Blue-emitting copolymers of isoquinoline and fluorene

5,8-Linked copolymers of isoquinoline with fluorene were synthesized by Pd(0)-catalyzed Suzuki polycondensation reaction. The polymers showed good solubility in common organic solvents and the number average molecular weights determined from GPC analysis fall in the range of 7.03-8.08 × 103 g/mol. The photoluminescence spectra of these neutral materials in solution exhibit emission maxima in the range 408-426 nm. An X-ray diffraction study on a single crystal of a 5,8-di(9,9-dimethylfluoren-2-yl) isoquinoline model compound shows it to have a non-planar conformation and sheds light on the factors that drive the solid-state packing. The alkylation of the imine nitrogen was achieved by treatment with methyl iodide and the alkylated products were characterized by 1H NMR, 13C NMR and UV-vis spectroscopy. The absorption maxima of model compounds and polymers were red shifted by 46-70 nm upon N-alkylation.