Boron-doped nanographene: Lewis acidity, redox properties, and battery electrode performance† †Electronic supplementary information (ESI) available: Supporting movie, experimental procedure and characterization details. CCDC 1059942–1059945. For ESI and crystallographic data in CIF or other electron

The impact of boron doping on the nature of nanographene was investigated at the molecular level in terms of chemical adsorption with various Lewis bases, spin multiplicity of the two electron-reduced species, and performance as a battery electrode.


Photophysical properties of 1c
UV-visible absorption spectra were recorded on a Shimadzu UV-3510 spectrometer. Vis-NIR fluorescence spectra were recorded on a Fluorolog-3 spectrometer (HORIBA Jobin Yvon).

Spectral titrations of 1a with various Lewis bases
UV-visible absorption spectra were recorded on a Shimadzu UV-3510 spectrometer.
Fluorescence spectra were recorded on a Hitachi F-4500 spectrometer. The absolute fluorescence quantum yields were determined with a Hamamatsu C9920-02 calibrated integrating sphere. NH 3 gas was prepared by heating a 28% NH 3 aqueous solution.       Figure S7a). where b is a constant while ε 1 and ε 2 are defined as ε(1a⋅LB)-ε(1a) and ε(1a⋅LB 2 )-ε(1a), respectively. Nonlinear least-square fitting was performed using a spectral analysis program      S14 absorption spectrum, which showed absorption maxima around 600, 780, 890 nm, was consistent with that obtained by electrochemical reduction.

Cyclic voltammetry of 1c
Cyclic voltammetry (CV) was performed on an Als/chi-617A electrochemical analyzer. The CV cell consisted of a glassy carbon working electrode, a Pt wire counter electrode, and a Ag/AgNO 3 reference electrode. The measurements were carried out under an argon atmosphere at a scan rate of 50 mV/s with nBu 4 NPF 6 as a supporting electrolyte (0.1 M). The redox potentials were calibrated with ferrocene as an internal standard.

Evaluation of battery electrode performance
The charge/discharge tests were performed with a Hokuto HJ1001-SM8A charge/discharge device. Specific capacity is determined based on the weight of active materials. The theoretical capacity C was calculated from the following equation: S5 where N A ⋅e is the Faraday constant (96487 C mol -1 ), and M w is the molecular weight required to store one electron.      Hydrogen atoms were omitted for clarity. Structures of 1bʹ′ and its Lewis adducts with DMAP, 1bʹ′⋅DMAP and 1bʹ′⋅(DMAP) 2 , were optimized and then TD-DFT calculations were performed at the B3LYP/6-31G* level of theory.
The mono Lewis adduct 1bʹ′⋅DMAP has a donor-acceptor type electronic structure, in which the HOMO is delocalized around the tetra-coordinate boron moiety while the LUMO around the tri-coordinate boron unit. Therefore, the S 0 →S 1 transition energy of 1bʹ′⋅DMAP is smaller than those of 1bʹ′ and 1bʹ′⋅(DMAP) 2 .

S24
Structural optimization of 1bʹ′ 2-. Structural optimizations of 1bʹ′ 2were performed using Gaussian 09 program S7 at the (U)B3LYP/6-311+G** level of theory. The symmetry-broken approach was applied for open-shell singlet calculations. Singlet biradical character (y) was calculated by the natural orbital occupancy number (NOON) of the LUMO in the broken-symmetry UHF/6-311+G** calculation S8 using the Yamaguchi scheme S9 .