Ligand-protected gold clusters attract much attention as building blocks for the functional materials at nanoscale. In order to deepen our understanding of clusters and find an application of their size-dependent properties, two problems should be overcome: (1) development of a scalable and reproducible synthesis method of desired gold clusters with atomic precision; (2) establishment of a simple guideline to control their electronic structures. In this account, our approach to tackle these problems is introduced. As for the former problem, we have developed an efficient synthesis method using an electronically activated cluster by hydride-doping. This atomically-precise cluster transformation reaction can be categorized into four types: core growth, ordered alloying, surface transformation, and fusion. For the latter one, we have utilized a simple jellium model to rationalize the relationship between electronic structures of clusters and structural factors such as composition and geometry. This simple principle enables us to intentionally design the physicochemical properties of clusters.

The interfacial chemical phenomenon plays an important role in modern chemistry and chemical engineering process. However, the detecting and microscopic understanding of the interfaces are still limited due to a lack of surface-specific techniques. Recent sum frequency generation (SFG) spectroscopy has been established as a powerful interface probe technique and provides valuable information at various interfaces, such as electrode/electrolyte and membranes. However, the observed SFG spectra are often hard to be interpreted and reliable theoretical support is strongly desirable. In this work, we have proposed a systematic method to generate non-empirical polarizable force fields and realized the simulation of SFG spectra of organic interfaces. The complicated SFG spectra are fully decomposed and the microscopic information of organic interfaces is extracted by the collaboration of SFG and molecular simulation. Furthermore, we discussed the effect of vibrational resonant components, such as quadrupole contribution and Fresnel factor dispersion, in the quantitative analysis of SFG spectra at organic interfaces. This work provides new aspects in the future study of complex organic interfaces through the SFG technique.

Molecular conductors demonstrate science of π electron systems where low-dimensionality and strong electron correlation play indispensable roles. Molecular conductors have been developed by collaboration between chemistry and physics. Chemistry prepares new materials that open new physics. On the other hand, deep insight of physics is fed back to new concepts of material design. This review describes cation radical salts of TTF (Tetrathiafulvalene) derivatives, DCNQI (N,N′-Dicyanobenzoquinonediimine)-Cu π-d systems, frustrated dimer-Mott systems, and single-component molecular Dirac electron systems from viewpoints of multi-dimensional and multi-orbital characters.