TY  - JOUR
A1  - Hoche, Joscha
A1  - Flock, Marco
A1  - Miao, Xincheng
A1  - Philipp, Luca Nils
A1  - Wenzel, Michael
A1  - Fischer, Ingo
A1  - Mitric, Roland
T1  - Excimer formation dynamics in the isolated tetracene dimer
JF  - Chemical Science
N2  - The understanding of excimer formation and its interplay with the singlet-correlated triplet pair state \(^{1}\)(TT) is of high significance for the development of efficient organic electronics. Here, we study the photoinduced dynamics of the tetracene dimer in the gas phase by time-resolved photoionisation and photoion imaging experiments as well as nonadiabatic dynamics simulations in order to obtain mechanistic insight into the excimer formation dynamics. The experiments are performed using a picosecond laser system for excitation into the S\(_{2}\) state and reveal a biexponential time dependence. The time constants, obtained as a function of excess energy, lie in the range between ≈10 ps and 100 ps and are assigned to the relaxation of the excimer on the S\(_{1}\) surface and to its deactivation to the ground state. Simulations of the quantum-classical photodynamics are carried out in the frame of the semi-empirical CISD and TD-lc-DFTB methods. Both theoretical approaches reveal a dominating relaxation pathway that is characterised by the formation of a perfectly stacked excimer. TD-lc-DFTB simulations have also uncovered a second relaxation channel into a less stable dimer conformation in the S\(_{1}\) state. Both methods have consistently shown that the electronic and geometric relaxation to the excimer state is completed in less than 10 ps. The inclusion of doubly excited states in the CISD dynamics and their diabatisation further allowed to observe a transient population of the \(^{1}\)(TT) state, which, however, gets depopulated on a timescale of 8 ps, leading finally to the trapping in the excimer minimum.
KW  - excimer formation
KW  - tetracene dimer
KW  - organic electronics
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-251559
VL  - 12
IS  - 36
SP  - 11965
EP  - 11975
ER  - 
TY  - JOUR
A1  - Bura, Thomas
A1  - Beaupré, Serge
A1  - Légaré, Marc-André
A1  - Ibraikulov, Olzhas A.
A1  - Leclerc, Nicolas
A1  - Leclerc, Mario
T1  - Theoretical calculations for highly selective Direct Heteroarylation Polymerization: new nitrile-substituted Dithienyl-Diketopyrrolopyrrole-based polymers
JF  - Molecules
N2  - Direct Heteroarylation Polymerization (DHAP) is becoming a valuable alternative to classical polymerization methods being used to synthesize π-conjugated polymers for organic electronics applications. In previous work, we showed that theoretical calculations on activation energy (Ea) of the C–H bonds were helpful to rationalize and predict the selectivity of the DHAP. For readers’ convenience, we have gathered in this work all our previous theoretical calculations on Ea and performed new ones. Those theoretical calculations cover now most of the widely utilized electron-rich and electron-poor moieties studied in organic electronics like dithienyl-diketopyrrolopyrrole (DT-DPP) derivatives. Theoretical calculations reported herein show strong modulation of the Ea of C–H bond on DT-DPP when a bromine atom or strong electron withdrawing groups (such as fluorine or nitrile) are added to the thienyl moiety. Based on those theoretical calculations, new cyanated dithienyl-diketopyrrolopyrrole (CNDT-DPP) monomers and copolymers were prepared by DHAP and their electro-optical properties were compared with their non-fluorinated and fluorinated analogues.
KW  - DHAP
KW  - selectivity
KW  - theoretical calculations
KW  - conjugated polymers
KW  - organic electronics
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197648
SN  - 1420-3049
VL  - 23
IS  - 9
ER  -