Solvent assisted fluorescence modulation of a C3-symmetric organogelator

Abstract

The synthesis and self-assembling properties of C₃ symmetric donor–acceptor molecules containing 1,3,4-oxadiazole and bisthiophene moieties in the core functionalized with octyl (BTOX8) and dodecyl (BTOX12) substituted phenyl acetylene units at the periphery are reported. BTOX8 was found to form gels only in aliphatic solvents, whereas BTOX12 formed gels in both aliphatic and aromatic solvents. Photophysical analysis of BTOX12 solutions showed a striking effect of the solvent on the nature of the self-assembled aggregate formed. Our studies indicate that in aliphatic solvents such as n-decane the solvent molecules interact mainly with the alkyl regions of BTOX12. As a result the π–π interaction between the neighbouring molecules becomes feasible resulting in strong excitonic coupling between the neighbouring molecules leading to excimer type emission. In aromatic solvents the solvent molecules interact mainly with the chromophoric part of BTOX12 resulting in reduced π-stacking between the molecules in the aggregate leading to monomer type emission. Films prepared from aliphatic and aromatic solvents exhibited photophysical properties significantly similar to those observed in the respective solvents. Photophysical studies of the films indicated that the films prepared from n-decane exhibited an H-type molecular arrangement whereas the films prepared from toluene exhibited a slipped stack J-type arrangement.