How N-(pyridin-4-yl)pyridin-4-amine and its methyl and nitro derivatives are arranged in the interlayer space of zirconium sulfophenylphosphonate: a problem solved by experimental and calculation methods.

Classical molecular simulation methods were used for a description of an arrangement of intercalated molecules N-(pyridin-4-yl)pyridin-4-amine (AH) and its derivatives, 3-methyl-N-(pyridin-4-yl)pyridin-4-amine (AMe), and 3-nitro-N-(pyridin-4-yl)pyridin-4-amine (ANO2) within a layered structure of zirconium 4-sulfophenylphosphonate. The intercalated molecules were placed between SO3H groups of the host layers. Their mutual positions and orientations were solved by molecular simulation methods and compared with the presented experimental results. Final calculated data showed differences of partially disordered arrangement of the intercalated molecules between zirconium 4-sulfophenylphosphonate layers. The calculation results revealed a dense net of hydrogen bonds connecting water molecules and the guests in the interlayer space and the sulfo groups of the host layers. We calculated the dipole moments of the AH, AMe and ANO2 guests in the final models in order to illustrate potential use of these materials in non-linear optics.

Geometry optimization of zirconium sulfophenylphosphonate layers by molecular simulation methods.

Classical molecular simulation methods were used for a detailed structural description of zirconium 4-sulfophenylphosphonate and zirconium phenylphosphonate 4-sulfophenylphosphonates with general formula Zr(HO3SC6H4PO3) x (C6H5PO3)2-x ·yH2O (x = 0.7-2; y = 0 or 2). First, models describing the structure of zirconium 4-sulfophenylphosphonate (x = 2) were calculated for the hydrated (y = 2) and dehydrated (y = 0) compounds. Subsequently, models for two mixed zirconium phenylphosphonate 4-sulfophenylphosphonates (x = 1.3 and 0.7) were calculated. Optimized models suggest that the presence of water molecules between sulfo groups creates a water-sulfonate layer with a system of hydrogen bonds. We suppose that this arrangement is the reason for a higher proton conductivity of the hydrated samples compared to dehydrated samples. When the water molecules are removed, a small decrease in the basal spacing (around 0.06 Å) is observed. This behavior is confirmed by the simulated models, where no significant changes in the structure on dehydration were observed except the absence of the water molecules and a lower number of hydrogen bonds between two adjacent sulfonate sheets. Due to the good crystallinity of the samples and the presence of sharp non-basal peaks in their X-ray diffraction patterns, Miller indices of the non-basal peaks in the diffraction patterns calculated from the models can be compared with those found in the experimental data. This allowed us to precisely describe for example (15 5-2) planes, from which mutual distances of the phenyl rings were determined to be 2.62 Å. Graphical Abstract Detailed ball and stick view into the interlayer structure of ZrSPhP1.3.