The high-spin(5T2)⇌low-spin(1A1) transition in solid dithiocyanatobis(2,2′-bi-2,thiazoline)iron(II). Hysteresis effects, debye-waller factors and crystallographic changes

König, E.; Ritter, G.; Irler, W.; Nelson, S. M.

doi:10.1016/s0020-1693(00)95540-3

Cited by 43 publications

(13 citation statements)

References 25 publications

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“…‡ Roosevelt University. of ∼3.00 mm/s at 77.5 K, similar to the limiting value found 16 for the HS form of polymorph A. This is consistent with an isolated, orbitally nondegenerate ground state and the expectation of essentially spin-only magnetic behavior at low temperature.…”

supporting

confidence: 86%

High-Frequency and -Field EPR of a Pseudo-octahedral Complex of High-Spin Fe(II): Bis(2,2‘-bi-2-thiazoline)bis(isothiocyanato)iron(II)

et al. 2004

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Iron is ubiquitous in metalloproteins, in a wide range of coordination environments. A large and important class of Fe proteins consists of the non-heme Fe proteins, in which Fe is often six-coordinate and generally has two or more endogenous histidine ligands. 1,2 HS 3 Fe(II) (3d 6 , S ) 2) is an important state in nonheme Fe proteins; however, this state is relatively difficult to investigate by EPR, normally a technique of choice for paramagnetic transition metal systems. HS Fe(II) is a non-Kramers (integer spin) ion of typically large zfs, on the order of 5-20 cm -1 . 4,5 The allowed EPR transitions thus generally appear at high frequencies, and/or at high magnetic fields. 6 Among spectroscopic methods generally applied to HS Fe(II) systems, Mössbauer spectroscopy 7,8 and MCD 1,9 are most informative, as are magnetic susceptibility measurements. 10 Far-infrared (FIR) spectroscopy 11 and, more recently, INS 12 have also been employed to detect transitions among the HS Fe(II) quintet-state zero-field levels and consequently provide information on its electronic structure. Another approach is to employ EPR, but at frequencies and fields sufficiently high to observe the allowed transitions. 13 12 The HFEPR results in the latter report were, however, secondary to highly informative INS results. Very few HFEPR transitions were observed, and the S/N ratio of reported EPR spectra was relatively low. 12 We demonstrate here that it is indeed possible to observe multiple HFEPR transitions for HS Fe(II) with high S/N ratio, in this case for a cis-FeN′ 2 N 4 chromophore complex: bis(2,2′-bi-2-thiazoline)-bis(isothiocyanato)iron(II) (1). Complex 1 can be considered as an approximate model for six-coordinate active sites in non-heme Fe proteins, wherein their histidine ligands are represented in 1 by the imino N-donor thiazoline ligands. We show that it is possible by HFEPR to accurately determine spin Hamiltonian parameters in this complex, and relate them to the electronic structure.Complex 1 exists as two polymorphs, A 15-18 and B. 18 It was polymorph A that drew initial attention since it undergoes a temperature-driven spin-crossover transition to a diamagnetic (LS, S ) 0) state. [15][16][17][18] Polymorph B remains paramagnetic (HS, S ) 2) to 4.2 K but is "silent" at conventional EPR frequencies. Crystals of each polymorph can be independently prepared, and their structures have been determined. 18 The structure of polymorph B (1B) is shown in Chart 1. Crystals of 1B were ground to a fine powder for HFEPR experiments. The HFEPR apparatus and the tunable-frequency EPR methodology as employed here have been previously described. 19 We have also performed Mössbauer spectroscopy measurements at 77 and 293 K, and DC SQUID magnetometry between 1.8 and 293 K for 1B. Figure 1 shows typical HFEPR spectra of 1B using two different modulation techniques: chopping the sub-THz wave beam, which results in an absorptive shape (black trace), and standard modulation of magnetic field (blue trace). The red trace is a derivative simulat...

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confidence: 86%

High-Frequency and -Field EPR of a Pseudo-octahedral Complex of High-Spin Fe(II): Bis(2,2‘-bi-2-thiazoline)bis(isothiocyanato)iron(II)

et al. 2004

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“…Furthermore, the equilibrium temperature for 1 , T 1/2 = 170 K, is 55 K higher than the average T 1/2 value shown by its X = S homologue. , This suggests that the increase in ligand field strength around the Fe II induced by the XCN – (X = S, Se) group does not depend substantially on whether it belongs to the dimeric bridging unit {[Hg II (XCN) 3 ] 2 (μ-L)} 2– or acts as a simple coordinating terminal anion. It is worth noting that differences of similar magnitude in T 1/2 have been found for monomeric − and polymeric 1D − and 2D − [Fe(L) 2 (NCX) 2 ] SCO complexes. Interestingly, from the point of view of the coordination sphere of the Fe II ion, the latter series of compounds represent the antithesis of the compounds described here.…”

Section: Discussion and Concluding Remarkssupporting

confidence: 64%

Spin Crossover in a Series of Non-Hofmann-Type Fe(II) Coordination Polymers Based on [Hg(SeCN)₃]⁻ or [Hg(SeCN)₄]^2– Building Blocks

et al. 2021

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Self-assembly of [Hg(SeCN) 4 ] 2− tetrahedral building blocks, iron(II) ions, and a series of bis-monodentate pyridyltype bridging ligands has afforded the new heterobimetallic Hg II -Fe II coordination polymers {Fe [Hg(SeCN) ethylene, 4,4′-azpy = 4,4′-azobispyridine, 3,3-bipy = 3,3′bipyridine, 3,3′-azpy = 3,3′-azobispyridine). Single-crystal X-ray analyses show that compounds 1 and 3 display a two-dimensional robust sheet structure made up of infinite linear [(FeL) n ] 2n+ (L = 4,4′-bipy or 4,4′-azpy) chains linked by in situ formed {[Hg(L)(SeCN) 3 ] 2 } 2− anionic dimeric bridges. Complexes 2 and 4−6 define three-dimensional networks with different topological structures, indicating, in combination with complexes 1 and 3, that the polarity, length, rigidity, and conformation of the bridging organic ligand play important roles in the structural nature of the products reported here. The magnetic properties of complexes 1 and 2 show the occurrence of temperature-and light-induced spin crossover (SCO) properties, while complexes 4−6 are in the high-spin state at all temperatures. The current results provide a new route for the design and synthesis of new SCO functional materials with non-Hofmann-type traditional structures.

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“…The bonding in gold clusters is determined largely by the 6s and 6p valence orbitals. The average calculated electronic configuration changes from 5 .04 0.03^9.93 at Au2 to sa90p01'd9 " at Au13 to s°'90p0 29d9 81 at Au43, which indicates the increasing component of p bonding (10) in larger clusters. The s and p orbitals are much more diffuse than the d orbitals, and they form a broad band which completely overlaps the d band at a cluster size of 13 atoms.…”

Section: Resultsmentioning

confidence: 94%

Electronic properties of metal clusters: size effects

Baetzold¹

1981

Inorg. Chem.

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The high-spin(5T2)⇌low-spin(1A1) transition in solid dithiocyanatobis(2,2′-bi-2,thiazoline)iron(II). Hysteresis effects, debye-waller factors and crystallographic changes

Cited by 43 publications

References 25 publications

High-Frequency and -Field EPR of a Pseudo-octahedral Complex of High-Spin Fe(II): Bis(2,2‘-bi-2-thiazoline)bis(isothiocyanato)iron(II)

High-Frequency and -Field EPR of a Pseudo-octahedral Complex of High-Spin Fe(II): Bis(2,2‘-bi-2-thiazoline)bis(isothiocyanato)iron(II)

Spin Crossover in a Series of Non-Hofmann-Type Fe(II) Coordination Polymers Based on [Hg(SeCN)₃]⁻ or [Hg(SeCN)₄]^2– Building Blocks

Electronic properties of metal clusters: size effects

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The high-spin(5T2)⇌low-spin(1A1) transition in solid dithiocyanatobis(2,2′-bi-2,thiazoline)iron(II). Hysteresis effects, debye-waller factors and crystallographic changes

Cited by 43 publications

References 25 publications

High-Frequency and -Field EPR of a Pseudo-octahedral Complex of High-Spin Fe(II): Bis(2,2‘-bi-2-thiazoline)bis(isothiocyanato)iron(II)

High-Frequency and -Field EPR of a Pseudo-octahedral Complex of High-Spin Fe(II): Bis(2,2‘-bi-2-thiazoline)bis(isothiocyanato)iron(II)

Spin Crossover in a Series of Non-Hofmann-Type Fe(II) Coordination Polymers Based on [Hg(SeCN)3]− or [Hg(SeCN)4]2– Building Blocks

Electronic properties of metal clusters: size effects

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Spin Crossover in a Series of Non-Hofmann-Type Fe(II) Coordination Polymers Based on [Hg(SeCN)₃]⁻ or [Hg(SeCN)₄]^2– Building Blocks