Tuning of the Self-Threading of Ring-in-Ring Structures in Aqueous Media.

A series of aryl-extended N-monoalkyl-4,4'-bipyridinium salts L (aryl=1,4-phenyl, 4,4'-biphenyl, 2,6-naphthyl and 9,10-anthracenyl) have been implemented by PdII /PtII -directed self-assembly into constitutionally dynamic systems (CDSs). As a result, the intended processes produced not only (en)M2 L2 (en=ethylenediamine) metallacyclic species but also (en)M4 L4 ring-in-ring aggregates, in equilibrium with the former, as a consequence of the hydrophobic nature of the aryl rings within the 4,4'-bipyridinium scaffold. The key feature of the obtained dynamic systems is the possibility of modulating their response against external stimuli by modifying the hydrophobic character of the ligand. While the different dynamic libraries follow the same trends upon changes in concentration, temperature, polarity of the medium, or addition of an aromatic chemical effector, subtle changes in the ligand hydrophobic core results in a fine-tuning of the speciation when applying a certain degree of the different stimulus. The exception is the anthracene-containing derivative, which does not form inclusion complexes or self-threaded structures.

Supramolecular Arene-Ruthenium Metallacycle with Thermotropic Liquid-Crystalline Properties.

Functionalization of 1,4-di(4-pyridinyl)benzene with poly(arylester) dendrimers bearing cyanobiphenyl end-groups gives a bidentate dendromesogenic ligand (L) that exhibits thermotropic liquid-crystalline properties. Combination of the diruthenium complex [Ru2(p-cymene)2(donq)][DDS]2 (M) with L, by coordination-driven self-assembly, affords the discrete and well-defined metallacycle M2L2. Like L, this supramolecular dendritic system displays mesomorphic properties above 50 °C. Both compounds L and M2L2 show smectic phases, characterized by a multilayered organization of the multiple components.

Stimuli-responsive metal-directed self-assembly of a ring-in-ring complex.

Concentration, temperature and/or solvent polarity control the speciation on the metal-directed self-assembly of a ditopic pyridyl ligand L with cis-protected Pd(ii) metal centers. This results into a controllable dynamic system, involving a [Pd2L2](6+) metallacycle and a [Pd4L4](12+) ring-in-ring complex.

Self-assembly of Pd2L2 Metallacycles Owning Diversely Functionalized Racemic Ligands.

We present herein the efficient palladium(II)-directed self-assembly in water of a series of nine new diversely functionalized metallacycles, owning hydroxy/alkoxycarbonyl/azidoalkyl exo pendant groups attached to ditopic N-monoalkyl/aryl-4,4'-bipyridinium/2,7-diazapyrenium ligands. The highly convergent and versatile synthetic route for the ligands uses the Zincke reaction between (dinitrophenyl)bipyridinium/diazapyrenium salts and racemic amines as the key step. The stereochemical outcome of the self-assembly of the Pd2L2 species is discussed on the basis of density functional theory quantum-chemical calculations.

Chains, necklaces and weaving chain-link grids from self-assembly reactions.

Assembly of two ditopic units, a phenanthroline substituted by 4-ethynyl pyridines at the 2-and 9-positions and a dimetallic paddlewheel, gives a linear chain polymer rather than a closed cyclic species, which would appear equally possible. The chain may be decorated by binding a copper-containing macrocycle around the phenanthroline units to form a polypseudorotaxane. When two phenanthroline ligands are assembled in a first step around copper(I), the paddlewheel acceptor can link them in a second step to form a two-dimensional interwoven grid that resembles the form of a chain-link fence. Each copper(I) centre in this structure is chiral, and the crystal shows complete homochirality, implying selection during the assembly process.

Dimensional matching of polycyclic aromatics with rectangular metallacycles: insertion modes determined by [C-H···π] interactions.

A family of Pd(II)/Pt(II) dinuclear receptors, designed to give a smooth increase in their cavity lengths (from 7.46-13.78 Å), is presented. Their inclusion complexes with a representative set of polycyclic aromatic substrates (naphthalene, carbazol, pyrene, and benzo[a]pyrene), were characterized and studied in aqueous solution and the solid state. By taking into account the dimensions of both receptors and substrates, an excellent complementarity was found between the size of the receptors and their ability to complex a given substrate. Furthermore, this dimensional matching results in specific binding modes depending on the ability of the guest to establish stabilizing [C-H···π] interactions with the host.

[2]Catenanes and inclusion complexes derived from self-assembled rectangular Pd(II) and Pt(II) metallocycles.

New inclusion complexes and [2]catenanes were self-assembled from a fluorescent diazapyrenium based ligand, a PdII or PtII complex, and cyclic or acyclic electron rich aromatic guests in aqueous and organic media. The molecular rectangles display a π-deficient cavity suitable to incorporate π-donor aromatic systems. The inclusion complexes between the metallocycles and phenylenic (2a,b) and naphthalenic (3a,b­5a,b) derivatives were studied by NMR, UV-vis and fluorescence spectroscopy. The crystal structure of (3b) ⊂ 1a·6PF(6) confirmed the insertion of the guest into the cavity of the metallocycle. Following the same self-assembly strategy, the use of polyethers 6,7 as π-donors resulted in the self-assembly of the [2]catenanes 1a(6,7)·6PF(6). Single-crystal X-ray analysis of 1a(7)·6PF6 revealed the [2]catenane structure being stabilized by π-stacking and [C­H···O] interactions.

Sycosiform tinea barbae caused by Trichophyton rubrum.

Tinea barbae is an uncommon superficial dermatophyte infection of the beard and moustache areas. It was more frequently observed in the past, before single-use razors became available. In most cases, the zoophilic ectothrix Trichophyton mentagrophytes and Trichophyton verrucosum are responsible for this type of infection. Its clinical presentation is variable; it can mimic many other skin disorders such as sycosis, iododerma, contact dermatitis, perioral dermatitis, and actinomycosis. We report a case of tinea barbae caused by an uncommon agent Trichophyton rubrum, misdiagnosed as sycosis, and review the approach and management of the disease.