Characterization of iron(II)(α-diimine) chelates and their interactions with anionic, cationic and non-ionic micelles using the separation, spectrophotometric and computational methods

Abstract

The Fe(II)(α-diimine) chelates as well as diimine ligands were characterized by means of liquid chromatography and capillary electrophoretic methods with the help of molecular computational methods. The diimine ligands: 2,2′-bipyridine as well as 1,10-phenathroline and its derivatives (5-chloro, 5-methyl, 5-nitro, 4,7-dimethyl, 3,4,7,8-tetramethyl, and 4,7-diphenyl) were used. The chelate parameters such as: log P ow, hydrodynamic radius, molar volume and charge were estimated. The obtained results were used for the characterization of binding of Fe(NN) (NN = α-diimine) chelates to micelles. In the second part of the work by means of spectrophotometery, it was established that the MLCT (metal-to-ligand charge transfer) bands of all Fe(NN) chelates were no solvent sensitive. The decrease in λ max (blue shift) of MLCT band of Fe(NN) chelates was observed in solutions of charged micelles. It was concluded that the hydrophobicity of Fe(II)(NN) was found to be responsible for the chelate localization into micellar structure, whereas the surface electrostatic potential of the charged micelle was affected the MLCT band of Fe(II)(NN) chelates. To rationalize the observed effect the molecular modeling method was applied. It was established the stability of λ max of MLCT band of Fe(NN) in solvents is mainly due to the D 3 symmetry of the chelate. In the micellar phase, the distortion of the chelate geometry, thus the distortion of D 3 symmetry from D 3 to C 2 leads to the observed blue shift in λ max of MLCT band. It was proposed that the blue shift in the MLCT band could be used for estimating the values of the surface potential of micelle and for establishing the relative hydrophobic character of the micellar interface.