Departamento de Química, Laboratório de Atividade Biológica e Química Supramolecular de Compostos de Coordenação (LABiQSC(2)), Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
Departamento de Química, Laboratório de Atividade Biológica e Química Supramolecular de Compostos de Coordenação (LABiQSC(2)), Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil; Departamento de Química, Grupo Computacional de Catálise e Espectroscopia (GCCE), Universidade Federal de São Carlos (UFSCar), Rod. Washington Luiz, km 235, CP 676, 13565-905 São Carlos, SP, Brazil.
Spectrochim Acta A Mol Biomol Spectrosc. 2023 May 5;292:122420. doi: 10.1016/j.saa.2023.122420. Epub 2023 Feb 1.
Due to the scarcity of spectroscopic studies on metal-coordinated naphthalimides, and aiming to investigate fundamental spectroscopic aspects, we have described here the aggregates of N-(4-pyridyl)-1,8-naphthalimide (NI-py) in solution as well as solvatochromism displayed by it and by the coordination compounds [RuO(CHCOO)(NI-py)], n = +1 or 0. Based both on theoretical calculations and luminescence spectra, we demonstrated that in aqueous media, the NI-py π-stacking is thermodynamically favored, suggesting a preferable conformation where the pyridine and naphthalene moieties of two NI-py molecules are parallel to each other, but are not co-planar within an individual molecule, due to steric hindrance. The NI-py ππ* band displayed positive solvatochromism, to which the major contribution was the Catalan's SP parameter (solvent polarizability). This observation is fully consistent with the extended π-electron cloud of the NI-py naphthalene ring. However, a secondary contribution of the SA (solvent acidity) was also observed, owing to the electron pairs available at the N-heteroatom of the pyridine rings and at the carbonyl-group oxygen atoms. Finally, the multiparametric solvent effect analysis indicated that the electronic coupling between coordinated NI-py and the metallic core is modulated by the charge of the [RuO(CHCOO)] core, being higher for the reduced species [RuO(CHCOO)(NI-py)]. In addition, in this reduced species, there is no overlap between NI-py ππ* and the [RuO(CHCOO)] charge transfer (CT) transitions, leading to the observation of the dependence of the CT energy with the SdP parameter (solvent dipolarity) since the CT transition implies in a charge-separation state.
由于对金属配位萘酰亚胺的光谱研究稀缺，并且旨在研究基本的光谱方面，我们在这里描述了 N-(4-吡啶基)-1,8-萘酰亚胺（NI-py）在溶液中的聚集以及它和配位化合物[RuO(CHCOO)(NI-py)]，n = +1 或 0 的溶剂变色性。基于理论计算和荧光光谱，我们证明在水介质中，NI-py 的π-堆积在热力学上是有利的，表明了一种更可取的构象，其中两个 NI-py 分子的吡啶和萘部分彼此平行，但在单个分子内并不共面，这是由于空间位阻。NI-py 的 ππ带显示出正的溶剂变色性，主要贡献是 Catalan 的 SP 参数（溶剂极化率）。这一观察结果与 NI-py 萘环扩展的π-电子云完全一致。然而，也观察到了次要的 SA（溶剂酸度）贡献，这是由于吡啶环的 N 杂原子和羰基氧原子上的电子对。最后，多参数溶剂效应分析表明，配位的 NI-py 和金属核心之间的电子耦合受到[RuO(CHCOO)]核心电荷的调节，对于还原物种[RuO(CHCOO)(NI-py)]更高。此外，在这种还原物种中，NI-py ππ和[RuO(CHCOO)]电荷转移（CT）跃迁之间没有重叠，导致观察到 CT 能量与 SdP 参数（溶剂偶极矩）的依赖性，因为 CT 跃迁意味着电荷分离状态。
