AZACROWN-CH2-BIPYRIDINE RECEPTORS IN SILICA XEROGEL - OPTICAL AND COORDINATION PROPERTIES

Samples of silica xerogel doped with encapsulated series of three rece ptors of the type (aza-3n-crown-n)-CH2-(2,2'-bipyridine), where n = 4, 5 and 6, were prepared by the sol-gel process. Fluorescence excitatio n spectra of the encapsulated receptors differ from the absorption spe ctra. Emission of the samples can be quenched specifically owing to th e coordination reaction with transition metal ions. Emission decays ca n be described by a double exponential, the lifetime values being shor t at room temperature. EPR spectra of Cu-II ions complexed on the surf ace of the receptor doped xerogel have fairly well resolved hyperfine structure and show an elongated rhombic octahedral environment for the receptors with 2,2'-bipyridine groups.