Events

Steric and Electronic Influence of Excited State Decay in Cu(I) MLCT Chromophores

Presented by Prof. Phil Castellano
Hosted by Prof. Jon Owen

Abstract:
Since 2013, we have continuously developed new classes of visible-light absorbing Cu^I MLCT-based 1,10-phenanthroline-containing photosensitizers to facilitate excited state chemistry. Our initial work leveraged ligand structural motifs featuring cooperative steric influence that ultimately achieved an unprecedented excited state lifetime in homoleptic Cu(I) MLCT complexes, realizing a seven-fold increase relative to its predecessor.¹ This led to a thorough investigation of their ultrafast dynamics, which were shown to inform the resultant photophysical properties and vice versa.² Computationally assisted molecular designs generated chromophores with cooperative steric influence to maintain long excited state lifetimes, with charge transfer bands featuring markedly enhanced visible light absorption properties.³ Exploiting combinations of cooperative steric influence and inductive electronic effects within the ligand structures ultimately achieved three record-setting excited state lifetimes and photoluminescence quantum yields in Cu(I) bis(phenanthrolines) with variable excited state redox properties.⁴ Adopting the lessons learned from a decade of research in Cu(I) homoleptics, heteroleptic Cu^I-based photosensitizers have been designed using the HETPHEN strategy to promote panchromatic light absorption5 and to independently possess excited state lifetimes suitable for engaging in bimolecular excited state reactions (hundreds of nanoseconds) while exhibiting measurable photoluminescence emission at room temperature. Our research in this area has recently been summarized.⁶

Read more about the Castellano Research Group here
 

References:

(1) McCusker, C. E.; Castellano, F. N. Design of a Long-Lifetime, Earth-Abundant, Aqueous Compatible Cu(I)
Photosensitizer Using Cooperative Steric Effects. Inorg. Chem. 2013, 52 (14), 8114-8120. DOI: 10.1021/ic401213p.

(2) Garakyaraghi, S.; Danilov, E. O.; McCusker, C. E.; Castellano, F. N. Transient Absorption Dynamics of
Sterically Congested Cu(I) MLCT Excited States. J. Phys. Chem. A 2015, 119 (13), 3181-3193. DOI: 10.1021/acs.jpca.5b00901.

(3) Garakyaraghi, S.; McCusker, C. E.; Khan, S.; Koutnik, P.; Bui, A. T.; Castellano, F. N. Enhancing the Visible-
Light Absorption and Excited-State Properties of Cu(I) MLCT Excited States. Inorg. Chem. 2018, 57 (4), 2296-2307. DOI: 10.1021/acs.inorgchem.7b03169.

(4) Rosko, M. C.; Espinoza, E. M.; Arteta, S.; Kromer, S.; Wheeler, J. P.; Castellano, F. N. Employing Long-Range Inductive Effects to Modulate Metal-to-Ligand Charge Transfer Photoluminescence in Homoleptic Cu(I) Complexes. Inorg. Chem. 2023, 62 (7), 3248-3259. DOI: 10.1021/acs.inorgchem.2c04315.

(5) Rosko, M. C.; Wheeler, J. P.; Alameh, R.; Faulkner, A. P.; Durand, N.; Castellano, F. N. Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines. Inorg. Chem. 2024, 63 (3), 1692-1701. DOI: 10.1021/acs.inorgchem.3c04024.

(6) Steric and Electronic Influence of Excited-State Decay in Cu(I) Chromophores. Castellano, F.N., Rosko, M.C. Acc. Chem. Res. 2024, 57, 2872-2886. DOI: 10.1021/acs.accounts.4c00476.