Research output: Contribution to journal › Article › peer-review
Giant magnetic field effects in donor-acceptor triads : On the charge separation and recombination dynamics in triarylamine-naphthalenediimide triads with bis-diyprrinato-palladium(II), porphodimethenato-palladium(II), and palladium(II)-porphyrin photosensitizers. / Riese, Stefan; Brand, Jessica S.; Mims, David et al.
In: Journal of Chemical Physics, Vol. 153, No. 5, 054306, 07.08.2020.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Giant magnetic field effects in donor-acceptor triads
T2 - On the charge separation and recombination dynamics in triarylamine-naphthalenediimide triads with bis-diyprrinato-palladium(II), porphodimethenato-palladium(II), and palladium(II)-porphyrin photosensitizers
AU - Riese, Stefan
AU - Brand, Jessica S.
AU - Mims, David
AU - Holzapfel, Marco
AU - Lukzen, Nikita N.
AU - Steiner, Ulrich E.
AU - Lambert, Christoph
PY - 2020/8/7
Y1 - 2020/8/7
N2 - A series of triads consisting of a triarylamine donor, a naphthalenediimide acceptor, and a palladium photosensitizer bridge was investigated for the photoinduced electron transfer processes and the spin chemistry involved. In this series, the ligand in the palladium photosensitizer was varied from bis-dipyrrinato to porphodimethenato and to a porphyrin. With the porphyrin photosensitizer, no charge separated state could be reached. This is caused by the direct relaxation of the excited photosensitizer to the ground state by intersystem crossing. The bis-dipyrrinato-palladium photosensitizer gave only a little yield (7%) of the charge separated state, which is due to the population of a metal centered triplet state and a concomitant geometrical rearrangement to a disphenoidal coordination sphere. This state relaxes rapidly to the ground state. In contrast, in the porphodimethenato-palladium triads, a long lived (μs to ms) charge separated state could be generated in high quantum yields (66%-74%) because, here, the population of a triplet metal centered state is inhibited by geometrical constraints. The magnetic field dependent transient absorption measurement of one of the porphodimethenato triads revealed a giant magnetic field effect by a factor of 26 on the signal amplitude of the charge separated state. This is the consequence of a magnetic field dependent triplet-singlet interconversion that inhibits the fast decay of the charge separated triplet state through the singlet recombination channel. A systematic comparative analysis of the spin-dependent kinetics in terms of three classical and one fully quantum theoretical methods is provided, shedding light on the pros and cons of each of them.
AB - A series of triads consisting of a triarylamine donor, a naphthalenediimide acceptor, and a palladium photosensitizer bridge was investigated for the photoinduced electron transfer processes and the spin chemistry involved. In this series, the ligand in the palladium photosensitizer was varied from bis-dipyrrinato to porphodimethenato and to a porphyrin. With the porphyrin photosensitizer, no charge separated state could be reached. This is caused by the direct relaxation of the excited photosensitizer to the ground state by intersystem crossing. The bis-dipyrrinato-palladium photosensitizer gave only a little yield (7%) of the charge separated state, which is due to the population of a metal centered triplet state and a concomitant geometrical rearrangement to a disphenoidal coordination sphere. This state relaxes rapidly to the ground state. In contrast, in the porphodimethenato-palladium triads, a long lived (μs to ms) charge separated state could be generated in high quantum yields (66%-74%) because, here, the population of a triplet metal centered state is inhibited by geometrical constraints. The magnetic field dependent transient absorption measurement of one of the porphodimethenato triads revealed a giant magnetic field effect by a factor of 26 on the signal amplitude of the charge separated state. This is the consequence of a magnetic field dependent triplet-singlet interconversion that inhibits the fast decay of the charge separated triplet state through the singlet recombination channel. A systematic comparative analysis of the spin-dependent kinetics in terms of three classical and one fully quantum theoretical methods is provided, shedding light on the pros and cons of each of them.
KW - PHOTOINDUCED ELECTRON-TRANSFER
KW - RADICAL RECOMBINATION
KW - STATES
KW - PAIR
KW - RELAXATION
KW - COMPLEXES
KW - PHOTOCHEMISTRY
KW - SPECTROSCOPY
KW - PALLADIUM
KW - COHERENT
UR - http://www.scopus.com/inward/record.url?scp=85089261833&partnerID=8YFLogxK
U2 - 10.1063/5.0013941
DO - 10.1063/5.0013941
M3 - Article
C2 - 32770922
AN - SCOPUS:85089261833
VL - 153
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 5
M1 - 054306
ER -
ID: 24962938