Spin‐Crossover and Field‐Induced Single‐Molecule Magnet Behaviour in Metal(II)‐Dipyrazolylpyridine Complexes. Issue 40 (18th October 2018) - Douib, Haiet
Abstract : 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 · x MeNO2 [M = Fe II (1· x MeNO2 ), x = 0 and 4, M = Co II, x = 2 (2·2MeNO2 ) 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 the1 displayed abrupt and straight (6 K) hysteresis loop while for1·4MeNO2 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 of1·4MeNO2 provoked an efficient LIESST effect at low temperature (TLIESST = 55 K). Finally dynamic magnetic measurements of2·2MeNO2 shown a field‐induced mononuclear Single‐Molecule Magnet behavior with Δ = 14.6(4) cm –1 and τ 0 = 6.28(8) × 10 –7 s. Abstract : The three mononuclear complexes of Fe II and Co II involving the 2, 6‐di(pyrazol‐1‐yl)‐4‐(bromomethyl)pyridine (L ) displayed thermal and photo‐induced spin transition, and field‐induced Single‐Molecule Magnet behaviour respectively.