title: How Does Peripheral Functionalization of Ruthenium(II)-Terpyridine Complexes Affect Spatial Charge Redistribution after Photoexcitation at the Franck-Condon Point?
abstract: Ruthenium polypyridine-type complexes are extensively used sensitizers to convert solar energy into chemical and/or electrical energy, and they can be tailored through their metal-to-ligand charge-transfer (MLCT) properties. Much work has been directed at harnessing the triplet MLCT state in photoinduced processes, from sophisticated molecular architectures to dye-sensitized solar cells. In dye-sensitized solar cells, strong coupling to the semiconductor exploits the high reactivity of the (hot) singlet/triplet MLCT state. In this work, we explore the nature of the (1) MLCT states of remotely substituted Ru(II) model complexes by both experimental and theoretical techniques. Two model complexes with electron-withdrawing (i.e. NO2 ) and electron-donating (i.e. NH2 ) groups were synthesized; these complexes contained a phenylene spacer to serve as a spectroscopic handle and to confirm the contribution of the remote substituent to the (1) MLCT transition. [Ru(tpy)2 ](2+) -based complexes (tpy=2,2':6',2''-terpyridine) were further desymmetrized by tert-butyl groups to yield unidirectional (1) MLCTs with large transition dipole moments, which are beneficial for related directional charge-transfer processes. Detailed comparison of experimental spectra (deconvoluted UV/Vis and resonance Raman spectroscopy data) with theoretical calculations based on density functional theory (including vibronic broadening) revealed different properties of the optically active bright (1) MLCT states already at the Franck-Condon point.
authors.affiliation: Institute for Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena (Germany).|SLAC National Accelerator Laboratory, Menlo Park, California 94309 (USA).
authors.forename: Julia
authors.initials: J
authors.lastname: Preiß
authors.affiliation: Institute for Organic and Macromolecular Chemistry, Friedrich Schiller University Jena, Jena Center for Soft Matter (JCSM), Humboldtstrasse 10, 07743 Jena (Germany).
authors.forename: Michael
authors.initials: M
authors.lastname: Jäger
authors.affiliation: Institute of Inorganic Chemistry I, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm (Germany).
authors.forename: Sven
authors.initials: S
authors.lastname: Rau
authors.affiliation: Institute for Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena (Germany).|Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Strasse 9, 07745 Jena (Germany).
authors.forename: Benjamin
authors.initials: B
authors.lastname: Dietzek
authors.affiliation: Institute for Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena (Germany).|Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Strasse 9, 07745 Jena (Germany).
authors.forename: Jürgen
authors.initials: J
authors.lastname: Popp
authors.affiliation: SLAC National Accelerator Laboratory, Menlo Park, California 94309 (USA).|Department of Chemistry and PULSE Institute, Stanford University, Stanford, California, 94305 (USA).
authors.forename: Todd
authors.initials: T
authors.lastname: Martínez
authors.affiliation: Institute for Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena (Germany).
authors.forename: Martin
authors.initials: M
authors.lastname: Presselt
keywords: charge transfer; density functional theory; dye-sensitized solar cells; photocatalysis; ruthenium