Spin state of cobalt(II) in five- and six-coordinate Lewis base adducts of (N,N'-ethylenebis(3-carboxysalicylaldiminato)cobalt(II). New spin-crossover complexes
Spin state of cobalt(II) in five- and six-coordinate Lewis base adducts of (N,N'-ethylenebis(3-carboxysalicylaldiminato)cobalt(II). New spin-crossover complexes
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(N,N-乙烯双(3-羧基水杨醛二胺)钴(II)的五配位和六配位路易斯碱加合物中钴(II)的自旋态。新的自旋交叉配合物
DOI：
10.1021/ic00232a020
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发表时间：
1986
影响因子：
4.6
通讯作者：
J. Zarembowitch
中科院分区：
文献类型：
--
作者：
P. Thuéry;J. Zarembowitch
3-Me 2 py、3-NH_2py和3，5-Me_2py表现出主要的高自旋行为。假设在四重基态（4A 2g）和第一激发二重态（2A 1g）之间存在自旋混合，这两个态（）之间的能隙和由4A 2g（5）产生的Kramers二重态之间的能隙可以估计为~ 550-600 cm™ 1和~ 95-115 cm™ 1。具有L= 4-M-Bupy和L= 4-Z-Bupy的化合物表现出5= 3/2-5=*/2交叉。在第一种情况下，这种跃迁是连续型的，热力学计算表明，正如预期的那样，协同效应可以忽略不计;计算的上限为194 cm™ 1，基态是自旋二重态。相比之下，后者的配合物的自旋转换是有史以来最突然的Co（II）配合物中观察到的，并提出了一个滞后约。16 K，在降温和升温时，Tct分别集中在138 K和154 K。顶端配体的性质对Co（II）的自旋状态的影响进行了讨论，在捐助者的能力，方向的吡啶环，和空间位阻的要求。
3-Mepy, 3-NH2py, and 3, 5-Me2py present a predominant high-spin behavior. Assuming the existence of a spin admixing between the quartet ground state (4A2g) andthe first excited doublet state (2Alg), the energy gaps between these two states () and between the Kramers doublets arising from 4A2g (5) could be estimated as~ 550-600 cm™ 1 and~ 95-115 cm™ 1. Compounds with L= 4-Mepy and L= 4-Z-Bupy exhibit a 5= 3/2—5=*/2 crossover. In the first case, this transition is of the continuous type and thermodynamic calculations show, as expected, that cooperativeeffects are negligible; an upper limit of 194 cm™ 1 is calculated for, the ground state being then a spin doublet. By contrast, the spin conversion of the latter complex is one of the most abrupt ever observed in Co (II) complexes and presents a hysteresis of ca. 16 K, being centeredat Tc\= 138 K and Tct= 154 K for decreasing and increasing temperatures, respectively. The effect of the nature of apical ligands on the spin state of Co (II) is discussed in terms of-donor ability, orientation of the pyridine ring, and steric requirements.