The nature of the ground state and the lowest triplet excited state of the [Rh-2(1,3-diisocyanopropane)(4)](2+) ion have been investigated by the density functional theory. Two locally stable geometrical conformations are found on the potential energy surfaces of both the ground and excited states, corresponding to the eclipsed and twisted conformations, the eclipsed conformation being more stable and having the shorter Rh-Rh bond length. While the Rh-Rh distances of the two conformations differ by similar to0.4 Angstrom, they shorten to the same value upon excitation (similar to3.1 Angstrom). The excited state originates from the d(z2)(*) (metal antibonding) to p(z) (ligand-metal bonding) electronic transition. The Mayer Rh-Rh bond order increases from similar to0.2 to more than 0.8 upon excitation, while the Rh-C-N bond order shows a slight decrease, A topological bond path between the Rh atoms is found in both the ground and excited states, while the electron localization function (ELF) indicates weak Rh-Rh covalent bonding for the excited state only.