Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15784 Athens, Greece.
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Ave., 11635 Athens, Greece.
Molecules. 2023 Apr 19;28(8):3565. doi: 10.3390/molecules28083565.
In the present paper, the photophysical properties of metallocene-4-amino-1,8-naphthalimide-piperazine molecules (), as well as their oxidized and protonated derivatives (, , and ), where M = Fe, Co, and Ni, were studied via DFT and TD-DFT, employing three functionals, i.e., PBE0, TPSSh, and wB97XD. The effect of the substitution of the transition metal M on their oxidation state, and/or the protonation of the molecules, was investigated. The present calculated systems have not been investigated before and, except for the data regarding their photophysical properties, the present study provides important information regarding the effect of geometry and of DFT methodology on absorption spectra. It was found that small differences in geometry, specifically in the geometry of N atoms, reflect significant differences in absorption spectra. The common differences in spectra due to the use of different functionals can be significantly increased when the functionals predict minima even with small geometry differences. For most of the calculated molecules, the main absorption peaks in visible and near-UV areas correspond mainly to charge transfer excitations. The Fe complexes present larger oxidation energies at 5.4 eV, whereas Co and Ni complexes have smaller ones, at about 3.5 eV. There are many intense UV absorption peaks with excitation energies similar to their oxidation energies, showing that the emission from these excited states can be antagonistic to their oxidation. Regarding the use of functionals, the inclusion of dispersion corrections does not affect the geometry, and consequently the absorption spectra, of the present calculated molecular systems. For certain applications, where there is a need for a redox molecular system including metallocene, the oxidation energies could be lowered significantly, to about 40%, with the replacement of the iron with cobalt or nickel. Finally, the present molecular system, using cobalt as the transition metal, has the potential to be used as a sensor.
本文采用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT），结合三个泛函（即 PBE0、TPSSh 和 wB97XD），研究了茂金属-4-氨基-1,8-萘酰亚胺-哌嗪分子（）及其氧化和质子化衍生物（、、和）的光物理性质。研究了取代过渡金属 M 对其氧化态以及分子质子化的影响。目前，尚未对本计算体系进行研究，除了光物理性质的数据外，本研究还提供了有关几何形状和 DFT 方法对吸收光谱影响的重要信息。研究发现，几何形状的微小差异，特别是 N 原子的几何形状，反映了吸收光谱的显著差异。由于使用不同的泛函，光谱中常见的差异可以大大增加，即使在几何形状差异较小的情况下，泛函也可以预测出最小值。对于大多数计算的分子，可见光和近紫外区域的主要吸收峰主要对应于电荷转移激发。Fe 配合物的氧化能较大，为 5.4 eV，而 Co 和 Ni 配合物的氧化能较小，约为 3.5 eV。有许多强的紫外吸收峰，激发能与它们的氧化能相似，表明这些激发态的发射可能与其氧化相反。关于泛函的使用，色散校正的包含不会影响本计算分子体系的几何形状，从而也不会影响其吸收光谱。对于某些需要包括茂金属的氧化还原分子体系的应用，用钴或镍取代铁可以显著降低氧化能，约为 40%。最后，本分子体系采用钴作为过渡金属，有可能用作传感器。
