金属串配合物[Cr_3(dpa)_4LL′](dpa=dipyridylamide;L,L′=Cl,BF_4,CCPh)的Cr―Cr成键特性  

The Cr―Cr Bonding Character of Metal String Complexes [Cr_3(dpa)_4LL′] (dpa=dipyridylamide; L,L′=Cl, BF_4, CCPh)

作　　者：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] 

机构地区：[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

出　　处：《物理化学学报》2012年第7期1637-1644,共8页Acta Physico-Chimica Sinica

基　　金：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);广州市科技攻关项目(2011J4300063)资助~~

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4中仅有三中心三电子σ键,而非对称构型1-3、5的Cr―Cr短键为三重键,非对称构型存在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的各自旋态均为对称构型.To study the configuration, the metal-metal interactions and the influence of the axial ligands L and L＇ on the Cr-Cr bond in the metal string complexes Cr3（dpa）,LL＇ （dpa = dipyridylamide; L, L＇=CI, BF4, and CCPh）, the structures of the five 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）,Cl（CCPh） （5） were investigated by density functional theory with the UBP86 functional. The results revealed that complexes with a longer average Cr-Cr bond distance tended to form a symmetrical configuration, whereas those with a shorter average Cr-Cr bond distance tended to form an asymmetric configuration. The most stable spin state was the quintet states. The complexes in quintet states with the longest average Cr- Cr distance tended to form a symmetrical configuration, whereas complexes in the septuplet spin states with the shortest Cr-Cr distance tended to form an asymmetrical configuration. For the quintet states of all complexes, there was only a 3-center-3-electron G bond in the Cr（3^（6＋）） chain. Furthermore, with the exception of the a bond, there were weak π Cr - Cr interactions in complexes 2 and 3. In the septuplet states, there was a triple bond in the short Cr-Cr bond of complexes 1-3 and 5, whereas there was only a 3-center-3-electron o bond in complex 4. In both the symmetrical and asymmetrical configurations, there were a delocalizations in the Cr（3^（6＋）） chain, suggesting that the asymmetrical metal string complexes were still the potential molecular wire species. The interactions between the axial ligand L and the Cr atom in the main, correspond to the nL→4So and nL→3d.,2cr delocalizations. For the stronger G donor -CCPh ligand, there were also ac-c→4scr delocalizations as well. The order of the bond strength of the axial ligand L and Cr atom was 2〈3〈1〈5〈4. The stronger bonding between the - CCPh ligand and Cr atom weakens the Cr-Cr bond and lengthen

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 

分 类 号：O641.4[理学—物理化学]