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- Title
Branching mechanism of photoswitching in an Fe(II) polypyridyl complex explained by full singlet-triplet-quintet dynamics.
- Authors
Rozgonyi, Tamás; Vankó, György; Pápai, Mátyás
- Abstract
It has long been known that irradiation with visible light converts Fe(II) polypyridines from their low-spin (singlet) to high-spin (quintet) state, yet mechanistic interpretation of the photorelaxation remains controversial. Herein, we simulate the full singlet-triplet-quintet dynamics of the [Fe(terpy)2]2+ (terpy = 2,2':6',2"-terpyridine) complex in full dimension, in order to clarify the complex photodynamics. Importantly, we report a branching mechanism involving two sequential processes: a dominant 3MLCT→3MC(3T2g)→3MC(3T1g)→5MC, and a minor 3MLCT→3MC(3T2g)→5MC component. (MLCT = metal-to-ligand charge transfer, MC = metal-centered). While the direct 3MLCT→5MC mechanism is considered as a relevant alternative, we show that it could only be operative, and thus lead to competing pathways, in the absence of 3MC states. The quintet state is populated on the sub-picosecond timescale involving non-exponential dynamics and coherent Fe-N breathing oscillations. The results are in agreement with the available time-resolved experimental data on Fe(II) polypyridines, and fully describe the photorelaxation dynamics. The description of full singlet-triplet-quintet dynamics is challenging due to the need for simultaneous treatment of disparate spin states, as well as multidimensional dynamics. Here the authors report a branching mechanism for the Fe(II) polypyridine complex [Fe(terpy)2]2+ by full-dimensional simulation of singlet-triplet-quintet dynamics, showing that the quintet (5MC) state is populated on the sub-ps timescale by two sequential 3MLCT→3MC→5MC pathways involving the two 3MC components 3T1g and 3T2g.
- Subjects
CHARGE transfer; VISIBLE spectra; POLYPYRIDINES; BROWNIAN motion; QUINTETS
- Publication
Communications Chemistry, 2023, Vol 6, Issue 1, p1
- ISSN
2399-3669
- Publication type
Article
- DOI
10.1038/s42004-022-00796-z