Long-wavelength-absorbing and -emitting carbostyrils with high fluorescence quantum yields

Synthesis, absorption and fluorescence spectra, as well as quantum yields o f a series of donor-acceptor-substituted carbostyrils (= quinolin-2(1H)-one s), are reported. Unprecedented strong absorption maxima (epsilon = 10000-2 0000) close to the visible spectrum, large Stokes shifts up to 130 nm, and quantum yields up to 0.7 are obtained with derivatives containing donor sub stituents at C(6) and C(7), and either one Ph substituent at C(3) or one CF 3 residue at C(4). For analytical applications in biochemistry and medicine , N(1)-functionalization, or amidoacylation at C(3) in the case of the CF3 derivatives, is possible without a concomitant hypsochromic shift of their absorption and emission maxima. Semiempirical molecular-orbital calculation s (AM1 for structures, ZINDO for electronic transition energies) prove to b it a suitable tool for the prediction of absorption properties of these com pounds. The crystal-structure analysis of 6,7-dimethoxy-1-methyl-3-nitro-4- (trifluoromethyl)quinolin-2-(1H)-one (7) (C13H11F3N2O5, monoclinic, P2(1)/c , a = 12.372(2), b = 12.154(2), c = 10.119(2)Angstrom, beta = 112.95(2)degr ees) shows that the NO2 group, squeezed between the CF3 and the C=O group, is oriented almost perpendicularly (87.8(4)degrees) to the ring plane. The intramolecular F ... N distance between the CF3 and the NO2 group is only 2 .513(4)Angstrom.