The ionization energy and Delta H-f (0 K) of CP, PCP and PCCP

By employing high-quality ab initio methods [RCCSD(T)/cc-pV5Z//UQCISD/6-311 G(2d)I, the adiabatic ionization energies of CP, PCP and PCCP are calculate d, yielding values of 10.92 +/- 0.05, 8.78 +/- 0.05, and 9.43 +/- 0.05 eV. In addition, DeltaH(f) (0 K) for CP, PCP and PCCP are derived, giving value s of 124 +/- 2, 96 +/- 2 and 103 +/- 4 kcal mol(-1), respectively. Some not able discrepancies with literature values are highlighted. The ground state of CP+ is confirmed to be the X(3)Pi state arising from a (...)pi (3)sigma (1) configuration, with the (...)pi (4)sigma (0)((1)Sigma (+)) state lying 0.75 eV higher in energy. (C) 2000 Elsevier Science B.V. All rights reserv ed.