Research Projects

This proposal aims to use ultrafast transient spectro-electrochemistry to explore the excited-state dynamics of a series of photoredox organic molecules and their corresponding radical ions. Triphenylamine (TPA) derivatives and their radical ions will be used as model systems in this study because of their exceptional redox properties, ease of structural modification, and spectral tunability to NIR. Upon oxidation, TPAs form stable radical cations (TPA•⁺), which are central to their performance in charge transfer processes, with profound potential applications in organic electronics, photoredox catalysis, electrochromic materials, and artificial photosynthesis. Several leading research groups across the globe, including India, have contributed significantly to the study of such molecular systems. While steady-state and time-resolved spectroscopy have provided insights into these systems, ultrafast excited-state dynamics under electrochemical control for monitoring redox-state-resolved dynamics remain largely unexplored. The research aims to bridge this gap by leveraging femtosecond transient absorption spectroscopy (fs-TAS) coupled with electrochemical control, enabling real-time observation of excited-state processes of in situ generated radical species. The goal of this study is to investigate how oxidation state and molecular structure influence the excited-state pathways of TPA systems. The project proposes to synthesize three classes of TPA-based molecular systems: • Functionalized monomeric TPAs • Donor-acceptor (push-pull) TPA cascades • Multi-branched and bimetallic TPAs The photophysical and redox properties of these molecules will be studied using: • Steady-state UV-Vis-NIR absorption and fluorescence spectroscopy to understand redox-dependent spectral behaviour. • Femtosecond TAS (covering 350–1350 nm probe range) to study relaxation pathways, charge separation, and recombination kinetics • Electrochemical methods to correlate redox potential with photophysics using spectroelectrochemistry • Quantum chemical calculations (DFT/TD-DFT) to interpret excited-state behavior and structure-function correlations • Time-tagged transient spectro-electrochemistry setup that synchronizes potential steps with fs-TAS using time-triggered potentiostats, allowing precise temporal alignment between photoexcitation and electrochemical transformation A proof-of-concept study on a modified Lehn-type catalyst validated our ability to perform TAS under a controlled potential without time tagging. We established the formation of a new electrochemically generated species that is otherwise not identifiable using traditional methods. The current project aims to extend this approach with temporal control between the applied potential and TAS. Expected outcome and impacts of this study include: • Deciphering electron transfer mechanisms and excited-state lifetimes in redox-active systems. • Developing structure-function correspondence for a rational design of high-efficiency optoelectronic and photocatalytic materials. • Establishing TSEC as a general platform for real-time investigation of photo-responsive systems. • Supporting national initiatives, such as the India Semiconductor Mission and the National Solar Mission. The project is proposed to span 3 years, involving equipment procurement, synthesis, measurements, analysis, and dissemination through peer-reviewed publications, international conferences, and patents. Long-term, it aims to enable the design of novel molecular systems for sustainable energy and electronic applications. If given an opportunity, the research will be extended to develop electrodes for practical device applications