The
impact of the electronic structure of a series of 4H-imidazolate ligands in neutral, heteroleptic Cu(I) complexes
is investigated. Remarkable broad and strong ligand-dependent absorption
in the visible range of the electromagnetic spectrum renders the studied
complexes promising photosensitizers for photocatalytic applications.
The electronic structure of the Cu(I) complexes and the localization
of photoexcited states in the Franck–Condon region are unraveled
by means of UV–vis absorption and resonance Raman (rR) spectroscopy
supported by time-dependent density functional theory (TD-DFT) calculations.
The visible absorption bands stem from a superposition of bright metal-to-ligand
charge-transfer (MLCT) and π–π* as well as weakly
absorbing MLCT states. Additionally, the analysis of involved molecular
orbitals and rR spectra upon excitation of MLCT and π–π*
states highlights the impact of the electronic structure of the 4H-imidazolate ligands on the properties of the corresponding
Cu(I) complexes to avail a toolbox for predictive studies and efficient
complex design.
Quantum chemical methods have been utilised to explore the kinetics and thermodynamics of a prominent charge recombination pathway in a series of Ru II based molecular photocatalysts. Selective tuning of the Ru II coordination sphere, replacing the tbbpy ligands of the hydrogen evolving parent photocatalyst with electron rich, biimidazole based ligands, promotes unidirectional charge transfer towards the bridging ligand during initial photoexcitation. These electronic effects are also significant in the triplet manifold, where the predicted rate of the undesired deactivation process from the 3 MLCT state on the bridging ligand to a 3 MC state on the ruthenium centre, is decreased relative to the parent complex, by 1-2 orders of magnitude, alongside a decrease in electronic coupling. This design methodology could be utilised to promote targeted (light-driven) electron transfer pathways, as well as to potentially reduce 3 MC deactivation pathways in commonly used polypyridyl-based Ru II photocentres, thus enhancing the quantum efficiency of light driven catalysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.