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

Direct link
BETA
Lunell, Sten
Alternative names
Publications (10 of 41) Show all publications
Lunell, S. (2009). Kvantkemi: kemi utan provrör. In: Annales Academiae regiae scientiarum Upsaliensis: ungl. Vetenskapssamhällets i Uppsala årsbok.Vol 37, 2007-2008 (pp. 111-115). Stockholm: Kungl. Vetenskapssamhället i Uppsala
Open this publication in new window or tab >>Kvantkemi: kemi utan provrör
2009 (Swedish)In: Annales Academiae regiae scientiarum Upsaliensis: ungl. Vetenskapssamhällets i Uppsala årsbok.Vol 37, 2007-2008, Stockholm: Kungl. Vetenskapssamhället i Uppsala , 2009, p. 111-115Chapter in book (Other academic)
Place, publisher, year, edition, pages
Stockholm: Kungl. Vetenskapssamhället i Uppsala, 2009
Series
Annales Academiae regiae scientiarum Upsaliensis, Kungl. Vetenskapssamhället i Uppsala, ISSN 0504-0736 ; 37
National Category
Theoretical Chemistry
Research subject
Chemistry with specialization in Quantum Chemistry
Identifiers
urn:nbn:se:uu:diva-122759 (URN)978-91-85832-18-7 (ISBN)
Available from: 2010-04-19 Created: 2010-04-19 Last updated: 2011-03-22Bibliographically approved
Borg, O. A., Karlsson, D., Isomäki-Krondahl, M., Davidsson, J. & Lunell, S. (2008). Predissociation of Chlorobenzene, beyond the pseudo-diatomic model. Chemical Physics Letters, 456(4-6), 123-126
Open this publication in new window or tab >>Predissociation of Chlorobenzene, beyond the pseudo-diatomic model
Show others...
2008 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 456, no 4-6, p. 123-126Article in journal (Refereed) Published
Abstract [en]

Dissociation of chlorobenzene via the lowest singlet excited state has been investigated by means of pump-probe femtosecond spectroscopy and spin-orbit corrected ab initio quantum chemistry. We have found that the so far accepted model with a (1)pi pi* -> (3)pi/n sigma* reaction mechanism has to be amended. We suggest that the mechanism goes via a transition from (1)pi pi* to a pi sigma* state that is to 90% a singlet. Further, three nuclear degrees of freedom required to describe the dissociation have been defined.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-96972 (URN)10.1016/j.cplett.2008.03.030 (DOI)000255555400001 ()
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2017-12-14Bibliographically approved
Norberg, D., Shiotani, M. & Lunell, S. (2008). SH2 reaction vs. hydrogen abstraction/expulsion in methyl radical-methylsilane reactions: Effects of prereactive complex formation. Journal of Physical Chemistry A, 112(6), 1330-1338
Open this publication in new window or tab >>SH2 reaction vs. hydrogen abstraction/expulsion in methyl radical-methylsilane reactions: Effects of prereactive complex formation
2008 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 112, no 6, p. 1330-1338Article in journal (Refereed) Published
Abstract [en]

A quantum chemical study has been undertaken to elucidate the cause of the recently observed S(H)2 reaction between the deuterated methyl radical ((CD3)-C-center dot) and methylsilane (SiD3CH3) following the photolysis of CD3I. [Komaguchi, K.; Norberg, D.; Nakazawa, N.; Shiotani, M.; Persson, P.; Lunell, S. Chem. Phys. Lett. 2005, 410, 1-5.] It is found that the backside SH2 mechanism may proceed favorably for C-Si-C angles deviating with up to 40 degrees from linearity. The competitive hydrogen abstraction reaction is predicted to be active in the range of 90 degrees <= C-Si-C <= 135 degrees. For steeper attack angles, the frontside S(H)2 mechanism is activated. However, high barriers along the corresponding reaction paths probably make the frontside mechanism less important for the present S(H)2 reaction. A number of bound SiH3CH3/CH3I complexes have been located with the MP2 method. At the CCSD(T) level, a complex corresponding to the collinear arrangement where the methyl moiety of methyl iodide points toward the silicon, which is the most favorable conformation for the subsequent S(H)2 reaction with the backside mechanism, is found to be the most stable linear conformer. A complex with similar energy is found where the methyl moiety of methyl iodide points approximately toward an Si-H bond. However, because C-Si-C = 69.4 degrees in this complex, subsequent photolysis of methyl iodide would probably not lead to hydrogen abstraction with full efficiency. These findings could provide an explanation for the observed S(H)2 reaction.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-96121 (URN)10.1021/jp076591y (DOI)000252967900031 ()
Available from: 2007-09-04 Created: 2007-09-04 Last updated: 2017-12-14Bibliographically approved
Shiotani, M., Lund, A., Lunell, S. & Williams, F. (2007). Structures of the hexafluorocyclopropane, octafluorocyclobutane, and decafluorocyclopentane radical anions probed by experimental and computational studies of anisotropic electron spin resonance (ESR) spectra. Journal of Physical Chemistry A, 111(2), 321-338
Open this publication in new window or tab >>Structures of the hexafluorocyclopropane, octafluorocyclobutane, and decafluorocyclopentane radical anions probed by experimental and computational studies of anisotropic electron spin resonance (ESR) spectra
2007 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, no 2, p. 321-338Article in journal (Refereed) Published
Abstract [en]

Anisotropic electron spin resonance (ESR) spectra are reported for the radical anions of hexafluorocyclopropane (c-C3F6-), octafluorocyclobutane (c-C4F8-), and decafluorocyclopentane (c-C5F10-) generated via gamma-irradiation in plastically crystalline tetramethylsilane (TMS) and rigid 2-methyltetrahydrofuran (MTHF) matrices. By combining the analysis of these experimental ESR spectra involving anisotropic hyperfine (hf) couplings with a series of quantum chemical computations, the geometrical and electronic structure of these unusual perfluorocycloalkane radical anions have been characterized more fully than in previous studies that considered only the isotropic couplings. Unrestricted Hartree-Fock (UHF) computations with the 6-311+G(d,p) basis set predict planar ring structures for all three radical anions, the ground electronic states being (2)A(2)" for c-C3F6- (D-3h symmetry), (2)A(2u) for c-C4F8- (D-4h), and (2)A(2)" for c-C5F10- (D-5h), in which the respective six, eight, and ten F-19-atoms are equivalent by symmetry. A successful test of the theoretical computation is indicated by the fact that the isotropic F-19 hf couplings computed by the B3LYP method with the 6-311+G(2df,p) basis set for the optimized geometries are in almost perfect agreement with the experimental values: viz., 19.8 mT (exp) vs 19.78 mT (calc) for c-C3F6-; 14.85 mT (exp) vs 14.84 mT (calc) for c-C4F8-; 11.6 mT (exp) vs 11.65 mT (calc) for c-C5F10-. Consequently, the same computation method has been applied to calculate the almost axially symmetric anisotropic F-19 hf couplings for the magnetically equivalent F-19 atoms: (-4.90 mT, -4.84 mT, 9.75 mT) for c-C3F6-, (-3.54 mT, -3.48 mT, 7.02 mT) for c-C4F8-, and (-2.62 mT, -2.56 mT, 5.18 mT) for c-C5F10-. ESR spectral simulations performed using the computed principal values of the hf couplings and the spatial orientations of the F-19 nuclei as input parameters reveal an excellent fit to the experimental anisotropic ESR spectra of c-C3F6-, c-C4F8-, and c-C5F10-, thereby providing a convincing proof of the highly symmetric D-nh structures that are predicted for these negative ions. Furthermore, using the computed F-19 principal values and their orientations, the effective F-19 anisotropic hf couplings along the molecular symmetry axes were evaluated for c-C3F6- and c-C4F8- and successfully correlated with the positions of the characteristic outermost features in both the experimental and calculated anisotropic spectra. In addition, the electronic excitation energies and oscillator strengths for the c-C3F6-, c-C4F8-, and c-C5F10- radical anions were computed for the first time using time-dependent density functional theory (TD-DFT) methods.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-25008 (URN)10.1021/jp064891u (DOI)000243388500018 ()
Available from: 2007-02-08 Created: 2007-02-08 Last updated: 2017-12-07Bibliographically approved
Komaguchi, K., Nomura, K., Shiotani, M., Lund, A., Jansson, M. & Lunell, S. (2006). ESR and theoretical studies of trimer radical cations of coronene. Spectrochimica Acta A, 63, 76
Open this publication in new window or tab >>ESR and theoretical studies of trimer radical cations of coronene
Show others...
2006 (Swedish)In: Spectrochimica Acta A, Vol. 63, p. 76-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-24799 (URN)
Available from: 2007-02-07 Created: 2007-02-07 Last updated: 2011-01-11
Borg, O. A., Liu, Y.-J., Persson, P., Lunell, S., Karlsson, D., Kadi, M. & Davidsson, J. (2006). Photochemistry of bromofluorobenzenes.. J Phys Chem A Mol Spectrosc Kinet Environ Gen Theory, 110(22), 7045-56
Open this publication in new window or tab >>Photochemistry of bromofluorobenzenes.
Show others...
2006 (English)In: J Phys Chem A Mol Spectrosc Kinet Environ Gen Theory, ISSN 1089-5639, Vol. 110, no 22, p. 7045-56Article in journal (Refereed) Published
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-83647 (URN)16737252 (PubMedID)
Note
Addresses: Univ Uppsala, Dept Quantum Chem, Box 518, S-75120 Uppsala, Sweden.Available from: 2007-02-01 Created: 2007-02-01 Last updated: 2011-01-11
Lundqvist, M. J., Nilsing, M., Lunell, S., Åkermark, B. & Persson, P. (2006). Spacer and anchor effects on the electronic coupling in Ruthenium-bis-terpyridine dye-sensitized TiO2 nanocrystals studied by DFT. Journal of Physical Chemistry B, 110(41), 20513-20525
Open this publication in new window or tab >>Spacer and anchor effects on the electronic coupling in Ruthenium-bis-terpyridine dye-sensitized TiO2 nanocrystals studied by DFT
Show others...
2006 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 41, p. 20513-20525Article in journal (Refereed) Published
Abstract [en]

Structural and electronic properties of TiO2 nanoparticles sensitized with a set of Ru(II)(tpy)2 based dyes have been investigated using density functional theory (DFT) calculations combined with time-dependent (TD) DFT calculations. The effects of carboxylic and phosphonic acid anchor groups, as well as a phenylene spacer group, on the optical properties of the dyes and the electronic interactions in the dye-sensitized TiO2 nanoparticles have been investigated. Inclusion of explicit counterions in the modeling shows that the description of the environment is important in order to obtain a realistic interfacial energy level alignment. A comparison of calculated electronic coupling strengths suggests that both the nature of the anchor group and the inclusion of the phenylene spacer group are capable of significantly influencing electron-transfer rates across the dye-metal oxide interface.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-94853 (URN)10.1021/jp064045j (DOI)000241192200066 ()17034238 (PubMedID)
Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2017-12-14Bibliographically approved
Shiotani, M., Persson, P., Lunell, S., Lund, A. & Williams, F. (2006). Structures of Tetrafluorocyclopropene, Hexafluorocyclobutene, Octafluorocyclopentene and Related Perfluoroalkene Radical Anions Revealed by ESR Spectroscopic and Computational Studies. Journal of Physical Chemistry A, 110, 6307
Open this publication in new window or tab >>Structures of Tetrafluorocyclopropene, Hexafluorocyclobutene, Octafluorocyclopentene and Related Perfluoroalkene Radical Anions Revealed by ESR Spectroscopic and Computational Studies
Show others...
2006 (English)In: Journal of Physical Chemistry A, Vol. 110, p. 6307-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-24802 (URN)
Available from: 2007-02-07 Created: 2007-02-07 Last updated: 2011-01-11
Liu, Y.-J., Lund, A., Persson, P. & Lunell, S. (2005). Density functional theory study of NO adsorbed in A-zeolite. Journal of Physical Chemistry B, 109(16), 7948-7951
Open this publication in new window or tab >>Density functional theory study of NO adsorbed in A-zeolite
2005 (English)In: Journal of Physical Chemistry B, Vol. 109, no 16, p. 7948-7951Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-73818 (URN)
Available from: 2007-02-01 Created: 2007-02-01 Last updated: 2011-01-11
Komaguchi, K., Norberg, D., Nakazawa, N., Shiotani, M., Persson, P. & Lunell, S. (2005). Direct ESR evidence for SH2 type reaction of methyl radical with methylsilane and methylgermane in a low temperature solid: A deuterium labeling study. Chemical Physics Letters, 410(1-3), 1-5
Open this publication in new window or tab >>Direct ESR evidence for SH2 type reaction of methyl radical with methylsilane and methylgermane in a low temperature solid: A deuterium labeling study
Show others...
2005 (English)In: Chemical Physics Letters, Vol. 410, no 1-3, p. 1-5Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-73838 (URN)doi:10.1016/j.cplett.2005.04.091 (DOI)
Available from: 2007-08-06 Created: 2007-08-06 Last updated: 2011-01-11
Organisations

Search in DiVA

Show all publications