The unusual magnetic behavior of the first dendritic Fe(3+) complex with general formula [Fe(L)2](+)Cl(-)·H2O based on a branched Schiff base has been investigated by electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. EPR displays that complex consists of the three types of magnetically active iron centers: one S = 1/2 low-spin (LS) and two S = 5/2 high-spin (HS) centers with strong low-symmetry and weak distorted octahedral crystal fields. Analysis of the magnetic behavior reflected by I versus T (where I is the EPR lines integrated intensity of the spectrum) demonstrates that the dendritic Fe(3+) complex has sufficiently different behavior in three temperature intervals. The first (4.2-50 K) interval corresponds to the antiferromagnetic exchange interactions between LS-LS, LS-HS, and HS-HS centers. The appearance of a presumable magnetoelectric effect is registered in the second (50-200 K) temperature interval, whereas a spin transition process between LS and HS centers occurs in the third (200-330 K) one. The coexistence of the magnetic ordering, presumable magnetoelectric effect, and spin crossover in one and the same material has been detected for the first time. The Mössbauer spectroscopy data completely confirm the EPR results.
The magnetic properties of a new dendrimeric spin crossover Fe(III) complex, [Fe(L)2]+PF6−, where L = 3,5-di[3,4,5-tris(tetradecyloxy) benzoyloxy]benzoyl-4-salicylidene-N-ethyl-N-ethylene-diamine, are reported for the first time. EPR studies show that this compound undergoes a gradual spin transition in the temperature range 70–300 K and has antiferromagnetic ordering below 10 K. Mössbauer spectroscopy at 5 K confirms the presence of magnetic ordering in the dendrimeric iron complex.
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