Département de Chimie Physique, Université de Genève, 30 Quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland.
Inorg Chem. 2011 Mar 7;50(5):1856-61. doi: 10.1021/ic102269y. Epub 2011 Jan 26.
Whereas the neat polymeric iron(II) compound Fe(bbtr)(3)(2), bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, shows a quantitative spin transition triggered by a crystallographic phase transition centered at 107 K with a 13 K wide hysteresis, the iron(II) complexes in the diluted mixed crystals Fe(x)Zn(1-x)(bbtr)(3)(2), x = 0.02 and 0.1, stay predominantly in the (5)T(2) high-spin state down to cryogenic temperatures. However, the (1)A(1) low-spin state can be populated as metastable state via irradiation into the spin-allowed (5)T(2)→(5)E ligand-field transition of the high-spin species in the near-infrared. The quantum efficiency of the light-induced conversion is approximately 10% at low temperatures and decreases rapidly above 160 K. The lifetime of the light-induced low-spin state decreases from 15 days at 40 K to 30 ns at 220 K, that is, by 14 orders of magnitude. In the high-temperature regime the activation energy for the low-spin→high-spin relaxation is 1840(20) cm(-1).
虽然规整的聚合态二价铁化合物 Fe(bbtr)(3)(2)（bbtr = 1,4-二(1,2,3-三唑-1-基)丁烷）在 107 K 处发生的以晶体相变为中心的自旋转变是定量的，具有 13 K 宽的滞后，但是在稀释混合晶体Fe(x)Zn(1-x)(bbtr)(3)(2)（x = 0.02 和 0.1）中，铁(II)配合物主要保持在低温下的(5)T(2)高自旋态。然而，(1)A(1)低自旋态可以通过辐射到近红外区高自旋物种的自旋允许的(5)T(2)→(5)E 配体场跃迁以亚稳态形式存在。低温下光诱导转化的量子效率约为 10%，在 160 K 以上迅速下降。光诱导低自旋态的寿命从 40 K 时的 15 天降至 220 K 时的 30 ns，即降低了 14 个数量级。在高温区，低自旋到高自旋弛豫的活化能为 1840(20)cm(-1)。
