Role of Second Halogen Atoms of Dihalobenzene in Controlling the Photoluminescence Properties of Single-Walled Carbon Nanotubes by Reductive Arylation.

The chemical functionalization of single-walled carbon nanotubes (SWCNTs) is effective for controlling their near-infrared (NIR) photoluminescence (PL) wavelength by locally modulating the band gap energy of the SWCNTs. The PL efficiency is dependent on the degree of functionalization. Herein, SWCNTs were reductively arylated using sodium naphthalenide and halo- and dihalobenzene derivatives to control their PL properties. (6,5) SWCNTs functionalized with iodobenzene exhibited two new PL peaks at 1100 and 1230 nm. In contrast, the arylated SWCNTs prepared by using fluorobenzene and chlorobenzene exhibited a single new PL peak at 1100 nm. Furthermore, the arylated SWCNTs prepared using dihalobenzene derivatives except for 1,2-difluorobenzene exhibited a new PL peak at 1230 nm, which was dependent on the type and number of halogen atoms. The relative stabilities and transition energies of the model compounds for the arylated SWCNTs were estimated by using theoretical calculations. These results suggest that their transition energies can be tuned by the binding configuration and that the relative stability of the binding configuration varies depending on the addenda. The arylated SWCNTs were chirally separated, and an analysis of the optical properties of the separated SWCNT adducts revealed that this arylation reaction is effective for tuning the PL wavelength and intensity of (6,4), (7,3), (8,3), and (7,5) SWCNTs with different chiral indices in the NIR region. The addenda on the SWCNTs were successfully observed using transmittance electron microscopy by isolating the functionalized (6,5) SWCNTs and subsequent thermal treatment.