Theoretical Study of Charge Mobility Properties of Complexes Si(DPP)(CH3)2 and Si(Bzimpy)(CH3)2

Abstract

The direction of organic electronics research is attracting more and more interest from the scientific community. One of the indicators of such interest is the appearance of commercially available products with screens based on organic compounds. Therefore, conducting experimental and theoretical research in this area is an urgent task. Pentacoordination neutral complexes of silicon are poorly studied from the point of view of application in organic electronics, as well as six-coordination analogues. We present data on the calculation of reorganization energies, intermolecular transfer integrals, transfer rates and charge mobility for the optimized structures of pentacoordinated silicon complexes Si(DPP)(CH3)2 and Si(bzimpy)(CH3)2. We have applied Marcus-Hush model for calculation of charge mobilities. The Si(DPP)(CH3)2 structure contains one diphenylpyridine (DPP = 2,6-diphenylperidine) ligand. The Si(bzimpy)(CH3)2 structure contains one benzimidazole (bzimpy = 2,6-bis(benzimidazole-2'-il)pyridine) ligand. Computational data were obtained using the B3LYP hybrid functional and the basis set 6-31G*. All calculations were performed using Gaussian09 program package. The charge mobility data obtained for Si(DPP)(CH3)2 and Si(bzimpy)(CH3)2 pentacoordinated silicon complexes were compared with their six-coordinate counterparts Si(DPP)2 and Si(bzimpy)2 for which experimental data on charge mobilities become available last years. Comparison with six-coordination analogues of complexes showed that penta-coordination complexes Si(DPP)(CH3)2 and Si(bzimpy)(CH3)2 have much higher mobility of electrons, while Si(bzimpy)(CH3)2 also has higher hole mobility. We suppose this could be related to different symmetry of the pentacoordinated and hexacoordinted complexes. It is shown that the mobility of holes is much higher in the complex Si(bzimpy)(CH3)2 than in Si(DPP)(CH3)2.