title: Two polymorphs of (2-carboxyethyl)(phenyl)phosphinic acid.
abstract: Two polymorphs of (2-carboxyethyl)(phenyl)phosphinic acid, C(9)H(11)O(4)P, crystallize in the chiral P2(1)2(1)2(1) space group with similar unit-cell parameters. They feature an essentially similar hydrogen-bonding motif but differ slightly in their detailed geometric parameters. For both polymorphs, the unequivocal location of the hydroxy H atoms together with the expected differences in the P-O bond lengths establish unequivocally that both forms contain the S isomer; the protonated phosphinic acid and carboxy O atoms serve as hydrogen-bond donors, while the second phosphinic acid O atom acts as a double hydrogen-bond acceptor and the remaining carboxy O atom is not involved in hydrogen bonding. Thus, an undulating two-dimensional supramolecular layer aggregate is formed based on an R(4)(3)(20) ring unit. Such polymorphism derives from the rotation of the C-C single bonds between the two hydrogen-bond-involved carboxy and phosphinic acid moieties.
authors.affiliation: College of Chemistry and Life Science, Gannan Normal University, Ganzhou, Jiangxi 341000, People's Republic of China.
authors.forename: Qiao Sheng
authors.initials: QS
authors.lastname: Hu
authors.forename: Xiu Zhi
authors.initials: XZ
authors.lastname: Zhang
authors.forename: Shu Fen
authors.initials: SF
authors.lastname: Luo
authors.forename: Yu Hui
authors.initials: YH
authors.lastname: Sun
authors.forename: Zi Yi
authors.initials: ZY
authors.lastname: Du