Direct Observation of Charge Transfer and Magnetism in Fe4Co4 Cyanide-Bridged Molecular Cubes

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We have studied the zero-dimensional cubane molecular correspondent of a Prussian blue analogue Cs–Fe 4 Co 4 at low temperature and high magnetic field by means of L-edge X-ray absorption spectroscopy and X-ray magnetic circular dichroism. We probe the magnetic and electronic structures of Fe and Co separately upon light irradiation, which allows us to observe directly the electron transfer coupled to a spin transition phenomenon within the molecular cubes and to investigate the nature of the metastable photoexcited state. The magnetic moments in the photoexcited state are found to be M = 1.3μ B ( M spin = 0.59μ B with large orbital moment, M orbit = 0.74μ B ) for low-spin Fe III and M = 1.5μ B ( M spin = 1.08μ B with orbital moment, M orbit = 0.41μ B ) for high-spin Co II at 2 K and 6.8 T. From our results, we evidence that a strong antiferromagnetic coupling between the metal ions can be ruled out.