Details

Autor(en) / Beteiligte

• Ahrens, J
• Frank, M
• Clever, G. H
• Schwarzer, D

Titel

Ultrafast IR spectroscopy of photo-induced electron transfer in self-assembled donor-acceptor coordination cagesElectronic supplementary information (ESI) available. See DOI: 10.1039/c7cp02253k

Erscheinungsjahr

2017-05

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Photo-induced processes in self-assembled coordination cages were studied by femtosecond infrared pump-probe spectroscopy. Densely packed, interpenetrated double cages were constructed from eight bis-monodentate redoxactive ligands bound to four Pd( ii ) nodes. Two types of ligands consisting of electron rich phenothiazine (PTZ) or electron deficient anthraquinone (ANQ) chromophores were used to assemble either homo-octameric or mixed-ligand cages. Upon photoexcitation the homo-octameric acceptor cage undergoes intersystem crossing to a long-lived triplet state, similar to the free acceptor ligand. Excitation of the free donor ligand leads to a fluorescent state with intramolecular charge transfer character. This fluorescence is completely quenched in the homo-octameric donor double cage due to a ligand-to-metal charge transfer followed by back electron transfer on a ps timescale. Only for the mixed-ligand cage irradiation produces a charge separated state with an oxidized PTZ radical cation and a reduced ANQ radical anion as proven by their vibrational fingerprints in the transient IR spectra. In dichloromethane the lifetime of this charge separated state extends from tens of ps to >1.5 ns which is attributed to the broad distribution of mixed-ligand cages with different stoichiometry and/or stereo configurations. Photo-excitation of self-assembled palladium based coordination cages consisting of phenothiazine electron donor and anthraquinone electron acceptor ligands produce charge separated states with lifetimes of up to 1.5 ns.