Fluorescent chemosensory conjugated polymers based on optically active polybinaphthyls and 2,2′-bipyridyl units

Chiral conjugated polymers P-1 and P-2 were synthesized by the polymerization of (S)-6,6'-di(4-methylphenyl)-3,3'-diiodo-2,2'-bisoctoxy-1,1'-binaphthyl (S-M-2) and (S)-6,6'-dibromo-3,3'-di(4-methylphenyl)-2,2'-bisoctoxy-1,1'-binaphthyl (S-M-3) with 5,5'-divinyl-2,2'- bipyridine (M-1) under Heck cross-coupling reaction, respectively. The chiral polymers P-1 and P-2 can show strong blue-green fluorescence. The responsive properties of chiral polymers on transition metal ions and H+ were investigated by fluorescent spectra. Cu2+ and Ni2+ lead to nearly complete fluorescent quenching of two polymers, and Zn2+, Cd2+, and H+ can cause slight fluorescent quenching. Such distinct ion responsive behaviors revealed the obvious difference of coordination abilities of transition metal ions with 2,2'-bipyridyl ligand receptors. The obvious quenching effect of P-1 and P-2 also suggested that the chiral conjugated polymers backbone structure and the efficiencies of energy or electron transfer between backbone and receptor ions in the main chain play important roles in fluorescence quenching. The results show that the chiral conjugated polybinaphthyls incorporating the 2,2'-bipyridyl moiety as the recognition site can act as promising active materials for application as fluorescent chemosensors.