Maxime Daigle

Helically Coiled Graphene Nanoribbons

Graphene is a zero-gap, semiconducting 2D material that exhibits outstanding charge-transport properties. One way to open a band gap and make graphene useful as a semiconducting material is to confine the electron delocalization in one dimension through the preparation of graphene nanoribbons (GNR). Although several methods have been reported so far, solution-phase, bottom-up synthesis is the most promising in terms of structural precision and large-scale production. Herein, we report the synthesis of a well-defined, helically coiled GNR from a polychlorinated poly(m-phenylene) through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction. The structure of the helical GNR was confirmed by 1 H NMR, FT-IR, XPS, TEM, and Raman spectroscopy. This Riemann surface-like GNR has a band gap of 2.15 eV and is highly emissive in the visible region, both in solution and the solid state.

Rigid organic nanotubes obtained from phenylene-butadiynylene macrocycles

Rigid organic nanotubes were prepared from six-membered phenylene-butadiynylene macrocycles through topochemical polymerization in the xerogel state. All six butadiyne units underwent polymerization, thus creating rigid nanotubes with six polydiacetylene chains lying parallel, one relative to each other.

Layered graphitic materials from a molecular precursor

A layered graphitic material was prepared from an alkyne-containing, reactive molecular precursor at low temperature without catalyst. The resulting nanomaterial is made of stacks of a few partially graphitized nanosheets and is soluble in common organic solvents in which it exhibits green fluorescence.

Regioselective Synthesis of Nanographenes by Photochemical Cyclodehydrochlorination

Novel nanographenes were prepared by a photochemical cyclodehydrochlorination (CDHC) reaction. Chlorinated precursors were irradiated in acetone in the presence of a base or in pure benzene and underwent multiple (up to four) regioselective cyclization reactions to provide rigid π-conjugated molecules. Pure compounds were recovered in good yields by simple filtration at the end of the reaction. The CDHC reaction showed compatibility with both electron-poor and electron-rich substrates, thus allowing the synthesis of pyridine- and thiophene-fused nanographenes. It also enabled the synthesis of sterically hindered contorted π-conjugated molecules without causing full aromatization. A kinetic study showed that the CDHC reaction under the conditions used is a very fast process, and some reactions are completed within minutes. The CDHC reaction thus shows great potential as an alternative to other reactions involving harsher conditions for the preparation of nanographenes.

Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification.

Summary The synthesis and self-assembly of two new phenylacetylene macrocycle (PAM) organogelators were performed. Polar 2-hydroxyethoxy side chains were incorporated in the inner part of the macrocycles to modify the assembly mode in the gel state. With this modification, it was possible to increase the reactivity of the macrocycles in the xerogel state to form polydiacetylenes (PDAs), leading to a significant enhancement of the polymerization yields. The organogels and the PDAs were characterized using Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Synthesis of Carboxylate Cp*Zr(IV) Species: Toward the Formation of Novel Metallocavitands

With the intent of generating metallocavitands isostructural to species [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+), the reaction of Cp*2ZrCl2 and Cp*ZrCl3 with phenylcarboxylic acids was carried out. Depending on the reaction conditions, five new complexes were obtained, which consisted of Cp*2ZrCl(κ(2)-OOCPh) (1), (Cp*ZrCl(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2 (2), [(Cp*Zr(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2(μ(2)-OH)2]·Et2O (3·Et2O), [[Cp*ZrCl2](μ-Cl)(μ-OH)(μ-O2CC6H5)[Cp*Zr]]2(μ-O2CC6H5)2 (4), and [Cp*ZrCl4][(Cp*Zr)3(κ2-OOC(C6H4Br)3(μ3-O)(μ2-Cl)2(μ2-OH)] [5](+)[Cp*ZrCl4](-). The structural characterization of the five complexes was carried out. Species 3·Et2O exhibits host-guest properties where the diethyl ether molecule is included in a cavity formed by two carboxylate moieties. The secondary interactions between the cavity and the diethyl ether molecule affect the structural parameters of the complex, as demonstrated be the comparison of the density functional theory models for 3 and 3·Et2O. Species 5 was shown to be isostructural to the [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+) metallocavitands.

Carbon nanomaterials from pyrolysis of polydiacetylene-walled nanorods

Pyrolysis of polydiacetylene-walled nanorods obtained from a rigid and shape-persistent macrocyclic precursor was performed. The thermogravimetric analysis showed that pyrolysis caused a loss of aliphatic chains and structural changes of PDAs to produce carbon-rich nanoarchitectures, as confirmed by Raman and UV-visible spectroscopy. The transmission electron microscopy imaging performed on the resulting material showed the formation of an entangled nanofibrils network containing various types of nanostructures.

Tetraphenylethene–diyne hybrid nanoparticles from Glaser-type dispersion polymerization

Organic-based nanoparticles hold great potential for optoelectronics and biomedicine as they may provide optical properties in the visible range and notable advantages over inorganic counterparts. In this report, we exploit aggregation-induced emission (AIE) from the well-known tetraphenylethene (TPE) to yield photoluminescent polymer particles by a dispersion polymerization route. 1,1-Bis(4-ethynylphenyl)-2,2-diphenylethene is polymerized by a Glaser-type dispersion polymerization, providing nanoparticles of 170–600 nm with low polydispersity by simply varying monomer loadings. Optical characterization reveals emission bands at 500 nm and 600 nm, where UV irradiation of the particles causes the 500 nm band to increase relative to the 600 nm one. Structural characterization by 13C MAS-NMR allows confirming that this change upon UV irradiation is not induced by a chemical modification, thus suggesting a physical change in the particles morphology. Altogether, the results of this work allow enlarging the library of TPE-comprising particles, but also enhance the variety of particles synthesized from Glaser-type dispersion polymerization. The study also allows gaining insight into the photochemical stability of TPE-containing particles, where the non-destructive UV irradiation lets us plan the development of new polyyne/TPE hybrid systems.