One-step synthesis of indolizino[3,4,5-ab]isoindoles by manganese(I)-catalyzed C-H activation: structural studies and photophysical properties

Herein, a regioselective synthesis of indolizino[3,4,5-ab]isoindoles, a valuable class of heterocycles with interesting luminescence properties, is described using manganese(I)-catalyzed C-H activation. The reported transformation proceeds in one-step and employs readily available 2-phenylpyridines as starting materials. Furthermore, the obtained single products exhibit blue-greenish fluorescence with high quantum yields.

Synthesis, Study, and Application of Pd(II) Hydrazone Complexes as the Emissive Components of Single-Layer Light-Emitting Electrochemical Cells

For the first time, square planar Pd(II) complexes of hydrazone ligands have been investigated as the emissive components of light-emitting electrochemical cells (LECs). The neutral transition metal complex, [Pd(L¹)₂]·2CH₃OH (1), (HL¹ = (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinhydrazide), was prepared and structurally characterized. Complex 1 displays quasireversible redox properties and is emissive at room temperature in solution with a λ_max of 590 nm. As a result, it was subsequently employed as the emissive material of a single-layer LEC with configuration FTO/1/Ga/In, where studies reveal that it has a yellow color with CIE(x, y) = (0.33, 0.55), a luminance of 134 cd cm^-2, and a turn-on voltage of 3.5 V. Protonation of the pendant pyridine nitrogen atoms of L¹ afforded a second ionic complex [Pd(L¹H)₂](ClO₄)₂ (2) which is also emissive at room temperature with a λ_max of 611 nm, resulting in an orange LEC with CIE(x, y) = (0.43, 0.53). The presence of mobile anions and cations in the second inorganic transition metal complex resulted in more efficient charge injection and transport which significantly improved the luminance and turn-on voltage of the device to 188.6 cd cm^-2 and 3 V, respectively. This study establishes Pd(II) hydrazone complexes as a new class of materials whose emissive properties can be chemically tuned and provides proof-of-concept for their use in LECs, opening up exciting new avenues for potential applications in the field of solid state lighting.

Porphyrinoids with Vinylene Bridges

Porphyrinoids containing vinylene bridges, such as triphyrin(2.1.1), porphycene, porphyrin(2.1.2.1), and hexaphyrin(2.1.2.1.2.1), are a relatively new family of porphyrinoids. Vinylene bridges give porphyrinoids a lower symmetry and a flexibility of the framework and they permit cis/trans-isomerization reactions; these factors confer unique properties to these substances, such as coordination to metal ions and aromaticity switching. In this account, the synthesis, crystal structures, and properties of new porphyrinoids containing vinylene bridges are summarized.

1 Introduction

2 Triphyrin(2.1.1)

3 Porphycene

4 Porphyrin(2.1.2.1)

5 Hexaphyrin(2.1.2.1.2.1)

6 Conclusion

Synthesis of Pyrrolo[2,1,5-cd]indolizine Rings via Visible-Light-Induced Intermolecular [3+2] Cycloaddition of Indolizines and Alkynes

A range of indolizine smoothly underwent visible-light-induced intermolecular [3+2] annulations with internal alkynes to afford pyrrolo[2,1,5-cd]indolizine in good to excellent yields with high regioselectivity. Through this cascade reaction, a series of fluoroactive fused indolizines with a large π-system were conveniently synthesized. The usage of visible light as energy source with air as a stoichiometric oxidant under simple conditions makes this process attractive and practical.

Application of primary halogenated hydrocarbons for the synthesis of 3-aryl and 3-alkyl indolizines

A transition-metal-free synthetic route to 3-aryl and 3-alkyl indolizines from electron-deficient alkenes, pyridines and primary halogenated hydrocarbons is reported for the first time using a tandem reaction.

Synthesis of pyrrolo[2,1,5-cd]indolizines through dehydrogenative Heck annelation of indolizines with diaryl acetylenes using dioxygen as an oxidant

A dehydrogenative Heck annelation reaction of indolizine with diaryl acetylene via dual C-H bond cleavage was developed. Oxygen gas was employed as a clean oxidant in this catalysis under base-free conditions. Diarylpyrrolo[2,1,5-cd]indolizines were synthesized with high atom economy. In addition, kinetic isotope experiments provided evidence for C-H bond metalation of the 5-position of the indolizine as the rate-limiting step.

One-pot synthesis of indolizine via 1,3-dipolar cycloaddition using a sub-equivalent amount of K2Cr2O7 as an efficient oxidant under base free conditions

X = Cl or Br; EWG₁, EWG₂ = electron withdrow group, one-pot reaction, 29 examples, yields from moderate to high, gram scale-up potential confirmed.