Ligand-directed molecular architectures: self-assembly of two-dimensional rectangular metallacycles and three-dimensional trigonal or tetragonal prisms

Self-assembled construction of a sheet-type coordination polymer bearing cationic M2L4 cages: creation of channel-like space for removal of ClO4− and NO3− from aqueous solutions

A 2D coordination polymer bearing cationic Cu₂L₄ cages on the sheet showed ClO₄⁻ and NO₃⁻ removal activities from aqueous solutions.

Metal-driven assembly of peptidic foldamers: formation of molecular tapes

Supramolecular structures are formed by the self-assembly of a peptidic foldamer with silver cations. The conformation of the peptide is preserved in the metal–organic fibres.

Rhenium(I)-based bridgeless double metallocalix[4]arenes

Bridgeless double metallocalix[4]arenes possessing two orthogonally arranged dinuclear cavitands were obtained from a Re2(CO)10, rigid bis-chelating OO donor (H2-L), and a flexible bis-ditopic NN donor (L') by a one-pot approach.

Multidimensional transition metal complexes based on 3-amino-1H-1,2,4-triazole-5-carboxylic acid: from discrete mononuclear complexes to layered materials

The synthesis and structural characterization of five transition metal complexes with different dimensionality and incorporating residues of 3-amino-1H-1,2,4-triazole-5-carboxylic acid (H₂atrc) is reported: [Zn(Hatrc)₂(H₂O)] (1), [Mn(Hatrc)₂(H₂O)₂]·2H₂O (2), [Fe₂(Hatrc)₄(OH)₂]·6H₂O (3), [Cd(Hatrc)₂(H₂O)]_n (4), and [Mn(atrc)(H₂O)]_n·nH₂O (5). These materials could be prepared from solution (1–3), diffusion (4), or hydrothermal reactions (5) with various anions and L:M ratios. Structural details were revealed by single crystal X-ray diffraction. The discrete units composing compounds 1–3, the polymeric 1D chain of 4 and the 2D layer of 5 are further extended into 3D supramolecular architectures through the formation of hydrogen bonds.

Guest-induced transformation of a porphyrin-edged Fe(II)4L6 capsule into a Cu(I)Fe(II)2L4 fullerene receptor

The combination of a bent diamino(nickel(II) porphyrin) with 2-formylpyridine and Fe(II) yielded an Fe(II) 4 L6 cage. Upon treatment with the fullerenes C60 or C70 , this cage was found to transform into a new host-guest complex incorporating three Fe(II) centers and four porphyrin ligands, in an arrangement that is hypothesized to maximize π interactions between the porphyrin units of the host and the fullerene guest bound within its central cavity. The new complex shows coordinative unsaturation at one of the Fe(II) centers as the result of the incommensurate metal-to-ligand ratio, which enabled the preparation of a heterometallic cone-shaped Cu(I) Fe(II) 2 L4 adduct of C60 or C70 .

Self-assembly of a fac-Mn(CO)3-core containing dinuclear metallacycles using flexible ditopic linkers

Flexible dimanganese metallacycles have been achieved using Mn(CO)₅Br and adaptable ditopic pyridyl linkers. The host–guest chemistry of Mn(i)-dinuclear metallacycles has been explored.

Homochiral coordination cages assembled from dinuclear paddlewheel nodes and enantiopure ditopic ligands: syntheses, structures and catalysis

A series of homochiral (Cu₂)₂L₄ lantern cages have been synthesized, which can promote cyclopropanation with up to 99 : 1 diastereoselectivity.

Self-assembly of oxamidato bridged ester functionalised dirhenium metallastirrups: synthesis, characterisation and cytotoxicity studies

Hetero-topic self-assembly of Re₂(CO)₁₀ with oxamide ligands and ester-functionalised flexible ditopic-tectons afforded dinuclear metallacycles resembling a stirrup. The metallastirrups showed promising cytotoxic activity against few cancer cell lines in vitro.

Structural disorder and transformation in crystal growth: direct observation of ring-opening isomerization in a metal-organic solid solution

A rare example is reported in which discrete Ag2 L 2 ring and (AgL)∞ chain motifs [L = N,N'-bis(3-imidazol-1-yl-propyl)-pyromellitic diimide] co-crystallize in the same crystal lattice with varying ratios and degrees of disorder. Crystal structures obtained from representative crystals reveal compatible packing arrangements of the cyclic and polymeric isomers within the crystal lattice, which enables them to co-exist within a crystalline solid solution. A feasible pathway for transformation between the isomers is suggested via facile rotation of the coordinating imidazolyl groups. This chemical system could provide a chance for direct observation of ring-opening isomerization at the crystal surface. Mass spectrometry and (1)H NMR titration show a dynamic equilibrium between cyclic and oligomeric species in solution, and a potential crystallization process is suggested involving alignment of precursors directed by aromatic stacking interactions between pyromellitic diimide units, followed by ring-opening isomerization at the interface between the solid and the solution. Both cyclic and oligomeric species can act as precursors, with interconversion between them being facile due to a low energy barrier for rotation of the imidazole rings. Thermogravimetric analysis and variable-temperature powder X-ray diffraction indicate a transition to a different crystalline phase around 120°C, which is associated with loss of solvent from the crystal lattice.

The Biological Side of Water-Soluble Arene Ruthenium Assemblies

This review article covers the synthetic strategies, structural aspects, and host-guest properties of ruthenium metalla-assemblies, with a special focus on their use as drug delivery vectors. The two-dimensional metalla-rectangles show interesting host-guest possibilities but seem less appropriate for being used as drug carriers. On the other hand, metalla-prisms allow encapsulation and possible targeted release of bioactive molecules and consequently show some potential as drug delivery vectors. The reactivity of these metalla-prisms can be fine-tuned to allow a fine control of the guest’s release. The larger metalla-cubes can be used to stabilize the formation of G-quadruplex DNA and can be used to encapsulate and release photoactive molecules such as porphins. These metalla-assemblies demonstrate great prospective in photodynamic therapy.

Stepwise assembly of Pd(6)(RuL(3))(8) nanoscale rhombododecahedral metal-organic cages via metalloligand strategy for guest trapping and protection

Stepwise synthesis of nanosized Pd-Ru heteronuclear metal-organic cages from predesigned redox- and photo-active Ru(II)-metalloligand and naked Pd(II) ion is described. The resulting cage shows rhombododecahedral shape and contains a 5350 Å(3) cavity and 12 open windows, facilitating effective trapping of both polar and nonpolar guest molecules. Protection of photosensitive guests against UV radiation is studied.

Self-assembled coordination cages based on banana-shaped ligands

The combination of pyridyl ligands and square-planar Pd(ii) or Pt(ii) cations has proven to be a very reliable recipe for the realization of supramolecular self-assemblies. This tutorial review deals with the design, synthesis and host-guest chemistry of discrete coordination cages built according to this strategy. The focus is set on structures obeying the formula [PdnL2n] (n = 2-4). The most discussed ligands are bent, bis-monodentate bridges having their two donor sites pointing in the same direction. The structures of the resulting cages range from simple globules over intertwined knots to interpenetrated dimers featuring three small pockets instead of one large cavity. The cages have large openings that allow small guest molecules to enter and leave the cavities. Most structures are cationic and thus favour the uptake of anionic guests. Some examples of host-guest complexes are discussed with emphasis on coencapsulation and allosteric binding phenomena. Aside from cages in which the ligands have only a structural role, some examples of functional ligands based on photo- and redox-active backbones are presented.

Five MOFs with different topologies based on anthracene functionalized tetracarboxylic acid: syntheses, structures, and properties

Five MOFs based on a new designed rigid tetracarboxylate ligand have been synthesized and characterized. Highly diverse structures are formed from 2D layer to 3D frameworks based on different SBUs.

Subtle backbone modifications control the interpenetration of dibenzosuberone-based coordination cages

The self-assembly of interpenetrated double-cages was examined with respect to various synthetic modifications of the dibenzosuberone backbone.

Four new metal–organic frameworks based on a rigid linear ligand: synthesis, optical properties and structural investigation

Four coordination polymers have been synthesized based on a rigid linear carboxylate ligand and different lengths of imidazole ligands.

Preparation, crystal structures and conformations of six complexes based on 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene

Six manganese(ii), cobalt(ii), copper(ii) and cadmium(ii) complexes based on dibenzimidazolyl ligands with the 1,2,4,5-tetramethylbenzene linker have been prepared and characterized.

Two new coordination polymers, a trinuclear metal complex and their interconversion depending on the solvent

Irreversible conversion of the 1-D coordination polymer to the discrete trinuclear complex by contact with MeCN is described.