A New Photomagnetic Molecular System Based on Photoinduced Self-Assembly of Radicals This work was supported by grants from DGI (project MAT 2000-1388-C03-01), CIRIT (project 2000 SGR00114), the 3MD Network of the TMR program of the EU (contract ERBFMRX CT980181), and the ESF program Molecular Magnets. D.R.-M. thanks the Generalitat de Catalunya for a postdoctoral grant, and I.R. thanks the CSIC-Carburos Metálicos and ESF for fellowships