芳香性作为有机化学最重要的概念之一，一直以来吸引着理论与实验化学家的共同关注。根据环上贡献电子的类型，芳香性大体可分为sigma-芳香性和pi-芳香性，分别用来描述饱和和不饱和体系。相比而言，不饱和体系通常是pi-芳香性主导，sigma-芳香性占据主导作用的不饱和化合物极为少见。基于我们最近在sigma芳香性方面的发现，在本项目书拟应用量子化学方法对不饱和体系中sigma芳香性占据主导可能性进行系统地研究，对相关体系的结构和成键给出详细的分析。通过调配不同金属中心、不同配体、不同环系大小、体系不饱和程度，探索sigma-芳香性在不饱和体系中占据主导的本质及规律。然后通过合作的方式力争在实验上给予验证，为进一步扩展“sigma-芳香性” 概念作出力所能及的贡献。

Aromaticity, one of the most important concepts in organic chemistry, has attracted continuous attention from both experimental and theoretical chemists for many decades. In general, aromaticity can be clarified as π- and σ-aromaticity according to the type of electrons with major contributions. The traditional π-aromaticity generally describes the π-conjugation in fully unsaturated rings whereas σ-aromaticity may stabilize fully saturated rings with delocalization caused by σ-electron conjugation. The reported species with σ-aromaticity dominating in an unsaturated ring is very rare. This project will systematically investigate σ-aromaticity dominating in an unsaturated ring by quantum chemical calculations based on our recent findings on σ-aromaticity. By examining the possibility of different the transition metals, tuning the metal centers, ligands, ring size and degree of the saturation, we aim to dig out the rule governing σ-aromaticity dominant in an unsaturated ring. Finally, we hope to realize attractive examples of these novel species by collaboration with local experimental chemists.