Maude Desroches

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.

The importance of the amide configuration in the gelation process and topochemical polymerization of phenylacetylene macrocycles

Two series of amide-containing phenylacetylene macrocycles (PAMs) were prepared and self-assembled through a gelation process in an organic solvent. Their gelation properties along with their molecular arrangements in the xerogel state, their morphological features and their reactivity toward the topochemical polymerization of the butadiyne units embedded within the structure were studied with respect to the amide configuration. The PAMs of series 1 with the nitrogen atom of the amide function directly attached to the phenyl groups of the PAMs (acetanilide derivatives) showed less organized molecular organization and less reactivity toward topochemical polymerization than the PAMs of series 2 with the inverted amide configuration (benzamide derivatives). The importance of the amide configuration in the gelation process was confirmed by theoretical calculations at the density functional theory level. Moreover, the computed architecture for molecules of series 1 was shown to be incompatible with topochemical reaction in agreement with experimental observation. The actual combination of experiments and calculations allows the design of larger covalently linked, rigid organic nanotubes.

Wurster-Type Nanographenes as Stable Diradical Dications

Three new and stable diradical dications based on the 4,10-dibromoanthanthrone have been synthesized and characterized. In their dicationic state, the amines show a biradical character in the ground state. Their magnetic properties have been investigated by NMR and EPR spectroscopies. The dicationic salts shows strong and broad optical absorption in the near-infrared region. The main driving force to obtain a ground state biradical is the high steric hindrance that prevents planarization of the diphenylamines with the anthanthrone aromatic core. The radical cations are isolated in two perpendicular π-systems as demonstrated by X-ray diffraction structures. This work provides a new bridging unit in the search for biradical bis(triarylamines) salts.

Breaking Bonds and Forming Nanographene Diradicals with Pressure

New anthanthrone-based polycyclic scaffolds possessing peripheral crowded quinodimethanes have been prepared. While the compounds adopt a closed-shell butterfly-shaped structure in the ground state, a curved-to-planar fluxional inversion is accessible with a low energy barrier through a biradicaloid transition state. Inversion is primarily driven by the release of strain associated with steric hindrance at the peri position of the anthanthrone core; a low-lying diradical state is accessible through planarization of the core, which is attained in solution at moderate temperatures. The most significant aspect of this transformation is that planarization is also achieved by application of mild pressure in the solid state, wherein the diradical remains kinetically trapped. Complementary information from quantum chemistry, 1 H NMR, and Raman spectroscopies, together with magnetic experiments, is consistent with the formation of a nanographene-like structure that possesses radical centers localized at the exo-anthanthrone carbons bearing phenyl substituents.

Anthanthrene as a Super-Extended Tetraphenylethylene for Aggregation-Induced Emission

Seven π-extended derivatives of the known tetraphenylethylene (TPE) have been studied for their aggregation-induced emission properties. Modulation of the emission properties of these anthanthrone-based luminogens has been accomplished through simple chemical modifications on four different positions of the anthanthrone core. The optical properties, along with X-ray diffraction and DFT-optimized structures, were studied. This work provides a new, easily accessible bridging unit for the TPE framework with a red-shifted emission.

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.

Wurster-Type Anthanthrene Polyradicaloid Cations

4,10-dibromoanthanthrone, a highly robust building block, is used to synthesize a bis(triarylamine) polymer. The polymer can be oxidized twice to form a polycationic macromolecule showing magnetic properties by electron paramagnetic resonance spectroscopy. In its dicationic state, the presence of isolated radicals is possible because of the interrupted conjugation between the diphenylamine with the anthanthrone core. The high steric hindrance prevents the planarity of the adjacent groups resulting in a polyradical cationic polymer. The oxidized polymer has a strong absorption in the near-infrared region along with reversible redox stages.

Synthesis and properties of a trapezoid shaped macrocycle with different [n]yne units

A new alkyne-based macrocycle that combines monoyne, diyne and tetrayne is reported. Despite its unusual trapezoid shape, the bending of the tetrayne unit allows the macrocycle to be unstrained. The macrocycle is synthesized by a combination of selective deprotection of silylated alkyne, Castro–Stephen–Sonogashira coupling and copper-mediated oxidative homocoupling. The final intramolecular cyclization proceeded in surprisingly high yield (72%) using modified Eglinton conditions in moderate dilution.