Fluorescent mesomorphic pyrazinacenes

Richards, Gary J.; Ishihara, Shinsuke; Labuta, Jan; Miklík, David; Mori, Toshiyuki; Yamada, Shinji; Ariga, Katsuhiko; Hill, Jonathan P.

doi:10.1039/c6tc04628b

Cited by 11 publications

(18 citation statements)

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“…In our previous work on the pyrazinacene systems, we have prepared mostly unsymmetrically substituted compounds , . This was initially as a result of our use of the reaction of 2,3‐diamino‐5,6‐dicyanopyrazine (DADCP) with 1,2‐diketones, such as benzil derivatives, where the synthesis naturally provides different groups at the terminal ends of the molecules.…”

Section: Resultsmentioning

confidence: 99%

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a Ru^II(2,2′‐bpy)₂ Derivative

et al. 2018

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We report the one-pot synthesis of a phenanthroline-fused pyrazinacene derivative (6,13-dihydrodipyrido-[3,2-a:2′,3′-c]-5,6,7,8,11,12,13,14-octaazapentacene-9,10-dicarbonitrile) and its behaviour under alkylating conditions used to improve solubility. Tautomerization of the starting pyrazinacene due to the presence of a reduced pyrazine ring contained within an octaazatetracene chromophore led to mixtures of isomers, and factors affecting the relative yields of these isomers were considered. Isomer population can be described by a two- [a]

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Section: Resultsmentioning

confidence: 99%

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a Ru^II(2,2′‐bpy)₂ Derivative

et al. 2018

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“…Furthermore, we observed the tendency for tautomerism in the N-alkylation only of those pyrazinacenes containing more than six nitrogen atoms. Fluorubine-type compounds, for instance, are N-alkylated leading to single symmetrically 6,13-disubstituted products 4,44 (other isomers are possible by different synthetic methods 59 ), while N-alkylation on compounds such as 4, 10, or 11 yields three isomers (Figure 6b). 46,58 This is consistent with our calculations, which suggest that protons tend not to reside on terminal pyrazine units so that distributions of products of N-alkylation reactions favor products with N-alkyl groups on nonterminal rings.…”

Section: Tautomers Of Pyrazinacenesmentioning

confidence: 99%

Section: Redox States Of Pyrazinacenesmentioning

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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“…Synthesis. Pyrazinacene-type molecules bearing N-substituents have been prepared previously and are known to be highly fluorescent molecules with potential applications beyond the usual acene-type applications [19][20][21][25][26][27][28][29] . Decaazapentacenes (DAP, see Fig.…”

Section: Resultsmentioning

confidence: 99%

Pyrazinacenes exhibit on-surface oxidation-state-dependent conformational and self-assembly behaviours

et al. 2021

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Acenes and azaacenes lie at the core of molecular materials’ applications due to their important optical and electronic features. A critical aspect is provided by their heteroatom multiplicity, which can strongly affect their properties. Here we report pyrazinacenes containing the dihydro-decaazapentacene and dihydro-octaazatetracene chromophores and compare their properties/functions as a model case at an oxidizing metal substrate. We find a distinguished, oxidation-state-dependent conformational adaptation and self-assembly behaviour and discuss the analogies and differences of planar benzo-substituted decaazapentacene and octaazatetracene forms. Our broad experimental and theoretical study reveals that decaazapentacene is stable against oxidation but unstable against reduction, which is in contrast to pentacene, its C–H only analogue. Decaazapentacenes studied here combine a planar molecular backbone with conformationally flexible substituents. They provide a rich model case to understand the properties of a redox-switchable π-electronic system in solution and at interfaces. Pyrazinacenes represent an unusual class of redox-active chromophores.

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Fluorescent mesomorphic pyrazinacenes

Abstract: Hexaazapentacene derivatives were N-substituted with hydrophilic and hydrophobic dendron-type substituents leading to different self-assembly behaviours including lamellar and columnar structures.

Cited by 11 publications

References 146 publications

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a Ru^II(2,2′‐bpy)₂ Derivative

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a Ru^II(2,2′‐bpy)₂ Derivative

The Pyrazinacenes

Pyrazinacenes exhibit on-surface oxidation-state-dependent conformational and self-assembly behaviours

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Fluorescent mesomorphic pyrazinacenes

Abstract: Hexaazapentacene derivatives were N-substituted with hydrophilic and hydrophobic dendron-type substituents leading to different self-assembly behaviours including lamellar and columnar structures.

Cited by 11 publications

References 146 publications

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a RuII(2,2′‐bpy)2 Derivative

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a RuII(2,2′‐bpy)2 Derivative

The Pyrazinacenes

Pyrazinacenes exhibit on-surface oxidation-state-dependent conformational and self-assembly behaviours

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Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a Ru^II(2,2′‐bpy)₂ Derivative

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a Ru^II(2,2′‐bpy)₂ Derivative