Research projects within Ottosson group

Development of selective chemistry with silenes, Si=C double bonded compounds

Focus is given to silenes with reversed Si=C bond polarities (Sið-=Cð+) as these, for example, give higher chemoselectivity in reactions with (hetero)dienes than naturally polarized (Sið+=Cð-) silenes. The goal is applications of these reactions in selective organic synthesis. Applications of Si=C bonded compounds in molecular electronics are also being examined.

Structure and reactivity of Si=C bonded compounds

Development of the organic chemistry of Si=C double bonded compounds for selective (target-directed) organic synthesis, in particular developing the Diels-Alder reaction with silenes.

Key publications

• The First Intramolecular Silene Diels-Alder Reactions, M. Czyzewski, J. D. Sellars, T. Guliashvili, J. Tibbelin, L. Johnstone, J. Bower, M. Box, H. Ottosson, P. G. Steel, Chem. Commun. 2014, 50, 2919 - 2921.
• A Computational Investigation of Brook-type Silabenzenes and Their Possible Formation through [1,3]-Si→O Silyl Shifts, A. M. Rouf, B. O. Jahn, H. Ottosson, Organometallics, 2013, 32, 16 – 28.
• Silenes: Connectors Between Classical Alkenes and Non-Classical Heavy Alkenes, H. Ottosson, A. M. Eklöf, Coord. Chem. Rev. 2008, 252, 1287 – 1314.

Aromaticity effects in electronically excited states

In this project area we exploit the reversal of the electron counting rules for aromaticity and antiaromaticity in the lowest triplet and singlet pp* excited states annulenes as compared to their electronic ground state. We have shown that a series of properties are varied through the mutual change in ground and lowest excited state aromaticity.

Excited state aromaticity and antiaromaticity effects (Baird's rule)

Pioneering the usage of Baird’s rule on excited state (anti)aromaticity for (i) the rationalization of a range of photophysical and photochemical properties and processes, (ii) the design of new optically and photochemically active compounds, and (iii) the development of new photochemical reactions.

Key publications

• Impact of Ground and Excited State Aromaticity on Silole and Cyclopentadiene Excitation Energies and Excited State Polarities, K. Jorner, R. Emanuelsson, C. Dahlstrand, H. Tong, A. V. Denisova, H. Ottosson, Chem. Eur. J. 2014, 20, 9295 – 9303.
• Excited State Aromaticity and Antiaromaticity: Opportunities for Photophysical and Photochemical Rationalization, M. Rosenberg, C. Dahlstrand, K. Kilså, H. Ottosson, Chem. Rev. 2014, 114, 5379 – 5425.
• Exciting Excited-State Aromaticity, H. Ottosson, Nat. Chem., 2012, 4, 969-971 (a News & Views article)

Novel conjugation phenomena

Design and synthesis of compounds that display new forms of conjugation, incorporating heavier group 14 elements such as silicon and germanium into the organic framework. Present focus is on merging the cross-conjugation and hyperconjugation concepts.

Publications

• 1,4-Disilacyclohexa-2,5-diene: A Cyclic Molecular Building Block that Allows for Remarkably Strong Neutral Cross-Hyper-conjugation, J. Tibbelin, A. Wallner, R. Emanuelsson, F. Heikenskjöld, M. Rosenberg, K. Yamazaki, D. Nauroozi, L. Karlsson, R. Feifel, R. Pettersson, J. Baumgartner, S. Ott, H. Ottosson, Chem. Sci. 2014, 5, 360 - 371.
• Charge Transfer Through Cross-Hyperconjugated versus Cross-pi-Conjugated Bridges: An Intervalence Charge Transfer Study, E. Göransson, R. Emanuelsson, K. Jorner, T. F. Markle, L.Hammarström, H. Ottosson, Chem. Sci. 2013, 4, 3522 - 3532.
• Cross-Hyperconjugation: An Unexplored Orbital Interaction between pi-Conjugated and Saturated Molecular Fragments, R. Emanuelsson, A. Wallner, E. A. M. Ng, J. R. Smith, D. Nauroozi, S. Ott, H. Ottosson, Angew. Chem. Int. Ed., 2013, 52, 983 – 987.

Molecular electronics

Design and synthesis of organosilicon compounds with targeted properties for applications in single-molecule electronics.

With focus on charge transport through compounds with unusual conjugation topologies, and in collaborations within the U3MEC constellation lead by Dr. Ottosson, development of new rigid molecular junction set-ups, novel anchor groups, and much more.

Publications

• The Dicyanopentafulvene Core: A Template for the Design of Electron Acceptor Compounds, A. D. Finke, B. O. Jahn, A. Saithalavi, D. Nauroozi, S. Haberland, E. Mijangos, J.-P. Gisselbrecht, C. Boudon, W. B. Schweizer, S. Ott, H. Ottosson, F. Diederich, Chem. – Eur. J. 2015, accepted.
• Configuration- and Conformation-Dependent Electronic Structure Variations in 1,4-Disubstituted Cyclohexanes Enabled by a Carbon-to-Silicon Exchange, R. Emanuelsson, H. Löfås, A. Wallner, D.Nauroozi, J. Baumgartner, C. Marschner, R. Ahuja, S. Ott, A. Grigoriev, H. Ottosson, Chem. Eur. J. 2014, 20, 9304 – 9311.
• In Search of Flexible Molecular Wires with Near Conformer-Independent Conjugation and Conductance: A Computational Study, R. Emanuelsson, H. Löfås, J. Zhu, R. Ahuja, A. Grigoriev, H. Ottosson, J. Phys. Chem. C, 2014, 118, 5637 - 5349.