Fig. 3: Schematic description of donor-acceptor electron transfer in the phenylene bridged Mo2 dimer.
From: Crossover between the adiabatic and nonadiabatic electron transfer limits in the Landau-Zener model
In the singly oxidized mixed-valence complex, the quadruply bonded [Mo2] unit serves as the electron donor and the cationic [Mo2] unit having a Mo–Mo bond order of 3.5 is the electron acceptor. Electron transfer causes δ bond breakage on the donor and formation on the acceptor, but the other bonds (σ and π) remain intact. While thermal electron self-exchange induced by medium fluctuations occurs between the two dimolybdenum units, nonadiabatic ET undergoes an optical pathway, which proceeds via vibronic transition under the Franck–Condon approximation by absorbing photons (hv), exhibiting the IVCT absorption band.
