Study on the interaction of metallocene catalysts with the surface of carbon nanotubes and its influence on the catalytic properties. 1. Investigation of possible complex structures and the influence on structural and electronic properties

Abstract

The interaction of a single-walled carbon nanotube (SWCNT) with the Cp2Zr+-CH3 has been studied with a hybrid quantum mechanics/molecular mechanics (QM/MM) method and density functional theory. At the first step, the QM/MM method has been validated by comparing its results with those of a related full QM approach. In this step, we used benzene, isobutane, and carboxyl species to model π⋯π, CH⋯π, and covalent interactions, respectively. According to our results, the QM/MM method is accurate enough to investigate covalent and noncovalent interactions with the surface of CNTs. After validating the method, the possible complex, i.e. Metallocene-CNT, structures have been investigated. We considered different π⋯π and CH⋯π configurations and found that: The Cp2Zr+-CH3 can be attached to SWCNT via both π⋯π and C-H⋯π noncovalent interactions. The C-H⋯π configurations are more stable than the π⋯π analogues and those with the zirconium atom near the CNT surface are the most stable ones. We also examined the influence of the CNT on the electronic and steric properties of the metallocene. While the tube has a small effect on the electronic properties of the catalyst, it has a considerable impact on its steric environment, which may lead to the high molecular weight and tacticity products.