Interaction of divalent metal ions with uracil III. Complexes of MnII,FeII, CoII,NiII and CuII with uracil acting as bidentate ligand

Summary Some novel nonelectrolytic complexes of uracil in its anionic form with divalent metal ions were synthesised by heating to reflux a methanolic solution of uracil and a metal salt at pHca. 7.5. The isolated complexes are formulated as [ML₂(H₂O)₂] where M = Mn, Fe, Co, Ni, or Cu; L = C₄H₃N₂O₂ Electronic spectra indicate the hexacoordination of the metal ion in all the complexes and also the presence of a weak metal-oxygen interaction. The disappearance of the (NH) band and also the appreciable change both in intensity and position the characteristic bands of the 2-keto group of the uracil in the infrared spectra of all the complexes indicate the chelation of the uracil through C(2)=O and N(3).     

Kinetics and mechanism of the interaction of thioglycolic acid with [(H2O)(tap)2RuORu(tap)2(H2O)]2+ ion at physiological pH

The interaction of thioglycolic acid (tgaH₂) with the title complex has been studied spectrophotometrically in aqueous medium as a function of [substrate complex], [ligand], pH and temperature at constant ionic strength. The reactivity of different donor centers [e.g., (N), (N,O) and (O,O) are compared]. In the studied pH range the reaction is a two-step ligand dependent process. The thermodynamic and activation parameters are reported and compared with other systems studied earlier. As no study on this system is available in the literature, it is not possible to compare with reports from other groups.     

Mixed-ligand complexes of osmium(III/II)8-quinolinolates with one diimine/azoimine ligand

Summary Paramagnetic [Os^IIIDQ₂]⁺ and diamagnetic [Os^IIAQ₂] (Q = deprotonated 8-quinolinols, D = diimines and A = azoimines) complexes were prepared and characterised by physicochemical, magnetic and spectroscopic methods. The complexes exhibit several spin-allowed and spinforbidden charge-transfer transitions in the visible region. In MeCN solution the OsN₄O₂ unit displays nearly reversible Os^IV-Os^III and Os^III-Os^II couples in the ca. -0.4 to +1.1 V range versus SCE. An anodic shift of these responses is seen in going from diimines to azoimines. The stability of metal oxidation levels is correlated on the basis of -acceptor properties of these ligands.     

Rational Design for Complementary Donor–Acceptor Recognition Pairs Using Self‐Complementary Hydrogen Bonds

An adaptable and efficient molecular recognition pair has been established by taking advantage of the complementary nature of donor–acceptor interactions together with the strength of hydrogen bonds. Such distinct molecular recognition propagates in orthogonal directions to effect extended alternating co‐assembly of two different appended molecular entities. The dimensions of the assembled structures can be tuned by stoichiometric imbalance between the donor and acceptor building blocks. The morphology of the self‐assembled material can be correlated with the ratio of the two building blocks.     

Efficient White‐Light Generation from Ionically Self‐Assembled Triply‐Fluorescent Organic Nanoparticles

Low cost, simple, and environmentally friendly strategies for white‐light generation which do not require rare‐earth phosphors or other toxic or elementally scare species remain an essentially unmet challenge. Progress in the area of all‐organic approaches is highly sought, single molecular systems remaining a particular challenge. Taking inspiration from the designer nature of ionic‐liquid chemistry, we now introduce a new strategy toward white‐light emission based on the facile generation of nanoparticles comprising three different fluorophores assembled in a well‐defined stoichiometry purely through electrostatic interactions. The building blocks consist of the fluorophores aminopyrene, fluorescein, and rhodamine 6G which represent blue, green, and red‐emitting species, respectively. Spherical nanoparticles 16(±5) nm in size were prepared which display bright white‐light emission with high fluorescence quantum efficiency (26 %) and color coordinate at (0.29, 0.38) which lie in close proximity to pure white light (0.33, 0.33). It is noteworthy that this same fluorophore mixture in free solution yields only blue emission. Density functional theory calculations reveal H‐bond and ground‐state proton transfer mediated absolute non‐parallel orientation of the constituent units which result in frustrated energy transfer, giving rise to emission from the individual centers and concomitant white‐light emission.