Research Projects

Transition metal-based photosensitizers are extensively used in various applications in photochemistry such as organic light emitting diodes (OLEDs), bioimaging, solar cells, photocatalysis, and photodynamic therapy. Mostly 4d6, 5d6, 4d8, and 5d8 transition metal complexes, for example, ruthenium(II), osmium(II), iridium(III), gold(III), platinum(II), and palladium(II) complexes are used in the above mentioned applications. This is due to having long-lived and highly emissive charge transfer excited states in these complexes. Currently, the major drawback of these photosensitizers is that they are made of rare and precious metals. So, the current goal among the scientists is to replace these expensive photosensitizers with abundant 3d metals. As iron is the most abundant transition metal, scientists are trying to obtain competent photophysical properties of 3d6 iron(II) complexes similar to isoelectronic (4d6 or 5d6), and benchmark ruthenium(II), osmium(II) or iridium(III) complexes which display phosphorescence from triplet metal-to-ligand charge transfer (MLCT) excited states. After a few decades of research only two emissive iron(II) complexes are reported with MLCT lifetime up to 1 ns, and no quantum yields are reported as the emissions are just in the instrumental detection limits. And none of these complexes are used photocatalysis. After an extraordinary discovery of a photoluminescent 3d5 iron(III) hexacarbene complex in 2017 which shows fluorescence from doublet ligand-to-metal charge transfer (LMCT) excited state, scientists got huge interest in the development of luminescent iron(III) complexes. To date there are five-six reports on the development of luminescent iron(III) complexes, and so far doublet LMCT lifetimes up to 2.1 ns and quantum yields up to 2.0% have been achieved and they are used in various photocatalysis. So there is a huge scope to develope iron(III) photoluminescent complexes. This proposal aims for cutting-edge research in the field of development of abundant photosensitizers. Our goal is to develope iron(III) luminescent complexes featuring N-heterocyclic carbene or arylisocyanide ligands as they are strong sigma-donating ligands which help to obtain LMCT excited states. We believe that our proposed molecules will possess longer lifetimes as well as higher quantum yields. Thereafter these newly proposed iron(III) photosensitizers will be used in photoinduced electron transfer catalysis.