The high-spin(5T2) .dblharw. low-spin(1A1) transition in solid bis[2-(2-pyridylamino)-4-(2-pyridyl)thiazoleiron(II) dinitrate. Its dependence on time and on the previous history of the specimen

Ritter, G.; Koenig, E.; Irler, W.; Goodwin, Harold A.

doi:10.1021/ic50180a005

Cited by 73 publications

(40 citation statements)

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“…Complexes 5 and 6 show a similar behavior, in that both compounds only exhibit wide spin-crossover hysteresis upon slow temperature scanning (¦T = 91 K for 5, 20,40 and 34 K for 6 41 ). Although no structural data are available, a calorimetry study of 5 showed that it undergoes a very slow phase change near 200 K, which cannot occur if the temperature is scanned too quickly.…”

Section: Molecular Compounds Showing Wide and Symmetric Thermal Hystementioning

confidence: 93%

Spin-crossover Compounds with Wide Thermal Hysteresis

2014

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Spin-crossover compounds showing wide thermal hysteresis are surveyed, and the factors underlying these properties are discussed. Hysteresis is promoted by large structural rearrangements during the transition and by strong intermolecular interactions involving rigid ligand groups or donor atoms. These observations provide new principles for the design of molecular crystals undergoing spin crossover (or other phase changes) with predefined switching properties.

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Section: Molecular Compounds Showing Wide and Symmetric Thermal Hystementioning

confidence: 93%

Spin-crossover Compounds with Wide Thermal Hysteresis

2014

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“…From coordination compounds it is known that a certain quantity of the high-spin population can get trapped on rapid cooling, because the lattice does not have enough time to relax, a phenomenon known as "spin trapping". [32][33][34][35][36][37][38][39] Up to 6% of the high-spin population in [1,3- Figure S13. The data range is limited by a monochromator glitch at about 12.5 Å -1 that affects data at some temperatures more than others; the samples were very difficult to align because they were strongly tapered.…”

Section: Methodsmentioning

confidence: 99%

Supramolecular Catalysis of Orthoformate Hydrolysis in Basic Solution: An Enzyme-Like Mechanism

2008

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Abstract. Magnetic susceptibility measurements and X-ray data confirm that tert-butyl substituted manganocenes [(Me 3 C) n C 5 H 5-n ] 2 Mn (n= 1, 2) follow the trend previously observed with the methylated manganocenes, i.e., electron donating groups attached to the Cp ring stabilize the low-spin (LS) electronic ground state relative to Cp 2 Mn and exhibit higher spin-crossover (SCO) temperatures.However, introducing three CMe 3 groups on each ring gives a temperature invariant high-spin (HS) state manganocene. The origin of the high-spin state in [1,2,4-(Me 3 C) 3 C 5 H 2 ] 2 Mn is due to the significant bulk of the [1,2,4-(Me 3 C) 3 C 5 H 2 ] -ligand, which is sufficient to generate severe inter-ring steric strain that prevents the realization of the low-spin state. Interestingly, the spin transition in [1,3-(Me 3 C) 2 C 5 H 3 ] 2 Mn is accompanied by a phase transition resulting in a significant irreversible hysteresis (∆T c = 16 K). This structural transition was also observed by extended X-ray absorption fine-structure (EXAFS) measurements. Magnetic susceptibility studies and X-ray diffraction data on SiMe 3 substituted 2 manganocenes [(Me 3 Si) n C 5 H 5-n ] 2 Mn (n= 1, 2, 3) show high-spin configuration in these cases. Although tetra-and hexasubstituted manganocenes are high-spin at all accessible temperatures, the disubstituted manganocenes exhibit a small low-spin admixture at low temperature. In this respect it behaves similarily to [(Me 3 C)(Me 3 Si)C 5 H 3 ] 2 Mn, which has a constant low-spin admixture up to 90 K and then gradually converts to high-spin. Thermal spin-trapping can be observed for [(Me 3 C)(Me 3 Si)C 5 H 3 ] 2 Mn on rapid cooling.

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“…The presence of HS metastable state at low temperatures indicates that the lattice structure in HS state at room temperature is probably frozen by the rapid cooling, and that the rate of spin state conversion is relatively slower than that of the structure change. 5 Low temperature HS metastable state induced by the rapid ZFC is reproducible. Scans in sequences ͑b͒ and ͑c͒ confirm the two spin trappings seen in ͑a͒.…”

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confidence: 96%

“…Although it is in principle, possible to induce such a HS metastable state at low temperatures by rapid cooling, the phenomenon has only been successfully demonstrated in a few systems. 5 Recently, a new kind of iron ͑II͒ spin crossover complex ͓Fe͑dpp͒ 2 ͑NCS͒ 2 ]•py has been fabricated. 6 The structure has been determined by x-ray diffraction to be cisdithiocyanatobiscis-dithiocyanatobis ͑dipyrido͓3,2a:2Ј,3Ј-c͔ phenazine͒, where the more extended aromatic ring is expected to show strong intermolecular -interactions to enhance the cooperativity.…”

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confidence: 99%