Structures of Sr-phosphonate layers intercalated by alkanedioles solved by molecular simulations

M. Pospíšil¹, P. Kovář¹, M. Pšenička¹, K. Melánová², J. Svoboda², V. Zima², L. Beneš³

¹Charles University, Faculty of Mathematics and Physics, Ke Karlovu 3, 12116 Prague 2, CZ

²Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, CZ. Present address: Joint Laboratory of Solid State Chemistry, Studentská 95, 532 10 Pardubice, CZ

³ Faculty of Chemical Technology, University of Pardubice, 53210 Pardubice, CZ

pospisil@karlov.mff.cuni.cz

Phosphonate layers represent group of compounds playing an important role in the design of new two-dimensional inorganic-organic hybrid materials. The usability of the layered phosphonates can be increased by intercalation of various organic species. We will show influence of intercalated 1,2 alkanediols [1] and 1,n alkanediols [2] on structural changes of Sr-phenylphosphonate layers. Intercalates are analysed by experimental techniques like X-ray diffraction, thermogravimetry, chemical analysis in combination with molecular modelling methods. Synthesized strontium phenylphosphonate intercalates with 1,2- and 1,n-diols (from 1,2-ethanediol to 1,2-hexanediol/ 1,n octanediol) show very good stability at ambient conditions. Calculated and experimental basal spacing are in very good agreement for both types of intercalates.

Models for 1,2 alkanediols suppose creation of cavities surrounded by six benzene rings. Every cavity contains one water molecule and one molecule of the diol for the 1,2-ethandiol to 1,2-butanediol intercalates. Two types of cavities are calculated for 1,2-pentanediol one with water molecule and another one with two water molecules. In the case 1,2-hexanediol intercalate two types of cavities are calculated containing one or two diol molecules. This variability causes more disordered structural models with longer alkyl chains with respect to models with shorter alkyl chains.

Another presented structure models are strontium phenylphosphonates intercalated with 1,n diols. Simulations show how the molecule conformation can be influenced by a shape of the host layer. On the base of experimental and calculation results, diols can be divided for two sets 1,2-to 1,4- diols and 1,6- to 1,8-diols. Diols with shorter alkyl chains are immersed between benzene groups and both OH groups are bonded to one host layer. Longer alkyl chains allow connection between two neighbouring layers to form nearly pillared structure in the interlayer and they are bonded by hydrogen bonds through water molecules. 1,5-diol was not prepared experimentally and simulations showed that the reason of this instability is the length of the alkyl chain.

1. J. Svoboda, K. Melánová, V. Zima, L. Beneš, M. Pšenička, M. Pospíšil, P. Kovář, J. Mol. Model., 22, (2016), 143.

2. K. Melánová, P. Kovář, L. Beneš, J. Svoboda, M. Veteška, M. Pospíšil, V. Zima, J. Coll. Int. Science, 1460, (2015), 181.

The authors thank the Czech Science Foundation (project number 14-13368S) for financial support.