Atanu Ghosh
Chemistry - 436
Leveraging light energy for a sustainable future is one of the most promising ways to reduce our
dependence on fossil fuels and lower our carbon footprint. The captivating pursuit of storing light
energy in molecular excited states enthralls chemists due to its ability to provide synthetic
tunability, unlocking unparalleled reactivities and establishing a crucial structure-property
correlation. Fundamental research to understand the molecular excited states is pivotal for rational
molecular designing. My research in the McCusker research group is focused on understanding
the photophysics of cobalt(III) polypyridyl chromophores to apply such systems in various
applications including photoredox catalysis and solar energy conversion.
First-row d
6
-iron(II) based transition metal complexes have been well explored as an
alternative to low abundant, expensive second and third row chromophores because of their
remarkable light absorbing properties. However, the presence of lower lying metal-centered
ligand-field excited states deactivate the charge-transfer excited states, limiting their potential in
energy conversion applications. New ligand design to increase the performance requires deep
understanding of ligand-field strength. Unfortunately, strong visible light absorption cross-section
of Fe(II) chromophores obscures the weak (low molar extinction coefficient) ligand-field
absorption bands. Isoelectronic Co(III) analogs have been used to address this challenge. The
isoelectronic relationship between Fe(II) and Co(III) ensures that they possess the same set of
ligand-field excited states, however the energetic order could be different, which is not known,
and thus one of the key goals of my research. Consequently, comprehending Co(III) photophysics
becomes a key element in unraveling the charge-transfer excited state decay of Fe(II)
chromophores, thereby paving the way towards the development of iron-based dye-sensitized
solar cells/photocatalysts. However, the photophysics of Co(III) complexes have not been
extensively explored, unlike their isoelectronic Fe(II) analogs. Therefore, my research aims to
conduct a comprehensive investigation into the excited state energetics and dynamics of Co(III)
polypyridyl complexes using time resolved laser spectroscopic techniques in the McCusker group
and through collaboration with multiple research groups with specific expertise, thus paving a way
for utilizing such chromophores across diverse applications.
References:
1. Chan, A. Y.;
†
Ghosh, A.;
†
Yarranton, J. T.; Twilton, J.; Jin, J.; Sakai, H. A.; Arias-Rotondo, D. M.; McCusker,
J. K.
*
and MacMillan, D. W. C.
*
Exploiting the Marcus inverted region as a design principle for first-row
transition metal-based photoredox catalysis. Science, 2023, 382, 191-197. [
†
equal contribution] (Link)
2. Alowakennu, M. M.;
†
Ghosh, A.;
†
McCusker, J. K.
*
Direct Evidence for Ligand Field-based Oxidative
Photoredox Chemistry of a Co(III) Photosensitizer. J. Am. Chem. Soc. 2023, 145, 20786-20791. [
†
equal
contribution] (Link)
If you have any questions regarding my project, please reach out to me: ghoshata@msu.edu
