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Designing of chromophores that can harvest light for sensitization of effective photochemical reactions is a topic of contemporary research.1 Most prominent examples are the functions of natural photosystems I and II. Although we are far away toward constructing artificial leaf, it has been realized that rational design of molecular architectures is crucial to achieve complex functions.1 To this end, we designed a series of Ru(II) and Os(II) complexes by utilizing various polypyridine ligands functionalized with substituted imidazole moieties.2-8 These complexes are of interest because they possess achiral linear rod-like structures, can absorb a significant portion of the visible spectrum, have relatively long-lived excited states, usually stable following one-electron oxidation and reduction, and exhibit good photochemical stability. Extensive photophysical and electrochemical studies have been carried out to evaluate their efficacies for migration of charge–transfer energies in the excited state. DFT and TD-DFT computation were also performed to examine the electronic structures of the complexes and for the assignment of their optical spectral bands. Due to the presence of acidic imidazole NH protons, the complexes can interact with selective anions and thereby can act as receptors for anions. Moreover, by taking advantage of vacant coordination site(s) in the secondary coordination sphere, they can be utilized for recognition of selective cationic guests. The focus of the talk is to address the design of some multichromophoric complexes of Ru(II) and Os(II) based on polypyridyl-imidazole ligands and then to explore the switching of their photophysical behaviors for the designing of suitable functional materials. |