Manipulating the Triplet Charge Transfer State Lifetime of Bis-indolyl-pyridine-based Ni(II) Complexes by Changing the Ancillary Ligand

Mathias, Vivienne Judith (2025) Manipulating the Triplet Charge Transfer State Lifetime of Bis-indolyl-pyridine-based Ni(II) Complexes by Changing the Ancillary Ligand. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Vivienne Judith Mathias (23MP015)) 23MP015_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

The development of earth-abundant, first-row transition metal complexes as sustainable alternatives to noble-metal-based photosensitizers is one of the main challenges of sustainable photochemistry. Herein, we investigate a bis-indolyl-pyridine (BIP) derived ligand scaffold coordinated to a Ni(II) centre to control and extend the lifetimes of triplet charge transfer (3CT) states—vital for photoinduced processes. By systematic tuning of ancillary ligands through electron-donating and electron-withdrawing groups as well as long conjugation involving pyrenyl, quinoline, and acridine units, we investigate the roles of electronics, resonance, and steric effects on the excited-state processes. Though efforts to achieve a triplet reservoir effect by chromophoric ligand conjugation were met with limited success due to structural non-planarity, resonance-extended ligands such as quinoline resulted in longer-lived excited states. The research emphasizes strategic ligand design as a method for fine-tuning photophysical properties of Ni(II) complexes and advances the general quest to replace rare 4d and 5d metals in photochemical applications.

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