A novel ratiometric electrochemical biosensing strategy based on T7 exonuclease-assisted homogenous target recycling coupling hairpin assembly-triggered double-signal output for the multiple amplified detection of miRNA.

A novel ratiometric electrochemical biosensing strategy based on T7 exonuclease (T7 Exo)-assisted homogenous target recycling coupling hairpin assembly triggered dual-signal output was proposed for the accurate and sensitive detection of microRNA-141 (miRNA-141). Concretely, in the presence of target miRNA, abundant signal transduction probes were released via the T7 Exo-assisted homogenous target recycling amplification, which could be captured by the specially designed ferrocene-labeled hairpin probe (Fc-H1) on -electrode interface and triggered the nonenzymatic catalytic hairpin assembly (Fc-H1 + MB-H2) to realize the cascade signal amplification and dual-signal output. Through such a conformational change process, the electrochemical signal of Fc (IFc) and MB (IMB) is proportionally and substantially decreased and increased. Therefore, the signal ratio of IMB/IFc can be employed to accurately reflect the true level of original miRNA. Benefiting from the efficient integration of the T7 Exo-assisted target recycle, nonenzymatic hairpin assembly and dual-signal output mode, the proposed sensor could realize the amplified detection of miRNA-141 effectively with a wide detection range from 1 fM to 100 pM, and a detection limit of 200 aM. Furthermore, it exhibits outstanding sequence specificity to discriminate mismatched RNA, acceptable reproducibility and feasibility for real sample. This strategy effectively integrated the advantages of multiple amplification and ratiometric output modes, which could provide an accurate and efficient method in biosensing and clinical diagnosis.

Enzyme-free and triple-amplified electrochemical sensing of 8-hydroxy-2'-deoxyguanosine by three kinds of short pDNA-driven catalyzed hairpin assemblies followed by a hybridization chain reaction.

A sensitive and enzyme-free electrochemical aptasensor was constructed for the sensing of 8-hydroxy-2'-deoxyguanosine (8-OH-dG). In the process of constructing the aptasensor, triple signal amplification strategies were introduced to enhance the sensitivity. First, every aptamer/pDNA complex immobilized on magnetic beads could release three kinds of pDNAs when 8-OH-dG was introduced, which caused three-fold magnification of the target. Second, the released three kinds of pDNAs initiated catalyzed hairpin assembly between two hairpin DNAs (HP1 and HP2) on a gold electrode. Meanwhile, the three kinds of pDNAs were released again by a strand displacement reaction to obtain the next catalyzed hairpin assembly. Third, the emerging toehold of HP2 further induced a hybridization chain reaction (HCR) between two hairpin DNAs (HP3 and HP4), forming a long double-stranded DNA concatemer on the surface of the electrode. Finally, [Ru(NH3)6]3+, an electroactive cation, was adsorbed onto the long dsDNA concatemer by electrostatic interactions and consequently, an electrochemical signal was generated. Under this triple signal amplification, a low detection limit down to 24.34 fM has been obtained for 8-OH-dG determination, which is superior to those of most previously reported methods.

Morphological measurements and classification of the spinoglenoid notch: A three-dimensional reconstruction of computed tomography in the Chinese population.

BACKGROUND: The spinoglenoid notch (SGN) is the second most common location for suprascapular nerve (SN) entrapment; however, there are few relative morphological reports on this condition. Hence, the present morphological study mainly explored the anatomical structure and classification of the SGN and the relationship with entrapment of SN. MATERIALS AND METHODS: Four hundred seventy-eight scapulae were analysed thoroughly and systematically in this study. Anatomical structure and classification of the SGN were observed and measured by a three-dimensional (3D) reconstruction of computed tomography (CT). The measurement results were then analysed and recorded. RESULTS: Chinese scapulae were classified into three types at the SGN, and it was found that left scapulae had deeper SGN than right ones. Then, significant differences were also noted between sexes. Men had thicker, wider and deeper SGN than women. Type II (small U, 46.04%) was the most common. Type I (large U) was the widest (15.67±1.43mm) and deepest (13.71±2.39mm) compared with other types. Lastly, no significant differences in the above criteria were found in other measurements. CONCLUSIONS: These morphological measurements of the SGN may help to improve the diagnosis and successful treatment rate of the surgery for the SN entrapment, but the relative clinical trial is necessary to support it.

An ultrasensitive luminol cathodic electrochemiluminescence probe with highly porous Pt on ionic liquid functionalized graphene film as platform for carcinoembryonic antigen sensing.

The low-potential electrochemiluminescence (ECL) sensors based on cathodic light emission of luminol have caused more and more concerns due to their good stability and reproducibility. In this work, highly porous platinum (Pt) nanostructures on ionic liquid functionalized graphene film (GR-IL/pPt) were prepared as platform to construct a label-free ECL sensor for the detection of carcinoembryonic antigen (CEA). Due to their good biocompatibility, excellent electrocatalytic activity and highly porous structure, the as-prepared GR-IL/pPt composites benefited amplified cathodic ECL signal of luminol and high loading density of the CEA antibody. After CEA was incubated with the CEA antibody, the cathodic ECL signal of luminol decreased thanks to the less conductive immunocomplex. The proposed ECL immunosensor realized high sensitivity for CEA detection with a wide linear range from 0.001 fg mL-1 to 1 ng mL-1 and an extremely low detection limit of 0.0003 fg mL-1 (S/N = 3). Moreover, the sensor showed good specificity, stability and reproducibility, indicating that the provided strategy had a promising potential in clinical detection.

A versatile label-free electrochemical biosensor for circulating tumor DNA based on dual enzyme assisted multiple amplification strategy.

A versatile label-free electrochemical biosensor based on dual enzyme assisted multiple amplification strategy was developed for ultrasensitive detection of circulating tumor DNA (ctDNA). The biosensor consists of a triple-helix molecular switch (THMS) as molecular recognition and signal transduction probe, ribonuclease HII (RNase HII) and terminal deoxynucleotidyl transferase (TdT) as dual enzyme assisted multiple amplification accelerator. The presence of target ctDNA could open THMS and trigger RNase HII-assisted homogenous target recycling amplification to produce substantial signal transduction probe (STP). The released STP hybridized with the capture probe immobilized on a gold electrode, then TdT and assistant probe were further employed to fulfill TdT-mediated cascade extension and generate stable DNA dendritic nanostructures. The electroactive methyl blue (MB) was finally used as the signal reporter to realize the multiple electrochemical amplification ctDNA detection as the amount of MB is positively correlated with the target ctDNA. Combined with the efficient recognition capacity of the designed THMS and the excellent multiple amplification ability of RNase HII and TdT, the constructed sensing platform could detect KRAS G12DM with a wide detection range from 0.01 fM to 1 pM, and the limit of detection as low as 2.4 aM. Besides, the platform is capable of detecting ctDNA in biological fluid such as plasma. More importantly, by substituting the loop of THMS with different sequences, this strategy could be conveniently expanded into the detection of other ctDNA, showing promising potential applications in clinical cancer screening and prognosis.

Perylenetetracarboxylic acid and carbon quantum dots assembled synergistic electrochemiluminescence nanomaterial for ultra-sensitive carcinoembryonic antigen detection.

It is important to design a nice electrochemiluminescence (ECL) biological nanomaterial for fabricating sensitive ECL immunosensor to detect tumor markers. Most reported ECL nanomaterial was decorated by a number of mono-luminophore. Here, we report a novel ECL nanomaterial assembled by dual luminophores perylenetetracarboxylic acid (PTCA) and carbon quantum dots (CQDs). In the ECL nanomaterial, graphene was chosen as nanocarrier. Significant ECL intensity increases are seen in the ECL nanomaterial, which was interpreted with the proposed synergistic promotion ECL meachanism of PTCA and CQDs. Furthermore, this ECL nanomaterial was used to label secondary antibody and fabricate a sandwiched carcinoembryonic antigen (CEA) immunosensor. The CEA immunosensor exhibits high sensitivity and the linear semilogarithmical range was from 0.001fgmL-1 to 1ngmL-1 with low detection limit 0.00026fgmL-1. And the CEA immunosensor is also suitable for various cancers' sample detection providing potential specific applications in diagnostics.

A novel sandwiched electrochemiluminescence immunosensor for the detection of carcinoembryonic antigen based on carbon quantum dots and signal amplification.

In this study, a novel sandwiched electrochemiluminescence (ECL) immunosensor for the detection of carcinoembryonic antigen (CEA) was developed. The nanocomposite of polydopamine and Ag nanoparticles (PDA-AgNPs) was prepared by the redox reaction between Ag+ and dopamine. This nanocomposite not only provided an effective matrix for the immobilization of primary antibody (Ab1) but also enhanced the conductivity of the electrode. Carbon quantum dots (CQDs) were immobilized on the poly(ethylenimine) functionalized graphene oxide (PEI-GO) through amido-bond. Then Au nanoparticles were decorated on the CQDs modified PEI-GO matrix, and the resulted complex AuNPs/CQDs-PEI-GO was introduced to link secondary antibody (Ab2). The CQDs can be connected to the electrode surface through the combination of CEA with Ab1 and Ab2, and then the amplified electrochemiluminescence signal of CQDs was obtained with the synergistic effect of AgNPs, polydopamine, AuNPs and PEI-GO. Under the optimal conditions, the ECL intensity was proportional to the logarithm value of CEA concentration in the linear range from 5pgmL-1 to 500ngmL-1 with a detection limit of 1.67pgmL-1 for CEA detection. The immunosensor was applied for the CEA detection in real samples with satisfactory results. The proposed ECL immunosensor showed good performance with high sensitivity, specificity, reproducibility, stability and will be potential in clinical detection.

Electrochemical performance of 8-hydroxy-2'-deoxyguanosine and its detection at poly(3-methylthiophene) modified glassy carbon electrode.

8-Hydroxy-2'-deoxyguanosine (8-OH-dG) has attracted enormous attention in recent years because it has been acknowledged as a typical biomarker of oxidative DNA damage. In this paper, the electrochemical performance of 8-OH-dG at the poly(3-methylthiophene) (P3MT) modified glassy carbon electrode (GCE) was investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The conducting polymer P3MT can effectively decrease the oxidation peak potential of 8-OH-dG and greatly enhance its peak current. In 0.1 M pH 7.0 phosphate buffer solution (PBS), the anodic peak currents of cyclic voltammograms are linear with the 8-OH-dG concentration in two intervals, viz. 0.700-35.0 microM and 35.0-70.0 microM, with the correlative coefficients of 0.9992 and 0.9995, respectively. The detection limit of 8-OH-dG can be estimated to be 0.100 microM (S/N=3). This modified electrode can be used to detect the amount of 8-OH-dG in human urine. Furthermore, the effects of scan rate, pH, and interference of uric acid (UA) for the voltammetric behavior and detection of 8-OH-dG are also discussed. This proposed modified electrode also shows excellent reproducibility and stability that makes it an ideal candidate for amperometric detection of 8-OH-dG in flow injection analysis (FIA) and high performance liquid chromatography (HPLC).

Highly selective and sensitive determination of dopamine using a Nafion/carbon nanotubes coated poly(3-methylthiophene) modified electrode.

A poly(3-methylthiophene) modified glassy carbon electrode coated with Nafion/single-walled carbon nanotubes film was fabricated and used for highly selective and sensitive determination of dopamine. The hybrid film surface of the modified electrode was characterized by scanning electrochemical microscopy (SECM) and the results indicated that the carbon nanotubes were dispersed uniformly on the conductive polymer. The experimental results suggest that the hybrid film modified electrode combining the advantages of poly(3-methylthiophene), carbon nanotubes with Nafion exhibits dramatic electrocatalytic effect on the oxidation of dopamine (DA) and results in a marked enhancement of the current response. In 0.1M phosphate buffer solution (PBS) of pH 7.0, the differential pulse voltammetric (DPV) peak heights are linear with DA concentration in three intervals, viz. 0.020-0.10 microM, 0.10-1.0 microM and 1.0-6.0 microM, with correlation coefficients of 0.9993, 0.9996 and 0.9993, respectively. The detection limit of 5.0 nM DA could be estimated (S/N=3). Moreover, the interferences of ascorbic acid (AA) and uric acid (UC) are effectively diminished. This hybrid film modified electrode can be applied to the determination of DA contents in dopamine hydrochloride injection and human serum. These attractive features provide a potential application for either in vitro measurement of DA in the presence of excess AA and UA or as detectors in flow injection analysis (FIA) and high performance liquid chromatography (HPLC).

Linear and star-shaped polynuclear Ru(II) complexes of 2-(2'-pyridyl)benzimidazolyl derivatives: syntheses, photophysical properties and red light-emitting devices.

Two new star-shaped ligands with a 1,3,5-triphenylbenzene core, tmpb (1,3,5-tris[p-2-(2'-pyridyl)benzimidazolylphenyl]benzene), and a 2,4,6-tris(p-biphenyl)-1,3,5-triazine core, tmbt (2,4,6-tris[p-2-(2'-pyridyl)benzimidazolylbiphenyl]-1,3,5-triazine), have been synthesized. Their corresponding trinuclear Ru(II) complexes [Ru3(tmpb)(bpy)6](PF6)6 (3) and [Ru3(tmpt)(bpy)6](PF6)6 (4) have been obtained. Two dinuclear linear Ru(II) complexes with previously reported ligands bmb (1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene) and bmbp (4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl) and formulae [Ru2(bmb)(bpy)4](PF6)4 (1) and [Ru2(bmbp)(bpy)4](PF6)4 (2) have also been synthesized. Photophysical and electrochemical properties of the new compounds have been investigated. All four compounds display a characteristic metal-to-ligand-charge transfer (MLCT) absorption band and emit a red light when excited at the maximum of the MLCT band with emission maximum at 624, 629, 623 and 625 nm, respectively in neat films at ambient temperature. The emission quantum efficiency of the four complexes in neat films was determined to be 0.15, 0.17, 0.04 and 0.05, respectively. Light emitting devices based on these four compounds were fabricated by spin-casting the compound as a neat film to an ITO substrate, followed by the deposition of an aluminium metal layer. All devices emit a deep red light and the device behavior resembles that of a light emitting electrochemical cell. The EL maximum of the devices 1, 2, 3, and 4 is at 637, 657, 678, and 655 nm, respectively. All four devices have a fast response time when a sufficiently high voltage is applied. The device based on 2 is the brightest with a maximum luminance of 133 cd m(-2) at 7 V. The performance of devices based on 1, 2, and 4 is in general much more efficient than the device based on [Ru(bpy)3](PF6)2, which was fabricated and evaluated under the same experimental conditions as for the devices based on 1-4.

Phosphorescent Cu(I) complexes of 2-(2'-pyridylbenzimidazolyl)benzene: impact of phosphine ancillary ligands on electronic and photophysical properties of the Cu(I) complexes.

Four mononuclear Cu(I) complexes of 2-(2'-pyridyl)benzimidazolylbenzene (pbb) with four different ancillary phosphine ligands PPh(3), bis[2-(diphenylphosphino)phenyl]ether (DPEphos), bis(diphenylphosphino)ethane (dppe), and bis(diphenylphosphinomethyl)diphenylborate (DPPMB) have been synthesized. The crystal structures of [Cu(pbb)(PPh(3))(2)][BF(4)] (1), [Cu(pbb)(dppe)][BF(4)] (2), [Cu(pbb)(DPEphos)][BF(4)] (3), and the neutral complex [Cu(pbb)(DPPMB)] (4) were determined by single-crystal X-ray diffraction analyses. The impact of the phosphine ligands on the structures of the copper(I) complexes was examined, revealing that the most significant impact of the phosphine ligands is on the P-Cu-P bond angle. The electronic and photophysical properties of the new complexes were examined by using UV-vis, fluorescence, and phosphorescence spectroscopies and electrochemical analysis. All four complexes display a weak MLCT absorption band that varies considerably with the phosphine ligand. At ambient temperature, no emission was observed for any of the complexes in solution. However, when doped into PMMA polymer (20 wt %), at ambient temperature, all four complexes emit light with a color ranging from green to red-orange, depending on the phosphine ligand. The emission of the new copper complexes has an exceptionally long decay lifetime (>200 micros). Ab initio MO calculations established that the lowest electronic transition in the copper(I) complexes is MLCT in nature. The electronic and photophysical properties of the new mononuclear Cu(I) complexes were compared with those of the corresponding polynuclear Cu(I) complexes based on the 2-(2'-dipyridyl)benzimidazolyl derivative ligands and the previously extensively studied phenanthroline-based Cu(I) complexes.

New phosphorescent polynuclear Cu(I) compounds based on linear and star-shaped 2-(2'-pyridyl)benzimidazolyl derivatives: syntheses, structures, luminescence, and electroluminescence.

Four dinuclear and trinuclear Cu(I) complexes that contain 2-(2'-pyridyl)benzimidazolyl derivative ligands including 1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,4-bmb), 1,3-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,3-bmb), 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb), and 4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl (bmbp) have been synthesized. The formulas of these complexes are [Cu(2)(1,4-bmb)(PPh(3))(4)][BF(4)](2) (1), [Cu(2)(1,3-bmb)(PPh(3))(4)][BF(4)](2) (2), [Cu(3)(tmb)(PPh(3))(6)][BF(4)](3) (3), and [Cu(2)(bmbp)(PPh(3))(4)][BF(4)](2) (4), respectively. The crystal structures of 2-4 have been determined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distorted tetrahedral geometry. For 3, two structural isomers (syn and anti) resulted from two different orientations of the three 2-(2'-pyridyl)benzimidazolyl chelating units were observed in the crystal lattice. Variable-temperature (1)H NMR experiments established the presence of syn and anti isomers for 1-3 in solution which interconvert at ambient temperature. Complexes 1-4 have a weak MLCT absorption band in the 350-450 nm region and display a yellow-orange emission when irradiated by UV light. One unexpected finding is that the yellow-orange emission of complexes 1-4 has a very long decay lifetime (approximately 200 micros) at 77 K. An electroluminescent (EL) device using 4 as the emitter and PVK as the host was fabricated. However, the long decay lifetime of the copper complexes may limit their applications as phosphorescent emitters in EL devices.

Blue luminescent 2-(2'-pyridyl)benzimidazole derivative ligands and their orange luminescent mononuclear and polynuclear organoplatinum(II) complexes.

Five new 2-(2'-pyridyl)benzimidazole derivative ligands, 1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,4-bmb), 4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl (bmbp), 1-bromo-4-[2-(2'-pyridyl)benzimidazolyl]benzene (Brmb), 1,3-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,3-bmb), and 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb), have been synthesized by Ullmann condensation methods. The corresponding mononuclear and polynuclear PtII complexes, Pt2(1,4-bmb)Ph4 (1), Pt2(bmbp)Ph4 (2), Pt(Brmb)Ph2 (3), Pt2(1,3-bmb)Ph4 (4), and Pt3(tmb)Ph6 (5), have been obtained by the reaction of the appropriate ligand with [PtPh2(SMe2)]n. The structures of the free ligands 1,4-bmb, bmbp, and tmb, as well as the complexes 1-3, were determined by single-crystal X-ray diffraction. All ligands display fluorescent emissions in the purple/blue region of the spectrum at ambient temperature and phosphorescent emissions in the blue/green region at 77 K, which are attributable to ligand-centered pi --> pi* transition. No ligand-based emission was observed for the PtII complexes 1-5. All PtII complexes display orange/red emissions at 77 K in a frozen solution or in the solid state, attributable to metal-to-ligand charge transfers (MLCT). Variable-temperature 1H NMR experiments establish that complexes 1, 4, and 5 exist in isomeric forms in solution at ambient temperature due to the hindered rotation of the square PtC2N2 planes in the complexes.

Organoboron compounds with an 8-hydroxyquinolato chelate and its derivatives: substituent effects on structures and luminescence.

Four new luminescent organoboron complexes have been synthesized and fully characterized. These compounds are four-coordinate boron chelated by either 8-hydroxyquinolato (q) or functionalized 8-hydroxylquinolato ligands, including BPh2(5-(1-naphthyl)-q) (1), BPh2(5-(2-benzothienyl)-q) (2), B(2-benzothienyl)2q (3), and B(2-benzothienyl)2(2-Me-q) (4). All four compounds have a tetrahedral geometry as established by X-ray diffraction analyses. In solution, compounds 1-4 have an emission maximum at 534, 565, 501, and 496 nm, respectively, at room temperature. They emit similar colors in the solid states without red shifts of the emission band due to the lack of significant intermolecular interactions in the crystal lattices. The substituent group at C5 or C2 position of the 8-hydroxyquinolato ligand has been observed to have a significant impact on the emission energy and the emission quantum efficiency of the boron complexes. Molecular orbital calculations (Gaussian 98) showed that the electronic transition of 1 and 2 is a pi-pi* transition centered on the functionalized 8-hydroxyquinolato group and the electronic transition of 3 and 4 is an interligand charge transfer from the 2-benzothienyl ligand to the hydroxyquinolato ring. A double-layer electroluminescent device using 3 as the emitter has been fabricated, which produced a broad emission band with a significant contribution of exciplex emission.

Cu(I) and Zn(II) complexes of 7-azaindole-containing scorpionates: structures, luminescence and fluxionality.

A new scorpionate borate ligand K[HB(7-azain)3](1, 7-azain = 7-azaindolyl) has been obtained from the reaction of KBH4 with excess 7-azaindole. The scorpionate ligand 1 was found to be able to form complexes with Zn(II) and Cu(I) ions. Complex 2 with the formula [BH(7-azain)3](ZnCl) has been obtained from the reaction of ZnCl2 with 1. Complex 3 with the formula [BH(7-azain)3][Cu(PPh3)] has been obtained from the reaction of [Cu(PPh3)2(CH3CN)2][BF4] with . The crystal structures of 1-3 have been determined by single-crystal X-ray diffraction analyses which revealed that has a dimeric structure linked together by two K+ ions, 2 has a symmetric tripodal structure with all three 7-azaindolyl groups being coordinated to the Zn(II) center, and 3 has an asymmetric structure with two of the 7-azaindolyl groups being coordinated to the Cu(I) center and the third 7-azaindolyl group uncoordinated. Variable temperature 1H NMR experiments established that 3 is highly dynamic in solution involving a rapid exchange between the coordinated and the non-coordinated 7-azaindolyl groups. All three compounds display blue emission in the solid state at ambient temperature. However, in solution at ambient temperature, compounds 1 and 2 display bright blue emission while compound 3 has no emission at all. At 77 K, solutions of all three compounds display blue-green phosphorescent emission with a long decay lifetime (> 2 ms).

7-Azaindolyl- and 2,2'-dipyridylamino-functionalized molecular stars with sixfold symmetry: self-assembly, luminescence, and coordination compounds.

Two novel star molecules functionalized with 7-azaindolyl and 2,2'-dipyridylamino groups have been synthesized. Both molecules possess a sixfold rotation symmetry. Molecule L1 is based on the hexaphenylbenzene core with the formula of hexa[p-(7-azaindolyl)phenyl]benzene, while molecule L2 is based on the hexakis(biphenyl)benzene core with the formula of hexa[p-(2,2'-dipyridylamino)biphenyl]benzene. Both compounds have been characterized by single-crystal X-ray diffraction analyses. Molecule L1 forms extended two-dimensional layered structure, while L2 forms interpenetrating columnar stacks in the solid state, as revealed by X-ray diffraction analyses. Nanowire structures based on columnar stacks through self-assembly of L2 on a graphite surface were revealed by an STM study. Molecules L1 and L2 are capable of binding to metal ions, resulting in unusual structural motifs. Two Ag(I) complexes with the formulae of [(AgNO(3))(2)(L1)] (1) and [(AgNO(3))(3)(L1)] (2) were isolated from the reactions of AgNO(3) with L1. Compound 1 displays extended intermolecular pi-pi stacking interactions that are responsible for its extended two-dimensional structure in the crystal lattice. Complex 2 has a "bowl" shape and forms polar stacks in the crystal lattice. A Cu(II) complex with the formula of [{Cu(NO(3))(2)}(6)(L 2)] (3) was isolated from the reaction of Cu(NO(3))(2) with compound L2. The six Cu(II) ions in 3 are chelated by the 2,2'-dipyridylamino groups of the star ligand L2. Intermolecular Cu-O (nitrate) bonds lead to the formation of an extended two-dimensional coordination network of 3. Both L1 and L2 are blue luminescent. Their interactions with Ag(I) or Cu(II) cause drastic quenching of emission. In addition, the luminescence of L1 and L2 is sensitive to the presence of protons, which cause a reduction of emission intensity and a red shift of the emission energy.

Palladium(II) complexes of bowls, pinwheels, cages, and N,C,N-pincers of starburst ligands 1,3,5-Tris(di-2-pyridylamino)benzene and 2,4,6-Tris(di-2-pyridylamino)-1,3,5-triazene.

The reactions of Pd(II) ions with starburst ligands 1,3,5-tris(di-2-pyridylamino)benzene (tdab) and 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazene (tdat) have been investigated. Complexes with the Pd:tdab (or tdat) ratio being 1:1 and 3:1 have been isolated and characterized. The structures of five new Pd(II) complexes containing the starburst ligands have been determined by X-ray diffraction analyses, which include chelate compounds [PdCl(2)(tdab)], 1, [(PdCl(2))(3)(tdab)], 2, [(Pd(OAc)(2))(3)(tdab)], 4, and [(Pd(OAc)(2))(3)(tdat)], 5, and a cyclometalated compound [Pd(OAc)(NCN-tdab)], 3. The Pd(II) ion in the 1:1 compound 1 is chelated by two pyridyl groups. Similarly, each Pd(II) center in the 3:1 compounds 2, 4, and 5 is chelated by two pyridyl groups. However, these three compounds display distinct structural features: 2 adopts a "bowl-shaped" structure, 4 has a "pinwheel"-like structure, and 5 has a "up-and-down" structure. Compounds 4 and 5 were examined in solution by variable-temperature (1)H NMR, which revealed that both compounds retain the "pinwheel" and the "up-and-down" structure, respectively. The observed structural preference by 4 and 5 is attributed to both electronic and steric factors.

Three-coordinate organoboron compounds BAr2R (Ar = mesityl, R = 7-azaindolyl- or 2,2'-dipyridylamino-functionalized aryl or thienyl) for electroluminescent devices and supramolecular assembly.

Eight novel three-coordinate boron compounds with the general formula BAr(2)L, in which Ar is mesityl and L is a 7-azaindolyl- or a 2,2'-dipyridylamino-functionalized aryl or thienyl ligand, have been synthesized by Suzuki coupling, Ullmann condensation methods, or simple substitution reactions (L = p-(2,2'-dipyridylamino)phenyl, 1; p-(2,2'-dipyridylamino)biphenyl, 2; p-(7-azaindolyl)phenyl, 3; p-(7-azaindolyl)biphenyl, 4; 3,5-bis(2,2'-dipyridylamino)phenyl, 5; 3,5-bis(7-azaindolyl)phenyl, 6; p-[3,5-bis(2,2'-dipyridylamino)phenyl]phenyl, 7; 5-[p-(2,2'-dipyridylamino)phenyl]-2-thienyl, 8). The structures of 1, 3, and 5-7 have been determined by X-ray diffraction analyses. These new boron compounds are bright blue emitters. Electroluminescent devices using compound 2 or 8 as the emitter and the electron-transport layer have been successfully fabricated. Molecular orbital calculations (Gaussian 98) have established that the blue emission of compounds 1-8 originates from charge transfer between the pi orbital of the ligand L and the p(pi) orbital of the boron center. The ability of these boron compounds to bind to metal centers to form supramolecular assemblies was demonstrated by treatment of compound 2 with Zn(O(2)CCF(3))(2), which generated a 1:1 chelate complex [2.Zn(O(2)CCF(3))(2)] (10), and also by treatment of compound 4 with AgNO(3), yielding a 2:1 coordination compound [(4)(2).Ag(NO(3))] (11). In the solid state, compounds 10 and 11 form interesting head-to-head and tail-to-tail extended structures that host solvent molecules such as benzene.