Density functional study of the valence-tautomeric interconversion low-spin [Co-III(SQ)(Cat)(phen)] reversible arrow high-spin [Co-II(SQ)(2)(phen)]
Density functional study of the valence-tautomeric interconversion low-spin [Co-III(SQ)(Cat)(phen)] reversible arrow high-spin [Co-II(SQ)(2)(phen)]
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DOI：
10.1021/ic9611812
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发表时间：
1997-08-27
影响因子：
4.6
通讯作者：
Hendrickson, DN
中科院分区：
文献类型：
--
作者：
Adams, DM;Noodleman, L;Hendrickson, DN
采用自洽场（SCF）非定域密度泛函分子轨道方法，计算了钴与邻醌衍生配体配合物的各种自旋态和互变异构形式.此外，新的变温溶液的磁化率，EPR，和电子吸收数据的特点低自旋[钴-III（3，5-DTBSQ）（3，5-DTBCat）（phen）]到高自旋[Co-II（3，5-DTBSQ）（2）-（phen）]化合价互变异构体互变，其中3，5-DTBSQ（-）和3，5-DTBCat（2-）是3的半醌酸盐和儿茶酚盐形式，5-二叔丁基-邻苯醌，phen为1，10-菲咯啉。对溶液磁化率数据进行拟合，得到ls-Co-III可逆箭hs-Co-II平衡的Δ H = 2238 cm（-1）和Δ S = 118.1 J mol（-1）K-1。随着两种互变异构形式之间的复合物变化，在电子吸收光谱中观察到明显的变化。非限制性SCF计算得到J = -594 cm（-1），这是表征hs-Co-II离子（S = 3/2）与hs-Co-II互变异构体中两个半醌配体（S = 1/2）之间的反铁磁交换相互作用的参数。计算结果表明，ls-Co-II互变异构体状态是最稳定的，在该ls-Co-III状态和hs-Co-II自旋梯的S = 1/2组分之间的能量分离Δ E = 4428 cm（-1）（0.55 eV）。该Δ E值与从变温敏感性数据评估的Δ H值相比是有利的。计算结果表明，虽然仍然有本地化的电子结构特征，反映不同的金属和配体的氧化态的ls-Co-III和hs-Co-II互变异构体的形式，明显的共价相互作用之间存在的钴离子和配体。最后，计算的结果被用来分配的ls-Co-III和hs-Co-II互变异构体的电子跃迁。
The results of self-consistent field (SCF) nonlocal density functional molecular orbital calculations are presented for the various spin states and tautomeric forms of a cobalt complex with two o-quinone-derived ligands. In addition, new variable-temperature solution magnetic susceptibility, EPR, and electronic absorption data are presented to characterize the low-spin [Co-III(3,5-DTBSQ)(3,5-DTBCat)(phen)] to high-spin [Co-II(3,5-DTBSQ)(2)-(phen)] valence-tautomeric interconversion, where 3,5-DTBSQ(-) and 3,5-DTBCat(2-) are the semiquinonate and catecholate forms of 3,5-di-tert-butyl-o-benzoquinone, respectively, and phen is 1,10-phenanthroline. The solution magnetic susceptibility data were fitted to give Delta H = 2238 cm(-1) and Delta S = 118.1 J mol(-1) K-1 for the ls-Co-III reversible arrow hs-Co-II equilibrium. Appreciable changes are seen in the electronic absorption spectrum as the complex changes between the two tautomeric forms. Unrestricted SCF calculations gave J = -594 cm(-1) for the parameter characterizing the antiferromagnetic exchange interaction between hs-Co-II ion (S = 3/2) and each of the two coordinated semiquinonate (S = 1/2) ligands in the hs-Co-II tautomer. The calculations indicated that the ls-Co-II tautomer state is the most stable with an energy separation of Delta E = 4428 cm(-1) (0.55 eV) between this ls-Co-III state and the S = 1/2 component of the hs-Co-II spin ladder. This Delta E value compares favorably with the Delta H value evaluated from variable-temperature susceptibility data. The calculations indicate that, while there are still localized electronic structural features reflecting the different metal and ligand oxidation states in the ls-Co-III and hs-Co-II tautomeric forms, appreciable covalent interactions exist between the cobalt ion and the ligands. Finally, the results of the calculations were used to assign the electronic transitions seen for the ls-Co-III and hs-Co-II tautomers.