The localized orbital locator (LOL) and electron localization function (ELF) As the number of -CO groups in precursors decreases from n = 6 to 4 and then 2, the value of bifurcation of the LOL- out isosurfaces gradually increases, which means that the  out electron delocalization of the molecule enhances sequentially. However, the isosurfaces of LOL- in are truncated near the -CO groups, and the hindrance to the electron delocalization of the molecule with more -CO substituents is more severe. Therefore,  in MOs in C 18 -(CO) n (n = 6, 4, and 2) only exhibit a local rather than global delocalization, and C 18 -(CO) 2 shows a relatively more complete delocalization than its analogues. Similarly to that of  out systems, the electron delocalization of  in MOs on the short C-C bonds is also more pronounced than that on the long bonds. By comprehensively considering the electron delocalization characteristics of π out and π in MOs, we can infer that the overall electron delocalization of C 18 -(CO) n (n = 6, 4, and ) of isosurface except for the breakpoint near -CO groups.