Spin-Crossover and Field-Induced Single-Molecule Magnet Behaviour in Metal(II)-Dipyrazolylpyridine Complexes

Haiet Douib (1, 2) , Louis Cornet (1) , Jessica Flores Gonzalez (1) , Elzbieta Trzop (3) , Vincent Dorcet (1) , Abdelkrim Gouasmia (2) , Lahcène Ouahab (1) , Olivier Cador (1) , Fabrice Pointillart (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 Université Larbi Tébessi [Tebessa]
3 IPR - Institut de Physique de Rennes

The reaction between the 2,6-di(pyrazol-1-yl)-4-(bromomethyl) pyridine (L) ligand and divalent transition metal salts led to the formation of three mononuclear complexes of formula [M(L)(2)](BF4)(2)center dot xMeNO(2) [M = Fe-II (1 center dot xMeNO(2)), x = 0 and 4, M = Co-II, x = 2 (2 center dot 2MeNO(2)) and]. Static magnetic measurements highlighted thermal spin crossover at high temperature (320-340 K) for the two Fe-II solvatomorphs nevertheless both the solvation degree and crystal packing had drastic influence on the shape and width of the hysteresis loop. Thus the 1 displayed abrupt and straight (6 K) hysteresis loop while for 1 center dot 4MeNO(2) the thermal spin transition could be described as a six-step gradual transition with the widest magnetic bistability range (35 K) for this kind of complexes. Irradiation at 530 nm of 1 center dot 4MeNO(2) provoked an efficient LIESST effect at low temperature (T-LIESST = 55 K). Finally dynamic magnetic measurements of 2 center dot 2MeNO(2) shown a field-induced mononuclear Single-Molecule Magnet behavior with Delta = 14.6(4) cm(-1) and tau(0) = 6.28(8) x 10(-7) s.

Mots clés: Iron; Cobalt; Dipyrazolylpyridine; Single-molecule magnet; Spin crossover

Domaines: Physique [physics]

Haiet Douib, Louis Cornet, Jessica Flores Gonzalez, Elzbieta Trzop, Vincent Dorcet, et al.. Spin-Crossover and Field-Induced Single-Molecule Magnet Behaviour in Metal(II)-Dipyrazolylpyridine Complexes. European Journal of Inorganic Chemistry, 2018, 2018 (40), pp.4452-4457. ⟨10.1002/ejic.201800819⟩. ⟨hal-01935237⟩