TY  - JOUR
A1  - Belaidi, Houmam
A1  - Rauch, Florian
A1  - Zhang, Zuolun
A1  - Latouche, Camille
A1  - Boucekkine, Abdou
A1  - Marder, Todd B.
A1  - Halet, Jean-Francois
T1  - Insights into the optical properties of triarylboranes with strongly electron-accepting bis(fluoromesityl)boryl groups: when theory meets experiment
JF  - ChemPhotoChem
N2  - The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4-D-C\(_6\)H\(_4\)-B(Ar)\(_2\) (D=\(^t\)Bu or NPh\(_2\); Ar=mesityl (Mes) or 2,4,6-tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state-of-the-art DFT and TD-DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4-\(^t\)Bu-C\(_6\)H\(_4\)-B(Fmes)\(_2\) 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert-butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.
KW  - boron
KW  - density functional calculations
KW  - luminescence
KW  - phosphorescence
KW  - photophysics
KW  - activated delayes flourescence
KW  - 3-coordinate organoboron compounds
KW  - light-emitting-diodes
KW  - phosphorescene spectra
KW  - molecular structures
KW  - high efficiency
KW  - pi-conjugation
KW  - trivalent boron
KW  - single photon
KW  - donor
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-205600
VL  - 4
IS  - 3
ER  - 
TY  - JOUR
A1  - Sun, Meng‐Jia
A1  - Anhalt, Olga
A1  - Sárosi, Menyhárt B.
A1  - Stolte, Matthias
A1  - Würthner, Frank
T1  - Activating Organic Phosphorescence via Heavy Metal–π Interaction Induced Intersystem Crossing
JF  - Advanced Materials
N2  - Heavy‐atom‐containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface‐bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid‐state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)\(_{2}\)) as a triplet sensitizer and electron‐deficient 1,4,5,8‐naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room‐temperature phosphorescence confined in the low‐lying, long‐lived triplet state of NDIs with photoluminescence (PL) quantum yield (Φ\(_{PL}\)) exceeding 25% and a phosphorescence lifetime (τ\(_{Ph}\)) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin–orbital coupling between the constituents.
KW  - cocrystallization
KW  - naphthalene diimide
KW  - phosphorescence
KW  - platinum complexes
KW  - triplet sensitization
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312248
VL  - 34
IS  - 51
ER  - 
TY  - JOUR
A1  - Weissenseel, Sebastian
A1  - Gottscholl, Andreas
A1  - Bönnighausen, Rebecca
A1  - Dyakonov, Vladimir
A1  - Sperlich, Andreas
T1  - Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes
JF  - Science Advances
N2  - Spin-spin interactions in organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) are pivotal because radiative recombination is largely determined by triplet-to-singlet conversion, also called reverse intersystem crossing (RISC). To explore the underlying process, we apply a spin-resonance spectral hole-burning technique to probe electroluminescence. We find that the triplet exciplex states in OLEDs are highly spin-polarized and show that these states can be decoupled from the heterogeneous nuclear environment as a source of spin dephasing and can even be coherently manipulated on a spin-spin relaxation time scale T-2* of 30 ns. Crucially, we obtain the characteristic triplet exciplex spin-lattice relaxation time T-1 in the range of 50 mu s, which far exceeds the RISC time. We conclude that slow spin relaxation rather than RISC is an efficiency-limiting step for intermolecular donor:acceptor systems. Finding TADF emitters with faster spin relaxation will benefit this type of TADF OLEDs.
KW  - detected magnetic-resonance
KW  - population oscillations
KW  - polaron delocalization
KW  - charge separation
KW  - hole
KW  - phosphorescence
KW  - singlet
KW  - absorption
KW  - tryptophan
KW  - emission
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265508
VL  - 7
IS  - 47
ER  - 
TY  - JOUR
A1  - Wu, Zhu
A1  - Dinkelbach, Fabian
A1  - Kerner, Florian
A1  - Friedrich, Alexandra
A1  - Ji, Lei
A1  - Stepanenko, Vladimir
A1  - Würthner, Frank
A1  - Marian, Christel M.
A1  - Marder, Todd B.
T1  - Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature
JF  - Chemistry—A European Journal
N2  - Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T\(^M_1\) state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T\(^A_1\) state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.
KW  - AIE
KW  - luminescence
KW  - phosphorescence
KW  - triarylborane
KW  - triplet
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318297
VL  - 28
IS  - 30
ER  -