Corannulene monoanion

In this article, we report solution ESR spectra of coronene monoanion, to compare with that of corannulene monoanion. Moreover, we present ab initio molecular orbital (MO) calculation on the JT potentials of monoanionic state of corannulene and coronene, and consider the temperature dependence of the ESR spectra based on these results. Furthermore, the analytical JT potential surfaces of corannulene monoanion and coronene monoanion are derived using group theory. 

According to the epikernel principle, the symmetry of the stable minima of the corannulene ion is Cs. If corannulene monoanion is a static JT system, the 11 peaks of the hyperhne structure with intensity ratio 1 10 45 120 210 252 210 120 45 10 1 due to the 10 equivalent hydrogens can be split into 3s = 243 peaks. 

Table 1. Calculated HFC constants of corannulene monoanion taken from Ref. [11] and coronene monoanion and spin density calculated using MP2/6-31G(d,p)//lTF/6-31G(d,p)...

However, the ESR spectra for coronene monoanion did not exhibit such complicated peaks as corannulene monoanion. This suggests that AE in the coronene ion is smaller than that of the corannulene ion. In fact, the calculated energy barrier AE of one of the Dlh saddle points between the stable Clh structures is 0.2 meV, which is smaller than that of corannulene as mentioned previously. Therefore, the pseudorotation about the D6h JT crossing makes the HFC constant averaged and all the peripheral hydrogen atoms equivalent even at low temperatures. 

Figure 7 shows the JT surface on the Zs2( 16) mode of corannulene monoanion. Five equivalent minima and five equivalent saddle points can be seen on the surface, since the e2 configuration space has C5v/C = C5v symmetry. 

We also estimated the barrier height for corannulene monoanion on the E2( 16) mode. The calculated AE for corannulene is 7.9 meV. Since calculated potential barrier by HF method tends to be overestimated, this value agrees fairly well with the experimental value, 2.2 meV [11], In addition, the barrier could be much less, since this calculated value is an upper bound. 

Fig. 7. (a) Lower Jahn-Teller potential surface of corannulene monoanion on the E2( 0) mode. The energy barrier between the minima is 7.9 meV. (b) The vibrational vectors of the E2 16) mode, the symmetric one (top) and the asymmetric one (bottom). 

Fig. 10. (a) Lower potential surface of corannulene monoanion using equation (24), (b) cross-section along 0 = 0.0, and (c) cross-section along p = 0.06. 

Fig. 2. Frontier orbitals of corannulene (left) and coronene (right). Degenerate LUMOs can give rise to Jahn-Teller distortion in the monoanionic state.

In this section, we will derive the analytical JT potential for corannulene and coronene monoanion using group theory to elucidate roles of anharmonic vibration and nonlinear vibronic coupling. 

We observed solution ESR spectra of corannulene and coronene monoanion and performed ab initio calculation. We also applied group-theoretical calculation to the JT systems to explain the experimental and computational findings. The major findings are as follows ... 

Fig. 6. Electron-phonon coupling constants in the monoanions of coronene and corannulene.

Table 2. Calculated Tcs (K) for the monoanions of coronene and corannulene as a function of n(0) and /a ...

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