TY  - JOUR
A1  - Hong, Yongseok
A1  - Kim, Woojae
A1  - Kim, Taeyeon
A1  - Kaufmann, Christina
A1  - Kim, Hyungjun
A1  - Würthner, Frank
A1  - Kim, Dongho
T1  - Real-time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda-dimer by Ultrafast Time-Domain Raman Spectroscopy
JF  - Angewandte Chemie International Edition
N2  - In π-conjugated organic photovoltaic materials, an excimer state has been generally regarded as a trap state which hinders efficient excitation energy transport. But despite wide investigations of the excimer for overcoming the undesirable energy loss, the understanding of the relationship between the structure of the excimer in stacked organic compounds and its properties remains elusive. Here, we present the landscape of structural dynamics from the excimer formation to its relaxation in a co-facially stacked archetypical perylene bisimide folda-dimer using ultrafast time-domain Raman spectroscopy. We directly captured vibrational snapshots illustrating the ultrafast structural evolution triggering the excimer formation along the interchromophore coordinate on the complex excited-state potential surfaces and following evolution into a relaxed excimer state. Not only does this work showcase the ultrafast structural dynamics necessary for the excimer formation and control of excimer characteristics but also provides important criteria for designing the π-conjugated organic molecules.
KW  - excimer
KW  - vibrational coherence
KW  - time-resolved impulsive stimulated raman spectroscopy
KW  - structural dynamics
KW  - perylene bisimide
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318788
VL  - 61
IS  - 13
ER  - 
TY  - JOUR
A1  - Stolte, Matthias
A1  - Hecht, Reinhard
A1  - Xie, Zengqi
A1  - Liu, Linlin
A1  - Kaufmann, Christina
A1  - Kudzus, Astrid
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - Crystal Engineering of 1D Exciton Systems Composed of Single‐ and Double‐Stranded Perylene Bisimide J‐Aggregates
JF  - Advanced Optical Materials
N2  - Single crystals of three at bay area tetraphenoxy‐substituted perylene bisimide dyes are grown by vacuum sublimation. X‐ray analysis reveals the self‐assembly of these highly twisted perylene bisimides (PBIs) in the solid state via imide–imide hydrogen bonding into hydrogen‐bonded PBI chains. The crystallographic insights disclose that the conformation and sterical congestion imparted by the phenoxy substituents can be controlled by ortho‐substituents. Accordingly, whilst sterically less demanding methyl and isopropyl substituents afford double‐stranded PBI chains of complementary P and M atropo‐enantiomers, single hydrogen‐bonded chains of homochiral PBIs are observed for the sterically more demanding ortho‐phenyl substituents. Investigation of the absorption and fluorescence properties of microcrystals and thin films of these PBIs allow for an unambiguous interpretation of these exciton systems. Thus, the J‐aggregates of the double‐stranded crystals exhibit a much larger (negative) exciton coupling than the single‐stranded one, which in contrast has the higher solid‐state fluorescence quantum yield.
KW  - fluorescence
KW  - J‐aggregates
KW  - perylene bisimides
KW  - reabsorption
KW  - single crystal structure
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218221
VL  - 8
IS  - 18
ER  -