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A series of highly emissive inert and chiral CrIII complexes displaying dual circularly polarized luminescence (CPL) within the NIR region have been prepared and characterized. The helical [Cr(dqpR)2 ]3+ (dqp=2,6-di(quinolin-8-yl)pyridine; R=OCH3 , Br or C≡CH) complexes were synthesized as racemic mixtures and resolved into their respective PP and MM enantiomers by chiral stationary phase HPLC. The corresponding enantiomers show large glum ≈0.2 and high quantum yield of up to 17 %, which afford important CPL brightness of up to 170 m-1 cm-1 , a key point for applications as chiral luminescent probes. Moreover, the long-lived CP-NIR emission provided by these chromophores (ms range) in aqueous solution opens the way toward the quantification of chiral targets in biological systems with time-gated detection. Thus, such chiral chromophores based on earth abundant and inert 3d metals open new perspectives in the field of CPL and represent an alternative to precious 4d, 5d and to labile 4f metal-based complexes.

International audience; We demonstrate the possibility to detect selectively the two enantiomers of a model [Ru(bpy) 3 ] 2+-based dye by circularly polarized-electrochemiluminescence (CP-ECL). This new nature of the ECL emission combines the chiral information intrinsic of CPL methods with an electrogeneration of the excited state. Thus, it opens the possibility to perform ECL-based bioassays or microscopy with efficient chiral dyes.

Controlling electrochemiluminescence (ECL) color(s) is crucial for many applications ranging from multiplexed bioassays to ECL microscopy. This can only be achieved through the fundamental understanding of high-energy electron-transfer processes in complex and competitive reaction schemes. Recently, this field has generated huge interest, but the effective implementation of multicolor ECL is constrained by the limited number of ECL-active organometallic dyes. Herein, the first self-enhanced organic ECL dye, a chiral red-emitting cationic diaza [4]helicene connected to a dimethylamino moiety by a short linker, is reported. This molecular system integrates bifunctional ECL features (i.e. luminophore and coreactant) and each function may be operated either separately or simultaneously. This unique level of control is enabled by integrating but decoupling both molecular functions in a single molecule. Through this dual molecular reactivity, concomitant multicolor ECL emission from red to blue with tunable intensity is readily obtained in aqueous media. This is done through competitive electron-transfer processes between the helicene and a ruthenium or iridium dye. The reported approach provides a general methodology to extend to other coreactant/luminophore systems, opening enticing perspectives for spectrally distinct detection of several analytes, and original analytical and imaging strategies., Controlling electrochemiluminescence (ECL) color(s) is crucial for many applications ranging from multiplexed bioassays to ECL microscopy.

International audience; Synthesis, electronic and structural properties of a chiral NHC bearing a N-bonded cationic [4]helicene moiety are reported. This ligand is used to construct Au(I), Au(III) and Rh(I) complexes exhibiting far-red (chir)optical properties regardless of the metal.

International audience; In one pot, tertiary alkyl amines are oxidized to enamines by cationic dioxa[6]helicene, which further reacts as electrophile and oxidant to form mono or bis donor-π-acceptor coupling products. This original and convergent synthetic approach provides a strong extension of conjugation yielding chromophores that absorb intensively in far-red or NIR domains (λmax up to 791 nm) and fluoresce in the NIR as well (λmax up to 887 nm). Intense ECD properties around 790 nm with a |Δϵ| value up to 60 M-1 cm-1 are observed.

Singlet fission (SF), i.e., the splitting of a high-energy exciton into two lower-energy triplet excitons, has the potential to increase the efficiency for harvesting spectrally broad light. The path from the photopopulated singlet state to free triplets is complicated by competing processes that decrease the overall SF efficiency. A detailed understanding of the whole cascade and the nature of the photoexcited singlet state is still a major challenge. Here, we introduce a pentacene dimer with a flexible crown ether spacer enabling a control of the interchromophore coupling upon solvent-induced self-aggregation as well as cation binding. The systematic change of solvent polarity and viscosity and excitation wavelength, as well as the available conformational phase space, allows us to draw a coherent picture of the whole SF cascade from the femtosecond to microsecond time scales. High coupling leads to ultrafast SF (

International audience; Chiral hemicyanine fluorophores are afforded in three steps only from Tröger bases via α-imino carbene additions, an original aminal deprotection and Cu(II)-mediated oxidation. The stable benzodiazepinoindolium salts are readily isolated and present (chir)optical properties that can be fine-tuned by late-stage cross-coupling functionalization. The hemicyanine character of dyes was rationalized using first principles.

International audience; A straightforward approach to the synthesis of two different series of cationic [5]helicenes has been achieved including, in dioxa series, the possibility to introduce aromatic functional groups at the periphery of the helical structure. While photophysical study highlights that the introduction of aryl substituents at position 23 of the helical moieties has a negligible impact on the optical properties, styryl substituents allow a welcoming extension of the conjugation pathways. Finally, a red shift of the optical properties was evidenced upon introduction of nitrogen atoms in the helicene scaffold, leading to particularly good fluorescence efficiencies in the red domain for a helicenic dye. Detailed information on racemization kinetics was collected for the most stable species upon direct high-performance liquid chromatography (HPLC) resolution or, when configurational lability was too high, through VT-HPLC analysis on the chiral stationary phase (ΔG‡ values ranging from 85.0 to 137.1 kJ·mol–1 and above).

International audience; A series of w ater-soluble helicene dyes generating intense electrochemiluminescence (ECL) signal in physiological conditions is reported. Those species were prepared using diaza [4] and [6]helicenes as structural cores modified with sulfonate groups in various positions. Such groups improve their water solubility and induce a red-shifted emission. Efficient ECL up to the near-infrared is achieved in water, demonstrating a viable strategy for the design of new near-infrared ECL dyes for bioassays and microscopy.

International audience; Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectroscopy. These enantiopure encaged superbases turned out to be efficient chiral derivatizing agents for chiral azides, underlining that the chirality of the cycloveratrylene (CTV) macrocycle induces different magnetic and chemical environments around the phosphazide functions.

International audience; Cationic [Ru(η 5-C5H5)(CH3CN)3] + complex, tris(acetonitrile)(cyclopentadienyl)ruthenium(II), gives rise to a very rich organometallic chemistry. Combined with diimine ligands, and 1,10-phenanthroline in particular, this system efficiently catalyzes diazo decomposition processes to generate metal-carbenes which undergo a series of original transformations in the presence of Lewis basic substrates. Herein, syntheses and characterizations of [CpRu(Phen)(L)] complexes with (large) lipophilic non-coordinating (PF6 − and BArF −) and coordinating N-TRISPHAT − anions are reported. Complex [CpRu(η 6-naphthalene)][BArF] [1][BArF] is readily accessible, in high yield, by direct counterion exchange between [1][PF6] and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF) salts. Ligand exchange of [1][BArF] in acetonitrile generated stable [Ru(η 5-C5H5)(CH3CN)3][BArF] [2][BArF] complex in high yield. Then, the desired [CpRu(Phen)(CH3CN)] [3] complexes were obtained from either the [1] or [2] complex in the presence of the 1,10-phenanthroline as ligand. For characterization and comparison purposes, the anionic hemilabile ligand TRISPHAT-N (TTN) was introduced on the ruthenium center, from the complex [3][PF6], to quantitatively generate the desired complex [CpRu(Phen)(TTN)] [4] by displacement of the remaining acetonitrile ligand and of the PF6 − anion. Solid state structures of complexes [1][BArF], [2][BArF], [3][BArF], [3][PF6] and [4] were determined by X-ray diffraction studies and are discussed herein.

Following a late-stage functionalization strategy, a series of heteroditopic cryptand receptors were prepared in three steps only from 1,4-dioxane. As evidenced by 1 H NMR spectroscopic and solid state analyses, these polyamide-crown ether conjugates present general ion pair binding capacity towards salts of monovalent cations and linear triatomic anions.

Interaction of electrons with chiral matter gives rise to interesting phenomena such as the chirality-induced spin selectivity. The interdependence of reflectivity of spin-polarized low energy electrons and the absolute handedness of chiral molecules is investigated. First, the growth of homochiral films of helical aromatic hydrocarbons, so-called helicenes, on a Cu(100) surface is studied by means of low energy electron microscopy and scanning tunneling microscopy in ultrahigh vacuum. As soon as the coverage exceeds one monolayer, double-layer nucleation and growth is favored such that depletion in the first layer occurs. Spatially resolved work function measurements show that second-layer patches have a lower work function than first-layer areas. Reflectivity spectra of spin-polarized electrons do not show any asymmetry between homochiral films of the enantiomers. Laterally resolved work function measurements do not confirm work function differences such as those reported earlier for photoelectron studies of chiral peptide films on ferromagnetic substrates.

We describe a new family of molecular ion‐to‐electron redox probes based on cationic diaza, azaoxa, and dioxa [6]helicenes and their derivatives. Their unique structure combines, in a single framework, two privileged families of molecules – helicenes and triaryl methyl carbenium moieties. These cationic [6]helicenes exhibit reversible and reproducible oxidation/reduction behavior and facilitate the ion transfer into thin layer sensing films composed of bis(2‐ethylhexyl)sebacate (DOS), polyurethane (PU), sodium tetrakis 3.5‐bis(trifluoromethyl)phenyl borate, sodium ionophore X and diaza+(C8)2Br2 for cation transfer. Cyclic voltammetry is used to interrogate the thin films. The cationic response can be tuned by adjusting the membrane loading. Addition of lipophilic cation exchanger into the membrane film results in transfer waves of Gaussian shape for cations. A peak separation of 60 mV and peak width of 110 mV are near the theoretical values for a surface confined process. While Nernstian shifts of the peak potentials with analyte concentration is obtained for membranes based on cationic [6]helicenes and doped with sodium‐selective ionophore X, this ionophore was found to promote a gradual loss of redox active species from the ionophore‐based membranes into the sample solution.

1,4-Dioxepines result from the decomposition of α-diazo-β-keto esters in the presence of oxetanes using the catalytic combination of the (cyclopentadienyl)ruthenium complex [CpRu(CH3CN)3][BArF] and 1,10-phenanthroline. The regioselective [4+3] insertions follow an SN1-like mechanism and occur yet enantiospecifically (es 74%). The retention of configuration was ascertained by vibrational circular dichroism (VCD) and solid state analyses. Furans, products of [4+1] insertions, are only observed as traces in the above protocol. To promote their formation under CpRu catalysis, it is necessary to use a two-step process with γ-halogenated alcohols as substrates.

Cationic helicenes are ortho-fused polyaromatics which exhibit well-defined and stable helical conformations with original absorption and emission properties in the red to near-infrared spectral ranges. Herein, a selection of cationic [4] and [6]helicenes are studied for their electrochemical, fluorescence, and electrochemiluminescence (ECL) properties in acetonitrile solutions. Their photophysical and redox responses are drastically tuned by the introduction of auxochrome substituents at their periphery or the interconversion of oxygen and nitrogen atoms within the helical core. All diaza helicenes exhibit a reversible reduction process, whereas in the presence of oxygen instead of nitrogen atoms in the helical core, irreversible oxidations and a decrease of ECL intensity are observed. ECL emission was successfully produced with two sacrificial coreactants (benzoyl peroxide and tri-n-propylamine, TPrA). [4]Helicene DMQA+, [6]helicene DIAZA(Pr/Br)+, and DIAZA(Hex/Br)+ exhibit similar ECL emission wavelength in the near-infrared region and generate very intense ECL signals. Their ECL efficiencies are up to 2.6 times higher than that of the reference compound [Ru(bpy)3]2+ when using TPrA as coreactant. A thermodynamic map gathering both oxidation and reduction potentials and fluorescence data is proposed for the prediction of energy sufficiency needed in both coreactant ECL systems. Such a systematic overview based on the photophysical and electrochemical properties may guide the conception and synthesis of new chromophores with a strong ECL proficiency.

Using N-sulfonyl triazoles as substrates, compounds as diverse as 2-imino tetrahydrofurans, 13- and 15-membered ring aza-macrocycles can be prepared selectively via formal [1 + 4], [5 + 4 + 4] and [3 + 4 + 4 + 4] condensations of α-imino carbenes and oxetanes under Rh(ii)-catalysis or thermal activation. Spirocyclic N-heterocycles are also accessible by means of Buchwald-Hartwig and Pictet-Spengler cyclizations. By reaction control, substrate selection or further derivatization, a large variety of chemical structures is thus achievable. Finally, using triazoles reacting under thermal activation, interesting mechanistic insight was obtained.

International audience; The physicochemical properties of cationic dioxa (1), azaoxa (2), and diaza (3) [6]helicenes demonstrate a much higher chemical stability of the diaza adduct 3 (pKR+ =20.4, Ered1/2 =-0.72 V) compared to its azaoxa 2 (pKR+ =15.2, Ered1/2 =-0.45 V) and dioxa 1 (pKR+ =8.8, Ered1/2 =-0.12 V) analogues. The fluorescence of these cationic chromophores is established, and ranges from the orange to the far-red regions. From 1 to 3, a bathochromic shift of the lowest energy transitions (up to 614 nm in acetonitrile) and an enhancement of the fluorescence quantum yields and lifetimes (up to 31 % and 9.8 ns, respectively, at 658 nm) are observed. The triplet quantum yields and circularly polarized luminescence are also reported. Finally, fine tuning of the optical properties of the diaza [6]helicene core is achieved through selective and orthogonal post-functionalization reactions (12 examples, compounds 4-15). The electronic absorption is modulated from the orange to the far-red spectral range (560-731 nm), and fluorescence is observed from 591 to 755 nm with enhanced quantum efficiency up to 70 % (619 nm). The influence of the peripheral auxochrome substituents is rationalized by first-principles calculations.

The first observation of circular polarization of electrochemiluminescence (ECL) from a purely organic derivative is reported. A bispyrene scaffold mounted on a constrained polyether macrocycle displaying intense excimer fluorescence and highly circularly-polarized (CP) photoluminescence has been selected for this purpose. The compound displays an ECL dissymmetry factor of about |8×10-3 |, which is in good agreement with the corresponding photoluminescence value. This observation is the first step towards the molecular engineering of tailored dyes that can act as both ECL and CP-ECL reporters for (bio)analysis by bringing a new level of information when dealing with chiral environments. Additionally, it provides an extra dimension to the ECL phenomenon and opens the way to chiral detection and discrimination.

The stereoselective synthesis of chiral macrocycles bearing two aliphatic amide functional groups is reported. After the amidation mediated by TBD, a guanidine derivative, the olefin transposition step is performed with a slight excess of t-BuOK. The products are afforded in moderate to good combined yields (up to 59%) and with an excellent syn diastereoselectivity (dr > 49 : 1). Introducing enantiopure α-branched substituents was possible and it resulted in mixtures of diastereomers, which could be tested as phase-transfer catalysts using the formation of a phenylalanine analog as a test reaction (up to 43% ee). A clear matched–mismatched situation was observed in the two diastereomeric series.

Oxygen atoms of cationic dioxa and azaoxa [6]helicenes can be exchanged by amino groups and these reactions lead to either near racemization (es 3%) or to a remarkable enantiospecificity (es up to 97%). Based on detailed investigations, the chirality transfer of the first transformation can be improved to 61%., Oxygen atoms of cationic dioxa and azaoxa [6]helicenes can be exchanged by amino groups to form azaoxa and diaza [6]helicenes respectively. The mild reaction conditions developed herein allow the construction of libraries of derivatives with sensitive and/or functionalized side chains. Using enantioenriched dioxa or azaoxa helicene precursors, these exchanges lead to either near racemization (es 3%) or to a remarkable enantiospecificity (es up to 97%). This unusual behavior is fully characterized via experimental and computational mechanistic evidence. Based on these investigations, the enantiospecificity of the first transformation can be improved to 57–61%.

Understanding structure–property relationships in multichromophoric molecular architectures is a crucial step in establishing new design principles in organic electronics as well as to fully understand how nature exploits solar energy. Here, we study the excited state dynamics of three bichromophores consisting of two perylene chromophores linked to three different crown-ether backbones, using stationary and ultrafast electronic spectroscopy combined with molecular dynamics simulations. The conformational space available to the bichromophores depends on the structure and geometry of the crown-ether and can be significantly changed upon cation binding, strongly affecting the excited-state dynamics. We show that, depending on the conformational restrictions and the local environment, the nature of the excited state varies greatly, going from an excimer to a symmetry-broken charge separated state. These results can be rationalised in terms of a structure–property relationship that includes the effect of the local environment., Varying the structure of perylene-based dimers allows tuning the excited state from an excimer to a charge-separated state.

Polycyclic indoline‐benzodiazepines are afforded in one step by the reaction of Troger bases with N‐sulfonyl‐1,2,3‐triazoles under Rh(II) catalysis. After α‐imino carbene formation, the process involves a cascade of [1,2]‐Stevens rearrangement, Friedel‐Crafts, Grob fragmentation, and aminal formation reactions. It is highly diastereoselective (d.r. >49:1, four stereocenters incl. two bridgehead N‐atoms). However and in contrast with other reported carbene additions to these moieties, full racemization occurs when enantiopure Troger bases are used as substrates. To pinpoint the origin of this unexpected behavior, a key elemental step of the mechanism was evaluated and tested. Interestingly, it is not only the initial ring‐opening but also the latter reversible Mannich reaction of the imino‐substituted ethano Troger base intermediate that is responsible for the loss of enantiospecificity.

A series of helical tetracenes and pentacenes was synthesized from cationic [6] and [4]helicene precursors. These colorful acenes fluoresce in the far red region. While [4]helicene-based pentacenes exhibit chiroptical properties mainly in the UV region, [6]helicene-derived tetracenes show enhanced ECD in the visible range, in addition to clear CPL responses. This difference is rationalized using first principles., Helical polyaza acenes, made from cationic [4] and [6]helicenes, display bright fluorescence. Only [6]helicene-derived tetracenes show enhanced ECD and CPL responses in the visible range as rationalized from first principles.

N-aryl γ-lactams react intermolecularly with acceptor–acceptor diazo reagents, usually dicarbonyl compounds, in a copper-catalyzed process to yield functionalized pyrrolidines with α-pseudoquaternary centers. As 1,2-acyl or -phosphoryl migration is preferred, single regioisomers are obtained. Furthermore, in the presence of a Lewis acid, subsequent Friedel–Crafts reactions yield tricyclic pyrrolizidines in excellent yields (90–96 %) and diastereoselectivities (up to >20:1).

In the context of [3+6+3+6] macrocyclization reactions, precise kinetics of α-diazo-β-ketoester decomposition were measured by in situ infrared (IR) monitoring. Dirhodium complexes of Ikegami–Hashimoto type—and perchlorinated phthalimido derivatives in particular—performed better than classical achiral complexes. Clear correlations were found between speciation among dirhodium species and catalytic activity. With these results, novel cyclohexyl-derived catalysts were developed, affording good yields of macrocycles (up to 78%), at low catalyst loadings (from 0.01 mol % to 0.001 mol %) and on a large scale (from 1 g to 20 g).

Cationic hetero[6]helicenes 1+, 2+ and 3+ have been recently disclosed. Herein we report on their enantiomeric separation using high-performance liquid chromatography. Separation of the antipodes can be achieved in preparative scale on neutral adducts with Chiralcel OD-I or Chiralpak ID CSP. Selectivity factors of 1.90, 1.67, and 1.96 were obtained for 1-H, 2-H, and 3-H, respectively. Separation can also be performed on the carbenium ions on regular Chiralpak IA CSP using water-containing eluents, thus allowing for enantiomeric purity determinations in aqueous environments. Resolution of neutral and cationic helicenes is also achieved on more recently developed LARIHC columns. The versatility of the cyclofructan phases allows for baseline separations for both cases and their loading capabilities are demonstrated. Finally, the configurational stability of 1+, 2+, and 3+ was measured. For each replacement of an oxygen atom by an amino group, the racemization barrier increases significantly (ΔG‡ = 29.8, 36.3 and >37 kcal mol(-1) for 1+, 2+, and 3+ respectively).

Cationic chiral helicenes fully conjugated systems without stereogenic carbons can filter spins effectively at room temperature a consequence of the chiral induced spin selectivity effect. The chirality dictates the spin of the electrons transferred through the helicene framework and magnetoresistance devices based on these molecules show antisymmetric magnetoresistance versus H plots.

Late endosomes are a major trafficking hub in the cell at the crossroads between endocytosis, autophagy, and degradation in lysosomes. Herein is disclosed the first small molecule allowing their selective imaging and monitoring in the form of a diazaoxatriangulene fluorophore, 1a (hexadecyl side chain). The compound is prepared in three steps from a simple carbenium precursor. In nanospheres, this pH-sensitive (pKa = 7.3), photochemically stable dye fluoresces in the red part of visible light (601 and 578 nm, acid and basic forms, respectively) with a quantum yield between 14 and 16% and an excited-state lifetime of 7.7-7.8 ns. Importantly, the protonated form 1a·H(+) provokes a specific staining of late endosome compartments (pH 5.0-5.5) after 5 h of incubation with HeLa cells. Not surprisingly, this late endosome marking depends on the intra-organelle pH, and changing the nature of the lipophilic chain provokes a loss of selectivity. Interestingly, fixation of the fluorophore is readily achieved with paraformaldehyde, giving the possibility to image both live and fixed cells.

We present here a new family of pH insensitive ion-selective optical sensors based on emulsified nanospheres containing densely functionalized 15-, 16-, 18- and 20-membered pyreneamide derivatives. These compounds were successfully synthesized by the reaction of α-diazo-β-ketoesters with cyclic ethers of the desired size in the presence of dirhodium complexes followed by a stereo-selective tandem amidation-transposition process and characterized by 1H-NMR, 13C-NMR, IR, HR-ESI-MS, UV-VIS and fluorescence spectroscopy and potentiometry. Their unique structure consisting of a crown ether ring linked to pyrene moieties through amide groups exhibits on–off switchable behavior upon binding of specific cations and allows one to incorporate these chemosensors as fluorescent ionophores into ion-exchange nanospheres. The nanosphere matrix is composed of bis(2-ethylhexyl)sebacate (DOS), poly(ethylene glycol) (PEG), sodium tetrakis 3,5-bis(trifluoromethyl)phenyl borate and pyreneamide functionalized 18-crown-6 ether (18C6). These optode nanoparticles exhibit a strong affinity to the potassium cation over other metal ions up to the millimolar concentration range in an exhaustive detection mode. The logarithmic complex formation constant was determined using the segmented sandwich membrane method and was found to be 6.5 ± 0.3 (SD) in PVC membrane plasticized with NPOE and 5.3 ± 0.3 (SD) in DOS with a 1 : 1 complex stoichiometry. The nanosensors were characterized in broad range of pH from 4 to 10 and the same linear calibration curves were obtained in the concentration range from 10−7 M to 10−5 M and thus the pH dependent response was largely overcome. These nanosensors are sufficiently stable, simple to prepare, exhibit a rapid response and their nanoscale size makes them suitable for sensing purposes in samples of limited dimensions.

A series of chiral fluorescent macrocycles display a remarkable combination of both +/– ECD and strong on/off CPL reversible switching upon cation binding and displacement., Straightforward synthesis and resolution of a series of chiral fluorescent macrocycles are presented, together with their electronic circular dichroism (ECD), strong excimer fluorescence (EF, λ 300 to 650 nm) and allied highly circularly polarized luminescence (CPL, glum up to 1.7 × 10–2). The ECD, EF and CPL responses are strongly affected by the presence of metal ions (Na+, Ba2+) thanks to deep conformational changes. While ECD signals can be almost completely reversibly inverted upon the complexation/decomplexation of metal ions in a typical binary response, CPL signals are reversibly quenched concomitantly. The designed macrocycles display thus a remarkable combination of both +/– ECD and on/off CPL reversible switching.

A series of nine C‐functionalized cationic diazaoxatriangulene (DAOTA) dyes have been successfully synthesized and fully characterized, including X‐ray structural analysis of four derivatives. The introduction of electron‐withdrawing or ‐donating functions enables the tuning of both electro‐ and photochemical properties with, for instance, two consecutive (reversible) reductions or oxidations observed for nitro or amino derivatives, respectively. The substituents also impacted on the optical properties, with absorption maxima varying from λ=528 to 640 nm and fluorescence being shifted from the yellow to the red range, up to λ=656 nm.

International audience; Twelve cationic helicenes and one triangulene were tested for the specific labeling of mitochondria from algal cells. Octyl ester derivative 5 readily penetrates algal cells and gives rise to clear fluorescence patterns when it is used at concentrations in the μM range. Under these conditions, cell structures are well preserved and cell survival is not compromised. Cationic helicene compounds such as 5 provide new useful tools for examining the mitochondrial network and its dynamics including fission and fusion events.

Polycyclic indoline‐benzodiazepines can be accessed through the intermolecular reaction of Tröger bases with N‐sulfonyl‐1,2,3‐triazoles. Under RhII catalysis, α‐imino carbenes are generated and a subsequent cascade of [1,2]‐Stevens, Friedel–Crafts, Grob, and aminal formation reactions yield the polycyclic heterocycles as single isomers (d.r.>49:1, four stereocenters including two bridgehead N atoms). Further ring expansion by insertion of a second α‐imino carbene leads to elaborated polycyclic 9‐membered‐ring triazonanes.

A novel CH2 -extrusion reaction leading to the transformation of ethano-Tröger bases into disubstituted methano derivatives is reported (yields up to 93 %). Under mild and metal-free oxidative conditions, a loss of CH2 and a ring contraction are provoked. Despite two bond cleavages at stereogenic nitrogen and carbon centers and a temporary rupture of the bicyclic structure, a very high enantiospecificity (es≥98 %) is observed for this unusual reaction.

(Cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate [CpRu(CH3CN)3][PF6] in combination with pyridine-hydrazone ligands efficiently catalyzes the asymmetric decarboxylative allylic rearrangement of allyl aryl carbonates. Formation of C[BOND]O bonds with high regio- and enantioselectivity ratios (up to 95:5 and 98% ee) is obtained. Good stereocontrol of the pseudotetrahedral geometry of the CpRu moiety is achieved by the hydrazone ligand and its “electron-poor” nature is evidenced through the epimerization of the hexacoordinated TRISPHAT-N anion.

A series of bis(pyreneamide) macrocycles, synthesized in two steps from THF, THP, oxepane and 1,4-dioxane, are tested as chemosensors for a large range of mono-, di- and trivalent cations. In their native states, these macrocycles exhibit a strong excimer fluorescence that is quenched upon the addition of the metal ions (alkaline, alkaline earth, p-, d-, and f-block metals). UV-Vis spectrophotometric titrations, cyclic voltammetry, excimer fluorescence quenching, and transient absorption spectroscopy experiments helped characterize the On-Off changes occurring upon binding and demonstrate that the highest stability constants are obtained with divalent cations Ca2+ and Ba2+ specifically.

A strategy for late-stage electrophilic functionalizations of cationic helicenes is exposed. Thanks to strongly acidic conditions that permit reversible electrophilic substitutions, regioselective acylations, sulfonylations, or alkylations occur at the extremity(ies) of the helical cores. Extended [5] or [6]helicenes can then be generated from cationic [4]helicenes in successive one-pot elongation processes. Retention of configuration and excellent enantiospecificity (up to 99 %) are observed for the helicene growth in the enantiopure series.

In the context of Troger base chemistry, regio- and stereoselective Csp3 -H azidation reactions are reported. Azide functional groups are introduced at either one or the two benzylic positions selectively. Mild conditions and good yields are afforded by the combination of TMSN3 and iodosobenzene PhIO. The process occurs with high enantiospecificity (es 96-99 %) and-interestingly and importantly-via bridgehead iminium intermediates as shown by mechanistic and in-silico studies. Finally, mono- and bistriazole derivatives were prepared in high yields and enantiospecificity by using copper-catalyzed alkyne azide cycloaddition (CuAAC) reactions; some of the products were used as anion-binding organocatalysts for the tritylation of amines and alcohols.

The electrochemistry and annihilation electrochemiluminescence (ECL) of a series of chiral cationic helicene luminophores containing various substituents were investigated in acetonitrile solvent. The electrochemical characterization evidenced a systematic reversible reduction of cationic derivatives, whereas the oxidation could be reversible or not, depending on the nature of the core heteroatoms within the structure as well as the functional-group appendages. One of the key parameters governing the ECL intensity is, indeed, the formal redox potentials for the electrogeneration of the neutral radical and dication radical species, which will undergo the annihilation reaction. On that basis, a thermodynamic wall of efficiency was proposed in the case of ECL annihilation pathway to predict the formation efficiency of the emitting excited state and, eventually, the light emission‘s strength. This very simple wall is constructed by plotting the difference of formal potentials in function of the fluorescence wavelength, thus delimiting two domains where ECL is thermodynamically possible or unfavorable.

Ester, amide, and directly linked composites of squalene and cationic diaza [4]helicenes 1 are readily prepared. These lipid-dye constructs 2, 3, and 4 give in aqueous media monodispersed spherical nanoassemblies around 100–130 nm in diameter with excellent stability for several months. Racemic and enantiopure nanoassemblies of compound 2 are fully characterized, including by transmission electron microscope and cryogenic transmission electron microscope imaging that did not reveal higher order supramolecular structures. Investigations of their (chir)optical properties show red absorption maxima ≈600 nm and red fluorescence spanning up to the near-infrared region, with average Stokes shifts of 1350–1550 cm−1. Live-cell imaging by confocal microscopy reveals rapid internalization on the minute time scale and organelle-specific accumulation. Colocalization with MitoTracker in several cancer cell lines demonstrates a specific staining of mitochondria by the [4]helicene–squalene nanoassemblies. To our knowledge, it is the first report of a subcellular targeting by squalene-based nanoassemblies.

Cationic azaoxa[4]helicenes can be prepared in a single step from a common xanthenium precursor by addition of nucleophilic amines under monitored conditions (160 °C, 2 min, MW). The (−)-(M) and (+)-(P) enantiomers can be separated by chiral stationary-phase chromatography. Determination of the absolute configuration and racemization barrier (ΔG(433 K) 33.3 ± 1.3 kcal·mol–1) was achieved by VCD and ECD spectroscopy, respectively. Cationic azaoxa[4]helicenes can be prepared in a single step from a common xanthenium precursor by addition of nucleophilic amines under monitored conditions (160 °C, 2 min, MW). The (−)-(M) and (+)-(P) enantiomers can be separated by chiral stationary-phase chromatography. Determination of the absolute configuration and racemization barrier (ΔG(433 K) 33.3 ± 1.3 kcal·mol–1) was achieved by VCD and ECD spectroscopy, respectively.

International audience; A chiral cationic helicene, which is depicted in the image, has been found to be a powerful dye and fluorophore that emits circularly polarized light in the red to far‐red region.

Densely functionalized polyether macrocycles can be prepared in one pot in yields up to 60% by the rhodium(II)-catalyzed decomposition of methyl diazoacetoacetate in the presence of a variety of substituted or unsaturated 5- and 6-membered ring cyclic ethers. A comprehensive analysis of the solid state conformations of the macrocyclic geometries is detailed as well as novel mechanistic insights about the multi-component condensation reaction.

Enantiopure binaphthyl azocines can be prepared in a single step via the direct copper-catalyzed reaction of binaphthyl azepines and α-diazo carbonyl reagents. The [1,2]-Stevens rearrangement is general (61-93% yields) and can be extended to [3]ferrocenophanes; similar reactivity in favor of the products of ring expansion is obtained with these ferrocene derivatives (80-96% yields).

The interaction of a series of chiral cationic [4]helicene derivatives, which differ by their substituents, with double-stranded DNA has been investigated by using a combination of spectroscopic techniques, including time-resolved fluorescence, fluorescence anisotropy, and linear dichroism. Addition of DNA to helicene solutions results to a hypochromic shift of the visible absorption bands, an increase of fluorescence quantum yield and lifetime, a slowing down of fluorescence anisotropy decay, and a linear dichroism in flow-oriented DNA, which unambiguously points to the binding of these dyes to DNA. Both helicene monomers and dimeric aggregates, which form at higher concentration, bind to DNA, the former most probably upon intercalation and the latter upon groove binding. The binding constant depends substantially on the dye substituents and is, in all cases, larger with the M than the P enantiomer, by factors ranging from 1.2 to 2.3, depending on the dye.

A direct nitrene insertion into C-N bonds is observed upon treatment of methano-Tröger bases with arylsulfonyl iminophenyliodinanes under copper and dirhodium catalysis. Novel cyclic imino-methano Tröger bases are obtained (55-88%). Enantiopure products (ee ≥ 99%) can be obtained with tailored substrates.

Unprecedented regioselective post-functionalization of racemic and enantiopure cationic diaza [4]helicenes is afforded. The peripheral auxochrome substituents allow a general tuning of the electrochemical, photophysical and chiroptical properties of the helical dyes (26 examples). For instance, electronic absorption and circular dichroism are modulated from the orange to near-infrared spectral range (575–750 nm), fluorescence quantum efficiency is enhanced up to 0.55 (631 nm) and circularly polarized luminescence is recorded in the red (|glum| ∼ 10−3).

Doubly bridged biphenyl azocines can be prepared in a single step through copper-catalyzed reactions of a doubly bridged biphenyl azepine and diazodiester reagents. Double [1,2]-Stevens rearrangements occur at 100 °C to afford doubly tethered eight-membered rings (49 to 61%) as trans and cis regioisomers (1:1 ratio). These products present an axial chirality. ECD and VCD analyses of the separated enantiomers (CSP-HPLC) were used to assign the absolute configuration. High configurational stability is observed for both regioisomers as racemization does not occur after 1 week of heating at 208 °C in dodecane (ΔG ‡ > 41 kcal·mol–1). Interestingly, reactions performed at 40 °C retain a certain level of enantiospecificity (82–86%), avoiding, for the most part, thermal racemization of the starting material.

Reactions of α-diazo-β-ketoesters with cyclic ketones, lactones, and carbonates are reported. Thanks to the combined use of salt [CpRu(CH3CN)3][BArF] and 1,10-phenanthroline as catalyst for the diazo decomposition, effective and practical syntheses of spiro bicyclic ketals, orthoesters, and orthocarbonates are afforded.