Host-guest interactions including polymer-mediated proton transfer dynamics are investigated for 7-azaindole embedded in poly(2-hydroxyethyl methacrylate) matrix using time-resolved fluorescence and transient absorption spectroscopy. Upon absorption of a photon the dye molecule having cyclic H-bonds with a polymeric group undergoes excited-state double proton transfer in 100 ps to form its tautomer, while the molecule without an H-bond bridge does not experience the proton transfer within the lifetime of 1200 ps. The reverse proton transfer takes place on the time scale of 60 mus in the ground state.