Oxidation of Isodiphenylfluorindine: Routes to 13-Oxoisodiphenylfluorindinium Perchlorate and Fluorindine Cruciform Dimers

Isodiphenylfluorindine (5) reacts with K2Cr2O7/H+ to give 13-oxoisodiphenylfluorindinium perchlorate (7) (75%), but with phenyliodine bis(trifluoroacetate) (PIFA) or MnO2 it gives the zwitterionic and quinoidal cruciform 13,13′-dimers 11 (85%) and 12 (89%), respectively. The zwitterionic 13,13′-dimer 11 can be rapidly converted with MnO2 into the quinoidal 13,13′-dimer 12 (100%). UV–vis, NMR, single-crystal X-ray diffraction, and density functional theory studies support the structural assignments of all products. The electrochemical behavior of the compounds is also presented.