Photoinduced magnetism

In the following sections, synthetic approaches to the preparation of multinu-clear cyanide complexes will be discussed. The structures of these compounds will be presented in the order of increasing nuclearity. Finally, the magnetic properties of cyanide complexes, including single-molecule magnetism, photoinduced magnetism, and spin crossover will be described. 

Quenching of the Intersystem Crossing to the Triplet State 521 Photoinduced 1RAV Studies 522 Time-Resolved Photoinduced Studies 524 Sensitization of Photoconductivity 525 Magnetic Properties 526... 

Magnetic field effects on the reaction kinetics or yields of photochemical reactions in the condensed phase have been studied [20-23]. They have proved powerful for verifying the mechanism of photochemical reactions including triplet states. Previously, we obtained photogenerated triplet biradicals of donor-acceptor linked compounds, and found that the lifetimes of the biradicals were remarkably extended in the presence of magnetic fields up to 1T [24]. It has been reported that Cgo and its derivatives form optically transparent microscopic clusters in mixed solvents [25,26]. The clustering behavior of fullerene (C o) is mainly associated with the strong three-dimensional hydrophobic interactions between the C o units. Photoinduced... 

Yonemura, H., Noda, M., Hayashi, K, Tokudome, H., Moribe, S. andYamada, S. (2002) Photoinduced intramolecular electron transfer reactions in fiillerene-phenothiazine linked compounds effects of magnetic field and spacer chain length. Mol. Phys., 100, 1395-1403. 

Not considered in this review are the removal of energetic equivalence by an applied field or stress where, as in a spinel, the energetically equivalent sites have differently oriented crystal-field axes. This lifting of site degeneracy coupled with charge transfer between mixed-valence states leads to such phenomena as magnetic after effect and photoinduced anisotropy ... 

Sato O. Photoinduced magnetization in molecular compounds. J Photochem Photobiol C Photochem Rev 2004 5 203-223. 

Kurreck, H, Eiger, G., Von Gersdorff, J., Wiehe, A., and Moebius, K. (1998) EPR studies on photoinduced electron transfer in triad model compounds of photosynthesis Applied Magnetic Resonance 14, 203-215. 

Wasielewski s research interests comprise photoinduced electron transfer and charge transport in organic molecules and materials, artificial and natural photosynthesis, self-assembly of nanoscale materials, spin dynamics of multispin organic molecules, materials for molecule-based optoelectronics and spintronics, and time-resolved optical and magnetic resonance spectroscopy. His research has resulted in over 300 publications. Dr. Wasielewski was elected a fellow of the American Association for the Advancement of Science in 1995, and has held numerous distinguished lectureships and fellowships. Among Wasielewski s recent awards are the 2004 Photochemistry Research Award of the Inter-American Photochemical Society and the 2006 James Flack Norris Award in Physical Organic Chemistry of the American Chemical Society. 

The heptanuclear complex [Cu°(tren)]6[Mo (CN)g] (C104)g (204) is characterized by the presence of six noninteracting Cu(ll) ions that surround the central diamagnetic [Mo (CN)g]" fragment [Fig. 45(Z))]. Upon irradiation with blue light (406 15 nm) at lOK, the compound exhibits a gradual increase in magnetic susceptibility that saturates after 10 h of continuous irradiation [Fig. 70(a)]. This effect was explained as a photoinduced electron transfer from Mo(lV) to Cu(ll) ions, which is promoted by the irradiation into the intervalence MMCT band... 

An increase in the magnetic response upon irradiation also was observed for the trinuclear complex [Cu (bpy)2]2[Mo (CN)g] (92), but in this special case, the photoinduced form [Cu bpy)2]2[Mo (CN)g] is postulated to arise from photooxidation of the Mo(lV) center in the presence of interstitial water. This conclusion is supported by the fact that the photoinduced conversion is irreversible. 

---