@Article{AngewChemIntlEd_53_3863, author = {A. Marino and P. Chakraborty and M. Servol and M. Lorenc and E. Collet and A. Hauser}, title = {{The role of ligand-field states in the ultrafast photophysical cycle of the prototypical iron(II) spin-crossover compound [Fe(ptz)$_6$](BF$_4$)$_2$}}, journal= {Angew. Chem. Intl. Ed.}, ISSN = {1433-7851}, volume= {53}, number= {15}, pages = {3863-3867}, url = {http://onlinelibrary.wiley.com/doi/10.1002/anie.201310884/abstract}, eprint= {http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref01396.pdf}, doi= {10.1002/anie.201310884}, keywords= {intersystem crossing;LIESST;ligand-field states;spin crossover;ultrafast spectroscopy}, abstract = {{Light-induced excited spin state trapping (LIESST) in iron(II) spin-crossover compounds, i.e., the light-induced population of the high-spin (S=2) state below the thermal transition temperature, was discovered thirty years ago. For irradiation into metal-ligand charge transfer (MLCT) bands of the low-spin (S=0) species the acknowledged sequence takes the system from the initially excited $^1$MLCT to the high-spin state via the $^3$MLCT state within ~150 fs, thereby bypassing low-lying ligand-field (LF) states. Nevertheless, these play role, as borne out by the observation of LIESST and reverse-LIESST on irradiation directly into the LF bands for systems with only high-energy MLCT states. Herein we elucidate the ultrafast reverse-LIESST pathway by identifying the lowest energy S=1 LF state as intermediate state with a lifetime of 39 ps for the light-induced high-spin to low-spin conversion on irradiation into the spin-allowed LF transition of the high-spin species in the NIR.}}, year = {2014} }