Casper Larissa A, Deuter Katharina L, Rehse Anja, Winter Rainer F
Department of Chemistry, Universität Konstanz, Konstanz 78457, Germany.
ACS Org Inorg Au. 2024 Apr 19;4(4):395-409. doi: 10.1021/acsorginorgau.3c00070. eCollection 2024 Aug 7.
We report on three new 9-phenyl-substituted ferroceno[2,3]indenylmethylium dyes - with electron-donating (OMe, Me) or electron-withdrawing (CF) substituents. Complexes - exist as racemic mixtures of and enantiomers. Pyramidalization at the methyl C atom in the precursor carbinol species - or the corresponding one-electron reduced radicals induces a second stereocenter, as the 9-phenyl substituent may reside in an or an position. Indeed, alcohol crystallizes as a racemate of , and , isomers. Cationic complexes - are of deep green color and show intense electronic absorption in the visible. The oxidation and reduction processes are thoroughly investigated by means of cyclic voltammetry and UV/vis/NIR spectroelectrochemistry, the latter showing their electrochromic behavior. -dependent EPR spectroscopy, EPR spin counting at 20 °C, as well as the UV/vis/NIR spectra of the reduced samples suggest that the one-electron reduced, neutral radicals dimerize nearly quantitatively (≥99.98%). Chemical reduction of furnished an isomeric mixture of dimeric -. As was shown by cyclic voltammetry and UV/vis/NIR spectroelectrochemistry, the latter dimer redissociates to monomers upon oxidation, thereby closing a reversible cycle of redox-induced C-C bond making and breaking.
我们报道了三种新的9-苯基取代的二茂铁并[2,3]茚基甲基染料，带有供电子（OMe、Me）或吸电子（CF）取代基。配合物以对映体的外消旋混合物形式存在。前体甲醇物种或相应的单电子还原自由基中甲基C原子处的锥形化诱导了第二个立体中心，因为9-苯基取代基可能位于或位置。实际上，醇以、异构体的外消旋体形式结晶。阳离子配合物呈深绿色，在可见光区有强烈的电子吸收。通过循环伏安法和紫外/可见/近红外光谱电化学对氧化和还原过程进行了深入研究，后者显示了它们的电致变色行为。依赖于的电子顺磁共振光谱、20℃下的电子顺磁共振自旋计数以及还原样品的紫外/可见/近红外光谱表明，单电子还原的中性自由基几乎定量地二聚（≥99.98%）。的化学还原得到了二聚体的异构体混合物。如循环伏安法和紫外/可见/近红外光谱电化学所示，后者的二聚体在氧化时重新解离为单体，从而形成了一个由氧化还原诱导的C-C键形成和断裂的可逆循环。
