Publications by authors named "Nicolas Vanthuyne"

173 Publications

Synthesis and Optical Resolution of Configurationally Stable Zwitterionic Pentacoordinate Silicon Derivatives.

Angew Chem Int Ed Engl 2021 Nov 12. Epub 2021 Nov 12.

Institut Parisien de Chimie Moléculaire, Sorbonne Université, CNRS, 4 Place Jussieu, CC 229, F-75252, Paris Cedex 05, France.

Stereogenic silicon centres in functionalised tetracoordinated organosilanes generally exhibit very high configurational stability under neutral conditions. This stability drops completely when higher coordination states of the silicon centre are reached due to rapid substituent exchange. Herein we describe the synthesis of chiral and neutral pentacoordinate silicon derivatives with high configurational stability. The zwitterionic nature of these air- and water-tolerant species allows for the first time their direct and efficient optical resolution using chiral HPLC techniques. By means of this method, pentacoordinate silicon compounds exhibiting high Si-inversion have been obtained as single enantiomers. A rationalisation of the enantiomerisation pathways has been also carried out using DFT calculations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202113836DOI Listing
November 2021

Enzymatic activity monitoring through dynamic nuclear polarization in Earth magnetic field.

J Magn Reson 2021 Dec 27;333:107095. Epub 2021 Oct 27.

Magnetic Resonance of Biological Systems, UMR5536 University of Bordeaux-CNRS, Bordeaux, France.

Cost-effective and portable MRI systems operating at Earth-field would be helpful in poorly accessible areas or in developing nations. Furthermore Earth-field MRI can provide new contrasts opening the way to the observation of pathologies at the biochemical level. However low-field MRI suffers from a dramatic lack in detection sensitivity even worsened for molecular imaging purposes where biochemical specificity requires detection of dilute compounds. In a preliminary spectroscopic approach, it is proposed here to detect protease-driven hydrolysis of a nitroxide probe thanks to electron-nucleus Overhauser enhancement in a home-made double resonance system in Earth-field. The combination of the Overhauser effect and the specific enzymatic modification of the probe provides a smart contrast reporting the enzymatic activity. The nitroxide probe is a six-line nitroxide which lines are shifted according to its substrate/product state, which requires quantum mechanical calculations to predict EPR line frequencies and Overhauser enhancements at Earth field. The NMR system is equipped with a 13-mT prepolarization coil, a 153-MHz EPR coil and a 2-kHz NMR coil. Either prepolarized NMR or DNP-NMR without prepolarization provide NMR spectra within 3 min. The frequency dependence of Overhauser enhancement was in agreement with theoretical calculations. Protease-mediated catalysis of the nitroxide probe could only be measured through the Overhauser effect with 5 min time resolution. Future developments shall open the way for the design of new low-field DNP-MRI systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jmr.2021.107095DOI Listing
December 2021

Transition metal complexes bearing atropisomeric saturated NHC ligands.

Chirality 2021 Nov 5. Epub 2021 Nov 5.

Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.

From achiral imidazolinium salts, chiral transition metal complexes containing an N-heterocyclic carbene (NHC) ligand were prepared (metal = palladium, copper, silver, gold, rhodium). Axial chirality in these complexes results from the formation of the metal-carbene bond leading to the restriction of rotation of dissymmetric N-aryl substituents about the C-N bond. When these complexes exhibited a sufficient configurational stability, a resolution by chiral high-performance liquid chromatography (HPLC) on preparative scale enabled isolation of enantiomers with excellent enantiopurities (>99% ee) and good yields. A study of the enantiomerization barriers revealed the effect of the backbone nature as well as the type of transition metal on its values. Nevertheless, the evaluation of palladium-based complexes in asymmetric intramolecular α-arylation of amides demonstrated that the ability to induce an enantioselectivity cannot be correlated to the configurational stability of the precatalysts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chir.23378DOI Listing
November 2021

Chiroptical properties of anionic and neutral nickel(II) bis(dithiolene) complexes based on methyl and dimethyl-dddt ligands.

Chirality 2021 Oct 23. Epub 2021 Oct 23.

Univ Angers, CNRS, MOLTECH-Anjou, SFR MATRIX, F-49000 Angers, France.

Racemic and enantiopure nickel(II) bis(dithiolene) anionic and neutral complexes based on the methyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (me-dddt) and dimethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm-dddt) ligands have been experimentally and theoretically investigated with a special focus on their chiroptical properties. According to the time-dependent density-functional theory (TD-DFT) calculations, the strong near-infrared absorption bands typical for such complexes are only weakly active in circular dichroism (CD), and moreover, they have opposite signs for the axial and equatorial conformations, due to the variation of the angle between the transition electric and magnetic dipole moments, thus leading to the mutual cancellation of their contributions and the absence of these bands in the experimental CD spectra. The influence of the number of stereogenic centers and of the oxidation state of the complexes on their chiroptical properties is highlighted. The solid-state structure of the complex (TMA)[Ni(rac-me-dddt) ] (TMA = tetramethylammonium), determined by single-crystal X-ray diffraction analysis, shows a rather unusual cis arrangement of the two dithiolene ligands, with the methyl substituents adopting an axial conformation, which is not the most stable one in the gas phase.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chir.23375DOI Listing
October 2021

Luminescent Chiral Exciplexes with Sky-Blue and Green Circularly Polarized-Thermally Activated Delayed Fluorescence.

Chemistry 2021 Nov 25;27(66):16505-16511. Epub 2021 Oct 25.

Univ. Rennes, CNRS, ISCR - UMR 6226, 35000, Rennes, France.

Luminescent exciplexes based on a chiral electron donor and achiral acceptors are reported as a new approach to design circularly polarized (CP) and thermally activated delayed fluorescence (TADF) emitters. This strategy results in rather high CP luminescence (CPL) values with g up to 7×10 , one order of magnitude higher in comparison to the CPL signal recorded for the chiral donor alone (g ∼7×10 ). This increase occurs concomitantly with a CPL sign inversion, as a result of the strong charge-transfer emission character, as experimentally and theoretically rationalized by using a covalent chiral donor-acceptor model. Interestingly, blue, green-yellow and red chiral luminescent exciplexes can be obtained by modifying with the electron accepting character of the achiral unit while keeping the same chiral donor unit. These results bring new (inter)molecular guidelines to obtain simply and efficiently multi-color CP-TADF emitters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.202102765DOI Listing
November 2021

Hemicryptophane Cages with a -Symmetric Cyclotriveratrylene Unit.

J Org Chem 2021 Nov 1;86(21):15055-15062. Epub 2021 Oct 1.

Aix Marseille Univ, CNRS, Centrale Marseille iSm2, 13284 Marseille, France.

Two new hemicryptophanes combining a cyclotriveratrylene unit with either an aminotrisamide or a tris(2-aminoethyl)amine (tren) moiety have been synthesized. Although a conventional synthesis approach was used, the molecular cages obtained are devoid of the expected symmetry. NMR analyses and X-ray crystal structure determination showed that these hemicryptophanes exhibited symmetry due to the unusual arrangement of the substituents of the cyclotriveratrylene unit. This unprecedented arrangement is related to a change in the regioselectivity of the Friedel-Crafts reactions that led to the CTV cap. This constitutes an original approach to access enantiopure chiral molecular cages with low symmetry.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.joc.1c01731DOI Listing
November 2021

Exciton coupling chirality in helicene-porphyrin conjugates.

Chem Commun (Camb) 2021 Oct 14;57(82):10743-10746. Epub 2021 Oct 14.

Univ Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France.

Enantiopure helicene-porphyrin conjugates were prepared. They show strong changes in their circular dichroic response as compared to classical helicene derivatives, with highly intense bisignate Exciton Coupling (EC) signal and Δ values up to 680 M cm for the Soret band. They also display circularly polarized fluorescence in the (far-)red region, with dissymmetry factors up to 7 × 10.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d1cc03314jDOI Listing
October 2021

Helical donor-acceptor platinum complexes displaying dual luminescence and near-infrared circularly polarized luminescence.

Dalton Trans 2021 Oct 5;50(38):13220-13226. Epub 2021 Oct 5.

Institute for Chemical Research (CSIC-US), C/Américo Vespucio 49, E-41092 Seville, Spain.

A series of chiral platina[5]helicenes displaying dual luminescence, , fluorescence between 450 and 600 nm and red/NIR phosphorescence between 700 and 900 nm, has been synthesised, characterised and studied by first-principle calculations. This unusual behavior has been attributed to limited electronic interactions between the d orbitals of the metal and the π-orbitals of the organic ligand on the excited-state. Accordingly, the electron richness of the donor group on the helical ligand does not affect the energy of the phosphorescence process but does play a role on its efficiency. Interestingly, near-infrared circularly polarized luminescence can be obtained for the three complexes with dissymmetry factors up to 3 × 10 at 750 nm.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d1dt02184bDOI Listing
October 2021

Enantioenriched Ruthenium-Tris-Bipyridine Complexes Bearing One Helical Bipyridine Ligand: Access to Fused Multihelicenic Systems and Chiroptical Redox Switches.

Inorg Chem 2021 Aug 23;60(16):11838-11851. Epub 2021 Jul 23.

Univ Rennes CNRS, , ISCR-UMR 6226 ScanMat-UMS 2001, 35000 Rennes, France.

The synthesis and photophysical and chiroptical properties of novel aza[]helicenes (-, ,, = 4-7) substituted with one or two 2-pyridyl groups are described. The preparation was performed via an adapted Mallory reaction using aromatic imines as precursors. The obtained novel class of helical 2,2'-bipyridine ligands was then coordinated to Ru(bipy) units, thus affording the first diastereomerically and enantiomerically pure [RuL(bipy)] (,, L = ,) or [RuL'(bipy)] (, L' = ) complexes. The topology and stereochemistry of these novel metal-based helical architectures were studied in detail, notably using X-ray crystallography. Interestingly, the coordination to ruthenium(II) enabled the preparation of fused multihelical systems incorporating aza- and ruthena-helicenes within the same scaffold. The photophysical, chiroptical, and redox properties of these complexes were examined in detail, and efficient redox-triggered chiroptical switching activity was evidenced.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.1c01379DOI Listing
August 2021

Indolizy Carbene Ligand. Evaluation of Electronic Properties and Applications in Asymmetric Gold(I) Catalysis.

Angew Chem Int Ed Engl 2021 Sep 29;60(36):19879-19888. Epub 2021 Jul 29.

Institut Parisien de Chimie Moléculaire, Sorbonne Université, CNRS, 4 Place Jussieu, CC 229, 75252, Paris Cedex 05, France.

We report herein a new family of carbene ligands based on an indolizine-ylidene (Indolizy) moiety. The corresponding gold(I) complexes are easily obtained from the gold(I)-promoted cyclization of allenylpyridine precursors. Evaluation of the electronic properties by experimental methods and also by DFT calculations confirms strong σ-donating and π-accepting properties of these ligands. Cationization of the gold(I) complexes generates catalytic species that trigger diverse reactions of (poly)unsaturated precursors. When armed with a methylene phosphine oxide moiety on the stereogenic center adjacent to the nitrogen atom, the corresponding bifunctional carbene ligands give rise to highly enantioselective heterocyclizations. DFT calculations brought some rationalization and highlighted the critical roles played by the phosphine oxide group and the tosylate anion in the asymmetric cyclization of γ-allenols.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202106142DOI Listing
September 2021

A curved host and second guest cooperatively inhibit the dynamic motion of corannulene.

Nat Commun 2021 07 2;12(1):4079. Epub 2021 Jul 2.

Department of Chemistry, University of Cambridge, Cambridge, UK.

Biomolecular systems show how host-guest binding can induce changes in molecular behavior, which in turn impact the functions of the system. Here we report an artificial host-guest system where dynamic adaptation during guest binding alters both host conformation and guest dynamics. The self-assembled cage host employed here possesses concave walls and a chirotopic cavity. Complementarity between the curved surfaces of fullerenes and the inner surface of the host cavity leads the host to reconfigure stereochemically in order to bind these guests optimally. The curved molecule corannulene undergoes rapid bowl-to-bowl inversion at room temperature. Its inversion barrier is increased upon binding, however, and increased further upon formation of a ternary complex, where corannulene and a cycloalkane are both bound together. The chiral nature of the host also leads to clear differences in the NMR spectra of ternary complexes involving corannulene and one or the other enantiomer of a chiral guest, which enables the determination of enantiomeric excess by NMR.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-021-24344-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8253762PMC
July 2021

Enantioselective synthesis of chiral porphyrin macrocyclic hosts and kinetic enantiorecognition of viologen guests.

Chem Sci 2021 Jan 13;12(5):1661-1667. Epub 2021 Jan 13.

Institute for Molecules and Materials, Radboud University Heyendaalseweg 135 6525 AJ Nijmegen The Netherlands

The construction of macromolecular hosts that are able to thread chiral guests in a stereoselective fashion is a big challenge. We herein describe the asymmetric synthesis of two enantiomeric -symmetric porphyrin macrocyclic hosts that thread and bind different viologen guests. Time-resolved fluorescence studies show that these hosts display a factor 3 kinetic preference (ΔΔ = 3 kJ mol) for threading onto the different enantiomers of a viologen guest appended with bulky chiral 1-phenylethoxy termini. A smaller kinetic selectivity (ΔΔ = 1 kJ mol) is observed for viologens equipped with small chiral -butoxy termini. Kinetic selectivity is absent when the -symmetric hosts are threaded onto chiral viologens appended with chiral tails in which the chiral moieties are located in the centers of the chains, rather than at the chain termini. The reason is that the termini of the latter guests, which engage in the initial stages of the threading process (entron effect), cannot discriminate because they are achiral, in contrast to the chiral termini of the former guests. Finally, our experiments show that the threading and de-threading rates are balanced in such a way that the observed binding constants are highly similar for all the investigated host-guest complexes, there is no thermodynamic selectivity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0sc05233gDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179042PMC
January 2021

Achieving high circularly polarized luminescence with push-pull helicenic systems: from rationalized design to top-emission CP-OLED applications.

Chem Sci 2021 Mar 2;12(15):5522-5533. Epub 2021 Mar 2.

Univ Rennes, CNRS, ISCR-UMR 6226, ScanMAT-UMS 2001 F-35000 Rennes France

While the development of chiral molecules displaying circularly polarized luminescence (CPL) has received considerable attention, the corresponding CPL intensity, hardly exceeds 10 at the molecular level owing to the difficulty in optimizing the key parameters governing such a luminescence process. To address this challenge, we report here the synthesis and chiroptical properties of a new family of π-helical push-pull systems based on carbo[6]helicene, where the latter acts as either a chiral electron acceptor or a donor unit. This comprehensive experimental and theoretical investigation shows that the magnitude and relative orientation of the electric ( ) and magnetic (μ ) dipole transition moments can be tuned efficiently with regard to the molecular chiroptical properties, which results in high values, up to 3-4 × 10. Our investigations revealed that the optimized mutual orientation of the electric and magnetic dipoles in the excited state is a crucial parameter to achieve intense helicene-mediated exciton coupling, which is a major contributor to the obtained strong CPL. Finally, top-emission CP-OLEDs were fabricated through vapor deposition, which afforded a promising of around 8 × 10. These results bring about further molecular design guidelines to reach high CPL intensity and offer new insights into the development of innovative CP-OLED architectures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0sc06895kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179576PMC
March 2021

Magnetic Resonance Imaging of Protease-Mediated Lung Tissue Inflammation and Injury.

ACS Omega 2021 Jun 28;6(23):15012-15016. Epub 2021 May 28.

Univ. Bordeaux, CNRS, CRMSB UMR 5536, F-33000 Bordeaux, France.

Pulmonary inflammation usually involves strong neutrophil recruitment with a marked release of proteases such as neutrophil elastase (NE). Noninvasive in vivo assessment of unregulated elastase activity in the lungs would provide a valuable diagnostic tool. Here, it is proposed to use Overhauser-enhanced magnetic resonance imaging (OMRI) in mice where inflammation was induced by the instillation of lipopolysaccharide (LPS). OMRI contrast in the lungs was generated by a dedicated NE free radical substrate. The free radical decayed more rapidly in LPS-treated mouse lungs than in control mice, indicating the occurrence of increased proteolysis under inflammation. Preclinical detection of abnormal proteolysis opens the way for new diagnosis modality and antiprotease testing in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsomega.1c01150DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8209802PMC
June 2021

Are the Physical Properties of [email protected] Complexes Easily Predictable? The Case of - and -Tris-aza-Cryptophanes.

J Org Chem 2021 Jun 25;86(11):7648-7658. Epub 2021 May 25.

Laboratoire de Chimie de l'ENS Lyon, (UMR 5182 CNRS-ENS-Université), Université Claude Bernard Lyon 1, F69342 Lyon, France.

We report the synthesis and optical resolution of -symmetrical tris-aza-cryptophanes - and -, as well as the study of their interaction with xenon hyperpolarized Xe NMR. These molecular cages are close structural analogues of the two well-known cryptophane-A (; chiral) and cryptophane-B (; achiral) diastereomers since these new compounds differ only by the presence of three nitrogen atoms grafted onto the same cyclotribenzylene unit. The assignment of their relative (syn vs anti) and absolute configurations was made possible, thanks to the combined use of quantum calculations at the density functional theory level and vibrational circular dichroism spectroscopy. More importantly, our results show that despite the large structural similarities with cryptophane-A () and -B (), these two new compounds show a very different behavior in the presence of xenon in organic solutions. These results demonstrate that prediction of the physical properties of the [email protected] complexes, only based on structural parameters, remains extremely difficult.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.joc.1c00701DOI Listing
June 2021

Multigram-scale HPLC enantioseparation as a rescue pathway for circumventing racemization problem during enantioselective synthesis of ethyl 3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate.

Chirality 2021 07 27;33(7):324-336. Epub 2021 Apr 27.

LCPM, CNRS, Université de Lorraine, F-54000 Nancy, France.

Racemic ethyl 3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate is a key synthon for the design of promising therapeutic drugs. It is mainly synthesized from racemic ethyl 2,3-dibromopropionate and 2-aminophenol in presence of K CO in refluxed acetone. Unfortunately, synthesis of (R)- and (S)-enantiomers using the enantioselective version of this reaction, which should normally be performed with a double S 2 mechanism, is unsuitable due to a racemization process involving the dehydrobromination of enantiopure ethyl 2,3-dibromopropionate into ethyl 2-bromoacrylate. For the first time, the enantioselective version is studied (ee ≈ 55-66%), and the percentage of racemization process has estimated to around 34-46% after determination of the optimal experimental conditions for analytical HPLC enantioseparation of racemate. The influence of the experimental and purification conditions on the racemization rate is also studied. The results indicate that racemization occurs faster at the beginning of the reaction but the initiation of the double S 2 process takes place more faster to limit the racemization rate. The study of the influence of experimental conditions (reaction times, temperature, solvent or type of base, etc.) on the degree of racemization of the (R)- enantiomer is performed and shows that despite changes in the experimental conditions, the synthesis of the (R)- enantiomer is always accompanied by a racemization rate which is difficult in reducing. In parallel, (R)- and (S)-enantiomers are obtained in high enantiopurity (ee > 99.5%) by preparative HPLC enantioseparation of racemate on multigram scale and characterized by optical rotation measurements, ECD and UV spectra.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chir.23313DOI Listing
July 2021

On the Enantioselective Phosphoric-Acid-Catalyzed Hantzsch Synthesis of Polyhydroquinolines.

Org Lett 2021 05 27;23(9):3394-3398. Epub 2021 Apr 27.

Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille 13397, France.

A reinvestigation of a chiral phosphoric-acid-catalyzed four-component Hantzsch enantioselective synthesis of polyhydroquinolines reported in 2009 is presented. In our hands, when the reaction was performed with fidelity to the original report using a chiral enantiopure phosphoric acid catalyst, no enantioselectivity was observed. Unlike in the original report, enantioselectivity results are backed by baseline separation of the enantiomers by HPLC analyses on chiral stationary phase with UV and chiroptical detection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.orglett.1c00866DOI Listing
May 2021

Synthesis and Properties of Partially Saturated Fluorenyl-Derived [n]Helicenes Featuring an Overcrowded Alkene.

Chemistry 2021 May 30;27(28):7722-7730. Epub 2021 Apr 30.

LCC-CNRS, Université de Toulouse, CNRS, 31077, Toulouse, France.

The straightforward, multigram-scale synthesis of the partially saturated H -fluoreno[n]helicenes (n=5 or 7) featuring a central, overcrowded alkene is described. The key cyclization step was based on an intramolecular McMurry reaction from the corresponding 1,5-diketones. Chiral stationary phase HPLC analysis and isomer separation indicate that each helicenic compound is constituted of three diastereoisomers at room temperature, i. e. the configurationally stable (R,R,P)/(S,S,M) pair of enantiomers and an apparently achiral compound resulting from the rapid interconversion between the (R,S,P) and (S,R,M) enantiomers. The partially saturated H -fluoreno[n]helicenes are oxidatively aromatized to give an efficient access to the corresponding fluoreno[n]helicenes. The chiroptical properties (vibrational and electronic circular dichroism) of the chiral, enantiopure compounds have been measured and analyzed by quantum-chemical calculations, confirming their helicoidal nature.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.202100150DOI Listing
May 2021

Circularly Polarized Fluorescent Helicene-Boranils: Synthesis, Photophysical and Chiroptical Properties.

Chemistry 2021 May 22;27(29):7959-7967. Epub 2021 Apr 22.

Univ Rennes, CNRS, ISCR-UMR 6226, Université de Rennes 1, Campus de Beaulieu, 35042, Rennes Cedex, France.

Mono- and di-boranil-substituted helicenes were prepared by BF -borylation of the corresponding anils, readily synthesized by condensation of 2-amino- and 2,15-diamino-helicenes with 4-(diethylamino)salicylaldehyde. After enantiomeric resolution using HPLC, their chiroptical properties including circularly polarized fluorescence in solution and in PMMA films were investigated and rationalized with the help of NMR, X-ray and quantum-chemical calculations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.202100356DOI Listing
May 2021

Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages.

European J Org Chem 2021 Jan 5;2021(4):607-617. Epub 2021 Jan 5.

Radboud University Institute for Molecules and Materials Heyendaalseweg 135 6525 AJ Nijmegen The Netherlands.

Chiral zirconium(IV) double cage sandwich complex has been synthesized in one step from porphyrin cage was obtained as a racemate, which was resolved by HPLC and the enantiomers were isolated in >99.5 % ee. Their absolute configurations were assigned on the basis of X-ray crystallography and circular dichroism spectroscopy. Vibrational circular dichroism (VCD) experiments on the enantiomers of revealed that the chirality around the zirconium center is propagated throughout the whole cage structure. The axial conformational chirality of the double cage complex displayed a VCD fingerprint similar to the one observed previously for a related chiral cage compound with planar and point chirality. shows fluorescence, which is quenched when viologen guests bind in its cavities. The binding of viologen and dihydroxybenzene derivatives in the two cavities of occurs with negative allostery, the cooperativity factors α (=4 K/K) being as low as 0.0076 for the binding of -dimethylviologen. These allosteric effects are attributed to a pinching of the second cavity as a result of guest binding in the first cavity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ejoc.202001392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898692PMC
January 2021

Two-Photon Absorbing AIEgens: Influence of Stereoconfiguration on Their Crystallinity and Spectroscopic Properties and Applications in Bioimaging.

ACS Appl Mater Interfaces 2020 Dec 20;12(49):55157-55168. Epub 2020 Nov 20.

Univ. Lyon, ENS Lyon, CNRS, Université Lyon 1, Laboratoire de Chimie, UMR 5182, 46 Allée d'Italie, 69364 Lyon, France.

This paper aims at designing chromophores with efficient aggregation-induced emission (AIE) properties for two-photon fluorescence microscopy (2PFM), which is one of the best-suited types of microscopy for the imaging of living organisms or thick biological tissues. Tetraphenylethylene (TPE) derivatives are common building blocks in the design of chromophores with efficient AIE properties. Therefore, in this study, extended TPE AIEgens specifically optimized for two-photon absorption (2PA) are synthesized and the resulting (/) isomers are separated using chromatography on chiral supports. Comparative characterization of the AIE properties is performed on the pure () and () isomers and the mixture, allowing us, in combination with powder X-ray diffraction and solid-state NMR, to document a profound impact of crystallinity on solid-state fluorescence properties. In particular, we show that stereopure AIEgens form aggregates of superior crystallinity, which in turn exhibit a higher fluorescence quantum yield compared to diastereoisomers mixtures. Preparation of stereopure organic nanoparticles affords very bright fluorescent contrast agents, which are then used for cellular and intravital two-photon microscopy on human breast cancer cells and on zebrafish embryos.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.0c15810DOI Listing
December 2020

Axially and Helically Chiral Cationic Radical Bicarbazoles: SOMO-HOMO Level Inversion and Chirality Impact on the Stability of Mono- and Diradical Cations.

J Am Chem Soc 2020 Nov 17. Epub 2020 Nov 17.

Université Rennes, CNRS, ISCR-UMR 6226, Rennes F-35000, France.

We report persistent chiral organic mono- and diradical cations based on bicarbazole molecular design with an unprecedented stability dependence on the type of chirality, namely, axial versus helical. An unusual chemical stability was observed for sterically unprotected axial bicarbazole radical in comparison with monocarbazole and helical bicarbazole ones. Such results were experimentally and theoretically investigated, revealing an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest (doubly) occupied molecular orbital (HOMO) in both axial and helical bicarbazole monoradicals along with a subtle difference of electronic coupling between the two carbazole units, which is modulated by their relative dihedral angle and related to the type of chirality. Such findings allowed us to explore in depth the SOMO-HOMO inversion (SHI) in chiral radical molecular systems and provide new insights regarding its impact on the stability of organic radicals. Finally, these specific electronic properties allowed us to prepare a persistent, intrinsically chiral, diradical which notably displayed near-infrared electronic circular dichroism responses up to 1100 nm and almost degenerate singlet-triplet ground states with weak antiferromagnetic interactions evaluated by magnetometry experiments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.0c08948DOI Listing
November 2020

Optically Pure -Symmetric Cyclic(alkyl)(amino)carbene Ruthenium Complexes for Asymmetric Olefin Metathesis.

J Am Chem Soc 2020 11 13;142(47):19895-19901. Epub 2020 Nov 13.

Université de Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, ISCR UMR 6226, F-35000Rennes, France.

An expedient access to the first optically pure ruthenium complexes containing -symmetric cyclic (alkyl)(amino)carbene ligands is reported. They demonstrate excellent catalytic performances in asymmetric olefin metathesis with high enantioselectivities (up to 92% ee). Preliminary mechanistic insights provided by density functional theory models highlight the origin of the enantioselectivity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.0c10705DOI Listing
November 2020

Dissecting the Role of the Sergeants in Supramolecular Helical Catalysts: From Chain Capping to Intercalation.

Angew Chem Int Ed Engl 2021 Feb 21;60(8):4183-4191. Epub 2020 Dec 21.

Sorbonne Université, CNRS, Institut Parisien de Chimie Moléculaire, Equipe Chimie des Polymères, 4 Place Jussieu, 75005, Paris, France.

Controlling the properties of supramolecular assemblies requires unveiling the specific interactions between their components. In the present work, the catalytic properties and structure of co-assemblies composed of a benzene-1,3,5-tricarboxamide (BTA) ligand coordinated to copper (the soldier) and seven enantiopure BTAs (the sergeants) have been determined. Whatever the sergeant, the enantioselectivity of the reaction is directly proportional to the optical purity of the supramolecular helices. More strikingly, the role played by the sergeant in the co-assembly process differs significantly: from almost pure intercalator (when it is incorporated in the stacks of the soldier and generates long homochiral helices) to pure chain capper (when it leads to the formation of partly helically biased and short assemblies). The former situation leads to optimal enantioselectivity for the catalytic system under study (58 % ee) while the latter situation leads to very low selectivity (8 % ee). The successful rationalization of this high and unexpected difference is crucial for the development of more efficient catalysts and more elaborate supramolecular systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202012457DOI Listing
February 2021

Molecular motor-functionalized porphyrin macrocycles.

Nat Commun 2020 10 20;11(1):5291. Epub 2020 Oct 20.

Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.

Molecular motors and switches change conformation under the influence of an external stimulus, e.g. light. They can be incorporated into functional systems, allowing the construction of adaptive materials and switchable catalysts. Here, we present two molecular motor-functionalized porphyrin macrocycles for future photo-switchable catalysis. They display helical, planar and point chirality, and are diastereomers, which differ in the relative orientation of the motor and macrocyclic components. Fluorescence, UV-vis, and H NMR experiments reveal that the motor-functionalized macrocycles can bind and thread different variants of viologen guests, including a one-side blocked polymeric one of 30 repeat units. The latter feature indicates that the motor systems can find the open end of a polymer chain, thread on it, and move along the chain to eventually bind at the viologen trap, opening possibilities for catalytic writing on single polymer chains via chemical routes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-19123-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7576194PMC
October 2020

Dinuclear Rhenium Complexes with a Bridging Helicene-bis-bipyridine Ligand: Synthesis, Structure, and Photophysical and Chiroptical Properties.

Chempluschem 2020 Nov 23;85(11):2446-2454. Epub 2020 Sep 23.

Univ Rennes, CNRS, ISCR - UMR 6226, 35000, Rennes, France.

By attaching pyridine groups to a diaza[6]helicene, a helical, bis-ditopic, bis-N N-coordinating ligand can be accessed. Dinuclear rhenium complexes featuring this bridging ligand, of the form [{Re(CO) Cl} (N N-N N)], have been prepared and resolved to give enantiopure complexes. These complexes are phosphorescent in solution at room temperature under one- and two-photon excitation. Their experimental chiroptical properties (optical rotation, electronic circular dichroism and circularly polarized emission) have been measured. They show, for instance, emission dissymmetry factors of c.a. ±3x10 . Quantum-chemical calculations indicate the importance of stereochemistry on the optical activity, pointing towards further design improvements in such types of complexes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cplu.202000559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7745256PMC
November 2020

Absolute configuration and host-guest binding of chiral porphyrin-cages by a combined chiroptical and theoretical approach.

Nat Commun 2020 09 22;11(1):4776. Epub 2020 Sep 22.

Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.

Porphyrin cage-compounds are used as biomimetic models and substrate-selective catalysts in supramolecular chemistry. In this work we present the resolution of planar-chiral porphyrin cages and the determination of their absolute configuration by vibrational circular dichroism in combination with density functional theory calculations. The chiral porphyrin-cages form complexes with achiral and chiral viologen-guests and upon binding one of the axial enantiomorphs of the guest is bound selectively, as is indicated by induced-electronic-dichroism-spectra in combination with calculations. This host-guest binding also leads to unusual enhanced vibrational circular dichroism, which is the result of a combination of phenomena, such as rigidification of the host and guest structures, charge transfer, and coupling of specific vibration modes of the host and guest. The results offer insights in how the porphyrin cage-compounds may be used to construct a future molecular Turing machine that can write chiral information onto polymer chains.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-18596-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7508876PMC
September 2020

Simultaneous Control of Central and Helical Chiralities: Expedient Helicoselective Synthesis of Dioxa[6]helicenes.

J Am Chem Soc 2020 09 8;142(38):16199-16204. Epub 2020 Sep 8.

Aix Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille, France.

An expedient synthesis of a new family of configurationally stable dioxa[6]helicenes was established using a sequential helicoselective organocatalyzed heteroannulation/eliminative aromatization via enantioenriched fused 2-nitro dihydrofurans featuring both central and helical chiralities. Starting from simple achiral precursors, a broad range of these previously unknown chiral heterocyclic scaffolds were obtained with good efficiency, and their aromatization proceeded with very high enantiopurity retention in most cases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.0c07995DOI Listing
September 2020

Enantiopure ethyl 2,3-dibromopropionate: Enantioselective synthesis vs preparative HPLC enantioseparation of racemate on multigram scale.

Chirality 2020 08 22;32(8):1045-1052. Epub 2020 Jun 22.

Université de Lorraine, CNRS, LCPM, Nancy, F-54000, France.

Racemic ethyl 2,3-dibromopropionate, commercially available at low price, is a key intermediate used in the synthesis of several heterocycle fragments, which are present in many biologically active compounds. Surprisingly, the enantiomers are not commercially available and have never been described in the literature. In this work, we undertook two different strategies to obtain these enantiomers, which are enantioselective synthesis and preparative HPLC enantioseparation of commercially available racemate on multigram scale. The first strategy has proved inadequate because racemization occurred during the synthesis (ee ≈ 9-50%). Conversely, the second strategy produced a very good enantioseparation of commercially available racemate (ee > 99.5% for both enantiomers) on multigram scale.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chir.23260DOI Listing
August 2020

Chiral Diketopyrrolopyrrole-Helicene Polymer With Efficient Red Circularly Polarized Luminescence.

Front Chem 2020 9;8:237. Epub 2020 Apr 9.

Univ Rennes, CNRS, Institut des Sciences Chimiques de Rennes, ISCR-UMR 6226, Rennes, France.

Chiral diketopyrrolopyrrole (DPP)-helicene polymers were synthesized to develop efficient red circularly polarized (CP) light emitters. These original chiral dyes display intense electronic circular dichroism (ECD) and CP luminescence (CPL) in the far-red spectral region owing to the presence of excitonic coupling between achiral DPPs within the chiral environment of the polymeric structure. This work affords an interesting example illustrating the potential of π-conjugated helical polymers for chiral optoelectronic applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fchem.2020.00237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7160364PMC
April 2020
-->