Guidelines to design new spin crossover materials

Atmani, Chahlae; Hajj, Fatima El; Benmansour, Samia; Marchivie, Mathieu; Triki, Smaı̈l; Conan, Françoise; Patinec, Véronique; Handel, Henri; Dupouy, G.; Gómez‐García, Carlos J.

doi:10.1016/j.ccr.2009.11.004

Cited by 63 publications

(51 citation statements)

References 85 publications

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“…There must hence be subtle crystal packing effects that counterbalance this trend and lower the crystal-field parameter of the molecule once included in the crystal lattice. Similar exceptions have been described in the literature, for example, by Gómez-García et al, [32,33] who explained the absence of SCO for [FeA C H T U N G T R E N N U N G (abpt) 2 A C H T U N G T R E N N U N G (tcnome) 2 ] (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole; tcnome À = 1,1,3,3-tetracyano-2-methoxypropenide anion) by a change in the p-p stacking mode compared to similar [FeA C H T U N G T R E N N U N G (abpt) 2 (X) 2 ] compounds with different apical X anions. In our case, a close analysis of the crystal structures of the HS phases of 11 and 12 shows that the p-p stacking modes are similar in compounds 11, 12, and 15, but that there are noticeable differences in the orientations of the two SCN À anions for both phases (see Figure 8a), which might play a role in terms of the crystal-field strength of both compounds and hence their ability to undergo SCO.…”

Section: Discussionsupporting

confidence: 84%

Tuning the Transition Temperature and Cooperativity of bapbpy‐Based Mononuclear Spin‐Crossover Compounds: Interplay between Molecular and Crystal Engineering

Arcís-Castillo

Zheng

Siegler

et al. 2011

Chemistry A European J

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In this study, we show that 1) different isomers of the same mononuclear iron(II) complex give materials with different spin-crossover (hereafter SCO) properties, and 2) minor modifications of the bapbpy (bapbpy=N6,N6'-di(pyridin-2-yl)-2,2'-bipyridine-6,6'-diamine) ligand allows SCO to be obtained near room temperature. We also provide a qualitative model to understand the link between the structure of bapbpy-based ligands and the SCO properties of their iron(II) compounds. Thus, seven new trans-[Fe{R(2)(bapbpy)}(NCS)(2)] compounds were prepared, in which the R(2)bapbpy ligand bears picoline (9-12), quin-2-oline (13), isoquin-3-oline (14), or isoquin-1-oline (15) substituents. From this series, three compounds (12, 14, and 15) have SCO properties, one of which (15) occurs at 288 K. The crystal structures of compounds 11, 12, and 15 show that the intermolecular interactions in these materials are similar to those found in the parent compound [Fe(bapbpy)(NCS)(2)] (1), in which each iron complex interacts with its neighbors through weak N-H···S hydrogen bonding and π-π stacking. For compounds 12 and 15, hindering groups located near the N-H bridges weaken the N-S intermolecular interactions, which is correlated to non-cooperative SCO. For compound 14, the substitution is further away from the N-H bridges, and the SCO remains cooperative as in 1 with a hysteresis cycle. Optical microscopy photographs show the strikingly different spatio-temporal evolution of the phase transition in the noncooperative SCO compound 12 relative to that found in 1. Heat-capacity measurements were made for compounds 1, 12, 14, and 15 and fitted to the Sorai domain model. The number n of like-spin SCO centers per interacting domain, which is related to the cooperativity of the spin transition, was found high for compounds 1 and 14 and low for compounds 12 and 15. Finally, we found that although both pairs of compounds 11/12 and 14/15 are pairs of isomers their SCO properties are surprisingly different.

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Section: Discussionsupporting

confidence: 84%

Tuning the Transition Temperature and Cooperativity of bapbpy‐Based Mononuclear Spin‐Crossover Compounds: Interplay between Molecular and Crystal Engineering

Arcís-Castillo

Zheng

Siegler

et al. 2011

Chemistry A European J

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“…This kind of incomplete and smooth SCO transition is typical of chain compounds, since when the metallic centers are connected, the transition of one of them exerts a chemical pressure on the bridging ligands that hampers the transition of the neighboring metal centers [45][46][47].…”

Section: Magnetic Propertiesmentioning

confidence: 99%

A Spin Crossover Transition in a Mn(II) Chain Compound

2015

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“…[1][2][3][4][5][6][7][8] In this regard, multinuclear transition metal complexes in which the bridging ligands have the potential to chelate all metal centres engenders materials with greater stability, potentially enhanced metal-metal interaction, and improved magnetic switching behaviour. [3,5,7] Improved cooperativity in switching can result in improved hysteretic behaviour and, from a device perspective, a more useful SCO system. [3,5,7] An example of such a chelating ligand, 2,2'-bipyrimidine (bpym), has been the subject of significant investigation and has been shown to form complexes with short metal-metal distances.…”

Section: Introductionmentioning

confidence: 99%

“…[3,5,7] Improved cooperativity in switching can result in improved hysteretic behaviour and, from a device perspective, a more useful SCO system. [3,5,7] An example of such a chelating ligand, 2,2'-bipyrimidine (bpym), has been the subject of significant investigation and has been shown to form complexes with short metal-metal distances. [9] For example, Real's classic Fe(II) dinuclear SCO complexes, [10,11] [{Fe(bpym)(NCE) 2 } 2 -μ-bpym] (E = S, Se) utilize bpym to facilitate spin coupling in this SCO system with short metal-metal separations of ∼5.5 Å.…”

Section: Introductionmentioning

confidence: 99%