New Y-shaped structures of tetra-gold cation clusters stabilised by absorption of oxygen molecules

Theoretically calculated research studies of oxygen absorption on gold cluster surface were used to simulate chemical reactions on the surfaces of gold nanoparticles. Low-energy conformational structures of tetra-nuclear gold cluster complexes with multiple oxygen molecule ligands, Au₄(O₂)<i>_n</i>⁺ (<i>n</i> = 1∼4), were theoretically investigated by the DFT calculations with long-range-corrected hybridisation functional CAM-B3LYP. In addition to known low-energy structures with tetragonal four-gold core, new low-energy isomers with Y-shaped four-gold core were revealed to be stable. The rationality of new structures was confirmed by the agreement of calculated infrared vibrational spectra with experimental results. The findings of new structures successfully interpreted the features of the vibrational spectra of this series of clusters. <b>Highlights:</b>New low-energy complex structures, containing a Y-shaped four-gold core, are stabilised by absorption of oxygen molecules and possess large first dissociation energy of oxygen molecule.The O–O stretching fundamental frequency of the Au–O–O–Au tetragon in the complexes with the Y-shaped four-gold core is found to be the origin of experimental vibrational absorption at about 1250 cm⁻¹.Sum frequency of the stretching vibrations of the Au–O bond and the O–O bond is responsible for absorption observed at 1470 cm⁻¹.A new activation mode of oxygen molecule is found in the Au–O–O–Au tetragon of new Y-core complexes, where the O-O bond length is <i>ca.</i> 1.30 angstrom (normally, <i>ca.</i> 1.20 angstrom). New low-energy complex structures, containing a Y-shaped four-gold core, are stabilised by absorption of oxygen molecules and possess large first dissociation energy of oxygen molecule. The O–O stretching fundamental frequency of the Au–O–O–Au tetragon in the complexes with the Y-shaped four-gold core is found to be the origin of experimental vibrational absorption at about 1250 cm⁻¹. Sum frequency of the stretching vibrations of the Au–O bond and the O–O bond is responsible for absorption observed at 1470 cm⁻¹. A new activation mode of oxygen molecule is found in the Au–O–O–Au tetragon of new Y-core complexes, where the O-O bond length is <i>ca.</i> 1.30 angstrom (normally, <i>ca.</i> 1.20 angstrom).

本研究以金团簇表面氧吸附的理论计算结果为基础，模拟金纳米颗粒表面的化学反应过程。本研究采用结合长程校正杂化泛函CAM-B3LYP的密度泛函理论（Density Functional Theory, DFT）计算，对带有多氧分子配体的四核金团簇配合物Au₄(O₂)ₙ⁺（n=1~4）的低能构象结构开展了理论研究。除已报道的以四方四金核为核心的低能结构外，本研究还发现了以Y形四金核为核心的新型低能异构体，并证实其具有热力学稳定性。通过将理论计算得到的红外振动光谱与实验结果进行比对，验证了该新型结构的合理性。本研究成果成功诠释了该系列金团簇的振动光谱特征。

**研究亮点：**
1. 以Y形四金核为核心的新型低能配合物结构可通过氧分子吸附实现稳定存在，且具备较高的氧分子一级解离能。
2. 在含Y形四金核的配合物中，Au-O-O-Au四方结构的O-O伸缩基频，被证实为实验中约1250 cm⁻¹处振动吸收峰的来源。
3. Au-O键与O-O键的伸缩振动和频，对应实验中1470 cm⁻¹处观测到的吸收峰。
4. 在新型Y形核配合物的Au-O-O-Au四方结构中，发现了一种全新的氧分子活化模式：其O-O键长约为1.30埃（常规O-O键长约为1.20埃）。

以Y形四金核为核心的新型低能配合物结构可通过氧分子吸附实现稳定存在，且具备较高的氧分子一级解离能。在含Y形四金核的配合物中，Au-O-O-Au四方结构的O-O伸缩基频，被证实为实验中约1250 cm⁻¹处振动吸收峰的来源。Au-O键与O-O键的伸缩振动和频，对应实验中1470 cm⁻¹处观测到的吸收峰。在新型Y形核配合物的Au-O-O-Au四方结构中，发现了一种全新的氧分子活化模式：其O-O键长约为1.30埃（常规O-O键长约为1.20埃）。