Based on an unsymmetrical 2-pyridylphosphonate ligand, two types of Ln^III–Cu^II compounds with three-dimensional structures were obtained under hydrothermal conditions, namely, Ln₂Cu₃(C₅H₄NPO₃)₆⋅4 H₂O (1⋅Ln; Ln=La, Ce, Pr, Nd) and Ln₂Cu₃(C₅H₄NPO₃)₆ (2⋅Ln; Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho). Compounds 1⋅Ln are isostructural and crystallize in chiral cubic space group I2₁3. In these structures, each Ln ion is nine-coordinate and has a tricapped triprismatic geometry, while each Cu center is six-coordinate with an octahedral environment. The {LnO₉} polyhedra and {CuN₂O₄} octahedra are connected by edge sharing to form an inorganic open framework structure with a 3-connected 10-gon (10,3) topology in which the Ln and Cu atoms are alternately linked by the phosphonate oxygen atoms. Compounds 2⋅Ln are isostructural and crystallize in trigonal space group R. In these structures, the {LnO₆} octahedra are triply bridged by the {CPO₃} tetrahedra by corner sharing to form an infinite chain along the c axis. Each chain is connected to its six equivalents through corner sharing of {CPO₃} tetrahedra and {CuN₂O₂} planes to form a three-dimensional framework structure in which the Ln and Cu atoms are linked purely by O-P-O units. The formation of these two types of structures is rationalized by quantum chemical calculations, which showed that both the lanthanide contraction and the electron configuration of Cu^II play important roles. When Cu^II was replaced by Zn^II, only the first type of compounds resulted. The magnetic properties of complexes 1⋅Ln and 2⋅Ln were investigated. The nature of Ln^III–Cu^II (Ln=Ce, Pr, Nd) interactions is illustrated by comparison with their Ln^III–Zn^II analogues.

Reactions of 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid) [notpH₆, C₉H₁₈N₃(PO₃H₂)₃] with different lanthanide salts result in four types of Ln–notp compounds: [Ln{C₉H₂₀N₃(PO₃H)₂(PO₃)}(NO₃)(H₂O)]⋅4 H₂O (1), [Ln = Eu (1 Eu), Gd (1 Gd), Tb (1 Tb)], [Ln{C₉H₂₀N₃(PO₃H)₂(PO₃)}(H₂O)]Cl⋅3 H₂O (2) [Ln = Eu (2 Eu), Gd (2 Gd), Tb (2 Tb)], [Ln{C₉H₂₀N₃(PO₃H)₂(PO₃)}(H₂O)]ClO₄⋅8 H₂O, (3) [Ln = Eu (3 Eu), Gd (3 Gd)], and [Ln{C₉H₂₀N₃(PO₃H)₂(PO₃)}(H₂O)]ClO₄⋅3 H₂O (4), [Ln = Gd (4 Gd), Tb (4 Tb)]. Compounds within each type are isostructural. In compounds 1, dimers of {Ln₂(notpH₄)₂(NO₃)₂(H₂O)₂} are found, in which the two lanthanide atoms are connected by two pairs of O-P-O and one pair of μ-O bridges. The NO₃⁻ ion serves as a bidentate terminal ligand. Compounds 2 contain similar dimeric units of {Ln₂(notpH₄)₂(H₂O)₂} that are further connected by a pair of O-P-O bridges into an alternating chain. The Cl⁻ ions are involved in the interchain hydrogen-bonding networks. A similar chain structure is also found in compounds 3; in this case, however, the chains are linked by ClO₄⁻ counterions through hydrogen-bonding interactions, forming an undulating layer in the (011) plane. These layers are fused through hydrogen-bonding interactions, leading to a three-dimensional supramolecular network with large channels in the [100] direction. Compounds 4 show an interesting brick-wall-like layer structure in which the neighboring lanthanide atoms are connected by a pair of O-P-O bridges. The ClO₄⁻ counterions and the lattice water molecules are between the layers. In all compounds the triazamacrocyclic nitrogen atoms are not coordinated to the Ln^III ions. The anions and the pH are believed to play key roles in directing the formation of a particular structure. The fluorescence spectroscopic properties of the Eu and Tb compounds, magnetic properties of the Gd compounds, and the catalytic properties of 4 Gd were also studied.

This paper describes the syntheses and crystal structures of two new copper(II) diphosphonates with mixed ligands: [Cu₃(hedpH)₂(4,4′-bipy)(H₂O)₂]·2H₂O (1) and [Cu₃(hedpH)₂(4,4′-azpy)(H₂O)₂]·1.6H₂O (2) (hedp = 1-hydroxyethylidenediphosphonate, 4,4′-bipy = 4,4′-bipyridine, 4,4′-azpy = 4,4′-azobispyridine). Both adopt a two-dimensional layer structure containing neutral ladder-like chains of {Cu₃(hedpH)₂(H₂O)₂}_n linked by 4,4′-bipy or 4,4′-azpy ligands. The adjacent layers are held together by strong hydrogen bonds, thus generating a three-dimensional network with rectangular shaped channels. The lattice water is found in these channels. The magnetic properties of compounds 1 and 2 have also been investigated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)