Maximizing Property Tuning of Phosphorus Corrole Photocatalysts through a Trifluoromethylation Approach

Zhan, Xuan,Teplitzky, Peter,Diskin-Posner, Yael,Sundararajan, Mahesh,Ullah, Zakir,Chen, Qiu-Cheng,Shimon, Linda J. W.,Saltsman, Irena,Mahammed, Atif,Kosa, Monica,Baik, Mu-Hyun,Churchill, David G.,Gros ACS AMERICAN CHEMICAL SOCIETY 2019 Inorganic Chemistry Vol.58 No.9

<P>An eight-member series of CF<SUB>3</SUB>-substituted difluorophosphorus corroles was prepared for establishing a structure-activity profile of these high-potential photosensitizers. It consisted of preparing all four possible isomers of the monosubstituted corrole and complexes with 2-, 3-, 4-, and 5-CF<SUB>3</SUB> groups on the macrocycle’s periphery. The synthetic pathway to these CF<SUB>3</SUB>-substituted derivatives, beginning with (<B>tpfc</B>)<B>PF</B><SUB><B>2</B></SUB>, involves two different initial routes: (i) direct electrophilic CF<SUB>3</SUB> incorporation using FSO<SUB>2</SUB>CF<SUB>2</SUB>CO<SUB>2</SUB>Me and copper iodide, or (ii) bromination to achieve the 2,3,8,17,18-pentabrominated compound using excess bromine in methanol. Crystallographic investigations revealed that distortion of the original planar macrocycle is evident even in the monosubstituted case and that it becomes truly severe for the penta-CF<SUB>3</SUB>-substituted derivative <B>5</B>. There is a shift in redox potentials of about 193 mV per -CF<SUB>3</SUB> group, which decreases to only 120 mV for the fifth one in <B>5</B>. Differences in the electronic spectra suggest that the Gouterman four orbital model decreases in relevance upon gradual -CF<SUB>3</SUB> substitution, a conclusion that was corroborated by DFT calculations. The very significant energy lowering of the frontier orbitals suggested that photoexcitation should lead to a highly oxidizing photocatalyst. This hypothesis was proven true by finding that the most synthetically accessible CF<SUB>3</SUB>-substituted derivative is an excellent catalyst for the photoinduced conversion of bromide to bromine (phenol, toluene, and benzene assay).</P><P>CF<SUB>3</SUB>-substituted difluorophosphorus corroles were synthesized and studied by CV, NMR spectroscopy, crystallography, and DFT. All four possible isomers of the monosubstituted corrole and complexes with 2-, 3-, 4-, and 5-CF<SUB>3</SUB> groups on the macrocycle’s periphery were prepared. The sterical and electronic role of the -CF<SUB>3</SUB> unit became evident through the study of the 5-CF<SUB>3</SUB> species which was found to be an excellent bromide photocatalyst (photoxidation with phenol, toluene, and benzene assays).</P> [FIG OMISSION]</BR>

Evaluating high-resolution forecasts of atmospheric CO and CO₂ from a global prediction system during KORUS-AQ field campaign

Tang, Wenfu,Arellano, Avelino F.,DiGangi, Joshua P.,Choi, Yonghoon,Diskin, Glenn S.,Agustí,-Panareda, Anna,Parrington, Mark,Massart, Sebastien,Gaubert, Benjamin,Lee, Youngjae,Kim, Danbi,Jung, Ji Copernicus GmbH 2018 Atmospheric Chemistry and Physics Vol.18 No.15

<P><p><strong>Abstract.</strong> <span id='page11008'/>Accurate and consistent monitoring of anthropogenic combustion is imperative because of its significant health and environmental impacts, especially at city-to-regional scale. Here, we assess the performance of the Copernicus Atmosphere Monitoring Service (CAMS) global prediction system using measurements from aircraft, ground sites, and ships during the Korea-United States Air Quality (KORUS-AQ) field study in May to June 2016. Our evaluation focuses on CAMS CO and <span class='inline-formula'>CO₂</span> analyses as well as two higher-resolution forecasts (16 and 9<span class='thinspace'></span>km horizontal resolution) to assess their capability in predicting combustion signatures over east Asia. Our results show a slight overestimation of CAMS <span class='inline-formula'>CO₂</span> with a mean bias against airborne <span class='inline-formula'>CO₂</span> measurements of 2.2, 0.7, and 0.3<span class='thinspace'></span>ppmv for 16 and 9<span class='thinspace'></span>km <span class='inline-formula'>CO₂</span> forecasts, and analyses, respectively. The positive <span class='inline-formula'>CO₂</span> mean bias in the 16<span class='thinspace'></span>km forecast appears to be consistent across the vertical profile of the measurements. In contrast, we find a moderate underestimation of CAMS CO with an overall bias against airborne CO measurements of <span class='inline-formula'>−</span>19.2 (16<span class='thinspace'></span>km), <span class='inline-formula'>−</span>16.7 (9<span class='thinspace'></span>km), and <span class='inline-formula'>−</span>20.7<span class='thinspace'></span>ppbv (analysis). This negative CO mean bias is mostly seen below 750<span class='thinspace'></span>hPa for all three forecast/analysis configurations. Despite these biases, CAMS shows a remarkable agreement with observed enhancement ratios of CO with <span class='inline-formula'>CO₂</span> over the Seoul metropolitan area and over the West (Yellow) Sea, where east Asian outflows were sampled during the study period. More efficient combustion is observed over Seoul (<span class='inline-formula'><math xmlns='http://www.w3.org/1998/Math/MathML' id='M12' display='inline' overflow='scroll' dspmath='mathml'><mrow><mi mathvariant='normal'>d</mi><mrow class='chem'><mi mathvariant='normal'>CO</mi></mrow><mo>/</mo><mi mathvariant='normal'>d</mi><mrow class='chem'><msub><mi mathvariant='normal'>CO</mi><mn mathvariant='normal'>2</mn></msub></mrow><mo>=</mo><mn mathvariant='normal'>9</mn></mrow></math><span><svg:svg xmlns:svg='http://www.w3.org/2000/svg' width='77pt' height='14pt' class='svg-formula' dspmath='mathimg' md5hash='e15dbed157728345ac15fd0589ea867d'><svg:image xmlns:xlink='http://www.w3.org/1999/xlink' xlink:href='acp-18-11007-2018-ie00001.svg' width='77pt' height='14pt' src='acp-18-11007-2018-ie00001.png'/></svg:svg></span></span><span class='thinspace'></span>ppbv<span class='thinspace'></span>ppmv<span class='inline-formula'>⁻¹</span>) compared to the West Sea (<span class='inline-formula'><math xmlns='http://www.w3.org/1998/Math/MathML' id='M14' display='inline' overflow='scroll' dspmath='mathml'><mrow><mi mathvariant='normal'>d</mi><mrow class='chem'><mi mathvariant='normal'>CO</mi></mrow><mo>/</mo><mi mathvariant='normal'>d</mi><mrow class='chem'><msub><mi mathvariant='normal'>CO</mi><mn mathvariant='normal'>2</mn></msub></mrow><mo>=</mo><mn mathvariant='normal'>28</mn></mrow></math><span><svg:svg xmlns:svg='http://www.w3.org/2000/svg' width='83pt' height='14pt' class='svg-formula' dspmath='mathimg' md5hash='3be8931fd245903ba9a1c1d59edabca9'><svg:image xmlns:xlink='http://www.w3.org/1999/xlink' xlink:href='acp-18-11007-2018-ie00002.svg' width='83pt' height='14pt' src='acp-18-11007-2018-ie00002.png'/></svg:svg></span></span><span class='thinspace'></span>ppbv<span class='thinspace'></span>pp

Characteristics of greenhouse gas concentrations derived from ground-based FTS spectra at Anmyeondo, South Korea

Oh, Young-Suk,Kenea, S. Takele,Goo, Tae-Young,Chung, Kyu-Sun,Rhee, Jae-Sang,Ou, Mi-Lim,Byun, Young-Hwa,Wennberg, Paul O.,Kiel, Matthä,us,DiGangi, Joshua P.,Diskin, Glenn S.,Velazco, Voltaire A.,Gr Copernicus GmbH 2018 Atmospheric measurement techniques Vol.11 No.4

<P><p><strong>Abstract.</strong> Since the late 1990s, the meteorological observatory established in Anmyeondo (36.5382°<span class='thinspace'></span>N, 126.3311°<span class='thinspace'></span>E, and 30<span class='thinspace'></span>m above mean sea level) has been monitoring several greenhouse gases such as CO₂, CH₄, N₂O, CFCs, and SF₆ as a part of the Global Atmosphere Watch (GAW) Program. A high resolution ground-based (g-b) Fourier transform spectrometer (FTS) was installed at this observation site in 2013 and has been operated within the frame work of the Total Carbon Column Observing Network (TCCON) since August 2014. The solar spectra recorded by the g-b FTS cover the spectral range 3800 to 16<span class='thinspace'></span>000<span class='thinspace'></span>cm⁻¹ at a resolution of 0.02<span class='thinspace'></span>cm⁻¹. In this work, the GGG2014 version of the TCCON standard retrieval algorithm was used to retrieve total column average CO₂ and CH₄ dry mole fractions (XCO₂, XCH₄) and from the FTS spectra. Spectral bands of CO₂ (at 6220.0 and 6339.5<span class='thinspace'></span>cm⁻¹ center wavenumbers, CH₄ at 6002<span class='thinspace'></span>cm⁻¹ wavenumber, and O₂ near 7880<span class='thinspace'></span>cm⁻¹ ) were used to derive the XCO₂ and XCH₄. In this paper, we provide comparisons of XCO₂ and XCH₄ between the aircraft observations and g-b FTS over Anmyeondo station. A comparison of 13 coincident observations of XCO₂ between g-b FTS and OCO-2 (Orbiting Carbon Observatory) satellite measurements are also presented for the measurement period between February 2014 and November 2017. OCO-2 observations are highly correlated with the g-b FTS measurements (<i>r</i>² = 0.884) and exhibited a small positive bias (0.189<span class='thinspace'></span>ppm). Both data set capture seasonal variations of the target species with maximum and minimum values in spring and late summer, respectively. In the future, it is planned to further utilize the FTS measurements for the evaluation of satellite observations such as Greenhouse Gases Observing Satellite (GOSAT, GOSAT-2). This is the first report of the g-b FTS observations of XCO₂ species over the Anmyeondo station.</p> </P>