Hydrogen-Bonded\nFrameworks Assembled Using Amidinium···Phosphonate\nand Phosphonate···Phosphonate Interactions

We report the synthesis of hydrogen-bonded frameworks\nprepared\nfrom guanidinium, bis-amidinium, or tetra-amidinium cations and diphosphonate\nor tetraphosphonate anions. The frameworks are assembled by both charge-assisted\namidinium···phosphonate and antielectrostatic phosphonate···phosphonate\nhydrogen bonds, of which the phosphonate···phosphonate\ninteractions are notably shorter. Frameworks prepared from the tetrahedral\ntetraphosphonate building block contain relatively large water-filled\nchannels but lose crystallinity upon drying. The crystal structure\nof a guanidinium···diphosphonate salt has an unusual\nstructure related to classic Ward guanidinium···sulfonate\nframeworks but with an additional cation/solvent layer. This material\nincludes toluene guests, which are held strongly within the crystal\nlattice.