Dynamics of Photoinduced Intramolecular and Intermolecular Electron Transfers in Ligand-Conjugated Ir(III)-Re(I) Photocatalysts

Soohwan Kim; Daehan Lee; Taesoo Kim; Chul Hoon Kim; Ho-Jin Son; Sang Ook Kang; Jae Yoon Shin

doi:10.1021/acs.jpclett.2c03367

Dynamics of Photoinduced Intramolecular and Intermolecular Electron Transfers in Ligand-Conjugated Ir(III)-Re(I) Photocatalysts

J Phys Chem Lett. 2023 Feb 16;14(6):1535-1541. doi: 10.1021/acs.jpclett.2c03367. Epub 2023 Feb 6.

Authors

Soohwan Kim¹, Daehan Lee¹, Taesoo Kim¹, Chul Hoon Kim¹, Ho-Jin Son¹, Sang Ook Kang¹, Jae Yoon Shin¹

Affiliation

¹ Department of Advanced Materials Chemistry, Korea University, Sejong 30019, Republic of Korea.

PMID: 36745190
DOI: 10.1021/acs.jpclett.2c03367

Abstract

We report the electron transfer (ET) dynamics in a series of Ir(III)-Re(I) photocatalysts where two bipyridyl ligands of Ir and Re moieties are conjugated at the meta (m)- or para (p)-position of each side. Femtosecond transient absorption (TA) measurements identify the intramolecular ET (IET) dynamics from the Ir to Re moiety, followed by the formation of one-electron-reduced species (OERS) via the intermolecular ET with a sacrificial electron donor (SED). The IET rate depends on the bridging ligand (BL) structures (∼25 ps for BL_mm/mp vs ∼68 ps for BL_pm/pp), while the OERS formation happens on an even slower time scale (∼1.4 ns). Connecting the Re moiety at the meta-position of the bipyridyl of the Ir moiety can restrict the rotation around a covalent bond between two bipyridyl ligands by steric hindrances and facilitate the IET process. This highlights the importance of BL structures on the ET dynamics in photocatalysts.