RESUMO
By performing density functional theory (DFT) calculations, we investigated and identified the fundamental pathway for N-heterocyclic carbene (NHC)-catalyzed synthesis of axially chiral benzothiophene-fused biaryls using enal and 2-benzyl-benzothiophene-3-carbaldehyde, which includes (1) nucleophilic attack on enal by the organocatalyst NHC, (2) [1,2]-proton transfer, (3) oxidation, (4) stereoselective formation of the C-C σ bond, (5) intramolecular [2 + 2] cycloaddition, (6) dissociation of NHC, (7) release of CO2, and (8) transformation to axial chirality. Moreover, the calculated results can reasonably explain the observed chemo- and stereoselectivities for the formation of both benzothiophene/benzofuran-fused biaryls in these kinds of reactions. Further non-covalent interaction (NCI) and atoms-in-molecules (AIM) analyses demonstrate that the hydrogen bond interactions are responsible for the stability of key stereoselective transition states. This work would be useful for understanding the origin of stereoselectivity of NHC-catalyzed intermolecular cyclization reactions for the synthesis of axially benzothiophene/benzofuran-fused biaryl compounds.
RESUMO
Along with the global spread of the COVID-19 pandemic, a number of hospitals are operating in the over-loaded state, which results in the ever-increasing requirements of cooling, heating, power, and medical gas supplies. This paper investigates a novel concept of hospital-oriented quad-generation (HOQG) to produce a combined cooling, heating, power and gas (CCHPG) system. Local renewable energy source (RES), high temperature superconducting (HTS) power cable and superconducting magnetic energy storage (SMES) device are used as the low-carbon electricity producer, carrier and regulator, respectively. Compared to the conventional copper cable and electrochemical battery, HTS terminal power units have superior advantages of high-efficiency power delivery and high-quality power compensation. To accommodate the surplus electricity from local RESs and guarantee emergency supply for the targeted hospital buildings, three cryogenic fluids of liquefied methane gas, liquefied oxygen and liquefied nitrogen are used as back-ups for both energy fuel and medical gas. By adopting a series of cascade energy utilization and thermally-activated energy conversion facilities, multiple clean energies of cooling, heating and power are produced to supply medical devices, and multiple medical gases of oxygen, nitrogen and carbon dioxide are delivered to hospitals for patient treatments. Compared to conventional diesel oil and compressed gas back-ups, these three cryogenic liquids have advantages of high-capacity, high-security storage and low-pollution utilization. Another possible benefit can be the low-temperature environment of these medical gases offers vaccines an appropriate delivering pathway against the COVID-19 pandemic. Therefore, the proposed HOQG can be expected to fulfill the demand of energy conservation and emission reduction simultaneously during the normal operation, as well as the demand of sustainable energy and medical gas supply under severe conditions such as natural and man-made disasters.
RESUMO
Smart window is a promising green technology with feature of tunable transparency under external stimuli to manage light transmission and solar energy. However, more functions based on the intelligent management of the solar spectrum need to be integrated into present smart windows. In this work, a dual-function smart window is fabricated by pairing the luminescent switch with the electrochromic window. The dual function is based on a single fluorine doped tin oxide coated glass functionalized with tungsten oxide and copper nanocluster, among which tungsten oxide serves as an electrochromic material and copper nanocluster provides photoinduced luminescence. Along with the regulation of the visible light based on the electrochromism of the window, the luminescence can be finely switched on and off, which establishes a pair of reversible states ("on" and "off") for the dual-function smart window. The contrast between two states reaches 88%. Furthermore, the manipulation of dual-function smart window is highly reversible with a short response time of 12.6 s. This prototype of dual-function smart window paves the way for developing multifunctional smart windows by integrating different functional materials into one smart window based on the rational management of the solar spectrum.
