Hydrogen-Bonded Frameworks Assembled Using Amidinium···Phosphonate and Phosphonate···Phosphonate Interactions

We report the synthesis of hydrogen-bonded frameworks prepared from guanidinium, bis-amidinium, or tetra-amidinium cations and diphosphonate or tetraphosphonate anions. The frameworks are assembled by both charge-assisted amidinium···phosphonate and antielectrostatic phosphonate···phosphonate hydrogen bonds, of which the phosphonate···phosphonate interactions are notably shorter. Frameworks prepared from the tetrahedral tetraphosphonate building block contain relatively large water-filled channels but lose crystallinity upon drying. The crystal structure of a guanidinium···diphosphonate salt has an unusual structure related to classic Ward guanidinium···sulfonate frameworks but with an additional cation/solvent layer. This material includes toluene guests, which are held strongly within the crystal lattice.