Structural Properties of M(dmit)(2)-Based (M = Ni, Pd, Pt; dmit(2)(-) = 2-Thioxo-1,3-dithiole-4,5-dithiolato) Molecular Metals. Insights from Density Functional Calculations.
Structural Properties of M(dmit)(2)-Based (M = Ni, Pd, Pt; dmit(2)(-) = 2-Thioxo-1,3-dithiole-4,5-dithiolato) Molecular Metals. Insights from Density Functional Calculations.
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M(dmit)(2) 基（M = Ni、Pd、Pt；dmit(2)(-) = 2-Thioxo-1,3-dithiole-4,5-dithiolato）分子金属的结构性质。
作者：
A. Rosa;G. Ricciardi;E. Baerends
利用空间排斥、电子对键形成和供体-受体相互作用中的相互作用能的分解，分析了叠层中两个M（dmit）（2）单体（M = Ni，Pd，Pt）之间的键合，这是这些化合物晶体结构的特征。如果满足两个条件，则可能发生原子上原子（重叠）堆叠：（a）HOMO到LUMO激发能应该足够小，使得这些单占据轨道都可以与它们在相邻单体上的配偶体形成电子对键。HOMO和LUMO都是基于配体的，电子对键在配体之间而不是在金属之间。(b)为了消除空间位阻而使配体体系弯曲不应消耗太多能量。这些情况在Pt（dmit）（2）中占主导地位，其中相对论效应通过增强金属上具有6s、7s和6p（z）（）特征的虚轨道的受体能力来增加重叠构象的稳定性，以便从被占据的相邻d（z）（）2中提供电子。在Ni（dmit）（2）中，激发能稍高，弯曲更不利;因此，它不表现出重叠堆叠图案。滑移是另一种减轻相邻单体之间的空间排斥的方式。在这种情况下，电子对键被破坏，但两个配体系统之间仍然存在足够的供体-受体相互作用，使其成为Ni（dmit）（2）的可行替代方案。Pd（dmit）（2）介于两者之间，可能采用重叠或滑动构型。
The bonding between two M(dmit)(2) monomers (M = Ni, Pd, Pt) in the stacks that are characteristic for the crystal structure of these compounds has been analyzed, using decomposition of the interaction energy in steric repulsion, electron pair bond formation, and donor-acceptor interactions. Atom over atom (eclipsed) stacking may occur if two conditions are met: (a) The HOMO to LUMO excitation energy should be small enough so that these singly occupied orbitals may both form an electron pair bond with their partner on the adjacent monomer. The HOMO and LUMO both being ligand based, the electron pair bonds are between the ligands and not between the metals. (b) The bending away of the ligand systems so as to relieve the steric hindrance should not cost too much energy. These circumstances prevail in Pt(dmit)(2), where relativistic effects increase the stability of the eclipsed conformation by enhancing the acceptor capability of the virtual orbitals with 6s, 7s, and 6p(z)() character on the metal for electron donation out of the occupied adjacent d(z)()()2. In Ni(dmit)(2) both the excitation energy is somewhat higher and the bending is more unfavorable; consequently, it does not exhibit the eclipsed stacking pattern. Slipping is another way to relieve the steric repulsion between adjacent monomers. The electron pair bonds are broken in that case, but sufficient donor-acceptor interactions between the two ligand systems remain to make this a viable alternative for Ni(dmit)(2). Pd(dmit)(2) is in between and may adopt either eclipsed or slipped configurations.