Direct probing of ion pair formation using a symmetric triangulenium dye
Artikel i vetenskaplig tidskrift, 2011

The 2,6,10-tris(dialkylamino)trioxatriangulenium dyes (ATOTA+) are highly stabilised cationic chromophores with D3h symmetry. The symmetry gives rise to a degeneracy of the main electronic transition. In low polarity solvents significant splitting of this degenerate transition is observed and assigned to ion pair formation. Ion pairing of the 2,6,10-tris(dioctylamino)trioxatriangulenium ion with Cl-, BF4-, PF6- and TRISPHAT anions was studied using absorption spectroscopy. A clear correlation is found between the size of the anion and the splitting of the ATOTA+ transitions. In benzene the Cl- salt displays a splitting of 1955 cm-1, while the salt of the much larger TRISPHAT ion has a splitting of 1543 cm-1. TD-DFT calculations confirm the splitting of the states and provide a detailed insight into the electronic structure of the ion pairs. The different degree of splitting in different ion pairs is found to correlate with the magnitude of the electric field generated in each ion pair, thus leading to the conclusion that the effect seen is an internal Stark effect. By insertion of an amphiphilic derivative of the ATOTA+ chromophore in an oriented lamellar liquid crystal, it was possible to resolve the two bands of the double peak spectrum and show their perpendicular orientation in the molecular framework, as predicted by the calculations.

Författare

Fredrik Westerlund

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Jonas Elm

Kobenhavns Universitet

Jacob Lykkebo

Kobenhavns Universitet

Nils Carlsson

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Erling Thyrhaug

Kobenhavns Universitet

Björn Åkerman

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

T. J. Sorensen

Kobenhavns Universitet

Kurt V. Mikkelsen

Kobenhavns Universitet

Bo W. Laursen

Kobenhavns Universitet

Photochemical and Photobiological Sciences

1474-905X (ISSN) 1474-9092 (eISSN)

Vol. 10 1963-1973

Styrkeområden

Nanovetenskap och nanoteknik

Ämneskategorier

Fysikalisk kemi

Fundament

Grundläggande vetenskaper

DOI

10.1039/c1pp05253e