A new interpretation of the bonding properties and UV-vis spectra of [M_3(CO)_(12)] clusters(M=Ru,Os):a TD-DFT study

摘要

DFT and TD-DFT calculations(ADF program)were performed in order to analyze the electronic structure of the [M_3(CO)_(12)] clusters(M=Ru,Os)and interpret their electronic spectra.The highest occupied molecular orbitals are M-M bonding(sigma)involving different M-M bonds,both for Ru and Os.They participate in low-energy excitation processes and their depopulation should weaken M-M bonds in general.While the LUMO is M-M and M-CO anti-bonding(sigma~*),the next,higher-lying empty orbitals have a main contribution from CO(pi~*)and either a small(Ru)or an almost negligible one(Os)from the metal atoms.The main difference between the two clusters comes from the different nature of these low-energy unoccupied orbitals that have a larger metal contribution in the case of ruthenium.The photochemical reactivity of the two clusters is reexamined and compared to earlier interpretations.