Research Projects

In recent times, radical molecules have garnered much attention in comparison to conventional fluorophores because of their high quantum efficiency (100%). In conventional fluorescent molecules, only 25% quantum efficiency from a singlet state and 75% quantum efficiency from a triplet state can be achieved, respectively, due to the spin selection rule. Whereas 100% quantum efficiency can be obtained from radical molecules for their spin-allowed transition, i.e., the doublet-doublet (D1 → D0) transition from the lowest-energy excited state (D1) to a singly occupied molecular orbital (D0). Thus, radicals have emerged as promising molecules in chemistry, organic optoelectronics, and material science owing to their intriguing optical, electronic, and magnetic properties. However, organic radicals, despite their potential applications, have suffered from instability under ambient conditions because of dimer/polymerization or being quenched by oxygen and, subsequently, loss of fluorescence via radical coupling. This proposal aims to develop highly fluorescent and stable radicals to achieve high quantum efficiency and address the above limitations by innovative molecular design, which will create new possibilities for various applications. This proposal is built on the unique design strategy to synthesize air-stable radicals, particularly those containing sterically bulky moieties to protect the radical centers. By conjugating these radicals with oligo-thiophenes, the goal is to obtain a new class of molecules that retain radical characteristics while exhibiting high luminescence. The oligo-thiophenes are selected judicially. With tunable electronic properties and structural rigidity, oligo-thiophenes have proven to be versatile building blocks in organic electronics. However, their application in radical chemistry remains unexplored. It is hypothesized that the conjugation of oligo-thiophene units with radical frameworks could synergistically enhance radical stability and fluorescence properties. The project object is to prevent radical quenching through molecular engineering, particularly by decoupling the radical's electron with the conjugated backbone of the oligothiophene framework. This serves as a foundation for exploring structural modifications in oligo-thiophene systems, such as incorporating various electron-donating substituents to fine-tune their optical and electronic behavior as well as to balance the delocalization of the radical electron over the π-conjugated molecular framework. Additionally, a variety of polyaromatic hydrocarbons (such as naphthalene, anthracene, pyrene, etc.) will be incorporated on the periphery to fine-tune the electronic properties of the π-radical systems. The proposed donor-appended and polyaromatic hydrocarbons coupled oligo-thiophene-conjugated organic π-radicals aim to attain air stability and high quantum efficiencies and provide next-generation fluorescent molecules for advanced applications.