Aza[6]helicene Platinum Complexes: Chirality Control of <i>cis–trans</i> Isomerism

Mendola, Daniele; Saleh, Nidal; Vanthuyne, Nicolas; Roussel, Christian; Toupet, Loı̈c; Castiglione, Franca; Caronna, Tullio; Mele, Andrea; Crassous, Jeanne

doi:10.1002/ange.201401004

Cited by 12 publications

(10 citation statements)

References 41 publications

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“…found twice as high as for 4-aza [6] 99 in agreement with the presence of two azahelicene moieties. Note that a similar strategy was applied by Srebro-Hooper, Crassous, et al to the preparation of helicene-bipy 51 (Scheme 13 and Table 6).…”

Section: Basesupporting

confidence: 67%

“…Later on in 2014, the coordination of 4-aza [6]helicene 41a 4 to square planar platinum(II) revealed a new aspect of reactivity in chiral transition metal complexes. 99 Indeed, our group has observed that cis-[PtCl 2 (NCEt)PPh 3 ] (cis-109) reacted differently with either racemic or enantiopure 4-aza [6]helicene 41a 4 giving respectively cis (racemic, 110) and trans (enantiopure, 110') [PtCl 2 (41a 4 )PPh 3 ] complexes (Scheme 27). This unexpected reactivity is explained through a dynamic process (crystallization-induced diastereoselective transformation).…”

Section: Coordination Chemistry Of Pyridohelicenesmentioning

confidence: 99%

“…X-ray crystallographic structure of cis-110 (one enantiomer is shown) and dihedral angles used to define the (M) planar chirality around the Pt center. 99 2,2'-Bipyridine ligands are classical N^N chelate ligands 151 but can also act as C^N ones toward different transition metal ions such as platinum. 152 In 2015, Autschbach, Crassous, et al reported the preparation of enantiopure helical cycloplatinated complexes (P)-and (M)-111 from a [6]helicenebipyridine-type ligand, namely 3-(2-pyridyl)-4-aza [6]helicene ((P)-and (M)-51 in Scheme 28).…”

Section: Coordination Chemistry Of Pyridohelicenesmentioning

confidence: 99%

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Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

2019

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In this review, we discuss the rich chemistry of helicenes and helicenoids containing maingroup elements. Enantioenriched helicenic derivatives containing main-group elements B, Si, N and P, either incorporated within the helical backbone or grafted to it, will be thoroughly presented. We will describe their synthesis, resolution, and asymmetric synthesis, their structural features, electronic and chiroptical properties, emission, together with other photochemical properties and applications. OUTLINE 14 The absorption spectrum of 19c recorded in CH 2 Cl 2 solutions exhibited a maximum at 376 nm which is significantly red shifted compared with that of double [5]helicene 19a (310 nm) due to the more extended π-conjugation in 19c. According to TD-DFT calculations, the low-energy absorption band from 400 to 500 nm is assignable to the HOMO→LUMO transition corresponding to a π−π* transition of the fully conjugated bis-helical system. DFT calculations revealed a very high theoretical isomerization barrier of 45.1 kcal/mol for the (P,P)/(M,M)-19c stereoisomer, i.e. 4.4 kcal/mol higher than the (P,M) stereoisomer (not observed experimentally). The high configurational stability of 19c enabled to obtain the pure (P,P)and (M,M)-19c by chiral HPLC (Daicel Chiralcel IE column; EtOAc/MeOH = 9:1 as eluent) and to study their chiroptical properties. The ECD spectrum of (P,P)-19c in CH 2 Cl 2 displayed two strong positive bands at 275 and 320 nm, a strong negative one at 375 nm and a broad and less intense one between 425-475 nm. 52 Note that the isomerization barrier of the OBO-fused double [7]helicene is much higher than for oxabora[6]helicene 9 (vide supra) and higher than carbo[7]helicene (42.0 kcal/ mol), indicating the advantage of double helicenes over monohelicenes in terms of conformational stability. Indeed no racemization was observed upon heating enantiomer (P,P) and (M,M)-19c for 24 h up to 200 °C. 52 Note that in 2017 a longer double OBO-helicene analogue was deposited on a Au(111) under UHV conditions and its surface-assisted cyclodehydrogenation into a planar OBO-perihexacene was observed by STM. 54 Similarly to 6 and 9, the strong bond alternation found in the BOC4 rings of 19a 51 may account for the small NICS value of 1.3 while the surrounding C6 rings, including the distorted central benzene ring, show large negative NICS values (Scheme 3c). For comparison, in the all-carbon analogue tetrabenzo-[a,f,j,o]perylene shown in Scheme 3c, the central C6 ring shows a positive NICS value, indicating substantial antiaromatic character. Notably, molecular orbital calculations of 19a indicate that the HOMO and LUMO are spread over the C6 rings rather than on the boron and oxygen atoms, accounting for the substantial stability of 19a (Scheme 3c). Borahelicenes are efficient blue fluorophores. Indeed, azabora[6]helicene 6 displays blue fluorescence at 447 nm (Table 2), while smaller achiral [4]helicenic systems were successfully used as host materials in phosphorescent OLEDs with efficiencies better than the classical 4,4'...

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Section: Basesupporting

confidence: 67%

Section: Coordination Chemistry Of Pyridohelicenesmentioning

confidence: 99%

Section: Coordination Chemistry Of Pyridohelicenesmentioning

confidence: 99%

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Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

2019

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“…Along with racemic pyrido[ n ]helicenes ( n =5,6,7) and their derivatives, both enantio‐ and diastereomerically pure pyrido[ n ]helicene‐like molecules ( n =5,6) were prepared by employing the chiral substrate‐controlled cyclisation of the corresponding enantiopure cyanodiynes. It establishes a new methodology for the preparation of attractive pyridohelicenes and their analogues,, which have already been studied theoretically as well as experimentally in the context of basicity,, coordination chemistry, organocatalysis, chiroptical properties, dynamic behaviour, thermopower, or photonics …”

Section: Discussionmentioning

confidence: 99%

[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

Klívar

Jančařík

Šaman

et al. 2016

Chemistry A European J

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We have developed a methodology for the synthesis of pyridohelicenes and their analogues based on the Ni(0) -, Co(I) - or Rh(I) -mediated intramolecular [2+2+2] cycloisomerisation of cyanodiynes. It allows for folding the linear precursors into the corresponding helical backbones comprising the newly formed pyridine unit in their central part. Along with racemic pyrido[n]helicenes (n=5,6,7) and their derivatives, both enantio- and diastereomerically pure pyrido[n]helicene-like molecules (n=5,6) were prepared by employing the chiral substrate-controlled cyclisation of the corresponding enantiopure cyanodiynes.

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“…The understanding and use of this effect is one of the pillars for the improvement of synthetic and predictive capabilities of inorganic chemists. Particularly, the trans influence, can be studied in different ways . If the atom of the ligand interacting directly with the metal center is an NMR active species, this technique becomes a powerful tool to get insights into this phenomenon .…”

Section: Introductionmentioning

confidence: 99%

Stability andtransInfluence in Fluorinated Gold(I) Coordination Compounds

et al. 2018

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We examined the Au–P and Au–X chemical bonding scenario throughout the series of compounds of the general formula [AuX(LP)] wherein LP is triphenylphosphine or a fluorinated phosphine [PPhF = P(C6H5)2(C6F5) 1, P(C6H5)(C6F5)2 2 and P(C6F5)3 3] and X is chloride or a fluorinated thiolate [SRF = SCF3 a, SCH2CF3 b, SC6F5 c, SC6F4(CF3)‐4 d]. We found that the increase of the fluorination degree or the replacement of Cl– by a –SRF ligand decreases the stability of the compound. Furthermore, this substitution shifts the 31P‐NMR signals to low field, which indicates differences in the electronegativity of the phosphorus due to the distinct trans influences of the Cl– and –SRF species. These effects correlate with the charge of the gold atom coordinated to phosphorus. Our investigation shows the high potential of fluorination as a strategy for the modulation of the properties of gold compounds, for example in catalysis, and the applicability of quantum chemical topology studies in the explanation of these features.

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Aza[6]helicene Platinum Complexes: Chirality Control of cis–trans Isomerism

Cited by 12 publications

References 41 publications

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

Stability andtransInfluence in Fluorinated Gold(I) Coordination Compounds

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