Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA+): A [4]Helicene with Multiple Redox States

Sørensen, Thomas Just; Nielsen, Merete Folmer; Laursen, Bo W.

doi:10.1002/cplu.201402058

Cited by 44 publications

(70 citation statements)

References 52 publications

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“…Under reductive conditions, a reversible event corresponding to the reduction of DMQA+ to DMQA• is observed around E1/2 = -1.25 V in 2 + -5 +. [32] This event is observed at a higher potential for 2-NO2+ (--1.05 V), consistent with a more electron de cient scaffold and a reduced reactivity toward oxygen due to the presence of the NO2 group. A second redox event corresponding to the reduction of DMQA • to DMQAwas also present.…”

Section: -No2• 3 •-5 •mentioning

confidence: 60%

“…The UV−visible spectra of the cations and radicals (2-5) were studied to futher probe the electronic structures of these molecules (Figure 3a). The blue shifted absorptions of the radicals compared to their cation analogs (Figure 3a (i) and (ii)) indicate a reduced involvement of the heteroatoms in the molecular framework and a reduced conjugation across thesystem, [32] consistent with the increased distortion observed in solid state (vide supra).. The stability of 2•-5• toward molecular oxygen was monitored upon exposure of their solution to air (2-H• Figure 3b) and Figure S47, S49, S51, S53).…”

Section: Resultsmentioning

confidence: 97%

“…A second redox event corresponding to the reduction of DMQA • to DMQAwas also present. [32] This was observed as a reversible process at E1/2 = -1.85 V for 2-NO2+, and irreversible for 2-H + , 3 + -5 +, at E1/2 = -2.3 V. [32] Photocatalysis. The estimated excited state oxidation potential of 2-H • E1/2(C + /C •* ) = -2.79 V vs SCE, See SI) suggests a highly photoreducing species.…”

Section: -No2• 3 •-5 •mentioning

confidence: 99%

“…To the best of our knowledge, only four examples of [4]helicene radicals have been reported. [30][31] [32][33] Of these radicals, two showed limited stability, [30] [31] and one was never isolated. [32] Notably, no X-ray crystallographic structure of any [4]helicene-based neutral radical has been reported.…”

Section: Introductionmentioning

confidence: 99%

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Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

Shaikh

Hossain

Moutet

et al. 2020

Preprint

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Stable organic radicals have gained considerable attention in the fields of catalysis and material sciences. In particular, helical molecules are of great interest in the development and application of novel organic radicals in optoelectronic and spintronic materials. Here we report the syntheses of highly stable neutral quinolinoacridine radicals by chemical reduction of their quinolinoacridinium cation analogs. The crystal structures of these [4]helicene radicals were determined by X-ray diffraction. Electron paramagnetic resonance (EPR) measurements, supported by density functional theory (DFT) calculations, indicate that the unpaired electron is mostly localized, showing more than 40% of spin density located at the central carbon of the [4]helicene radicals. Quantitative conversion from neutral radical to cation is observed upon exposure to air, monitored via UV-vis spectroscopy. The successful photoreductive dehalogenation of aryl halides occurs in the presence of 10 mol% of [4]helicene radical under blue light.

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Section: -No2• 3 •-5 •mentioning

confidence: 60%

Section: Resultsmentioning

confidence: 97%

Section: -No2• 3 •-5 •mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

Shaikh

Hossain

Moutet

et al. 2020

Preprint

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“…[15a,b,d,18] The phenolate group is an efficient photoinduced electron transfer quencher (Figures S22 and S24, Supporting Information); therefore, the fluorescence intensity decreases with increasing pH. The reference dye is the red emitting dimethoxyquinacridinium (DMQA) fluorophore . Emission spectra of the physisorbed pH‐responsive DAOTA dye 3a (methylsufonyl variant) and the DMQA reference dye 4 are shown in Figure .…”

Section: Sensor Characteristics For Optodes Made From the Methyl‐sulfmentioning

confidence: 99%

A Fluorescence Intensity Ratiometric Fiber Optics–Based Chemical Sensor for Monitoring pH

Rosenberg

Laursen

Frankær

et al. 2018

Adv Materials Technologies

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Accurate determination of pH is essential, yet a single technology is relied upon for almost all pH measurements. Here, a new optical pH sensor is described. Two highly photostable fluorescent dyes with a polymerizable side chain are incorporated into a composite polymer that allows for fast transport of protons. A pH‐responsive dye and a reference dye with limited response to pH are used, thus allowing for determining pH using a ratiometric fluorescence intensity response. The sensor material—dyes covalently attached in the composite polymer—is deposited on a polycarbonate hemiwicking substrate, and immobilized on the inside of a shaker flask. In this manner, two robust pH optodes with pKa values of 5.30 and 6.11 are prepared. The pH‐responsive composite materials are addressed using fiber optics, and the response is recorded on a fiber spectrometer. The optodes are shown to have low drift, fast response time, no leachables, and the sensor is shown to work in heterogeneous media exemplified with coffee, beer, and cola.

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Structure and Property Diversity of Chiral Helicene Oligomers

Saito

Shigeno

Yamaguchi

2015

Encyclopedia of Polymer Science and Technology

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alkylthio, and perfluoroalkyl groups. In addition, cyclization of helicene oligomers provides another method of obtaining diversity.A notable aspect in the diversity of helicene oligomers is that they can be connected to provide multidomain oligomers (Fig. 4). When two helicene oligomers are connected, they are referred to herein as homo-bidomain oligomers. Cyclic homo-bidomain oligomers are also conceivable. Hetero-multidomain oligomers can be obtained by connecting different structures of oligomers. Such manipulations provide a large diversity of structures.Because helicene can generate characteristic π−π interactions, helicene oligomers often form bimolecular, trimolecular, tetramolecular, and polymolecular aggregates in which homoaggregation and heteroaggregation can also occur. Such aggregates self-assemble to form fibrils, vesicles, liquid crystals, and surface monolayers. These noncovalent bonding interactions provide diversity of the structure of helicene oligmers. Diverse Properties of Helicene OligomersStructural diversity is directly related to diversity of properties, and the properties of a helicene oligomer can be varied by structural modifications. In addition, multidomain oligomers can be designed, in which properties A and B of each domain can be combined. Such compounds exhibit property A + B or even another property C, a result regarded as the "synthesis of a property or function." Aggregation and self-assembly of helicene oligomers further increase property diversity, which covers materials with a broad range of sizes from subnanometersized molecules through nano-and micrometer-sized molecular aggregates and molecular self-assemblies to macroscopic bulk materials. Helicene oligomers are sensitive to changes in the environment such as temperature, solvent, and concentration. Different properties appear in dilute solution, in concentrated Amidohelicene oligomers: (a) acylcic oligomers (P)-1 (n = 1−9) with dianiline spacer, cyclic oligomers (P)-2 (n = 1−10) with dianiline spacer, (b) acyclic oligomers (P)-3 (n = 1−9) with m-phenylene spacer, and acyclic reverse oligomers (P)-4 (n = 1−4). (c) Schematic representation of reversible change between helix dimer and random coils of (P)-3 and (P)-4. solution, in the crystalline state, in the amorphous state, on the solid surface, at the solid-liquid interface, in fiber assemblies, in liquid crystals, and in gels. Dynamic properties of helicene oligomers are also interesting, and structural changes are largely affected by the environment, providing a stimulus response or possible molecular switching materials. It is also noteworthy that the process of a structure change can produce unusual transient phenomena. Amidohelicene OligomersStudies on helicene oligomers were initiated with amide derivatives (Fig. 5a, top), in which the spacer has a bent shape and includes both hydrogen bonding donor and acceptor moieties (24). (P)-5,8-Helicenedicarboxylate was reacted with bis(2,6-dimethylanilino)cyclohexane to give a series of acyclic helicene oligomers 1 up t...

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Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

Cited by 44 publications

References 52 publications

Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

A Fluorescence Intensity Ratiometric Fiber Optics–Based Chemical Sensor for Monitoring pH

Structure and Property Diversity of Chiral Helicene Oligomers

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