Ultrafast photo-induced charge transfer unveiled by two-dimensional electronic spectroscopy.
The interaction of exciton and charge transfer (CT) states plays a central role in photo-induced CT processes in chemistry, biology, and physics. In this work, we use a combination of two-dimensional electronic spectroscopy (2D-ES), pump-probe measurements, and quantum chemistry to investigate the ultrafast CT dynamics in a lutetium bisphthalocyanine dimer in different oxidation states. It is found that in the anionic form, the combination of strong CT-exciton interaction and electronic asymmetry induced by a counter-ion enables CT between the two macrocycles of the complex on a 30 fs timescale. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra, and we monitor how the excited state charge density ultimately localizes on the macrocycle closest to the counter-ion within 100 fs. A comparison with the dynamics in the radical species further elucidates how CT states modulate the electronic structure and tune fs-reaction dynamics. Our experiments demonstrate the unique capability of 2D-ES in combination with other methods to decipher ultrafast CT dynamics.
Faculty of Physics, University of Vienna, Strudlhofgasse 4, 1090 Vienna, Austria.
Oliver
O
Bixner
Vladimír
V
Lukeš
Tomáš
T
Mančal
Jürgen
J
Hauer
Franz
F
Milota
Michael
M
Fischer
Igor
I
Pugliesi
Maximilian
M
Bradler
Walther
W
Schmid
Eberhard
E
Riedle
Harald F
HF
Kauffmann
Niklas
N
Christensson
D019281:Dimerization; D004583:Electrons; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D008187:Lutetium / Q000737:chemistry*; D008958:Models, Molecular; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013997:Time Factors
D007211:Indoles; D054833:Isoindoles; D000644:Quaternary Ammonium Compounds; D008187:Lutetium; C009405:tetrabutylammonium; C013647:phthalocyanine