The Inductive Effect in Nitridosilicates and Oxysilicates and Its Effects on 5d Energy Levels of Ce³

The inductive effect exists widely in inorganic compounds and accounts well for many physicochemical properties. However, until now this effect has not been characterized quantitatively. In this work, we collected and analyzed the structural data of more than 100 nitridosilicates and oxysilicates, whose structures typically consist of [SiN₄] or [SiO₄] tetrahedra. We introduce a new parameter, the inductive effect factor μΔχ, related to the difference of electronegativity between constituent metal elements and silicon. Then, a linear relationship is established between average length of Si-N/Si-O bonds and the inductive factor with the help of statistical method, that is, l̅ = 1.7313 + 0.0166 μΔχ (Å) with adjusted (adj) R² = 0.800 for Si-N and l̅ = 1.6221 + 0.0035 μΔχ(Å) with adj R² = 0.240 for Si-O. Furthermore, our research shows that the distinct positive correlation does exist between the inductive factor and the centroid shift of 5d levels of Ce³⁺. This work will help us understanding the inductive effect deeply and quantitatively.