Phosphonopropionic acid as a building block in supramolecular chemistry: salts with organic diamines

The structures of seven salts formed by phosphonopropionic acid with organic diamines are reported; in these salts, the hydrogen-bonded substructures formed by the anions can be zero-, one- or two-dimensional, while the overall hydrogen-bonded supramolecular structures are three-dimensional. The 1: 1 adduct, compound (1), formed between 1,2-bis(4'-pyridyl) ethene and phosphonopropionic acid is a salt, [{(C12H10N2) H-2}(2+)].[(C12H10N2)].[(C3H6O5P)(-)](2), in which both diamine components lie across centres of inversion in space group P2(1)/c. The anions form hydrogen-bonded head-to-head dimers, and these are linked by the two diamine units into sheets, which are themselves linked by C-H...O hydrogen bonds. With 2,2'-dipyridylamine the acid forms the hydrated salt [{(C10H9N3)H}(+)][(C3H6O5P)(-)].H2O (2), in which all components are disordered with occupancy 0.5 in space group Fmm2. The anions form head-to-tail dimers, which are linked into sheets by the cations, and the sheets are linked into a three-dimensional framework by the water molecules. The piperazine salt [{(C4H10N2)H-2}(2+)].[(C3H5O5P)(2-)] (3) contains simple anion chains linked into a three-dimensional framework by the two independent cations, both of which are centrosymmetric. In the hydrated salt formed by N,N'-dimethylpiperazine, [{(MeNC4H8NMe)H-2}(2+)].[(C3H6O5P)(-)](2).(H2O)(2) (4), head-to-tail anion chains combine with the water molecules to form a three-dimensional framework, which encloses voids that contain the cations. In the 4,4'-bipyridyl adduct [{(C10H8N2) H-0.72}(0.72+)][{(H0.5O)(3)PCH2CH2COOH0.78}(0.72-)] ( 5), there is extensive disorder of the H atoms that are bonded to N and O atoms, and the anion chains are linked by the cations into sheets, which are themselves linked by C-H...O hydrogen bonds. In the 1: 2 adduct formed with 1,2-bis(4'-pyridyl) ethane, [{(C12H12N2)H-2}(2+)].[(C3H6O5P)(-)](2) ( 6), where the cation lies across an inversion centre, the anions form molecular ladders. These ladders are linked into sheets by the cations, which are themselves linked by C-H...O hydrogen bonds. In the methanol-solvated salt formed with 2,6-dimethylpiperazine, [{(C6H14N2) H-2}(2+)].[(C3H6O5P)(-)](2). (CH4O)(0.34) (7), the anions form sheets that are linked into a three-dimensional framework by the cations. The supramolecular structures are compared with those of analogous salts formed by phosphonoacetic acid.