Mir Wais Hosseini

Molecular tectonics: from molecular recognition of anions to molecular networks

Abstract One may apply concepts developed in the context of molecular recognition of anions by synthetic receptors in solution to the design of molecular tectons capable of generating molecular networks with anionic species in the crystalline phase. With respect to that, bis-cyclic amidinium dications are interesting tectons because they offer two positive charges allowing strong electrostatic charge–charge interactions with anions and four acidic protons divergently oriented and capable of forming two sets of two H-bond chelates. The latter characteristic is of interest for the generation of supramolecular chirality taking place within the second coordination sphere around anionic metal complexes adopting an octahedral coordination geometry.

Thiacalixarenes: Synthesis and structural analysis of thiacalix[4]arene and of p-tert-butylthiacalix[4]arene

The synthesis of tetrathiacalix[4]arene was achieved by the detertiobutylation of p-tert-butyltetrathiacalix[4]arene. X-ray diffraction studies revealed that in the solid state whereas p-tert-butyltetrathiacalix[4]arene forms inclusion complexes with solvent molecules, tetrathiacalix[4]arene undergoes self-inclusion leading to trimeric units. The same behaviour in the crystalline phase was also demonstrated for calix[4]arene.

Synthesis and Structural Analysis of a Helical Coordination Polymer Formed by the Self-Assembly of a 2,2′-Bipyridine-Based exo-Ditopic Macrocyclic Ligand and Silver Cations

The overall topology of coordination polymers can be controlled by means of the coordination preferences of the metal center and the structure of the bridging ligand. This is demonstrated here by the synthesis of a single-stranded helical coordination polymer by the self-assembly of the exo-ditopic ligand 1 and silver ions.

Reflexion on molecular tectonics

Molecular crystals are solid and periodic materials. These entities may be regarded as supramolecular architectures and thus be described as molecular networks, which are infinite molecular assemblies possessing translational symmetry and composed of complementary or self-complementary tectons capable of mutual interactions. This way of analysing structural features of crystalline materials called molecular tectonics not only permits crystals to be described as supramolecular architectures generated through molecular recognition processes but also allows molecular networks to be conceived with predicted connectivity and thus dimensionality through the design of tectons. A formal description and analysis of molecular networks is given.

Molecular Tectonics: Control of Reversible Water Release in Porous Charge-Assisted H-Bonded Networks

The combinations of bisamidium dicationic tectons 1-2H+ and 2-2H+ bearing two OH groups as additional H-bond donor/acceptor sites with [M(CN)6](3-)2 (M = Fe, Co, Cr) anions lead to the formation of robust porous crystals (decomposition temperature in the range of 240-300 degrees C) offering channels occupied by water molecules. The release and uptake of solvent molecules takes place through a reversible single crystal-to-single crystal transformation. Importantly, the temperature of dehydration can be increased by ca 40 degrees C through the decoration of the channels by introduction of OH groups on the backbone of the organic tecton.

Assembly of heteroleptic copper complexes with silver salts: from discrete trinuclear complexes to infinite networks.

The use of heteroleptic copper complexes functionalized with two differentiated coordinating groups for the elaboration of heterometallic extended networks is presented. Two novel 5-phenyl-dipyrrin (dpm) ligands appended with an imidazole or a pyrazole function, dpm-imid and dpm-pz, have been prepared and used as ligands for the synthesis of a series of heteroleptic (acacR)Cu(dpm) complexes (acacH = acetylacetonate; acacCN = 3-cyanoacetylacetonate). The X-ray crystal structures of these complexes revealed that, albeit no particular association mode is observed for the acac capping ligand, one-dimensional networks are formed with the acacCN capping ligand. Whereas the imidazole peripheral ligand is coordinated to the copper center of a neighboring complex in the structure of (acacCN)Cu(dpm-imid), such an interaction is absent for the pyrazole appended derivative, (acacCN)Cu(dpm-pz), leading to an association mode involving the peripheral nitrile group of the acacCN ligand. Upon reaction of the imidazole functionalized complexes, (acac)Cu(dpm-imid) and (acacCN)Cu(dpm-imid), with silver salts, trinuclear species, {[(acacR)Cu(dpm-imid)](2)Ag}(+), are formed as a result of the coordination of the azole nitrogen atom of two copper complexes to the silver ion. As expected, in the case of (acac)Cu(dpm-imid), these species do not self-assemble into an extended network owing to the absence of a peripheral coordinating group. However, for the (acacCN)Cu(dpm-imid) complex, the trinuclear species are equipped with peripheral nitrile groups, thus allowing the binding of metal centers. Consequently, these species self-assemble into one-dimensional polymers with association modes varying with the nature of the anion present in the silver salt.

Synthesis and solid state structural analysis of conformers of tetrakis((ethoxycarbonyl)methoxy)tetrathiacalix[4]arene

The role of alkaline metal cations in the synthesis and in determining the conformer distribution of tetrakis((ethoxycarbonyl)methoxy)tetrathiacalix[4]arene obtained by treatment of tetrathiacalix[4]arene 1 in acetone by ethyl bromoacetate in the presence of M 2 CO 3 was systematically investigated. Among the four possible conformers, the cone, partial cone and 1,3-alternate conformers were obtained, purified and structurally characterised by X-ray analysis in the solid state. Although for Li + no tetra substituted derivative was observed, for Na + the cone conformer was exclusively formed while for both K + and Cs + a mixture of partial cone and 1,3-alternate conformers was obtained.

Charge-assisted N–H(+)···O(−) and O–H···O(−) hydrogen bonds control the supramolecular aggregation of ferrocenedicarboxylic acid and bis-amidines

Directional N–H···O and O–H···O hydrogen bonds reinforced by charge assistance in the presence of anion–cation interactions have been used to design and synthesise a whole family of new organic-organometallic supramolecular salts. The compounds [C5H16N4]2+[(η5-C5H4COO)2Fe]2−·2C2H5OH, 1, [C5H16N4]2+{[(η5-C5H4COOH)(η5-C5H4COO)Fe]2}2−, 2, [C7H20N4]2+[(η5-C5H4COO)2Fe]2−·4H2O, 3, [C7H20N4]2+{[(η5-C5H4COOH)(η5-C5H4COO)Fe]2}2−, 4, and [C7H18O2N4]2+[(η5-C5H4COO)2Fe]2− ·4H2O, 5, have been obtained by reacting [(η5-C5H4COOH)2Fe] with the bis-amidines [C5H14N4], [C7H18N4] and [C7H16O2N4]. The self-assembly between singly and doubly deprotonated acids and the protonated cations is controlled by the stoichiometric ratio and by the choice of solvent. The effect of charge assistance on the N–H···O interactions is discussed on the basis of a CSD analysis.

Beyond classical coordination: silver–π interactions in metal dipyrrin complexes

Homo- and hetero-leptic Zn and Cu complexes of dipyrrin type ligands bearing mono- and di-cyanophenyl groups when combined with silver cations lead to the formation of Ag(I)-C=C double bond interactions unprecedented in the crystalline phase.

Tetrasulfinylcalix[4]arenes: Synthesis and solid state structural analysis

The synthesis of two tetrasulfinylcalix[4]arene was achieved by partial oxidation of tetrathiacalix[4]arene precursors. In both cases, the 1,3-alternate conformation of the calix units and the alternate orientation of the sulfoxide groups were demonstrated by X-ray diffraction studies in the solid state. In the case of tetrasulfinylcalix[4]arene, a 3-D network based on stacking interactions between the aromatic groups was observed.