Structural, Magnetic and Mössbauer Studies of Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Triflate and its Hydrates

1997 ◽  
Vol 50 (9) ◽  
pp. 869 ◽  
Author(s):  
Kristian H. Sugiyarto ◽  
Karyn Weitzner ◽  
Donald C. Craig ◽  
Harold A. Goodwin
Keyword(s):  
Electronic Properties ◽  
Low Temperatures ◽  
Room Temperature ◽  
Spin Transition ◽  
Water Molecules ◽  
Triclinic Space Group ◽  
Discontinuous Transition ◽  
A Minor ◽  
Spin Species ◽  
Anhydrous Complex

The electronic properties of bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) triflate depend markedly on the extent of hydration. The trihydrate is low spin while the monohydrate is high spin at room temperature but undergoes a discontinuous transition to low spin at low temperatures. In the anhydrous complex magnetic and Mössbauer spectral data indicate that there is a minor fraction of low-spin species at room temperature and this fraction increases at low temperatures. The spin transition in the anhydrous salt is continuous and incomplete at 80 K. The structure of the trihydrate reveals an extensive hydrogen-bonding network which involves the uncoordinated >NH groups of the pyrazolyl groups in the ligands, the water molecules and the anions. The disruption of this network on loss of water is believed to be responsible for the change in electronic properties. Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) triflate trihydrate: triclinic, space group P-1, a 11·490(5), b 12·218(6), c 13·666(6) Å, α 104 ·67(2), β 104·58(2), γ 104·35(2)°, Z 2.

Structural and Electronic Properties of the Iron(II) and Nickel(II) Bis(ligand) Complexes of 6-(5-Methyl-1,2,4-oxadiazol-3-yl)-2,2′-bipyridine— a Terpyridine-Based Tridentate

1999 ◽  
Vol 52 (7) ◽  
pp. 673 ◽  
Author(s):  
Bradley J. Childs ◽  
Marcia L. Scudder ◽  
Donald C. Craig ◽  
Harold A. Goodwin
Keyword(s):  
Electronic Properties ◽  
Spectroscopic Data ◽  
Room Temperature ◽  
Spin Transition ◽  
Iron Complex ◽  
Ligand Field ◽  
Monoclinic Space Group ◽  
Space Group ◽  
C 23 ◽  
Structural And Electronic Properties

Iron(II) and nickel(II) bis(ligand) complexes of 6-(5-methyl-1,2,4-oxadiazol-3-yl)-2,2′-bipyridine (L) are described. The ligand field in the iron complex is close to that at the singlet ( 1 A1) ? quintet ( 5 T2) crossover and magnetic and Mössbauer spectral evidence indicates that a spin transition occurs in salts of the iron complex but is centred above room temperature. The structures of [FeL2] [CF3SO3]2.CH3CN and [NiL2] [BF4]2.CH3CN were determined and both are very similar to the structures of the corresponding terpyridine complexes. Spectroscopic data indicate that for the iron complex π-interaction between the metal and the ligand is less than that in the terpyridine system. [FeL2] [CF3SO3]2.CH3CN is monoclinic, space group P 21/c; a 8 . 232(5), b 25 . 273(10), c 17 . 306(10) Å, β 92 . 37(3)°, Z 4; [NiL2] [BF4]2.CH3CN is monoclinic, space group P 21/c; a 8 . 136(2), b 17 . 558(2), c 23 . 783(7) Å, β 109 . 32(1)°, Z 4.

Infrared Spectra of Water in Crystalline Hydrates: KSnCl3•H2O, an Untypical Monohydrate

1974 ◽  
Vol 52 (16) ◽  
pp. 2928-2931 ◽  
Author(s):  
Michael Falk ◽  
Chung-Hsi Huang ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Room Temperature ◽  
Water Molecules ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline KSnCl3•H2O were recorded between 4000 and 300 cm−1 at different degrees of deuteration and at temperatures between 30 and −160 °C. At low temperatures the spectra show a complexity indicative of the presence of several crystallographically distinct water molecules. These molecules occupy sites with nearly identical environments and at room temperature are spectroscopically indistinguishable. The environment of each of these molecules is asymmetric. Hydrogen bonds are very weak and probably highly bent. The water molecules are less separated from one another than in K2SnCl4•H2O and may share their potassium neighbors.

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.

Investigation of the V4+-Centre in 6H- and 4H-SIC by the Method of Spectral-Hole Burning

1998 ◽  
Vol 512 ◽  
Author(s):  
C. Hecht ◽  
R. Kummer ◽  
A. Winnacker
Keyword(s):  
Electronic Properties ◽  
Room Temperature ◽  
Hole Burning ◽  
Band Offset ◽  
Spectral Hole Burning ◽  
Type Ii ◽  
Thermally Stable ◽  
Spectral Hole

ABSTRACTIn the context of spectral-hole burning experiments in 4H- and 6H-SiC doped with vanadium the energy positions of the V4+/5+ level in both polytypes were determined in order to resolve discrepancies in literature. From these numbers the band offset of 6H/4H-SiC is calculated by using the Langer-Heinrich rule, and found to be of staggered type II. Furthermore the experiments show that thermally stable electronic traps exist in both polytypes at room temperature and considerably above, which may result in longtime transient shifts of electronic properties.

Room-temperature synthesis, growth mechanisms and opto-electronic properties of organic–inorganic halide perovskite CH3NH3PbX3 (X = I, Br, and Cl) single crystals

CrystEngComm ◽  
2021 ◽  
Author(s):  
Maryam Bari ◽  
Hua Wu ◽  
Alexei A. Bokov ◽  
Rana Faryad Ali ◽  
Hamel N. Tailor ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Single Crystals ◽  
Room Temperature ◽  
Solubility Curve ◽  
Inverse Temperature ◽  
Growth Mechanisms ◽  
Temperature Synthesis ◽  
Room Temperature Synthesis ◽  
Halide Perovskite ◽  
Temperature Crystallization

Growth of MAPbX3 (X = I, Br, and Cl) single crystals by room temperature crystallization (RTC) method, and the crystallization pathway illustrated by the solubility curve of MAPbCl3 in DMSO, compared with inverse temperature crystallization (ITC) method.

scholarly journals Review of Multi-Physics Modeling on the Active Magnetic Regenerative Refrigeration

2021 ◽  
Vol 26 (2) ◽  
pp. 47
Author(s):  
Julien Eustache ◽  
Antony Plait ◽  
Frédéric Dubas ◽  
Raynal Glises
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Room Temperature ◽  
State Of The Art ◽  
Vapor Compression ◽  
Crucial Step ◽  
Potential Alternative ◽  
Vapor Compression Refrigeration ◽  
Preliminary Study ◽  
Physics Modeling

Compared to conventional vapor-compression refrigeration systems, magnetic refrigeration is a promising and potential alternative technology. The magnetocaloric effect (MCE) is used to produce heat and cold sources through a magnetocaloric material (MCM). The material is submitted to a magnetic field with active magnetic regenerative refrigeration (AMRR) cycles. Initially, this effect was widely used for cryogenic applications to achieve very low temperatures. However, this technology must be improved to replace vapor-compression devices operating around room temperature. Therefore, over the last 30 years, a lot of studies have been done to obtain more efficient devices. Thus, the modeling is a crucial step to perform a preliminary study and optimization. In this paper, after a large introduction on MCE research, a state-of-the-art of multi-physics modeling on the AMRR cycle modeling is made. To end this paper, a suggestion of innovative and advanced modeling solutions to study magnetocaloric regenerator is described.

scholarly journals On the measurement of the ratio of the specific heats using small volumes of gas.—The ratios of the specific heat of air and of hydrogen at atmospheric pressure and a temperatures between 20°C. and —183°C

1925 ◽  
Vol 107 (743) ◽  
pp. 510-543 ◽  
Keyword(s):  
Systematic Error ◽  
Low Temperatures ◽  
Room Temperature ◽  
Expansion Chamber ◽  
Small Vessels ◽  
Specific Heats ◽  
Large Expansion ◽  
Before And After ◽  
The One ◽  
Chamber Capacity

Introduction .—In nearly all the previous determinations of the ratio of the specific heats of gases, from measurements of the pressures and temperature before and after an adiabatic expansion, large expansion chambers of fror 50 to 130 litres capacity have been used. Professor Callendar first suggests the use of smaller vessels, and in 1914, Mercer (‘Proc. Phys. Soc.,’ vol. 26 p. 155) made some measurements with several gases, but at room temperature only, using volumes of about 300 and 2000 c. c. respectively. He obtained values which indicated that small vessels could be used, and that, with proper corrections, a considerable degree of accuracy might be obtained. The one other experimenter who has used a small expansion chamber, capacity about 1 litre, is M. C. Shields (‘Phys. Rev.,’ 1917), who measured this ratio for air and for hydrogen at room temperature, about 18° C., and its value for hydroger at — 190° C. The chief advantage gained by the use of large expansion chambers is that no correction, or at the most, a very small one, has to be made for any systematic error due to the size of the containing vessels, but it is clear that, in the determinations of the ratio of the specific heats of gases at low temperatures, the use of small vessels becomes a practical necessity in order that uniform and steady temperature conditions may be obtained. Owing, however, to the presence of a systematic error depending upon the dimensions of the expansion chamber, the magnitude of which had not been definitely settled by experiment, the following work was undertaken with the object of investigating the method more fully, especially with regard to it? applicability to the determination of this ratio at low temperatures.

The Effect of Electron Irradiation on the Structure of Sodium Aluminum-Iron Phosphate Glasses

MRS Advances ◽  
2016 ◽  
Vol 1 (63-64) ◽  
pp. 4227-4232 ◽  
Author(s):  
S.V. Stefanovsky ◽  
O.I. Stefanovsky ◽  
M.I Kadyko ◽  
V.A. Zhachkin ◽  
L.D. Bogomolova
Keyword(s):  
Room Temperature ◽  
Structural Evolution ◽  
Iron Phosphate ◽  
Esr Spectra ◽  
Phosphate Glasses ◽  
Water Molecules ◽  
Oxygen Hole ◽  
Bending Modes ◽  
Iron Phosphate Glasses ◽  
Hole Centers

ABSTRACTGlasses of the series (mol.%) 40 Na2O, (20-x) Al2O3, x Fe2O3, 40 P2O5 were irradiated with 8 MeV electrons to doses equivalent of 0.1, 0.5, and 1.0 MGy and characterized by FTIR spectroscopy and ESR at room temperature. FTIR spectra of all the glasses consist of strong bands due to O-P-O stretching modes in (PO4)3- and (P2O7)4- units at 1000-1200 cm-1, P-O-P stretching modes at 900-950 cm-1 (νas) and 700-750 cm-1 (νs), and bending modes in the PO4 units. The wavenumber range lower 800 cm-1 has some contribution due to stretching modes in MO4 and MO6 (M = Al, Fe) units. Moreover the bands at 3300-3700 cm-1 and 1550-1650 cm-1 due to stretching and bending modes in both absorbed and structurally bound H2O molecules were present. As irradiation dose increases the bands due to stretching and bending modes in water molecules and M-O-H bonds become stronger and are split. No essential changes with increasing dose were observed within the spectral range of stretching modes of the O-P-O and P-O-P bonds. Irradiation yields phosphorus-oxygen hole centers - PO42- (D5) and PO42- (D6), and PO32- ion-radicals (D2) observable in ESR spectra of low-Fe glasses. At x>5 their responses are overlapped with strong broad line due to Fe(III). On the whole, with the increase in iron content the glass structural evolution decrease.

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