Synthesis, spectroelectrochemistry and electronic structure calculations of 4-(2-ferrocenylvinyl)-[2.2]-paracyclophane and 4,12-di-(2-ferrocenylvinyl)-[2.2]-paracyclophane

4,12-di-(2-ferrocenylvinyl)-[2.2]-paracyclophane 2 has been prepared and investigated with respect to its electrochemical and UV/Vis/NIR spectroelectrochemical properties. Cyclic and square wave voltammetric measurements show two consecutive one-electron oxidations with a moderate redox splitting of 112(±3) mV for the individual Fc/Fc+ couples. In spite of this redox splitting, radical cation 2
• + is a class I mixed-valent system with no detectable electronic coupling between the individual redox sites as is shown by the comparison of the Vis/NIR spectra of 2
• +, 22+ and the radical cation of 4-(2-ferrocenylvinyl)-[2.2]-paracyclophane, 4
• +. The NIR bands observed for the oxidized forms have been assigned as ferrocene-based d-d transitions by quantum chemical calculations.

The 4,12-di-(2-ferrocenylvinyl)-[2.2]-paracyclophane radical cation features two mutually insulated ferrocenyl subunits despite a sizable redox splitting of 112 mV for their consecutive oxidation.Figure optionsDownload as PowerPoint slideHighlights
► 4,12-di-(2-ferrocenylvinyl)-[2.2]-paracyclophane has been synthesized via Heck reaction.
► Electrochemistry shows a splitting of redox waves for 4,12-di-(2-ferrocenylvinyl)-[2.2]-paracyclophane, 2.
► Spectroelectrochemical measurements reveal the absence of electronic coupling in 2+.
► DFT calculations reveal that the NIR absorption of 2+ is due to Fe (d-d) transitions.