3 research outputs found
Computational and Experimental Study on Selective sp<sup>2</sup>/sp<sup>3</sup> or Vinylic/Aryl Carbon–Hydrogen Bond Activation by Platinum(II): Geometries and Relative Stability of Isomeric Cycloplatinated Compounds
Cyclometalating
ligands 6-(1-phenylethyl)-2,2′-bipyridine
(<b>L4</b>), 6-(1-phenylvinyl)-2,2′-bipyridine (<b>L5</b>), and 6-(prop-1-en-2-yl)-2,2′-bipyridine (<b>L6</b>) were synthesized by the Negishi coupling of 6-bromo-2,2′-bipyridine
with the corresponding organozinc reagents. The reaction of <b>L4</b> with K<sub>2</sub>PtCl<sub>4</sub> produced only the cycloplatinated
compound <b>4a</b> via sp<sup>2</sup> C–H bond activation.
The reactions of <b>L5</b> and <b>L6</b> produced exclusively
the cycloplatinated compounds <b>5b</b> and <b>6a</b>,
respectively, via vinylic C–H bond activation. DFT calculations
were performed on 12 possible cycloplatination products from the reaction
of <i>N</i>-alkyl-<i>N</i>-phenyl-2,2′-bipyridin-6-amine
(alkyl = methyl (<b>L1</b>), ethyl (<b>L2</b>), and isopropyl
(<b>L3</b>)) and <b>L4</b>–<b>L6</b>. The
results show that compounds <b>1b</b>–<b>3b</b> resulting from the sp<sup>3</sup> C–H bond activation of <b>L1</b>–<b>L3</b> are thermodynamic products, and
their relative stability is attributed to the planar geometry that
allows for a better conjugation. Similar reasoning also applies to
the stability of products from vinylic C–H bond activation
of <b>L5</b> and <b>L6</b>. The relative stability of
isomeric cycloplatinated compounds <b>4a</b> and <b>4b</b> may be due to the different strengths of C–Pt bonds. The
steric interaction is the major cause of severe distortion from a
planar coordination geometry in the cycloplatinated compounds, which
leads to instability of the corresponding cyclometalated products
and a higher kinetic barrier for C–H bond activation
Computational and Experimental Study on Selective sp<sup>2</sup>/sp<sup>3</sup> or Vinylic/Aryl Carbon–Hydrogen Bond Activation by Platinum(II): Geometries and Relative Stability of Isomeric Cycloplatinated Compounds
Cyclometalating
ligands 6-(1-phenylethyl)-2,2′-bipyridine
(<b>L4</b>), 6-(1-phenylvinyl)-2,2′-bipyridine (<b>L5</b>), and 6-(prop-1-en-2-yl)-2,2′-bipyridine (<b>L6</b>) were synthesized by the Negishi coupling of 6-bromo-2,2′-bipyridine
with the corresponding organozinc reagents. The reaction of <b>L4</b> with K<sub>2</sub>PtCl<sub>4</sub> produced only the cycloplatinated
compound <b>4a</b> via sp<sup>2</sup> C–H bond activation.
The reactions of <b>L5</b> and <b>L6</b> produced exclusively
the cycloplatinated compounds <b>5b</b> and <b>6a</b>,
respectively, via vinylic C–H bond activation. DFT calculations
were performed on 12 possible cycloplatination products from the reaction
of <i>N</i>-alkyl-<i>N</i>-phenyl-2,2′-bipyridin-6-amine
(alkyl = methyl (<b>L1</b>), ethyl (<b>L2</b>), and isopropyl
(<b>L3</b>)) and <b>L4</b>–<b>L6</b>. The
results show that compounds <b>1b</b>–<b>3b</b> resulting from the sp<sup>3</sup> C–H bond activation of <b>L1</b>–<b>L3</b> are thermodynamic products, and
their relative stability is attributed to the planar geometry that
allows for a better conjugation. Similar reasoning also applies to
the stability of products from vinylic C–H bond activation
of <b>L5</b> and <b>L6</b>. The relative stability of
isomeric cycloplatinated compounds <b>4a</b> and <b>4b</b> may be due to the different strengths of C–Pt bonds. The
steric interaction is the major cause of severe distortion from a
planar coordination geometry in the cycloplatinated compounds, which
leads to instability of the corresponding cyclometalated products
and a higher kinetic barrier for C–H bond activation
Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States
Organic
nitrates are an important aerosol constituent in locations
where biogenic hydrocarbon emissions mix with anthropogenic NO<sub><i>x</i></sub> sources. While regional and global chemical
transport models may include a representation of organic aerosol from
monoterpene reactions with nitrate radicals (the primary source of
particle-phase organic nitrates in the Southeast United States), secondary
organic aerosol (SOA) models can underestimate yields. Furthermore,
SOA parametrizations do not explicitly take into account organic nitrate
compounds produced in the gas phase. In this work, we developed a
coupled gas and aerosol system to describe the formation and subsequent
aerosol-phase partitioning of organic nitrates from isoprene and monoterpenes
with a focus on the Southeast United States. The concentrations of
organic aerosol and gas-phase organic nitrates were improved when
particulate organic nitrates were assumed to undergo rapid (Ï„
= 3 h) pseudohydrolysis resulting in nitric acid and nonvolatile secondary
organic aerosol. In addition, up to 60% of less oxidized-oxygenated
organic aerosol (LO-OOA) could be accounted for via organic nitrate
mediated chemistry during the Southern Oxidants and Aerosol Study
(SOAS). A 25% reduction in nitrogen oxide (NO + NO<sub>2</sub>) emissions
was predicted to cause a 9% reduction in organic aerosol for June
2013 SOAS conditions at Centreville, Alabama