Phosphorescent platinum(II) complexes derived from multifunctional chromophores: synthesis, structures, photophysics, and electroluminescence

The synthesis and structural, photophysical, electrochemical, and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are reported in which the hole-transporting triarylamine, electron-transporting oxadiazole, and electroluminescent metal components are integrated into a single molecule. These neutral metal chelates display good thermal stability (>250 degrees C under N2) and morphological stability. All of them exhibit intense ligand-centered fluorescence and phosphorescence in fluid solutions at room temperature, but the emission spectra become largely dominated by triplet emission bands in CH2Cl2 glass at 77 K. Substituents with different electronic properties were introduced into the bipolar cyclometalating ligands to fine-tune the absorption and emissive characteristics of the compounds, and the results were correlated with theoretical calculations using density functional theory. A comparison of the photophysics and electrochemistry of our multifunctional systems to those only derived from each of the constituent components was also made and discussed. These Pt complexes can be vacuum-sublimed and applied as emissive dopants for the fabrication of vapor-deposited electrophosphorescent organic light-emitting devices (OLEDs), which generally exhibit good device performance with efficiencies up to 3.6%, 11.0 cd A-1, and 5.8 lm W-1. While the electroluminescence energy resembles that recorded in fluid solutions for these Pt emitters, these monochromatic OLEDs can emit tunable colors by varying the aryl ring substituents and the level of doping. Saliently, single dopant white-light electroluminescence, triggered by the simultaneous fluorescence/phosphorescence emission of the metal complexes and a variation of applied driving voltages, has also been realized based on some of these multifunctional complexes with peak electrophosphorescence efficiencies of 6.8 cd A-1 and 2.6%.     

Nonlinear polarization rotation in a dispersion-flattened photonic-crystal fiber for ultrawideband (>100 nm) all-optical wavelength conversion of 10 Gbit/s nonreturn-to-zero signals

We study the conversion bandwidth of the cross-polarization-modulation (XPoIM)-based wavelength conversion scheme with a dispersion-flattened highly nonlinear photonic-crystal fiber for signals with a nonreturn-to-zero (NRZ) modulation format. Both theoretical and experimental results show that the conversion bandwidth can be extended to cover a very wide band, including S-, C-, and L-bands for 10 Gbit/s NRZ signals (a total bandwidth of 120 nm is experimentally demonstrated). We also study the theoretical bandwidth limit for 40 Gbit/s NRZ signals. A significant extension of the conversion bandwidth using the XPoIM approach compared with the four-wave mixing approach previously reported is demonstrated.     

Surface wave assisted self-assembly of multidomain magnetic structures

An ensemble of magnetic microparticles at the liquid surface displays novel snakelike self-assembled structures induced by an alternating magnetic field. We demonstrate that these structures are directly related to surface waves in the liquid generated by the collective response of magnetic microparticles to the alternating magnetic field. The segments of the "snake" exhibit long-range antiferromagnetic ordering, while each segment is composed of ferromagnetically aligned chains of microparticles. The structures exhibit magnetic hysteretic behavior with respect to an external in-plane magnetic field and logarithmic relaxation of the remanent magnetic moment.     

Dimension-splitting data points redistribution for meshless approximation

To better approximate nearly singular functions with meshless methods, we propose a data points redistribution method extended from the well-known one-dimensional equidistribution principle. With properly distributed data points, nearly singular functions can be well approximated by linear combinations of global radial basis functions. The proposed method is coupled with an adaptive trial subspace selection algorithm in order to reduce computational cost. In our numerical examples, clear exponential convergence (with respect to the numbers of data points) can be observed.     

Screening of drugs in equine plasma using automated on-line solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry

A rapid liquid chromatography–tandem mass spectrometry (LC–MS–MS) method was developed for the simultaneous screening of 19 drugs of different classes in equine plasma using automated on-line solid-phase extraction (SPE) coupled with a triple quadrupole mass spectrometer. Plasma samples were first protein precipitated using acetonitrile. After centrifugation, the supernatant was directly injected into the on-line SPE system and analysed by a triple quadrupole LC–MS–MS in positive electrospray ionisation (+ESI) mode with selected reaction monitoring (SRM) scan function. On-line extraction and chromatographic separation of the targeted drugs were performed using respectively a polymeric extraction column (2 cm L × 2.1 mm ID, 25 μm particle size) and a reversed-phase C18 LC column (3 cm L × 2.1 mm ID, 3 μm particle size) with gradient elution to provide fast analysis time. The overall instrument turnaround time was 9.5 min, inclusive of post-run and equilibration time. Plasma samples fortified with 19 targeted drugs including narcotic analgesics, local anaesthetics, antipsychotics, bronchodilators, mucolytics, corticosteroids, sedative and tranquillisers at sub-parts per billion (ppb) to low parts per trillion (ppt) levels could be consistently detected. No significant matrix interference was observed at the expected retention times of the targeted ion transitions. Over 70% of the drugs studied gave detection limits at or below 100 pg/mL, with some detection limits reaching down to 19 pg/mL. The method had been validated for extraction recovery, precision and sensitivity, and a blockage study had also been carried out. This method is used regularly in the authors’ laboratory to screen for the presence of targeted drugs in pre-race plasma samples from racehorses.     

Dynamic interfacial effect of electroosmotic slip flow with a moving capillary front in hydrophobic circular microchannels

Miniaturization of chemical analysis using microfabrication is an emerging technology. The use of polymeric materials as opposed to conventional glass substrate is also a promising alternative. As most polymeric materials are hydrophobic relative to glass, we describe here the implication for the loading process of electroosmotic flow (EOF) when a three-phase (solid-liquid-vapor) contact line exists. The presence of these interfaces can result in a large Laplace pressure that resists EOF and hence hinders its flow performance. This effect depends on the phenomenological contact angle at the solid-liquid interface. In our model for EOF, we considered simultaneously the presence of an electric double layer, liquid slips via a weaker solid-liquid interaction and Laplace pressure across a liquid-vapor interface.     

Tethered silyl complexes from nucleophilic substitution reactions at the Si-Cl bond of the chloro(diphenyl)silyl ligand in Ru(SiClPh2)(κ-S2CNMe2)(CO)(PPh3)2

Crystal structure determination of RuH(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (1) confirms that the triphenylphosphine ligands are arranged mutually trans. 1 reacts readily with HSiClPh₂ to eliminate H₂ and produce the six-coordinate silyl complex, Ru(SiClPh₂)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (2). Crystal structure determination of 2 reveals the same geometrical arrangement of ligands as in 1 with the silyl ligand replacing the hydride ligand. The chloride bound to silicon in 2 is replaced through reactions with 2-hydroxypyridine, 2-aminopyridine, and thallium acetate, producing, respectively, the mono-PPh₃ complexes, Ru(κ²(Si,N)-SiPh₂OC₅H₄N)(κ²-S₂CNMe₂)(CO)(PPh₃) (3), Ru(κ²(Si,N)-SiPh₂NHC₅H₄N)(κ²-S₂CNMe₂)(CO)(PPh₃) (4), and Ru(κ²(Si,O)-SiPh₂OCMeO)(κ²-S₂CNMe₂)(CO)(PPh₃) (5). Crystal structure determinations of 3, 4, and 5 confirm that in each case there is formation of a five-membered chelate ring tethering the silyl ligand to ruthenium. In the formation of 3, 4, and 5 the Si-ligand and the two S atoms of the dimethyldithiocarbamate ligand remain meridional but the remaining triphenylphosphine ligand and the carbonyl ligand are interchanged in position leaving the donor atom of the tether trans to the CO ligand. An alternative way of considering the tethered silyl ligands in 3, 4, and 5 is as tethered, base-stabilised, silylene ligands and the structural data give some support for a contribution from this bonding model.     

One stone,three birds: one AIEgen with three colors for fast differentiation of three pathogens

Visually identifying pathogens favors rapid diagnosis at the point-of-care testing level. Here, we developed a microenvironment-sensitive aggregation-induced emission luminogen (AIEgen), namely IQ–Cm, for achieving fast discrimination of Gram-negative bacteria, Gram-positive bacteria and fungi by the naked-eye. With a twisted donor–acceptor and multi-rotor structure, IQ–Cm shows twisted intramolecular charge transfer (TICT) and AIE properties with sensitive fluorescence color response to the microenvironment of pathogens. Driven by the intrinsic structural differences of pathogens, IQ–Cm with a cationic isoquinolinium moiety and a membrane-active coumarin unit as the targeting and interacting groups selectively locates in different sites of three pathogens and gives three naked-eye discernible emission colors. Gram-negative bacteria are weak pink, Gram-positive bacteria are orange-red and fungi are bright yellow. Therefore, based on their distinctive fluorescence response, IQ–Cm can directly discriminate the three pathogens at the cell level under a fluorescence microscope. Furthermore, we demonstrated the feasibility of IQ–Cm as a visual probe for fast diagnosis of urinary tract infections, timely monitoring of hospital-acquired infection processes and fast detection of molds in the food field. This simple visualization strategy based on one single AIEgen provides a promising platform for rapid pathogen detection and point-of-care diagnosis.

A simple AIEgen with three emission colors achieves rapid identification of Gram-negative bacteria, Gram-positive bacteria and fungi.