Mössbauer studies of Fe x Zn1−x (4-amino-1,2,4-triazole)3(NO3)2 complexes possessing the1 A 1⇄5 T 2 spin transition

Mössbauer studies were carried out for the mixed complexes Fe_xZn_1?x(ATr)₃(NO₃)₂ (0.2≤x≤1) having a polynuclear chain structure, for which we had earlier found a significant decrease in the¹A₁ ⁵T₂ spin transition temperature when iron was replaced with zinc. For these complexes, we have found for the first time a tendency toward an increase in the chemical shifts and quadrupole splitting of iron atoms in the low-spin state with the degree of their replacement by other metal atoms. A correlation between these Mössbauer spectral data and the spin transition temperature was found. The results of these studies are explained in terms of the model of steric strains in molecular fragments of the chain structure of the complexes appearing when iron atoms are replaced by zinc atoms.