Halogeno metallates of transition elements with cations of nitrogen-containing heterocyclic bases, IX. Moessbauer and ESR spectroscopic investigation of aquachloro- and bromoferrates(III). On the compatibility of structural information obtained by sp

摘要

The ~(57)Fe-Moessbauer spectrum of (dmpipzH_2)_2[Fe~(III)(H_2O)_2Cl_4][Fe~(III)Cl_4]Cl_2 (1) consists of two doublts caused by a strongly distorted octahedral and a non-distorted tetrahedral component. Both (dmpipzH_2)[Fe~(III)Br_4]_2 (2) and (trienH_2)[Fe~(III)Br_4]Br (3) show only one doublet indicating a more strongly distorted iron(III) species for 2 and a less-distorted one in the case of 3. For all compounds investigated, the ESR spectra reveal the existence of ground states with predominant antiferromagnetic coupling. The Neel temperatures amount to <4.2 K for 1, ～4 K for 3 and 48 K for 2. In the case of 2, both the Moessbauer and the ESR spectra reveal the formation of exchange-coupled {FeBr_4} units which has been attributed to a significant cation influence. The fine structure of residual paramagnetic [FeBr_4]~- subunits remaining in the crystalline matrix could be directly determined. Temperature dependent AC and DC susceptibility measurements of 2 and 3 confirmed the results.