Synthesis and Properties of Highly Fluorescent Indolizino[3,4,5-ab]isoindoles

Abstract

We report here the synthesis, X-ray structures, optical and electrochemical properties, fabrication of light-emitting devices, and density functional calculations for indolizino[3,4,5-ab]isoindole (INI) derivatives. Strongly luminescent heterocycles based on the INI unit were synthesized by 1,3-dipolar cycloaddition reactions between pyrido[2,1-a]isoindole (PIS) and acetylene or ethylene derivatives. They are indolizino[3,4,5-ab]isoindoles 2-9 and 14-15, benzo[1',2'-1,2]indolizino[3,4,5-ab]isoindoles 10, pyridazino[4',5':1,2]indolizino[3,4,5-ab]isoindoles 12-13, and 2,3-hydropyridazino[4',5':1,2]indolizino[3,4,5-ab]isoindole-1,4-dione 11. The relative luminescence quantum yield can be as high as 90%. Their reduction and oxidation potentials and high luminescence can make these heterocycles possible alternatives to tris(8-hydroxyquinolinato)aluminum (Alq(3)). The brightness of the light-emitting device reached as high as 10(4) cd/m(2) and indolizino[3,4,5-ab]isoindole 3 emits beautifully blue light. The X-ray crystal structures of INI derivatives were obtained for the first time. The geometries obtained from X-ray data and density functional theory calculations shed more light on an interesting formally antiaromatic 16pi system, which is divided into 10pi and 6pi aromatic systems. We also report a relatively easy protonation of INI, which occurs at a carbon, rather than nitrogen atom.

Studies on Cage‐Type Tetranuclear Metal Clusters with Ferrocenylphosphonate Ligands

“…[47][48] Frontier orbital theory may provide an explanation for such behavior. [50] In 2, the HOMO is associated with the phen ligands and Zn II orbitals, and the charge transitions of the tetranuclear metal cores may play an important role in the change of the Fe II /Fe III oxidation potential. The HOMO in 1 is located in the FMPA 2À groups, so the Fe II centers of 1 are more easily oxidized to Fe III than those in complex 2.…”

Electro-Organic Synthesis and Characterization of New Dihydroxybenzene Dinitrile Derivatives with Fluorescent Properties

“…The synthesis and the biological applications of fluorescent compounds have previously been investigated. [3][4][5][6][7][8] It has been shown that the quinone/hydroquinone redox couple can interconvert reversibly by exchanging two protons and two electrons. This characteristics enables it to serve as an antenna or the control subunit, which affects the absorption or the emission optical properties of the compound.…”

Synthesis and Emitting Properties of the Blue‐Light Fluorophores Indolizino[3,4,5‐ab]isoindole Derivatives

“…The starting materials 4a-4c were prepared by the 1,3-dipolar cycloadditions of isoquinolinium carboxymethylide with the corresponding alkynes. [16] Their reactions with 1 under the same conditions as described above for the reactions of 2a-2k with 1 gave the corresponding benzo [6,7]pyrrolizino [3,4,5-ab]isoquinolines 5a-5c as red solids, respectively, in 52-60 % yield ( Table 2). Compounds 5a-5c have strong molecular ion peaks in their MS spectra, with 5b and 5c having this peak as the base peak.…”

“…[7] Therefore, further investigation of their luminescence-structure rela-properties of these compounds have been investigated by cyclic voltammetry. Indolizino [3,4,5-ab]isoindoles without a substituent at C-2 (compounds 3a, 3c, 3d) or with an alkyl substituent in the framework (3i, 3k) undergo irreversible anodic oxidations and reversible cathodic reductions.…”

“…[8a,11] The benzyne precursor used in these reactions was 2-(phenyliodonio)benzoate and the yields of the benzo-and dibenzo-annulated indolizino [3,4,5-ab]isoindole products are in the range of 18-39 %. [11] To the best of our knowledge, there has so far been no systematic investigation into the synthesis of indolizino [3,4,5- [7] We envisioned that the cycloadditions of the easily accessible substituted indolizines with benzyne generated from the 2-trimethylsilyl trifluoromethanesulfonate precursor 1, [12] would provide a general and versatile synthesis of indolizino [3,4,5-ab]isoindole derivatives with different substitution patterns under mild conditions. Hence, we have synthesized a series of indolizino [3,4,5-ab]isoindole derivatives by this method and further investigated their fluorescence and electrochemical properties, as well as their electronic structure by molecular orbital calculations, because of their potential applications as blue and green light-emitting fluorophores and electroluminescent materials for OLED devices.…”