the photoinduced HS state, generated from the LS state at low temperature, is compared to the structures of the HS and LS phases at thermal equilibrium and to the thermally trapped HS state. The preliminary results presented here show that the structural reorganization is similar in the different HS states.

Coordination of 2,2'-Bithiazole. Spectral, Magnetic and Structural Studies of the Iron(II) and Nickel(II) Complexes

1988 ◽  
Vol 41 (11) ◽  
pp. 1625 ◽  
Author(s):  
DC Craig ◽  
HA Goodwin ◽  
D Onggo ◽  
AD Rae
Keyword(s):  
High Spin ◽  
Spectral Properties ◽  
Elevated Temperatures ◽  
Spin Transition ◽  
Anomalous Temperature ◽  
Space Group ◽  
X Ray ◽  
Spin Lattice ◽  
Centrosymmetric Space Group ◽  
Spin Species

Iron(II) and nickel(II) complexes of 2,2′bithiazole (2bt) have been prepared. Salts of [Fe(2bt)3]2+ have spectral properties typical of iron(II) diimine systems. Their magnetic and Mossbauer spectral properties show an anomalous temperature-dependence which is associated with a temperature-induced singlet (1A1) ↔ quintet (5T2) transition. The manifestation of the spin transition is complicated by the existence of two modifications of the complex perchlorate. In one of these there is a relatively small fraction of quintet state species in an essentially low-spin lattice. This fraction increases only slightly at elevated temperatures within the range 89-343 K. The other modification is essentially high-spin at high temperatures and low-spin at low temperatures. The quadrupole splitting values for the two high-spin species are quite different, arising from different lattice contributions. The structures of 2bt and the related 4,4′-bithiazole and of [Ni(2bt)3][ClO4]2 have been determined by single-crystal X-ray diffactometry. These afford a comparison of the coordination features of the isomeric bithiazoles. 2,2′-Bithiazole, orthorhombic with space group P bca , Z = 8, α 9.284(1), b 14.564(1), c 10.802(1) Ǻ; 4,4′-Bithiazole, monoclinic with space group P21/c, Z = 2, a 5.528(2), b 6.288(2), c 11.316(4)Ǻ. The nickel complex, orthorhombic with non-centrosymmetric space group Pna21, four molecules per unit cell, a 16.709(3), b 9.511(4), c 17.491(2)Ǻ, has a stacking fault which reduces the intensity of h = 2n+1 data. Pseudosymmetry enables data with h = 2n to be described by a disordered structure in the centrosymmetric space group Pnmn.

An X-ray powder diffraction study of the spin-crossover transition and structure of bis(2,6-dipyrazol-1-ylpyrazine)iron(II) perchlorate

2004 ◽  
Vol 60 (1) ◽  
pp. 41-45 ◽  
Author(s):  
Victoria A. Money ◽  
Ivana Radosavljevic Evans ◽  
Jerome Elhaïk ◽  
Malcolm A. Halcrow ◽  
Judith A. K. Howard
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Spin Crossover ◽  
Spin Transition ◽  
High Spin State ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Crossover Transition

The crystal structure of the iron(II) spin-crossover compound [Fe(C10H8N6)2](ClO4)2 in the high-spin state has been solved from powder X-ray diffraction data using the DASH program and refined using Rietveld refinement. The thermal spin transition has been monitored by following the change in unit-cell parameters with temperature. The title compound has been found to undergo a crystallographic phase change, involving a doubling of the crystallographic a axis, on undergoing the spin transition.

Polymorphism in the spin-crossover ferric complexes [(TPA)FeIII(TCC)]PF6

2009 ◽  
Vol 65 (4) ◽  
pp. 474-480 ◽  
Author(s):  
Eric Collet ◽  
Marie-Laure Boillot ◽  
Johan Hebert ◽  
Nicolas Moisan ◽  
Marina Servol ◽  
...  
Keyword(s):  
Optical Properties ◽  
High Spin ◽  
Molecular Complex ◽  
Spin Crossover ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystalline Structures

We have identified two polymorphs of the molecular complex [(TPA)Fe(III)(TCC)]PF6 [TPA = tris(2-pyridylmethyl)amine and TCC = 3,4,5,6-tetrachlorocatecholate dianion]: one is monoclinic and the other is orthorhombic. By lowering the temperature both undergo a thermal spin-crossover between a high-spin (S = 5/2) and a low-spin (S = 1/2) state, which we detected by magnetic, optical and X-ray diffraction measurements. The thermal crossover is only slightly shifted between the polymorphs. Their crystalline structures consist of similar cation layers alternating with PF6 anion layers, packed differently in the two polymorphs. The magnetic and optical properties of the polymorphs are presented.

An iron(II) complex tripodally chelated with 1,1,1-tris(pyridin-2-yl)ethane showing room-temperature spin-crossover behaviour

2016 ◽  
Vol 72 (11) ◽  
pp. 797-801 ◽  
Author(s):  
Takayuki Ishida ◽  
Takuya Kanetomo ◽  
Masaru Yamasaki
Keyword(s):  
High Spin ◽  
Room Temperature ◽  
Spin Crossover ◽  
Spin Transition ◽  
Complex Salt ◽  
Magnetic Study ◽  
The Novel ◽  
Bond Lengths ◽  
External Stimuli ◽  
Spin Species

The spin-crossover phenomenon is a reversible low- and high-spin transition caused by external stimuli such as heat. In the novel iron(II) complex salt tetraphenylphosphonium tris(thiocyanato-κN)[1,1,1-tris(pyridin-2-yl)ethane-κ3N,N′,N′′]ferrate(II), (C24H20P)[Fe(NCS)3(C17H15N3)], the Fe—N bond lengths are in the range 2.027 (2)–2.089 (2) Å, indicating that the specimen consists of comparable molar fractions of the low- and high-spin species at 296 K. A magnetic study confirmed that spin-crossover takes place at around 290 K.

scholarly journals Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 276 ◽  
Author(s):  
Tomoe Matsuyama ◽  
Keishi Nakata ◽  
Hiroaki Hagiwara ◽  
Taro Udagawa
Keyword(s):  
Schiff Base ◽  
Schiff Base Ligand ◽  
Spin Crossover ◽  
Variable Temperature ◽  
Spin Transition ◽  
Ligand Field ◽  
X Ray Diffraction ◽  
Monodentate Ligand ◽  
X Ray ◽  
Mononuclear Iron

A mononuclear iron(II) complex bearing the linear pentadentate N5 Schiff-base ligand containing two 1,2,3-triazole moieties and the MeCN monodentate ligand, [FeIIMeCN(L3-Me-3Ph)](BPh4)2·MeCN·H2O (1), have been prepared (L3-Me-3Ph = bis(N,N′-1-Phenyl-1H-1,2,3-triazol-4-yl-methylideneaminopropyl)methylamine). Variable-temperature magnetic susceptibility measurements revealed an incomplete one-step spin crossover (SCO) from the room-temperature low-spin (LS, S = 0) state to a mixture of the LS and high-spin (HS, S = 2) species at the higher temperature of around 400 K upon first heating, which is irreversible on the consecutive cooling mode. The magnetic modulation at around 400 K was induced by the crystal-to-amorphous transformation accompanied by the loss of lattice MeCN solvent, which was evident from powder X-ray diffraction (PXRD) studies and themogravimetry. The single-crystal X-ray diffraction studies showed that the complex is in the LS state (S = 0) between 296 and 387 K. In the crystal lattice, the complex-cations and B(1)Ph4− ions are alternately connected by intermolecular CH···π interactions between the methyl group of the MeCN ligand and phenyl groups of B(1)Ph4− ions, forming a 1D chain structure. The 1D chains are further connected by P4AE (parallel fourfold aryl embrace) interactions between two neighboring complex-cations, constructing a 2D extended structure. B(2)Ph4− ions and MeCN lattice solvents exist in the spaces of the 2D layer. DFT calculations verified that the 1,2,3-triazole-containing ligand L3-Me-3Ph gives a stronger ligand field around the octahedral coordination environment of the iron(II) ion than the analogous imidazole-containing ligand H2L2Me (= bis(N,N′-2-methylimidazol-4-yl-methylideneaminopropyl)methylamine) of the known compound [FeIIMeCN(H2L2Me)](BPh4)1.5·Cl0.5·0.5MeCN (2) reported by Matsumoto et al. (Nishi, K.; Fujinami, T.; Kitabayashi, A.; Matsumoto, N. Tetrameric spin crossover iron(II) complex constructed by imidazole⋯chloride hydrogen bonds. Inorg. Chem. Commun. 2011, 14, 1073–1076), resulting in the much higher spin transition temperature of 1 than that of 2.

scholarly journals Structural Studies into the Spin Crossover Behaviour of Fe(abpt)2(NCS)2 Polymorphs B and D

2021 ◽  
Author(s):  
Helen Elizabeth Mason ◽  
Jake R.C. Musselle-Sexton ◽  
Judith A. K. Howard ◽  
Michael Probert ◽  
Hazel Anne Sparkes
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Spin Crossover ◽  
Structural Features ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
X Ray

The spin-crossover behaviour of [Fe(abpt)2(NCS)2] (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) polymorphs B and D have been studied using single crystal X-ray diffraction to monitor changes in structural features. High pressure single crystal...

Ribosome Structural Organization

1974 ◽  
Vol 32 ◽  
pp. 332-333
Author(s):  
James A. Lake
Keyword(s):  
Ribosomal Proteins ◽  
Structural Organization ◽  
Three Dimensional ◽  
Small Subunit ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
Specific Antibodies ◽  
X Ray ◽  
E Coli ◽  
Complete Sequences

The understanding of ribosome structure has advanced considerably in the last several years. Biochemists have characterized the constituent proteins and rRNA's of ribosomes. Complete sequences have been determined for some ribosomal proteins and specific antibodies have been prepared against all E. coli small subunit proteins. In addition, a number of naturally occuring systems of three dimensional ribosome crystals which are suitable for structural studies have been observed in eukaryotes. Although the crystals are, in general, too small for X-ray diffraction, their size is ideal for electron microscopy.

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