Charge transfer composites of bis(cyclopentadienyl) and bis(benzene) transition metal complexes encapsulated in single-walled carbon nanotubes

Abstract

The interaction of two organometallic $\ensuremath{\pi}$-aryl $(M{L}_{2})$ complexes, cobaltocene $[\mathrm{Co}{({\ensuremath{\eta}}^{5}\text{\ensuremath{-}}{\mathrm{C}}_{5}{\mathrm{H}}_{5})}_{2}]$ and bis(benzene) chromium $[\mathrm{Cr}{({\ensuremath{\eta}}^{6}\text{\ensuremath{-}}{\mathrm{C}}_{6}{\mathrm{H}}_{6})}_{2}]$, with a series of semiconducting $(n,0)$ $(n=11--18)$ single-walled carbon nanotubes (SWNT) has been investigated using density-functional theory calculations. Dependence of the $M{L}_{2}$-SWNT interaction on the diameter and band structure of the nanotube was studied. We find that both cobaltocene and bis(benzene) chromium act as electron donors to form composites ${[M{L}_{2}]}^{q+}{[\mathrm{SWNT}]}^{q\ensuremath{-}}$ in which the extent of the charge transfer, and hence the binding energy, is modulated by the diameter and band structure of the nanotube. The relative influence of the ionization energy of the $M{L}_{2}$ complexes and the electron attachment energy of the SWNT on the binding energy for these composites is described.