Bonding and metastability for Group 12 dications

Electronic structure and bonding properties of the Group 12 dications M-2(2+)(M = Zn, Cd, Hg) are investigated and electron density-derived quantities are used to characterize the metastability of these species. Of particular interest are the complementary descriptions afforded by the Laplacian of the electron density backward difference (2)rho(r)and the one-electron Bohm quantum potential (Q= del 2 rho root p(r)/2 root p(r)) along the bond path. Further, properties derived from the pair density including the localization-delocalization matrices (LDMs) and the interacting quantum atoms (IQA) energies are analyzed within the framework of the quantum theory of atoms in molecules (QTAIM). From the crossing points of the singlet (ground) and triplet (excited) potential energy curves, the barriers for dissociation (BFD) are estimated to be 25.2 kcal/mol (1.09 eV) for Zn-2(2+), 22.8 kcal/mol (0.99 eV) for Cd-2(2+), and 26.4 kcal/mol (1.14 eV) for Hg-2(2+). For comparison and benchmarking purposes, the case of N(2)(2+)is considered as a texbook example of metastability. At the equilibrium geometries, LDMs, which are used here as an electronic fingerprinting tool, discriminate and group together Group 12 M(2)(2+)from its isoelectronic Group 11 M-2. While classical bonding indices are inconclusive in establishing regions of metastability in the bonding, it is shown that the one-electron Bohm quantum potential is promising in this regard.

Automated summary

The electronic structure and bonding properties of Group 12 dications M-2(2+)(M = Zn, Cd, Hg) were investigated, with emphasis on using electron density-derived quantities to characterize the metastability of these species. Various methods including Laplacian of the electron density and one-electron Bohm quantum potential were used to describe the bond path. The findings suggest promising results in discerning the stability of these species using electronic fingerprinting tools like LDMs and IQA energies, despite classical bonding indices being inconclusive.