Search for new luminophores with predetermined physicochemical and chemical properties. XIV.N-Arylmethylene- and N-hetarylmethylene derivatives of poly (3‒aminopropene)

Abstract

The possibility of creating polymers with fluorescence, derivatives of poly (3-aminopropene) (PAP) by alkylation of amino groups with aromatic or heterocyclic aldehydes by Leykart-Wallach reaction with own fluorescence was investigated. Synthesis of N-alkylated PAP derivatives was performed by sequential conversion: acrylamide → PAA (Mν = 100 kDa) → PAP → alkylated PAP. Due to the impossibility of using LiAlH4 to reduce the amide groups of polyacrylamide to amine due to the low solubility of PAA in the non-aqueous (diethyl ether, tetrahydrofuran, etc.) solvents, the reduction of PAA by other reducing agents was optimized. It was found that the best conditions for the reduction of amide groups of PAA to amine - acetic acid - dioxane as a solvent and NaBH4 (suspended in anhydrous 1,4-dioxane) as a reducing agent. According to IR spectroscopy, the products obtained are copolymers of 3-aminopropene (the main amount of elementary units), acrylamide and acrylic acid. To modify the structure of the obtained polymer, the Leuckart-Wallach reaction was used, where the following aldehydes having luminescence were selected: pyrene-3-aldehyde, 2-hydroxy-1-naphthaldehyde, anthracene-9-carbaldehyde, and 3.5 phenyl-1-(4-formylphenyl)-2-pyrazoline. To obtain N-Ar/Het-methylene derivatives, a mixture of PAP, aldehyde and 98% formic acid was heated under harsh conditions (6 hours, glycerol bath), isolated and purified. The obtained modified samples of polymers are intensely fluorescent both in the solid state and in the form of solutions, which indicates the successful passage of the Leykart-Wallach reaction. Spectral characteristics were obtained for solutions in a mixed solvent – ethyl acetate – formic acid (9 : 1). For both the original aldehydes and the copolymers in the mixed solvent used, the spectral fluorescence curves lose their oscillatory structure, probably due to the specific effect of the mixed solvent on the phosphor molecules (for the original aldehydes) and the side methylamino-N-arylmethylene - […СН2-СН(СН2-NH-CH2-Ar)- …] and methylamino-N-getarylmethylene […-СН2-СН(СН2-NH-CH2-Het)-…] groups both in the ground and in the excited state, and for polymers of inhomogeneity of the medium with local polarity zones.