| Abstract: | A formula relating the1A1?5T2 spin transition temperature (Tc) in Fe(II) complexes to characteristics of the compounds is derived. With certain assumptions, Tc is determined by the splitting parameter ΔLS of eg- and t2g-orbitals for the low-spin complexes and by the frequency ratio of normal vibrations of the low- and high-spin phases. For the group of compounds possessing spin transitions, the values of ΔLS are found and analyzed. Correlations between Tc and ΔLS are established; the values of the change in the probability of the Mössbauer effect are correlated with those of entropy of spin transition. The correlations are substantiated. It is concluded that for mononuclear Fe(II) complexes possessing sharp spin transitions, Tc may not be significantly higher than for Fe(Phy)2(BF4)2 (Tc=282 K). |
