Nitrogen-Embedded Multi-Resonance Heteroaromatics with Prolonged Homogeneous Hexatomic Rings
Xuan Zeng1,2, Xiang Wang1, Yuewei Zhang1
1Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
Angewandte Chemie (International Ed. in English)
|January 29, 2022
Summary
Researchers developed novel nitrogen-embedded emitters with homogeneous hexatomic rings, achieving efficient narrowband emission. These materials offer bathochromic shifts and high performance in organic light-emitting diodes.
Area of Science:
- Materials Science
- Organic Chemistry
- Photophysics
Background:
- Nitrogen-containing polycyclic heteroaromatics show multi-resonance (MR) properties for narrowband emission.
- Achieving bathochromic shifts in emission while maintaining narrow bandwidths is challenging.
Purpose of the Study:
- To develop novel emitters with bathochromic shifted narrowband emission.
- To enhance photoluminescence quantum yields and device performance.
Main Methods:
- Incorporation of homogeneous hexatomic rings into nitrogen-embedded MR skeletons.
- Synthesis and characterization of novel emitters.
- Fabrication and testing of organic light-emitting diodes (OLEDs).
Main Results:
- Emitters exhibit near-unity photoluminescence quantum yields.
- Narrowband emission peaks at 598 nm and 620 nm with small full-width-at-half-maximums (28 nm and 31 nm).
- Optimal OLEDs achieved 18.2% external quantum efficiency, negligible roll-off, and long operational lifetime.
Conclusions:
- Homogeneous hexatomic rings effectively prolong π-conjugation for low-energy transitions.
- The developed emitters demonstrate excellent photophysical properties and device stability.
- This strategy offers a promising pathway for advanced narrowband emitters in OLEDs.
Keywords:
Bathochromic ShiftDevice StabilityHomogeneous Hexatomic RingsMultiple ResonanceNarrow Energy GapMore Related Videos
Related Concept Videos
01:13Five-Membered Heterocyclic Aromatic Compounds: Overview
4.5K
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom,...
4.5K
01:18Aromatic Hydrocarbon Cations: Structural Overview
3.2K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
3.2K
01:18Aromatic Hydrocarbon Anions: Structural Overview
3.1K
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
Due to the absence of continuous...
3.1K
01:27¹H NMR: Long-Range Coupling
2.0K
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
2.0K
01:20Criteria for Aromaticity and the Hückel 4n + 2 Rule
11.6K
Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as...
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as...
11.6K
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
947
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
947