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Photophysical studies on a BODIPY-fullerene-distyryl BODIPY triad (BDP-C

International audience; The synthesis of a methanofullerene platform bearing on one side an alkyne and on the other a protected alkyne is reported. This clickable fullerene building block was functionalized by two distinct BODIPY azido derivatives using a 1 st CuAAC/alkyne deprotection /2 nd CuAAC, sequence, through either stepwise or one-pot processes in an efficient manner. The triad displays strong absorption from 300 to 700 nm. The strong fluorescence quenching observed for the two BODIPYs within the triad is probably due to photo-induced energy and/or electron transfer events.

International audience; A new donor–acceptor dyad composed of a BODIPY (4,4′-difluoro-4-bora-3a,4a-diaza-s-indacene) donor and a fullerene C60 acceptor has been synthesized and characterized. This derivative has been prepared using a clickable fullerene building block that bears an alkyne moiety and a maleimide unit. The post-functionalization of the maleimide group by a BODIPY thiol leads to a BODIPY-C60 dyad, leaving the alkyne moiety for further functional arrangement. On the basis of the combination of semi-empirical and density functional theory (DFT) calculations, spectroelectrochemical experiments, and steady-state and time-resolved spectroscopies, the photophysical properties of this new BODIPY-C60 dyad were thoroughly studied. By using semi-empirical calculations, the equilibrium of three conformations of the BODIPY-C60 dyad has been deduced, and their molecular orbital structures have been analyzed using DFT calculations. Two short fluorescence lifetimes were attributed to two extended conformers displaying variable donor–acceptor distances (17.5 and 20.0 Å). Additionally, the driving force for photoinduced electron transfer from the singlet excited state of BODIPY to the C60 moiety was calculated using redox potentials determined with electrochemical studies. Spectroelectrochemical measurements were also carried out to investigate the absorption profiles of radicals in the BODIPY-C60 dyad in order to assign the transient species in pump–probe experiments. Under selective photoexcitation of the BODIPY moiety, occurrences of both energy and electron transfers were demonstrated for the dyad by femtosecond and nanosecond transient absorption spectroscopies. Photoinduced electron transfer occurs in the folded conformer, while energy transfer is observed in extended conformers.

The synthesis of a C60-peptide using “clickable” fullerene and peptide derivatives is described. The peptide is composed of a repeating sequence of α-aminoisobutyric acid (Aib) and two L-alanine (Ala) residues, promoting the formation of a helical conformation, which has been confirmed by IR absorption, NMR and circular dichroism measurements. In addition, the presence of a lipoyl moiety, at the end of the peptide sequence, allows the formation of self-assembled monolayers of the C60-peptide and the parent peptide on a gold surface. A C60-alkyl derivative was also prepared to compare the self-assembly properties of fullerene derivatives containing peptides or alkyl chains. The fullerene assembly on a gold substrate characterized by quartz crystal microbalance and by cyclic voltammetry show that the monolayers containing alkyl chains are slightly less well packed than the peptide monolayers. Finally, polarization modulation reflection adsorption infra-red spectroscopy measurements indicate that the C60-peptide tends to be more vertical than the parent peptide which could originate from complementary C60–C60 and helical–helical interactions.

International audience; An easily synthesized α-hydroxy-β-azidotetrazole scaffold was used to build a three dimensional polychromic system. Different chromophores (coumarin, BODIPY and distyryl BODIPY) were incorporated into the structure by using sequential CuAAC reactions to form a series of dyads and a triad. A computational study of the resulting arrays showed that the predominant conformations brought the substituents into close spatial proximity. The triad exhibited FRET behaviour with notably efficient energy transfer values.

In this study, the functionalization of a fullerene building block in a stepwise process by means of the copper-catalyzed alkyne-azide cycloaddition (CuAAC) and thiol-maleimide reactions is reported. Grafting of the fullerene platform with a variety of azido derivatives, including Bodipy, pyrene and ferrocene, was carried out first. These fullerene compounds were then reacted with thiol derivatives to yield sophisticated structures comprising photo- and/or electroactive fullerodendrimers and cysteine-functionalized fullerene assemblies. This strategy, which combines the CuAAC and thiol-maleimide processes, could become more widely adopted in the field of fullerene chemistry.

This work deals with the covalent coupling of azide-functionalized polymeric nanoparticles as a reactive core and amino-terminated PAMAM dendrons as a reactive shell. The nanoassemblies thereby obtained could be modified after the dendronization step by grafting an alkynyl Bodipy dye on the unreacted azide moieties. Only a few steps are required to attain nanoassemblies that could mimic dendrimers of high generation with sizes of nano-objects beyond those of dendrimers. The structure of the nanoassemblies are composed of a polystyrene core, an inner shell including the Bodipy dyes along with the internal branches of the PAMAM, and the terminal amino groups from the outer shell. The dendritic shell acts as a protective layer that prevents NP from aggregation in a surfactant free aqueous solution. The nano-objects display absorption and emission maxima above 500 nm with brightness that are the same order of magnitude than Qdots. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 115–126

In this study, the synthesis of an orthogonally clickable fullerene building block mono-adduct bearing on one side an alkyne unit and a maleimide moiety on the other side is presented. This derivative has been involved in CuAAC and thiol–maleimide click reactions using stepwise or one-pot processes with benzyl azide and 1-octanethiol. The one-pot process involving the CuAAC reaction followed by the thiol–maleimide conjugation gives the highest yield. This new platform could pave the way for the synthesis of a wide range of fullerene derivatives exploiting this set of orthogonal reactions.

In this study, the synthesis of water-soluble fullerene derivatives bearing on one side a poly(amidoamine) (PAMAM) dendron with peripheral carboxylic groups and an alkyne moiety on the other side is presented. Fullerodendrimers with tert-butyl ester groups at the periphery were first prepared by treating C60 with unsymmetrical malonates through the use of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)/I2 or DBU/CBr4 conditions. The latter led to an unexpected addition of dibromocarbene on C60. The tert-butyl esters were then cleaved using formic acid and gave the corresponding carboxyfullerene derivatives. The second generation with eight carboxylic groups at the periphery was easily dissolved in water, whereas the first generation with its four carboxylic groups can only be solubilized in a basic medium. These compounds self-assemble into micelle-like aggregates probably composed of a cluster of C60 surrounded by a PAMAM shell. The alkyne moiety was then used as a chemical anchor to immobilize in water fullerodendrimers on the surface of azido-coated polymer nanoparticles by means of the copper(I)-catalyzed azide and alkyne cycloaddition reaction. At room temperature, this reaction is competing with azido cycloaddition onto the fullerene core. Given the high density of azide anchoring groups on the nanoparticle surface and the size of the fullerodendrimers, unreacted azides are still active and are available for subsequent functional arrangements. This strategy paves the way for the design of functional fullerene-rich nanomaterials that could be of interest in the field of materials science.

The convergent synthesis of fluorescent polystyrene core–PAMAM shell nanoparticles in the 15–20 nm diameter range is presented using azido-coated nanoparticles (NPN3) as a clickable platform. The c...

Azamacrocycles bearing four arylsulfonyl or arylsulfinyl pendant arms have been synthesised with good yields through nucleophilic addition of 1,4,8,11-tetraazacyclotetradecane (cyclam) to phenylvinylsulfone, phenylvinylsulfoxide or (R)-tolylvinylsulfoxide in isopropanol/water media. The crystal structure of the tetraethylsulfonylphenyl substituted macrocycle has been determined by X-ray crystallography. Preliminary studies of the coordination properties of these functionalised macrocyles towards Cu(II) and Eu(III) indicate that pendant sulfoxide groups act as oxygen donor coordinating groups.

Conjugate additions of cyclam to perfluorohexyl vinyl sulfone and sulfoxide, which act as efficient fluorous Michael acceptors, readily give access to new fluoro-ponytail tetraazamacrocycles in good yields. The solubility of the N-tetrasubstituted macrocycles depends dramatically on the nature of the polar function (SO or SO2): the sulfoxide cyclam derivative is soluble in perfluorodecaline (pfd) and perfluoromethylcyclohexane (pfmc) while the sulfonyl derivative is almost insoluble in organic or fluorous solvents. In agreement with the well known affinity of cyclam for copper(II) ions, stable copper complexes of the fluorous macrocyclic ligands have been isolated and characterized. In chloroform/methanol, complexes with four perfluorinated tails have been obtained from reaction of the tetra-N-perfluorohexylsulfinyl-substituted macrocycle with copper nitrate and copper perfluorocarboxylate. In trifluoroethanol, a selective retro-Michael reaction has been observed and the same reaction specifically gives copper complexes of the tri-N-substituted macrocycle. Complexes with three and four fluorous tails associated with perfluorocarboxylate counteranions are soluble in fluorous solvents (pfd and pfmc). These copper complexes were tested as catalysts for the oxidation of cyclohexene by molecular oxygen in the presence of tert-butyl hydroperoxide (tbhp). The oxidation reactions proceed under fluorous biphasic conditions and the catalyst can be recovered and reused. Quenching experiments indicate that cyclohexenyl hydroperoxide is the main oxidation product of the reaction performed with or without tbhp. Interestingly, these perfluorinated copper complexes are good, recyclable catalysts for the oxidation of cyclohexene by molecular oxygen without tbhp at room temperature and 65 °C.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

N,N′-disubstitution of cyclam without the use of protecting groups was investigated. This macrocycle reacted with two equivalents of a Michael acceptor in chloroform to yield as a major isolated compound the 1,8 di-N,N′-substituted macrocycle. Running the same reaction in the presence of one equivalent of para-toluenesulfonic acid led to the 1,11-di-N,N′-substituted macrocycle as the major product. Each regioisomer has been isolated and fully characterized. The observed regioselectivity is discussed with respect to the reactivity of the unprotonated or protonated monoalkylated intermediate. A site of protonation for the latter intermediate is deduced from an NMR study. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

N-Monoalkylated azamacrocycles are selectively obtained by reacting cyclam (1,4,8,11-tetraazacyclotetradecane) with equimolar amounts of Michael acceptors in chloroform in the presence of one equivalent of acid (TsOH). This chemoselective addition provides a general route to new mono-substituted azamacrocycles with various pendant groups such as sulfonic acid, ester, amide, nitrile, sugar or crown ether. The selectivity for monoaddition results from protonation of the azamacrocycles in the presence of one equivalent of acid.

Bis-tetraazacyclotetradecanes (bis-cyclam) are readily prepared with fairly good yields in a one step procedure from non-protected cyclam. The synthesis involves a selective addition of cyclam on bis-acrylamides in chloroform in the presence of one equivalent of p-toluenesulfonic acid.

New reactive-surfactants, N-alkylglucosylacrylamides and N-alkylglucosylmethacrylamides, are easily prepared in two steps from glucose without protection. The complete structural analysis of these compounds by 1D and 2D NMR spectroscopy shows the existence of a rotational isomerism that is strongly dependent on the steric hindrance of the carbonyl substituent: whatever the alkyl chain length, both endo and exo rotamers are observed for N-alkylglucosylacrylamides 1 while the endo rotamer is the sole species observed in the case of N-alkylglucosylmethacrylamides 2. For acrylamido derivatives 1, the exo-endo equilibrium is solvent-dependent: the endo isomer is favored in polar nonaqueous solvents (endo-exo isomeric ratio R = 70/30) while the equilibrium is shifted toward the exo rotamer in protic acidic medium (R = 50/50 in water and 80/20 in acidic medium). An intramolecular hydrogen bond is assumed to be responsible for the increased stability of the endo rotamer. Furthermore, for tetra-O-acetylated derivatives the exo rotamer becomes favored in aprotic solvents. Surface tension measurements demonstrate that N-octyl- to -tetradecyl-substituted compounds 1 and 2 are surfactants with critical micelle concentrations ranging from 1.2 x 10(-2) to 1.7 x 10(-5) mol/L.

Bis-tetraazacyclotetradecanes (bis-cyclam) are readily prepared with fairly good yields in a one step procedure from non-protected cyclam. The synthesis involves a selective addition of cyclam on bis-acrylamides in chloroform in the presence of one equivalent of p-toluenesulfonic acid.