title: Linking 31P magnetic shielding tensors to crystal structures: experimental and theoretical studies on metal(II) aminotris(methylenephosphonates).
abstract: The (31)P chemical shift tensor of the phosphonate group [RC-PO(2)(OH)](-) is investigated with respect to its principal axis values and its orientation in a local coordinate system (LCS) defined from the P atom and the directly coordinated atoms. For this purpose, six crystalline metal aminotris(methylenephosphonates), MAMP·xH(2)O with M = Zn, Mg, Ca, Sr, Ba, and (2Na) and x = 3, 3, 4.5, 0, 0, and 1.5, respectively, were synthesized and identified by diffraction methods. The crystal structure of water-free BaAMP is described here for the first time. The principal components of the (31)P shift tensor were determined from powders by magic-angle-spinning NMR. Peak assignments and orientations of the chemical shift tensors were established by quantum-chemical calculations from first principles using the extended embedded ion method. Structure optimizations of the H-atom positions were necessary to obtain the chemical shift tensors reliably. We show that the (31)P tensor orientation can be predicted within certain error limits from a well-chosen LCS, which reflects the pseudosymmetry of the phosphonate environment.
authors.affiliation: Department of Chemistry, Ludwig-Maximilians-Universität, D-81377 Munich, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Weber
authors.forename: Gisbert
authors.initials: G
authors.lastname: Grossmann
authors.forename: Konstantinos D
authors.initials: KD
authors.lastname: Demadis
authors.forename: Nikos
authors.initials: N
authors.lastname: Daskalakis
authors.forename: Erica
authors.initials: E
authors.lastname: Brendler
authors.forename: Martin
authors.initials: M
authors.lastname: Mangstl
authors.forename: Jörn
authors.initials: J
authors.lastname: Schmedt auf der Günne