scholarly journals Dialing in Direct Air Capture of CO2 by Crystal Engineering of Bis-iminoguanidines

2020 ◽  
Author(s):  
Radu Custelcean ◽  
Neil J. Williams ◽  
Xiaoping Wang ◽  
Kathleen A. Garrabrant ◽  
Halie Martin ◽  
...  
Keyword(s):  
Crystal Engineering ◽  
Conformational Flexibility ◽  
Methyl Groups ◽  
Hydrogen Atoms ◽  
Structural Modifications ◽  
Air Capture ◽  
Relationship Study ◽  
Aqueous Solubilities ◽  
Carbonate Salts ◽  
Structure Properties

We report a structure-properties relationship study of DAC by crystallization of bis-iminoguanidine (BIG) carbonate salts. The study focuses on a series of basic BIG structures including the glyoxal-bis(iminoguanidine) prototype (GBIG) and its simple analogs methylglyoxal-bis(iminoguanidine) (MGBIG) and diacetyl-bis(iminoguanidine) (DABIG). We find that minor structural modifications in the molecular structure of GBIG, such as substituting one or two hydrogen atoms with methyl groups, result in major changes in the crystal structures, induced by the increased conformational flexibility and steric hindrance. As a result, the corresponding aqueous solubilities within the series increase significantly, leading in turn to enhanced DAC performances.

scholarly journals Dialing in Direct Air Capture of CO2 by Crystal Engineering of Bis-iminoguanidines

2020 ◽  
Author(s):  
Radu Custelcean ◽  
Neil J. Williams ◽  
Xiaoping Wang ◽  
Kathleen A. Garrabrant ◽  
Halie Martin ◽  
...  
Keyword(s):  
Crystal Engineering ◽  
Conformational Flexibility ◽  
Methyl Groups ◽  
Hydrogen Atoms ◽  
Structural Modifications ◽  
Air Capture ◽  
Relationship Study ◽  
Aqueous Solubilities ◽  
Carbonate Salts ◽  
Structure Properties

We report a structure-properties relationship study of DAC by crystallization of bis-iminoguanidine (BIG) carbonate salts. The study focuses on a series of basic BIG structures including the glyoxal-bis(iminoguanidine) prototype (GBIG) and its simple analogs methylglyoxal-bis(iminoguanidine) (MGBIG) and diacetyl-bis(iminoguanidine) (DABIG). We find that minor structural modifications in the molecular structure of GBIG, such as substituting one or two hydrogen atoms with methyl groups, result in major changes in the crystal structures, induced by the increased conformational flexibility and steric hindrance. As a result, the corresponding aqueous solubilities within the series increase significantly, leading in turn to enhanced DAC performances.

scholarly journals Effects of Alkyl-Substituted Polybenzoxazines on Tribological Properties of Non-Asbestos Composite Friction Materials

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 567
Author(s):  
Anun Wongpayakyotin ◽  
Chanchira Jubsilp ◽  
Sunan Tiptipakorn ◽  
Phattarin Mora ◽  
Christopher W. Bielawski ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Composite Materials ◽  
Coefficient Of Friction ◽  
Aromatic Amines ◽  
Underlying Structure ◽  
Methyl Groups ◽  
Friction Materials ◽  
Wear Rates ◽  
Structure Properties ◽  
Crosslink Densities

A series of substituted polybenzoxazines was synthesized and studied as binders in non-asbestos friction composite materials. The structures of the polybenzoxazines were varied in a systemic fashion by increasing the number and position of pendant alkyl (methyl) groups and was accomplished using the respective aromatic amines during the polymer synthesis step. By investigating the key thermomechanical and tribological characteristics displayed by the composite materials, the underlying structure-properties relationships were deconvoluted. Composite friction materials with higher thermomechanical and wear resistance properties were obtained from polybenzoxazines with relatively high crosslink densities. In contrast, polybenzoxazines with relatively low crosslink densities afforded composite friction materials with an improved coefficient of friction values and specific wear rates.

scholarly journals On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

Nano Research ◽  
2021 ◽  
Author(s):  
Xiushang Xu ◽  
Marco Di Giovannantonio ◽  
José I. Urgel ◽  
Carlo A. Pignedoli ◽  
Pascal Ruffieux ◽  
...  
Keyword(s):  
Carbon Nanomaterials ◽  
Graphene Nanoribbons ◽  
Gold Surface ◽  
Fine Tuning ◽  
Uniform Structure ◽  
Methyl Groups ◽  
Structural Modifications ◽  
Force Microscopy ◽  
Chemical Structures ◽  
Atomic Force

AbstractGraphene nanoribbons (GNRs) have potential for applications in electronic devices. A key issue, thereby, is the fine-tuning of their electronic characteristics, which can be achieved through subtle structural modifications. These are not limited to the conventional armchair, zigzag, and cove edges, but also possible through incorporation of non-hexagonal rings. On-surface synthesis enables the fabrication and visualization of GNRs with atomically precise chemical structures, but strategies for the incorporation of non-hexagonal rings have been underexplored. Herein, we describe the on-surface synthesis of armchair-edged GNRs with incorporated five-membered rings through the C-H activation and cyclization of benzylic methyl groups. Ortho-Tolyl-substituted dibromobianthryl was employed as the precursor monomer, and visualization of the resulting structures after annealing at 300 °C on a gold surface by high-resolution noncontact atomic force microscopy clearly revealed the formation of methylene-bridged pentagons at the GNR edges. These persisted after annealing at 340 °C, along with a few fully conjugated pentagons having singly-hydrogenated apexes. The benzylic methyl groups could also migrate or cleave-off, resulting in defects lacking the five-membered rings. Moreover, unexpected and unique structural rearrangements, including the formation of embedded heptagons, were observed. Despite the coexistence of different reaction pathways that hamper selective synthesis of a uniform structure, our results provide novel insights into on-surface reactions en route to functional, non-benzenoid carbon nanomaterials.

scholarly journals Electron-induced ionization of undeuterated and deuterated benzoic acid isopropyl esters and nicotinic acid isopropyl esters: Some implications for the mechanism of the McLafferty rearrangement

2019 ◽  
Vol 26 (1) ◽  
pp. 3-24
Author(s):  
Joachim Opitz ◽  
A Stephen K Hashmi ◽  
Burkhard Miehlich ◽  
Michael Wölfle
Keyword(s):  
Benzoic Acid ◽  
Nicotinic Acid ◽  
Ethyl Ester ◽  
Methyl Groups ◽  
Aliphatic Chain ◽  
Methyl Ethyl ◽  
Hydrogen Atoms ◽  
Isopropyl Esters ◽  
Mclafferty Rearrangement ◽  
Ester Chain

Electron ionization mass spectra, ionization, and appearance energies and bond energies (as dissociation energies) are reported for benzoic acid-1-methyl-ethyl ester (BAIPE), benzoic acid-1-deutero-1-methyl-ethyl ester (BAIPED1), benzoic acid-2,2,2-trideutero-1-trideuteromethyl-ethyl ester (BAIPED6) as well as nicotinic acid-1-methyl-ethyl ester (NAIPE), nicotinic acid-1-deutero-1-methyl-ethyl ester (NAIPED1), and nicotinic acid-2,2,2-trideutero-1-trideuteromethyl-ethyl ester (NAIPED6). Ionization energies of 9.39 eV for BAIPE, 9.40 eV for BAIPED1, 9.26 eV for BAIPED6 as well as 9.70 eV for NAIPE, 9.79 eV for NAIPED1, and 9.65 eV for NAIPED6 were determined. A gas-phase formation enthalpy of [Formula: see text] = (−4.10 ± 0.1) eV for BAIPE is calculated as well as [Formula: see text] = (−3.35 ± 0.1) eV for NAIPE. Molecular ions show two main fragmentation pathways. The first is a classical McLafferty rearrangement, characterized by the transfer of one γ-hydrogen atom from the isopropyl ester chain leading to the ions of the corresponding acid and neutral propene. The second is the double hydrogen transfer from the ester chain leading to the formation of the protonated acid and a C3H5√ allyl radical. For BAIPE, both hydrogen atoms originate from the methyl groups of the aliphatic chain with a probability of ≥98%, whereas the C-1-hydrogen is transferred with a probability of ≤2%. For NAIPE, both hydrogen atoms originate from the methyl groups of the aliphatic chain with a probability of 90%. Experimental proton affinities of PA = (8.75 ± 0.2) eV for benzoic acid and PA = (8.43 ± 0.2) eV for nicotinic acid are derived. For the protonation of the carbonyl group, B3LYP DFT calculations yielded PA = 8.66 eV for benzoic acid and PA = 8.41 eV for nicotinic acid. The overall fragmentation mechanism is explained with the initial formation of a 1,5-distonic ion by transfer of the first hydrogen. For the transfer of the second hydrogen, an intermediate ion/neutral complex is formulated.

Blue Emitting 3 π-2 Spiro Terfluorene-Indenofluorene Isomers: A Structure-Properties Relationship Study

2011 ◽  
Vol 17 (50) ◽  
pp. 14031-14046 ◽  
Author(s):  
Cyril Poriel ◽  
Joëlle Rault-Berthelot ◽  
Damien Thirion ◽  
Frédéric Barrière ◽  
Laurence Vignau
Keyword(s):  
Relationship Study ◽  
Structure Properties

Structure-Properties Relationship Study in GaP/GaOx Core-shell Nanowires and Nanochains Based Nanodevices

2012 ◽  
Vol 18 (S2) ◽  
pp. 1858-1859
Author(s):  
Y. Li ◽  
W. Zhou
Keyword(s):  
Core Shell ◽  
Relationship Study ◽  
Shell Nanowires ◽  
Structure Properties

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

scholarly journals Direct air capture of CO2 via crystal engineering

2021 ◽  
Author(s):  
Radu Custelcean
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Crystal Engineering ◽  
Perspective View ◽  
Direct Air Capture ◽  
Air Capture

This article presents a perspective view of the topic of direct air capture (DAC) of carbon dioxide and its role in mitigating climate change, focusing on a promising approach to...

Site of H Atom Attack on Uracil and Its Derivatives in Aqueous Solution

1985 ◽  
Vol 40 (3-4) ◽  
pp. 292-294 ◽  
Author(s):  
Suresh Das ◽  
David J. Deeble ◽  
Clemens von Sonntag
Keyword(s):  
Aqueous Solution ◽  
Double Bond ◽  
Pulse Radiolysis ◽  
Hydrogen Abstraction ◽  
Methyl Groups ◽  
Oh Radicals ◽  
Hydrogen Atoms ◽  
Sugar Moiety ◽  
Reducing Properties

Hydrogen atoms from the radiolysis of water at pH 1.6 add to the 5,6-double bond of pyrimidines. The preferen­tial site of attack is the C(5) position (values in brackets) in the case of 6-methyluracil (87%), 1,3-dimethyluracil (71%), uracil (69%) and poly(U) (60%). This reaction yields a radical of reducing properties which can be monitored by its reaction with tetranitromethane in a pulse radiolysis experiment. In thymine (37%), thymidine (32%) and 1,3-dimethylthymine (25%) H-addition no longer pre­ferentially occurs at C(5), but addition is now mainly at C(6). Hydrogen abstraction from the methyl groups or the sugar moiety is negligible (≦ 5.5%). A comparison is made with literature values for the equivalent reactions of OH radicals.

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