Pentafluorophenylphosphonic Acid as a New Building Block for Molecular Crystal Fabrication

Molecular crystals have been prepared from pentafluorophenylphosphonic acid (4). These include 2C6F5PO3H2·H2O (4·4·H2O), [(C6F5PO3H–)(H3O+)]·C6F5PO3H2 (4·4–·H3O+), [(C6F5PO3H–)(NH4+)]·C6F5PO3H2 (4·4–·NH4+), [(C6F5PO3H–)(Me2NH2+)] (4–·DMA+), [(C6F5PO3H–)(Me2NH2+)]·H2O (4–·DMA+·H2O), [(C6F5PO3H–)(Me2NH2+)]·C6F5PO3H2 (4·4–·DMA+), [(C6F5PO3H–)(Me2NH2+)0.5(NH4+)0.5] (4–·DMA+·NH4+), and [(C6F5PO3H–)(+H3NCH2CO2H)] (4–·Gly+), where DMA+ = dimethylammonium Gly+ glycinium. All of the assemblies incorporate an ammonium cation, a water molecule, or hydronium ion in their structure, these included species act as adhesive agents. They interact via O/N–H···O hydrogen bonds C–H···O contacts with PO3H2 PO3H– moieties located polar sheets, forcing building blocks to assemble 2D layered arrangement. The robustness this arrangement is reminiscent that observed metal arylphosphonates guanidinium sulfonates, yet architectures described herein differ significantly second family compounds two aspects: lack puckering layers absence void spaces accommodate solvent molecules. Interestingly, however, just structural types recognized depending on size species: single-layer stacking motif bilayer motif. Even though bonding prevailing interaction systems, use perfluoroaryl groups also central, bring about weak C–F···π, π···π, C–F···F–C, C–F···H–C, O/N–H···F–C interactions help increase cohesion nonpolar regions. As result, new are created some cases those phenylphosphonic acid. However, weakness perfluoroaryl-based strength, sufficiently flexible allow changes organization aromatic response (ionization) occurring regions, structures 4·4·H2O 4·4–·H3O+. This situation quite unusual may be regarded kind acidity-modulated polymorphism. work presented here broadens knowledge molecular crystal formation arylphosphonic acids, research area largely dominated by carboxylic sulfonic acids. Also, computational evaluation 4·4–·H3O+ report suggests fluorinated show interesting prospects semiconductors, currently receiving increased attention.