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)H2}2+]·[(C12H10N2)]·[(C3H6O5P)−]2, in which both diamine components lie across centres of inversion in space group P21/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)H2}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)H2}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)H0.72}0.72+]·[{(H0.5O)3PCH2CH2COOH0.78}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)H2}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)H2}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.