
%0 Journal Article
%A Abushamleh, AS 
%A Goodwin, HA 
%T Metal-Complexes of 1,10-Phenanthroline Derivatives. XV. Complexes of 2-(3,5-Dimethylpyrazol-1-yl)-1,10-phenanthroline
%J Australian Journal of Chemistry
%D 1988/06/01
%V 41
%N 6
%P 873-880
%K 
%R https://doi.org/10.1071/CH9880873
%U https://www.publish.csiro.au/paper/CH9880873 
%X Iron(II) and nickel(II) bis ( ligand ) complexes of 2-(3,5-dimethylpyrazol-1-yl)-1,10-phenanthroline (L) have been prepared. The field strength of L as determined from spectral data for the nickel complex is in the range encompassing the critical value at the singlet (1A1) &#8596; quintet (5T2) crossover for iron(II). The magnetic properties of the iron(II) complex both in solution and in the solid state are anomalous, and indicative of the occurrence of a thermally induced spin transition. Mossbauer spectral data confirm this, and reveal separate contributions from the singlet and quintet species with a strong temperature-dependence of their relative intensities. Magnetic data for the complex in solution are consistent with a simple high spin &#8596; low spin equilibrium, and lead to values of &#916;H = 23±0.5 kJ mol-1 and &#916;S = 66±5 J K-1 mol-1 for the low spin &#8594; high spin transformation. 
