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Fluorescence-based assays should be feasible in aqueous media for effectively detecting the biological factors. However, numerous sensors have limited signal transductions and low fluorescence quantum yields due to the ingerently reduced excited state energy of fluorophores in aqueous solution, which reduces their sensitivity. This necessitates a smart sensing approach with an amplified fluorescence response for analytes in aqueous solution. Herein, a new building block which self-assembles in aqueous media, giving a micellar sturcuture with the hydrophobic π-extended conjugated system at the core and hydrophilic groups at the periphery, was devised for the first time. We demonstrated that the aggregated fluorophores in a micelle induce amplified fluorescence quenching, in which the excited electron efficiently migrates through π-extended conjugated system in a micelle, as in a polymeric system. Such feature differentiates this sensing approach from the numerous fluorescence-based tools previously developed for sensitive detection. This new system exhibited highly sensitive signal transduction for specific analytes even under actual bioanalytical conditions. [ABSTRACT FROM AUTHOR]

Abstract: Molecular knots have become highly attractive to chemists because of their prospective properties in mimicking biomolecules and machines. Only a few examples of molecular knots from the billions tabulated by mathematicians have been realized and molecular knots with more than eight crossings have not been reported to date. We report here the coordination‐driven [8+8] self‐assembly of a higher‐generation molecular knot comprising as many as sixteen crossings. Its solid‐state X‐ray crystal structure and multinuclear 2D NMR findings confirmed its architecture and topology. The formation of this molecular knot appears to depend on the functionalities and geometries of donor and acceptor in terms of generating appropriate angles and strong π‐π interactions supported by hydrophobic effects. This study shows coordination‐driven self‐assembly offers a powerful potential means of synthesizing more and more complicated molecular knots and of understanding differences between the properties of knotted and unknotted structures. [ABSTRACT FROM AUTHOR]

A molecular Solomon link was synthesized in high yield through the template-free, coordination-driven self-assembly of a carbazole-functionalized donor and a tetracene-based dinuclear ruthenium(II) acceptor. The doubly interlocked topology was realized by a strategically chosen ligand which was capable of participating in multiple CH ⋅⋅⋅π and π-π interactions, as evidenced from single-crystal X-ray analysis and computational studies. This method is the first example of a two-component self-assembly of a molecular Solomon link using a directional bonding approach. The donor alone was not responsible for the construction of the Solomon link, and was confirmed by its noncatenane self-assemblies obtained with other similar ruthenium(II) acceptors. [ABSTRACT FROM AUTHOR]

A hollow iridium-cornered prismatic cage was self-assembled without the assistance of any template. The cage was found to be capable of encapsulating heteroguest's triplet in its perfect sized cavity, producing the first demonstration of quintuple structure by an octahedral metal cornered prismatic cage. [ABSTRACT FROM AUTHOR]

A suite of three tetraruthenium metallacycles have been obtained from [2+2] self-assemblies between N, N′-Di-(4-pyridyl)-1,4,5,8-naphthalenetetracarbo-xydiimide ( 4) and one of the three dinuclear arene ruthenium clips, (η6- p- iPrC6H4Me)2Ru2( OO∩OO)][OTf]2 ( OO∩OO=oxalate 1, 2,5-dioxydo-1,4-benzoquinonato (dobq) 2, 5,8-dihydroxy-1,4-naphthaquinonato (donq) 3; OTf=triflate). All complexes were isolated in good yield (>85 %) as triflate salts and were fully characterized by using 1H NMR and UV/Vis spectroscopies, and high-resolution electrospray mass spectrometry. A single crystal of the metallarectangle 5 was suitable for X-ray diffraction structural characterization. The biological activities of the metallacycles were determined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays, establishing their in vitro anticancer properties. Our results show that for the AGC (gastric cancer) cell lines, the cytotoxicity of (donq)-containing SCC 7 exceeds that of cisplatin, which was used as a control. For HCT15 (colon cancer) cell lines, the cytotoxicity is comparable to both cisplatin and doxorubicin. An in vivo hollow fiber model was used to show growth-inhibitory activity against HCT15 and image-based cytometry experiments indicated that 7 induced apoptosis as the mode of cell death. Complex 7 also showed significant antitumor activity for multidrug-resistant HCT15/CLO2 cell lines, for which doxorubicin was ineffective. [ABSTRACT FROM AUTHOR]

Two novel nano-cage compounds, 8and 9, were prepared by self-assembly of the ruthenium complexes 4and 5, and the tripodal donor 1. The cytotoxicity of 8was found to be considerably stronger than that of cisplatin. The complex 8inhibited tumor cell proliferation by interfering into regulatory pathways of the cell cycle viaapoptosis. [ABSTRACT FROM AUTHOR]

A suite of two new tetraruthenium metallarectangles 5 and 6 have been obtained from [2+2] self-assemblies between dipyridylethynyltriptycene 2 and one of the two dinuclear arene ruthenium clips, [Ru 2 ( μ - η 4 -OO∩OO) ( η 6 - p -cymene) 2 ][OTf] 2 ; (OO∩OO = oxalate 3 ; 6,11-dihydroxy-5,12-naphthacenedionato (dotq) 4 ; OTf = triflate). These molecular rectangles are fully characterized by 1 H NMR spectroscopy, electrospray mass spectrometry. A single crystal of 6 was suitable for X-ray diffraction structural characterization. These new metallarectangles showed fluorescence behavior in solution, have been examined for emission quenching effects with various aromatic compounds, and show high quenching selectivity and sensitivity towards nitroaromatics, particularly picric acid and 1,3,5-trinitrobenzene. Excited-state charge transfer from the rectangles to nitro aromatic substrates can be used to develop selective fluorescent sensors for nitro aromatics. [ABSTRACT FROM AUTHOR]

Thetwo new large molecular metalla-rectangles 6and 8were obtained by the reaction of the two different arene–rutheniumacceptors [Ru2(p-cymene)2(μ-η4-C2O4)Cl2] (2) and [Ru2(p-cymene)2(donq)(Cl)2] (donq = 5,8-dioxido-1,4-naphthoquinonato) (4) with a symmetrical N,N′-bis(4-(pyridin-4-ylethynyl)phenyl)terephthalamide(1) donor ligand. Both metalla-rectangles were isolatedin good yields as triflate salts and were characterized by multinuclearNMR, ESI–MS, and UV–vis spectroscopy. X-ray crystallographyof 6confirmed a molecular metalla-rectangle. The cytotoxicitiesof metalla-rectangles 6–9were establishedin SK-hep-1 (liver cancer), AGS (gastric cancer), and HCT-15 (colorectalcancer) human cancer cell lines. The cytotoxicity of metalla-rectangle 8was found to be considerably stronger against all cancercell lines, even much more effective than the well-known anticancerdrugs doxorubicin and cisplatin. In addition, expressions of APC andp53, colorectal cancer suppressor genes, were significantly increasedfollowing exposure to the metalla-rectangle 8. [ABSTRACT FROM AUTHOR]

Abstract: The effect of ligand flexibility on the self-assembly of Pt(II) metallacycles was investigated. Three diazopyridyl ligands with different flexibilities were used to synthesize three nanoscale supramolecular complexes via Pt(II) mediated self-assembly. With comparatively less flexible ligands, 4,4′azobispyridine (2) and pyridine-4-carbaldehyde azine (3), formation of [3+3] molecular triangles was observed; in contrast, the most flexible of the three ligands, pyridine-3-carbaldehyde azine (4), yielded the [2+2] molecular rhomboid. All three complexes were characterized by multinuclear NMR (1H and 31P) and HR-ESI-MS, and the structure of complex 7 was further established by X-ray crystallography. These studies clearly showed that increased ligand flexibility entropically favors the formation of smaller metallacycles as the ligand can reduce angular strain through bending or conformational change. [Copyright &y& Elsevier]

Two new and large molecular rectangles 4and 5were synthesized from two different arene–ruthenium[Ru2(μ-η4-C2O4)(MeOH)2(η6-p-PriC6H4Me)2][O3SCF3]2(2) and [Ru2(p-cymene)2(donq)(OH2)2][O3SCF3]2(donq =5,8-dioxydo-1,4-naphthaquinonato) (3) acceptors and anew unsymmetrical N-(4-(pyridin-4-ylethynyl)phenyl)isonicotinamide (1) donor ligand. X-ray crystallographyof 4confirmed a molecular rectangle. The 1H NMR spectra of both rectangles 4and 5showed a mixture of two structural, head-to-tail(HTT) and head-to-head(HTH), type isomers in a1:1 ratio. The cytotoxicities of both rectangles have been establishedagainst Colo320 (colorectal cancer), A549 (lung cancer), MCF-7 (breastcancer), and H1299 (lung cancer) human cancer cell lines. The cytotoxicityof rectangle 5was found to be considerably strongeragainst all cancer cell lines than that of the reference drug cisplatin. [ABSTRACT FROM AUTHOR]

A novel, interlocked, self-assembled (M2L2)2 molecular architecture was constructed from an arene-Ru acceptor and a 1,4-di(pyridin-4-yl)buta-1,3-diyne donor. Two M2L2 units, with cavities of ∼7.21 Å, spontaneously interlock, with one unit encapsulating a twin in a non-catenane fashion. The dimeric host-guest complex thus formed is unique among two-dimensional self-assemblies and is stabilized by π-π interactions between the M2L2 units. [ABSTRACT FROM AUTHOR]