duction indicating destruction of the indacene structure. At an even higher negative potential reversible reduction of the phenylanthracene substructure can be observed. Apparently the substructures are electrochemically independent, too.Cyclic voltammetry of 4 a indicated that the oxidation of the dimethylamino group appears between the oxidation and the reduction of the indacene framework. This suggests that the lone electron pair at the amino group is energetically located between the HOMO and the LUMO of the indacene chromophore. The oxidation potential of the protonated dimethylamino group is considerably higher than that of the free base and beyond the accessible potentials in acetonitrile, which is reflected in the CV upon protonation by the disappearance of this peak. This increase of the oxidation potential makes a nonradiative deactivation process like the one described above impossible. The oxidation of the indacene chromophore in the protonated form occurs at the same potential as in the neutral form, where it appears as the second oxidation step. Apparently the indacene chromophore is influenced inductively by a positive charge on the dimethylamino group in the same way no matter how the charge is created, by protonation or oxidation.We have showed that by specific functionalization the electron donor and acceptor properties of the difluoroboradiaza-sindacene chromophore can be directed in a way that leads to electrogenerated luminescence or proton-dependent fluorescence. Presently we aim to incorporate the described dye compounds as active components in OLEDs and to test analytical applications in sensor chemistry.
Experimental SectionCyclic voltammetry: Solvent acetonitrile: potentials reported [mV] vs ferrocene (FOC) as internal standard. Experimental conditions: reversible half-wave potentials El,,, room temperature, scan rate 250 mVs-', platinum disc working electrode. Ag, AgCl pseudo-reference electrode, platinum counterelectrode, supporting electrolyte 0 1 M tetrabutylammonium hexafluorophosphate. Spectroelectrochemistry : Solvent acetonitrile, transmission cell with a gold minigrid working electrode or reflection cell with a platinum disc working electrode. Optlcdl spectra: Concentrations IO-'M to 1 0 -6~ in chloroform filtered over basic alumina before use Emission spectra are corrected. ECL-measurements: The ECL spectrum was recorded by applying an alternating square wave with redox potentials determined by cyclic voltammetry (switching time 20 ms. solvent dichloromethane). Concentration: IO-'M, supporting electrolyte' 0.1 M tetrabutykammoniurn hexafluorophosphate. The emission is red-shifted because of reabsorption in more highly concentrated solutions.
Ohne signifikante Strukturänderung kann die lineare Fe‐O‐Fe‐Einheit in einem μ‐Oxotetraphenylphorphyrin‐Eisen(III)‐Dimer am Sauerstoffatom protoniert werden (Strukturbild des μ‐OH‐verbrückten Komplexes rechts). Die antiferromagnetische Kopplung zwischen den Eisenzentren wird dabei deutlich geschwächt. Der Selbstaustausch der Protonen ist langsam.
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