摘要
采用ab initio HF,MP2方法和密度泛函理论方法,对具有D2h和D4d构型的膦配体稳定的过渡金属团簇[Au@Au8(PR3)8]3+(R=Me,OMe,H,F,Cl,CN)进行了几何结构、电子结构及团簇稳定性等方面的研究.计算表明,与D2h构型相比,D4d构型更稳定,两者能量相差约5～10 kJ/mol.SVWN局域泛函能够对团簇的几何结构给予较准确的描述,MP2方法对团簇的结构参数有所低估,而离域和杂化泛函则过高地估计了团簇的结构参数.电子结构分析表明,中心Au原子与外围的Au原子之间通过d电子的成键作用构成团簇内核[Au@Au8]3+,[Au@Au8]3+与PR3配体则通过"σ给予/π反馈"模式成键.PR3配体与[Au@Au8]3+的结合能够加强内核-外围Au原子间的成键作用,缩小外围Au原子在成键上的差异,增大前线轨道能级间隙,从而提高团簇的稳定性.PR3配体中R基团供、吸电子能力的变化对[Au@Au8(PR3)8]3+结构影响较小,但对[Au@Au8]3+-PR3结合能影响较大.能量分析显示,不同PR3配体与[Au@Au8]3+之间具有相近的轨道作用能,与R基团供、吸电子能力相关的非轨道作用能成为影响两者连接牢固程度的决定因素.
The molecular geometric and electronic structures of phosphine-stabilized transition-metal cluster [Au@Au8（PR3）8]3＋（R = Me, OMe, H, F, Cl, CN） were investigated by means of ab initio HF, MP2 and density functional theory（DFT） methods. The bonding energies of Au＋-Au82＋/Au8（PR3）82＋ and [Au@Au8]3＋-PR3 were also analyzed on the basis of calculations. The calculation results show that the D4d conformations of [Au@Au8（PR3）8]3＋ are more stable than the D2h conformations by 5-10 kJ/mol. The local density functio-nal SVWN methods have good performance in reproducing the experimental geometric features. The MP2 calculations underestimate the bond lengths of clusters, while the non-local exchange-correlation functionals and hybrid functionals tend to overestimate the bond lengths. The studies of the electronic structures show that the metal cluster core [Au@Au8]3＋ is formed by the d-d electron interaction of Au atoms. The bonding of [Au@Au8]3＋-PR3 complexes can be described as a synergistic combination of σ-donor and π-acceptor interactions between [Au@Au8]3＋ and PR3 ligands. Adding the PR3 ligands can increase the bonding interaction of Au＋-Au82＋ and the HOMO-LUMO gap, and reduce the differences of bonding properties between the external Au atoms. Therefore, the stability of the cluster is increased. It is found that the effect of the electron donating or withdrawing ability of PR3 groups on the geometries of [Au@Au8（PR3）8]3＋ is small, but that on the bonding energies of [Au@Au8]3＋-PR3 is large. The energy decomposition analysis results show that the orbital interaction energies of the [Au@Au8]3＋-PR3 bonding are very close to each other, so the magnitude of the non-orbital interaction energy plays a crucial role in the stabilization of [Au@Au8（PR3）8]3＋ complexes.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第11期2549-2555,共7页
Chemical Journal of Chinese Universities
基金
国家自然科学基金(批准号:20973109)资助
关键词
过渡金属团簇
从头算
密度泛函理论
电子结构
能量分解分析
Transition-metal cluster
Ab initio
Density functional theory
Electronic structure
Energy decomposition analysis
