Direct Evidence of a Photoinduced Electron Transfer in Diluted "Molybdenum-Copper" Molecular Compounds

For the first time, direct evidence of a photoinduced intramolecular electron transfer has been found in the "molybdenum-copper" family of cyanide complexes that corresponds to a [Mo-IV-Cu-II]->[Mo-V-Cu-I] transition. The design and synthesis of a diluted molecular system, [Mo(Zn(1-x)Cux)(2)-tren] (x = 0, epsilon, 1, 5 and 10 %,, with epsilon corresponding to ppm ratio), viewed as new model compounds, have allowed good characterization of the metastable states involved in the process and provided evidence for two different mechanisms. By using squid magnetometry, EPR spectroscopy and X-ray diffraction, the results of this study have confirmed not only the photoinduced electron transfer, but also supports the light-induced excited spin state trapping effect centred on the molybdenum, thought to be due to the presence of a high-spin state (S = 1). This article provides a better understanding of the photomagnetic behaviour in Mo-Cu complexes and reveals the importance of orbital overlap to differentiate the two effects.