Lyotropic Behavior of Diruthenium(II,III) Alkoxybenzoates in Dodecane

Abstract

The lyotropic behavior of three mixed valence diruthenium(II,III) alkoxybenzoates in dodecane mixtures has been analyzed. The studied compounds, namely, Ru2(3,4,5-B3OC14)4Cl [1] (3,4,5-B3OC14 = 3,4,5-tri(n-tetradecyloxy)benzoate), Ru2(3,4-B2OC14)4Cl [2] (3,4-B2OC14 = 3,4-di(n-tetradecyloxy)benzoate), and Ru2(3,5-B2OC14)4Cl [3] (3,5-B2OC14 = 3,5-di(n-tetradecyloxy)benzoate), were investigated at three different temperatures (40, 70, and 100 °C) for variable solvent concentrations (between 0 and 70 wt %). Mixing the complexes with up to 40−60 wt % of dodecane did not alter the nature of the low-temperature mesophase exhibited by the pure compound still showing a columnar hexagonal phase. However, it resulted in a substantial decrease of the viscosity for all of them and a depression of the melting point for [2]. For solvent concentrations greater than 40−60 wt % and high temperatures, the mixtures exhibited also a nematic columnar mesophase prior to the transition to the isotropic solution. At a structural level, the incorporation of solvent resulted in the swelling of the columns, leading to an increase of the intercolumnar distance up to a point where the columns lost their hexagonal order to give the columnar nematic phase. At higher concentrations of solvent, the mesophase dissolved into the solvent.