A Self-Assembled Unit Comprising 12 Squaraine Dyes Built Up from Two Star-Shaped Hexasquarainyl-Benzene Molecules |
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| Authors: | Maximilian H Schreck Dr Merle I S Röhr Prof Timothy Clark Dr Vladimir Stepanenko Prof Frank Würthner Prof Christoph Lambert |
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| Institution: | 1. Institut für Organische Chemie & Center for Nanosystems Chemistry, Julius-Maximilians-Universität Würzburg, 97074 Würzburg, Germany;2. Computer Chemistry Center, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91052 Erlangen, Germany |
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| Abstract: | We describe the aggregate formation and optical properties of a star-shaped hexaarylbenzene with six squaraine chromophores (=hexasquarainyl benzene). Comprehensive concentration-dependence studies in acetone/CHCl3 mixtures reveal a strong propensity to form discrete dimeric aggregates with a high binding constant in excess of 106 m −1. In this context, a large hypsochromic shift of almost 2700 cm−1 was found in the absorption spectrum, indicating H-type exciton coupling. The aggregate band is characterised by a very small band width of only 560 cm−1, probably caused by exchange narrowing. Both experimental and computational methods were used to elucidate the supramolecular aggregate structure, which is assumed to consist of two stacked hexasquarainyl benzene monomers. |
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| Keywords: | dyes/pigments exchange narrowing exciton coupling noncovalent interactions self-assembly |
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