Recent progress in well-defined higher azaacenes (<i>n</i>≥ 6): synthesis, molecular packing, and applications

Zhang, Zhongbo; Zhang, Qichun

doi:10.1039/c9qm00656g

Cited by 80 publications

(41 citation statements)

References 77 publications

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“…For instance, unsubstituted heptacene has only been studied using matrix-isolation methods, and the higher homologues nonacene and decacene are only available for study following synthesis at a stabilizing metal surface. The poor stabilities of the higher acenes has been addressed to some extent either by introducing sterically bulky or other groups − or, of interest here, by the introduction of heteroatoms, in particular, nitrogen . Nitrogen-containing heteroacenes, or N-heteroacenes, , are now available as extensively extended polycyclic materials with excellent stabilities attesting to the utility of the heteroatom approach for the development of acene chemistry.…”

Section: Introductionmentioning

confidence: 99%

The Pyrazinacenes

Richards

Hill

2021

Acc. Chem. Res.

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Conspectus Pyrazinacenes are a class of nitrogen-containing heteroacene molecules composed of linearly fused pyrazine units, which might also include dihydropyrazine groups leading to different reduced states of the compounds. While they are structurally similar to hydrocarbon acenes (e.g., pentacene) the presence of increasing numbers of N-heteroatoms introduces several different additional features of the compounds so that they can be considered for investigations beyond those suggested for acenes (i.e., organic field-effect transistors, solar cell components). Pyrazinacenes are in several ways complementary to C–H-only acenes based on the increasing stability of reduced states of the compounds with increasing numbers of fused pyrazine rings, although an acene-like electronic structure persists in the compounds so far studied. However, the introduction of multiple N atoms leads to properties that depart from C–H-only acenes. In particular, the compounds exhibit a delocalization of NH protons in extended reduced compounds and oxidation state switchability in solution and at interfaces. The presence of NH groups also allows an easy introduction of solubilizing groups at the pyrazinacene chromophore. In this Account, we will describe the preparation of extended pyrazinacenes from dipyrazino[2,3-b:2′,3′-e]pyrazine (1,4,5,8,9,10-hexaazaanthracene; N6) derivatives up to 1,4,5,6,7,8,9,12,13,14,15,16,17,18-tetradecaazaheptacene (N14) and also assess structures of the relevant compounds based on X-ray crystallographic studies. Emergent properties of the molecules include highly unusual linear tautomeric processes based on a delocalization of protons (and the corresponding formation of orbitals based on multiple adjacent N lone electron pair interactions), which suggest special transport properties based on molecular protonics. Molecules such as decazapentacene (N10) exhibit multistability of oxidation state, and this is predicted to promote the redox catalytic properties of the compounds. The oxidation-state switching of on-surface processes is also described and has been investigated using scanning tunneling microscopy. The longest known pyrazinacene chromophore (N14) exhibits amphiprotism with its state of protonation being strongly coupled to its fluorescence emission properties in the near-infrared region indicating possible uses in pH-coupled bioimaging applications. The synthesis of the pyrazinacenes is flexible and allows the preparation of symmetrically or unsymmetrically substituted derivatives for the development of more complex molecules and for control of the electronic structure of the acene unit. Overall, the pyrazinacenes represent an emerging class of highly nitrogenous heteroacenes with unique properties and excellent potential for development in different applications based on their special supramolecular properties including guest binding or interactions in biological systems.

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Section: Introductionmentioning

confidence: 99%

The Pyrazinacenes

Richards

Hill

2021

Acc. Chem. Res.

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“…First syntheses of azaacenes were reported at the end of 19th century by Fischer and Hepp [ 38 , 39 ]. These research efforts were then continued through the 20th century and significantly intensified in recent years [ 40 , 41 ].…”

Section: Synthesis Of Azaacenesmentioning

confidence: 99%

Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications—A Critical Review

2021

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This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc+. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300-310) to yield, for the first time, a set of normalized data, which could be directly compared.

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“…5 However, due to the high requirements of these applications, a series of material systems with excellent performances, which generally consists of a considerable number of aromatic rings and related fused structures, has been developed. 6–8 Especially, polycyclic aromatic hydrocarbons (PAHs) have become molecular libraries of organic semiconductor materials and popular material systems due to their inherent conjugated structure and strong intermolecular interaction, which result in favorable solid stacking. As a representative molecule, pentacene delivered a hole mobility of over 5 cm 2 V −1 s −1 due to its extended π-conjugated structure with ideal molecular packing.…”

Section: Introductionmentioning

confidence: 99%

Polycyclic aromatic hydrocarbon-based organic semiconductors: ring-closing synthesis and optoelectronic properties

Zhang

Xie

et al. 2022

J. Mater. Chem. C

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Recent progress in well-defined higher azaacenes (n≥ 6): synthesis, molecular packing, and applications

Abstract: In this review, we will focus on the recent progress in the synthetic strategies, photo-electronic properties, molecular packing modes and applications of azaacenes (n ≥ 6) with single-crystal structures.

Cited by 80 publications

References 77 publications

The Pyrazinacenes

The Pyrazinacenes

Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications—A Critical Review

Polycyclic aromatic hydrocarbon-based organic semiconductors: ring-closing synthesis and optoelectronic properties

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