Theoretical studies of the structure and properties of cyclic hydrogen peroxide clusters: quantum chemical calculations

Density functional theory calculations of the structure and properties of bicyclic and tricyclic hydrogen peroxide (HP) clusters (Pn, n = 8–14) in the gas phase were carried out for the first time. Three main types of couplings of two or more ring clusters P4–P7 (tetra-, penta-, hexa-, and heptamer) into a cyclic structure were investigated. The first (type A) includes a reorientation of hydrogen bonds within the cluster and a change in the sign of the dihedral angle (chirality) of several HP molecules, while the second (type B) process entails the formation of bridges comprising two HP molecules, without altering the overall chirality of the cluster. The third type of coupling of two clusters involves the formation of nested structures in which the smaller cluster is located inside the larger one. The thermodynamic parameters of conjugation of clusters P4–P7 with the formation of cyclic structures were calculated. In the gas phase, the heterochiral type A structures have a lower energy than the homochiral type B structures with the same number of HP molecules. In the case of low-energy cyclic clusters, the highest number of hydrogen bonds (2n) is favourable.