Variable assembly of imidazole into α-VOPO4·2H2O

Abstract

α-VOPO₄·2H₂O reacts with Imidazole (Im) in anhydrous ethanol to give a layered composite with d_00I, = 10.3 Å, whereas in 95% ethanol it gives a phase with d_00I, = 8.8 Å; both have formula VOPO₄(Im)_1.0·nH₂O (8.8 Å phase, n= 0.2; 10.3 Å phase, n= 0.6). The 8.8 Å phase slowly changes to a third phase with d_00I, = 9.63 Å. Indirect evidence suggests that the 10.3 Å phase contains Im coordinated to intralayer vanadium and oriented vertically to the planes, whereas in the 8.8 Å phase the Im lies almost flat between the layers and is not coordinated, i.e., the materials may be considered ‘intercalation isomers’.