Weak forces at work in dye-loaded zeolite materials: spectroscopic investigation on cation-sulfur interactions.

The interaction between sulfur-containing chromophores and cationic species (K(+)) has been investigated in dye-loaded zeolite materials by means of photoluminescence spectroscopy. A red-shift in the emission spectra of the host-guest compounds (HGCs) has been detected and unambiguously connected to the close proximity between a conjugated moiety and nearby free charges, suggesting a specific role played by sulfur lone pair electrons. Quantum-chemical calculations on model compounds have been performed to support this hypothesis.