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Charge Transfer Through Cross-π-conjugated and Cross-hyperconjugated Bridges: An Intervalence Charge Transfer Study
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. (Leif Hammarström)
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi. (H. Ottosson)
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
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(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Nyckelord [en]
Intervalence charge transfer, Cross-conjugation, Cross-hyperconjugation
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-180437OAI: oai:DiVA.org:uu-180437DiVA, id: diva2:550376
Tillgänglig från: 2012-09-07 Skapad: 2012-09-06 Senast uppdaterad: 2012-10-01Bibliografiskt granskad
Ingår i avhandling
1. Bridge Mediated Electron Transfer in Conjugated and Cross-Conjugated Donor-Acceptor Compounds
Öppna denna publikation i ny flik eller fönster >>Bridge Mediated Electron Transfer in Conjugated and Cross-Conjugated Donor-Acceptor Compounds
2012 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Detailed understanding of electron transfer reactions is important in many aspects of chemistry, biology and solar energy conversion.

The main aim of this thesis is to provide further insight into electron transfer through highly conjugated bridge structures. Towards this end, three series of donor-acceptor dyads have been studied, all using an oligo(1,4-phenylene-ethynylene) moiety as the bridge. A common theme in these series is that they explore the effects of having either an ethynylene or phenylene as the attachment group between the bridge and the donor or acceptor. Photophysical characterization of these dyads was carried out by means of time resolved laser spectroscopy. The results show that having an ethynylene as attachment group results in higher rates for bridge mediated electron and energy transfer compared to similar systems, where a phenylene was used.

It was also found that most of the investigated systems show a fast back electron transfer. A notable exception is a zinc(II) phthalocyanine- gold(III) porphyrin dyad, where very fast photoinduced electron transfer (kPET = 1.0×1012 s-1) was followed by relatively slow back electron transfer (kBET = 1.0×109 s-1). A complementary DFT investigation indicated that the charge shifted state involves a reduction of the gold ion, rather than the porphyrin ring. This results in lower electronic coupling between the reduced gold porphyrin and the bridge and thus slower back electron transfer.

A series of zinc porphyrin platinum acetylide dyads was used to explore the effects on electronic coupling of different attachments points on the porphyrin ring. For the investigated system it was found that linking at the meso-position results in an eight-fold increase in electron transfer rate compared to the β-position.

In addition, a series of mixed valence compounds was used to investigate electronic coupling mediated by cross-hyperconjugated or cross-π-conjugated bridges. The results indicate coupling elements of 100-400 cm-1, with the cross-π-conjugated bridge having the largest coupling. A complementary TD-DFT study indicates that both through bond and through space coupling can be active in these systems. The relative contribution of these two mechanisms to the electronic coupling is highly conformer dependent.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2012. s. 71
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 974
Nyckelord
Electron transfer, Ultrafast, Long-range, Intervalence charge transfer, cross conjugation, hyperconjugation
Nationell ämneskategori
Fysikalisk kemi
Forskningsämne
Fysikalisk kemi
Identifikatorer
urn:nbn:se:uu:diva-180442 (URN)978-91-554-8474-3 (ISBN)
Disputation
2012-10-19, Polhemssalen, Ångström lab, Lägerhyddsvägen 1, Uppsala, 13:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2012-10-01 Skapad: 2012-09-07 Senast uppdaterad: 2013-01-23Bibliografiskt granskad

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