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metal phosphonates; hydrothermal reactions; layer compounds; magnetic property; intercalation
Abstract:
Hydrothermal reactions of N,N-bis(phosphonomethyl)aminoacetic acid
(HO2CCH2N(CH2PO3H2)(2)) With metal(II) salts afforded two new metal
carboxylate-phosplionates, namely, Pb-2[O2CCH2N(CH2PO3)(CH2PO3H)].H2O
(1) and {NH3CH2CH2NH3} (2). Among two unique lead(II) ions in the
asymmetric unit of complex 1, one is five coordinated by five
phosphonate oxygen atoms from 5 ligands, whereas the other one is
five-coordinated by a tridentate chelating ligand (1 N and 2
phosphonate O atoms) and two phosphonate oxygen atoms from two other
ligands. The carboxylate group of the ligand remains non-coordinated.
The bridging of above two types of lead(II) ions through phosphonate
groups resulted in a <002> double layer with the carboxylate group of
the ligand as a pendant group. These double layers are further
interlinkcd via hydrogen bonds between the carboxylate groups into a 3D
network. The nickel(II) ion in complex 2 is octahedrally coordinated by
a tetradentate chelating ligand (two phosphonate oxygen atoms, one
nitrogen and one carboxylate oxygen atoms) and two aqua ligands. These
{Ni[O2CCH2N(CH2PO3H)(2)][H2O](2)}(-) anions are further interlinked via
hydrogen bonds between non-coordinated phosphonate oxygen atoms to form
a <800> hydrogen bonded 2D layer. The 2H-protonated ethylenediamme
cations are intercalated between two layers, forming hydrogen bonds
with the non-coordinated carboxylate oxygen atoms. Results of magnetic
measurements for complex 2 indicate that there is weak Curie-Weiss
behavior with 0 = -4.4 K indicating predominant antiferromagnetic
interaction between the Ni(II) ions. Indication for magnetic
low-dimension magnetism Could not be detected. (C) 2003 Elsevier Inc.
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