ChemInform Abstract: Similarities and Differences Between (C₆₀)₂^2‐ and (C₅₉N)₂ Conformers.

Abstract

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Implications of Nitrogen Doping on Geometrical and Electronic Structure of the Fullerene Dimers

“…(C 60 – ) 2 and (C 59 N) 2 have the same electronic number and similar structures (Figures 1a, 1b). According to the previous theoretical predictions, [ 36 ] the most stable conformer for (C 60 – ) 2 dimer is an anti‐conformer with C 2h symmetry, which has been confirmed in the crystallographic structures [ 9 ] as shown in Figure 1b, but the length of the inter‐ cage C—C bond (1.597 Å) slightly deviates from the predicted one (1.618 Å). [ 36 ] Notably, the length of the inter‐cage C—C bond (1.597 Å) is longer than that of a normal C(sp 3 )‐C(sp 3 ) single bond, and the difference of the inter‐cage C—C bond lengths between (C 59 N) 2 and (C 60 – ) 2 may explain why (C 60 – ) 2 depolymerizes above 220 K, [ 9 ] while (C 59 N) 2 depolymerizes above 500 K. [ 36 ]…”

“…As shown in Table 2, our optimized structures by a B3LYP‐ D3BJ method are more consistent with the single crystal structures than that by a commonly used B3LYP method, [ 36 ] suggesting that the B3LYP‐D3BJ function is more suitable for the systems of fullerene dimers. With regard to distances, R C‐C of (C 59 N) 2 is shorter than that of (C 60 ) 2 , [P(O)(OMe) 2 C 60 ] 2 and the three (C 60 – ) 2 dimers, while the D inter‐cage of (C 60 ) 2 is the shortest, probably due to two inter‐cage C—C single bonds in (C 60 ) 2 (whereas only one inter‐cage C—C single bond in the other dimers).…”

“…Herein, we elucidate the key crystal structure information of (C 59 N) 2 , and confirm that the inter‐cage C—C single bond length of (C 59 N) 2 is approximately equal to that of an ordinary C(sp 3 )‐C(sp 3 ) single bond, and that the most stable conformer of (C 59 N) 2 is gauche‐conformer with C 2 symmetry. By comparing the key crystal structure information of (C 59 N) 2 with those in the previous theoretical calculations, [ 34‐36 ] we find most of the theoretical structures deviate from single crystal structures of the fullerene dimers. Therefore, a more accurate calculation is necessary to be developed for better understanding the fullerene dimers, especially for those that fail to grow single crystals.…”

“…[ 36 ] theoretically predicted the most stable conformers of (C 59 N) 2 and (C 60 – ) 2 . Although there are many theoretical studies, [ 34‐36 ] the structure and conformer of (C 59 N) 2 remained ambiguous. In recent years, we have improved the overall yield of (C 59 N) 2 by optimizing Wudl's synthesis route.…”

“…As a result, we discovered that DFT calculations using the B3LYP method and 6‐31G(d,p) basis set combined with an extra dispersion correction (D3BJ) approach [ 39 ] are much more accurate than those previous calculation methods. [ 34‐36 ]…”