TY  - JOUR
A1  - Barak, Arvind
A1  - Dhiman, Nishant
A1  - Sturm, Floriane
A1  - Rauch, Florian
A1  - Lakshmanna, Yapamanu Adithya
A1  - Findlay, Karen S.
A1  - Beeby, Andrew
A1  - Marder, Todd B.
A1  - Umapathy, Siva
T1  - Excited‐State Intramolecular Charge‐Transfer Dynamics in 4‐Dimethylamino‐4′‐cyanodiphenylacetylene: An Ultrafast Raman Loss Spectroscopic Perspective
JF  - ChemPhotoChem
N2  - Photo‐initiated intramolecular charge transfer (ICT) processes play a pivotal role in the excited state reaction dynamics in donor‐bridge‐acceptor systems. The efficacy of such a process can be improved by modifying the extent of π‐conjugation, relative orientation/twists of the donor/acceptor entities and polarity of the environment. Herein, 4‐dimethylamino‐4′‐cyanodiphenylacetylene (DACN‐DPA), a typical donor‐π‐bridge‐acceptor system, was chosen to unravel the role of various internal coordinates that govern the extent of photo‐initiated ICT dynamics. Transient absorption (TA) spectra of DACN‐DPA in n‐hexane exhibit a lifetime of >2 ns indicating the formation of a triplet state while, in acetonitrile, a short time‐constant of ∼2 ps indicates the formation of charge transferred species. Ultrafast Raman loss spectroscopy (URLS) measurements show distinct temporal and spectral dynamics of Raman bands associated with C≡C and C=C stretching vibrations. The appearance of a new band at ∼1492 cm\(^{−1}\) in acetonitrile clearly indicates structural modification during the ultrafast ICT process. Furthermore, these observations are supported by TD‐DFT computations.
KW  - charge transfer
KW  - ultrafast Raman loss spectroscopy
KW  - 4-dimethylamino-4′-cyanodiphenylacetylene
KW  - transient absorption
KW  - TD-DFT
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312280
VL  - 6
IS  - 12
ER  - 
TY  - JOUR
A1  - Malý, Pavel
A1  - Brixner, Tobias
T1  - Fluorescence‐Detected Pump–Probe Spectroscopy
JF  - Angewandte Chemie International Edition
N2  - We introduce a new approach to transient spectroscopy, fluorescence‐detected pump–probe (F‐PP) spectroscopy, that overcomes several limitations of traditional PP. F‐PP suppresses excited‐state absorption, provides background‐free detection, removes artifacts resulting from pump–pulse scattering, from non‐resonant solvent response, or from coherent pulse overlap, and allows unique extraction of excited‐state dynamics under certain conditions. Despite incoherent detection, time resolution of F‐PP is given by the duration of the laser pulses, independent of the fluorescence lifetime. We describe the working principle of F‐PP and provide its theoretical description. Then we illustrate specific features of F‐PP by direct comparison with PP, theoretically and experimentally. For this purpose, we investigate, with both techniques, a molecular squaraine heterodimer, core–shell CdSe/ZnS quantum dots, and fluorescent protein mCherry. F‐PP is broadly applicable to chemical systems in various environments and in different spectral regimes.
KW  - femtochemistry
KW  - FL spectroscopy
KW  - time-resolved spectroscopy
KW  - transient absorption
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-244811
VL  - 60
IS  - 34
SP  - 18867
EP  - 18875
ER  - 
TY  - JOUR
A1  - Kar, Haridas
A1  - Gehrig, Dominik W.
A1  - Allampally, Naveen Kumar
A1  - Fernández, Gustavo
A1  - Laquai, Frédéric
A1  - Ghosh, Suhrit
T1  - Cooperative supramolecular polymerization of an amine-substituted naphthalene-diimide and its impact on excited state photophysical properties
JF  - Chemical Science
N2  - A donor-acceptor-donor (D-A-D) type naphthalene-diimide (NDI-H) chromophore exhibits highly cooperative J-aggregation leading to nanotubular self-assembly and gelation in n-decane, as demonstrated by UV/Vis, FT-IR, photoluminescence and microscopy studies. Analysis of temperature-dependent UV/Vis spectra using the nucleation-elongation model and FT-IR data reveals the molecular origin of the cooperative nature of the self-assembly. The supramolecular polymerization is initiated by H-bonding up to a degree of polymerization similar to 20-25, which in a subsequent elongation step promotes J-aggregation in orthogonal direction leading to possibly a sheet-like structure that eventually produces nanotubes. Time-resolved fluorescence and absorption measurements demonstrate that such a tubular assembly enables very effective delocalization of excited states resulting in a remarkably prolonged excited state lifetime.
KW  - nanotube
KW  - supramolecular polymerization
KW  - NDI-H
KW  - UV/Vis spectroscopy
KW  - FT-IR spectroscopy
KW  - transient absorption
KW  - nucleation-elongation model
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191459
VL  - 7
IS  - 2
ER  -