Green and Orange Crystalline Forms of [VO{N-salicylidene-N′-3-ethoxysalicylidene-(R,R)-1,2-cyclohexane-diamine}], Separation of the Diastereomeric Pair, and Isomerization between Them in the Solid State
A pair of diastereomers, I and II, of the titled complex were separated by liquid chromatography, and each of them crystallized in two different colors, green and orange. I(green) and II(green) were assigned to a mononuclear square pyramidal structure, while I(orange) and II(orange) to a polynuclear linear chain structure. The orange complexes turned green by heating at 195 °C in a few minutes. All of the four complexes undergo isomerization at 195 °C in the solid state to give an equilibrium mixture, I : II ≈ 1 : 1.