Effects of Heteroatoms of Tetracene and Pentacene Derivatives on Their Stability and Singlet Fission

Abstract

The effects of the introduction of an sp(2)-hybridized nitrogen atom (═N-) and thiophene ring on the structure geometries, frontier molecular orbital energies, and excited state energies related to singlet fission (SF) for some tetracene and pentacene derivatives were theoretically investigated by quantum chemical methods. The introduction of a nitrogen atom significantly decreases the energies of frontier molecular orbitals and hence improves their stabilities in air and light illumination. More importantly, it is helpful for reducing the energy loss of the exothermic singlet fission of pentacene derivatives. For fused benzene-thiophene structures, the (α, β) connection pattern could stabilize the frontier molecular orbitals, while the (β, β) connection pattern can promote the thermodynamic driving force of singlet fission. These facts provide a theoretical ground for rational design of SF materials.

Tuning of the stability and energy levels of singlet exciton fission relevant excited states of pentacenes by site-specific substitution

“…For most of the electron withdrawing groups, the central-substitutions (at ␣ and ␤ positions) lead to relatively larger decrease on the FMO energies than those of end-substitutions (at ␥ and ␦) due to the relatively larger electron densities at these central positions. Contrarily, the end positions are less sensitive to the electronic inductive effect than the central positions due to their small electron densities, which corresponds well with the results of our previous work on nitrogen hybridized pentacene derivatives [32].…”

“…The frontier molecular orbital (FMO) energies were obtained after ground state geometry optimization. Our previous work indicates that enlargement of basis set size did not bring obvious improvement on the accuracy of HOMO and LUMO energies and the overall HOMO/LUMO gaps [32], so the double-quality AO basis set, 6-31G**, is selected for calculating the FMO energies. The reliability of these calculations have been proved by the fact that the calculated HOMO/LUMO gap for pentacene (2.21 eV) is consistent with the experimental values (2.15 eV) [16].…”

Exact wave packet dynamics of singlet fission in unsubstituted and substituted polyene chains within long-range interacting models

“…Thus we find that even in substituted polyenes, if the initial state is an S 1 state rather than other higher energy singlet state, SF is efficient. This agrees with some recent studies which suggest substitution by heteroatoms within organic chromophore 16,39,40 or copolymerising donor-acceptor moieties [41][42][43] can play an important role in tailoring candidate molecules for SF. The mixing of different eigenstates on donor-acceptor substitution, although well-known in π-conjugated carbon systems, its significance in singlet fission has not been explored.…”

Synthesis, computational, and photophysical characterization of diaza-embedded [4]helicenes and pseudo[4]helicenes and their pyridinium and viologen homologues

“…11 This observation is potentially important because of the role that  ST plays in diverse phenomenon such as triplettriplet annihilation, 42 intersystem crossing, 43 delayed fluorescence, 44 and singlet fission. [45][46][47] These processes play critical roles in many optoelectronic applications and as a consequence considerable effort has been devoted to controlling the size of  ST.…”