Synthesis, Electronic, and Electro-Optical Properties of Emissive Solvatochromic Phenothiazinyl Merocyanine Dyes

• Published in: Chemistry : a European journal 2011-08, Vol.17 (36), p.9984-9998
• Main Authors: Hauck, Martina, Stolte, Matthias, Schönhaber, Jan, Kuball, Hans-Georg, Müller, Thomas J. J.
• Format: Article
• Language: English
• Subjects: Chemistry; chromophores; cyclic voltammetry; dyes/pigments; electro-optical absorption spectroscopy; fluorescence; heterocycles
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201100592

Phenothiazinyl merocyanine dyes with variable substitution patterns on the peripheral benzene ring were synthesized in good yields by Knoevenagel condensation of the corresponding phenothiazinyl aldehydes and N‐methylrhodanine or indan‐1,3‐dione. The electronic properties were investigated by cyclic voltammetry, absorption, electro‐optical absorption, and emission spectroscopy. All these merocyanines reveal reversible redox behavior that stems from the phenothiazinyl‐centered oxidation to give stable radical cations. The redox potentials strongly correlate with Hammett σp parameters. All merocyanines reveal large Stokes shifts. They also display a pronounced emissive solvatochromism, which is caused by large dipole moment changes upon excitation from the ground to the excited state. These findings are supported by solvatochromism studies and time‐dependent DFT computations. A dye‐ing breed: Phenothiazinyl–merocyanine dyes with variable substitution patterns on the peripheral benzene ring were synthesized in good yields by Knoevenagel condensation of the corresponding phenothiazinyl aldehydes and N‐methylrhodanine or indan‐1,3‐dione. Their electronic properties were investigated by various methods (see figure).