Chasing Self-Assembly of Thioether-Substituted Flavylium Salts in Solution and Bulk State
Résumé
Two series of flavylium triflates carrying alkoxy side chains in the A-ring (benzo unit of chromylium salt) and thioethers in the B-ring (phenyl unit) (On-Fla-Sm) as well as thioethers at both A- and B-ring (Sn-Fla-Sm) were synthesized in order to understand the effect of thioether functionalization on their self-assembly and electronic properties. Concentration-dependent and diffusion ordered (DOSY) NMR experiments of O1-iV-Fla-S3 indicated the formation of columnar H-aggregates in solution with antiparallel intracolumnar stacking of the AC unit (chromylium) of the flavylium triflate, which agreed with the solid state structure of O1-V-Fla-S1 . Thioether substitution on the B-ring changed the linear optical properties in solution, while it has no effect on the A-ring. According to differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction bulk self-assembly of these ionic liquid crystals (ILCs) depends on the total number of side chains, yielding SmA and LamCol phases for ILCs with 2 - 3 chains and Colro, Colh phases for ILCs with 3 - 6 chains. Thus, we demonstrated that thioethers are a useful design tool for ILCs with tailored properties.