A theoretical study of the photoelectron spectra of dichloroketene with accurate computation of ionization energies via complete basis set limit extrapolation

We calculated the equilibrium geometries and harmonic vibrational frequencies of the ground state and five cationic states of dichloroketene using (TD-)B3LYP, PBE0, and M06/M06-2X approaches. The photoelectron spectra of dichloroketene were simulated by computing Franck-Condon factors. The ionization energies were computed using the CCSD(T) approach with extrapolation to the complete basis set (CBS) limit. We propose two new CBS energy formulas (E = E_CBS + Aexp(-x) + B/(x−1) ⁿ, n = 2 or 3) and compare the performance of different CBS approaches. A new ionic state of dichloroketene belonging to the C_s point group is reported. This state is identified as the first excited state of Cl₂CCO⁺ having a double-well potential-energy curve along the CCO bending mode with a barrier height of 1.335 eV. The simulated photoelectron spectra are in agreement with the experiment. The vertical ionization energies calculated via spectral simulation are more accurate compared with those obtained at the ground-state structure. Among the CBS formulas used, the proposed ansatz with n = 2 performs best, with a mean absolute error of 0.021 and 0.012 eV for the adiabatic and vertical ionization energies, respectively.     

Tuning the In Vivo Transport of Anticancer Drugs Using Renal‐Clearable Gold Nanoparticles

Precise control of in vivo transport of anticancer drugs in normal and cancerous tissues with engineered nanoparticles is key to the future success of cancer nanomedicines in clinics. This requires a fundamental understanding of how engineered nanoparticles impact the targeting‐clearance and permeation‐retention paradoxes in the anticancer‐drug delivery. Herein, we systematically investigated how renal‐clearable gold nanoparticles (AuNPs) affect the permeation, distribution, and retention of the anticancer drug doxorubicin in both cancerous and normal tissues. Renal‐clearable AuNPs retain the advantages of the free drug, including rapid tumor targeting and high tumor vascular permeability. The renal‐clearable AuNPs also accelerated body clearance of off‐target drug via renal elimination. These results clearly indicate that diverse in vivo transport behaviors of engineered nanoparticles can be used to reconcile long‐standing paradoxes in the anticancer drug delivery.     

Structural and luminescent characteristics of non-stoichiometric ZnO films by various sputtering and annealing temperatures

ZnO thin films were prepared by reactive RF magnetron sputtering at various deposition temperatures. They were annealed in oxygen ambient at various annealing temperatures. The microstructures and photoluminescence characteristics of ZnO films were investigated. The grain size of the ZnO thin film that was deposited at room temperature (RT) after annealing exceeded that of the film that was deposited at . Excess Zn atoms were considered to be present in the ZnO film that was deposited at RT, so the film was non-stoichiometric ZnO. No visible emission of either of the ZnO films deposited at the two temperatures was observed before annealing. Following annealing at high temperature, the green emission from the ZnO film that was deposited at RT was stronger than that of the film that was deposited at . The relationship between the non-stoichiometry of the thin film and the visible emission was discussed. The luminescent centers that correspond to green emission are defects; the concentration of defects was higher in the ZnO thin film that was deposited at RT than in the film that was deposited at .     

Facile Generation of Thermally Activated Delayed Fluorescence and Fabrication of Highly Efficient Non-Doped OLEDs Based on Triazine Derivatives

A series of donor–acceptor–donor triazine-based molecules with thermally activated delayed fluorescence (TADF) properties were synthesized to obtain highly efficient blue-emitting OLEDs with non-doped emitting layers (EMLs). The targeted molecules use a triazine core as the electron acceptor, and a benzene ring as the conjugated linker with different electron donors to alternate the energy level of the HOMO to further tune the emission color. The introduction of long alkyl chains on the triazine core inhibits the unwanted intermolecular D –D/A–A-type π–π interactions, resulting in the intermolecular D–A charge transfer. The weak aggregation-caused quenching (ACQ) effect caused by the suppressed intermolecular D –D/A–A-type π–π interaction further enhances the emission. The crowded molecular structure allows the electron donor and acceptor to be nearly orthogonal, thereby reducing the energy gap between triplet and singlet excited states (ΔE_ST). As a result, blue-emitting devices with TH-2DMAC and TH-2DPAC non-doped EMLs showed satisfactory efficiencies of 12.8 % and 15.8 %, respectively, which is one of the highest external quantum efficiency (EQEs) reported for blue TADF emitters (λ_peak<475 nm), demonstrating that our tailored molecular designs are promising strategies to endow OLEDs with excellent electroluminescent performances.     

A New β-Ionone from Liriodendron tulipifera

Chemistry of Natural Compounds - A new β-ionone, litulipiferic acid (12), was isolated from the leaves of Liriodendron tulipifera (Magnoliaceae). The structure of the new β-ionone was...     

Multidimensional chromatography coupled with mass spectrometry for target-based screening

Summary The synthesis of structural analogs and the process of drug discovery have evolved dramatically through recent advances in solid-phase synthesis reagents and automated screening systems. As molecular diversity strategies emerge, the need for automated target-based selection of lead candidates becomes equally important. Multidimensional automated chromatographic techniques coupled to electrospray ionization mass spectrometry facilitate the selection process and provide maximum characterization information in a single screening run. The capture of tightly bound affinity leads by target biomolecules, followed by subsequent release and high-resolution separation with sensitive detection, significantly reduces the time required to identify and characterize lead compounds. This automated multidimensional chromatographic approach coupled with mass spectrometry, Selectronics, was used with several organic and natural libraries to demonstrate an automated target-based screening technique to select for high-affinity binders as potential lead compounds.Abbreviations ESI electrospray ionization - HPLC high-performance liquid chromatography - HTS high-throughput screening - ESI-TOF electrospray ionization time-of-flight - SAR structure-activity relationship     

Strained AlGaInP quantum wire lasers

We report on the fabrication of strained separate-confinement heterostructure AlGaInP visible laser diodes with multiple quantum wire active regions formed in situ during gas source molecular beam epitaxy. Lateral composition modulation with a period on the order of 100 å perpendicular to the growth direction occurs spontaneously during the growth of the (GaP)₂/(InP)₂ short-period superlattice active region by the strain-induced lateral-layer ordering (SILO) process. Individual laser diodes fabricated from the same wafer but emitting parallel and normal to the wire axis exhibit highly anisotropic properties, including large difference in threshold current, emission wavelength, and opposite polarizations. These effects are explained in terms of the strained quantum wire potential. The additional degree of quantum confinement in quantum wire structure reduces the threshold current density by a factor of >2.7 when compared with an otherwise identical quantum well laser.     

Potential of HILIC-MS in quantitative bioanalysis of drugs and drug metabolites

One fundamental requirement for many lead optimization processes is the need for bioanalytical support within pharmaceutical drug discovery and development. Currently, most bioanalytical methods for pharmaceutical analysis employ HPLC coupled with MS/MS. The combination of HPLC and MS/MS detection frequently offers the complete resolution of the dosed compounds from their metabolites and the endogenous interferences to avoid extra efforts for chemical separation and sample clean-up procedures resulting in higher-throughput assays for a series of new chemical entities (NCEs). Hydrophilic interaction chromatography (HILIC) has been demonstrated to be a powerful technique for the retention of polar analytes offering a difference in selectivity compared to traditional RP chromatography. This review summarizes the HILIC-MS/MS methods for the trace quantitative determinations of the drug compounds and their metabolites to support both in vitro and in vivo experiments. The challenges on performing HILIC-MS/MS assays such as matrix ionization suppression and the potential for endogenous interferences are also presented.     

New benzoyl glucosides and cytotoxic pterosin sesquiterpenes from Pteris ensiformis Burm

Three new compounds: 2R,3R-pterosin L 3-O-beta-D-glucopyranoside (1), beta-D-xylopyranosyl(1-->2)-7-O-benzoyl-beta-D-glucopyranoside (2) and 4-O-benzoyl-beta-D-xylo-pyranosyl(1-->2)-7-O-benzoyl-beta-D-glucopyranoside (3), together with nine known compounds, were isolated from the ethyl acetate extract of Pteris ensiformis. 5-[2-Hydroxyethylidene]-2(5H)-furanone (4), which had been synthesized, was isolated from natural sources for the first time. The structures of all isolated compounds were determined on the basis of mass and spectroscopic evidence. Compound 1 and pterosin B (5) show cytotoxicity against HL 60 cells (human leukemia) with the IC(50) values of 3.7 and 8.7 microg/mL, respectively.