uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 82) Show all publications
Yadav, S., El Bakouri, O., Jorner, K., Tong, H., Dahlstrand, C., Sola, M. & Ottosson, H. (2019). Exploiting the Aromatic Chameleon Character of Fulvenes for Computational Design of Baird-Aromatic Triplet Ground State Compounds. Chemistry - An Asian Journal, 14(10), 1870-1878
Open this publication in new window or tab >>Exploiting the Aromatic Chameleon Character of Fulvenes for Computational Design of Baird-Aromatic Triplet Ground State Compounds
Show others...
2019 (English)In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 14, no 10, p. 1870-1878Article in journal (Refereed) Published
Abstract [en]

Due to the reversal in electron counts for aromaticity and antiaromaticity in the closed-shell singlet state (normally ground state, S-0) and lowest * triplet state (T-1 or T-0), as given by Huckel's and Baird's rules, respectively, fulvenes are influenced by their substituents in the opposite manner in the T-1 and S-0 states. This effect is caused by a reversal in the dipole moment when going from S-0 to T-1 as fulvenes adapt to the difference in electron counts for aromaticity in various states; they are aromatic chameleons. Thus, a substituent pattern that enhances (reduces) fulvene aromaticity in S-0 reduces (enhances) aromaticity in T-1, allowing for rationalizations of the triplet state energies (E-T) of substituted fulvenes. Through quantum chemical calculations, we now assess which substituents and which positions on the pentafulvene core are the most powerful for designing compounds with low or inverted E-T. As a means to increase the -electron withdrawing capacity of cyano groups, we found that protonation at the cyano N atoms of 6,6-dicyanopentafulvenes can be a route to on-demand formation of a fulvenium dication with a triplet ground state (T-0). The five-membered ring of this species is markedly Baird-aromatic, although less than the cyclopentadienyl cation known to have a Baird-aromatic T-0 state.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
Baird's rule, excited state aromaticity, fulvenes, quantum chemistry, triplet state energies
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-389826 (URN)10.1002/asia.201801821 (DOI)000471307500040 ()30659757 (PubMedID)
Funder
Swedish Research CouncilCarl Tryggers foundation Wenner-Gren Foundations
Available from: 2019-07-29 Created: 2019-07-29 Last updated: 2019-07-29Bibliographically approved
Toldo, J., El Bakouri, O., Sola, M., Norrby, P.-O. & Ottosson, H. (2019). Is Excited-State Aromaticity a Driving Force for Planarization of Dibenzannelated 8 Π-Electron Heterocycles?. Paper presented at 18th International Symposium on Novel Aromatic Compounds (ISNA), 2019, Sapporo, JAPAN. CHEMPLUSCHEM, 84(6), 712-721
Open this publication in new window or tab >>Is Excited-State Aromaticity a Driving Force for Planarization of Dibenzannelated 8 Π-Electron Heterocycles?
Show others...
2019 (English)In: CHEMPLUSCHEM, ISSN 2192-6506, Vol. 84, no 6, p. 712-721Article in journal (Refereed) Published
Abstract [en]

Compounds with dibenzannelated heterocycles with eight pi-electrons are found in a range of applications. These molecules often adopt a bent structure in the ground state (S-0) but can become planar in the first excited states (S-1 and T-1) because of the cyclically conjugated 4n pi central ring, which fulfils the requirements for excited state aromaticity. We report on a quantum chemical investigation of the aromatic character in the S-1 and T-1 states of dibenzannelated seven- and six-membered heterocycles with one, two, or three heteroatoms in the 8 pi-electron ring. These states could have pi pi* or n pi* character. We find that compounds with one or two heteroatoms in the central ring have pi pi* states as their S-1 and T-1 states. They are to a significant degree influenced by excited state aromaticity, and their optimal structures are planar or nearly planar. Among the heteroatoms, nitrogen provides for the strongest excited state aromaticity whereas oxygen provides for the weakest, following the established trend of the S-0 state. Yet, dibenzannelated seven-membered-ring compounds with N=N bonds have non-aromatic n pi* states with strongly puckered structures as their S-1 and T-1 states.

Keywords
aromaticity, Baird's rule, dibenzannelated heterocycles, excited states, quantum chemical calculations
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-389613 (URN)10.1002/cplu.201900066 (DOI)000470922000022 ()
Conference
18th International Symposium on Novel Aromatic Compounds (ISNA), 2019, Sapporo, JAPAN
Funder
Vinnova, 2016-04572Stiftelsen Olle Engkvist Byggmästare, 184-390Wenner-Gren Foundations, UPD2017-0243
Available from: 2019-07-22 Created: 2019-07-22 Last updated: 2019-07-22Bibliographically approved
Dreos, A., Jorner, K., Borjesson, K., Wang, Z., Ottosson, H. & Moth-Poulsen, K. (2018). Norbornadiene-quadricyclane photochromic systems for solar energy storage applications and testing in devices. Paper presented at 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, USA.. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Norbornadiene-quadricyclane photochromic systems for solar energy storage applications and testing in devices
Show others...
2018 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Washington, D.C.: American Chemical Society (ACS), 2018
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-368923 (URN)000435539900027 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, USA.
Note

Meeting Abstract: 26

Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Poon, J.-f., Yan, J., Jorner, K., Ottosson, H., Donau, C., Singh, V. P., . . . Engman, L. (2018). Substituent Effects in Chain-Breaking Aryltellurophenol Antioxidants. Chemistry - A European Journal, 24(14), 3520-3527
Open this publication in new window or tab >>Substituent Effects in Chain-Breaking Aryltellurophenol Antioxidants
Show others...
2018 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 14, p. 3520-3527Article in journal (Refereed) Published
Abstract [en]

2-Aryltellurophenols substituted in the aryltelluro or phenolic part of the molecule were prepared by lithiation of the corresponding O-THP-protected 2-bromophenol, followed by reaction with a suitable diaryl ditelluride and deprotection. In a two-phase system containing N-acetylcysteine as a co-antioxidant in the aqueous phase, all compounds quenched lipid peroxyl radicals more efficiently than α-tocopherol with 3 to 5-fold longer inhibition times. Compounds carrying electron donating para-substituents in the phenolic or aryltelluro part of the molecule showed the best results. The mechanism for quenching of peroxyl radicals was discussed in the light of calculated OH bond dissociation energies, deuterium labeling experiments and studies of thiol-consumption in the aqueous phase. 

National Category
Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-329202 (URN)10.1002/chem.201704811 (DOI)000426764400024 ()29266496 (PubMedID)
Funder
Stiftelsen Olle Engkvist Byggmästare, 1016/159ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 16-364
Note

Poon, J. and Yan, J. are equally contributing.

Available from: 2017-09-10 Created: 2017-09-10 Last updated: 2018-05-22Bibliographically approved
Li, H., Papadakis, R., Jafri, S. H., Thersleff, T., Michler, J., Ottosson, H. & Leifer, K. (2018). Superior adhesion of graphene nanoscrolls. Communications Physics, 1, Article ID 44.
Open this publication in new window or tab >>Superior adhesion of graphene nanoscrolls
Show others...
2018 (English)In: Communications Physics, E-ISSN 2399-3650, Vol. 1, article id 44Article in journal (Refereed) Published
Abstract [en]

An emerging material in the carbon family, a graphene nanoscroll (GNS) is composed of tubularly scrolled monolayer graphene and has shown superlubricity and large current sustainability, surpassing the properties of monolayer graphene itself. Here we report on the superior adhesion of GNS prepared with a high yield synthesis method that allows for mass production of high quality GNSs. Raman spectra indicate that the GNS still maintains the signature of monolayer graphene, implying the lacking of pi-stacking between adjacent layers. Importantly, adhesion measurements using atomic force microscopy reveal these GNSs with height range of 120-130 nm show a 2.5-fold stronger adhesion force than pristine graphene. This result potentially indicates that the GNS has higher adhesion than monolayer graphene and even higher than the liquid-solid and hydrogen-bonding enhanced interfaces which are essential types of adhesions involved in the field of physical adhesions and thus, GNS could be a new candidate for super-strong and lightweight devices.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-362689 (URN)10.1038/s42005-018-0043-2 (DOI)000442027400001 ()
Funder
Knut and Alice Wallenberg FoundationWenner-Gren Foundations
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-05-06Bibliographically approved
DeFrancisco, J. R., Lopez-Espejo, G., Zafra, J. L., Yadav, S., Messersmith, R. E., Gomez-Garcia, C. J., . . . Tovar, J. D. (2018). Torsional Bias as a Strategy To Tune Single-triplet Gaps in Organic Diradicals. The Journal of Physical Chemistry C, 122(23), 12148-12157
Open this publication in new window or tab >>Torsional Bias as a Strategy To Tune Single-triplet Gaps in Organic Diradicals
Show others...
2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 23, p. 12148-12157Article in journal (Refereed) Published
Abstract [en]

Quinoidal compounds with proaromatic structures possess differing degrees of diradical character, where the open-shell diradical resonance form has restored aromaticity throughout the compound. Methods to tune the diradical character of these compounds have traditionally focused on altering the length and the molecular composition of the pi-conjugated backbones. However, other molecular design strategies to tune the singlet-triplet gap of pi-conjugated quinoidal molecules have not been extensively explored. We previously reported a strikingly small energy gap between the quinoidal and diradical states of a quinoidal small molecule containing methano[10]annulene (TMTQ) that was dictated in large part by the unusual aromaticity of the central annulene ring. Here, we report on two alkylated derivatives of TMTQthat present substantially different torsional biases to the planarity of the TMTQ pi-system. Using a combination of electronic and vibrational spectroscopies, magnetic measurements, and quantum chemical calculations, we demonstrate here how a steric effect rather than pi-electron compositional molecular engineering can dramatically narrow the singlet-triplet gap of a quinoidal compound to as small as -0.52 kcal/mol, determined experimentally. This study offers important insight for the continued development of open-shell diradical molecules that need not rely exclusively on the design of synthesis of new and complex conjugated systems.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-358520 (URN)10.1021/acs.jpcc.8b01905 (DOI)000435611900003 ()
Funder
Carl Tryggers foundation , CTS 14:369Carl Tryggers foundation , CTS 17:347
Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2018-10-05Bibliographically approved
Jorner, K., Jahn, B. O., Bultinck, P. & Ottosson, H. (2018). Triplet state homoaromaticity: concept, computational validation and experimental relevance. Chemical Science, 9(12), 3165-3176
Open this publication in new window or tab >>Triplet state homoaromaticity: concept, computational validation and experimental relevance
2018 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 9, no 12, p. 3165-3176Article in journal (Refereed) Published
Abstract [en]

Cyclic conjugation that occurs through-space and leads to aromatic properties is called homoaromaticity. Here we formulate the homoaromaticity concept for the triplet excited state (T1) based on Baird's 4n rule and validate it through extensive quantum-chemical calculations on a range of different species (neutral, cationic and anionic). By comparison to well-known ground state homoaromatic molecules we reveal that five of the investigated compounds show strong T1 homoaromaticity, four show weak homoaromaticity and two are non-aromatic. Two of the compounds have previously been identified as excited state intermediates in photochemical reactions and our calculations indicate that they are also homoaromatic in the first singlet excited state. Homoaromaticity should therefore have broad implications in photochemistry. We further demonstrate this by computational design of a photomechanical “lever” that is powered by relief of homoantiaromatic destabilization in the first singlet excited state.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Organic Chemistry Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-349228 (URN)10.1039/C7SC05009G (DOI)000428987200010 ()29732099 (PubMedID)
Funder
Swedish Research Council, 2015-04538Wenner-Gren FoundationsThe Royal Swedish Academy of Sciences
Available from: 2018-04-23 Created: 2018-04-23 Last updated: 2018-06-05Bibliographically approved
Denisova V, A., Tibbelin, J., Emanuelsson, R. & Ottosson, H. (2017). A Computational Investigation of the Substituent Effects on Geometric, Electronic, and Optical Properties of Siloles and 1,4-Disilacyclohexa-2,5-dienes. Molecules, 22(3), Article ID 370.
Open this publication in new window or tab >>A Computational Investigation of the Substituent Effects on Geometric, Electronic, and Optical Properties of Siloles and 1,4-Disilacyclohexa-2,5-dienes
2017 (English)In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 22, no 3, article id 370Article in journal (Refereed) Published
Abstract [en]

Thirty two differently substituted siloles 1a–1p and 1,4-disilacyclohexa-2,5-dienes 2a–2p were investigated by quantum chemical calculations using the PBE0 hybrid density functional theory (DFT) method. The substituents included σ-electron donating and withdrawing, as well as π-electron donating and withdrawing groups, and their effects when placed at the Si atom(s) or at the C atoms were examined. Focus was placed on geometries, frontier orbital energies and the energies of the first allowed electronic excitations. We analyzed the variation in energies between the orbitals which correspond to HOMO and LUMO for the two parent species, here represented as ΔεHL, motivated by the fact that the first allowed transitions involve excitation between these orbitals. Even though ΔεHL and the excitation energies are lower for siloles than for 1,4-disilacyclohexa-2,5-dienes the latter display significantly larger variations with substitution. The ΔεHL of the siloles vary within 4.57–5.35 eV (ΔΔεHL = 0.78 eV) while for the 1,4-disilacyclohexa-2,5-dienes the range is 5.49–7.15 eV (ΔΔεHL = 1.66 eV). The excitation energy of the first allowed transitions display a moderate variation for siloles (3.60–4.41 eV) whereas the variation for 1,4-disilacyclohexa-2,5-dienes is nearly doubled (4.69–6.21 eV). Cyclobutadisiloles combine the characteristics of siloles and 1,4-disilacyclohexa-2,5-diene by having even lower excitation energies than siloles yet also extensive variation in excitation energies to substitution of 1,4-disilacyclohexa-2,5-dienes (3.47–4.77 eV, variation of 1.30 eV).

National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-335095 (URN)10.3390/molecules22030370 (DOI)000398743500031 ()
Note

Title of manuscript in list of papers in Julius Tibbelin´s thesis: A comparative computational investigation of the substituent effects on geometric, electronic, and optical properties of 1,4-disilacyclo-hexa-2,5- dienes and siloles

Available from: 2017-11-30 Created: 2017-11-30 Last updated: 2018-02-16Bibliographically approved
Messersmith, R. E., Yadav, S., Siegler, M. A., Ottosson, H. & Tovar, J. D. (2017). Benzo[b]thiophene Fusion Enhances Local Borepin Aromaticity in Polycyclic Heteroaromatic Compounds. Journal of Organic Chemistry, 82(24), 13440-13448
Open this publication in new window or tab >>Benzo[b]thiophene Fusion Enhances Local Borepin Aromaticity in Polycyclic Heteroaromatic Compounds
Show others...
2017 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 24, p. 13440-13448Article in journal (Refereed) Published
Abstract [en]

This report documents the synthesis, characterization, and computational evaluation of two isomeric borepin-containing polycyclic aromatics. The syntheses of these two isomers involved symmetrical disubstituted alkynes that were reduced to Z-olefins followed by borepin formation either through an isolable stannocycle intermediate or directly from the alkene via the trapping of a transient dilithio intermediate. Comparisons of their magnetic, crystallographic, and computational characterization to literature compounds gave valuable insights about the aromaticity of these symmetrically fused [b,f]borepins. The fusion of benzo[b]thiophene units to the central borepin cores forced a high degree of local aromaticity within the borepin moieties relative to other known borepin-based polycyclic aromatics. Each isomer had unique electronic responses in the presence of fluoride anions. The experimental data demonstrate that the local borepin rings in these two compounds have a relatively high amount of aromatic character. Results from quantum chemical calculations provide a more comprehensive understanding of local and global aromatic characters of various rings in fused ring systems built upon boron heterocycles.

National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-337849 (URN)10.1021/acs.joc.7b02512 (DOI)000418392600048 ()29136463 (PubMedID)
Available from: 2018-01-05 Created: 2018-01-05 Last updated: 2018-05-18Bibliographically approved
Ayub, R., El Bakouri, O., Jorner, K., Sola, M. & Ottosson, H. (2017). Can Baird's and Clar's Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4n pi- and (4n+2)pi-Rings?. Journal of Organic Chemistry, 82(12), 6327-6340
Open this publication in new window or tab >>Can Baird's and Clar's Rules Combined Explain Triplet State Energies of Polycyclic Conjugated Hydrocarbons with Fused 4n pi- and (4n+2)pi-Rings?
Show others...
2017 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 82, no 12, p. 6327-6340Article in journal (Refereed) Published
Abstract [en]

Compounds that can be labeled as "aromatic chameleons" are pi-conjugated compounds that are able to adjust their pi-electron distributions so as to comply with the different rules of aromaticity in different electronic states. We used quantum chemical calculations to explore how the fusion of benzene rings onto aromatic chameleonic units represented by biphenylene, dibenbzocyclooctatetraene, and dibenzo[a,e]pentalene modifies the first triplet excited states (T-1) of the compounds. Decreases in T-1 energies are observed when going from isomers with linear connectivity of the fused benzene rings to those with cis- or transbent connectivities. The T-1 energies decreased down to those of the parent (isolated) 4n pi-electron units. Simultaneously, we observe an increased influence of triplet State aromaticity of the central 4n ring as given by Baird's rule and evidenced by geometric, magnetic, and electron density based aromaticity indices (HOMA, NICS-XY, ACID, and FLU). Because of an influence of,triplet state aromaticity in the central 4n pi-electron units,, the most stabilized, compounds, retain the triplet excitation in Baird pi-quartets or octets, enabling the outer benzene rings to adapt closed-shell singlet Clar pi-sextet character. Interestingly, the T-1 energies go down as the total number of aromatic cycles within a molecule in the T-1 state increases.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-329665 (URN)10.1021/acs.joc.7b00906 (DOI)000403854500031 ()28535673 (PubMedID)
Funder
Swedish Research Council
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2017-10-27Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8076-1165

Search in DiVA

Show all publications