Cyclobutadiene complexed with Li atom and the effects of substituting by F atom in LiC4H4

The complex in LiC4H4−nFn (n=1-4) has low symmetry (Cs or C1) due to F substituent(s). The LiC4H4−nFn complexes with F(2) substituent exhibit different structural characteristics from those without F(2) substituent. Thus the 11 F-substituted complexes plus LiC4H4 are clearly divided into A (without F(2)) and B (with F(2)) two groups. The electron correlation contributions are obviously different between the complexes in group A and those in group B for interaction energies and vertical ionization energies (VIE).