Crystal Structure and Optical Properties of the [Ag₆₂S₁₂(SBu^t)₃₂]²⁺ Nanocluster with a Complete Face-Centered Cubic Kernel

The crystal structure of the [Ag62S12(SBut)32]2+ nanocluster (denoted as NC-I) has been successfully determined, and it shows a complete face-centered-cubic (FCC) Ag14 core structure with a Ag48(SBut)32 shell configuration interconnected by 12 sulfide ions, which is similar to the [Ag62S13(SBut)32]4+ structure (denoted as NC-II for short) reported by Wang. Interestingly, NC-I exhibits prominent differences in the optical properties in comparison with the case of the NC-II nanocluster. We employed femtosecond transient absorption spectroscopy to further identify the differences between the two nanoclusters. The results show that the quenching of photoluminescence in NC-I in comparison to that of NC-II is caused by the free valence electrons, which dramatically change the ligand to metal charge transfer (LMCT, S 3p → Ag 5s). To get further insight into these, we carried out time-dependent density functional theory (TDDFT) calculations on the electronic structure and optical absorption spectra of NC-I and NC-II. These findings offer a new insight into the structure and property evolution of silver cluster materials.[Ag62S12(SBut)32]2+纳米团簇（命名为NC-I）的晶体结构已成功解析，其具有完整的面心立方（face-centered-cubic，FCC）Ag14核结构，以及由12个硫离子桥联的Ag48(SBut)32壳层构型，该结构与Wang课题组报道的[Ag62S13(SBut)32]4+结构（简称NC-II）高度相似。值得注意的是，NC-I与NC-II纳米团簇在光学性质上存在显著差异。我们采用飞秒瞬态吸收光谱进一步表征了这两种纳米团簇间的性能差异。结果表明，相较于NC-II，NC-I的光致发光猝灭源于自由价电子，该自由价电子显著改变了配体到金属电荷转移（ligand to metal charge transfer，LMCT，S 3p → Ag 5s）过程。为深入探究该现象的内在机制，我们对NC-I和NC-II的电子结构及光学吸收光谱开展了含时密度泛函理论（time-dependent density functional theory，TDDFT）计算。上述研究结果为银团簇材料的结构与性能演化规律提供了全新的认知视角。