Spectral properties of bichromophoric pyrene derivatives: Monomer vs. excimer fluorescence

Spectral properties of bichromophoric pyrene probes with different linkage between pyrene units were compared in chloroform, cyclohexane and methanol, as well as in the polymer matrices polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(vinyl chloride) (PVC). The derivatives under study were pyrene, di(1-pyrenylmethyl) ether (DiPyM), 4-(1-pyrenemethoxymethyl) phenylethene (PyS) and 2,3-di(4-(1-pyrenemethoxymethyl)phenyl)butane (DiPyS).The absorption spectra of the probes exhibited well-resolved bands that were only slightly influenced by substitution and medium. Parent pyrene and PyS, exhibited well-resolved monomer fluorescence in all media, which indicated a weak solvent effect. DiPyM and DiPyS exhibited strong excimer fluorescence in solutions of low viscosity. The influence of the viscosity on the ratio of excimer and monomer emission Φexc/Φem of DiPyS and DiPyM in diethylene glycol was also studied. In polymer matrices, only monomer emission of DiPyM and DiPyS was observed. However, the lifetime of monomer emission was influenced by the medium.