Synthesis, Aromaticity and Reactivity in Distorted Polycyclic Aromatic Hydrocarbons – TWISTAR

TWISTAR proposes an approach based on the intimate collaboration of synthetic organic and physical organic chemists at each and every stages of the project, and two main tasks have been identified: Task 1 for synthesis and Task 2 for physico-chemical studies.

In accordance with the project's predictions, to date we have obtained, not without difficulty, our first highly distorted original chiral PAHs and started the study of their chemical reactivity and physico-chemical properties. The most advanced part of the project, and ahead of the project's expectations, concerns the methodological development of a theoretical chemistry tool to analyze aromaticity in non-planar aromatic molecules, namely 3D isotropic magnetic shielding contour maps.

The progress of the project is excellent. The experimental organic synthesis part which allows to create the objects of our studies is of course the limiting part, but we have now bypassed the main obstacles identified. The experimental physical organic chemistry part has started with our first synthesized molecules. The fundamental theoretical development part on the study of the magnetic properties of chiral PAHs is almost finished and we will now move on to the computational applications of this new approach.

1 submitted manuscript

Large chiral polycyclic aromatic hydrocarbons (PAHs), referred to as chiral nanographenes, form a young and original class of molecules of enormous interest. These molecules can exist as several diastereomers, each existing as a pair of enantiomers, that can more or less rapidly interconvert depending on their flexibility. Unprecedented distortions were measured on the honeycomb network of some highly twisted chiral nanographenes, raising new synthetic and theoretical interests and a demand for more warped PAH structures. The paradigm considered is that distorted benzenoid systems lose some of their local aromatic character, strongly affecting their electronic properties and possibly unleashing the reactivity of otherwise chemically inert sp² hybridized carbon atoms.
We propose fundamental research in the burgeoning field of chiral nanographenes obtained by controlled organic synthesis. The project aims at providing deep insights on the potential, limits and true nature of highly twisted large chiral Polycyclic Aromatic –or not– Hydrocarbons using a global approach combining experimental synthetic organic chemistry and experimental and theoretical physical organic chemistry.