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Electronic states and phosphorescence of dendron functionalized platinum(II) acetylides
Department of Physics, Norwegian University of Science and Technology.
Department of Physics, Norwegian University of Science and Technology.
Department of Physics, Norwegian University of Science and Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
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2007 (English)In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 124, no 2, 302-310 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2007. Vol. 124, no 2, 302-310 p.
Keyword [en]
optical power limiting, platinum(II)-complexes, triplet state, phosphorescence, electronic structure, inter-system crossing, 2, 2-bis(methylol)propionic acid dendrimers, nonlinear-optical properties, pt-ethynyl compound, site-isolation, dendritic encapsulation, core, absorption, porphyrin, molecules, metalloporphyrins
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-16335DOI: 10.1016/j.jlumin.2006.03.019ISI: 000243674400021Scopus ID: 2-s2.0-33751425887OAI: oai:DiVA.org:kth-16335DiVA: diva2:334377
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Nonlinear Absorbing platinum(II) Acetylides for Optical Power Limiting Applications
Open this publication in new window or tab >>Nonlinear Absorbing platinum(II) Acetylides for Optical Power Limiting Applications
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

During the past few decades, laser technology has had a strong impact on our society, providing important contributions to materials processing, data storage, communications, medicine, and defense applications. However, the progress in laser technology has also brought about the development of harmful portable high‐power lasers and tactical laser weapons. As a result, the hazard of being blinded by lasers (accidentally or from hostile use) has increased significantly. Hence, the need for protection against lasers has emerged. In order to protect optical sensors against harmful laser radiation, materials that absorb high intensity light, such as nonlinear absorbing chromophores, are employed. The concept of controlling the intensity of an optical light beam is usually referred to as optical power limiting and can be used efficiently in sensor protection devices.In this thesis, various nonlinear absorbing platinum(II) acetylides have been synthesized and characterized regarding their photophysical and optical limiting properties. Dendronized platinum(II) acetylides were prepared in order to evaluate the site isolation effect offered by the dendritic surrounding. The photophysical measurements reveal that the dendritic encapsulation enhances the phosphorescence, increases the luminescence lifetimes, and improves the optical limiting performance due to reduced quenching of the excited states.Triazole‐containing chromophores were synthesized using click chemistry to achieve functionalized platinum(II) acetylides. It was found that the position of the triazole unit affects the photophysical properties of these chromophores. The most promising results were obtained for the chromophore with the triazole located at the end of the conjugation where it may act as an electron donor, thus contributing to improved two‐photon absorption.A branched platinum(II) acetylide was also prepared in order to investigate the effect of multiple conjugated arms as well as multiple heavy atoms within the same molecule on the optical limiting performance. The star shaped chromophore reached the lowest clamping level of all compounds included in this thesis and constitutes a highly suitable chromophore for optical power limiting applications.The nonlinear absorbing chromophores were also incorporated into novel solid state materials based on PMMA. The actual device fabrication of doped organic glasses as optical limiters for sensor protection is presented, and their optical limiting performance is reported. The obtained organic glasses can reduce the transmission of high intensity light by 97 %.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 73 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:59
Keyword
optical power limiting
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-9169 (URN)978-91-7415-102-2 (ISBN)
Public defence
2008-10-03, F3, Lindstedtsvägen 26, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20100920Available from: 2008-09-30 Created: 2008-09-29 Last updated: 2010-09-20Bibliographically approved

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