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ABSTRACT: A benzo[h]quinolyl ligand provided pentacoordinate character for silicon in dibenzo[b,f]silepins. Substituents on the silicon center determined both conformations of the dibenzosilepin and luminescence properties in relation to charge transfer.
Organic Letters 05/2013; · 5.86 Impact Factor
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ABSTRACT: We present the development of the thiophene-fused boron dipyrromethene derivatives as efficient light absorbers. The two strategies for the evolution of the optical properties such as the peak positions of absorption wavelengths and molar extinct coefficients were established by the substituent effects: by introducing iodine groups, the bathochromic shifts of the peak positions (+15nm) and the enhancement of molar extinct coefficients were simultaneously received owing to the heavy atom effect. Next, it was found that the modification with the trifluoromethyl group contributed to the large bathochromic shift (+60nm) because of the lowering effect on the lowest unoccupied molecular orbital of the dye by the substituent. Finally, we obtained the dyes with large molar extinct coefficients (184,140M(-1)cm(-1) at 592nm, 72,180M(-1)cm(-1) at 623nm), sharp absorption bands, and low emissions.
Bioorganic & medicinal chemistry 04/2013; · 2.82 Impact Factor
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ABSTRACT: The influence on the efficiencies of the triplet-triplet annihilation (TTA)-supported upconversion by oxygen under biomimetic conditions was investigated. From the solution containing the dendrimer complexes based on polyhedral oligomeric silsesquioxane (POSS)-core dendrimer with the Pt complex of octaethylporphyrin (PtOEP) and anthracene in PBS, the fluorescence emission of anthracene depending on the dissolved oxygen (DO) concentrations via the TTA-supported upconversion was obtained with the excitation light at 540nm. In particular, we observed strong emission only under hypoxic conditions. In addition, it was found that the emission intensity via TTA-supported upconversion can be reversibly regulated by the DO concentrations in the solution.
Bioorganic & medicinal chemistry 03/2013; · 2.82 Impact Factor
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ABSTRACT: We designed and synthesized air- and moisture-stable gallafluorenes in which two benzene rings were bridged by the four-coordinate gallium atoms. The series of gallafluorenes were prepared by introducing electron-donating and -withdrawing groups through Suzuki-Miyaura coupling reactions. The gallafluorenes showed unique emissions via their triplet states in the presence of B(C6F5)3. These emissions were obtained via the triplet exciplex of gallafluorene and B(C6F5)3.
Journal of the American Chemical Society 03/2013; · 9.91 Impact Factor
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ABSTRACT: A series of boron ketoiminate derivatives that exhibited clear aggregation-induced emission (AIE) characteristics (in THF: Φ(PL) ≤0.01; in the solid state: Φ(PL) =0.30-0.76) were prepared by the reactions of 1,3-enaminoketone derivatives with boron trifluoride-diethyl etherate. The structures and optical properties were investigated by UV-visible spectroscopy, photoluminescent (PL) spectroscopy, and X-ray single-crystal measurements. These results indicate that the AIE characteristics were derived from molecular motions of the boron-chelating rings with a boronnitrogen (BN) bond. Furthermore, the optical properties were controllable by steric hindrance of the substituted groups on the nitrogen atom.
Chemistry 01/2013; · 5.93 Impact Factor
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ABSTRACT: For detecting reduced glutathione (GSH) with a (19)F NMR spectroscopy with time-specificity, we developed the probes based on gold nanoparticles modified with the fluorinated groups via the thermally-cleavable linkers. Before the heating treatment with the probe, the maleimide moiety as a binding site with GSH in the probe is inactivated by cycloaddition of furan. At this silent state, the magnitude of (19)F NMR signals from the fluorinated groups was suppressed. By heating for the activation of the probe, the maleimide moiety was produced via retro Diels-Alder reaction, and (19)F NMR signals were observed. From this moment, GSH started the reaction with the probe via Michael addition to the maleimide moiety, leading to the observation of the new peak in (19)F NMR spectra. Finally, the amounts of GSH were determined from the increase of the magnitude of (19)F NMR signals.
Bioorganic & medicinal chemistry letters 11/2012; · 2.65 Impact Factor
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ABSTRACT: The o-carborane-based π-conjugated compound, benzocarborano- [2,1-b:3,4-b']dithiophene was synthesized. Its crystal structure revealed high coplanarity for the two thiophene rings of the 2,2'-bithiophene skeleton, which is fixed in the cisoid structure by the o-carborane unit. Theoretical calculations indicated non-aromaticity for its center C(6) ring moiety as well as decreased HOMO and LUMO levels. The o-carborane moiety provides an electron-withdrawing character to the 2,2'-bithiophene unit through an inductive effect.
Chemistry 07/2012; 18(36):11251-7. · 5.93 Impact Factor
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ABSTRACT: Reactions of 10-benzo[h]quinolyllithium with a series of organosilanes led to the formation of neutral pentacoordinate complexes. The diethynyl-substituted complex was able to be converted to di(arylethynyl)-substituted ones by the Sonogashira-Hagihara coupling reaction. Electronegative substituents shortened N-Si distances and enhanced fluorescence intensity from the complexes.
Chemical Communications 07/2012; 48(68):8541-3. · 6.17 Impact Factor
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ABSTRACT: Our work on the characteristics of organoboron-containing polymers is reviewed. The electronic interaction and correlation involving organoboron complexes are responsible for the optical and electric properties of the polymers. To understand the origins of these properties and apply them to the next generation of new materials, we have gathered not only fundamental knowledge on the electronic states and behaviors of each organoboron complex in the polymers but also on the functions of the polymers in devices. In this article, we introduce our findings obtained from a series of studies on polymers involving cyclodiborazane, quinolate, diketonate, dipyrromethene, pyrazabole, and carborane complexes. In particular, there is a focus on results from recent work.
Macromolecular Rapid Communications 06/2012; 33(15):1235-55. · 4.60 Impact Factor
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ABSTRACT: We report the tumor cell-selective prodrugs based on the arsonic acid-presenting iron oxide nanoparticles. We synthesized the well-dispersed nanoparticles having arsonoacetic acid which is composed of the low toxic As(V) form. From the analyses of the reaction products, it is suggested that the reduction by dithiothreitol with arsonoacetic acid and the modified nanoparticles could generate the highly-toxic As(III) species. In the MTT assays, it was found that the cell viabilities of HeLaS3 and especially HepG2 were reduced in the presence of the modified nanoparticles. In contrast, a slight effect on viability was observed with primary mouse hepatocytes. The viabilities showed good agreements with the amounts of intracellular reduced glutathione concentrations. Furthermore, the valid concentrations of the modified nanoparticles for tumor-specific cytotoxicity were similar level in MRI measurements. These results indicate that arsonic acid-presenting nanoparticles should be a good platform for developing highly-sensitive tumor-specific prodrugs.
Bioorganic & medicinal chemistry 06/2012; 20(15):4675-9. · 2.82 Impact Factor
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ABSTRACT: The (19)F NMR probes for the HNO detection are reported. We synthesized the probe molecules with the paramagnetic Cu(II) complex and fluorine atoms using a cubic silsesquioxane. By using the magnetism changes of the Cu(II) to Cu(I) in the complex by the reduction with HNO, the (19)F NMR signal intensities of the probe increased. Noteworthily, our probes have superior resistance to reduced glutathione which is the major intracellular molecule to maintain the reductive environment and the competitor in the reduction of Cu(II) against HNO.
Bioorganic & medicinal chemistry 06/2012; 20(15):4668-74. · 2.82 Impact Factor
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ABSTRACT: New aromatic ring-layered polymer comprising the 2,7-linked carbazole and xanthene units was synthesized by the Sonogashira
coupling reaction. The structure and optical properties of the 2,7-linked carbazole-layered polymer were compared with those
of the 3,6-linked carbazole-layered polymer by using their model compounds.
KeywordsAromatic ring-layered polymer-Conjugated polymer-Carbazole-Xanthene
Polymer Bulletin 04/2012; 65(5):465-476. · 1.53 Impact Factor
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ABSTRACT: The regulation of electron transfer between a conjugated polymer and ligands orthogonally connected to the main-chain is reported. Poly(arylene-ethynylene)s containing aminoquinoline-borafluorene complexes in the main-chain are synthesized in good yields by a Sonogashira-Hagihara coupling. Single crystal X-ray analysis of a model compound has elucidated the complex's structure in which the aminoquinolate moiety and the borafluorene ring are connected directly and orthogonally. Moreover, the optical properties of the polymers are characterized by UV-vis absorption and photoluminescence spectra. Perfluorinated alkyl chain-containing polymers show strong emission, while hydrocarbon chain-containing ones exhibit only a slight emission. DFT calculation suggests that an electron transfer from the excited main-chain to the aminoquinolate ligand is suppressed because of the lowered LUMO level by introducing the electron withdrawing groups, resulting in the significant emission.
Macromolecular Rapid Communications 01/2012; 33(6-7):550-5. · 4.60 Impact Factor
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ABSTRACT: We report that a polyhedral oligomeric silsesquioxane (POSS) core in a dendrimer can enhance the affinity of the molecular recognition via hydrogen bonds between 1,8-naphthyridine and guanosine nucleotides. The complexation of the naphthyridine ligands with a series of guanosine nucleotides was investigated, and it is shown that the POSS core should play a significant role in the stabilization of the complexes via hydrogen bonds. Finally, we demonstrate that the 1,8-naphthyridine ligand can selectively recognize guanosine triphosphate by assisting with the POSS-core dendrimer.
Organic & Biomolecular Chemistry 01/2012; 10(1):90-5. · 3.70 Impact Factor
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ABSTRACT: We demonstrate that the POSS-core dendrimer induced various kinds of favourable properties of trisvinyl-pyridinium triphenylamine (TP3PY) as a bioprobe. By using the amphiphilicity of the POSS core, the complexes of TP3PY with G2 POSS-core dendrimer were prepared, and the series of properties were investigated for the application as a bioprobe. Initially, it was shown that the adsorption of TP3PY onto the vessels was highly prohibited by the complex formation with the dendrimers. The solution states of the dendrimer complexes were maintained at least for 7 days. Moreover, it was found that the improvement of quantum yields and the elongation of fluorescent lifetimes were observed by the complexation with the dendrimers. Similar photochemical properties were obtained in a glassy state of 2-methyltetrahydrofuranat -196°C. The molecular rotations occurring at the excited state could be restricted by the complex formation with dendrimers. These characteristics induced by the complexation with the POSS-core dendrimer are of significance to improve the signal to noise ratio and the accuracy on the detection as a bioprobe.
Bioorganic & medicinal chemistry 12/2011; 20(2):915-9. · 2.82 Impact Factor
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ABSTRACT: For the quantitative assessment of the glutathione reductase (GR) activity with a (19)F NMR spectroscopy, we developed the heavy metal-free probes based on silica nanoparticles modified with water-soluble perfluorinated dendrimers via the disulfide linkers. Before enzymatic reaction, the molecular rotation of the perfluorinated dendrimers is highly restricted, and the magnitude of (19)F NMR signals from the perfluorinated dendrimers can be suppressed. By the reductive cleavage of the disulfide linkers with the reduced glutathione-mediated enzymatic reaction of GR, perfluorinated dendrimers can be released from the surfaces of the nanoparticles. Consequently, the (19)F NMR signals of perfluorinated dendrimers were recovered. The enzymatic activity of GR was determined from the increase of the magnitude of (19)F NMR signals. Finally, to demonstrate the feasibility of the probe in the presence of miscellaneous molecules under bio-mimetic conditions, the comparison study was executed with the cancer cell lysate. The value determined from our method showed a good agreement with that from the conventional method.
Bioorganic & medicinal chemistry 11/2011; 20(1):96-100. · 2.82 Impact Factor
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ABSTRACT: We describe the bimodal quantitative assay for enzymatic activity in (19)F NMR spectroscopy and fluorescence spectroscopy using a nanoparticle-based molecular probe. Perfluorinated dendrimers were tethered on silica nanoparticles with a phosphate-caged fluorescein as a linker. Before enzymatic reaction, the molecular rotation of the perfluorinated dendrimers should be highly restricted, and the (19)F NMR signals from the perfluorinated dendrimers were too broad to be detected relative to the noise level. Fluorescence signals of fluorescein were suppressed by the presence of the diphosphate groups. Following the enzymatic reaction with an alkaline phosphatase, perfluorinated dendrimers and fluorescein were released, and the NMR signals of perfluorinated dendrimers and strong fluorescence from fluorescein were correspondingly observed. The enzymatic activity and reaction rates of the hydrolysis of alkaline phosphatase were detected from the increases of fluorescence and (19)F NMR signals. Finally, the feasibility of the probe in the presence of miscellaneous molecules under biomimetic conditions was demonstrated by determining of the enzymatic activity in cell lysate. Quantitative analysis using both (19)F NMR spectroscopy and fluorescence spectroscopy can be accomplished.
Bioconjugate Chemistry 08/2011; 22(8):1484-90. · 4.93 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 06/2011; 49(16):3664 - 3670. · 3.92 Impact Factor
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ABSTRACT: We designed a novel ditopic bisterpyridyl ligand containing o-carborane that can construct a coordination polymer by complexation with metal ions. Through the use of Sonogashira-Hagihara coupling, the desired ligand molecule was successfully synthesized. Addition of Zn(II) ions rapidly underwent the generation of a fluorescent coordination polymer, which was confirmed by (1)H NMR, UV-vis, and fluorescent titration experiments. Furthermore, the electronic structure of the bisterpyridyl ligand molecules was drastically changed upon the complexation with metal ions. The obtained coordination polymer showed light blue emission derived from the intraligand charge transfer (ILCT) state, whereas a bare ligand molecule exhibited yellowish-green aggregation-induced emission (AIE) in a poor solvent such as water, because of the variable C-C bond in o-carborane.
Dalton Transactions 03/2011; 40(9):1919-23. · 3.84 Impact Factor
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ABSTRACT: A practical synthetic route for enantiomerically pure P-stereogenic diphosphacrowns was developed by using a P-stereogenic bisphosphine as a chiral building block. Their molecular structures were confirmed by NMR spectroscopy and X-ray crystallography. Complexation of the diphosphacrowns with palladium was carried out, and the corresponding palladium complexes were obtained. The P-stereogenic diphosphacrowns were applicable to the chiral ligand for the asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated ketone catalyzed by palladium. This reaction proceeded smoothly to afford the corresponding 1,4-addition products in high yield with good enantioselectivities.
The Journal of Organic Chemistry 02/2011; 76(6):1795-803. · 4.45 Impact Factor
