Easy Excited-State Trapping and Record High TTIESST in a Spin-Crossover Polyanionic FeII Trimer
journal contribution
posted on 2015-09-23, 00:00 authored by Verónica Gómez, Cristina Sáenz de Pipaón, Pilar Maldonado-Illescas, João Carlos Waerenborgh, Eddy Martin, Jordi Benet-Buchholz, José Ramón Galán-MascarósReaction
of the polysulfonated triazole ligand L = 4-(1,2,4-triazol-4-yl)ethanedisulfonate)
with iron(II) salts in water yields the trimeric species [Fe3(μ-L)6(H2O)6]6–. This polyanion, as the dimethylammonium salt,
shows a thermally induced spin transition above room temperature for
the central Fe position in the trimer with a large hysteresis cycle
(>85 K) and remarkably slow dynamics. This allows easy quenching
of
the metastable high-spin (HS) state via gradual cooling (5 K min–1). Once it is trapped, the HS state remains metastable.
Thermal energy is not able to promote relaxation into the low-spin
ground state below 215 K, with a characteristic TTIESST = 250 K, the highest temperature ever observed
for thermal trapping of an excited spin state in a switchable molecular
material.
