| 1. |
- Lindgren, Mikael, et al.
(författare)
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Electronic states and phosphorescence of dendron functionalized platinum(II) acetylides
- 2007
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313 .- 1872-7883. ; 124:2, s. 302-310
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Tidskriftsartikel (refereegranskat)abstract
- The photophysical properties of bis((4-(phenylethynyl)phenyl)ethynyl)bis(tributylphosphine) platinum(II) with 2,2-bis(methylo])propionic acid (bis-MPA) dendritic substituents were studied. The fluorescence emission decay upon excitation in the UV (typically 350-380 nm) was rapid, in the order of I ns or shorter. In oxygen-saturated tetrahydrofuran solvent, the phosphorescence decay time was in the order of 200 ns. Bright phosphorescence at 530 nm was found for dendrimers under certain conditions. The associated phosphorescence decay time considerably increased to above 100-200 mu s at higher concentrations (30-100 mu M), and in oxygen-evacuated samples. Thus, it was clarified that the strongest triplet quenching was caused by oxygen dissolved in the sample, since it was possible to reversibly go between the bright and quenched phosphorescent state by freeze-thaw pumping cycles. The bright phosphorescence formed spontaneously for the cases with the larger dendritic substituents is implying a chromophore protecting effect. From time-dependent density functional calculations, the electronic structure of a few low-lying singlet and triplet states are discussed. A new mechanism for efficient triplet state formation and phosphorescence of Pt-ethynyls is proposed. Here, a fast relaxation via internal conversion takes the excited population of the dominant pi -> pi*, excitation into a lower singlet state of ligand-to-metal charge transfer character of pi sigma* type. This allows an efficient inter system crossing to the triplet state manifold.
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| 2. |
- Vestberg, Robert, et al.
(författare)
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Dendron Decorated Platinum(II) Acetylides for Optical Power Limiting
- 2006
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 39:6, s. 2238-2246
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Tidskriftsartikel (refereegranskat)abstract
- The effect of dendritic substituents on a nonlinear optical chromophore for optical power limiting (OPL) has been investigated. Synthesis and characterization of bis((4-(phenylethynyl)phenyl)ethynyl)bis-(tributylphosphine) platinum(II) with dendritic end groups are described. Polyester dendrimers up to the fourth generation were grown divergently using the anhydride of 2,2-bis(methylol)propionic acid (bis-MPA). The introduction of the dendritic moieties onto the NLO chromophore enables further processing of the materials using polymeric and related techniques. OPL measurements performed at 532, 580, and 630 nm show that the OPL properties improve with increasing size of the dendritic substituent. It is also shown that the addition of the dendrons increase the OPL as compared to the nondecorated bis((4-(phenylethynyl)phenyl) ethynyl)bis-(tributylphosphine)platinum(II). By use of femtosecond z-scan measurements carried out at different pulse-repetition frequencies, it is shown that the two-photon absorption cross section is ∼10 GM. Using pulse repetition frequencies (100 kHz-4.75 MHz) so that the time between the pulses is comparable with the triplet excited lifetime, the z-scans become dominated by excited-state absorption of excited triplet states.
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| 3. |
- Westlund, Robert, et al.
(författare)
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Click Chemistry for Photonic Applications : Triazole-Functionalized Platinum(II) Acetylides for Optical Power Limiting
- 2008
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 18:2, s. 166-175
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Tidskriftsartikel (refereegranskat)abstract
- Three different triazole-containing platinum(ii) acetylide compounds were synthesized by click chemistry and evaluated for their use in optical power limiting (OPL) applications. The triazole unit was incorporated at three different positions within, or at the end of, the conjugation path of the chromophore. The aim is to explore the possibilities of using click chemistry to prepare dendronized chromophores, and to evaluate how the triazole structure affects the photophysical properties and the optical power limiting abilities of these acetylide compounds. It is shown that the concept of click chemistry can be used to attach branched monomer units to ethynyl-phenyl arms by Huisgen 1,3-dipolar cycloaddition, forming triazole units within the chromophore. Photophysical characterization of these triazole-containing materials shows an absorption maximum within the UV-A region and emission through both fluorescence and phosphorescence. Bright phosphorescence was emitted from argon purged samples, and decay measurements thereof showed triplet lifetimes of up to 100 μs. The results from the photophysical characterization suggest that the triazole does break the conjugation path, and in order to gain maximum optical limiting the triazole needs to be placed at the end of the conjugation. All three investigated triazole-containing platinum(ii) acetylides show good optical power limiting at 532 nm (10 ns pulse, f/5 set-up, 2 mm cells). The most efficient compound, with the triazole positioned at the end of the conjugation, reaches a defined clamping level of 2.5 μJ for a sample with a concentration of 50 mM in THF and a linear transmission above 80% at 532 nm. These data can be compared to the OPL properties of Zn-based porphyrins or derivatized thiophenes, reaching clamping levels of 6-15 μJ.
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| 4. |
- Westlund, Robert, et al.
(författare)
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Multi-functionalized platinum(II) acetylides for optical power limiting
- 2006
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Ingår i: Optical Materials in Defence Systems Technology III. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9780819464996 ; , s. U87-U94
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Konferensbidrag (refereegranskat)abstract
- Preliminary results on the optical power limiting properties of platinum(II) acetylides containing triazole units are presented. It is shown that the triazole units give a positive contribution to the limiting abilities of the platinum(H) acetylide and that this modified chromophore could have potential use in sensor protection devices. Moreover, this paper discusses how the versatile building block 2,2-bis(methylol)propionic acid (bis-MPA) can be used advantageously to functionalize nonlinear optical (NLO) platinum(H) acetylides. The bis-MPA units can be used to prepare dendritic substituents offering site isolation to the chromophore leading to improved clamping. The bis-MPA functionalization also improves the solubility of the platinum(H) acetylides in many organic solvents. The preparation of solid-state optical power limiters, where the NLO chromophore is inserted in an optically transparent matrix, is addressed. Again, the bis-MPA unit can be employed to increase the number of accessible end-groups to which matrix-compatible species can be attached. It is concluded that the hydroxy-functional platinum(II) acetylides can be modified to fit almost any matrix, organic or inorganic. Finally, depending on functionalization, it is possible to prepare doped glasses where the chromophore is either embedded in the matrix, or covalently bonded to the matrix.
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| 5. |
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| 6. |
- Carlmark, Anna E, et al.
(författare)
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Atom transfer radical polymerization of methyl acrylate from a multifunctional initiator at ambient temperature
- 2002
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Ingår i: Polymer. - OXFORD, ENGLAND : ELSEVIER SCI LTD. - 0032-3861 .- 1873-2291. ; 43:15, s. 4237-4242
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Tidskriftsartikel (refereegranskat)abstract
- A multifunctional initiator for ATRP has been synthesized by reacting a hyperbranched polyether, based on 3-ethyl-3-(hydroxymethyl)oxetane, with 2-bromo-isobutyrylbromide. The macroinitiator contained approximately 25 initiating sites per molecule. It was used for the atom transfer radical polymerization of methyl acrylate mediated by Cu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me-6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. The large number of growing chains from each macromolecule increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems and prevent them from forming a gel, the concentration of propagating radicals must be kept low. The polymerizations under these conditions were well controlled. When a ratio of initiating sites-to-catalyst of 1:0.05 was used, the polymers from all of the reactions had a low polydispersity, ranging from 1.1 to 1.4. None of the polymerizations under these conditions gave gelation. Monomer conversions as high as 65% were reached while maintaining control over the polymerization. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 7. |
- Ekeblad, Annika, et al.
(författare)
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Randomized Trial of Interpersonal Psychotherapy and Cognitive Behavioral Therapy for Major Depressive Disorder in a Community-Based Psychiatric Outpatient Clinic
- 2016
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Ingår i: Depression and anxiety (Print). - : WILEY-BLACKWELL. - 1091-4269 .- 1520-6394. ; 33:12, s. 1090-1098
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundInterpersonal psychotherapy (IPT) and cognitive behavioral therapy (CBT) are both evidence-based treatments for major depressive disorder (MDD). Several head-to-head comparisons have been made, mostly in the United States. In this trial, we compared the two treatments in a small-town outpatient psychiatric clinic in Sweden. The patients had failed previous primary care treatment and had extensive Axis-II comorbidity. Outcome measures were reduction of depressive symptoms and attrition rate. MethodsNinety-six psychiatric patients with MDD (DSM-IV) were randomized to 14 sessions of CBT (n = 48) or IPT (n = 48). A noninferiority design was used with the hypothesis that IPT would be noninferior to CBT. A three-point difference on the Beck Depression Inventory-II (BDI-II) was used as noninferiority margin. ResultsIPT passed the noninferiority test. In the ITT group, 53.5% (23/43) of the IPT patients and 51.0% (24/47) of the CBT patients were reliably improved, and 20.9% (9/43) and 19.1% (9/47), respectively, were recovered (last BDI score amp;lt;10). The dropout rate was significantly higher in CBT (40%; 19/47) compared to IPT (19%; 8/43). Statistically controlling for antidepressant medication use did not change the results. ConclusionsIPT was noninferior to CBT in a sample of depressed psychiatric patients in a community-based outpatient clinic. CBT had significantly more dropouts than IPT, indicating that CBT may be experienced as too demanding. Since about half the patients did not recover, there is a need for further treatment development for these patients. The study should be considered an effectiveness trial, with strong external validity but some limitations in internal validity.
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| 8. |
- Glimsdal, E., et al.
(författare)
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Two-photon absorption cross-section and triplet states of dendritic Pt-acetylides for OPL applications
- 2005
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - The International Society for Optical Engineering.
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Konferensbidrag (refereegranskat)abstract
- The photo-physical properties of bis((4-(phenylethynyl)phenyl)ethynyl) bis(tributylphosphine) platinum(II) with 2,2-bis(methylol)propionic acid (bis-MPA) dendritic substituents were studied. The introduction of dendrimer capping was found to give rise to protection from oxygen quenching of phosphorescent states with a considerably longer decay time of the phosphorescence (0.1 -0.4 ms range) for solvents with oxygen removed or dendrimers of larger size (G2-G4) or higher concentration. Presence of oxygen reduces the phosphorescence decay time to below 1 microsecond. Two-photon induced fluorescence and z-scan of fs pulses at low pulse repetition frequency at approximately 720 nm revealed that the two-photon absorption cross-section is in the order of 0.01 cm/GW, well below the 0.34cm/GW reported by Staromlynska et al [J. Staromlynska, T. McKay and P. Wilson, J. Appl. Phys. 88, 1726 (2000)] and similar for all dendrimer complexes as well as the non-capped Pt-acetylide. Z-scans performed at high pulse repetition frequency gives an apparent two-photon absorption cross-section that is higher due to the population of excited triplet states, and the contribution from incoherent multiphoton absorption involving the triplet states.
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| 9. |
- Malkoch, Michael, et al.
(författare)
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Synthesis of well-defined hydrogel networks using Click chemistry
- 2006
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Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; :26, s. 2774-2776
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Tidskriftsartikel (refereegranskat)abstract
- New PEG-based hydrogel materials have been synthesized by Click chemistry and shown to result in well-defined networks having significantly improved mechanical properties; the selectivity of the azide/ acetylene coupling reaction also allows for the incorporation of various additives and functional groups leading to chemical tailoring of the hydrogels.
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| 10. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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