Quadripartite bond length rule applied to two prototypical aromatic and antiaromatic molecules.

Context: In 2000, a remarkably simple relationship was introduced, which connected the calculated geometries of isomolecular states of three different multiplicities. These encompass a ground single state, the first excited triplet state, as well as related radical anion and radical cation. The rule allows the prediction of the geometry of one of the species if the three remaining ones are known.

Structural Phase Transitions and Magnetic Superexchange in M Ag F Perovskites at High Pressure.

Pressure-induced phase transitions of M Ag F perovskites (M=K, Rb, Cs) have been predicted theoretically for the first time for pressures up to 100 GPa. The sequence of phase transitions for M=K and Rb consists of a transition from orthorhombic to monoclinic and back to orthorhombic, associated with progressive bending of infinite chains of corner-sharing [AgF ] octahedra and their mutual approach through secondary Ag⋅⋅⋅F contacts. In stark contrast, only a single phase transition (tetragonal→triclinic) is predicted for CsAgF ; this is associated with substantial deformation of the Jahn-Teller-distorted first coordination sphere of Ag and association of the infinite [AgF ] chains into a polymeric sublattice.

Pt as the limit of high oxidation states in oxide-nitride species.

A series of pentaatomic species has been investigated theoretically with relativistic DFT using the M06-L functional with both ZORA scalar relativistic correction, and including spin-orbit coupling effects. The distorted quasi-octahedral local minima for PtNO, PtNO and PtNO corresponding to decavalent Pt were found to be unstable with respect to the elimination of O, NO or N. However, barriers surrounding these minima suggest that these species could be achieved under low-temperature conditions, similar to what was predicted for PtO dications.

The high covalence of metal-ligand bonds as stability limiting factor: the case of Rh(IX)O and Rh(IX)NO.

Rhodium, a 4d transition metal and a lighter analogue of iridium, is known to exhibit its highest VIth oxidation state in RhF molecule. In this report, the stability and decomposition pathways of two species containing rhodium at a potentially formal +IX oxidation state, [RhO] and RhNO, have been investigated theoretically within the framework of the relativistic two-component Hamiltonian calculations. Possible rearrangement into isomers featuring lower formal oxidation numbers has been explored.