58031-48-4Relevant academic research and scientific papers
X-ray absorption fine structure study of the structural changes accompanying spin cross-over in the acetone solvates of [Fe(dppen)2X2] [dppen = cis-1,2-bis(diphenylphosphino)ethylene; X = Cl or Br]
Young, Nigel A.
, p. 1275 - 1281 (1996)
Iron and bromine K-edge X-ray absorption fine structure (XAFS) have been used to determine the changes in the local iron environment in [Fe(dppen)2Br2]·2Me2CO on going through the spin cross-over transition at 160-185 K. The mean Fe-P bond length decreases from the high- to the low-spin isomer by 0.29 A [2.60(3) to 2.31(3) A], whereas the mean Fe-Br bond length decreases by only ca. 0.02 A [2.51(3) to 2.48(3), iron K-edge; 2.48(3) to 2.47(3) A, bromine K-edge]. Iron K-edge XAFS for [Fe(dppen)2Cl2]·2Me2CO showed a reduction of 0.28 A in the mean Fe-P distance [2.55(3) to 2.27(3) A] and a reduction of 0.02 A in the mean Fe-Cl bond length [2.33(3) to 2.31 (3) A] on going from the high- to the low-spin form, in good agreement with literature values, the spin transition being observed at 220-240 K.
Pressure-induced spin-state phase transitions in Fe(dppen)2Cl2 and Fe(dppen)2Br2
McCusker, James K.,Zvagulis, Maruta,Drickamer, Harry G.,Hendrickson, David N.
, p. 1380 - 1384 (2008/10/08)
The pressure-induced high-spin to low-spin transformation in solid Fe(dppen)2X2, where X = Cl or Br and dppen = cis-1,2-bis(diphenylphosphino)ethylene, has been studied by variable-pressure M?ssbauer spectroscopy. It is found that the dichloro complex undergoes an abrupt first-order phase transition in the region of 7-9 kbar, while the dibromo complex undergoes a more gradual transition starting at approximately 60 kbar. The somewhat more gradual nature of the transformation in the dibromo case likely reflects a first-order phase transition influenced by defect structures. In neither compound is the transition complete: approximately 20% of the molecules remain in the high-spin state for each compound at the highest pressures studied (70 kbar for the dichloro complex and 111 kbar for the dibromo complex). The difference in transition pressures is discussed in terms of lattice cooperativity, in addition to ligand field and polarizability effects manifested with increasing pressure.
