Continuous Symmetry Breaking Induced by Ion Pairing Effect in Heptamethine Cyanine Dyes: Beyond the Cyanine Limit

Pierre-Antoine Bouit (1) , Christophe Aronica (1, 2) , Loic Toupet (3) , Boris Le Guennic (1) , Chantal Andraud (1) , Olivier Maury (1)

1 LC - Laboratoire de Chimie - UMR5182
2 LMI - Laboratoire des Multimatériaux et Interfaces
3 IPR - Institut de Physique de Rennes

The association of heptamethine cyanine cation 1(+) with various counterions A (A = Br(-), I(-), PF(6)(-), SbF(6)(-), B(C(6)F(5))(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(C(6)F(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.

Domaines: Physique Générale [physics.gen-ph]

Pierre-Antoine Bouit, Christophe Aronica, Loic Toupet, Boris Le Guennic, Chantal Andraud, et al.. Continuous Symmetry Breaking Induced by Ion Pairing Effect in Heptamethine Cyanine Dyes: Beyond the Cyanine Limit. Journal of the American Chemical Society, 2010, 132 (12), pp.4328--4335. ⟨10.1021/ja9100886⟩. ⟨hal-01073293⟩