Cation-Templated Assembly of 613 and 623 Metalla-Links.

Facilitated by multiple stacking interactions between components, two kinds of metalla-links containing molecular Borromean rings (623 links) and head-to-tail cyclic [3]catenanes (613 links), as isomers, were constructed in high yield by introducing tri-µ-methoxyl-dinuclear complexes [(Cp*M)2(µ-OCH3)3][OTf] (M = RhIII or IrIII, Cp* = η5-pentamethylcyclopentadienyl, OTf = triflate) as unusual cationic guests during coordination-driven assembly. The topology of these intricate structures was controlled by strategically selecting two dipyridyl ligands that differ in their coordination orientations, as evidenced by X-ray crystallography and electrospray ionization-time-of-flight/mass spectrometry analysis. The behavior of the abovementioned metalla-links in solution was monitored and further studied by the detailed NMR techniques.

Self-Assembly of Molecular Figure-Eight Knots Induced by Quadruple Stacking Interactions.

Molecular figure-eight knot (notation: 41) is extremely rare and presents great synthetic challenge due to its essentially complicated entanglement. To solve this synthetic problem, a quadruple stacking strategy was developed. Herein, we report the efficient self-assembly of figure-eight knots induced by quadruple stacking interactions, through the combination of four carefully selected naphthalenediimide (NDI)-based pyridyl ligands and Cp*Rh building blocks bearing large conjugated planes in a single-step strategy. Notably, slight size adjustment of the Cp*Rh units was found to affect the stability of the figure-eight knots in methanol. Additionally, reversible structural transformations between these figure-eight knots and corresponding metallorectangles could be achieved by concentration changes and solvent- and guest-induced effects. X-ray crystallographic data and NMR spectroscopy provide full confirmation of these phenomena.

Stereoselective Synthesis of a Topologically Chiral Solomon Link.

With the help of retrosynthetic analysis, we have realized the highly anticipated stereoselective synthesis of a topologically chiral Solomon link, by taking advantage of coordination-driven self-assembly and chiral induction by axially chiral ligands. Combination of the ligands (R or S)-2,2'-diethoxy-1,1'-binaphthyl-6,6'-bis(4-vinylpyridine) (R-L or S-L) with the binuclear iridium complex [Cp*2Ir2(DHBQ)(OTf)2] (Ir-B(OTf)2, H2DHBQ = 2,5-dihydroxy-1,4-benzoquinone) allows diastereoselective synthesis of the topological enantiomers P (Ir-1P) or M (Ir-1M) of a Solomon link, respectively. The main driving force for the formation of the Solomon link is the π-π interactions between chiral ligands.

Coordination-Directed Construction of Molecular Links.

Since the emergence of the concept of chemical topology, interlocked molecular assemblies have graduated from academic curiosities and poorly defined species to become synthetic realities. Coordination-directed synthesis provides powerful, diverse, and increasingly sophisticated protocols for accessing interlocked molecules. Originally, metal ions were employed solely as templates to gather and position building blocks in entwined or threaded arrangements. Recently, metal centers have increasingly featured within the backbones of the integral structural elements, which in turn use noncovalent interactions to self-assemble into intricate topologies. By outlining ingenious recent examples as well as seminal classic cases, this Review focuses on the role of metal-ligand paradigms in assembling molecular links. In addition, the ever-evolving approaches to efficient assembly, the structural features of the resulting architectures, and their prospects for the future are also presented.

Dynamic Interconversion between Solomon Link and Trapezoidal Metallacycle Ensembles Accompanying Conformational Change of the Linker.

A novel template-free Cp*Rh-based molecular Solomon link has been established through selection of the flexible ligand L as a linker and the half-sandwich rhodium(III) dinuclear fragment B1 as a rigid capping unit. Furthermore, we demonstrate that the self-assembly of the Solomon link based on the flexible ligand is both solvent- and concentration-dependent: the Solomon link is formed in concentrated methanolic solutions, whereas formation of a dinuclear trapezoidal rectangle is favored at low concentrations or in acetonitrile or DMF solutions. Remarkably, alteration of the solvent or concentration can promote a unique and dynamic interconversion between the two molecular species, accompanying conformational change of the ligand. The synthetic outcomes are supported by single-crystal X-ray diffraction analysis.

Selective Synthesis of Discrete Mono-, Interlocked-, and Borromean Ring Ensembles Based on a π-Electron-Deficient Ligand.

Herein, we present a new synthetic approach to achieve selective supramolecular transformations and construct different interlocked metallacycles featuring a π-electron-deficient thiazolo[5,4-d]thiazole-derived ligand. We demonstrate that the formation of mono-rings, interlocked rings ([2]catenanes) and Borromean rings can be controlled by adjusting the length of the binuclear half-sandwich RhIII and IrIII building blocks. Furthermore, a concentration effect or D-A stacking interaction between the pyrene guest and the thiazolo[5,4-d]thiazole-based ligand promotes a unique and reversible conversion between catenane structures and metalla-rectangles. The synthetic results are supported by single-crystal X-ray diffraction analysis.

Covalent Post-assembly Modification Triggers Structural Transformations of Borromean Rings.

A series of supramolecular transformation cascades are presented here, employing ligand exchange reactions, concentration-dependent Borromean ring (BR) linking and unlinking, and inverse electron-demand Diels-Alder (IEDDA) reactions. The new family of template-free, tetrazine-edged BRs are constructed by using ligand exchange reactions, and their concentration-dependent linking and unlinking reactions have been observed. Moreover, Borromean precursors have been demonstrated to further undergo supramolecular structural transformations induced by rapid and efficient IEDDA reactions to afford corresponding post-assembly modified architectures. Remarkably, subtle steric increases of the pyridazine fragments obtained by IEDDA reactions is regarded to induce controlled topological transformations in the cascade, unlinking the Borromean structures by using electron-rich dienophiles as triggering signals.

Europium metal-organic frameworks as recyclable and selective turn-off fluorescent sensors for aniline detection.

Seven Eu-(H)BDC compounds, [RMI][Eu2(BDC)3Cl] (R = ethyl (1), propyl (2), butyl (3), H2BDC = 1,4-benzenedicarboxylic acid), [EMI]2[Eu2(BDC)3(H2BDC)Cl2] (4), [Eu(BDC)(HCOO)] (5), [Eu(BDC)Cl(H2O)] (6) and [Eu3(BDC)4Cl(H2O)6] (7), were synthesized under ionothermal conditions. Compounds 4 and 6 behave as potential highly selective turn-off fluorescent sensors for aniline, which can be detected in mixtures of aniline with contrast organic amides or alkylbenzenes. Fluorescence quenching can be observed when compounds 4 and 6 mix with the samples containing aniline. Compounds 4 and 6 show basically unchanged emission intensities and rapid response to aniline after ten recycling tests, suggesting that the compounds have high stable recycle repeatabilities.

[Observation on therapeutic effect of acupuncture combined with chinese herbs on polycystic ovary syndrome of kidney deficiency and phlegm stasis type].

OBJECTIVE: To observe the clinical therapeutic effect of acupuncture combined with Chinese herbs on polycystic ovary syndrome of kidney deficiency and phlegm stasis type and probe into the mechanism. METHODS: Sixty-three cases of polycystic ovary syndrome of kidney deficiency and phlegm stasis type were randomly divided in to a combined acupuncture and Chinese herb group (n=32) treated with acupuncture at Qihai (CV 6), Guanyuan (CV 4), et al. and oral administration of Chinese herbs, and a simple Chinese herb group (n=31) treated with oral administration of the same Chinese herbs as in the combined acupuncture and Chinese herb group. The therapeutic effects and changes of follicle stimulating hormone (FSH), luteotropic hormone (LH), testosterone (T) and LH/FSH were compared between the two groups. RESULTS: The total effective rate was 93.8% in the combined acupuncture and Chinese herb group and 80.6% in the simple Chinese herb group, the former being significantly better than the latter (P < 0.05). The decrease of T in the combined acupuncture and Chinese herb group was significantly su perior to that in the simple Chinese herb group (P < 0.01). CONCLUSION: Acupuncture combined with Chinese herb therapy is superior to the simple Chinese herb in the clinical therapeutic effect on polycystic ovary syndrome of kidney deficiency and phlegm stasis type and decrease of T level, indicating this method is a better one for polycystic ovary syndrome of kidney deficiency and phlegm stasis type.