Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Electron microscopy and Nanoengineering)ORCID iD: 0000-0003-1050-8441
AstraZeneca R&D, Med Chem KH471, S-43183 Molndal, Sweden.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
Show others and affiliations
2016 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723Article in journal (Refereed) Published
Abstract [en]

The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S0), becomes exergonic in the first triplet state (T1). This is in line with Baird’s rule, which tells that benzene is antiaromatic and destabilized in its T1 state and also in its first singlet excited state (S1), opposite to S0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T1-state benzene is excellent at H-atom abstraction, while COT, aromatic in the T1 and S1 states according to Baird’s rule, is unreactive. Remarkably, also CVD-graphene on SiO2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions.

Place, publisher, year, edition, pages
2016.
National Category
Chemical Sciences Chemical Engineering
Identifiers
URN: urn:nbn:se:uu:diva-303639DOI: 10.1038/ncomms12962ISI: 000385553900001PubMedID: 27708336OAI: oai:DiVA.org:uu-303639DiVA, id: diva2:972524
Funder
Wenner-Gren FoundationsSwedish Research CouncilKnut and Alice Wallenberg FoundationÅForsk (Ångpanneföreningen's Foundation for Research and Development)Magnus Bergvall Foundation
Available from: 2016-09-21 Created: 2016-09-21 Last updated: 2017-11-21Bibliographically approved
In thesis
1. Covalent Graphene Functionalization for the Modification of Its Physical Properties
Open this publication in new window or tab >>Covalent Graphene Functionalization for the Modification of Its Physical Properties
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Graphene, a two dimensional monolayer carbon sheet with the atoms tightly packed in a hexagonal lattice, has exhibited so many excellent properties, which enable graphene to break several material records with regard to carrier mobility, strength yield and thermal conductivity to name a few. Therefore, graphene has been placed as a potential candidate to allow truly next-generation material. Graphene is a zero band gap material, implying that an energy band gap around the Dirac point is supposed to be open to make graphene applicable as a semiconductor. Covalent bond graphene functionalization becomes an essential enabler to open the energy gap in graphene and extend graphene applications in electronics, while the densely packed hexagonal carbon atoms as well as the strong sp2 hybridization carbon-carbon bonds jointly result in a changeling topic of allowing graphene to be decorated with functional groups.

Here in this thesis, different routes to realize graphene functionalizations are implemented by using physical and chemical ways. The physical functionalization methods are the ion/electron beam induced graphene fluorination as well as local defect insertion and the chemical ways correspond to the photochemistry techniques to approach hydrogenation and hydroxypropylation of graphene. Furthermore, to incorporate graphene into devices, the tuning of mechanical properties of graphene is desired. Towards this aim, the structure modification of graphene is employed to investigate the nanometer size-effect of crystalline size of graphene on the mechanical properties, namely Young’s modulus and surface energy. In the process of the graphene hydrogenation project, we discovered a high yield way to synthesis high quality graphene nanoscroll (GNS). Interestingly, the GNS shows superadhesion property through our atomic force microscopy measurements. This superadhesion is around 6-order stronger than van der Waals interaction and even higher than the hydrogen bonding enhanced and solid/liquid interfaces.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 60
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1472
Keyword
graphene; functionalization; nanomechanical property, graphene nanoscroll
National Category
Materials Engineering Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-314176 (URN)978-91-554-9807-8 (ISBN)
Public defence
2017-03-17, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 23:15 (English)
Opponent
Supervisors
Available from: 2017-02-24 Created: 2017-01-30 Last updated: 2017-02-24
2. Development of Mild Methods for Selective Covalent Functionalization of Graphene
Open this publication in new window or tab >>Development of Mild Methods for Selective Covalent Functionalization of Graphene
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis discusses methods for the comparatively mild covalent functionalization of graphene. Several graphene models were investigated: polycyclic aromatic hydrocarbons (PAHs), chemical vapor deposition (CVD)-graphene on SiO2/Si substrate, graphite foil, graphite flakes, kish graphite and highly oriented pyrolytic graphite. The PAHs were viewed as graphene edge analogs with the following molecules representing different edge motifs: pyrene, perylene, benzo[a]pyrene, benzo[e]pyrene, triphenylene, acenapthylene, and anthracene.

Ozone was used in combination with different solvents to functionalize PAHs, graphite, and CVD-graphene on SiO2/Si. Ozonation in water or methanol resulted in trapping of the carbonyl oxide intermediate that was formed in the reaction, producing a variety of functional groups. Ozonation in hydrogen peroxide solution with sonication promoted radical formation, possibly resulting in edge-oxidation of graphite. The regioselectivity for addition reactions (ozonolysis) and electrophilic aromatic substitution reactions with graphene edges is discussed.

To achieve functionalization of the basal plane of graphite or graphene, white light irradiation was used in combination with several transfer hydrogenation reagents. Formic acid treatment under irradiation resulted in the expected hydrogenation, whereas iso-propanol treatment resulted in iso-propanol attachment to the graphene.

The developed methods provide opportunities for graphene functionalization without the need for metal based reagents or harsh conditions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 48
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1593
Keyword
Polycyclic aromatic hydrocarbons, graphene models, graphite, local ionization energy surfaces, graphene functionalization
National Category
Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-332004 (URN)978-91-513-0135-8 (ISBN)
Public defence
2017-12-14, A1:107a, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-11-21 Created: 2017-10-24 Last updated: 2018-03-07
3. Excited State Aromaticity and Antiaromaticity: Fundamental Studies and Applications
Open this publication in new window or tab >>Excited State Aromaticity and Antiaromaticity: Fundamental Studies and Applications
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The central theme of this thesis is the ability to tune various molecular properties by controlling and utilizing aromaticity and antiaromaticity in the lowest electronically excited states. This investigation is based on qualitative theory, quantum chemical (QC) calculations and experimental work.

Baird's rule tells that the π-electron count for aromaticity and antiaromaticity is reversed in the ππ* triplet (T1) state when compared to Hückel's rule for the singlet ground state. The excited state aromatic character of [4n]annulenes is probed by usage of two structural moieties, the cyclopropyl (cPr) group and the silacyclobutene (SCB) ring. The results of QC calculations and photoreactivity experiments showed that the cPr group and the SCB ring remained closed when attached to or fused with [4n]annulenes so as to preserve T1 aromatic stabilization. In contrast, both moieties ring-opened when attached to or fused with [4n+2]annulenes as a means for alleviation of T1 antiaromaticity. These two structural moieties are shown to indicate T1 aromatic character of [4n]annulenes except in a limited number of cases.

The T1 antiaromatic character of compounds with 4n+2 π-electrons was utilized for photo(hydro)silylations and photohydrogenations. QC calculations showed that due to T1 antiaromaticity, benzene is able to abstract hydrogen atoms from trialkylsilanes. The photoreactions occurred under mild conditions for benzene and certain polycyclic aromatic hydrocarbons. In contrast, COT was found to be unreactive under similar conditions.

It is further revealed that various properties of molecules can be tailored by rational design using Baird’s rule. Three modes of connectivity (linear, bent, and cyclic) of polycyclic conjugated hydrocarbons (PCH) were explored by DFT calculations. When the PCHs contain a central [4n]unit and 4nπ-electron perimeter, bent isomers have lower triplet state energies than linear ones due to increased T1 aromaticity in the bent isomers. With regard to the cyclic connectivity, macrocyclic compounds are designed by modifying the C20 monocycle through incorporation of monocyclic units (all-carbon as well as heterocyclic) and the impact of macrocyclic T1 aromaticity upon insertion of different units is examined through QC calculations. The results provide insights on excited state aromaticity in macrocyclic systems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 61
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1594
Keyword
Baird's rule, Clar's rule, Computational quantum chemistry, Excited state aromaticity, Excited state aromaticity indicators, Organic photochemistry, Polycyclic conjugated hydrocarbons
National Category
Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-332404 (URN)978-91-513-0138-9 (ISBN)
Public defence
2017-12-15, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2017-11-24 Created: 2017-10-27 Last updated: 2018-03-07

Open Access in DiVA

fulltext(1691 kB)259 downloads
File information
File name FULLTEXT01.pdfFile size 1691 kBChecksum SHA-512
c08b5c5868920ee36774f8210434b87698d4b58b9d53a4de1c8e6a60976b70d91e65e2d1cc47aa65b81e80abaaabf57e836f72f4d94fecd7d0fcf2a37ff4f5d0
Type fulltextMimetype application/pdf

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Papadakis, RaffaelloLi, HuLundstedt, AnnaJorner, KjellAyub, RabiaHaldar, SoumyajyotiDenisova, AleksandraZietz, BurkhardLindh, RolandSanyal, BiplabGrennberg, HelenaLeifer, KlausOttosson, Henrik
By organisation
Molecular BiomimeticsDepartment of Chemistry - BMCApplied Materials SciencesOrganic ChemistryMaterials TheoryTheoretical Chemistry
In the same journal
Nature Communications
Chemical SciencesChemical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 259 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 1130 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf