A computational characterization of N2@C60

Recent observations of N2@C60 are supported computationally. The geometry is optimized at the B3LYP/3-21G and PW91/3-21G levels. The lowest-energy structure has the N2 unit oriented towards a pair of parallel pentagons so that the complex exhibits D5d symmetry. Single-point energy calculations are further carried out at the B3LYP/6-31G*, PW91/6-31G* and MP2 = FC/6-31G* levels and corrected for the basis set superposition error (BSSE). The MP2 = FC/6-31G* treatment with the BSSE correction gives a stabilization energy of -9.3 kcal mol−1, whereas DFT approaches mostly fail to produce a stabilization. The entropy term for the encapsulation is also evaluated and leads to a standard Gibbs energy change upon encapsulation at room temperature of -3.3 kcal mol−1. The computed structural and vibrational characteristics are also reported. §Dedicated to Professor Nicholas C. Handy.