A Photoinduced Mixed Valence Photoswitch

COTIC, AGUSTINA; ELIAS, BENJAMIN; SLEP, LEONARDO DANIEL; ALEJANDRO CADRANEL; CERFONTAINE, SIMON; TROIAN-GAUTIER, LUDOVIC

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2022 vol. 24 p. 15121 - 15128

1463-9076

The ground state and photoinduced mixed valence states (GSMV and PIMV, respectively) of a dinuclear (Dp4+) ruthenium(II) complex bearing 2,2?-bipyridine ancillary ligands and a 2,2´:4´,4´´:2´´,2´´´-quaterpyridine (Lp) bridging ligand were investigated using femtosecond and nanosecond transient absorption spectroscopy, electrochemistry and density functional theory. It was shown that the electronic coupling between the transiently light-generated Ru(II) and Ru(III) centers is HDA ~ 450 cm?1 in the PIMV state, whereas the electrochemically generated GSMV state showed HDA ~ 0 cm?1, despite virtually identical Ru-Ru distances. This stemmed from the changes in dihedral angles between the two bpy moieties of Lp, estimated at 30° and 4° for the GSMV and PIMV states, respectively, consistent with a through-bond rather than a through-space mechanism. Electronic coupling can be turned on by using visible light excitation, making Dp4+ a competitive candidate for photoswitching applications. A novel strategy to design photoinduced charge transfer molecular switches is proposed.