Ultrafast spin crossover in a single crystal

Femtosecond spectroscopy and electron diffraction are used to characterize spin crossover in single crystal iron(II)-tris(bipyridine)-bis(hexafluorophosphate). The high-spin lifetime is reduced compared to in solution. Preliminary electron diffraction experiments show evidence of ultrafast Fe-N bond elongation associated with spin crossover and the subsequent molecular reorganization resulting from vibrational cooling.