ab initio study of structure and energy of Be2+⋅(CO)1−3 complexes

Geometries and binding energies of Be²⁺ ⋅ (CO)_1–3 complexes have been determined at the level of MP2/aug-cc-pVTZ method. Binding energy increases linearly with the number of CO molecules in these complexes. Our results show that the sequential bond dissociation energy follows the order: \({\text{Be}}^{2+}\cdot \text{CO}\) \(>\) \({\text{Be}}^{2+}\cdot {\left(\text{CO}\right)}_{2}\) \(>{\text{Be}}^{2+}\cdot {\left(\text{CO}\right)}_{3}\). This trend was well-explained in terms of ion–quadrupole interaction fluctuations. Detailed bond analysis confirmed that the strength of interaction between Be ion and CO molecule decreases with the number of CO molecules in these complexes. Our calculations show that the strength of interaction with these complexes is highly dependent on the CO bond polarization and stabilization energy of these complexes.

Graphical abstract

The sequential bond energies of the Be²⁺ ·(CO)^1,2,3 complexes follow the trend: Be²⁺ ·(CO) > Be²⁺ ·(CO)₂ > Be²⁺ ·(CO)₃ . The primary cause of the variations observed in the ion-quadruple attraction forces in these complexes is the strength of the σ-donation between the Be cation and CO molecules. The ion-induced dipole interaction energy in these complexes is insignificant.