Fatmi M Qaiser, Hofer Thomas S, Randolf Bernhard R, Rode Bernd M
Theoretical Chemistry Division, Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.
J Phys Chem B. 2007 Jan 11;111(1):151-8. doi: 10.1021/jp0654213.
In the context of our detailed study of the chemical behavior of aquo- and ammine-Zn(II) complexes, ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations were performed at the Hartree-Fock (HF) level for the zinc(II)-diamine complexes in aqueous solution. The initial structures of cis and trans isomers of the tetraaquodiamminezinc(II) complex were found to transform into the triaquodiamminezinc(II) complex by releasing one water ligand after approximately 6 and approximately 22 ps of simulation time, respectively. The structural and dynamical properties of these three zinc complexes, i.e., cis-[Zn(NH3)2(H2O)4]2+, trans-[Zn(NH3)2(H2O)4]2+, and [Zn(NH3)2(H2O)3]2+, were analyzed in terms of radial distribution functions (RDF), coordination number distributions (CND), angular distribution functions (ADF), tilt and theta angle distributions, ligands' mean residence times (MRTs), and ion-ligand stretching frequencies. One considerably elongated Zn-O bond of 2.43 A was observed in the case of the cis isomer for one of the water ligands located in the trans position to an ammonia ligand. In the trans isomer the average Zn-O bond length was observed to be 2.23 A, while in the triaquodiamminezinc(II) complex two distinct Zn-O bonds, namely 2.12 A for the ligands in the trigonal plane and 2.26 A for axial water molecules, were observed. As both of the octahedral isomers are transformed into the pentacoordinated structure within the picosecond range, they might be regarded as "metastable species or intermediates", while the triaquodiamminezinc(II) complex is the most stable species of the zinc(II)-diamine complex in aqueous solution.
在我们对水合和氨合锌（II）配合物化学行为的详细研究中，在Hartree-Fock（HF）水平上对水溶液中的锌（II）-二胺配合物进行了从头算量子力学/分子力学（QM/MM）分子动力学（MD）模拟。发现四水二氨合锌（II）配合物的顺式和反式异构体的初始结构在模拟时间分别约为6皮秒和约22皮秒后，通过释放一个水配体转化为三水二氨合锌（II）配合物。根据径向分布函数（RDF）、配位数分布（CND）、角分布函数（ADF）、倾斜角和θ角分布、配体的平均停留时间（MRT）以及离子-配体伸缩频率，分析了这三种锌配合物，即顺式-[Zn(NH3)2(H2O)4]2+、反式-[Zn(NH3)2(H2O)4]2+和[Zn(NH3)2(H2O)3]2+的结构和动力学性质。在顺式异构体中，对于位于与氨配体反位的一个水配体，观察到一个相当长的Zn-O键，键长为2.43 Å。在反式异构体中，观察到平均Zn-O键长为2.23 Å，而在三水二氨合锌（II）配合物中，观察到两个不同的Zn-O键，即三角平面内配体的键长为2.12 Å，轴向水分子的键长为2.26 Å。由于两种八面体异构体在皮秒范围内都转化为五配位结构，它们可能被视为“亚稳物种或中间体”，而三水二氨合锌（II）配合物是水溶液中锌（II）-二胺配合物中最稳定的物种。
