Synthesis, Crystal Structure, EXAFS, and Magnetic Properties of Catena [-Tris(1,2-bis(tetrazol-1-yl)propane-N1,N1')iron(
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- 作者：Petra J. van Koningsbruggen ; Yann Garcia ; Olivier Kahn ; Lé ; opold Fournè ; s ; Huub Kooijman ; Anthony L. Spek ; Jaap G. Haasnoot ; Jacques Moscovici ; Karine Provost ; Alain Michalowicz ; Franz Ren
- 刊名：Inorganic Chemistry
- 出版年：2000
- 出版时间：May 1, 2000
- 年：2000
- 卷：39
- 期：9
- 页码：Gütlich
- 全文大小：168K
- 年卷期：v.39,no.9(May 1, 2000)
- ISSN：1520-510X
文摘
[Fe(btzp)3](ClO4)2 (btzp = 1,2-bis(tetrazol-1-yl)propane) represents the first structurally characterized Fe(II) linearchain compound exhibiting thermal spin crossover. It shows a very gradual spin transition (T1/2 = 130 K) whichhas been followed by magnetic susceptibility measurements and 57Fe Mössbauer spectroscopy. The structure hasbeen solved at 200 and 100 K by single-crystal X-ray analysis. It crystallizes in the trigonal space group P
c1with Z = 2 Fe(II) units at both temperatures. The molecular structure consists of chains running along the c axisin which the Fe(II) ions are linked by three N4,N4' coordinating bis(tetrazole) ligands. The main difference betweenthe two forms appears to be in the Fe-N bond lengths, which are 2.164(4) Å at 200 K and 2.038(4) Å at 100 K.The Fe-Fe separations are 7.422(1) Å at 200 K and 7.273(1) Å at 100 K. The EXAFS results are consistent withthe crystal structure. In both spin states, the FeN6 octahedron is almost regular within the EXAFS resolution. TheFe-N distance is found as 2.16(2) Å at 300 K and 2.00(2) Å at 40 K. The absence of the "7 Å peak" in theEXAFS spectra of [Fe(btzp)3](ClO4)2, in contrast with what has been observed for the [Fe(4-R-1,2,4-triazole)3](anion)2 chain compounds, confirms that this peak can be used as the signature of a metal alignment only whenit involves a strongly enhanced multiple scattering M-M-M path, with M-M spacing less than 4 Å. Irradiationwith green light at 5 K has led to the population of the metastable high-spin state for the iron(II) ion. The natureof the spin-crossover behavior has been discussed on the basis of the structural features.
c1with Z = 2 Fe(II) units at both temperatures. The molecular structure consists of chains running along the c axisin which the Fe(II) ions are linked by three N4,N4' coordinating bis(tetrazole) ligands. The main difference betweenthe two forms appears to be in the Fe-N bond lengths, which are 2.164(4) Å at 200 K and 2.038(4) Å at 100 K.The Fe-Fe separations are 7.422(1) Å at 200 K and 7.273(1) Å at 100 K. The EXAFS results are consistent withthe crystal structure. In both spin states, the FeN6 octahedron is almost regular within the EXAFS resolution. TheFe-N distance is found as 2.16(2) Å at 300 K and 2.00(2) Å at 40 K. The absence of the "7 Å peak" in theEXAFS spectra of [Fe(btzp)3](ClO4)2, in contrast with what has been observed for the [Fe(4-R-1,2,4-triazole)3](anion)2 chain compounds, confirms that this peak can be used as the signature of a metal alignment only whenit involves a strongly enhanced multiple scattering M-M-M path, with M-M spacing less than 4 Å. Irradiationwith green light at 5 K has led to the population of the metastable high-spin state for the iron(II) ion. The natureof the spin-crossover behavior has been discussed on the basis of the structural features.