Cyclic and linear structures of C₁₃: a computational study

Recently, a linear structure of C₁₃ was observed and its infrared spectrum recorded. Computations of the linear and cyclic structures of C₁₃ are thus presented. The computations are performed at ab initio level using the standard 6-31G^* basis set. Electron correlation is treated by density functional theory (Becke3LYP) and perturbation treatment (MP2=FC). With the density-functional approach the standard 6-311G^* and 6-311G(2d,p) basis sets are applied, too. In all the treatments the cyclic structure (C_2v symmetry) is located about 90 kJ/mol below the linear form (D_∞h symmetry) while a tricyclic structure is considerably higher in energy (about 280 kJ/mol above the monocyclic species). Even at high temperatures the linear form represents less than 10% of the equilibrium isomeric mixture. Computed IR spectra are also reported. The stability evaluation corresponds to the findings of ion chromatography.