Martínez-Fernández Lara, Improta Roberto
Departamento de Química Física de Materiales, Instituto de Química Física Blas Cabrera, CSIC (Consejo Superior de Investigaciones Científicas), 28006 Madrid, Spain.
Istituto di Biostrutture e Bioimmagini-CNR (IBB-CNR), Via De Amicis 95, I-80145 Napoli, Italy.
Molecules. 2025 Jan 13;30(2):298. doi: 10.3390/molecules30020298.
We perform DFT calculations with different hybrid (ωB97X-D and M05-2X) and double hybrid (B2PLYP-D3 and ωB2PLYP) functionals to characterize the lowest energy triplet excited states of naphthalene monomer and dimers in different stacking arrangements and to simulate their absorption spectra. We show that both excimer and localized triplet minima exist. In the former, the spin density is delocalized over the two monomers, adopting a face-to-face arrangement with a short inter-molecular distance. In the latter, the spin density is localized on a single naphthalene molecule, and different minima or pseudo-minima are possible, the most stable one corresponding to a slipped parallel arrangement. According to B2PLYP-D3 calculations, excimer minima are the most stable, in line with the indications of ADC(2) studies. However, the relative stability of the minima is reverted when including thermal and vibrational effects. Excimer minima exhibit a very intense absorption spectrum, peaking above 500 nm. The computed absorption spectra of localized minima significantly depend on the stacking geometry and do not coincide with that of isolated naphthalene. Hybrid functionals provide very accurate vibronic absorption spectra for naphthalene monomer, both in the singlet and in the triplet state, but underestimate the stability of the excimer triplet.
我们使用不同的杂化泛函（ωB97X-D和M05-2X）以及双杂化泛函（B2PLYP-D3和ωB2PLYP）进行密度泛函理论（DFT）计算，以表征萘单体和不同堆积排列的二聚体的最低能量三重激发态，并模拟它们的吸收光谱。我们发现准分子和局域三重态极小值均存在。在前者中，自旋密度在两个单体上离域，采取面对面排列且分子间距离较短。在后者中，自旋密度局域在单个萘分子上，可能存在不同的极小值或准极小值，最稳定的一种对应于错位平行排列。根据B2PLYP-D3计算，准分子极小值是最稳定的，这与含时耦合簇理论二阶微扰（ADC(2)）研究的结果一致。然而，当考虑热效应和振动效应时，极小值的相对稳定性会发生反转。准分子极小值表现出非常强烈的吸收光谱，峰值在500 nm以上。局域极小值的计算吸收光谱显著依赖于堆积几何结构，且与孤立萘的吸收光谱不一致。杂化泛函为萘单体在单重态和三重态下都提供了非常精确的振转吸收光谱，但低估了准分子三重态的稳定性。
