Ab initio exploration of low‐lying electronic states of linear and bent MNX+ (M = Ca, Sr, Ba, Ra; X = O, S, Se, Te, Po) and their origins

Abstract

AbstractHigh‐level multireference and coupled cluster quantum calculations were employed to analyze low‐lying electronic states of linear‐MNX+ and side‐bonded‐M[NX]+ (M = Ca, Sr, Ba, Ra; X = O, S, Se, Te, Po) species. Their full potential energy curves (PECs), dissociation energies (Des), geometric parameters, excitation energies (Tes), and harmonic vibrational frequencies (ωes) are reported. The first three chemically bound electronic states of MNX+ and M[NX]+ are 3Σ−, 1Δ, 1Σ+ and 3A″, 1A′, 1A″, respectively. The 3Σ−, 1Δ, 1Σ+ of MNX+ originate from the M+(2D) + NX(2Π) fragments, whereas the 3A″, 1A′, 1A″ states of M[NX]+ dissociate to M+(2S) + NX(2Π) as a result of avoided crossings. The MNX+ and M[NX]+ are real minima on the potential energy surface and their interconversions are possible. The M2+NX−/M2+[NX]− ionic structure is an accurate representation for their low‐lying electronic states. The Des of MNX+ species were found to depend on the dipole moment (μ) of the corresponding NX ligands and a linear relationship between these two parameters was observed.