Preferential solvation studies using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex

Article abstract of DOI:10.1039/b104093f

Solvent effects on the electronic spectra of dicyanobis(1,10-phenanthroline)iron(II) have been investigated in thirteen pure solvents and twenty binary solvent mixtures. In pure solvents, the shifts of the v_max values are found to depend on more than one of the known solvent parameters (AN, α, β, DN and π*). AN, α and π* are found to be the most important solvent parameters, exerting a considerable effect on the solvatochromic shifts of the title complex. The preferential solvation of dicyanobis(1,10-phenanthroline)iron(II) in binary solvent mixtures has been investigated by monitoring the metal-ligand charge transfer band of the indicator complex. Organic solvents are preferred near the indicator complex in aqueous binary solvent mixtures (negative deviation), except in regions rich in MeCN, Me₂CO and 1,4-dioxane, where water molecules are preferred over the organic component (dual behavior). However, the indicator complex is preferentially solvated by the component which has the higher acceptor number in non-aqueous binary solvent mixtures. Negative deviation was observed in binary mixtures ofand CHCl₃ Me₂CO with alcohols and positive deviation in mixtures of CHCl₃ with THF, DMSO and Me₂CO. Different criteria were considered to evaluate the extent of preferential solvation in different solvent mixtures, viz., the local molar fraction (X_A^L), the excess function (ΔX), the iso-solvation point (X_B^iso) and the preferential solvation constant (K_A/B). The preferential solvation data have been linearly correlated with the different solvent parameters.