Long-Wavelength-Absorbing and -Emitting Carbostyrils with High Fluorescence Quantum Yields

Synthesis, absorption and fluorescence spectra, as well as quantum yields of a series of donor-acceptor-substituted carbostyrils (=quinolin-2(1H)-ones), are reported. Unprecedented strong absorption maxima (ε=10000 – 20000) 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 substituents at C(6) and C(7), and either one Ph substituent at C(3) or one CF₃ 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 calculations (AM1 for structures, ZINDO for electronic transition energies) prove to be a suitable tool for the prediction of absorption properties of these compounds. The crystal-structure analysis of 6,7-dimethoxy-1-methyl-3-nitro-4-(trifluoromethyl)quinolin-2-(1H)-one ( 7 ) (C₁₃H₁₁F₃N₂O₅, monoclinic, P2₁/c, a=12.372(2), b=12.154(2), c=10.119(2)Å, β=112.95(2)°) shows that the NO₂ group, squeezed between the CF₃ and the C=O group, is oriented almost perpendicularly (87.8(4)°) to the ring plane. The intramolecular F⋅⋅⋅N distance between the CF₃ and the NO₂ group is only 2.513(4)Å.     

The Crystal Structures of a Lower Order and a “Higher Order” Cyanocuprate: [tBuCu(CN)Li(OEt2)2]∞ and [tBuCutBu{Li(thf)(pmdeta)}2CN]

Different types of bonding are present in cyanocuprates 1 and 2 , whose crystal structures could be determined (the drawings below show the important structural characteristics). Accordingly, 1 is a lower order cyanocuprate of the type RCu(CN)Li, whereas 2 , which is of the type R₂Cu(CN)Li₂, does not exist as a “higher order” cyanocuprate with Cu–CN bonds, but rather as a cyano-Gilman cuprate.     

Burning Graphite Faster than Carbon Black: A Case of Diffusion Control

External diffusion may be exploited as a tool to purify materials in a way thought to be inaccessible from a chemical reactivity point of view. A mixture of two carbonaceous materials, graphite and carbon black, are thermally oxidized in either i) outside total diffusion-limited regime or ii) total diffusion-limited regime. Depending on the treatment applied it is possible to purify either graphite, a trivial task, or carbon black, a task thought impossible. Introducing geometrical selectivity, controlled total diffusion-limited chemistry exceeds by far the field of carbon materials and can be used as an engineering tool for many materials purification, original synthesis, or to introduce asymmetry in a system. Several examples for direct applications of the findings are mentioned.