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Earth Abundant Photosensitizers

A specialization of the Castellano Group is our ability to develop and understand earth abundant transition metal photosensitizers and is made possible thanks to funding from the DoE-BES. The main goal of this research program is to explain the fundamental aspects of photosensitizer design and excited-state engineering. With this knowledge, development of metal-organic chromophores for an array of solar photochemistry applications can be expanded upon.

Long-Lived MLCT Excited States of Cu(I) bis(phenanthrolines)

Enhancing the MLCT excited states of Cu(I) diimine complexes has been pursued by our group for a decade. After excitation, these molecules undergo a flattening distortion as a result of the pseudo-Jahn–Teller effect, ultimately quenching their MLCT excited states. By prohibiting distortion, however, we have shown that lifetimes can be extended into the microsecond-regime. By designing a new generation of phenanthroline ligand, we continue to study unique effects on Cu(I) MLCT excited states.

Recent article: Next Generation Cuprous Phenanthroline MLCT Photosensitizer Featuring Cyclohexyl Substituents — Inorganic Chemistry

Zr(IV) LMCT photosensitizers undergoing TADF

In tandem with the Milsmann Group at West Virginia University, a series of Zr(IV) photosensitizers harnessing unique ligand design have been devised for use in photochemical upconversion. Our group focuses on understanding the complex photophysical phenomenon underlying these chromophores. Zr(IV) molecules exhibit long-lived LMCT lifetimes exceeding hundreds of microseconds due to thermally-activated delayed fluorescence (TADF). 

Recent article: Low power threshold photochemical upconversion using a zirconium(iv) LMCT photosensitizer — Chemical Science