Molecular dynamics of coil–rod–coil molecules depending on their concentrations in polar or non-polar solvent: intra- and intermolecular interactions and charge transfer emissions

Concentration-dependent molecular dynamics of long coil–rod–coil molecules at the concentrations of 1×10−6 M ∼1×10−4 M in polar or non-polar solvent were investigated by steady-state excitation, fluorescence, and picosecond time-resolved fluorescence spectroscopies. The fluorescence spectra of the molecules reveal both characteristics of local excited-state emission and strong intramolecular charge-transfer (ICT) emission. The steady-state excitation spectra and the picosecond time-resolved fluorescence decay profiles in the concentrations of 5×10−5 M and 1×10−4 M ascertain hydrophobic rod-to-rod interaction (J-aggregation) in methanol solution. The hydrophilic intermolecular interactions (amorphous aggregation) in n-hexane are also discussed.