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, [[(C(12)H(10)N(2))H(2)](2+)].[(C(12)H(10)N(2))].[(C(3)H(6)O(5)P)(-)](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 [[(C(10)H(9)N(3))H](+)].[(C(3)H(6)O(5)P)(-)].H(2)O (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 [[(C(4)H(10)N(2))H(2)](2+)].[(C(3)H(5)O(5)P)(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, [[(MeNC(4)H(8)NMe)H(2)](2+)].[(C(3)H(6)O(5)P)(-)](2).(H(2)O)(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 [[(C(10)H(8)N(2))H(0.72)](0.72+)].[[(H(0.5)O)(3)PCH(2)CH(2)COOH(0.78)](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, [[(C(12)H(12)N(2))H(2)](2+)].[(C(3)H(6)O(5)P)(-)](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, [[(C(6)H(14)N(2))H(2)](2+)].[(C(3)H(6)O(5)P)(-)](2). (CH(4)O)(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.