Crystal structure and luminescent properties of the complex [Eu(III)(TFPB)(3)bpy]

The crystal structure of Eu(TFPB)(3)bpy [TFPB: 4,4,4-trifluoro-1-phenyl-1,3-butanedione, bpy: 2,2'-bipyridyl] has been determined by single crystal X-ray diffraction and the coordination geometry of Eu atom is a square antiprism. The complex can give the characteristic luminescence of Eu3+ upon UV excitation.

Structural selectivity of aromatic diamidines

Competition dialysis was used to study the interactions of 13 substituted aromatic diamidine compounds with 13 nucleic acid structures and sequences. The results show a striking selectivity of these compounds for the triplex structure poly dA:(poly dT)(2), a novel aspect of their interaction with nucleic acids not previously described. The triplex selectivity of selected compounds was confirmed by thermal denaturation studies. Triplex selectivity was found to be modulated by the location of amidine substiuents on the core phenyl-furan-phenyl ring scaffold. Molecular models were constructed to rationalize the triplex selectivity of DB359, the most selective compound in the series. Its triplex selectivity was found to arise from optimal ring stacking on base triplets, along with proper positioning of its amidine substituents to occupy the minor and the major-minor grooves of the triplex. New insights into the molecular recognition of nucleic acid structures emerged from these studies, adding to the list of available design principles for selectively targeting DNA and RNA.

A modified Wittig polycondensation - to high-trans- and high-molecular weight PPVs

A modified Wittig polycondensation was developed by replacing the bulky -PPh3 with -PBu3 ylide. Our studies suggested that the modified polymerization dramatically enhances trans-selectivity due to the decreased 1.3-steric interaction between butyl chain and triphenylamine group, together with the 1,2-steric interaction between the phenyl ring of the ylide and the triphenylamine group of the aldehyde. Moreover, the method also enhances high-molecular weight products by increasing the activity and solubility of the ylide.

Crosslinkable poly (p-phenylenevinylene) derivative

To simplify the fabrication of multilayer light-emitting diodes, we prepared a p-phenylenevinylene-based polymer capped with crosslinkable styrene through a Wittig reaction. Insoluble poly(p-phenylenevinylene) derivative (PPVD) films were prepared by a thermal treatment. The photoluminescence and ultraviolet-visible (UV-vis) absorbance of crosslinked films and noncrosslinked films were studied. We also studied the solvent resistance of crosslinked PPV films with UV-vis absorption spectra and atomic force microscopy. Double-layer devices using crosslinked PPVD as an emitting layer, 2-(4-tert-butylphenyl)-5-phenyl-1,3,4-oxadiazole (PBD) in poly(methyl methacrylate) as an electron-transporting layer, and calcium as a cathode were fabricated. A maximum luminance efficiency of 0.70 cd/A and a maximum brightness of 740 cd/m(2) at 16 V were demonstrated. A 12-fold improvement in the luminance efficiency with respect to that of single-layer devices was realized.

Phenylthiolate as a sigma- and pi-donor ligand: synthesis of a 3-D organometallic coordination polymer [K2Fe(SPh)(4)](n)

The synthesis and crystal structure of the first mixed-metal organometallic polymer network containing phenylthiolato ligands, [K2Fe(SPh)(4)](n), are investigated. The simple phenyl-thiolate acts as a sigma- and pi-donor ligand to give a 3-D potassium iron coordination polymer with both metal-carbon and metal-sulfur coordination interactions.

Self-immobilized metallocene catalysts bearing an allyl group for ethylene polymerization, X-ray crystal structure of [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2

A series of ansa-metallocene complexes with an allyl substituted silane bridge [(CH =CHCH2)CH3Si(C5H4)(2)]TiCl2 (1), [(CH2=CHCH2)CH3Si(C9H6)(2)]MCl2 [M = Ti (2), Zr (3), Hf (4)] and [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2 (6) have been synthesized and characterized. The molecular structure of 6 has been determined by X-ray crystallographic analysis. Complexes 1-4, 6 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization in the presence of MMAO. The results showed that the self-immobilized catalysts 1-4, 6 kept high ethylene polymerization activities of ca. 10(6) g PE mol(-1) M h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene.

The antioxidative effect of icariin in human erythrocytes against free-radical-induced haemolysis

Icariin (2-(4'-methoxyl phenyl)-3-rhamnosido-5-hydroxyl-7-glucosido-8-(3'-methyl-2-butyleny"chromanone) is the major component in Herba Epimedii used in traditional Chinese medicine for the treatment of atherosclerosis. This work focuses on the antioxidative effect of icariin on freeradical-induced haemolysis of human erythrocytes, in which the initial free radical derives from the decomposition of 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) at physiological temperature. To reveal the structure-activity relationship of icariin, the antioxidant effects of two structural analogues of icariin, acacetin (2-(4'-methoxylphenyl)-5,7-dihydroxylchromone) and norwogonin (2-phenyl-5,7,8-trihydroxylchromone), on the same experimental system were examined as well. It was found that all these chromone derivatives (Chm-OHs) dose-dependently protected human erythrocytes against free-radical-induced haemolysis. The order of antioxidative activity was nonvogoni-n > acacetin > icariin by the analysis of the relationship between the concentration of Chm-OHs and the prolongation percentage of the lag time of haemolysis (PP%). It was also proved that the phenyl hydroxyl group attached to the chromone ring at 7-position cannot trap the free radical- On the contrary, phenyl hydroxyl groups at the 5- and 8-position in nonvogonin made it a significant antioxidant in AAPH-induced haemolysis.

White electrolumineseence from a single-polymer system with simultaneous two-color emission: Polyfluorene as the blue host and a 2,1,3-benzothiadiazole derivative as the orange dopant on the main chain

New single-polymer electroluminescent systems containing two individual emission species - polyfluorenes as a blue host and 2,1,3-benzothiadiazole derivative units as an orange dopant on the main chain - have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue(lambda(max) = 421 nm/445 nm) and orange emission (lambda(max) = 564 nm)from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light-emitting diodes (PLEDs) based on the single-polymer systems has been investigated. The introduction of the highly efficient 4,7-bis(4-(N-phenyl-N-(4-methylphenyl)amino)phenyl)-2,1,3-benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single-layer device fabricated in air (indium tin oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure-white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m(-2), luminance efficiency of 7.30 cd A(-1), and power efficiency of 3.34 lm W-1 can be obtained.

Highly efficient electroluminescence from green-light-emitting electrochemical cells based on Cu-I complexes

The complexes [Cu(dnpb)(DPEphos)](+)(X-) (dnpb and DPEphos are 2,9-di-n-butyl-1,10-phenanthroline and bis[2-(diphenyl-phosphino)phenyl]ether, respectively, and X- is BF4-, ClO4-, or PF6-) can form high quality films with photoluminescence quantum yields of up to 71 +/- 7%. Their electroluminescent properties are studied using the device-structure indium tin oxide (ITO)/complex/metal cathiode. The devices emit green light efficiently, with an emission maximum of 523 nm, and work in the mode of light-emitting electrochemical cells. The response time of the devices greatly depends on the driving voltage, the counterions, and the thickness of the complex film. After pre-biasing at 25 V for 40 s, the devices turn on instantly, with a turn-on voltage of ca. 2.9 V. A current efficiency of 56 cd A(-1) and an external quantum efficiency of 16% are realised with Al as the cathode. Using a low-work-function metal as the cathode can significantly enhance the brightness of the device almost without affecting the turn-on voltage and current efficiency. With a Ca cathode, a brightness of 150 cd m(-2) at 6 V and 4100 cd m(-2) at 25 V is demonstrated. The electroluminescent performance of these types of complexes is among the best so far for transition metal complexes with counterions.

Specific determination of As(V) by an acid phosphatase-polyphenol oxidase biosensor

An original amperometric biosensor based on the simultaneous entrapment of acid phosphatase (AcP) and polyphenol oxidase (PPO) into anionic clays (layered double hydroxides) was developed for the specific detection of As(V). The functioning principle of the bienzyme electrode consisted of the successive hydrolysis of phenyl phosphate into phenol by AcP, followed by the oxidation of phenol into o-quinone by PPO. The phenyl phosphate concentration was, thus, monitored by potentiostating the biosensor at -0.2 V vs Ag/AgCl to detect amperometrically the generated quinone. The detection of As(V) was based on its inhibitory effect on AcP activity toward the hydrolysis of phenyl phosphate into phenol. The As(V) can be specifically determined in pH 6.0 acetate buffer without any interferences of As(III) or phosphate, the detection limit being 2 nM or 0.15 ppb after an incubation step for 20 min.

Structure and identity of 4,4 '-thiobisbenzenethiol self-assembled monolayers

Self-assembled monolayers (SAMs) of 4,4'-thiobisbenzenethiol (TBBT) can be formed on Au surface spontaneously. The structural characteristics and adsorption behavior of TBBT SAMs on Au have been investigated by surface enhanced Raman scattering (SERS), electrochemical cyclic voltammetry (CV), ac impedance spectroscopy (EIS), and atomic force microscopy (AFM). It is demonstrated that TBBT adsorbed on Au by losing a H atom, forming one Au-S bond, and the other mercapto group is free at the surface of the monolayer owing to the presence of the nu(S-H) at 2513 cm(-1) and the delta(C-S-H) at 910 cm(-1) in SERS. The enhancement of the vibration of C-S (1064 cm(-1)), the aromatic C-H vibration (3044 cm(-1)), and the absence of the vibration of S-S illustrate TBBT adsorbed on Au forming a monolayer with one benzene ring tilted with respect to the Au surface. The interpretation of the observed frequencies is aided by ab initio molecular orbital (MO) calculations at the HF/6-31G* level of theory. Electrochemical CV and EIS indicate TBBT monolayers can passivate the Au effectively for its low ratio of pinhole defects (theta = 99.6%). AFM studies give details about the surface morphology. The applications of TBBT SAMs have been extensively investigated by exposure of Cu2+ ion to TBBT SAMs on Au and covalent adsorption of metal nanoparticles.

Green electroluminescent polyfluorenes containing 1,8-naphthalimide moieties as color tuner

A series of copolymers (CNPFs) containing low-band-gap 1,8-naphthalimide moieties as color tuner was prepared by a Yamamoto coupling reaction of 2,7-dibromo-9,9-dioctylfluorene (DBF) and different amount of 4-(3,6-dibromocarbazol-9-yl)-N-(4'-tert-butyl-phenyl)-1,8-naphthalimide (Br-CN) (0.05-1 mol% feed ratio). The light emitting properties of the resulting copolymers showed a heavy dependence on the feed ratio. In photoluminescence (PL) studies, an efficient color tuning through the Forster energy transfer mechanism was revealed from blue to green as the increase of Br-CN content, while in electroluminescence (EL) studies, the color tuning was found to go through a charge trapping mechanism. It was found that by introduction of a very small amount of Br-CN (0.1-0.5 mol%) into polyfluorene, the emission color can be tuned from blue to pure green with Commission International de l'Echairage (CIE) coordinates being (0.21, 0.42) and (0.21, 0.48). A green emitting EL single-layer device based on CNPF containing 0.1 mol% of Br-CN showed good performances with a low turn-on voltage of 4.2 V, a brightness of 9104 cd/m(2), the maximum luminous efficiency of 2.74 cd/A and the maximum power efficiency of 1.51 lm/W.

Negative differential resistance and multilevel memory effects in organic devices

Negative differential resistance ( NDR) and multilevel memory effects were obtained in organic devices consisting of an anthracene derivative, 9,10-bis-{ 9,9-di-[ 4-(phenyl-p-tolyl-amino)-phenyl]-9H-fluoren-2-yl}-anthracene ( DAFA), sandwiched between Ag and ITO electrodes. The application of a negative bias voltage leads to negative differential resistance in current-voltage characteristics and different negative voltages produce different conductance currents, resulting in the multilevel memory capability of the devices. The NDR property has been attributed to charge trapping at the DAFA/Ag interface. This opens up a wide range of application possibilities of such organic-based NDR devices in memory and logic circuits.

Synthesis, crystal structure, spectroscopy and electroluminescence of zinc(II) complexes containing bidentate 2-(2-pyridyl)quinoline derivative ligands

Three bidentate ligands, 4-phenyl-2-(2-pyridyl)-quinoline (ppq), 6-(carbazol-9-yl)-4-phenyl-2-(2-pyridyl)-quinoline (cpq) and 6-diphenylamino-4-phenyl-2-(2-pyridyl)-quinoline (dpq) and their zinc(II) complexes, have been designed and synthesized. The crystal structure of [Zn(ppq)(2)Cl]PF6 shows that the central zinc atom is coordinated with one chloride and four nitrogen atoms from two ligands. The introduction of an electron-donating substituent such as carbazole or an aromatic amine group at the 6-position of the quinoline moiety can generate colored tunable Zn complexes, and the photoluminescence (PL) wavelength was modulated from 418 nm for [Zn(ppq)(2)Cl]PF6 to 591 nm for [Zn(cpq)(2)Cl]PF6 and 638 nm for [Zn(dpq)(2)Cl]PF6 in CH2Cl2 solution. The electroluminescence spectrum of [Zn(dpq)(2)Cl]PF6 exhibits pure red light emission with the Commission Internationale de L'Eclairage (CIE) coordinates (0.63, 0.36) and a maximum at 648 nm.

2-[2-(Phenylsulfonyl)ethyl]isoindoline-1,3-dione

In the title compound, C16H13NO4S, the phthalimide ring system makes a dihedral angle of 56.7 (1)degrees with the phenyl ring.