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Surface-enhanced Raman scattering spectroscopy was used to study charge-transfer (CT) complexes between bis(18-crown-6) stilbene and bisammonium derivative of dipyridylethylene. Using model compounds it is shown that interactions of the ammonium groups with the crown ether moieties played a critical role in the CT complex formation by stabilizing the molecular complex.

Research has been conducted on styryl dyes which contain 15-crown-5 ether unit and a quinoline residue with sulfonatobenzyl or sulfonatoalkyl N-substituent. The synthesis of these dyes is described.

The triple oxygen isotope signature Δ17O in atmospheric CO2, also known as its "17O excess," has been proposed as a tracer for gross primary production (the gross uptake of CO2 by vegetation through photosynthesis). We present the first global 3‐D model simulations for Δ17O in atmospheric CO2 together with a detailed model description and sensitivity analyses. In our 3‐D model framework we include the stratospheric source of Δ17O in CO2 and the surface sinks from vegetation, soils, ocean, biomass burning, and fossil fuel combustion. The effect of oxidation of atmospheric CO on Δ17O in CO2 is also included in our model. We estimate that the global mean Δ17O (defined as Δ17O=ln(δ17O+1)−λRL·ln(δ18O+1) with λRL = 0.5229) of CO2 in the lowest 500 m of the atmosphere is 39.6 per meg, which is ∼20 per meg lower than estimates from existing box models. We compare our model results with a measured stratospheric Δ17O in CO2 profile from Sodankylä (Finland), which shows good agreement. In addition, we compare our model results with tropospheric measurements of Δ17O in CO2 from Göttingen (Germany) and Taipei (Taiwan), which shows some agreement but we also find substantial discrepancies that are subsequently discussed. Finally, we show model results for Zotino (Russia), Mauna Loa (United States), Manaus (Brazil), and South Pole, which we propose as possible locations for future measurements of Δ17O in tropospheric CO2 that can help to further increase our understanding of the global budget of Δ17O in atmospheric CO2. Key Points: This work presents a first view on possible spatial and temporal gradients of Δ17O in CO2 across the globeTropical, boreal, and Southern Hemisphere observations of Δ17O in CO2 could be of great interestWe implemented spatially and temporally explicit sources and sinks of Δ17O in CO2 in a 3‐D model framework [ABSTRACT FROM AUTHOR]

The description of the syntheses of two series of new styryl dyes incorporating thiacrown ether moieties (CSDs 3a-e, 4a-e) is provided. The photochromic properties of the CSDs are based on reversible trans-cis isomerization and [2+2]-photocycloaddition.

We present version 4.0gmdd of the atmospheric chemistry box model CAABA/MECCA which now includes a number of new features: (i) skeletal mechanism reduction, (ii) the MOM chemical mechanism for volatile organic compounds, (iii) an option to include reactions from the Master Chemical Mechanism (MCM) and other chemical mechanisms, (iv) updated isotope tagging, and (v) improved and new photolysis modules (JVAL, RADJIMT, DISSOC). Further, when MECCA is connected to a global model, the new feature of coexisting multiple chemistry mechanisms (PolyMECCA/CHEMGLUE) can be used. Additional changes have been implemented to make the code more user-friendly and to facilitate the analysis of the model results. Like earlier versions, CAABA/MECCA-4.0gmdd is a community model published under the GNU General Public License. [ABSTRACT FROM AUTHOR]

An important driver of climate change is stratospheric water vapor (SWV), which in turn is influenced by the oxidation of atmospheric methane (CH4). In order to parameterize the production of water vapor (H2O) from CH4 oxidation, it is often assumed that the oxidation of one CH4 molecule yields exactly two molecules of H2O. However, this assumption is based on an early study, which also gives evidence that this is not true at all altitudes. In the current study, we re-evaluate this assumption with a comprehensive systematic analysis using a state-of-the-art chemistry-climate model (CCM), namely the ECHAM/MESSy Atmospheric Chemistry (EMAC) model, and present three approaches to investigate the yield of H2O and hydrogen gas (H2) from CH4 oxidation. We thereby make use of the Module Efficiently Calculating the Chemistry of the Atmosphere (MECCA) in a box model and global model configuration. Furthermore, we use the kinetic chemistry tagging technique (MECCA-TAG) to investigate the chemical pathways between CH4, H2O and H2, by being able to distinguish hydrogen atoms produced by CH4 from H2 from other sources. We apply three approaches, which all agree that assuming a yield of 2 overestimates the production of H2O in the lower stratosphere (calculated as 1.5-1.7). Additionally, transport and subsequent photochemical processing of longer-lived intermediates (mostly H2) raise the local yield values in the upper stratosphere and lower mesosphere above 2 (maximum > 2.2). In the middle and upper mesosphere, the influence of loss and recycling of H2O increases, making it a crucial factor in the parameterization of the yield of H2O from CH4 oxidation. An additional sensitivity study with the Chemistry As A Boxmodel Application (CAABA) shows a dependence of the yield on the hydroxyl radical (OH) abundance. No significant temperature dependence is found. We focus representatively on the tropical zone between 23°S and 23°N. It is found in the global approach that presented results are mostly valid for midlatitudes as well. During the polar night, the method is not applicable. Our conclusions question the use of a constant yield of H2O from CH4 oxidation in climate modeling and encourage to apply comprehensive parameterizations that follow the vertical profiles of the H2O yield derived here and take the chemical H2O loss into account. [ABSTRACT FROM AUTHOR]

Abstract: The complex formation of bis(18‐crown‐6)stilbene (1) and its supramolecular donor‐acceptor complex with N,N′‐bis(ammonioethyl) 1,2‐di(4‐pyridyl)ethylene derivative (2) with alkali and alkaline‐earth metal perchlorates has been studied using absorption, steady‐state fluorescence, and femtosecond transient absorption spectroscopy. The formation of 1∙Mn+ and 1∙(Mn+)2 complexes in acetonitrile was demonstrated. The weak long‐wavelength charge‐transfer absorption band of 1·2 completely vanishes upon complexation with metal cations because of disruption of the pseudocyclic structure. The spectroscopic and luminescence parameters, stability constants, and 2‐stage dissociation constants were calculated. The initial stage of a recoordination process was found in the excited complexes 1∙M+ and 1∙(M+)2 (M = Li, Na). The pronounced fluorescence quenching of 1·2 is explained by very fast back electron transfer (τet = 0.397 ps). The structure of complex 1·2 was studied by X‐ray diffraction; stacked (1·2)m polymer in which the components were connected by hydrogen bonding and stacking was found in the crystal. These compounds can be considered as novel optical molecular sensors for alkali and alkaline‐earth metal cations. [ABSTRACT FROM AUTHOR]

We provide a comprehensive review of the proxy data on the 13C ∕ 12C ratios and uncertainties of emissions of reactive carbonaceous compounds into the atmosphere, with a focus on CO sources. Based on an evaluated set-up of the EMAC model, we derive the isotope-resolved data set of its emission inventory for the 1997–2005 period. Additionally, we revisit the calculus required for the correct derivation of uncertainties associated with isotope ratios of emission fluxes. The resulting δ13C of overall surface CO emission in 2000 of −(25. 2 ± 0. 7) ‰ is in line with previous bottom-up estimates and is less uncertain by a factor of 2. In contrast to this, we find that uncertainties of the respective inverse modelling estimates may be substantially larger due to the correlated nature of their derivation. We reckon the δ13C values of surface emissions of higher hydrocarbons to be within −24 to −27 ‰ (uncertainty typically below ±1 ‰), with an exception of isoprene and methanol emissions being close to −30 and −60 ‰, respectively. The isotope signature of ethane surface emission coincides with earlier estimates, but integrates very different source inputs. δ13C values are reported relative to V-PDB. [ABSTRACT FROM AUTHOR]

We provide a comprehensive review of the proxy data on the 13C/12C ratios and uncertainties of emissions of reactive carbonaceous compounds into the atmosphere, with a focus on CO sources. Based on an evaluated setup of the EMAC model, we derive the isotope-resolved dataset of its emission inventory for the 1997-2005 period. Additionally, we revisit the calculus required for the correct derivation of uncertainties associated with isotope ratios of emission fluxes. The resulting overall surface CO emission δ13C in 2000 of -(25.2 ± 0.7) ‰ is in line with the previous bottom-up estimates and a factor of two less uncertain. In contrast to this, we find that uncertainties of the respective inverse modelling estimates are substantially larger due to the correlated nature of their derivation. We reckon the δ13C values of surface emissions of higher hydrocarbons being within -24 ‰ to -27 ‰ (uncertainty typically below ±1 ‰), with an exception of isoprene emissions being close to -30 ‰. The isotope signature of ethane surface emission coincides with earlier estimates, however integrating very different source inputs. δ13C values are reported relative to V-PDB. [ABSTRACT FROM AUTHOR]