Photochemical aspects in anthracene-containing cationic polyurethanes

The synthesis, characterization and photochemical properties of a new polyurethane cationomer (PUC-AN) with anthracene chromophore groups attached on the quaternary ammonium units is reported and compared to those of a model compound (AN) carrying the same moiety. PUC-AN synthesis implied the quaternization reaction with 9-chloromethylanthracene of the tertiary amine of one precursor polymer based on poly(tetramethylene oxide) diol of 2000 average molecular weight, tolylene-2,4-diisocyanate (as 2,4- and 2,6-TDI, 80:20 v/v isomers mixture), N-methyldiethanol amine and terephthalaldehyd-bis(3-hydroxymethylphenylimine) in a molar ratio of 1:3:1:1. The fluorescence spectra of the anthracene structure indicates that the synthesized compounds present different shifts in solution and in the solid state, their photochemical behavior being influenced by monomer and excimer emission. The photophysical investigations revealed that such structures can function as fluorescent chemosensors for transitional metals, showing a fluorescence quenching in the presence of different metal ions (, Fe³⁺, Cu²⁺). The quenching mechanisms for PUC-AN and the corresponding model compound (AN) are assigned to electron transfer and/or energy transfer processes of Dexter type.