The ionization energy and ΔHf (0 K) of CP, PCP and PCCP

By employing high-quality ab initio methods [RCCSD(T)/cc-pV5Z//UQCISD/6-311G(2d)], the adiabatic ionization energies of CP, PCP and PCCP are calculated, yielding values of 10.92±0.05, 8.78±0.05, and 9.43±0.05 eV. In addition, ΔHf (0 K) for CP, PCP and PCCP are derived, giving values of 124±2, 96±2 and 103±4 kcal mol−1, respectively. Some notable discrepancies with literature values are highlighted. The ground state of CP+ is confirmed to be the X3Π state arising from a ⋯π3σ1 configuration, with the ⋯π4σ0(1Σ+) state lying 0.75 eV higher in energy.