The synthesis of 2-bromo[6]helicene was revised and improved up to 51% yield. Its reactivity was thoroughly investigated, and a library of 17 different carbon, boron, nitrogen, phosphorus, oxygen and sulfur substituted derivatives was prepared. The racemization barrier for 2-bromo[6]helicene was determined, and the usage of enantiomers in the synthesis of optically pure helicenes was rationalized. The three most energy-demanding reactions using enantiomerically pure 2-bromo[6]helicene were tested in order to confirm the predicted enantiomeric excess.

The first racemization-stable helicene derivatives fluorinated at terminal rings, 1,2,3,4-tetrafluoro[6]­helicene (6) and 1,2,3,4,13,14,15,16-octafluoro[6]­helicene (15), were synthesized via the Wittig reaction followed by oxidative photocyclization in an overall yield of 41% of 6 and 76% of 15. The changed electronic structure in fluorinated helicenes was reflected in a slight shift of UV–vis absorption, fluorescence excitation, and emission spectra maxima when compared to unsubstituted [6]­helicene. Cyclic voltammetry revealed a moderate decrease in the HOMO–LUMO gap with increasing fluorination. The specific rotation of tetrafluoro[6]­helicene 6 enantiomers was found to be approximately 25% lower than that of unsubstituted [6]­helicene. The theoretical study of the racemization barrier suggested a reasonable shift toward higher energy with increasing fluorination. The increasing fluorination also significantly affected the intermolecular interactions in the crystal lattice. The observed CH···F interactions led to the formation of 1D-molecular chains in the crystal structures of both fluorinated helicenes.

We report on the preparation of a hybrid system consisting of exfoliated graphene and N,N′-didodecyl 3,10-diazapicenium salts by solution based methods. The obtained hybrids were characterized by steady state and time-resolved spectroscopic as well as microscopic techniques to corroborate the p-doped character.