Structural Arrangement of 4-[4-(Dimethylamino)phenylazo]pyridine Push–Pull Molecules in Acidic Layered Hosts Solved by Experimental and Calculation Methods

Abstract

4-[4-(dimethylamino)phenylazo]pyridine (further denoted as G) representing a type of push–pull molecules can be intercalated into α- and γ-modifications of zirconium phosphate (α-ZrP and γ-ZrP) and into zirconium (4-sulfophenyl)phosphonate (ZrSPP). The obtained intercalates form single phases with interlayer distances of 12.75, 16.31, and 24.11 � for α-ZrP�0.2G�1.5H2O, γ-ZrP�0.2G�1.5H2O, and ZrSPP�0.5G�1H2O, respectively. The increase of the interlayer distance upon intercalation suggests that the molecules of the intercalated guest lie parallel to the host layers. All intercalates were further characterized by IR and UV/Vis spectroscopy. The arrangement of the guests in the interlayer space was determined by molecular simulation methods. The calculations were performed separately for protonated and unprotonated forms of the guest in the models of hydrated and dehydrated α-ZrP and γ-ZrP intercalates. In the case of the α-ZrP intercalate, the presence of interlayer water stabilizes the head-to-tail arrangement of the guest molecules. Dehydration of this intercalate disturbs their arrangement, mainly in the case of protonated guest molecules. In the case of dehydrated γ-ZrP, the guest molecules are head-to-tail ordered, and the guest molecules in the hydrated form of γ-ZrP are more disordered than in the dehydrated intercalate. The simulations also describe a layer shift present in the dehydrated γ-ZrP intercalate, which explains why the rehydration of this intercalate is not possible.