Platinum(II) Schiff Base Complexes as Photocatalysts for Visible-Light-Induced Cross-Dehydrogenative Coupling Reactions.

Four phosphorescent platinum(II) Schiff base complexes are screened for application in visible-light-induced cross-dehydrogenative coupling (CDC) reactions. Preliminary studies show that, among the four platinum(II) complexes, Pt3 is an efficient catalyst for CDC reactions with oxygen as an oxidant. Light irradiation (λ>420 nm) on a mixture of the PtII complex, tertiary amine, and a variety of nucleophiles (nitroalkanes, ketones, or indoles) under aerobic conditions gives α-functionalized tertiary amines in good to excellent yields. The photoluminescence quenching experiment reveals that the CDC reaction is initiated by photoinduced electron transfer from N-phenyltetrahydroisoquinoline to the PtII complex. Further, electron spin resonance (ESR) measurements clearly indicate the formation of superoxide radical anions (O2 .- ) rather than singlet oxygen (1 O2 ) during the photocatalytic reaction.

Long-lived excited states of zwitterionic copper(I) complexes for photoinduced cross-dehydrogenative coupling reactions.

Four heteroleptic copper(I) complexes containing phenanthroline and monoanionic nido-carborane-diphosphine ligands have been prepared and structurally characterized by various spectroscopic techniques and X-ray diffraction. These complexes exhibit intense absorptions in the visible range and excited-state lifetimes on the microsecond scale. Their application in visible-light-induced cross-dehydrogenative coupling reactions was investigated. Preliminary studies showed that one of the four copper(I) complexes is an efficient catalyst for photoinduced oxidative C-H functionalization using oxygen as oxidant. Furthermore, α-functionalized tertiary amines were obtained in good-to-excellent yields by light irradiation (λ>420 nm) of a mixture of our Cu(I) complex, tertiary amines, and a variety of nucleophiles (nitroalkane, acetone, or indoles) under aerobic conditions. Electron paramagnetic resonance measurements provided evidence for the formation of superoxide radical anions (O2(-⋅)) rather than singlet oxygen ((1)O2) during these photocatalytic reactions.

A fluorescence and fluorescence probe study of benzonaphthyridines.

A series of benzo[b][1,8]naphthyridines has been synthesized by Friedländer condensation of 2-aminoquinoline-3-carbaldehyde 1 (o-aminoaldehyde) with alicyclic ketones in basic medium. Benzonaphthyridines branched with various side-chains and substituents are prepared with the aim of being investigated as a good fluorescent material. Electronic absorption and fluorescence properties of some representative benzonaphthyridines in organic solvents, water-dioxane, and SDS, CTAB and Triton-X-100 micelles have been examined. The linear correlation between solvent polarity and fluorescence properties is observed. This study may provide new directions for the development of fluorescence probes as reporters of microenvironments of organized assemblies.