Design Strategies Towards Stabilization of Organic Radical Ions and their Electroactive Partners
p-conjugated molecules are intriguing building blocks to realize diverse range of closed and open-shell molecular materials.1 The major challenge facing their applications is the intrinsic reactivity of highly electron-deficient and electron-rich molecules in the neutral and radical ion forms. In this context, the naphthalenediimide (NDI) and the perylenediimide (PDI) p-scaffolds provide an intriguing platform to design new electro-active molecules.2
In this talk, we would discuss how the arylenediimide scaffolds integrated with specific design elements3a can be utilized to synthesize and isolate new ambient stable radical ions. We have recently extended our efforts in synthetic spin chemistry towards the development of eco-friendly synthetic protocols towards radical ions.3b Along with this, we recently isolated new planar as well as twisted ambient stable radical anions as well as the strongest electron acceptors with calculated LUMO of -5.2 eV.4a,b Considering the other end of the electrochemical window, we have been able to isolate highly electron-rich, di-reduced NDI systems, which have an unusual doubly zwitterionic molecular structure and redox switchable aromatic-antiaromatic sites.5 In short, we would discuss the possibilities to expand the electrochemical window of the arylenediimides maintaining their ambient stability. We believe their excited states would be of interest for photocatalysis and other relevant opto-electronic applications.
1. Morita, Y.; Suzuki, S.; Sato, K.; Takui, T.Nature Chem. 2011, 3, 197.
2. A review on electron-poor arylenediimides: Kumar, S.; Shukla, J.; Kumar, Y.; Mukhopadhyay, P. Org. Chem. Front., 2018, 5, 2254.
3. a) Kumar, S.; Ajayakumar, M. R.; Hundal, G.; Mukhopadhyay, P. J. Am. Chem. Soc. 2014, 136, 12004; b) Kumar, S.; Mukhopadhyay, P. Green. Chem. 2018, 20, 4620.
4. a) Kumar, Y.; Kumar, S.; Mandal, K.; Mukhopadhyay, P. Angew. Chem. Int. Ed. 2018, 57, 16318; b) Kumar, Y.; Kumar, S.;Bansal, D.; Mukhopadhyay, P. Org. Lett. 2019,21,2185.
5. Kumar, S.; Shukla, J.; Kumar, Y.; Mandal, K.; Prakash, R.; Ram, P.; Mukhopadhyay, P. Chem. Sci. 2019, 10, 6482.