Studies on a Vinyl Ruthenium-Modified Squaraine Dye : Multiple Visible/Near-Infrared Absorbance Switching through Dye- and Substituent-Based Redox Processes

Chen, Jing; Winter, Rainer F.

Studies on a Vinyl Ruthenium-Modified Squaraine Dye : Multiple Visible/Near-Infrared Absorbance Switching through Dye- and Substituent-Based Redox Processes

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Datum

2012

Publikationstyp

Zeitschriftenartikel

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Erschienen in

Chemistry - A European Journal. 2012, 18(34), pp. 10733-10741. ISSN 0947-6539. eISSN 1521-3765. Available under: doi: 10.1002/chem.201200800

Zusammenfassung

Abstract:The bis(vinyl ruthenium)-modified squaraine dye 1 was synthesized by treatment of [RuHCl(CO)(PiPr3)2] with bis(ethynyl)-substituted squaraine 8. Spectroscopic and electrochemical measurements on 1 and its organic precursors 6–8 were performed to study the effect of the vinyl ruthenium “substituents,” particularly with respect to (poly)electrochromism. Attachment of the vinyl ruthenium moieties endows metal–organic squaraine 1 with two additional oxidation waves and lowers the first two oxidation potentials by approximately 300 mV with respect to its organic precursors. Squaraines 6, 7, 8, and 1 strongly absorb at 648, 663, 656, or 709 nm. Although organic dyes 6, 7, and 8 fluoresce, no room-temperature emission is observed for 1. The radical cations and anions of 6, 7, 8, and 1 as well as the doubly oxidized dications have been studied by IR and UV/Vis/NIR spectroelectrochemistry, and the −/0/+/2+ redox sequences were found to be reversible in each case. Our results indicate that the 12−/−/0/+/2+ redox system constitutes a polyelectrochromic switch in which absorption in the visible or the near-infrared range is reversibly turned off or shifted deep into the NIR. They also show that radical cation 1.+ is an intrinsically delocalized system with only little contribution from the outer vinyl ruthenium tags to the oxidation process. Dication 12+ constitutes a class-II mixed-valent system with two electronically different vinyl ruthenium moieties and has an open-shell singlet electronic ground-state structure. ESR and NMR spectra of chemically prepared 1.+ and 12+ corroborate these results. It has also emerged that reduction involves an orbital that is strongly delocalized across the entire squaraine π system and strongly affects the peripheral vinyl ruthenium sites.

Fachgebiet (DDC)

540 Chemie

Schlagwörter

dyes/pigments, electrochemistry, ruthenium, squaraines, vinyl complexes

Zitieren

ISO 690

CHEN, Jing, Rainer F. WINTER, 2012. Studies on a Vinyl Ruthenium-Modified Squaraine Dye : Multiple Visible/Near-Infrared Absorbance Switching through Dye- and Substituent-Based Redox Processes. In: Chemistry - A European Journal. 2012, 18(34), pp. 10733-10741. ISSN 0947-6539. eISSN 1521-3765. Available under: doi: 10.1002/chem.201200800

BibTex

@article{Chen2012-08-20Studi-20693,
  year={2012},
  doi={10.1002/chem.201200800},
  title={Studies on a Vinyl Ruthenium-Modified Squaraine Dye : Multiple Visible/Near-Infrared Absorbance Switching through Dye- and Substituent-Based Redox Processes},
  number={34},
  volume={18},
  issn={0947-6539},
  journal={Chemistry - A European Journal},
  pages={10733--10741},
  author={Chen, Jing and Winter, Rainer F.}
}

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    <dcterms:abstract xml:lang="deu">Abstract:The bis(vinyl ruthenium)-modified squaraine dye 1 was synthesized by treatment of [RuHCl(CO)(PiPr3)2] with bis(ethynyl)-substituted squaraine 8. Spectroscopic and electrochemical measurements on 1 and its organic precursors 6–8 were performed to study the effect of the vinyl ruthenium “substituents,” particularly with respect to (poly)electrochromism. Attachment of the vinyl ruthenium moieties endows metal–organic squaraine 1 with two additional oxidation waves and lowers the first two oxidation potentials by approximately 300 mV with respect to its organic precursors. Squaraines 6, 7, 8, and 1 strongly absorb at 648, 663, 656, or 709 nm. Although organic dyes 6, 7, and 8 fluoresce, no room-temperature emission is observed for 1. The radical cations and anions of 6, 7, 8, and 1 as well as the doubly oxidized dications have been studied by IR and UV/Vis/NIR spectroelectrochemistry, and the −/0/+/2+ redox sequences were found to be reversible in each case. Our results indicate that the 12−/−/0/+/2+ redox system constitutes a polyelectrochromic switch in which absorption in the visible or the near-infrared range is reversibly turned off or shifted deep into the NIR. They also show that radical cation 1.+ is an intrinsically delocalized system with only little contribution from the outer vinyl ruthenium tags to the oxidation process. Dication 12+ constitutes a class-II mixed-valent system with two electronically different vinyl ruthenium moieties and has an open-shell singlet electronic ground-state structure. ESR and NMR spectra of chemically prepared 1.+ and 12+ corroborate these results. It has also emerged that reduction involves an orbital that is strongly delocalized across the entire squaraine π system and strongly affects the peripheral vinyl ruthenium sites.</dcterms:abstract>
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