(Spectro)electrochemical Properties of Anthracene Containing Triarylamine Platinum(II) Acetylides

Abstract

The synthesis of [Pt{2} 2 (PPh 3 ) 2 ] (5) (10-ethinyl-9-di(p-anisyl) aminoanthracene = alkyne 2H) in a cis and trans configuration was achieved. Adsorption of cis-5 on AlOx as well as electrochemical oxidation led to a reductive elimination of 10,10'-(buta-1,3-diyne-1,4-diyl)bis(9-di(p-anisyl)amino-anthracene) (6). The molecular structures of the alkyne intermediate 2H, [Pt{2} Cl(PPh 3 ) 2 ] (4) and butadiyne 6 have been determined by single crystal X-ray diffraction. Cyclic voltammetry measurements of the platinum-acetylides trans-4, and cis-and trans-5 demonstrated, that the back donation from platinum towards the π-system results in a shift of the triarylamine and anthracene related redox processes towards lower E°' values, when compared to the SiMe 3 -protected alkyne of 2 (= 2SiMe 3 ). Both platinum complex trans-5 and butadiyne 6 demonstrated that the individual arylamine and the respective anthracenyl buildings blocks can be oxidized in four one electron processes. Spectroelectrochemical studies revealed several intense intraligand absorptions in the NIR, demonstrating a high degree of delocalization in the ligand. However, a direct IVCT through the platinum was not observed.