物理化学学报 >> 2012, Vol. 28 >> Issue (07): 1637-1644.doi: 10.3866/PKU.WHXB201204111

理论与计算化学 上一篇    下一篇

金属串配合物[Cr3(dpa)4LL'](dpa=dipyridylamide; L, L'=Cl, BF4, CCPh)的Cr—Cr成键特性

马华璇1, 郑燕玲1, 詹益仕1, 谭莹1, 黄晓1, 彭琦1, 许旋1,2,3,4   

  1. 1. 华南师范大学化学与环境学院, 广州 510006;
    2. 教育部环境理论化学重点实验室, 广州 510006;
    3. 广东省高校电化学储能与发电技术重点实验室, 广州 510006;
    4. 华南师范大学, 电化学储能材料与教育技术教育部工程研究中心, 广州 510006
  • 收稿日期:2012-02-23 修回日期:2012-04-10 发布日期:2012-06-07
  • 通讯作者: 许旋 E-mail:xuxuan@scnu.edu.cn
  • 基金资助:

    广东省自然科学资金项目(9151063101000037), 广东省教育部产学研项目(2010B090400184), 广东省人才引进专项资金(C10133)和广州市科技攻关项目(2011J4300063)资助

The Cr—Cr Bonding Character in Metal String Complexes [Cr3(dpa)4LL'] (dpa=dipyridylamide; L, L'=Cl, BF4, CCPh)

MA Hua-Xuan1, ZHENG Yan-Ling1, ZHAN Yi-Shi1, TAN Ying1, HUANG Xiao1, PENG Qi1, XU Xuan1,2,3,4   

  1. 1. School of Chemistry & Environment, South China Normal University, Guangzhou 510006, P. R. China;
    2. Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, Guangzhou 510006, P. R. China;
    3. Key Laboratory of Electrochemical Technology on Energy Storage and Power Generation in Guangdong Universities, Guangzhou 510006, P. R. China;
    4. Engineering Research Center of Materials and Technology for Electrochemical Energy Storage, Ministry of Education, South China Normal University, Guangzhou 510006, P. R. China
  • Received:2012-02-23 Revised:2012-04-10 Published:2012-06-07
  • Contact: XU Xuan E-mail:xuxuan@scnu.edu.cn
  • Supported by:

    The project was supported by the Natural Science Foundation of Guangdong Province, China (9151063101000037), Ministry of Education of Guangdong Province, China (2010B090400184), Program of Talent Introduction of Guangdong Province, China (C10133), Science and Technology Program of Guangzhou City, China (2011J4300063).

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摘要：

采用密度泛函理论UBP86方法计算了Cr3(dpa)4Cl2 (1)、Cr3(dpa)4(BF4)2 (2)、Cr3(dpa)4Cl(BF4) (3)、Cr3(dpa)4(CCPh)2 (4)和Cr3(dpa)4Cl(CCPh) (5)金属串配合物的结构, 并对配合物的构型、Cr—Cr键的本质以及轴向配体对Cr—Cr键的影响进行了研究. 结果表明: (1) Cr—Cr平均键长较长的配合物趋于形成对称构型, 较短时趋于形成非对称构型. 最稳定的五重态的Cr—Cr平均键长最长, 故优化时趋于形成对称构型; 七重态的Cr—Cr平均键长最短, 趋于形成非对称构型; (2) 五重态的Cr36+金属链均存在三中心三电子σ键, 含弱σ给电子轴向配体BF4-的2和3的Cr—Cr短键还具有弱的π相互作用. 七重态下, 对称构型的4中仅有三中心三电子σ键, 而非对称构型的1-3、5的Cr—Cr短键为三重键, 非对称构型仍具有Cr36+链的σ离域作用, 仍具有分子导线的潜在应用; (3) 轴向配体L与Cr的作用主要表现为nL→4sCr或nL→3dz2Cr离域, 较强的σ给电子配体CCPh-还存在σC—C→4sCr离域. Cr与L的结合强度为2＜3＜1＜5＜4, CCPh-与Cr的结合最强, 使Cr—Cr键减弱、Cr—Cr距离增长, 故4的各自旋重态均为对称构型.

关键词: 金属串配合物, 密度泛函理论, 自然键轨道分析, M—M相互作用

Abstract:

To study the configuration, the metal-metal interactions and the influences of axial ligands L and L' on the Cr—Cr bond in metal string complexes Cr3(dpa)4LL' (L, L'=Cl, BF4, CCPh), the structures of complexes Cr3(dpa)4Cl2 (1), Cr3(dpa)4(BF4)2 (2), Cr3(dpa)4Cl(BF4) (3), Cr3(dpa)4(CCPh)2 (4) and Cr3(dpa)4Cl(CCPh) (5) were investigated by density functional theory UBP86 method. The conclusions can be drawn as follows: (1) The complex with longer average Cr—Cr distance tends to form a symmetrical configuration, while it tends to form a asymmetric configuration with shorter average Cr—Cr distance. The most stable spin states, quintet states, with the longest average Cr—Cr distance tend to form a symmetrical configuration, while septuplet states with shortest Cr—Cr distance tend to form asymmetrical one; (2) For quintet states of all complexes, there is only a 3-center-3-electron σ bond in Cr36+ chain. Furthermore, except the σ bond, there are weak π Cr—Cr interactions in complex 2 and 3. For septuplet states, there is a triple bond in the short Cr—Cr bond of complexes 1-3 and 5, while there is only a 3-center-3-electron σ bond in complex 4. Not only in symmetrical configuration but also in asymmetric configuration, there are σ delocalizations in Cr36+ chain, suggesting the asymmetrical metal string complexes are still the potential molecular wire species; (3) The interactions between axial ligand L and Cr atom mainly correspond to the nL→4sCr and nL→3dz2Cr delocalizations. In addition, for stronger σ donor CCPh- ligand, there are σC—C→4sCr delocalizations as well. The order of the bond strength of axial ligand L and Cr atom is 2＜3＜1＜5＜4. The strongest bonding between CCPh- ligand and Cr atom weakens the Cr—Cr bond and lengthens the Cr—Cr distance. Therefore, every spin state of 4 tends to form a symmetrical configuration.

Key words: Metal string complexes, Density functional theory, Natural bond orbital, Metal-metal interaction