Orellana Carlos, Miranda-Rojas Sebastián, Sundholm Dage, Mendizabal Fernando
Departmento de Química, Facultad de Ciencias, Universidad de Chile, P. O. Box 653, Las Palmeras 3425, Ñuñoa, Santiago, Chile.
Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Avenida República 275, Santiago, Chile.
Phys Chem Chem Phys. 2022 Oct 12;24(39):24457-24468. doi: 10.1039/d2cp02937e.
Electronic absorption and emission spectra of [M(MPA)] (M = Au, Ag; MPA = SCHCHCOOH) clusters have been recorded for energies below 5 eV at the time-dependent density functional theory (TDDFT) level using B3LYP and TPSSh functionals and compared to the calculated ones using the computationally inexpensive simplified TDDFT (sTDDFT) approach. The results show a qualitative agreement between the TDDFT and sTDDFT approaches used here, which were also in line with the experimental and theoretical spectra previously reported. However, the sTDDFT calculations were several orders of magnitude faster than those obtained by TDDFT. Our results support that sTDDFT provides an excellent balance between accuracy and low computational cost, becoming a suitable approach for studying the absorption and emission spectra of noble-metal clusters of sizes that would be unaffordable by the traditional TDDFT methods. The main peaks of the experimental absorption spectrum of [Au(MPA)] have been previously assigned, whereas [Ag(MPA)] has not been synthesised. However, its absorption spectrum resulted in having similar features to the experimental spectrum of [Ag(GSH)] (GSH = glutathione), used to validate our results. The emission spectra, which to date have not been reported either from experimental or theoretical means, were simulated by using the molecular structure of the first excited triplet state (T). The emission spectra were obtained by comparing them to those of [M(GSH)] since no experimental luminescence spectra have been reported for [M(MPA)]. The calculations suggest that [Ag(SR)] (SR = thiolate) clusters have a weak luminescence band in the NIR region. Finally, solvent shifts were found to be minor, whereas the absorption bands seem to be significantly redshifted in solid-state materials.
利用B3LYP和TPSSh泛函，在含时密度泛函理论（TDDFT）水平下记录了[M(MPA)]（M = Au、Ag；MPA = SCHCHCOOH）团簇在5 eV以下能量的电子吸收和发射光谱，并与使用计算成本较低的简化TDDFT（sTDDFT）方法计算得到的光谱进行了比较。结果表明，这里使用的TDDFT和sTDDFT方法在定性上是一致的，这也与先前报道的实验和理论光谱相符。然而，sTDDFT计算比TDDFT计算快几个数量级。我们的结果支持sTDDFT在准确性和低计算成本之间提供了出色的平衡，成为研究传统TDDFT方法无法承受的尺寸的贵金属团簇的吸收和发射光谱的合适方法。[Au(MPA)]的实验吸收光谱的主要峰已被先前指定，而[Ag(MPA)]尚未合成。然而，其吸收光谱的特征与用于验证我们结果的[Ag(GSH)]（GSH = 谷胱甘肽）的实验光谱相似。发射光谱，迄今为止尚未通过实验或理论手段报道，是通过使用第一激发三重态（T）的分子结构进行模拟的。通过将发射光谱与[M(GSH)]的发射光谱进行比较获得，因为尚未报道[M(MPA)]的实验发光光谱。计算表明，[Ag(SR)]（SR = 硫醇盐）团簇在近红外区域有一个弱发光带。最后，发现溶剂位移较小，而吸收带在固态材料中似乎有明显的红移。
