Employing Click Chemistry to Expand the Scope of the Metal‐Free Donor‐Acceptor‐Type Photocatalyst 4CzIPN

Abstract

AbstractThe design of a versatile alkyne‐bearing derivative of the donor‐acceptor fluorophore 2,4,5,6‐tetrakis(9H‐carbazol‐9‐yl) isophthalonitrile (4CzIPN) suitable for further targeted modifications by copper‐catalysed Azide Alkyne Cycloaddition (CuAAC) is reported. The newly synthesised photoredox catalyst notably exhibits analogously unique photoelectronic and steric features as the well‐established carbazolyl dicyanobenzene motif and performs equally in a C−C‐Coupling model reaction. Furthermore, the variability of this donor‐acceptor system was demonstrated by the generation of a library of fourteen photoredox catalysts with electron‐withdrawing and ‐donating groups as well as residues with high steric demands in one simple and selective CuAAC reaction. The modified catalysts feature a broad scope of reducing and oxidising powers in their excited states (span of reducing powers over more than 1 V) and were also successfully applied in the photoredox and nickel‐catalysed decarboxylative cross coupling model reaction. This work represents a method to overcome the limitations in the flexibility of metal‐free donor‐acceptor fluorophores required for the targeted application in organic synthesis and paves the way for the design of customised catalysts with multiple functionalities.