Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Phys Chem Chem Phys. 2018 May 16;20(19):13348-13356. doi: 10.1039/c8cp00865e.
Nitric oxide plays an important role in several physiological processes. This study investigates model ruthenium ammine coordination compounds to control NO bioavailability: cis-[RuCl(NO)(NH3)4]+ (1+), cis-[RuCl(NO)(NH3)4]2+ (12+), cis-[RuCl(NO)(NH3)4]3+ (13+), trans-[RuCl(NO)(NH3)4]+ (2+), trans-[RuCl(NO)(NH3)4]2+ (22+), trans-[RuCl(NO)(NH3)4]3+ (23+), [Ru(NO)(NH3)5]+ (3+), [Ru(NO)(NH3)5]2+ (32+), and [Ru(NO)(NH3)5]3+ (33+). We employed natural population analysis (NPA) atomic charges (qNPA) and the LUMO to identify the main reduction sites in the complexes 1, 2 and 3. For example, in the transformations 12+ → 1+, 22+ → 2+, and 33+ → 32+, the main reduction site was a NO π* orbital, which accounted for the lower electron density of the Ru-NO bond critical point (BCP) in 1+, 2+, and 32+ than 12+, 22+, and 33+, respectively, as shown by the quantum theory of atoms in molecules (QTAIM). The QTAIM method indicated that the electron density was larger in Ru-NO BCP due to the Cl negative cis- and trans-influence in 12+ and 22+, respectively, as compared with the NH3 influence in 33+. Compared to trans-Cl-Ru-NO in 22+, the interacting quantum atoms method demonstrated that cis-Cl-Ru-NO in 12+ displayed (i) a larger repulsive electrostatic energy, which agreed with qNPA, and (ii) a less negative exchange-correlation energy between Ru and the NO nitrogen atom, which agreed with topological analyses performed by the QTAIM method. Thus, the combination of topological and energy decomposition analyses allowed the mechanism behind the Ru-NO bond to be revealed regarding the influence of the total charge and the relative position of the ligands.
一氧化氮在许多生理过程中发挥着重要作用。本研究调查了模型钌氨配位化合物以控制 NO 生物利用度：顺式-[RuCl(NO)(NH3)4]+(1+)、顺式-[RuCl(NO)(NH3)4]2+(12+)、顺式-[RuCl(NO)(NH3)4]3+(13+)、反式-[RuCl(NO)(NH3)4]+(2+)、反式-[RuCl(NO)(NH3)4]2+(22+)、反式-[RuCl(NO)(NH3)4]3+(23+)、[Ru(NO)(NH3)5]+(3+)、[Ru(NO)(NH3)5]2+(32+)和[Ru(NO)(NH3)5]3+(33+)。我们采用自然键轨道分析（NBO）原子电荷（qNPA）和最低未占据轨道（LUMO）来识别配合物 1、2 和 3 中的主要还原位点。例如，在 12+→1+、22+→2+和 33+→32+的转化中，主要的还原位点是一个 NO π*轨道，这导致 Ru-NO 键临界点（BCP）的电子密度在 1+、2+和 32+中低于 12+、22+和 33+，正如分子中的原子量子理论（QTAIM）所示。QTAIM 方法表明，由于 Cl 的负顺式和反式影响，12+和 22+中的 Ru-NO BCP 中的电子密度更大，而 33+中的 NH3 影响较小。与 22+中的反式-Cl-Ru-NO 相比，相互作用量子原子方法表明，12+中的顺式-Cl-Ru-NO 表现出（i）更大的排斥静电能，这与 qNPA 一致，以及（ii）Ru 和 NO 氮原子之间的交换相关能量更负，这与通过 QTAIM 方法进行的拓扑分析一致。因此，拓扑和能量分解分析的结合允许揭示 Ru-NO 键背后的机制，涉及总电荷和配体相对位置的影响。
