| 1. |
- Lundqvist, Maria J., et al.
(författare)
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Calculated optoelectronic properties of Ruthenium tris-bipyridine dyes containing oligophenyleneethynylene rigid rod linkers in different chemical environments
- 2007
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:8, s. 1487-1497
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Tidskriftsartikel (refereegranskat)abstract
- Ruthenium tris-bipyridine dyes containing oligophenyleneethynylene (OPE) rigid rod linker groups ([Ru(bpy)3]2+, [Ru(bpy)2bpy-E-Ipa]2+, [Ru(bpy)2bpy-E-Ph-E-Ipa]2+, and [Ru(bpy)2bpy-E-Bco-E-Ipa]2+, where bpy = 2,2'-bipyridine, E = ethynylene, Ph = p-phenylene, Bco = bicyclo[2.2.2]octylene, and Ipa = isophthalic acid) have been investigated using DFT and TD-DFT calculations to elucidate the influence of the rigid rod on their optoelectronic properties. Experimentally observed differences in the optical absorption for the different complexes are discussed on the basis of TD-DFT simulated absorption spectra. A comparison of the calculated optoelectronic properties of [Ru(bpy)2bpy-E-Ph-E-Ipa]2+ in different chemical environments, that is, in different solvents and with or without counter ions, suggests that both the absorption spectra and the redox properties of the dyes with OPE rods are sensitive to the environment. The calculations show that spurious low-energy charge-transfer excitations present in the TD-DFT calculations of the extended systems in vacuum are removed when the environment is included in the calculations.
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| 2. |
- Persson, Petter, et al.
(författare)
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N1s x-ray Absorption Study of the Bonding Interaction of Bi-Isonicotinic Acid on Rutile TiO2 (110)
- 2000
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 112:9, s. 3945-3948
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Tidskriftsartikel (refereegranskat)abstract
- N1s x-ray absorption spectra of bi-isonicotinic acid (2,28-bipyridine–4,48-dicarboxylic acid! on rutile TiO2(110) have been studied experimentally and quantum chemically. Differences between multilayer and monolayer spectra are explained by the adsorbate bonding to the substrate. A connection to the electronic coupling in dye-sensitized electrochemical devices is made.
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| 3. |
- Thyagarajan, S., et al.
(författare)
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Large Footprint Pyrene Chromophores Anchored to Planar and Colloidal Metal Oxide Thin Films
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:16, s. 9219-9226
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Tidskriftsartikel (refereegranskat)abstract
- Sensitization and binding of a large footprint pyrene chromophore to planar (sapphire) and colloidal metal oxide films (TiO2 and ZrO2) is investigated. The model compound combines a 1-pyrenyl-ethynylenephenylene unit with a new adamantane-tripodal linker that binds to the surface. The linker design, combining a large footprint (2 nm2) of the tripodal linker with the meta position of the COOH anchoring groups, was suggested from atomistic models, and it aims to provide improved spacing control. The pyrene chromophore unit provides a probe of sensitizer−sensitizer interactions through its propensity to form excimers, unless neighboring pyrene units are sufficiently spaced (≥3.5 Å). Absorption and fluorescence studies, and a comparison with a pyrene−rigid rod model compound, suggest that the new tripodal anchor group allows spacing control on planar surfaces. On colloidal films, the linker provides spacing control at low surface coverage but sensitizer−sensitizer interactions are still observed on colloidal films at high surface coverage. Implications for the functionalization of metal oxide films in hybrid molecule−metal oxide semiconductor material systems are discussed.
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| 4. |
- Abrahamsson, Maria, et al.
(författare)
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Bistridentate Ruthenium(II)polypyridyl-Type Complexes with Microsecond 3MLCT State Lifetimes : Sensitizers for Rod-Like Molecular Arrays
- 2008
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Ingår i: Journal of the American Chemical Society. - : ACS. - 0002-7863 .- 1520-5126. ; 130:46, s. 15533-15542
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Tidskriftsartikel (refereegranskat)abstract
- A series of bistridentate ruthenium(II) polypyridyl-type complexes based on the novel 2,6-di(quinolin-8-yl)pyridine (dqp) ligand have been synthesized and their photophysical properties have been studied. The complexes are amenable to substitution in the 4-position of the central pyridine with conserved quasi-C2v symmetry, which allows for extension to isomer-free, rod-like molecular arrays for vectorial control of electron and energy transfer. DFT calculations performed on the parent [Ru(dqp) 2](2+) complex (1) predicted a more octahedral structure than in the typical bistridentate complex [Ru(tpy)2](2+) (tpy is 2,2':6',2"-terpyridine) thanks to the larger ligand bite angle, which was confirmed by X-ray crystallography. A strong visible absorption band, with a maximum at 491 nm was assigned to a metal-to-ligand charge transfer (MLCT) transition, based on time-dependent DFT calculations. 1 shows room temperature emission (Phi = 0.02) from its lowest excited ((3)MLCT) state that has a very long lifetime (tau = 3 micros). The long lifetime is due to a stronger ligand field, because of the more octahedral structure, which makes the often dominant activated decay via short-lived metal-centered states insignificant also at elevated temperatures. A series of complexes based on dqp with electron donating and/or accepting substituents in the 4-position of the pyridine was prepared and the properties were compared to those of 1. An unprecedented (3)MLCT state lifetime of 5.5 micros was demonstrated for the homoleptic complex based on dqpCO2Et. The favorable photosensitizer properties of 1, such as a high extinction coefficient, high excited-state energy and long lifetime, and tunable redox potentials, are maintained upon substitution. In addition, the parent complex 1 is shown to be remarkably photostable and displays a high reactivity in light-induced electron and energy transfer reactions with typical energy and electron acceptors and donors: methylviologen, tetrathiofulvalene, and 9,10-diphenylanthracene. This new class of complexes constitutes a promising starting point for the construction of linear, rod-like molecular arrays for photosensitized reactions and applications in artificial photosynthesis and molecular electronics.
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| 5. |
- Abrahamsson, Maria, et al.
(författare)
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Bistridentate Ruthenium(II)polypyridyl-Type Complexes with Microsecond (MLCT)-M-3 State Lifetimes: Sensitizers for Rod-Like Molecular Arrays
- 2008
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 130:46, s. 15533-15542
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Tidskriftsartikel (refereegranskat)abstract
- A series of bistridentate ruthenium(II) polypyridyl-type complexes based on the novel 2,6-di(quinolin-8-yl)pyridine (dqp) ligand have been synthesized and their photophysical properties have been studied. The complexes are amenable to substitution in the 4-position of the central pyridine with conserved quasi-C-2v symmetry, which allows for extension to isomer-free, rod-like molecular arrays for vectorial control of electron and energy transfer. DIFT calculations performed on the parent [Ru(dqp)(2)](2+) complex (1) predicted a more octahedral structure than in the typical bistridentate complex [Ru(tpy)(2)](2+) (tpy is 2,2':6',2 ''-terpyridine) thanks to the larger ligand bite angle, which was confirmed by X-ray crystallography. A strong visible absorption band, with a maximum at 491 nm was assigned to a metal-to-ligand charge transfer (MLCT) transition, based on time-dependent DIFT calculations. 1 shows room temperature emission (Phi = 0.02) from its lowest excited ((MLCT)-M-3) state that has a very long lifetime (tau = 3 mu s). The long lifetime is due to a stronger ligand field, because of the more octahedral structure, which makes the often dominant activated decay via short-lived metal-centered states insignificant also at elevated temperatures. A series of complexes based on dqp with electron donating and/or accepting substituents in the 4-position of the pyridine was prepared and the properties were compared to those of 1. An unprecedented (MLCT)-M-3 state lifetime of 5.5 mu s was demonstrated for the homoleptic complex based on dqpCO(2)Et. The favorable photosensitizer properties of 1, such as a high extinction coefficient, high excited-state energy and long lifetime, and tunable redox potentials, are maintained upon substitution. In addition, the parent complex 1 is shown to be remarkably photostable and displays a high reactivity in light-induced electron and energy transfer reactions with typical energy and electron acceptors and donors: methylviologen, tetrathiofulvalene, and 9,10-diphenylanthracene. This new class of complexes constitutes a promising starting point for the construction of linear, rod-like molecular arrays for photosensitized reactions and applications in artificial photosynthesis and molecular electronics.
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| 6. |
- Abrahamsson, Maria, et al.
(författare)
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Meta-substituted Ru(II) rigid rods for sensitization of TiO(2)
- 2009
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Ingår i: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 206:2-3, s. 155-163
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in Undetermined Ruthenium polypyridyl rigid-rod compounds with phenylene-ethynelene (OPE) spacers and an isophthalic acid (Ipa) binding group were synthesized and characterized for sensitization of nanocrystalline TiO(2) (anatase) thin films. Density functional theory predicted that the most stable structure oriented the isophthalic group about 45 degrees from normal to the TiO(2) surface. Comparative experimental studies of meta- and para-isomers revealed small changes in the ground state absorption spectra and very similar excited state and redox properties. The excited state injection yields (inj = 0.15 +/- 0.03)into nanocrystalline TiO(2) and the subsequent charge recombination rates were found to be insensitive to the isomer utilized. Meta-substitution enabled the synthesis of sensitizers with two Ru(II) sensitizers that displayed enhanced sunlight absorption relative to the monomeric compound.
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| 7. |
- Borg, OA, et al.
(författare)
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Photochemistry of bromofluorobenzenes
- 2006
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 110:22, s. 7045-7056
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Tidskriftsartikel (refereegranskat)abstract
- The photochemistry of low lying excited states of six different fluorinated bromobenzenes has been investigated by means of femtosecond laser spectroscopy and high level ab initio CASSCF/CASPT2 quantum chemical calculations. The objective of the work was to investigate how and to what extent light substituents, position on the benzene ring and number, would influence the dissociation mechanism of bromobenzene. In general, the actual position of a fluorine atom affects the dissociation rate to a less extent than the number of fluorine atoms. A clear connection between a lowering of a repulsive pi sigma* relative to a bound pi pi* state and the number of fluorine substituents exists, and the previously suggested model of coupling between dissociation rate and relative location of bound and repulsive state still holds for these molecules. A more elaborate examination of the electronic structure of the excited states in bromobenzenes than previously reported is presented.
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| 8. |
- Höst, Gunnar E., 1976-, et al.
(författare)
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Methods for investigating students’ learning and interaction with a haptic virtual biomolecular model
- 2010
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Ingår i: Contemporary Science Education Research: International Perspectives. - Ankara : Pegem Akademi. - 9786053640318 ; , s. 115-121
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Konferensbidrag (refereegranskat)abstract
- Although immersive haptic virtual technologies are emerging rapidly in modern education, few methods exist for delivering data on the pedagogical merits of such models in the molecular life sciences. This paper reports on a selection of methods that we have used to obtain and analyse data on students’ learning and interaction with a haptic virtual model of protein-ligand docking, previously designed by author PBP. The methods have been developed and employed during four consecutive years in which the model has been part of an advanced biomolecular interactions course. In this regard, we present data-collection methods that include written items, interviews, think-aloud tasks and automated time-stamped logs and, corresponding quantitative and qualitative analytical procedures such as pre/posttest statistical comparisons, word usage analysis and, visualised profiling of students’ interaction with the model. Our results suggest that these methods are useful for generating valuable information on students’ learning gain, changes in conceptual understanding, reasoning processes and patterns of interactivity with the model. Dissemination of such methods could provide an empirical contribution to the dearth of research instruments in this domain. Future research will develop these methodologies to explore the relationship between using the model and students’ conceptual and embodied learning.
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| 9. |
- Jones, Robert W., et al.
(författare)
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Direct Determination of the Rate of Intersystem Crossing in a Near-IR Luminescent Cr(III) Triazolyl Complex
- 2023
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Ingår i: Journal of the American Chemical Society. - 0002-7863. ; 145:22, s. 12081-12092
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Tidskriftsartikel (refereegranskat)abstract
- A detailed understanding of the dynamics of photoinduced processes occurring in the electronic excited state is essential in informing the rational design of photoactive transition-metal complexes. Here, the rate of intersystem crossing in a Cr(III)-centered spin-flip emitter is directly determined through the use of ultrafast broadband fluorescence upconversion spectroscopy (FLUPS). In this contribution, we combine 1,2,3-triazole-based ligands with a Cr(III) center and report the solution-stable complex [Cr(btmp)2]3+(btmp = 2,6-bis(4-phenyl-1,2,3-triazol-1-yl-methyl)pyridine) (13+), which displays near-infrared (NIR) luminescence at 760 nm (τ = 13.7 μs, φ = 0.1%) in fluid solution. The excited-state properties of 13+are probed in detail through a combination of ultrafast transient absorption (TA) and femtosecond-to-picosecond FLUPS. Although TA spectroscopy allows us to observe the evolution of phosphorescent excited states within the doublet manifold, more significantly and for the first time for a complex of Cr(III), we utilize FLUPS to capture the short-lived fluorescence from initially populated quartet excited states immediately prior to the intersystem crossing process. The decay of fluorescence from the low-lying 4MC state therefore allows us to assign a value of (823 fs)-1to the rate of intersystem crossing. Importantly, the sensitivity of FLUPS to only luminescent states allows us to disentangle the rate of intersystem crossing from other closely associated excited-state events, something which has not been possible in the spectroscopic studies previously reported for luminescent Cr(III) systems.
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| 10. |
- Kjær, Kasper S., et al.
(författare)
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Finding intersections between electronic excited state potential energy surfaces with simultaneous ultrafast X-ray scattering and spectroscopy
- 2019
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 10:22, s. 5749-5760
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Tidskriftsartikel (refereegranskat)abstract
- Light-driven molecular reactions are dictated by the excited state potential energy landscape, depending critically on the location of conical intersections and intersystem crossing points between potential surfaces where non-adiabatic effects govern transition probabilities between distinct electronic states. While ultrafast studies have provided significant insight into electronic excited state reaction dynamics, experimental approaches for identifying and characterizing intersections and seams between electronic states remain highly system dependent. Here we show that for 3d transition metal systems simultaneously recorded X-ray diffuse scattering and X-ray emission spectroscopy at sub-70 femtosecond time-resolution provide a solid experimental foundation for determining the mechanistic details of excited state reactions. In modeling the mechanistic information retrieved from such experiments, it becomes possible to identify the dominant trajectory followed during the excited state cascade and to determine the relevant loci of intersections between states. We illustrate our approach by explicitly mapping parts of the potential energy landscape dictating the light driven low-to-high spin-state transition (spin crossover) of [Fe(2,2′-bipyridine)3]2+, where the strongly coupled nuclear and electronic dynamics have been a source of interest and controversy. We anticipate that simultaneous X-ray diffuse scattering and X-ray emission spectroscopy will provide a valuable approach for mapping the reactive trajectories of light-triggered molecular systems involving 3d transition metals.
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