Modifizierte Tetrahelicen‐Systeme

Hellwinkel, Dieter; Aulmich, Gerhard; Melan, Michael

doi:10.1002/cber.19761090812

Cited by 15 publications

(8 citation statements)

References 19 publications

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“…Although 1 .+ is considered reasonably stable, it is plagued by slow decomposition, producing colored impurities — the so called ‘blues brothers’ — which complicate spectroscopic analysis . Exploiting the rich chemistry of aromatic amines, back in the 1980s, Hellwinkel and Melan reported an elegant molecular design resulting from the exhaustive introduction of bridging units at the ortho ‐position of triphenylamine, which forces the originally propeller‐shaped scaffold into a virtually planar geometry (Figure b) . Various types of bridged triphenylamines have been reported to date, including carbonyl, ether, thioether, dimethylmethylene, and diphenylmethylene bridges as well as triphenylamines with two fused pentagons .…”

Section: Figurementioning

confidence: 99%

A Spherically Shielded Triphenylamine and Its Persistent Radical Cation

Schaub

Mekelburg

Dral

et al. 2020

Chemistry A European J

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This work reports the design and synthesis of a sterically protected triphenylamine scaffold which undergoes one‐electron oxidation to form an amine‐centered radical cation of remarkable stability. Several structural adjustments were made to tame the inherent reactivity of the radical cation. First, the parent propeller‐shaped triphenylamine was planarized with sterically demanding bridging units and, second, protecting groups were deployed to block the reactive positions. The efficiently shielded triphenylamine core can be reversibly oxidized at moderate potentials (+0.38 V, vs. Fc/Fc+ in CH2Cl2). Spectroelectrochemistry and chemical oxidation studies were employed to monitor the evolution of characteristic photophysical features. To obtain a better understanding of the impact of one‐electron oxidation on structural and electronic properties, joint experimental and computational studies were conducted, including X‐ray structural analysis, electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations. The sterically shielded radical cation combines various desirable attributes: A characteristic and unobstructed absorption in the visible region, high stability which enables storage for weeks without spectroscopically traceable degradation, and a reliable oxidation/re‐reduction process due to effective screening of the planarized triphenylamine core from its environment.

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Section: Figurementioning

confidence: 99%

A Spherically Shielded Triphenylamine and Its Persistent Radical Cation

Schaub

Mekelburg

Dral

et al. 2020

Chemistry A European J

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“…In 1971, Hellwinkel and coworkers described the synthesis of 4H,8H,12H‐benzo[1,9]quinolizino[3,4,5, 6,7‐defg]acridine‐4,8,12‐trione (red core in Figure ) . In this compound, the three aryl rings of a TPA are bridged via carbonyl groups that cause the planarization of the whole system to yield π‐conjugated scaffolds useful for potential applications in several fields .…”

Section: H‐bonded C3‐symmetric Discoticsmentioning

confidence: 99%

C₃‐Symmetrical π‐Scaffolds: Useful Building Blocks to Construct Helical Supramolecular Polymers

Dorca

Matern

Fernández

et al. 2019

Israel Journal of Chemistry

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In this review, we highlight some relevant examples of C3‐symmetrical molecules that have been reported to form supramolecular polymers and helical aggregates. In particular, the number and type of non‐covalent forces are key to bias the supramolecular polymerization leading from a simple isodesmic or cooperative mechanism to a more complex self‐assembly process, i. e. pathway complexity. Furthermore, the attachment of stereogenic centres at the peripheral side chains of the C3‐systems provokes efficient transfer and amplification of chirality phenomena when directional and specific non‐covalent interactions operate. Interestingly, the incorporation of hydrophilic side chains induces the formation of organized aggregates in aqueous media with potential biomedical applications. Overall, the examples shown in this review on C3‐symmetrical scaffolds illustrate the relevance of this molecular shape in the development of functional supramolecular structures.

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“…The synthesis of H 3 L was achieved by a copper-catalyzed Ullman nitrogen arylation, followed by a standard base hydrolysis as described previously. 11 Compounds 1-8 were synthesised by mixing equimolar amounts of the ligand H 3 L and the appropriate metal perchlorate in water, methanol or acetonitrile. NaOH, Ca(OH) 2 or Et 3 N was used as a base to deprotonate H 3 L. Crystals suitable for X-ray crystallography were obtained with the metal ions Fe III , Fe II , Co II , Ni II , Cu II and Zn II .…”

Section: Synthesis and X-ray Structures Of Metal Complexes Of H 3 Lmentioning

confidence: 99%

On, off and intermediate coordination of a bridgehead triarylamine donor in tripodal complexes: Towards the tuning of coordinative bond distance

et al. 2004

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A series of first row transition metal complexes of the tripodal ligand 2,2',2"-nitrilotribenzoic acid H3L has been prepared and characterised by X-ray crystallography: Mononuclear [M(L)]- species [Cu(H2O)4]3[Cu(L)(H2O)]6.25H2O (2), [Co(H2O)6][Co(L)(H2O)].8H2O (4), [Zn(H2O)6][Zn(L)(H2O)].8H2O (5) and a neutral [M(L)] complex [Fe(III)2(L)(H2O)3].5H2O (8) are formed as well as dimeric [M(L)]2 2- species (HNEt3)2[Cu(L)]2.2CH3CN (1), (HNEt3)3[Ni(L)]2(ClO4).H2O (3), (HNEt3)2[Fe(II)(L)]2.2CH3CN (6) and (HNEt3)2[Fe(III)2(L)2(mu-O)](7). The complexes display a unique variation in the M-N distance (2.09 A for Cu(II) to 3.29 A for Fe(III)) to the bridgehead triphenylamine donor and are classified into compounds with "On","Off" and "Intermediate" N-coordination. The trigonal-bipyramidal coordination polyhedron changes towards tetrahedral in the intermediate and octahedral in the Off-state. The M-N distance of individual complexes is reversibly tuned by external chemical input such as changes of metal ion oxidation state (Fe(II)/Fe(III)) or variation of the axial coligand as a consequence of solvent or pH variation. Possible reasons for the exceptional tolerance of the M-N bond to distance variations are discussed under consideration of gas phase DFT calculations of [Zn(L)]-.

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Modifizierte Tetrahelicen‐Systeme

Cited by 15 publications

References 19 publications

A Spherically Shielded Triphenylamine and Its Persistent Radical Cation

A Spherically Shielded Triphenylamine and Its Persistent Radical Cation

C₃‐Symmetrical π‐Scaffolds: Useful Building Blocks to Construct Helical Supramolecular Polymers

On, off and intermediate coordination of a bridgehead triarylamine donor in tripodal complexes: Towards the tuning of coordinative bond distance

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Modifizierte Tetrahelicen‐Systeme

Cited by 15 publications

References 19 publications

A Spherically Shielded Triphenylamine and Its Persistent Radical Cation

A Spherically Shielded Triphenylamine and Its Persistent Radical Cation

C3‐Symmetrical π‐Scaffolds: Useful Building Blocks to Construct Helical Supramolecular Polymers

On, off and intermediate coordination of a bridgehead triarylamine donor in tripodal complexes: Towards the tuning of coordinative bond distance

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C₃‐Symmetrical π‐Scaffolds: Useful Building Blocks to Construct Helical Supramolecular Polymers