New Heptazines for efficient selective organophotocatalysis. – HEPTA-cat

Heptazine polymers have been recently recognized for their exceptional catalytic properties, (even water splitting), but examples of well-defined tunable monomeric heptazines are still scarce, because of severe synthetic limitations (before 2019, all syntheses relied on trichloroheptazine, obtained using PCl5 at high temperature). We want to take advantage of a recent discovery on heptazines synthesis (by the coordinator’s team, Partner 1), to develop a set of new photoactive heptazines, starting from new derivative with exchangeable pyrazoles, TDPH, prepared by mechanochemistry. From TDPH, the second to date heptazine described with exchangeable groups, we will generate a whole family of heptazines with adapted properties (especially adapted redox potentials by tuning the electron deficiency of the substituents) adequate for the collaborative tasks defined below.
The project will gather the coordinator’s team and his partners in exploring the synthesis of new sets of heptazines and establishing their photophysical properties. This will be performed in close connections with DFT studies performed by our Partner 2 (TUM), in particular to estimate the redox potential of the excited state of several heptazines and to select most relevant heptazines for subsequent work.
Heptazines are exceptional photooxidants (from the preliminary results in the coordinator’s team, likely the best organic photooxidants to date, comparable to iridium complexes). Their seminal catalytic potential to oxidize organic molecules was demonstrated in collaboration with our Partner 3 (ICSN). Here, we will explore more challenging photocatalyzed reactions. Heptazines should be able to oxidize unreactive positions (Csp3-H activation). As such, yet unsolved direct a-functionalization of simple primary,, or acyclic secondary aliphatic amines will be targeted. We will also tackle unprecedented organocatalyzed remote NH aliphatic amines functionalization and double a- and remote functionalization of aliphatic amines.
With our Partner 4 (IRCER), we will also meanwhile, and afterwards, graft some of our active heptazines on hard recyclable materials like oxides, or possibly nanocarbons. This should lead to interesting complex 3D micro(nano)structures and architectures. Collaboration between Partner 4 and Partner 3 should also allow moving from homogeneous to heterogeneous catalysis, aiming at using solid supported heptazines in photocatalytic organic transformation to benefit from recyclability and easy purification.