One- and Two-Step Spin-Crossover Behavior of [FeII(isoxazole)6]2+ and the Structure and Magnetic Properties of Triangular [FeIII3O(OAc)6
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- 作者：Wendy Hibbs ; Petra J. van Koningsbruggen ; Atta M. Arif ; William W. Shum ; and Joel S. Miller
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：September 8, 2003
- 年：2003
- 卷：42
- 期：18
- 页码：5645 - 5653
- 全文大小：418K
- 年卷期：v.42,no.18(September 8, 2003)
- ISSN：1520-510X
文摘
The structure and spin-crossover magnetic behavior of [FeII16][BF4]2 (1 = isoxazole) and [FeII16][ClO4]2 have beenstudied. [FeII16][BF4]2 undergoes two reversible spin-crossover transitions at 91 and 192 K, and is the first two-stepspin transition to undergo a simultaneous crystallographic phase transition, but does not exhibit thermal hysteresis.The single-crystal structure determinations at 260 [space group P
images/entities/thremacr.gif">, a = 17.4387(4) Å, c = 7.6847(2) Å] and at130 K [space group Pimages/entities/onemacr.gif">, a = 17.0901(2) Å, b = 16.7481(2) Å, c = 7.5413(1) Å, images/gifchars/alpha.gif" BORDER=0> = 90.5309(6)images/entities/deg.gif">, images/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 91.5231(6)images/entities/deg.gif">,images/gifchars/gamma.gif" BORDER=0 > = 117.8195(8)images/entities/deg.gif">] reveal two different iron sites, Fe1 and Fe2, in a 1:2 ratio. The room-temperature magneticmoment of 5.0 images/entities/mgr.gif">B is consistent with high-spin Fe(II). A plateau in images/entities/mgr.gif">(T) having a moment of 3.3 images/entities/mgr.gif">B centered at 130K suggests a mixed spin system of some high-spin and some low-spin Fe(II) molecules. On the basis of the Fe-Nbond distances at the two temperatures, and the molar fraction of high-spin molecules at the transition plateau,Fe1 and Fe2 can be assigned to the 91 and 192 K transitions, respectively. [FeII16][ClO4]2 [space group Pimages/entities/thremacr.gif">, a =17.5829(3) Å, c = 7.8043(2) Å, images/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 109.820 (3)images/entities/deg.gif">, T = 295 K] also possesses Fe1:Fe2 in a 1:2 ratio, andmagnetic measurements show a single spin transition at 213 K, indicating that both Fe1 and Fe2 undergo asimultaneous spin transition. [FeII16][ClO4]2 slowly decomposes in solutions containing acetic anhydride to form[FeIII3O(OAc)613][ClO4] [space group I2, a = 10.1547(7) Å, b = 16.5497(11) Å, c = 10.3205(9) Å, images/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 109.820(3)images/entities/deg.gif">, T = 200 K]. The isosceles Fe3 unit contains two Fe···Fe distances of 3.2844(1) Å and a third Fe···Fedistance of 3.2857(1) Å. The magnetic data can be fit to a trinuclear model with H = -2J(S1·S2 + S2·S3) -2J13(S1·S3), where J = -27.1 and J13 = -32.5 cm-1.