Publications by authors named "Ian D Williams"

180 Publications

Organic Long-Persistent Luminescence from a Single-Component Aggregate.

J Am Chem Soc 2022 Jan 20. Epub 2022 Jan 20.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, China.

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.
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http://dx.doi.org/10.1021/jacs.1c11480DOI Listing
January 2022

Evidence of underestimation in microplastic research: A meta-analysis of recovery rate studies.

Sci Total Environ 2022 Jan 9;805:150227. Epub 2021 Sep 9.

School of Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Highfield Campus, University Road, Southampton SO17 1BJ, United Kingdom. Electronic address:

Research on microplastics in the environment is of high interest to many scientists and industries globally. Key to the success of this research is the accuracy, efficiency, reliability, robustness and repeatability of the method(s) used to isolate the microplastics from environmental media. However, with microplastics now being found in new complex media, many multifaceted methods have been developed to research the quantities of these pollutants. To validate new methods, recovery studies can be undertaken by spiking the test medium with known quantities of plastics. The method is typically run as normal, and the recovered plastics counted to give a recovery rate. A current issue in this field is that methods are rarely or poorly validated in this way. Here, we conducted a meta-analysis on 71 recovery rate studies. We found sediment was the most studied medium and saline solutions were the most used reagents. Polyethylene and polystyrene were the most used spiking polymers, which is relevant to the most common polymers in the environment. We found that recovery rates were highest from plant material, whole organisms and excrement (>88%), and lowest from fishmeal, water and soil (58-71%). Moreover, all reagents but water were able to recover more than 80% of the spiked plastics. We believe we are the first (to our knowledge) to provide an overarching indication for the underestimation of microplastics in the environment of approximately 14% across the studies we reviewed, varying with the methods used. Furthermore, we recommend that the quality, use and reporting of recovery rate studies should be improved to aid the standardisation and replication of microplastic research.
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http://dx.doi.org/10.1016/j.scitotenv.2021.150227DOI Listing
January 2022

How Do Molecular Motions Affect Structures and Properties at Molecule and Aggregate Levels?

J Am Chem Soc 2021 08 22;143(30):11820-11827. Epub 2021 Jul 22.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.

Molecular motions are essential natures of matter and play important roles in their structures and properties. However, owing to the diversity 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.
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http://dx.doi.org/10.1021/jacs.1c05647DOI Listing
August 2021

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen.

Chem Sci 2020 Oct 19;12(2):709-717. Epub 2020 Oct 19.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, State Key Laboratory of Molecular Nanoscience, Division of Life Science, Department of Chemical and Biomedical Engineering and Institute for Advanced Study, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Developing versatile synthetic methodologies with merits of simplicity, efficiency, and environment friendliness for five-membered heterocycles is of incredible importance to pharmaceutical and material science, as well as a huge challenge to synthetic chemistry. Herein, an unexpected regioselective photoreaction to construct a fused five-membered azaheterocycle with an aggregation-induced emission (AIE) characteristic is developed under mild conditions. The formation of the five-membered ring is both thermodynamically and kinetically favored, as justified by theoretical calculation and experimental evidence. Markedly, a light-driven amplification strategy is proposed and applied in selective mitochondria-targeted cancer cell recognition and fluorescent photopattern fabrication with improved resolution. The work not only delivers the first report on efficiently generating a fused five-membered azaheterocyclic AIE luminogen under mild conditions photoreaction, but also offers deep insight into the essence of the photosynthesis of fused five-membered azaheterocyclic compounds.
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http://dx.doi.org/10.1039/d0sc04725bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179000PMC
October 2020

Visualization and Manipulation of Solid-State Molecular Motions in Cocrystallization Processes.

J Am Chem Soc 2021 06 21;143(25):9468-9477. Epub 2021 Jun 21.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biomedical Engineering, Institute for Advanced Study, and Guangdong Hong Kong Macro Joint Laboratory of Optoelectronic and Magnetic Functional Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Solid-state molecular motions (SSMM) play a critical role in adjusting behaviors and properties of materials. However, research on SSMM, especially for multicomponent systems, suffers from various problems and is rarely explored. Herein, through collaboration with cocrystal engineering, visualization and manipulation of SSMM in two-component systems, namely, FSBO (()-2-(4-fluorostyryl)benzo[]oxazole)/TCB (1,2,4,5-tetracyanobenzene) and PVBO (()-2-(2-(pyridin-4-yl)vinyl)benzo[]oxazole)/TCB, were realized. The obtained yellow-emissive F/T (FSBO/TCB) cocrystal displayed turn-on fluorescence, and the green-emissive P/T (PVBO/TCB) cocrystal presented redder emission, both of which exhibited an aggregation-induced emission property. At varied pressure and temperature, the grinding mixtures of FSBO/TCB and PVBO/TCB displayed different molecular motions that were readily observed through the fluorescence signal. Notably, even without grinding, FSBO and TCB molecules could move over for 4 mm in a 1D tube. The unique emission changes induced by SSMM were applied in information storage and dynamic anticounterfeiting. This work not only visualized and manipulated SSMM but offered more insights for multicomponent study in aggregate science.
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http://dx.doi.org/10.1021/jacs.1c02594DOI Listing
June 2021

How to Manipulate Through-Space Conjugation and Clusteroluminescence of Simple AIEgens with Isolated Phenyl Rings.

J Am Chem Soc 2021 Jun 11;143(25):9565-9574. Epub 2021 Jun 11.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.

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. However, unlike TBC in conjugated chromophores, it is still challenging to manipulate TSC and clusteroluminescence. Herein, simple and nonconjugated triphenylmethane (TPM) and its derivatives with electron-donating and electron-withdrawing groups were synthesized, and their photophysical properties were systematically studied. 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 red-shift 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.
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http://dx.doi.org/10.1021/jacs.1c03882DOI Listing
June 2021

Varying degrees of homostructurality in a series of cocrystals of antimalarial drug 11-azaartemisinin with salicylic acids.

Acta Crystallogr C Struct Chem 2021 06 6;77(Pt 6):262-270. Epub 2021 May 6.

Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, People's Republic of China.

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[10.3.1.0.0]hexadecan-10-one, CHNO) with bromo-substituted salicylic acids [namely, 5-bromo- (5-BrSalA, CHBrO), 4-bromo- (4-BrSalA, CHBrO) and 3,5-dibromosalicylic acid (3,5-BrSalA, CHBrO)] are reported. All the structures are related to the parent 11-Aza:SalA cocrystal (monoclinic P2) reported previously. The 5-BrSalA analogue is isostructural with the parent, with lattice expansion along the c axis. The 4-BrSalA and 3,5-BrSalA cocrystals retain the highly preserved 2 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-BrSalA 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.
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http://dx.doi.org/10.1107/S2053229621004460DOI Listing
June 2021

Synthesis, structure and reactivity of iridium complexes containing a bis-cyclometalated tridentate C^N^C ligand.

Dalton Trans 2021 Jun;50(24):8512-8523

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

In an effort to synthesize cyclometalated iridium complexes containing a tridentate C^N^C ligand, transmetallation of [Hg(HC^N^C)Cl] (1) (H2C^N^C = 2,6-bis(4-tert-butylphenyl)pyridine) with various organoiridium starting materials has been studied. The treatment of 1 with [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) in acetonitrile at room temperature afforded a hexanuclear Ir4Hg2 complex, [Cl(κ2C,N-HC^N^C)(cod)IrHgIr(cod)Cl2]2 (2), which features Ir-Hg-Ir and Ir-Cl-Ir bridges. Refluxing 2 with sodium acetate in tetrahydrofuran (thf) resulted in cyclometalation of the bidentate HC^N^C ligand and formation of trinuclear [(C^N^C)(cod)IrHgIr(cod)Cl2] (3). On the other hand, refluxing [Ir(cod)Cl]2 with 1 and sodium acetate in thf yielded [Ir(C^N^C)(cod)(HgCl)] (4). Chlorination of 4 with PhICl2 gave [Ir(C^N^C)(cod)Cl]·HgCl2 (5·HgCl2) that reacted with tricyclohexylphosphine to yield Hg-free [Ir(C^N^C)(cod)Cl] (5). Chloride abstraction of 5 with silver(i) triflate (AgOTf) gave [Ir(C^N^C)(cod)(H2O)](OTf) (6) that can catalyze the cyclopropanation of styrene with ethyl diazoacetate. Reaction of 1 and [Ir(CO)2Cl(py)] (py = pyridine) with sodium acetate in refluxing thf afforded [Ir(C^N^C)(HgCl)(py)(CO)] (7), in which the carbonyl ligand is coplanar with the C^N^C ligand. On the other hand, refluxing 1 with (PPh4)[Ir(CO)2Cl2] and sodium acetate in acetonitrile gave [Ir(C^N^C)(κ2C,N-HC^N^C)(CO)] (8), the carbonyl ligand of which is trans to the pyridyl ring of the bidentate HC^N^C ligand. Upon irradiation with UV light 8 in thf was isomerized to 8', in which the carbonyl is trans to a phenyl group of the bidentate HC^N^C ligand. The isomer pair 8 and 8' exhibited emission at 548 and 514 nm in EtOH/MeOH at 77 K with lifetime of 84.0 and 64.6 μs, respectively. Protonation of 8 with p-toluenesulfonic acid (TsOH) afforded the bis(bidentate) tosylate complex [Ir(κ2C,N-HC^N^C)2(CO)(OTs)] (9) that could be reconverted to 8 upon treatment with sodium acetate. The electrochemistry of the Ir(C^N^C) complexes has been studied using cyclic voltammetry. Reaction of [Ir(PPh3)3Cl] with 1 and sodium acetate in refluxing thf led to isolation of the previously reported compound [Ir(κ2P,C-C6H4PPh2)2(PPh3)Cl] (10). The crystal structures of 2-5, 8, 8', 9 and 10 have been determined.
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http://dx.doi.org/10.1039/d1dt01269jDOI Listing
June 2021

An Air-Stable Organic Radical from a Controllable Photoinduced Domino Reaction of a Hexa-aryl Substituted Anthracene.

J Org Chem 2021 Jun 25;86(11):7359-7369. Epub 2021 May 25.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Air-stable organic radicals and radical ions have attracted great attention for their far-reaching application ranging from bioimaging to organic electronics. However, because of the highly reactive nature of organic radicals, the design and synthesis of air-stable organic radicals still remains a challenge. Herein, an air-stable organic radical from a controllable photoinduced domino reaction of a hexa-aryl substituted anthracene is described. The domino reaction involves a photoinduced [4 + 2] cycloaddition reaction, rearrangement, photolysis, and an elimination reaction; H/C NMR spectroscopy, high resolution mass spectrometry, single-crystal X-ray diffraction, and EPR spectroscopy were exploited for characterization. Furthermore, a photoinduced domino reaction mechanism is proposed according to the experimental and theoretical studies. In addition, the effects of employing push and pull electronic groups on the controllable photoinduced domino reaction were investigated. This article not only offers a new blue emitter and novel air-stable organic radical compound for potential application in organic semiconductor applications, but also provides a perspective for understanding the fundamentals of the reaction mechanism on going from anthracene to semiquinone in such anthracene systems.
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http://dx.doi.org/10.1021/acs.joc.1c00233DOI Listing
June 2021

Developing a systematic method for extraction of microplastics in soils.

Anal Methods 2021 04 22;13(14):1695-1705. Epub 2021 Mar 22.

Faculty of Engineering and Physical Sciences, University of Southampton, Highfield Campus, University Road, Southampton SO17 1BJ, UK.

Microplastics are an environmental issue of global concern. Although they have been found in a range of environments worldwide, their contamination in the terrestrial environment is poorly understood. The lack of standardised methods for their detection and quantification is a major obstacle for determining the risk they pose to soil environments. Here we present a systematic comparison of microplastic extraction methods from soils, taking into account the characteristics of the soil medium to determine the best methods for quantification. The efficiency of organic matter removal using hydrogen peroxide, potassium hydroxide and Fenton's reagent was measured. Soils with a range of particle size distribution and organic matter content were spiked with a variety of microplastic types. Density separation methods using sodium chloride, zinc chloride and canola oil were tested. Recovery efficiencies were calculated and the impact of the reagents on the microplastics was quantified using Attenuated Total Reflectance (ATR) Fourier Transform-Infrared (FTIR) spectroscopy. The optimal organic removal method was found to be hydrogen peroxide. The recovery efficiency of microplastics was variable across polymer types. Overall, canola oil was shown to be the optimal method for density separation, however, efficiency was dependent on the amount of organic matter in the soil. This outcome highlights the importance of including matrix-specific calibration in future studies considering a wide range of microplastic types, to avoid underestimation of microplastic contamination. We show here that methods for extracting microplastics from soils can be simple, cost-effective and widely applicable, which will enable the advancement of microplastic research in terrestrial environments.
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http://dx.doi.org/10.1039/d0ay02086aDOI Listing
April 2021

Regional carbon stock assessment and the potential effects of land cover change.

Sci Total Environ 2021 Jun 12;775:145815. Epub 2021 Feb 12.

Faculty of Engineering and Physical Sciences, University of Southampton, Highfield Campus, University Road, Southampton SO17 1BJ, United Kingdom. Electronic address:

Accurate assessment of carbon stocks remains a global challenge. High levels of uncertainty in Land Use, Land Use Change and Forestry reporting has hindered decision-makers and investors worldwide to support sustainable soil and vegetation management. Potential mitigation-driven activities and effects are likely to be locally/regionally unique. A spatially-targeted approach is thus required to optimise strategic carbon management. This study provides a new regional carbon assessment (tier 3) approach using biophysical-process modelling of high-resolution Land Cover (LC) data within a UK National Park (NFNP) to provide higher accuracy. Future Land Cover Change (LCC) scenarios were simulated. Vegetation-driven carbon dynamics were modelled by coupling two widely-used models, LPJ-GUESS and RothC-26.3. Transition and persistence analysis was conducted using Terrset's Land Change Modeller to predict likely future LCC for 2040 using Multi-Layer Perceptron Markov-Chain Analysis. Current total carbon in the NFNP is 7.32-8.73 Mt C, with current trajectories of LCC leading to minor losses of up to 0.39 Mt C. Alternative LCC scenarios indicated possible gains or losses of 1.27 Mt C, or 136.7 t C ha. The importance of vegetation-driven carbon storage was greater than the national average, with a VegC pool 12-14% of the soil organic C pool, placing greater significance on local/regional LC and management policy. The potential storage capacity of each LC class was ranked (highest to lowest): Coniferous > Broadleaved/Mixed > Coastal > Semi-natural Grassland > Heath > Improved Grassland > Arable (Cropland). Opportunities were prioritised to inform landscape-scale management to reduce future carbon losses and/or to enhance gains through LCC. Balancing the carbon budget relies upon maintaining existing LC. The more detailed LC classification facilitated accounting of management through stock change factors and disaggregation of classes, achieving greater detail and accuracy. Forthcoming policy decisions must optimise carbon storage at a local/regional landscape-scale.
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http://dx.doi.org/10.1016/j.scitotenv.2021.145815DOI Listing
June 2021

Oxidizing Cerium(IV) Alkoxide Complexes Supported by the Kläui Ligand [Co(η-CH){P(O)(OEt)}]: Synthesis, Structure, and Redox Reactivity.

Inorg Chem 2021 Feb 27;60(4):2261-2270. Epub 2021 Jan 27.

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China.

Tetravalent cerium alkoxide complexes supported by the Kläui tripodal ligand [Co(η-CH){P(O)(OEt)}] (L) have been synthesized, and their nucleophilic and redox reactivity have been studied. Treatment of the Ce(IV) oxo complex [Ce(L)(O)(HO)]·MeCONH () with PrOH or reaction of [Ce(L)Cl] () with AgO in PrOH afforded the Ce(IV) dialkoxide complex [Ce(L)(OPr)] (). The methoxide and ethoxide analogues [Ce(L)(OR)] (R = Me (), Et ()) have been prepared similarly from and AgO in ROH. Reaction of with an equimolar amount of yielded a new Ce(IV) complex that was formulated as the chloro-alkoxide complex [Ce(L)(OPr)Cl] (). Treatment of with HX and methyl triflate (MeOTf) afforded [Ce(L)X] (X = Cl, NO, PhO) and [Ce(L)(OTf)], respectively, whereas treatment with excess CO in hexane led to isolation of the Ce(IV) carbonate [Ce(L)(CO)]. reacted with water in hexane to give a Ce(III) complex and a Ce(IV) species, presumably the reported tetranuclear oxo cluster [Ce(L)(O)(OH)]. The Ce(IV) alkoxide complexes are capable of oxidizing substituted phenols, possibly via a proton-coupled electron transfer pathway. Treatment of with ArOH afforded the Ce(III) aryloxide complexes [Ce(L)(OAr)] (Ar = 2,4,6-tri--butylphenyl (), 2,6-diphenylphenyl ()). On the other hand, a Ce(III) complex containing a monodeprotonated 2,2'-biphenol ligand, [Ce(L)(BuCHOH)] () (BuCHOH = 4,4',6,6'-tetra--butyl-2,2'-biphenol), was isolated from the reaction of with 2,4-di--butylphenol. The crystal structures of complexes , , , and - have been determined.
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http://dx.doi.org/10.1021/acs.inorgchem.0c03105DOI Listing
February 2021

Global E-waste management: Can WEEE make a difference? A review of e-waste trends, legislation, contemporary issues and future challenges.

Waste Manag 2021 Feb 9;120:549-563. Epub 2020 Dec 9.

School of Geography and Environmental Science, Faculty of Environmental and Life Sciences, University of Southampton, Highfield Campus, Southampton SO17 1BJ, United Kingdom.

Waste electrical and electronic equipment (WEEE) comprises a globally important waste stream due to the scarcity and value of the materials that it contains; annual generation of WEEE is increasing by 3-5% per annum. The effective management of WEEE will contribute critically to progress towards (1) realisation of the United Nations' Sustainable Development Goals, (2) a circular economy, and (3) resource efficiency. This comprehensive review paper provides a critical and contemporary examination of the current global situation of WEEE management and discusses opportunities for enhancement. Trends in WEEE generation, WEEE-related policies and legislation are exemplified in detail. Four typical future WEEE management scenarios are identified, classified and outlined. The European Community is at the forefront of WEEE management, largely due to the WEEE Directive (Directive 2012/19/EU) which sets high collection and recycling targets for Member States. WEEE generation rates are increasing in Africa though collection and recycling rates are low. WEEE-related legislation coverage is increasing in Asia (notably China and India) and in Latin America. This review highlights emerging concerns, including: stockpiling of WEEE devices; reuse standards; device obsolescence; the Internet of Things, the potential for collecting space e-debris, and emerging trends in electrical and electronic consumer goods. Key areas of concern in regard to WEEE management are identified: the partial provision of formal systems for WEEE collection and treatment at global scale; further escalation of global WEEE generation (increased ownership, and acceleration of obsolescence and redundancy); and absence of regulation and its enforcement. Measures to improve WEEE management at global scale are recommended: incorporation of circular economy principles in EEE design and production, and WEEE management, including urban mining; extension of WEEE legislation and regulation, and improved enforcement thereof; harmonisation of key terms and definitions to permit consistency and meaning in WEEE management; and improvements to regulation and recognition of the informal WEEE management sector.
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http://dx.doi.org/10.1016/j.wasman.2020.10.016DOI Listing
February 2021

Robust Supramolecular Nano-Tunnels Built from Molecular Bricks*.

Angew Chem Int Ed Engl 2021 Mar 9;60(13):7148-7154. Epub 2021 Feb 9.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, SCUT-HKUST Joint Research Institute, Institute for Advanced Study, Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Herein we report a linear ionic molecule that assembles into a supramolecular nano-tunnel structure through synergy of trident-type ionic interactions and π-π stacking interactions. The nano-tunnel crystal exhibits anisotropic guest adsorption behavior. The material shows good thermal stability and undergoes multi-stage single-crystal-to-single-crystal phase transformations to a nonporous structure on heating. The material exhibits a remarkable chemical stability under both acidic and basic conditions, which is rarely observed in supramolecular organic frameworks and is often related to structures with designed hydrogen-bonding interactions. Because of the high polarity of the tunnels, this molecular crystal also shows a large CO -adsorption capacity while excluding other gases at ambient temperature, leading to high CO /CH selectivity. Aggregation-induced emission of the molecules gives the bulk crystals vapochromic properties.
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http://dx.doi.org/10.1002/anie.202013117DOI Listing
March 2021

Albofungin and chloroalbofungin: antibiotic crystals with 2D but not 3D isostructurality.

Acta Crystallogr C Struct Chem 2020 12 25;76(Pt 12):1100-1107. Epub 2020 Nov 25.

Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, People's Republic of China.

The potent antibiotics albofungin [systematic name: (1S,4R,8aR)-13-amino-1,15,16-trihydroxy-4-methoxy-12-methyl-3,4,8a,13-tetrahydro-1H-xantheno[4',3',2':4,5][1,3]benzodioxino[7,6-g]isoquinoline-14,17(2H,9H)-dione, CHNO, 1] and its chlorinated analogue chloroalbofungin (the 11-chloro analogue, CHClNO, 2) have been crystallized following their isolation from the bacterial strain Streptomyces chrestomyceticus and their structures determined by single-crystal X-ray diffraction. The novel N-aminoquinolone molecular arrangement shows N-N bond lengths of 1.4202 (16) and 1.424 (2) Å in 1 and 2, respectively. The regiochemistry of chloro substitution in the A-ring is para to the quinolone O atom, with a C-Cl bond length of 1.741 (2) Å. The absolute stereochemistry at three chiral centres of the xanthone rings (i.e. 10S, 13R and 19R) is confirmed. Both compounds crystallize in chiral Sohncke space groups consistent with enantiopurity, but are not fully isostructural. A preserved supramolecular construct (SC) confers two-dimensional (2D) isostructurality, but the SC self-associates via either a twofold screw operation in 1, giving a monoclinic P2 structure, or a twofold rotation in 2, affording a monoclinic C2 structure with a doubled unit-cell axis.
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http://dx.doi.org/10.1107/S2053229620015041DOI Listing
December 2020

Identification of tidal trapping of microplastics in a temperate salt marsh system using sea surface microlayer sampling.

Sci Rep 2020 08 24;10(1):14147. Epub 2020 Aug 24.

National Oceanography Centre, Southampton, SO14 3ZH, UK.

Microplastics are contaminants of increasing global environmental concern. Estuaries are a major transport pathway for land-derived plastics to the open ocean but are relatively understudied compared to coastal and open marine environments. The role of the "estuarine filter", by which the supply of sediments and contaminants to the sea is moderated by processes including vegetative trapping and particle flocculation, remains poorly defined for microplastics land to sea transfer. Here, we focus on the sea surface microlayer (SML) as a vector for microplastics, and use SML sampling to assess microplastic trapping in a temperate marsh system in Southampton Water, UK. The SML is known to concentrate microplastics relative to the underlying water and is the first part of rising tidal waters to traverse intertidal and upper tidal surfaces. Sampling a salt marsh creek at high temporal resolution allowed assessment of microplastics in-wash and outflow from the salt marsh, and its relationship with tidal state and bulk suspended sediment concentrations (SSC), over spring and neap tides. A statistically significant decrease in microplastics abundance from the flood tide to the ebb tide was found, and a weak positive relationship with SSC observed.
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http://dx.doi.org/10.1038/s41598-020-70306-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7445233PMC
August 2020

Molecular Motions in AIEgen Crystals: Turning on Photoluminescence by Force-Induced Filament Sliding.

J Am Chem Soc 2020 08 4;142(34):14608-14618. Epub 2020 Aug 4.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering, Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Life process is amazing, and it proceeds against the eternal law of entropy increase through molecular motion and takes energy from the environment to build high-order complexity from chaos to achieve evolution with more sophisticated architectures. Inspired from the elegance of life process and also to effectively exploit the undeveloped solid-state molecular motion, two unique chiral Au(I) complexes were elaborately developed in this study, in which their powders could realize a dramatic transformation from nonemissive isolated crystallites to emissive well-defined microcrystals under the stimulation of mechanical force. Such an unusual crystallization was presumed to be caused by molecular motions driven by the formation of strong aurophilic interactions as well as multiple C-H···F and π-π interactions. Such a prominent macroscopic off/on luminescent switching could also be achieved through extremely subtle molecular motions in the crystal state and presented a filament sliding that occurred in a layer-by-layer molecular stacking fashion with no involvement of any crystal phase transition. Additionally, it had been demonstrated that the manipulation of the solid-state molecular motions could result in the generation of circularly polarized luminescence.
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http://dx.doi.org/10.1021/jacs.0c06305DOI Listing
August 2020

Chiral Phosphoric Acid Catalyzed Enantioselective Synthesis of α-Tertiary Amino Ketones from Sulfonium Ylides.

J Am Chem Soc 2020 08 7;142(33):14384-14390. Epub 2020 Aug 7.

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, SAR China.

Herein we disclose a new catalytic asymmetric approach for the synthesis of chiral α-amino ketones, which is particularly useful for the less accessible acyclic α-tertiary cases. By a protonation-amination sequence, our approach represents a rare asymmetric H-heteroatom bond insertion by α-carbonyl sulfonium ylides, an attractive surrogate of diazocarbonyls. The mild intermolecular C-N bond formation was catalyzed by chiral phosphoric acids with excellent efficiency and enantioselectivity. The products are precursors to other important chiral amine derivatives, including drug molecules and chiral ligands. The enantioselectivity was controlled by dynamic kinetic resolution in the amination step, rather than the initial protonation. This process opens up a new platform for the development of other related insertion reactions.
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http://dx.doi.org/10.1021/jacs.0c07210DOI Listing
August 2020

Robust Alkyne Metathesis Catalyzed by Air Stable d Re(V) Alkylidyne Complexes.

J Am Chem Soc 2020 08 24;142(31):13339-13344. Epub 2020 Jul 24.

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

We report in this communication the first example of catalytic alkyne metathesis reactions mediated by well-defined non-d alkylidyne complexes. The air-stable d Re(V) alkylidyne complex , bearing two PO-chelating ligands and a labile pyridine ligand, could catalyze homometathesis of internal alkynes with a broad substrate scope, including alcohols, amines, and even carboxylic acids. The catalyst can tolerate heating, air, and moisture in both solid and solution states, and the catalytic metathesis reactions could proceed normally in wet solvents.
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http://dx.doi.org/10.1021/jacs.0c06581DOI Listing
August 2020

Chiral anionic layers in tartramide spiroborate salts and variable solvation for [NR][B(TarNH)] (R = Et, Pr or Bu).

Acta Crystallogr C Struct Chem 2020 Jul 30;76(Pt 7):695-705. Epub 2020 Jun 30.

Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, People's Republic of China.

The spiroborate anion, namely, 2,3,7,8-tetracarboxamido-1,4,6,9-tetraoxa-5λ-boraspiro[4.4]nonane, [B(TarNH)], derived from the diol L-tartramide TarNH, [CH(O)(CONH)], shows a novel self-assembly into two-dimensional (2D) layer structures in its salts with alkylammonium cations, [NR] (R = Et, Pr and Bu), and sparteinium, [HSpa], in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, CHN·CHBNO, the tetraethylazanium salt hydrate, CHN·CHBNO·6.375HO, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, CHN·CHBNO·CHOH·0.5HO, and the sparteinium (7-aza-15-azoniatetracyclo[7.7.1.0.0]heptadecane) salt as the ethanol monosolvate, CHN·CHBNO·CHOH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt] salt is highly hydrated with around 6.5HO per cation, the [NPr] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu] salt is intermediate and has EtOH and HO in its cation layer, which is similar to the arrangement for the chiral [HSpa] cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.
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http://dx.doi.org/10.1107/S2053229620008384DOI Listing
July 2020

Crystal structures of the flavonoid Oroxylin A and the regioisomers Negletein and Wogonin.

Acta Crystallogr C Struct Chem 2020 05 24;76(Pt 5):490-499. Epub 2020 Apr 24.

Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, People's Republic of China.

The flavonoid Oroxylin A (6-methoxychrysin or 5,7-dihydroxy-6-methoxy-2-phenyl-4H-chromen-4-one, CHO) and its regioisomers are of increasing interest for a variety of bioactive functions and their pharmaceutical formulation is of importance. Previous difficulties in the separation and misidentification of Oroxylin A from its regioisomers Wogonin (8-methoxychrysin or 5,7-dihydroxy-8-methoxy-2-phenyl-4H-chromen-4-one) and Negletein (5,6-dihydroxy-7-methoxyflavone or 5,6-dihydroxy-7-methoxy-2-phenyl-4H-chromen-4-one) render its full structural and powder X-ray characterization highly desirable. The low-temperature (100 K) crystal structures of Oroxylin A, Negletein and Wogonin sesquihydrate are reported for the first time. Wogonin crystallizes in two related but distinct hydrated forms. These have very similar powder diffractograms, indicating that such issues need to be addressed for its pharmaceutical formulation.
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http://dx.doi.org/10.1107/S2053229620005550DOI Listing
May 2020

Two Are Better Than One: A Design Principle for Ultralong-Persistent Luminescence of Pure Organics.

Adv Mater 2020 Jun 22;32(22):e2001026. Epub 2020 Apr 22.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

Because of their innate ability to store and then release energy, long-persistent luminescence (LPL) materials have garnered strong research interest in a wide range of multidisciplinary fields, such as biomedical sciences, theranostics, and photonic devices. Although many inorganic LPL systems with afterglow durations of up to hours and days have been reported, organic systems have had difficulties reaching similar timescales. In this work, a design principle based on the successes of inorganic systems to produce an organic LPL (OLPL) system through the use of a strong organic electron trap is proposed. The resulting system generates detectable afterglow for up to 7 h, significantly longer than any other reported OLPL system. The design strategy demonstrates an easy methodology to develop organic long-persistent phosphors, opening the door to new OLPL materials.
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http://dx.doi.org/10.1002/adma.202001026DOI Listing
June 2020

monitoring of tissue regeneration using a ratiometric lysosomal AIE probe.

Chem Sci 2020 Feb 11;11(12):3152-3163. Epub 2020 Feb 11.

HKUST-Shenzhen Research Institute No. 9 Yuexing 1st RD, South Area, Hi-tech Park, Nanshan Shenzhen 518057 China

Tissue regeneration is a crucial self-renewal capability involving many complex biological processes. Although transgenic techniques and fluorescence immunohistochemical staining have promoted our understanding of tissue regeneration, simultaneous quantification and visualization of tissue regeneration processes is not easy to achieve. Herein, we developed a simple and quantitative method for the real-time and non-invasive observation of the process of tissue regeneration. The synthesized ratiometric aggregation-induced-emission (AIE) probe exhibits high selectivity and reversibility for pH responses, good ability to map lysosomal pH both and , good biocompatibility and excellent photostability. The caudal fin regeneration of a fish model (medaka larvae) was monitored by tracking the lysosomal pH change. It was found that the mean lysosomal pH is reduced during 24-48 hpa to promote the autophagic activity for cell debris degradation. Our research can quantify the changes in mean lysosomal pH and also exhibit its distribution during the caudal fin regeneration. We believe that the AIE-active lysosomal pH probe can also be potentially used for long-term tracking of various lysosome-involved biological processes, such as tracking the stress responses of tissue, tracking the inflammatory responses, and so on.
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http://dx.doi.org/10.1039/c9sc06226bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157324PMC
February 2020

A lipophilic AIEgen for lipid droplet imaging and evaluation of the efficacy of HIF-1 targeting drugs.

J Mater Chem B 2020 02;8(7):1516-1523

HKUST Shenzhen Research Institute, No. 9 Yuexing 1st RD, South Area, Hi-tech Park, Nanshan, Shenzhen 518057, China. and Department of Chemistry, Department of Chemical and Biological Engineering, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and Institute of Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China and Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet, Hong Kong and NSFC Center for Luminescence from Molecular Aggregate, Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China.

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that mediates the cellular response to hypoxia. The upregulation of HIF-1 expression in hypoxic cells can induce the accumulation of lipid droplets (LDs), and the LD levels can in turn reflect the expression level of HIF-1. Herein, we report a LD-specific luminogen with aggregation-induced emission characteristics (AIEgen), and have explored its potential applications in the evaluation of the inhibitory efficacy of HIF-1 targeting drugs. Compared to Nile red, this AIEgen shows a larger Stokes shift, better photostability, a more sensitive response to changes in dye concentration and a broader quantitative range. We found that the AIEgen can be used for semi-quantifying LD levels in cancer cells under hypoxic conditions, and for evaluating the inhibitory efficacy of HIF-1 targeting drugs. This work provides a simple and cost-effective strategy for screening HIF-1-targeted drugs, which may also be an alternative for evaluating the drug efficacy of other LD-related diseases.
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http://dx.doi.org/10.1039/c9tb02848jDOI Listing
February 2020

Highly efficient singlet oxygen generation, two-photon photodynamic therapy and melanoma ablation by rationally designed mitochondria-specific near-infrared AIEgens.

Chem Sci 2020 Jan 21;11(9):2494-2503. Epub 2020 Jan 21.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Institute of Molecular Functional Materials, Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology (HKUST) Clear Water Bay Kowloon Hong Kong China

Photosensitizers (PSs) with multiple characteristics, including efficient singlet oxygen (O) generation, cancer cell-selective accumulation and subsequent mitochondrial localization as well as near-infrared (NIR) excitation and bright NIR emission, are promising candidates for imaging-guided photodynamic therapy (PDT) but rarely concerned. Herein, a simple rational strategy, namely modulation of donor-acceptor (D-A) strength, for molecular engineering of mitochondria-targeting aggregation-induced emission (AIE) PSs with desirable characteristics including highly improved O generation efficiency, NIR emission (736 nm), high specificity to mitochondria, good biocompatibility, high brightness and superior photostability is demonstrated. Impressively, upon light irradiation, the optimal NIR AIE PS (DCQu) can generate O with efficiency much higher than those of commercially available PSs. The excellent two-photon absorption properties of DCQu allow two-photon fluorescence imaging of mitochondria and subsequent two-photon excited PDT. DCQu can selectively differentiate cancer cells from normal cells without the aid of extra targeting ligands. Upon ultralow-power light irradiation at 4.2 mW cm, mitochondrial photodynamic activation to specifically damage cancer cells and efficient melanoma ablation are demonstrated, suggesting superior potency of the AIE PS in imaging-guided PDT with minimal side effects, which is promising for future precision medicine.
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http://dx.doi.org/10.1039/c9sc06441aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157451PMC
January 2020

Polymorph selectivity of an AIE luminogen under nano-confinement to visualize polymer microstructures.

Chem Sci 2019 Nov 22;11(4):997-1005. Epub 2019 Nov 22.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Development of Chemical and Biological Engineering, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within the polymer network are dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen with green emission is stabilized in the amorphous phase, while a metastable polymorph with yellow emission is confined in the crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phase distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of the AIE luminogen in the polymer network can achieve free space recognition and also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision that our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogens for various applications.
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http://dx.doi.org/10.1039/c9sc04239cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8146380PMC
November 2019

New Wine in Old Bottles: Prolonging Room-Temperature Phosphorescence of Crown Ethers by Supramolecular Interactions.

Angew Chem Int Ed Engl 2020 Jun 20;59(24):9293-9298. Epub 2019 Nov 20.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, and Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

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 was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10-fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials.
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http://dx.doi.org/10.1002/anie.201912155DOI Listing
June 2020

Unusual Through-Space Interactions between Oxygen Atoms that Mediate Inverse Morphochromism of an AIE Luminogen.

Angew Chem Int Ed Engl 2020 May 20;59(22):8552-8559. Epub 2019 Nov 20.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

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.
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http://dx.doi.org/10.1002/anie.201908573DOI Listing
May 2020

Tandem crystallization strategies for resolution of 3,3,3-trifluorolactic acid [CF CH(OH)COOH] by chiral benzylamines.

Chirality 2019 11 30;31(11):979-991. Epub 2019 Sep 30.

Department of Chemistry, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.

Resolution of rac-3,3,3-trifluorolactic acid by diastereomeric salt formation was reinvestigated. The use of (S)-1-phenylethylamine gives coprecipitation of two diastereomeric phases, 1 (S)-[NH CH(CH )Ph](S)-[CF CH(OH)COO] and 2 (S)-[NH CH(CH )Ph](R)-[CF CH(OH)COO]·H O. Pure phase 1 may be obtained using molecular sieves as desiccants. Resolution by (S,S)-2-amino-1-phenylpropan-1,3-diol gives monoclinic (S,S)-[NH CH(CH OH)CHOHPh] (R)-[CF CH(OH)-COO] 3 with minor (S)-3,3,3-trifluorolactate contamination, which is precluded in the recrystallized orthorhombic form 4. A new resolution using inexpensive phenylglycinol gives pure phase 5 (S)-[NH CH(CH OH)Ph] (S)-[CF CH(OH)COO] in 76% yield, 94% ee in a single step, in preference to its (S)-(R) diastereomer 6. Overall efficient resolution for both enantiomers of the trifluorolactic acid (each ca. 70% yield, 99% ee) may be achieved by various two-step "tandem" crystallizations, involving direct addition of either water or a second base to the filtrate from the initial reaction.
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http://dx.doi.org/10.1002/chir.23127DOI Listing
November 2019

Time-Dependent Photodynamic Therapy for Multiple Targets: A Highly Efficient AIE-Active Photosensitizer for Selective Bacterial Elimination and Cancer Cell Ablation.

Angew Chem Int Ed Engl 2020 06 22;59(24):9470-9477. Epub 2019 Oct 22.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering., Research Center for Tissue Restoration and Reconstruction, Institute of Molecular Functional Materials, State Key Laboratory of Molecular Nanoscience, Division of Life Science and Department of Chemical and Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

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 , 4TPA-BQ shows a satisfactorily high O generation efficiency of 97.8 %. In vitro and in vivo experiments confirmed that 4TPA-BQ exhibited potent photodynamic antibacterial performance against ampicillin-resistant Escherichia coli with good biocompatibility in a short time (15 minutes). When the incubation duration persisted long enough (12 hours), cancer cells were ablated efficiently, leaving normal cells essentially unaffected. This is the first reported time-dependent fluorescence-guided photodynamic therapy in one individual PS, which achieves ordered and multiple targeting simply by varying the external conditions. 4TPA-BQ reveals new design principles for the implementation of efficient PSs in clinical applications.
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http://dx.doi.org/10.1002/anie.201909706DOI Listing
June 2020
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