An official website of the United States government
The structures of a series of 2:1 cocrystals formed between 4-(dimethylamino)pyridine and each of 1,2,4,5-tetrachloro-3,6-diiodobenzene, 2C7H10N2·C6Cl4I2, 1,2,4,5-tetrabromo-3,6-diiodobenzene, 2C7H10N2·C6Br4I2, 1-bromo-4-iodo-2,3,5,6-tetrafluorobenzene, 2C7H10N2·C6BrF4I, and 1,2-dibromo-4,5-difluoro-3,6-diiodobenzene, 2C7H10N2·C6Br2F2I2, are reported. In all five structures, the core halogen-bonded 2:1 trimolecular units have geometrically similar parameters, with the central halogen-bond donor flanked by two pyridine halogen-bond acceptors twisted with respect to the central halogen-bond donor at angles ranging from 76 to 86°. The I...N halogen-bond separations are all short, ranging from 73.3 to 76.7% of the sum of the van der Waals radii, while the C—I...N bond angles are essentially linear. The Br...N halogen-bond separation in the cocrystal formed with 1-bromo-4-iodo-2,3,5,6-tetrafluorobenzene is 80.4% of the sum of the van der Waals radii. Subtle differences in the crystal packings are attributed to the role of secondary C—H...π and weak π-type interactions with chloro and bromo substituents. The cocrystals 2C7H10N2·C6Cl4I2and 2C7H10N2·C6Br4I2are isomorphous.
more »
« less
Modeling estimates of agricultural and natural soil nitrous oxide emissions across the contiguous United States: Annual time-series gridded database during 1900-2019
This dataset includes the time-series maps of the model-estimated N2</sub>O emissions, covering the lower U.S. spanning from 1900 to 2019.
more »
« less
- PAR ID:
- 10336602
- Publisher / Repository:
- figshare
- Date Published:
- Subject(s) / Keyword(s):
- Environmental Science
- Format(s):
- Medium: X Size: 134650813 Bytes
- Size(s):
- 134650813 Bytes
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract High‐temperature, high‐velocity water vapor (steam‐jet) exposures were conducted on Y2O3, Y2SiO5, Y2Si2O7, and SiO2for 60 hours at 1400°C. Volatility of Y2O3was not observed. Phase‐pure Y2SiO5exhibited SiO2loss forming Y2O3and porosity. A mixed porous and dense Y2SiO5layer formed on the surface of Y2Si2O7due to SiO2depletion. The mechanisms and kinetics of the reaction between SiO2and H2O(g) to form Si(OH)4(g) from Y2SiO5, Y2Si2O7, and SiO2are discussed.more » « less
-
Abstract The overarching goal of this study is to effect the elimination of platinum from adducts withcis–C≡C−Pt−C≡C‐ linkages, thereby generating novel conjugated polyynes. Thus, the bis(hexatriynyl) complextrans‐(p‐tol3P)2Pt((C≡C)3H)2is treated with 1,3‐diphosphines R2C(CH2PPh2)2to generate (R2C(CH2PPh2)2)2Pt((C≡C)3H)2(14; R=c,n‐Bu;e,p‐tolCH2). These condense with the diiodide complexes R2C(CH2PPh2)2PtI2(9 a,c) in the presence of CuI (cat.) and excess HNEt2to give the title macrocycles [(R2C(CH2PPh2)2)Pt(C≡C)3]4(16 c,e) as adducts of the byproduct [H2NEt2]+I−(30–66 %). DOSY NMR experiments establish that this association is maintained in solution, but NaOAc removes the ammonium salt. The bis(triethylsilylpolyynyl) complexes (n‐Bu2C(CH2PPh2)2)Pt((C≡C)nSiEt3)2(n=2, 3) are synthesized analogously to14 c. They react with I2at rt to give mainly the diiodide complex9 cand the coupling product Et3Si(C≡CC≡C)nSiEt3. The possibility of competing reactions giving IC≡C species is investigated. Analogous reactions of the Pt4C24macrocycle16 calso give9 c, but no sp13C NMR signals or mass spectrometric Cxz+ions (x=24–100) could be detected. It is proposed that some cyclo[24]carbon is generated, but then rapidly converts to other forms of elemental carbon. No cyclotetracosane (C24H48) is detected when this sequence is carried out in the presence of PtO2and H2.more » « less
-
Abstract Sodium superionic conductor (NASICON)‐type materials are getting more and more attention due to their high capacity and good cycling ability compared with other cathode materials in aqueous zinc ion batteries (AZIB). The present paper was to study the synthesis and electrochemical properties of two NASICON compounds of Na3V2(PO4)3and Na3V2(PO4)2F3and to understand the impacts of fluorine. Both Na3V2(PO4)3and Na3V2(PO4)2F3are synthesized by hydrothermal growth followed with annealing at 800°C in inert gas. With 3 mol/L Zn(CF3SO3)2in water as electrolyte, Na3V2(PO4)3offered a high storage capacity, while Na3V2(PO4)2F3demonstrated a high discharge voltage though low storage capacity. It was also found that the storage capacity of Na3V2(PO4)2F3increases with increased cycles; however, the compound undergoes a gradual phase transition. It is discussed possible approaches to attain both high discharge voltage and large capacity with good cycling stability.more » « less
-
The electrical properties of the entropy stabilized oxides: Zr6Nb2O17, Zr6Ta2O17, Hf6Nb2O17and Hf6Ta2O17were characterized. The results and the electrical properties of the products (i.e. ZrO2, HfO2, Nb2O5and Ta2O5) led us to hypothesize the A6B2O17family is a series of mixed ionic-electronic conductors. Conductivity measurements in varying oxygen partial pressure were performed on A6Nb2O17and A6Ta2O17.The results indicate that electrons are involved in conduction in A6Nb2O17while holes play a role in conduction of A6Ta2O17. Between 900 °C–950 °C, the charge transport in the A6B2O17system increases in Ar atmosphere. A combination of DTA/DSC and in situ high temperature X-ray diffraction was performed to identify a potential mechanism for this increase. In-situ high temperature X-ray diffraction in Ar does not show any phase transformation. Based on this, it is hypothesized that a change in the oxygen sub-lattice is the cause for the shift in high temperature conduction above 900 °C–950 °C. This could be:(i)Nb(Ta)4+- oxygen vacancy associate formation/dissociation,(ii)formation of oxygen/oxygen vacancy complexes(iii)ordering/disordering of oxygen vacancies and/or(iv)oxygen-based superstructure commensurate or incommensurate transitions. In-situ high temperature neutron diffraction up to 1050 °C is required to help elucidate the origins of this large increase in conductivity.more » « less
