Abstract:
The magnetic properties and the influence of counterions on the spin crossover properties of two novel Fe(III) dendrimeric complexes of the second generation, namely [Fe(L)2]+X-, where L = 3,5-di(3,4,5-tris(tetradecyloxy)benzoyloxy)benzoyl-4-oxy-salicylidene-N'-ethyl-N-ethylenediamine X = Cl- (1), ClO4- (2), have been studied for the first time by magnetic susceptibility measurements and electron paramagnetic resonance (EPR) method in a wide (4.2-300 K) temperature range. EPR results showed that compound 1 contains about 98% of high-spin (HS, S = 5/2) and 2% of low-spin (LS, S = 1/2) Fe(III) centers, and undergoes an antiferromagnetic ordering below 7 K. The EPR integrated intensity of a broad line (g 2), corresponding to the HS iron(III) centers, passes through a broad maximum at Tmax 100 K, which is indicative of short-range correlation effects. The anomalous broadening of this EPR line at low temperatures with the critical exponent = 1.5 upon approaching the long-range orderi
