TY  - JOUR
A1  - Wu, Zhu
A1  - Roldao, Juan Carlos
A1  - Rauch, Florian
A1  - Friedrich, Alexandra
A1  - Ferger, Matthias
A1  - Würthner, Frank
A1  - Gierschner, Johannes
A1  - Marder, Todd B.
T1  - Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP)
JF  - Angewandte Chemie
N2  - Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)\(_{3}\) does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.
KW  - boric acid
KW  - room-temperature phosphorescence (RTP)
KW  - optical materials
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318308
VL  - 61
IS  - 15
ER  - 
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  - Ferger, Matthias
A1  - Roger, Chantal
A1  - Köster, Eva
A1  - Rauch, Florian
A1  - Lorenzen, Sabine
A1  - Krummenacher, Ivo
A1  - Friedrich, Alexandra
A1  - Košćak, Marta
A1  - Nestić, Davor
A1  - Braunschweig, Holger
A1  - Lambert, Christoph
A1  - Piantanida, Ivo
A1  - Marder, Todd B.
T1  - Electron‐Rich EDOT Linkers in Tetracationic bis‐Triarylborane Chromophores: Influence on Water Stability, Biomacromolecule Sensing, and Photoinduced Cytotoxicity
JF  - Chemistry – A European Journal
N2  - Three novel tetracationic bis‐triarylboranes with 3,4‐ethylenedioxythiophene (EDOT) linkers, and their neutral precursors, showed significant red‐shifted absorption and emission compared to their thiophene‐containing analogues, with one of the EDOT‐derivatives emitting in the NIR region. Only the EDOT‐linked trixylylborane tetracation was stable in aqueous solution, indicating that direct attachment of a thiophene or even 3‐methylthiophene to the boron atom is insufficient to provide hydrolytic stability in aqueous solution. Further comparative analysis of the EDOT‐linked trixylylborane tetracation and its bis‐thiophene analogue revealed efficient photo‐induced singlet oxygen production, with the consequent biological implications. Thus, both analogues bind strongly to ds‐DNA and BSA, very efficiently enter living human cells, accumulate in several different cytoplasmic organelles with no toxic effect but, under intense visible light irradiation, they exhibit almost instantaneous and very strong cytotoxic effects, presumably attributed to singlet oxygen production. Thus, both compounds are intriguing theranostic agents, whose intracellular and probably intra‐tissue location can be monitored by strong fluorescence, allowing switching on of the strong bioactivity by well‐focused visible light.
KW  - boranes
KW  - DNA/RNA sensors
KW  - fluorescent probes
KW  - singlet oxygen
KW  - theranostics
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287241
VL  - 28
IS  - 48
ER  -