PART I: FIELD DESORPTION MASS SPECTROMETRY OF ALKALI METAL CRYPTATES. PART II: STEREOCHEMICAL DIFFERENTIATION OF ALCOHOL DERIVATIVES BY VARIOUS MASS SPECTROMETRIC TECHNIQUES.

Part I. Field desorption (FD) mass spectra have been obtained from a series of alkali metal cryptates formed from {2.2.2}-, {2.2.1}- and {2.1.1}-cryptands with Li(\u27+), Na(\u27+) and K(\u27+) salts of Cl(\u27-), Br(\u27-), I(\u27-), OTs(\u27-) and BPh(,4)(\u27-). Stabilities of these complexes under FD conditions are compared with their thermodynamic stabilities in solution. Differences in these stabilities are attributed to the lack of solvation of ions under FD conditions. A marked anion effect is also observed in FD spectra. This effect is correlated with the recombination energy of the released cation and anion in the gaseous state. Part II. Acid phthalates from isomeric alicyclic alcohols have been studied by field desorption (FD) and electron impact (EI) mass spectrometry. Isomeric acid phthalates gave identical FD spectra and EI spectra. The use of these methods for distinguishing stereoisomers of this type thus proved to be unsuccessful. However, the field ionization (FI) spectra of cis- and trans-4-t-butylcyclohexyl 9-fluorenylmethyl carbonate show distinguishing features. The trans-isomer undergoes a rearrangement reaction which involves mainly the transfer of the benzylic hydrogen to carbonyl oxygen, whereas the cis-isomer transfers either the benzylic hydrogen or a readily available hydrogen from the 2-position in the cyclohexyl ring. This divided pathway gives rise to an additional ion for the cis-isomer (m/z 138) which is the major qualitative difference in the spectra. The EI spectra for both isomers are simple and closely related to each other. Source: Dissertation Abstracts International, Volume: 42-08, Section: B, page: 3262. Thesis (Ph.D.)--University of Windsor (Canada), 1981

The epidemiology of COVID-19 cases and the successful containment strategy in Hong Kong-January to May 2020

BACKGROUND: Hong Kong, a Special Administrative Region of China, recorded its first confirmed coronavirus disease 2019 (COVID-19) case on 23 January 2020. We reviewed the case epidemiology and the various public health measures implemented from January to May 2020. METHODS: The epidemiological and clinical characteristics of the cases recorded in different phases of the epidemic were described and compared, and the effectiveness of the public health measures implemented were reviewed using the changes in the daily number of confirmed cases and the interval from symptom onset to hospital admission. RESULTS: Between January and May 2020, 1084 confirmed COVID-19 cases were reported, about 70% of which had a history of travel during the incubation period. The case fatality ratio was 0.4%. The local epidemic progressed through four phases: (1) preparedness and imported infection from mainland China, (2) local transmission, (3) imported infection from overseas countries associated with local transmission, and (4) controlled imported infection with limited local transmission, with an eventual reduction of the daily case number and minimization of the onset-to-admission interval. Various public health measures, including enhanced surveillance, border control, and social distancing, were introduced in phases in response to the prevailing local and global situations. DISCUSSION: The overall containment strategy in Hong Kong led to a stabilization of the number of cases and the absence of a community-wide outbreak during the 4.5 m after the first case was reported. This strategy of containment might serve as an example for future planning of preparedness and response against novel infectious agents

Frequency Doubled CO₂Laser Induced Decomposition of Carbonyl Compounds:Cyclobutanone

This paper reports the first use of radiation derived from a TEA carbon dioxide laser by nonlinear upshifting techniques (second harmonic generation) in initiating multiphoton absorption and dissociation. The frequency doubled CO2 laser has frequency coverage from 2180–1750 cm–1. This frequency region is of importance as it allows pumping of the fundamental stretching modes of organic carbonyl groups (anhydrides, acyl chlorides and strained cyclic ketones), inorganic carbonyl groups, and carbontritium bonds. The laser has been used to excite cyclobutanone in the region of the carbonyl stretch. Efficient multiphoton absorption and two channel dissociation are observed. The product array is consistent with that observed upon excitation at 10 μm

Functionalized Bis-Cyclometalated Alkynylgold(III) Complexes: Synthesis, Characterization, Electrochemistry, Photophysics, Photochemistry, and Electroluminescence Studies

A series of luminescent alkynylgold­(III) complexes containing various tridentate bis-cyclometalating ligands derived from 2,6-diphenylpyridine (R-C^∧N^∧C), [Au­(R-C^∧N^∧C)­(CCC₆H₄R′)] has been successfully synthesized and characterized. Complexes <b>1</b> and <b>6</b> have been determined by X-ray crystallography. Electrochemical studies show a ligand-centered reduction that originated from the tridentate R-C^∧N^∧C pincer ligands and an alkynyl-centered oxidation. The photophysical properties of the complexes have been studied in detail by electronic absorption and emission studies. Tunable photoluminescence behaviors have been observed, with the emission maxima spanning through the visible region from 476 to 669 nm in dichloromethane at room temperature, and the complexes were also found to be emissive in various media at both room and low temperatures. Transient absorption studies have been conducted to investigate the excited state properties of the complexes. Furthermore, selected complexes have been incorporated into the emissive layer (EML) of organic light-emitting devices (OLEDs) and have demonstrated interesting electroluminescence

Functionalized Bis-Cyclometalated Alkynylgold(III) Complexes: Synthesis, Characterization, Electrochemistry, Photophysics, Photochemistry, and Electroluminescence Studies

A series of luminescent alkynylgold­(III) complexes containing various tridentate bis-cyclometalating ligands derived from 2,6-diphenylpyridine (R-C^∧N^∧C), [Au­(R-C^∧N^∧C)­(CCC₆H₄R′)] has been successfully synthesized and characterized. Complexes <b>1</b> and <b>6</b> have been determined by X-ray crystallography. Electrochemical studies show a ligand-centered reduction that originated from the tridentate R-C^∧N^∧C pincer ligands and an alkynyl-centered oxidation. The photophysical properties of the complexes have been studied in detail by electronic absorption and emission studies. Tunable photoluminescence behaviors have been observed, with the emission maxima spanning through the visible region from 476 to 669 nm in dichloromethane at room temperature, and the complexes were also found to be emissive in various media at both room and low temperatures. Transient absorption studies have been conducted to investigate the excited state properties of the complexes. Furthermore, selected complexes have been incorporated into the emissive layer (EML) of organic light-emitting devices (OLEDs) and have demonstrated interesting electroluminescence

Bipolar Gold(III) Complexes for Solution-Processable Organic Light-Emitting Devices with a Small Efficiency Roll-Off

Poster: no. 12A new class of bipolar alkynylgold(III) complexes containing triphenylamine and benzimidazole moieties has been synthesized and fully characterized. The incorporation of methyl groups in the central phenyl unit has been found to rigidify the molecule to reduce non-radiative decay, yielding a high photoluminescence quantum yield of up to 75 % in spin-coated thin films. More importantly, this class of alkynylgold(III) complexes exhibits excellent solubility in various organic solvents and is capable of serving as phosphorescent dopants in the fabrication of solution-processable organic lightemitting devices (OLEDs). Efficient solution-processable OLEDs with high external quantum efficiency (EQE) of up to 10 % and an extremely small efficiency roll-off of less than 1 % at a practical brightness of 1000 cd m–2 have been demonstrated.published_or_final_versio