The hexanuclear rhenium cluster ions Re_6S_8X_6~(4-) (X = Cl, Br, I): Are these clusters luminescent?

摘要

Dirac molecular orbital calculations on the octahedral rhenium clusters Re_6S_8X_6~(4-) (where X = Cl, Br, I) are reported. The calculated relativistic molecular orbitals indicate that the manifold of closely spaced unoccupied energy levels are mainly localized on the octahedral rhenium core with some contributions from the #mu#_3-S ligands, while all the cluster highest occupied molecular orbitals are largely centered on the terminal halide ligands. All three hexanuclear rhenium cluster ions have singlet ground state (spanning the #GAMMA#_6~+ symmetry) and are therefore diamagnetic. They have the same ground state and excited state features as the intensely luminescent W_6Cl_(14)~(2-) cluster ion. The calculated charge distributions indicate that these clusters could be formulated as: Re_6~(-0.21)S_8~(-0.16)Cl_6~(-0.24), Re_6~(-0.23)S_8~(-0.17)Br_6~(-0.21) and Re_6~(-0.26)S_8~(-0.26)I_6~(-0.12), respectively.