Continuous symmetry breaking induced by ion pairing effect in heptamethine cyanine dyes: Beyond the cyanine limit

Article abstract of DOI:10.1021/ja9100886

The association of heptamethine cyanine cation 1⁺ with various counterions A (A = Br^-, I^-, PF₆^-, SbF₆^-, B(C₆F₅)₄ ^-, TRISPHAT) was realized. The six different Ion pairs have been characterized by X-ray diffraction, and their absorption properties were studied In polar (DCM) and apolar (toluene) solvents. A small, hard anion (Br ^-) Is able to strongly polarize the polymethine chain, resulting In the stabilization of an asymmetric dipolar-like structure In the crystal and In nondissociating solvents. On the contrary, In more polar solvents or when it is associated with a bulky soft anion (TRISPHAT or B(C₆F ₅)₄^-), the same cyanine dye adopts preferentially the ideal polymethine state. The solid-state and solution absorption properties of heptamethine dyes are therefore strongly correlated to the nature of the counterion.

Full text of DOI:10.1021/ja9100886

Supporting information for
Continuous Symmetry Breaking Induced by Ion Pairing Effect in
Heptamethine Cyanine Dyes: Beyond the Cyanine Limit.
Pierre-Antoine Bouit, Christophe Aronica, Loïc Toupet, Boris Le Guennic, Chantal Andraud*
and Olivier Maury*.
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