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Quantifying Entatic States in Photophysical Processes: Applications to Copper Photosensitizers

Stroscio, Gautam D. and Ribson, Ryan D. and Hadt, Ryan G. (2019) Quantifying Entatic States in Photophysical Processes: Applications to Copper Photosensitizers. Inorganic Chemistry, 58 (24). pp. 16800-16817. ISSN 0020-1669. doi:10.1021/acs.inorgchem.9b02976.

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The entatic or rack-induced state is a core concept in bioinorganic chemistry. In its simplest form, it is present when a protein scaffold places a transition metal ion and its first coordination sphere into an energized geometric and electronic structure that differs significantly from that of the relaxed form. This energized complex can exhibit special properties. Under this purview, however, entatic states are hardly unique to bioinorganic chemistry, and their effects can be found throughout a variety of important chemistries and materials science applications. Despite this broad influence, there are only a few examples where entatic effects have been quantified. Here we extend the entatic concept more generally to photophysical processes by developing a combined experimental and computational methodology to quantify entatic states across an entire class of functional molecules, e.g., Cu-based photosensitizers. These metal complexes have a broad range of applications, including solar electricity generation, solar fuels synthesis, organic light emitting diodes (OLEDs), and photoredox catalysis. As a direct consequence of quantifying entatic states, this methodology allows the disentanglement of steric and electronic contributions to excited state dynamics. Thus, before embarking on the syntheses of new Cu-based photosensitizers, the correlations described herein can be used as an estimate of entatic and electronic contributions and thus guide ligand design and the development of next-generation transition metal complexes with improved or tailored excited state dynamics. Lastly, entatic energies in some Cu photosensitizers are the largest yet quantified and are found here to approach 20 kcal/mol relative to the conformationally flexible [Cu(phen)₂]⁺. These energetics are significant relative to typical chemical driving forces and barriers, highlighting the utility in extending entatic state descriptors to new classes of molecules and materials with interesting functional properties involving the coupling between electron and vibrational dynamics.

Item Type:Article
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URLURL TypeDescription ItemConference Paper
Stroscio, Gautam D.0000-0002-0827-1062
Hadt, Ryan G.0000-0001-6026-1358
Additional Information:© 2019 American Chemical Society. Received: October 9, 2019; Published: November 26, 2019. We acknowledge Dr. Jay Winkler for assistance with low-temperature emission measurements and the Beckman Institute Laser Resource Center (BILRC) for access to equipment. We also thank Profs. Harry Gray, Lin Chen, and Dugan Hayes and Drs. Karen Mulfort, Lars Kohler, Martin Srnec, and Alec Follmer for helpful discussions. Financial support from Caltech and the Dow Next Generation Educator Fund is gratefully acknowledged. The authors declare no competing financial interest.
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Dow Next Generation Educator FundUNSPECIFIED
Issue or Number:24
Record Number:CaltechAUTHORS:20191126-105444590
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Official Citation:Quantifying Entatic States in Photophysical Processes: Applications to Copper Photosensitizers. Gautam D. Stroscio, Ryan D. Ribson, and Ryan G. Hadt. Inorganic Chemistry 2019 58 (24), 16800-16817. DOI: 10.1021/acs.inorgchem.9b02976
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100063
Deposited By: Tony Diaz
Deposited On:26 Nov 2019 19:46
Last Modified:16 Nov 2021 17:51

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