MOSSBAUER STUDIES OF FEXZN1-X(4-AMINO-1,2,4-TRIAZOLE)3(NO3)(2) COMPLEXES POSSESSING THE (1)A(1)REVERSIBLE-ARROW-T-5(2) SPIN TRANSITION

Mossbauer studies were carried out for the mixed complexes FexZn1-x(AT r)(3)(NO3)(2)(0.2 less than or equal to x less than or equal to 1) hav ing a polynuclear chain structure, for which we had earlier found a si gnificant decrease in the (1)A(1) reversible arrow(5)T(2) spin transit ion temperature when iron was replaced with zinc. For these complexes, we have found for the first rime a tendency toward an increase in the chemical shifts and quadrupole splitting of iron atoms in the low-spi n state with the degree of their replacement by other metal atoms. A c orrelation between these Mossbauer spectral data and the spin transiti on temperature was found. The results of these studies are explained i n terms of the model of steric strains in molecular fragments of the c hain structure of the complexes appearing when iron atoms are replaced by zinc atoms.