Computational study on optical and electronic properties of the “CH”/N substituted emitting materials based on spirosilabifluorene derivatives

In order to predict the substitution effect, equilibrium ground state geometry configurations and the relevant electronic properties of a series “CH”/N substituted symmetric and asymmetric spirosilabifluorene derivatives are optimized by the HF(B3LYP)/6-31G(d) method. Their excited state geometries are investigated using the CIS/6-31G(d) method. The absorption and emission spectra are evaluated at the TD-PBE0/6-31+G(d) level. Compared to the parent compound, the skeleton structure does not show any appreciable change. The “CH”/N substitution decreases both the EHOMO and ELUMO in S0, and a very slight change is observed on Eg values. Thus no apparent change is predicted for the absorption/emission wavelength either. However, an efficient charge transfer is revealed within the “CH”/N substituted derivatives upon excitation. The properties may make these derivatives efficient electroluminescence materials. A series of low reorganization energy values are also obtained based on these derivatives, implying a potential application as charge-transport materials. Furthermore, we find that the performance and the optical properties of these derivatives can be improved by adding aryl groups and oligomerization.