We present here two new materials, Er 2 (BDC) 3 (H 2 O) 6 (1) and Er 2 (NDC) 3 (H 2 O) 6 (2), where BDC stands for 1,4-benzenedicarboxylate and NDC stands for 2,6-naphthalenedicarboxylate ligand. In addition to their compositions, both structures adopt the same general arrangement: that is, a succession, along the c b-axis, of erbium atoms planes and organic spacers-ligands planes. The longer naphthalene derivative ligand increases the c parameter, but the organization inside the erbium cations planes is kept, including the nature and the geometry of the coordination spheres of the lanthanide ions, the number and the repartition of the water molecules, and the network of hydrogen bonding. The chemical nature, the flexibility, and the topology of the organic ligands allow the preservation of the organic-inorganic interface within the materials. This study clearly shows the opportunity to imagine new lanthanide-based materials with the tools of crystal engineering.

This contribution gives an overview on the different subjects treated in our group. One of our fundamental interests lies in the synthesis and study of low‐dimensional polymer and molecular solid state structures. We have chosen several synthetic approaches in order to obtain such compounds.Firstly, the concept of cutting out structural fragments from a solid state structure of a binary compound will be explained on behalf of BaI2. Oxygen donor ligands, used as chemical scissors on BaI2, allow obtaining three‐, two‐, one‐ and zero‐dimensional derived compounds depending on their size and concentration. Thus, a structural genealogy tree for BaI2 can be established. This method, transferred to alkali halides using crown ethers and calix[n]arenes as delimiting ligands, leads us to the subject of one‐dimensional ionic channels.A second chapter deals with the supramolecular approach for the synthesis of different dimensional polymer structures derived from alkaline earth metal iodides, and based on the combination of metal ion coordination with hydrogen bonding between the cationic complexes and their anions. Under certain circumstances, rules can be established for the prediction of the dimensionality of a given compound, thus contributing to the fundamental problem of structure prediction in crystal engineering.A third part describes a fundamentally new synthetic pathway for generating pure alkaline earth metal cage compounds as well as alkali and alkaline earth mixed metal clusters. In a first step, different molecular precursors, such as solvated alkaline earth metal halides are investigated as a function of the ligand size and reactivity. They are then reacted with some alkali metal compound in order to partially eliminate alkali halide and to form the clusters. The so obtained unique structures of ligand stabilized metal halide, hydroxide and/or alkoxide and aryloxide aggregates are of interest as potential precursors for oxide materials. Approaches to two synthetic methods of the latter, sol‐gel and (MO)‐CVD, are investigated with our compounds.In order to generate single source precursors for oxide materials, we started to investigate transition metal ions, especially Cu and Ag, using multitopic ligands. This has led us into the fundamental problematic of “crystal engineering” and solid state structure prediction and we found ourselves confronted to numerous interesting cases of polymorphism and pseudo‐polymorphism. Weak interactions, such as π‐stacking, H‐bonding and metal‐metal interactions, and solvent, counter ion and concentration effects seem to play important roles in the construction of such low‐dimensional structures.Finally, the physical properties of some of our compounds are described qualitatively in order to show the wide spectrum of possibilities and potential applications for the chemistry in this field.

As previously shown, alkali and alkaline earth metal iodides in nonaqueous, aprotic solvents behave like transition metal halides, forming cis- and trans-dihalides with various neutral O-donor ligands. These compounds can be used as precursors for the synthesis of new mixed alkali/alkaline earth metal aggregates. We show here that Ln2+ ions form isostructural cluster compounds. Thus, with LiOtBu, 50% of the initial iodide can be replaced in MI2, M=Ca, Sr, Ba, Eu, to generate the mixed-metal alkoxide aggregates [IM(OtBu)4{Li(thf)}4(OH)], for which the M--OH contacts were investigated by theoretical methods. With M'OPh (M'=Li, Na), a new mixed-metal aryloxide cluster type [MM'6(OPh)8(thf)6] is obtained for M=Ca, Sr, Ba, Sm, Eu. Their stability versus DME (DME=1,2-dimethoxyethane) as bidentate ligand is studied.

For the first time, unsubstituted mixed lithium and calcium phenolates could be structurally characterized in the solid state. Compound [CaLi 6 (µ 3 -OPh) 8 (thf) 6 ] (1), was obtained from the reaction of CaI 2 with LiOPh in THF, and features two heterocubane units fused via the calcium ion. Upon recrystallization from the bidentate ligand DME, the aggregate [Ca 2 (dme) 2 (µ-2295 OPh) 6 {Li(dme)} 2 ] (2) is obtained, in which the metal ions form a chain motif, being pairwise bridged by phenolate. The transformation of 1 into 2 upon addition of DME can be followed by 7 Li-NMR spectroscopy.

Two new alkaline earth metal halide adducts with oxygendonor polyether ligands are described. One of them, cis-[SrI 2 (diglyme) 2 ], features two terminally bonded anions in vicinal positions, and at an angle of ca. 90°. The low bond valence sum of ca. 1.9 indicates how well the cation is shielded by its ligands in the solid state, and that ligand exchange can be expected in solution and upon reaction. The second