ORCID Profile
0000-0001-8743-401X
Current Organisation
Hong Kong University of Science and Technology
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Chemical Society (ACS)
Date: 03-08-2018
Abstract: Far-red and near-infrared (NIR) fluorescent materials possessing the characteristics of strong two-photon absorption and aggregation-induced emission (AIE) as well as specific targeting capability are much-sought-after for bioimaging and therapeutic applications due to their deep penetration depth and high resolution. Herein, a series of dipolar far-red and NIR AIE luminogens with a strong push-pull effect are designed and synthesized. The obtained fluorophores display bright far-red and NIR solid-state fluorescence with a high quantum yield of up to 30%, large Stokes shifts of up to 244 nm, and large two-photon absorption cross-sections of up to 887 GM. A total of three neutral AIEgens show specific lipid droplet (LD)-targeting capability, while the one with cationic and lipophilic characteristics tends to target the mitochondria specifically. All of the molecules demonstrate good biocompatibility, high brightness, and superior photostability. They also serve as efficient two-photon fluorescence-imaging agents for the clear visualization of LDs or mitochondria in living cells and tissues with deep tissue penetration (up to 150 μm) and high contrast. These AIEgens can efficiently generate singlet oxygen upon light irradiation for the photodynamic ablation of cancer cells. All of these intriguing results prove that these far-red and NIR AIEgens are excellent candidates for the two-photon fluorescence imaging of LDs or mitochondria and organelle-targeting photodynamic cancer therapy.
Publisher: American Chemical Society (ACS)
Date: 20-01-2022
DOI: 10.1021/JACS.1C11480
Abstract: Long-persistent luminescence (LPL), also known as afterglow, is a phenomenon in which the material shows long-lasting luminescence after the cessation of the excitation source. The research of LPL continues to attract much interest due to its fundamental nature and its potential in the development of the next generation of functional materials. However, most of the current LPL materials are multicomponent inorganic systems obtained after harsh synthetic procedures and often use rare-earth metals. Recently, metal free organic long-persistent luminescence (OLPL) has gained much interest because it can bypass many of the disadvantages of inorganic systems. To date, the most successful method to generate OLPL systems is to access charge-separated states through binary donor-acceptor exciplex systems. However, it has been reported that the ratios of the binary systems affect OLPL properties, complicating the reproducibility and large-scale production of OLPL materials. Simpler OLPL systems can overcome these issues for the benefit of the development and adoption of OLPL systems. Here, we report on the rational design and synthesis of a single-component OLPL system with detectable afterglow for at least 12 min under ambient conditions. This work exemplifies an easy design principle for new OLPL materials. The investigation of the material provides valuable insights toward the generation of OLPL from a single-component system.
Publisher: Springer Science and Business Media LLC
Date: 02-10-2018
DOI: 10.1038/S42004-018-0062-7
Abstract: The quinolone decoquinate is coadministered with feed for treatment of parasites which cause coccidiosis in poultry. However, from a drug-development perspective, the biological activity is often not adequately exploited due to poor physicochemical properties. Here we convert decoquinate into N -alkyl quinolone amides that, in contrast to decoquinate, are active against the tuberculosis bacterium with MIC 90 values ranging from 1.4 to 3.64 µM, and quinoline O -carbamates active against apicomplexan parasites that cause malaria, toxoplasmosis, and neosporosis with IC 50 values of 0.32–1.5 nM for the best derivative. Uniquely for the TB-active amides, disruption of cell wall homoeostasis is identified as one target. With IC 50 values against fetal lung fibroblast cells of 40 to μM, the derivatives are selective for the pathogens. Structures of the most active derivatives are determined by NMR spectroscopy and X-ray crystallography. Analogues lacking the decyl side chain of decoquinate are inactive.
Publisher: American Chemical Society (ACS)
Date: 06-2021
DOI: 10.26434/CHEMRXIV.14703822
Abstract: Experimental and theoretical analysis demonstrated that the active intramolecular motions in the excited state of all molecules at single molecule level imparted them with more twisted structural conformations and weak emission. However, owing to the restriction of intramolecular motions in the nano/macro aggregate state, all the molecules assumed less twisted conformations with bright emission. Synergic strong and weak intermolecular interactions allowed their crystals to undergo reversible deformation, which effectively solved the problem of the brittles of organic crystals, meanwhile imparted them with excellent elastic performance.
Publisher: Wiley
Date: 19-05-2003
Publisher: Wiley
Date: 07-06-2016
Abstract: We sought to establish if methylene homologues of artemisone are biologically more active and more stable than artemisone. The analogy is drawn with the conversion of natural O- and N-glycosides into more stable C-glycosides that may possess enhanced biological activities and stabilities. Dihydroartemisinin was converted into 10β-cyano-10-deoxyartemisinin that was hydrolyzed to the α-primary amide. Reduction of the β-cyanide and the α-amide provided the respective methylamine epimers that upon treatment with inyl sulfone gave the β- and α-methylene homologues, respectively, of artemisone. Surprisingly, the compounds were less active in vitro than artemisone against P. falciparum and displayed no appreciable activity against A549, HCT116, and MCF7 tumor cell lines. This loss in activity may be rationalized in terms of one model for the mechanism of action of artemisinins, namely the cofactor model, wherein the presence of a leaving group at C10 assists in driving hydride transfer from reduced flavin cofactors to the peroxide during perturbation of intracellular redox homeostasis by artemisinins. It is noted that the carba analogue of artemether is less active in vitro than the O-glycoside parent toward P. falciparum, although extrapolation of such activity differences to other artemisinins at this stage is not possible. However, literature data coupled with the leaving group rationale suggest that artemisinins bearing an amino group attached directly to C10 are optimal compounds.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7RA11997F
Abstract: Both chiral hands of bis(salicylato)borate anion [B S (Sal) 2 ] and [B R (Sal) 2 ] are isolated and CD spectroscopy indicates they can be configurationally stable.
Publisher: American Chemical Society (ACS)
Date: 22-07-2021
DOI: 10.1021/JACS.1C05647
Abstract: Molecular motions are essential natures of matter and play important roles in their structures and properties. However, owing to the ersity and complexity of structures and behaviors, the study of motion-structure-property relationships remains a challenge, especially at all levels of structural hierarchy from molecules to macro-objects. Herein, luminogens showing aggregation-induced emission (AIE), namely, 9-(pyrimidin-2-yl)-carbazole (PyCz) and 9-(5-R-pyrimidin-2-yl)-carbazole [R = Cl (ClPyCz), Br (BrPyCz), and CN (CyPyCz)], were designed and synthesized, to decipher the dependence of materials' structures and properties on molecular motions at the molecule and aggregate levels. Experimental and theoretical analysis demonstrated that the active intramolecular motions in the excited state of all molecules at the single-molecule level endowed them with more twisted structural conformations and weak emission. However, owing to the restriction of intramolecular motions in the nano/macroaggregate state, all the molecules assumed less twisted conformations with bright emission. Unexpectedly, intermolecular motions could be activated in the macrocrystals of ClPyCz, BrPyCz, and CyPyCz through the introduction of external perturbations, and synergic strong and weak intermolecular interactions allowed their crystals to undergo reversible deformation, which effectively solved the problem of the brittleness of organic crystals, while endowing them with excellent elastic performance. Thus, the present study provided insights on the motion-structure-property relationship at each level of structural hierarchy and offered a paradigm to rationally design multifunctional AIE-based materials.
Publisher: MDPI AG
Date: 13-07-2018
DOI: 10.3390/MOLECULES23071713
Abstract: According to the precepts that C-10 amino-artemisinins display optimum biological activities for the artemisinin drug class, and that attachment of a sugar enhances specificity of drug delivery, polarity and solubility so as to attenuate toxicity, we assessed the effects of attaching sugars to N-4 of the dihydroartemisinin (DHA)-piperazine derivative prepared in one step from DHA and piperazine. N-Glycosylated DHA-piperazine derivatives were obtained according to the Kotchetkov reaction by heating the DHA-piperazine with the sugar in a polar solvent. Structure of the D-glucose derivative is secured by X-ray crystallography. The D-galactose, L-rhamnose and D-xylose derivatives displayed IC50 values of 0.58–0.87 nM against different strains of Plasmodium falciparum (Pf) and selectivity indices (SI) , on average, with respect to the mouse fibroblast WEHI-164 cell line. These activities are higher than those of the amino-artemisinin, artemisone (IC50 0.9–1.1 nM). Notably, the D-glucose, D-maltose and D-ribose derivatives were the most active against the myelogenous leukemia K562 cell line with IC50 values of 0.78–0.87 µM and SI 380 with respect to the human dermal fibroblasts (HDF). In comparison, artemisone has an IC50 of 0.26 µM, and a SI of 88 with the same cell lines. Overall, the N-glycosylated DHA-piperazine derivatives display antimalarial activities that are greatly superior to O-glycosides previously obtained from DHA.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9SC06226B
Abstract: An AIE-active ratiometric probe for the first time achieved the long-term quantification of lysosomal pH during the medaka larva's caudal fin regeneration.
Publisher: International Union of Crystallography (IUCr)
Date: 21-07-2017
DOI: 10.1107/S2053229617009718
Abstract: Spiroborate anions have potential for crystallization or resolution and chiral bis(mandelato)borate anions can be used for the efficient resolution of a erse range of racemic cations via diastereomeric salt formation. The syntheses, X-ray crystal structures and solubilities of three chiral bis(mandelato)borate salts, namely poly[[aqua-μ 3 -bis[( R )-mandelato]borato-lithium(I)] monohydrate], [Li(C 16 H 12 BO 6 )(H 2 O)] n or Li[B( R -Man) 2 ]·H 2 O, (1), ammonium bis[( R )-mandelato]borate, NH 4 + ·C 16 H 12 BO 6 − or NH 4 [B( R -Man) 2 ], (2), and tetra- n -butylammonium bis[( R )-mandelato]borate, C 16 H 36 N + ·C 16 H 12 BO 6 − or NBu 4 [B( R -Man) 2 ], (3), are reported. They all have a B S configuration and show a reasonably well-conserved anion geometry. The main conformational variation is the orientation of the two phenyl groups, supporting the idea that [B(Man) 2 ] − is a semi-rigid anion. The salts are differentially soluble in a range of solvents, meaning they could be useful as reagents for resolution via a metathesis crystallization approach.
Publisher: Wiley
Date: 23-03-2018
Abstract: Ionic fluorophores are powerful tools for the study of environmental science and bio-imaging. However, traditional ionic dyes usually require long synthetic steps and suffer from a quenching effect caused by aggregation. A water-soluble ionic aggregation-induced emission luminogen called DBTA is presented, which is readily accessed by a one-step reaction. The switchable emission manipulated by hydrogen bonding provided solid evidence for the restriction of intramolecular motions as the mechanism of aggregation-induced emission. DBTA can not only differentiate solvents with different H-bond donor acidities but also capable of wash-free imaging in living HeLa cells and fish larva.
Publisher: Wiley
Date: 12-1997
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8SC05805A
Abstract: Facile synthesis and bio-applications of a series of AIEgens with widely tunable emissions ranging from violet to near-infrared are reported.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7SC03515B
Abstract: PIP–TPE’s fluorescence turns on blue due to the large viscosity of lysosomes which restricts intramolecular motions but it red-shifts in the bulk.
Publisher: Wiley
Date: 19-06-2019
Publisher: International Union of Crystallography (IUCr)
Date: 25-11-2003
DOI: 10.1107/S0108768103024984
Abstract: The 1:2 adduct of benzene-1,2,4,5-tetracarboxylic acid and 4,4′-bipyridyl at 100 K has been studied by single-crystal neutron diffraction at 20, 200 and 296 K. The structure contains two short, strong N...O hydrogen bonds: one O—H...N hydrogen bond [O...N 2.6104 (17) Å at 20 K] and one short N—H...O hydrogen bond [N...O 2.5220 (17) Å at 20 K]. The N—H distance in the N—H...O hydrogen bond changes from 1.207 (3) Å at 20 K to 1.302 (4) Å at 296 K and the N...O distance increases to 2.5315 (16) Å at 296 K. At 200 K the H atom lies in an intermediate position 1.251 (6) Å from the N atom with an N...O separation of 2.520 (4) Å. The O—H...N hydrogen bond, on the other hand, does not change with temperature.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9TB02848J
Abstract: A lipid-droplet-specific AIEgen was used to evaluate the inhibitory efficacy of HIF-1-targeting drugs by assessing lipid-droplet levels.
Publisher: American Chemical Society (ACS)
Date: 07-1997
DOI: 10.1021/JO970337S
Publisher: International Union of Crystallography (IUCr)
Date: 11-03-2006
Publisher: Elsevier BV
Date: 08-1999
Publisher: Wiley
Date: 15-07-2019
Publisher: International Union of Crystallography (IUCr)
Date: 06-05-2021
DOI: 10.1107/S2053229621004460
Abstract: The X-ray structures of three new 1:1 pharmaceutical cocrystals of 11-azaartemisinin (11-Aza systematic name: 1,5,9-trimethyl-14,15,16-trioxa-11-azatetracyclo[10.3.1.0 4,13 .0 8,13 ]hexadecan-10-one, C 15 H 23 NO 4 ) with bromo-substituted salicylic acids [namely, 5-bromo- (5-BrSalA, C 7 H 5 BrO 3 ), 4-bromo- (4-BrSalA, C 7 H 5 BrO 3 ) and 3,5-dibromosalicylic acid (3,5-Br 2 SalA, C 7 H 4 Br 2 O 3 )] are reported. All the structures are related to the parent 11-Aza:SalA cocrystal (monoclinic P 2 1 ) reported previously. The 5-BrSalA analogue is isostructural with the parent, with lattice expansion along the c axis. The 4-BrSalA and 3,5-Br 2 SalA cocrystals retain the highly preserved 2 1 stacks of the molecular pairs, but these pack with a varying degree of slippage with respect to neighbouring stacks, altering the close contacts between them, and represent two potential alternative homostructural arrangements for the parent compound. Structure redeterminations of the bromosalicylic acids 5-BrSalA, 4-BrSalA and 3,5-Br 2 SalA at 100 K show that the packing efficiency of the cocrystals need not be higher than the parent coformers, based on specific-volume calculations, attributable to the strong O—H...O=C hydrogen bonds of 2.54 Å in the cocrystals.
Publisher: Wiley
Date: 2002
DOI: 10.1002/1099-0690(20021)2002:1<113::AID-EJOC113>3.0.CO;2-N
Publisher: American Chemical Society (ACS)
Date: 27-08-2018
Abstract: Sensitive and accurate detection of highly contagious virus is urgently demanded for disease diagnosis and treatment. Herein, based on a multifunctional aggregation-induced emission luminogen (AIEgen), a dual-modality readout immunoassay platform for ultrasensitive detection of viruses has been successfully demonstrated. The platform is relied on virions immuno-bridged enzymatic hydrolysis of AIEgen, accompanying with the in situ formation of highly emissive AIE aggregates and shelling of silver on gold nanoparticles. As a result, robust turn-on fluorescence and naked-eye discernible plasmonic colorimetry composed dual-signal is achieved. By further taking advantage of effective immunomagnetic enrichment, EV71 virions, as an ex le, can be specifically detected with a limit of detection down to 1.4 copies/μL under fluorescence modality. Additionally, semiquantitative discerning of EV71 virions is realized in a broad range from 1.3 × 10
Publisher: Wiley
Date: 09-11-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7CE01875D
Abstract: The R22(8) lactam : acid hetero-synthon, found in several new 1 : 1 and 2 : 1 cocrystals between the anti-malarial 11-azaartemisinin and organic acids.
Publisher: American Chemical Society (ACS)
Date: 14-01-2019
Publisher: American Chemical Society (ACS)
Date: 22-08-2019
DOI: 10.1021/JACS.9B06196
Abstract: Acrylonitriles with aggregation-induced emission (AIE) characteristics have been found to show promising applications in two-photon biomedical imaging. Generally, elaborate synthetic efforts are required to achieve different acrylonitriles with distinct functionalities. In this work, we first reported the synthesis of two different group-functionalized AIE-active acrylonitriles (TPAT-AN-XF and 2TPAT-AN) obtained simply by mixing the same reactants at different temperatures using a facile and transition metal-free synthetic method. These two AIE luminogens (AIEgens) exhibit unique properties such as bright red emission in the solid state, large Stokes shift, and large two-photon absorption cross section. Water-soluble nanoparticles (NPs) of 2TPAT-AN were prepared by a nanoprecipitation method. In vitro imaging data show that 2TPAT-AN NPs can selectively stain lysosome in live cells. Besides one-photon imaging, remarkable two-photon imaging of live tumor tissues can be achieved with high resolution and deep tissue penetration. 2TPAT-AN NPs show high biocompatibility and are successfully utilized in in vivo long-term imaging of mouse tumors with a high signal-to-noise ratio. Thus, the present work is anticipated to shed light on the preparation of a library of AIE-active functionalized acrylonitriles with intriguing properties for biomedical applications.
Publisher: Elsevier BV
Date: 2001
Publisher: Wiley
Date: 16-09-2019
Abstract: Nonlinear optical microscopy has become a powerful tool in bioimaging research due to its unique capabilities of deep optical sectioning, high-spatial-resolution imaging, and 3D reconstruction of biological specimens. Developing organic fluorescent probes with strong nonlinear optical effects, in particular third-harmonic generation (THG), is promising for exploiting nonlinear microscopic imaging for biomedical applications. Herein, a simple method for preparing organic nanocrystals based on an aggregation-induced emission (AIE) luminogen (DCCN) with bright near-infrared emission is successfully demonstrated. Aggregation-induced nonlinear optical effects, including two-photon fluorescence (2PF), three-photon fluorescence (3PF), and THG, of DCCN are observed in nanoparticles, especially for crystalline nanoparticles. The nanocrystals of DCCN are successfully applied for 2PF microscopy at 1040 nm NIR-II excitation and THG microscopy at 1560 nm NIR-II excitation, respectively, to reconstruct the 3D vasculature of the mouse cerebral vasculature. Impressively, the THG microscopy provides much higher spatial resolution and brightness than the 2PF microscopy and can visualize small vessels with diameters of ≈2.7 µm at the deepest depth of 800 µm in a mouse brain. Thus, this is expected to inspire new insights into the development of advanced AIE materials with multiple nonlinearity, in particular THG, for multimodal nonlinear optical microscopy.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2MH00808D
Abstract: A radical polymer without any delocalized π-stabilization was synthesized from a classical chromophore quencher, TEMPO, which surprisingly shows red emission.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3SC50648G
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SC02810A
Abstract: This work provides a new strategy to design heterocycle-containing AIEgens from non-emissive heteroaromatics and promotes their applications for long-term lysosome imaging.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SC01170B
Abstract: Photocyclized intermediate formation and quasi CC twisting are the dominant processes behind the AIE.
Publisher: Wiley
Date: 20-11-2019
Abstract: Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room-temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K
Publisher: Wiley
Date: 20-11-2019
Abstract: We have studied the photophysics of tetrafurylethene, an aggregation‐induced emission luminogen with exceptionally short intramolecular O−O distances of 2.80 Å and a significant red‐shifted morphochromism (27 nm) when going from the aggregate to the crystal. The short O−O distances, which are substantially smaller than the sum of the van der Waals radii (3.04 Å), are due to the fact that the oxygen atoms act as an electronic bridge connecting the furan rings on opposite ends of the central double bond, giving rise to a circular delocalization of the π‐electron density across the rings. In the excited state the O−O distance is further reduced to 2.70 Å the increased O−O interaction causes a narrowing of the HOMO–LUMO gap, resulting in the red morphochromism of the emission. Our results show the structural origin of the red‐shifted emission lies in close O−O contacts, paving the way for understanding the clusteroluminescence of oxygen‐rich non‐conjugated systems that emit visible light.
Publisher: Wiley
Date: 28-02-2019
Abstract: The development of molecular machines requires new building blocks which are easy to characterize and visualize to realize a complexity comparable to their natural counterparts such as biological enzymes. Furthermore, with the desire to build functional nanobots capable of navigating living organisms, it is necessary that the building blocks show mobility even in the solid state. Herein we report a system which is emissive in the amorphous state but is non-fluorescent in the crystalline state due to the formation of extensive π-π interactions. This dual nature could be exploited for easy visualization of its solid-state molecular rearrangement. The emission of the amorphous film was quenched as the molecules spontaneously formed π-π interactions even in the solid state. Scratching the non-emissive film destroyed the interactions and restored the emission of the film. The emission quickly disappeared with an average lifetime of 20 s as the compound reformed the π-network even at room temperature.
Publisher: American Chemical Society (ACS)
Date: 02-10-2018
Publisher: Wiley
Date: 22-04-2020
Publisher: American Chemical Society (ACS)
Date: 03-11-2017
DOI: 10.1021/JACS.7B08592
Abstract: π-Bonds connected with aromatic rings were generally believed as the standard structures for constructing highly efficient fluorophores. Materials without these typical structures, however, exhibited only low fluorescence quantum yields and emitted in the ultraviolet spectral region. In this work, three molecules, namely bis(2,4,5-trimethylphenyl)methane, 1,1,2,2-tetrakis(2,4,5-trimethylphenyl)ethane, and 1,1,2,2-tetraphenylethane, with nonconjugated structures and isolated phenyl rings were synthesized and their photophysical properties were systematically investigated. Interestingly, the emission spectra of these three molecules could be well extended to 600 nm with high solid-state quantum yields of up to 70%. Experimental and theoretical analyses proved that intramolecular through-space conjugation between the "isolated" phenyl rings played an important role for this abnormal phenomenon.
Publisher: American Chemical Society (ACS)
Date: 13-04-2021
DOI: 10.26434/CHEMRXIV.14400953
Abstract: a Apart from the traditional through-bond conjugation (TBC), through-space conjugation (TSC) is gradually proved as another important interaction in photophysical processes, especially for the recent observation of clusteroluminescence from nonconjugated molecules. /a Herein, a simple and nonconjugated triphenylmethane (TPM) and its derivatives with electron-donating and electron-withdrawing groups were synthesized /a , and their photophysical properties were systematically studied. a TPM was characterized with visible clusteroluminescence due to the intramolecular TSC. Experimental and theoretical results showed that the introduction of electron-donating groups into TPM could /a a red-shift /a the wavelength and increase the efficiency of clusteroluminescence simultaneously, due to the increased electronic density and stabilization of TSC. However, TPM derivatives with electron-withdrawing groups showed inefficient or even quenched clusteroluminescence caused by the vigorous excited-state intramolecular motion and intermolecular photoinduced electron transfer process. This work provides a reliable strategy to manipulate TSC and clusteroluminescence.
Publisher: American Chemical Society (ACS)
Date: 16-07-2004
DOI: 10.1021/IC049744U
Abstract: Interaction of PdCl(2)(MeCN)(2) with 2 equiv of (S(P))-(t)BuPhP(O)H (1H) followed by treatment with Et(3)N gave [Pd((1)(2)H)](2)(micro-Cl)(2) (2). Reaction of 2 with Na[S(2)CNEt(2)] or K[N(PPh(2)S)(2)] afforded Pd[(1)(2)H](S(2)CNEt(2)) (3) or Pd[(1)(2)H)[N(PPh(2)S)(2)] (4), respectively. Treatment of 3 with V(O)(acac)(2) (acac = acetylacetonate) and CuSO(4) in the presence of Et(3)N afforded bimetallic complexes V(O)[Pd(1)(2)(S(2)CNEt(2))](2) (5) or Cu[Pd(1)(2)(S(2)CNEt(2))](2) (6), respectively. X-ray crystallography established the S(P) configuration for the phosphinous acid ligands in 3 and 6, indicating that 1H binds to Pd(II) with retention of configuration at phosphorus. The geometry around Cu in 6 is approximately square planar with the average Cu-O distance of 1.915(3) A. Treatment of 2 with HBF(4) gave the BF(2)-capped compound [Pd((1)(2)BF(2))](2)(micro-Cl)(2) (7). The solid-state structure of 7 containing a PdP(2)O(2)B metallacycle has been determined. Chloride abstraction of 7 with AgBF(4) in acetone/water afforded the aqua compound [Pd((1)(2)BF(2))(H(2)O)(2)][BF(4)] (8) that reacted with [NH(4)](2)[WS(4)] to give [Pd((1)(2)BF(2))(2)](2)[micro-WS(4)] (9). The average Pd-S and W-S distances in 9 are 2.385(3) and 2.189(3) A, respectively. Treatment of [(eta(6)-p-cymene)RuCl(2)](2) with 1H afforded the phosphinous acid adduct (eta(6)-p-cymene)RuCl(2)(1H) (10). Reduction of [CpRuCl(2)](x)() (Cp = eta(5)-C(5)Me(5)) with Zn followed by treatment with 1H resulted in the formation of the Zn(II) phosphinate complex [(CpRu(eta(6)-C(6)H(5)))(t)BuPO(2))](2)(ZnCl(2))(2) (11) that contains a Zn(2)O(4)P(2) eight-membered ring.
Publisher: American Chemical Society (ACS)
Date: 11-06-2021
DOI: 10.1021/JACS.1C03882
Publisher: Royal Society of Chemistry (RSC)
Date: 1995
DOI: 10.1039/C39950002479
Publisher: Wiley
Date: 11-10-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5CC04977F
Abstract: Cations of tetrahydropalmatine (THP), 1,2-diaminopropane (1,2-dap) and [Co(phen) 3 ] 3+ are all readily resolved by the red [B S ( R -Man) 2 ] anions with % ee in 1 easy step.
Publisher: Wiley
Date: 26-09-2007
Abstract: Artesunate drug substance, for which a rectal capsule formulation is under development for the treatment of severe malaria, when heated at 100 degrees C for 39 h gives beta-artesunate, artesunate dimers, 9,10-anhydrodihydroartemisinin (glycal), a DHA beta-formate ester, and smaller amounts of other products that arise via intermediate formation of dihydroartemisinin (DHA) and subsequent thermal degradation. Solid DHA at 100 degrees C provides an epimeric mixture of a known peroxyhemiacetal, arising via ring opening to a hydroperoxide and re-closure, smaller amounts of a 3:1 mixture of epimers of a known tricarbonyl compound, and a single epimer of a new dicarbonyl compound. The latter arises via homolysis of the peroxide and an ensuing cascade of alpha-cleavage reactions which leads to loss of formic acid incorporating the C10 carbonyl group of DHA exposed by this 'unzipping' cascade. The tricarbonyl compound that arises via peroxide homolysis and extrusion of formic acid from a penultimate hydroxyformate ester incorporating C12 of the original DHA, is epimeric at the exocyclic 1''-aldehyde, and not in the cyclohexanone moiety. It is converted into the dicarbonyl compound by peroxide-induced deformylation. The dicarbonyl compound is not formed during anhydrous ferrous bromide mediated decomposition of DHA at room temperature, which provides the 1''-R epimer of the tricarbonyl compound as the dominant product this equilibrates at room temperature to the 3:1 mixture of epimers of the tricarbonyl compound obtained from thermolysis. Each of artesunate and DHA decomposes readily under aqueous acidic conditions to provide significant amounts of the peroxyhemiacetal, which, like DHA, decomposes to the inert end product 2-deoxyartemisinin under acidic or basic conditions. DHA and the peroxyhemiacetal are the principal degradants in aged rectal capsule formulations of artesunate. TGA analysis and thermal degradation of DHA reveals a thermal lability which would pose a problem not only in relation to ICH stability testing guidelines, but in the use of DHA in fixed formulations currently under development. This thermolability coupled with the poor physicochemical properties and relative oral bioavailability of DHA suggests that it is inferior to artesunate in application as an antimalarial drug.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9SC04239C
Abstract: A polymorphic AIEgen is capable of selective growth in amorphous and crystalline polymer phases with distinct color for microstructure visualization.
Publisher: American Chemical Society (ACS)
Date: 02-07-2018
Publisher: Wiley
Date: 09-02-2021
Publisher: Wiley
Date: 07-08-2018
Publisher: American Chemical Society (ACS)
Date: 28-07-2020
DOI: 10.1021/JACS.0C06305
Publisher: American Chemical Society (ACS)
Date: 07-1998
DOI: 10.1021/JO984003U
Publisher: Wiley
Date: 26-09-2007
Abstract: As the clinically used artemisinins do not withstand the thermal stress testing required to evaluate shelf life for storage in tropical countries where malaria is prevalent, there is a need to develop thermally more robust artemisinin derivatives. Herein we describe the attachment of electron-withdrawing arene- and alkanesulfonyl and -carbonyl groups to the nitrogen atom of the readily accessible Ziffer 11-azaartemisinin to provide the corresponding N-sulfonyl- and -carbonylazaartemisinins. Two acylurea analogues were also prepared by treatment of the 11-azaartemisinin with arylisocyanates. Several of the N-sulfonylazaartemisinins have melting points above 200 degrees C and possess substantially greater thermal stabilities than the artemisinins in current clinical use, with the antimalarial activities of several of the arylsulfonyl derivatives being similar to that of artesunate against the drug-sensitive 3D7 clone of the NF54 isolate and the multidrug-resistant K1 strain of P. falciparum. The compounds possess relatively low cytotoxicities. The carbonyl derivatives are less crystalline than the N-sulfonyl derivatives, but are generally more active as antimalarials. The N-nitroarylcarbonyl and arylurea derivatives possess sub-ng ml(-1) activities. Although several of the azaartemisinins possess log P values below 3.5, the compounds have poor aqueous solubility (<1 mg L(-1) at pH 7). The greatly enhanced thermal stability of our artemisinins suggests that strategic incorporation of electron-withdrawing polar groups into both new artemisinin derivatives and totally synthetic trioxanes or trioxolanes may assist in the generation of practical new antimalarial drugs which will be stable to storage conditions in the field, while retaining favorable physicochemical properties.
Publisher: American Chemical Society (ACS)
Date: 21-06-2021
DOI: 10.1021/JACS.1C02594
Publisher: International Union of Crystallography (IUCr)
Date: 14-11-2005
DOI: 10.1107/S0108768105030077
Abstract: Pyridine-3,5-dicarboxylic acid has been studied by single-crystal neutron diffraction at 15 and 296 K. Pyridine-3,5-dicarboxylic acid, in which the carboxylic acid protons have been replaced by deuterons, has also been studied at 15, 150 and 296 K. The protonated structure contains a short N...H...O hydrogen bond [N...O 2.523 (2) Å at 15 K]. Temperature-dependent proton migration occurs where the N—H distance in the hydrogen bond changes from 1.213 (4) Å at 15 K to 1.308 (6) Å at 300 K. In the deuterated structure the overall hydrogen-bond length increased [N...O 2.538 (3) Å at 15 K] and the magnitude of the migration increased so that the N—D distance changes from 1.151 (3) Å at 15 K to 1.457 (4) Å at 300 K.
Publisher: American Chemical Society (ACS)
Date: 25-05-2021
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2002
DOI: 10.1097/00001756-200212200-00001
Abstract: Psychophysical experiments identified effects of galvanic vestibular stimulation (GVS) on the perception of whole-body angular rotation. Subjects lay supine on a platform that could rotate about a vertical axis through the vestibular axis so that linear movements were excluded. Movements were applied sufficiently above perception threshold to enable a reliable report of direction and movement size. In some trials, binaural GVS was applied concurrently at 1-2 mA. When GVS that was incongruent with the movement was applied, subjects reported lesser spin, on average cancelling the movement perception. When the GVS and movement were congruent, subjects reported greater spin. We conclude that GVS produces a vestibular signal of rotation, probably though an effect on semicircular canals.
Publisher: American Chemical Society (ACS)
Date: 22-04-2005
DOI: 10.1021/JP0503462
Abstract: We synthesized a group of silole regioisomers 1(x,y), whose photoluminescence varied dramatically with its regiostructure. By internally hindering the intramolecular rotation, we succeeded in creating a novel silole (1(3,4)) that is strongly luminescent in solutions and whose fluorescence quantum yield in acetone is as high as 83%. We revealed that 1(3,4) was a sensitive chemosensor capable of optically discriminating nitroaromatic regioisomers of p-, o-, and m-nitroanilines. Against general belief, crystal formation of 1(2,4) blue-shifted its emission color and boosted its emission efficiency. The light-emitting diode based on the crystal of 1(2,4) emitted a strong blue light (464 nm) in a high current efficiency (5.86 cd/A).
Publisher: Elsevier BV
Date: 2001
Publisher: American Chemical Society (ACS)
Date: 09-05-2018
DOI: 10.1021/JACS.8B02350
Abstract: Multimodality imaging is highly desirable for accurate diagnosis by achieving high sensitivity, spatial-temporal resolution, and penetration depth with a single structural unit. However, it is still challenging to integrate fluorescent and plasmonic modalities into a single structure, as they are naturally incompatible because of significant fluorescence quenching by plasmonic noble-metal nanoparticles. Herein, we report a new type of silver@AIEgen (aggregation-induced emission luminogen) core-shell nanoparticle (AACSN) with both strong aggregated-state fluorescence of the AIEgen and distinctive plasmonic scattering of silver nanoparticles for multimodality imaging in living cells and small animals. The AACSNs were prepared through a redox reaction between silver ions and a redox-active AIEgen, which promoted synergistic formation of the silver core and self-assembly of the AIEgen around the core. The resulting AACSNs exhibited good biocompatibility and high resistance to environmental damage. As a result, excellent performance in fluorescence imaging, dark-field microscopy, and X-ray computed tomography-based multimodality imaging was achieved.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SC05192H
Abstract: Crystallization induced S⋯S interactions leading to an unusual luminescent phenomenon.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CC33780K
Abstract: Melding a benzothiazolium unit with tetraphenylethene generates a new hemicyanine luminogen with aggregation-induced emission characteristics the luminogen exhibits crystochromism and its solid-state emission can be repeatedly tuned from yellow or orange to red by grinding-fuming or grinding-heating processes due to the transformation from the crystalline to the amorphous state and vice versa.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0SC04725B
Abstract: A multifunctional, AIE-based, fused five-membered azaheterocycle is photogenerated with light-driven lification to combat the photobleaching issue and fabricate display materials.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9QM00156E
Abstract: Excited-state “double-bond” torsion plays an important role in the nonluminescent behaviour of a stilbene-based twisted isomer.
Publisher: Wiley
Date: 28-02-2018
Publisher: American Chemical Society (ACS)
Date: 16-12-2021
Publisher: American Chemical Society (ACS)
Date: 27-01-2018
DOI: 10.1021/JACS.7B13364
Abstract: Seeking new methods to obtain elaborate artificial on-demand photoswitching with multiple functionalities remains challenging. Most of the systems reported so far possess only one specific function and their nonemissive nature in the aggregated state inevitably limit their applications. Herein, a tailored cyanostilbene-based molecule with aggregation-induced emission characteristic was synthesized and was found to exhibit efficient, multiple and controllable photoresponsive behaviors under different conditions. Specifically, three different reactions were involved: (i) reversible Z/E isomerization under room light and thermal treatment in CH
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SC01709C
Abstract: This article presents a new strategy to achieve white-light emission from single tetraphenylethylene-substituted pyrenes (TPE-Pys) with aggregation-induced emission (AIE) characteristics.
Publisher: Wiley
Date: 23-07-2010
Abstract: The antimalarial drug methylene blue (MB) affects the redox behaviour of parasite flavin-dependent disulfide reductases such as glutathione reductase (GR) that control oxidative stress in the malaria parasite. The reduced flavin adenine dinucleotide cofactor FADH(2) initiates reduction to leucomethylene blue (LMB), which is oxidised by oxygen to generate reactive oxygen species (ROS) and MB. MB then acts as a subversive substrate for NADPH normally required to regenerate FADH(2) for enzyme function. The synergism between MB and the peroxidic antimalarial artemisinin derivative artesunate suggests that artemisinins have a complementary mode of action. We find that artemisinins are transformed by LMB generated from MB and ascorbic acid (AA) or N-benzyldihydronicotinamide (BNAH) in situ in aqueous buffer at physiological pH into single electron transfer (SET) rearrangement products or two-electron reduction products, the latter of which dominates with BNAH. Neither AA nor BNAH alone affects the artemisinins. The AA-MB SET reactions are enhanced under aerobic conditions, and the major products obtained here are structurally closely related to one such product already reported to form in an intracellular medium. A ketyl arising via SET with the artemisinin is invoked to explain their formation. Dihydroflavins generated from riboflavin (RF) and FAD by pretreatment with sodium dithionite are rapidly oxidised by artemisinin to the parent flavins. When catalytic amounts of RF, FAD, and other flavins are reduced in situ by excess BNAH or NAD(P)H in the presence of the artemisinins in the aqueous buffer, they are rapidly oxidised to the parent flavins with concomitant formation of two-electron reduction products from the artemisinins regeneration of the reduced flavin by excess reductant maintains a catalytic cycle until the artemisinin is consumed. In preliminary experiments, we show that NADPH consumption in yeast GR with redox behaviour similar to that of parasite GR is enhanced by artemisinins, especially under aerobic conditions. Recombinant human GR is not affected. Artemisinins thus may act as antimalarial drugs by perturbing the redox balance within the malaria parasite, both by oxidising FADH(2) in parasite GR or other parasite flavoenzymes, and by initiating autoxidation of the dihydroflavin by oxygen with generation of ROS. Reduction of the artemisinin is proposed to occur via hydride transfer from LMB or the dihydroflavin to O1 of the peroxide. This hitherto unrecorded reactivity profile conforms with known structure-activity relationships of artemisinins, is consistent with their known ability to generate ROS in vivo, and explains the synergism between artemisinins and redox-active antimalarial drugs such as MB and doxorubicin. As the artemisinins appear to be relatively inert towards human GR, a putative model that accounts for the selective potency of artemisinins towards the malaria parasite also becomes apparent. Decisively, ferrous iron or carbon-centered free radicals cannot be involved, and the reactivity described herein reconciles disparate observations that are incompatible with the ferrous iron-carbon radical hypothesis for antimalarial mechanism of action. Finally, the urgent enquiry into the emerging resistance of the malaria parasite to artemisinins may now in one part address the possibilities either of structural changes taking place in parasite flavoenzymes that render the flavin cofactor less accessible to artemisinins or of an enhancement in the ability to use intra-erythrocytic human disulfide reductases required for maintenance of parasite redox balance.
Publisher: American Chemical Society (ACS)
Date: 28-08-2019
DOI: 10.1021/JACS.9B06493
Abstract: Polymers containing rich chalcogen elements are rarely reported due to the lack of facile synthesis methods. Herein, a novel multicomponent polymerization route toward chalcogen-rich polymers was introduced. A series of poly(vinyl sulfones) (PVSs) were synthesized at room temperature using readily prepared monomers. PVSs were generated with high regio- and stereo-selectivity in high yields (up to 92.3%). Rich chalcogen elements endowed PVSs with distingctive multifunctionalities. The PVSs possessed good solubility and film-forming ability. Their thin films exhibited outstanding refractive indices up to 1.8062 at 550.0 nm together with good optical transparency in the visible region. Thin films of some polymers can also be fabricated into well-resolved fluorescent photopatterns by photolithography. Thanks to the unique redox properties of selenium, postmodification by oxidation reaction of P
Publisher: International Union of Crystallography (IUCr)
Date: 24-05-2018
DOI: 10.1107/S2053229618006320
Abstract: The stoichiometry, X-ray structures and stability of four pharmaceutical cocrystals previously identified from liquid-assisted grinding (LAG) of 11-azaartemisinin (11-Aza systematic name: 1,5,9-trimethyl-14,15,16-trioxa-11-azatetracyclo[10.3.1.0 4,13 .0 8,13 ]hexadecan-10-one) with trans -cinnamic (Cin), maleic (Mal) and fumaric (Fum) acids are herein reported. trans -Cinnamic acid, a mono acid, forms 1:1 cocrystal 11-Aza:Cin ( 1 , C 15 H 23 NO 4 ·C 9 H 8 O 2 ). Maleic acid forms both 1:1 cocrystal 11-Aza:Mal ( 2 , C 15 H 23 NO 4 ·C 4 H 4 O 4 ), in which one COOH group is involved in self-catenation, and 2:1 cocrystal 11-Aza 2 :Mal ( 3 , 2C 15 H 23 NO 4 ·C 4 H 4 O 4 ). Its isomer, fumaric acid, only affords 2:1 cocrystal 11-Aza 2 :Fum ( 4 ). All cocrystal formation appears driven by acid–lactam R 2 2 (8) heterosynthons with short O—H...O=C hydrogen bonds [O...O = 2.56 (2) Å], augmented by weaker C=O...H—N contacts. Despite a better packing efficiency, cocrystal 3 is metastable with respect to 2 , probably due to a higher conformational energy for the maleic acid molecule in its structure. In each case, the microcrystalline powders from LAG were useful in providing seeding for the single-crystal growth.
Publisher: Wiley
Date: 22-10-2019
Abstract: Pathogen infections and cancer are two major human health problems. Herein, we report the synthesis of an organic salt photosensitizer (PS), called 4TPA-BQ, by a one-step reaction. 4TPA-BQ presents aggregation-induced emission features. Owing to the aggregation-induced reactive oxygen species generated and a sufficiently small ΔE
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9SC06441A
Abstract: Mitochondria-targeted photosensitizers with highly efficient singlet oxygen generation, bright near-infrared AIE and good two-photon absorption are obtained through ingenious molecular engineering for cancer cell-selective photodynamic therapy.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for ian williams.