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Easy Excited-State Trapping and Record High T TIESST in a Spin-Crossover Polyanionic Fe II Trimer

2015; American Chemical Society; Volume: 137; Issue: 37 Linguagem: Inglês

10.1021/jacs.5b07879

1943-2984

Verónica Gómez, Cristina Sáenz de Pipaón, Pilar Maldonado-Illescas, João C. Waerenborgh, Eddy Martín, J. Benet‐Buchholz, José Ramón Galán‐Mascarós,

Lanthanide and Transition Metal Complexes

Reaction 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.