Tetrahedral silicon-based luminescent molecules: Synthesis and comparison of thermal and photophysical properties by various effect factors

Abstract

A series of luminescent molecules were presented employing the tetrahedral structural motif of the silicon atom, which further connected different N-containing heterocycle functional groups in their periphery using phenyl rings as the bridges. These compounds included three kinds of N-heterocycle functional silanes: imidazole derivatives (1a–h), pyrazole derivatives (2a–e) and benzimidazole derivatives (3a–b), and their structures were fully characterized by FT-IR, 1H NMR, 13C NMR and HRMS. The TGA results indicate that they all exhibit high thermal stabilities. The photophysical properties demonstrate that they are fluorescent in the violet-blue region and could be potentially applied as blue emitters for organic light-emitting diodes (OLEDs). The effect factors of sort, disposition and number of substituent groups and N-containing heterocycle functional groups on their thermal and photophysical properties were investigated. Molecular calculations were also performed to support the experimental results. Moreover, the computational results reveal that these compounds all exhibit relatively large HOMO–LUMO band gaps with the range from 4.82 eV (2d) to 5.19 eV (1a and 2c), making them become promising candidates as host materials for emitters and hole/electron blocking materials in OLEDs display.