Pressure-Temperature Relationships for Fe(II) Complexes of 1,10-Phenanthroline and 2,2′-Bipyridine

The complexes of the type Fe(phen)2X2 and Fe(bipy)2X2 (phen = 1, 10-phenanthroline, bipy = 2,2'-bipyridine) exist in high spin states (X = Cl−, Br−, N3−, NCO−, OAc−, HCOO−) or low spin states (X = CN−, CNO−, NO2−) or can exhibit the phenomenon of magnetic spin crossover. A recent study of the effect of pressure on the Mossbauer spectra for this type of complex indicates that high pressure is capable of partial conversion of the high spin state to the low spin state. However, there is still some disagreement concerning the interpretation of the Mossbauer data in systems which are in spin state equilibrium, as evidenced by some recent work on Fe(III) complexes with N, N-dialkyldithiocarbamates. High pressure studies have also been made on these Fe (III) dithio chelates. The results of these investigations on the solution electronic spectra indicate that the spin state is again pressure-sensitive.