Relative stabilities of the asymmetric OPOP, symmetric OPPO and cyclic conformations of P2O2

Various P₂O₂ planar isomers are investigated by molecular orbital calculations. Cyclic (¹A_g) is predicted to be more stable than OPOP (³A″-cis) and OPPO (¹A_g-trans) by 5.6 and 23.1 kcal/mol, respectively. The dimerization energy of 2PO→cyclic OPOP lies around 55 kcal/mol; the asymmetrical conformations OPOP and symmetrical OPPO are also bound. The computed vibrational frequencies and corresponding absorption intensities (derived at the SCF level) should help future experimental characterizations of these P₂O₂ isomers.