Self-assembly of oligothiophene chromophores by m -calix[3]amide scaffold

摘要

m-Calix[3]amides carrying the bithiophene chromophore (BTC3A) and terthiophene chromophore (TTC3A) were synthesized by the cyclic trimerization of m-aminobenzoic acid esters for the purpose of the control and understanding of the self-assembly of oligothiophene chromophores. Polymers and model compounds were also prepared for comparison. From the 1H NMR experiments, cyclic trimer BTC3A showed the syn/anti equilibrium in solution, and the syn/anti conformer ratio (76/24 in CDCl_3) was influenced by the solvent character. Namely, the population of the syn conformer was lowest (70%) in THF-d8 and was highest (86%) in CDCl_3/CD_3OD (1/1 in volume). On the other hand, the population of the syn conformer of cyclic trimer TTC3A was high (84%) even in CDCl_3. In a CHCl _3 solution of cyclic trimer BTC3A, the absorption maximum (342 nm) blue-shifted and the emission maximum (448 nm) red-shifted compared with those of polymer BTPA and model compound BTM. The solvent character also had an impact on the optical properties of cyclic trimer BTC3A. The red-shifted emission maximum (481 nm) of cyclic trimer BTC3A in CH_3OH indicated the interaction between three bithiophene chromophores. The emission maxima of cyclic trimer TTC3A (486 nm) demonstrated a small red-shift from model compound TTM (477 nm), and no solvent dependency was observed, unlike cyclic trimer BTC3A.