Spectrophotometric investigations of aqueous solutions at elevated temperatures. Effect of temperature on the stability constants of the tris complexes of 1,10-phenanthroline, 5-nitro-1,10-phenanthroline and 2,2′-bipyridyl with iron (II)

Abstract

The overall stability constants (β₃) of the tris complexes of 1,10-phenanthroline, 5-nitro-1,10 phenanthroline and 2,2′-bipyridyl with iron (II) have been determined at various temperatures between 298 and 433 K by a new spectrophotometric method. The value of β₃ for all three complexes decreases regularly with increasing temperature as expected. Plots of log₁₀β₃ against 1/T have been used to determine average values of the thermodynamic functions (enthalpy and entropy) of the formation reaction in aqueous solution over the experimental temperature range.