Cáceres-Vásquez Joaquín, Jara Danilo H, Costamagna Juan, Martínez-Gómez Fabián, Silva Carlos P, Lemus Luis, Freire Eleonora, Baggio Ricardo, Vera Cristian, Guerrero Juan
Laboratorio de Compuestos de Coordinación y Química Supramolecular, Facultad de Química y Biología, Universidad de Santiago de Chile Av. Libertador Bernardo O'Higgins 3363, Estación Central, Casilla 40, Correo 33 Santiago Chile
Facultad de Ingenieria y Ciencias, Universidad Adolfo Ibáñez Av. Padre Hurtado 750 Viña del Mar Chile.
RSC Adv. 2023 Jan 3;13(2):825-838. doi: 10.1039/d2ra05341a.
A series of six new Cu(i) complexes with ([Cu(-{4-}pyridine-2-yl-methanimine)(PPh)Br]) formulation, where corresponds to a donor or acceptor -substituent, have been synthesized and were used to study self-association effects on their structural and electrochemical properties. X-ray diffraction results showed that in all complexes the packing is organized from a dimer generated by supramolecular π stacking and hydrogen bonding. H-NMR experiments at several concentrations showed that all complexes undergo a fast-self-association monomer-dimer equilibrium in solution, while changes in resonance frequency towards the high or low field in specific protons of the imine ligand allow establishing that dimers have similar structures to those found in the crystal. The thermodynamic parameters for this self-association process were calculated from dimerization constants determined by VT-H-NMR experiments for several concentrations at different temperatures. The values for (4.0 to 70.0 M range), Δ (-1.4 to -2.6 kcal mol range), Δ (-0.2 to 2.1 cal mol K range), and Δ (-0.8 to -2.0 kcal mol range) are of the same order and indicate that the self-dimerization process is enthalpically driven for all complexes. The electrochemical profile of the complexes shows two redox Cu(ii)/Cu(i) processes whose relative intensities are sensitive to concentration changes, indicating that both species are in chemical equilibrium, with the monomer and the dimer having different electrochemical characteristics. We associate this behaviour with the structural lability of the Cu(i) centre that allows the monomeric molecules to reorder conformationally to achieve a more adequate assembly in the non-covalent dimer. As expected, structural properties in the solid and in solution, as well as their electrochemical properties, are not correlated with the electronic parameters usually used to evaluate substituent effects. This confirms that the properties of the Cu(i) complexes are usually more influenced by steric effects than by the inductive effects of substituents of the ligands. In fact, the results obtained showed the importance of non-covalent intermolecular interactions in the structuring of the coordination geometry around the Cu centre and in the coordinative stability to avoid dissociative equilibria.
合成了一系列六种新的具有([Cu(-{4-}吡啶-2-基-甲亚胺)(PPh)Br])结构的Cu(i)配合物,其中 对应供体或受体 - 取代基,并用于研究自缔合对其结构和电化学性质的影响。X射线衍射结果表明,在所有配合物中,堆积是由超分子π堆积和氢键产生的二聚体组织而成。在几种浓度下进行的H-NMR实验表明,所有配合物在溶液中都经历快速的自缔合单体 - 二聚体平衡,而亚胺配体特定质子的共振频率向高场或低场的变化表明二聚体具有与晶体中发现的结构相似的结构。通过VT-H-NMR实验在不同温度下对几种浓度测定的二聚化常数计算了该自缔合过程的热力学参数。 (4.0至70.0 M范围)、Δ (-1.4至-2.6 kcal mol范围)、Δ (-0.2至2.1 cal mol K范围)和Δ (-0.8至-2.0 kcal mol范围)的值处于同一量级,表明所有配合物的自二聚化过程是由焓驱动的。配合物的电化学曲线显示两个氧化还原Cu(ii)/Cu(i)过程,其相对强度对浓度变化敏感,表明这两种物质处于化学平衡,单体和二聚体具有不同的电化学特性。我们将这种行为与Cu(i)中心的结构不稳定性联系起来,这种不稳定性允许单体分子进行构象重排,以在非共价二聚体中实现更合适的组装。正如预期的那样,固体和溶液中的结构性质以及它们的电化学性质与通常用于评估 取代基效应的电子参数无关。这证实了Cu(i)配合物通常受空间效应的影响比受配体取代基的诱导效应更大。事实上,所获得的结果表明了非共价分子间相互作用在Cu中心周围配位几何结构的构建以及避免解离平衡的配位稳定性中的重要性。