Paper
Journal of Materials Chemistry C
been shown to reduce the dynamic rocking of chromophores
necessary for rISC, hence resulting in room temperature
phosphorescence.
5 C. Adachi, Jpn. J. Appl. Phys., 2014, 53, 60101.
6 Y. Tao, K. Yuan, T. Chen, P. Xu, H. Li, R. Chen, C. Zheng,
L. Zhang and W. Huang, Adv. Mater., 2014, 26, 7931–7958.
5
7
7
8
9
M. Y. Wong and E. Zysman-Colman, Adv. Mater., 2017, 29,
605444.
Q. Zhang, B. Li, S. Huang, H. Nomura, H. Tanaka and
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E. Spuling, N. Sharma, I. D. W. Samuel, E. Zysman-Colman
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1
Conclusions
Detailed DFT calculations have been used to unravel the initially
perplexing photophysics of three DMAC–BZN positional isomers.
The D–A bond dihedral angles – often the critical factor in similar
studies – are found to be much more alike than expected due to
the inward pointing DMAC C–H bonds capturing the plane of the
BZN acceptor ring. TD-DFT was f-state properties of the structural
isomers beyond qualitative comparisons, while use of the Tamm–
Dancoff approximation led to much more accurate results.
With identical D–A dihedral environments, the large differ-
ences between meta- and para-isomers are instead attributed to
different bond lengths and acceptor strengths associated with
resonance and inductive effects in the BZN p-system. The para-
and ortho-isomers are likely similar in acceptor strength, but an
additional intramolecular dipole interaction further restricts
ortho-D–A dihedral angle rotation, and results in improved
performance. We also identify D–A bond length relaxation
as an important factor in TADF performance, alongside D–A
dihedral motion.
1
1
0 Y. Gao, Q.-Q. Pan, L. Zhao, Y. Geng, T. Su, T. Gao and
Z.-M. Su, Chem. Phys. Lett., 2018, 701, 98–102.
1 K.-L. Woon, C.-L. Yi, K.-C. Pan, M. K. Etherington, C.-C. Wu,
K.-T. Wong and A. P. Monkman, J. Phys. Chem. C, 2019, 123,
12400–12410.
1
1
1
2 X. Wang, S. Wang, J. Lv, S. Shao, L. Wang, X. Jing and
F. Wang, Chem. Sci., 2019, 10, 2915–2923.
3 J. Gibson, A. P. Monkman and T. J. Penfold, ChemPhysChem,
2016, 17, 2956–2961.
4 C. Chen, R. Huang, A. S. Batsanov, P. Pander, Y.-T. Hsu,
Z. Chi, F. B. Dias and M. R. Bryce, Angew. Chem., 2018, 130,
16645–16649.
1
1
5 M. K. Etherington, F. Franchello, J. Gibson, T. Northey,
J. Santos, J. S. Ward, H. F. Higginbotham, P. Data,
A. Kurowska, P. Lays, D. Santos, D. R. Graves, A. S.
Batsanov, F. B. Dias, M. R. Bryce, T. J. Penfold and
A. P. Monkman, Nat. Commun., 2017, 8, 14987.
6 R. Huang, J. S. Ward, N. A. Kukhta, J. Av o´ , J. Gibson,
T. Penfold, J. C. Lima, A. S. Batsanov, M. N. Berberan-
Santos, M. R. Bryce and F. B. Dias, J. Mater. Chem. C,
Finally, we identify an interesting and useful example of an
attractive intramolecular dipole interaction that can be used to
control dihedral angles by trapping at favourable angles instead
of repelling from unfavourable ones. These kinds of dihedral
control open new horizons in TADF rational design.
2018, 6, 9238–9247.
1
1
7 C. S. Oh, D. de, S. Pereira, S. H. Han, H.-J. Park, H. F.
Higginbotham, A. P. Monkman and J. Y. Lee, ACS Appl.
Mater. Interfaces, 2018, 10, 35420–35429.
8 H. F. Higginbotham, C.-L. Yi, A. P. Monkman and K.-T.
Wong, J. Phys. Chem. C, 2018, 122, 7627–7634.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
19 M. K. Etherington, N. A. Kukhta, H. F. Higginbotham,
A. Danos, A. N. Bismillah, D. R. Graves, P. R. McGonigal,
N. Haase, A. Morherr, A. S. Batsanov, C. Pflumm, V. Bhalla,
M. R. Bryce and A. P. Monkman, J. Phys. Chem. C, 2019, 123,
NAK, HFH, MKE, and APM acknowledge the EU’s Horizon 2020
for funding the PHEBE project under grant no. 641725. NAK,
MKE, AD, NH and APM acknowledge the EU’s Horizon 2020
for funding the HyperOLED project under grant no. 641725.
APM thanks EPSRC grant EP/L02621X/1 for funding. ANB
acknowledges an EPSRC Doctoral Training Grant. TOC image
elements adapted from ref. 58, under Creative Commons BY 3.0
1
1109–11117.
0 C. S. Oh, H. L. Lee, S. H. Han and J. Y. Lee, Chem. – Eur. J.,
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1 N. A. Kukhta, A. S. Batsanov, M. R. Bryce and A. P.
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2 P. L. dos Santos, J. S. Ward, M. R. Bryce and A. P. Monkman,
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