Rannulu N S, Rodgers M T
Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
J Phys Chem A. 2007 May 10;111(18):3465-79. doi: 10.1021/jp066903h. Epub 2007 Apr 18.
Collision-induced dissociation of complexes of Cu+ bound to a variety of N-donor ligands (N-L) with Xe is studied using guided ion beam tandem mass spectrometry. The N-L ligands examined include pyridine, 4,4-dipyridyl, 2,2-dipyridyl, and 1,10-phenanthroline. In all cases, the primary and lowest-energy dissociation channel observed corresponds to the endothermic loss of a single intact N-L ligand. Sequential dissociation of additional N-L ligands is observed at elevated energies for the pyridine and 4,4-dipyridyl complexes containing more than one ligand. Ligand exchange processes to produce Cu+Xe are also observed as minor reaction pathways in several systems. The primary cross section thresholds are interpreted to yield 0 and 298 K bond dissociation energies (BDEs) after accounting for the effects of multiple ion-neutral collisions, the kinetic and internal energy distributions of the reactants, and dissociation lifetimes. Density functional theory calculations at the B3LYP/6-31G* level are performed to obtain model structures, vibrational frequencies, and rotational constants for the neutral N-L ligands and the Cu+(N-L)x complexes. The relative stabilities of the various conformations of these N-L ligands and Cu+(N-L)x complexes as well as theoretical BDEs are determined from single point energy calculations at the B3LYP/6-311+G(2d,2p) level of theory using B3LYP/6-31G* optimized geometries. Excellent agreement between theory and experiment is observed for all complexes containing one or two N-L ligands, while theory systematically underestimates the strength of binding for complexes containing more than two N-L ligands. The ground-state structures of these complexes and the trends in the sequential BDEs are explained in terms of stabilization gained from sd-hybridization and repulsive ligand-ligand interactions. The nature of the binding interactions in the Cu+(N-L)x complexes are examined via natural bond orbital analyses.
利用导向离子束串联质谱法研究了与多种含氮供体配体（N-L）结合的Cu⁺配合物与Xe的碰撞诱导解离。所研究的N-L配体包括吡啶、4,4-联吡啶、2,2-联吡啶和1,10-菲咯啉。在所有情况下，观察到的主要且能量最低的解离通道对应于单个完整N-L配体的吸热损失。对于含有多个配体的吡啶和4,4-联吡啶配合物，在较高能量下观察到了额外N-L配体的顺序解离。在几个体系中，还观察到了生成Cu⁺Xe的配体交换过程作为次要反应途径。在考虑了多次离子-中性碰撞的影响、反应物的动能和内能分布以及解离寿命后，对主要截面阈值进行了解释，以得出0和298K时的键解离能（BDE）。在B3LYP/6-31G水平上进行密度泛函理论计算，以获得中性N-L配体和Cu⁺(N-L)ₓ配合物的模型结构、振动频率和转动常数。这些N-L配体和Cu⁺(N-L)ₓ配合物的各种构象的相对稳定性以及理论BDE是在B3LYP/6-31G优化几何结构的基础上，通过在B3LYP/6-311+G(2d,2p)理论水平上的单点能量计算确定的。对于所有含有一个或两个N-L配体的配合物，理论与实验结果吻合良好，而对于含有两个以上N-L配体的配合物，理论系统地低估了其结合强度。这些配合物的基态结构和顺序BDE的趋势是根据sd杂化获得的稳定性和排斥性配体-配体相互作用来解释的。通过自然键轨道分析研究了Cu⁺(N-L)ₓ配合物中结合相互作用的性质。
