Red-Emitting Delayed Fluorescence and Room Temperature Phosphorescence from Core-Substituted Naphthalene Diimides

Article abstract of DOI:10.1002/chem.201904651

Unprecedented ambient triplet-mediated emission in core-substituted naphthalene diimide (cNDI) derivatives is unveiled via delayed fluorescence and room temperature phosphorescence. Carbazole core-substituted cNDIs, with a donor–acceptor design, showed deep-red triplet emission in solution processable films with high quantum yield. This study, with detailed theoretical calculations and time-resolved emission experiments, enables new design insights into the triplet harvesting of cNDIs; an important family of molecules which has been, otherwise, extensively been investigated for its n-type electronic character and tunable singlet fluorescence.

Full text of DOI:10.1002/chem.201904651

A Journal of
Accepted Article
Title: Red-emitting Delayed Fluorescence and Room Temperature
Phosphorescence from Core-substituted Naphthalene Diimides
Authors: Suman Kuila, Anaranya Ghorai, Pralok K. Samanta, Raja B.
K. Siram, Swapan K. Pati, K. S. Narayan, and Subi J. George
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To be cited as: Chem. Eur. J. 10.1002/chem.201904651
Link to VoR: http://dx.doi.org/10.1002/chem.201904651
Supported by

10.1002/chem.201904651
Chemistry - A European Journal
COMMUNICATION
Red-emitting Delayed Fluorescence and Room Temperature
Phosphorescence from Core-substituted Naphthalene Diimides
Suman Kuila,[a] Anaranya Ghorai,[b] Pralok K. Samanta,[c] Raja B. K. Siram,[a] Swapan K. Pati,[c] K. S.
Narayan[b] and Subi J. George*[a]
Dedicated to Professor C. N. R. Rao on the occasion of his 85th birthday
a)
Abstract: Unprecedented ambient triplet mediated emission in core-
substituted naphthalene diimide (cNDI) derivatives is unveiled via
delayed fluorescence and room temperature phosphorescence.
Carbazole core-substituted cNDIs, with a donor-acceptor design,
showed deep-red triplet emission in solution processable films with
high quantum yield. This study, with detailed theoretical calculations
and time-resolved emission experiments, enables new design
insights into the triplet harvesting of cNDIs; an important family of
molecules which has been, otherwise, extensively investigated for its
n-type electronic character and tunable singlet fluorescence.
CzNDI
CzPhNDI
b)
electron
hole
1,4,5,8-Naphthalenetetracarboxylic acid diimides (NDIs) are a
very important class of molecules in functional organic and
supramolecular materials.[1] NDIs have been extensively used in
organic FETs and photovoltaic applications as air-stable, n-type
semiconductors.[2] Improved synthetic methodologies to access
library of core-substituted NDIs (cNDIs) with tunable energetic
levels have further expanded its scope to various optoelectronic
and sensor applications and also as a model system in
supramolecular chemistry.[1a,3] Novel anion-π interactions have
been experimentally realized in electron deficient cNDIs and later
used in halide sensing, organocatalysis and for anion transport
through lipid bilayers.[4-6] Remarkably, air-stable radical anions of
cNDI derivatives are now synthetically feasible[7] and may be of
potential use in artificial photosynthetic cascades for efficient
solar energy conversion.[8] Apart from its electronic properties,
the tunable fluorescence of cNDIs in solution are used in energy
transfer and circularly polarized luminescence.[9] However, for
advanced luminescence applications such as solid state lighting
and organic light emitting diodes (OLEDs), triplet harvesting of
these molecules is an important requirement to improve the
efficiency of these devices.[10]
ν = 0.959
f = 0.20
f = 0.25
ν = 0.958
c)
S1
S1
2.13 eV
2.25 eV
ΔEST = 0.17 eV
ΔEST = 0.15 eV
T1
T1
2.0 eV
2.08 eV
F
DF
P
F
DF
P
S0
S0
Figure 1. a) Molecular structures and corresponding sample photographs of
CzNDI (left) and CzPhNDI (right). b) Natural transition orbitals for S1 state at
the optimized S0 geometry for optical absorption of CzNDI (left) and CzPhNDI
*
(right) calculated using B97XD/6-31+g(d) level of theory in vacuum. Hole
and electron wave functions with the largest weight (v) and the oscillator
strength for the transition (f) are also provided. c) Proposed singlet and triplet
energy states of CzNDI (left) and CzPhNDI (right). F = fluorescence, DF =
delayed fluorescence, P = phosphorescence.
In this respect, however, NDIs are relatively unexplored
in spite of the presence of multiple carbonyl groups in its core to
promote fast intersystem crossing (ISC) and despite having
excellent triplet yield. [11] Very recently, efforts have been made in
stabilizing these NDI triplets by heavy atom substitution or by
intermolecular charge-transfer in confined supramolecular
microenvironments, to harvest ambient room temperature
phosphorescence (RTP).[12] However, molecular engineering of
cNDIs to modulate the excited state energy levels (Sn and Tn) and
emission wavelengths and also to realize other means of triplet
harvesting such as thermally activated delayed fluorescence and
triplet-triplet annihilation up-conversion still remains a challenge.
We envisage that low lying triplets of cNDIs would also benefit in
the design of red to NIR triplet emitters.[13] Charge-transfer (CT)
states created by the spatially separated donor and acceptor
subunits is a crucial design to obtain a small singlet-triplet gap
[a]
S. Kuila, Dr. R. B. K. Siram, Prof. Dr. S. J. George
New Chemistry Unit and School of Advanced Materials (SAMat)
Jawaharlal Nehru Centre for Advanced Scientific Research
(JNCASR) Jakkur, Bangalore 560064, India
E-mail: george@jncasr.ac.in, subijg@gmail.com
A. Ghorai, Prof. Dr. K. S. Narayan
Chemistry and Physics of Materials Unit,
Jawaharlal Nehru Centre for Advanced Scientific Research
(JNCASR)
[b]
[c]
Dr. P. K. Samanta, Prof. Dr. S. K. Pati
Theoretical Science Unit,
Jawaharlal Nehru Centre for Advanced Scientific Research
(JNCASR)
Supporting information for this article is given via a link at the end of
the document.
(ΔEST
)
to aid triplet mediated delayed emission from
chromophores.[10a,14] In this work, we introduce a donor-acceptor
molecular design to harvest the triplets in cNDI derivatives, by
1
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104
103
102
101
100
1.5
1.0
0.5
0.0
IRF
a)
b)
c)
CzNDI (Abs)
CzPhNDI (Abs)
CzNDI (Em)
CzNDI-430 nm
CzPhNDI-430 nm
CzPhNDI-580 nm
CzPhNDI (Em)
I
A / I
em
/ Counts
350 420 490 560 630 700
/ nm
20
40
60
80
100

tns
d)
electron
CzNDI
CzPhNDI
hole
ν = 0.957
f = 0.00
f = 0.40
ν = 0.961
Figure 2. a) Synthetic scheme for CzNDI and CzPhNDI. Reagents and conditions: i) 1,1-dibromo-5,5-dimethylhydantoin, conc. H2SO4, 50 ºC, 24 h, 93%; ii) n-octyl
amine, acetic acid, 100 ºC, 24 h, 88%; iii) Carbazole, Pd(OAc)2, P(o-tol)3, potassium tert-butoxide, toluene, 120 ºC, 24 h, 42%; iv) 9H-Carbazole-9-(4-phenyl)boronic
acid pinacol ester, Pd(PPh3)4, aq. K2CO3, toluene, 120 ºC, 24 h, 64%. b) Absorption and normalized emission spectra of CzNDI and CzPhNDI in THF ([CzNDI]
and [CzPhNDI] = 0.05 mM, λexc. = 380 nm) and c) corresponding lifetime decay spectra collected at the locally excited emission wavelength (430 nm) and charge-
transfer emission wavelength (580 nm). IRF is the instrument response function and λexc. = 373 nm; d) Natural transition orbitals for S1 states at optimized S1 state
*
geometry for emission of CzNDI (left) and CzPhNDI (right) using B97XD/6-31+g(d) level of theory in vacuum. Hole and electron wave functions with the largest
weight (v), the oscillator strength for the transitions (f) are also provided.
substituting the electron-deficient NDI cores with carbazole (Cz)
donor moieties. Remarkably, these core-substituted NDI
derivatives CzNDI and CzPhNDI, showed red-emitting delayed
fluorescence (DF) and room temperature phosphorescence
(RTP), phenomena rarely reported in NDI based molecules
(Figure 1a). With detailed time dependent density functional
theory (TDDFT) calculations and time-resolved emission
spectroscopy, further we provide a structure-property study on
how to increase the oscillator strength of emission in these cNDI
derivatives, which depends heavily on the excited state geometry
of the chromophores.
also shows the spatial separation of HOMO-LUMO for a suitable
charge-transfer state formation in the molecules in their ground
states.[13c]
In solution state (THF), both CzNDI and CzPhNDI show
a locally excited (LE) absorption band at around 300-400 nm and
a charge-transfer (CT) band in the longer wavelengths (420-650
nm) (Figure 2b). The locally excited or charge-transfer nature of
the absorption bands were confirmed by their sensitivity towards
the polarity of the solvents (Figure S2). Both the molecules
showed characteristic LE emission bands with sharp vibrational
features at 400-500 nm with short lifetime (0.99 ns and 0.90 ns for
CzNDI and CzPhNDI, respectively) on excitation at 380 nm
(Figures 2b-c). Interestingly, CzPhNDI showed a CT emission
with a maximum at 580 nm, whereas CzNDI does not show any
CT emission in THF (λexc. = 380 nm, Figure 2b and Figure S2).
The CT nature of CzPhNDI emission is evident from the long
lifetime of 9.3 ns and its solvatochromic behaviour (λexc. = 373 nm,
λmonitored = 580 nm) (Figure 2c and Figure S2). In order to get
further insight into this remarkable difference in emission
characteristics, we theoretically investigated the nature of excited
states using TDDFT methods. In the excited state of CzNDI, the
Cz and NDI units are found to be perpendicular to each other
(dihedral angle ~90o), thus forming a stable twisted intramolecular
charge transfer (TICT) state (S1), with complete spatial separation
of hole and electron wavefunctions (Figure 2d, left panel); a
geometry that weakens the transition dipole moment matrix
element as evident from the low oscillator strength of emission (f
= 0.00). On the contrary, due to the presence of a phenyl spacer
in CzPhNDI, the TICT state is not stable and both the Cz and NDI
units tend to adapt a more planar conformation (dihedral angle
~2º) in its optimized excited (S1) state (Table S1-S2). This leads
to a comparatively higher spatial overlap between hole and
CzNDI and CzPhNDI were synthesized from dibromo
naphthalene diimide derivative 3, using Pd-catalysed Buchwald-
Hartwig amination and Suzuki coupling reactions, respectively
(Figure 2a, Supporting Information). TDDFT studies of the ground
state geometries (S0) revealed dihedral angles of 57º and 61º
between donor (Cz) and acceptor (NDI) moieties for CzPhNDI
and CzNDI, respectively (Table S1). Further natural transition
orbital (NTO) analysis was performed to understand the nature of
transitions in the molecules. In both molecules for optical
absorption to S1 state, the hole NTO is localized on carbazole
units and the electron NTO is localized on NDI core, in consistent
with the molecular design having suitable charge-transfer
transitions (Figure 1b). This was further supported experimentally
by cyclic voltametry (CV) studies where highest occupied
(HOMO) and lowest unoccupied (LUMO) molecular orbital
energies were estimated (Figure S1). The calculated HOMO
energies of CzNDI and CzPhNDI were -5.26 eV and -5.17 eV,
respectively. The calculated LUMO energies of CzNDI and
CzPhNDI were -3.86 eV and -3.71 eV respectively. The HOMO
and LUMO energy levels closely match with the HOMO level of
carbazole and NDI LUMO levels, respectively.[15] This observation
2
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104
103
102
b)
c)
a)
1.6
1.2
0.8
0.4
0.0
104
103
102
15 K- Gated (20 ms)
300 K- Steady State
300 K- Gated (0.5 ms)
300 K- Gated (20 ms)
15 K
15 K
100 K
200 K
250 K
300 K
100 K
200 K
250 K
300 K
I
I
I
em
/ Counts
/ Counts
101
101
ΔEST = 0.17 0.03 eV
600 700 800
100
100
500
0
20
40
60
0
2
4
6
8
10
 / nm
t / ms
t / ms
d)
f)
e)
IRF
15 K
100 K
200 K
250 K
300 K
104
103
102
15K-Gated (20 ms)
300 K-Steady State
300 K-Gated (50 s)
Air
Vacuum
1.0
0.5
0.0
1.2
0.8
0.4
0.0
I
I
I
em
em
/ Counts
101
(x 106)
ΔEST = 0.15
0.02 eV
100
500
600
700
800
500
600
700
800
0
2
4
6
8
10
 / nm
 / nm
t / ms
Figure 3. a) Normalized emission spectra of the PMMA films of CzPhNDI at different temperature with varying delay times (0.5 ms and 20 ms) showing DF and
phosphorescence. Temperature dependent lifetime decay profiles of CzPhNDI monitored at b) 640 nm and c) 550 nm. d) Comparision of steady-state emission
intensity of CzPhNDI in air and under vacuum and the inset shows the photograph of CzPhNDI film under 365 nm UV-lamp. e) Normalized emission spectra of
PMMA films of CzNDI at different temperatures with different delay times (50 µs and 20 ms) showing DF and phosphorescence. Inset: Photograph of CzNDI in film
state under 365 nm UV-lamp. f) Lifetime decay spectra of CzNDI at different temperatures (λmonitored = 680 nm). In all cases 1 wt. % CzNDI or CzPhNDI in PMMA
was used and the excitation wavelength was 380 nm.
electron wavefunctions with large oscillator strength (f = 0.40) for
S1-S0 transition leading to emissive CT for CzPhNDI (Figure 2d,
right panel, Table S1-S2). Thus it is evident that a balance
between twist angle and HOMO-LUMO overlap is crucial for high
photoluminescence quantum yield in cNDI derivatives.
suggesting the presence of a delayed emission in CzPhNDI
chromophores (Figure 3a). Further, the gated emission with a
longer delay time of 20 ms at 300 K, revealed vibronic features in
the 600-800 nm range, accompanied by a broad structureless
emission band at 550-600 nm with reduced intensity, hinting
towards the presence of an additional low energy excited state.
Low temperature (15 K) gated emission (20 ms delay) further
showed that the emission band in the 600-800 nm region retains
its vibronic spectral features with the complete disappearance of
the emission contribution in the 550-600 nm suggesting its
phosphorescence nature. This was further confirmed by
temperature dependent, time-resolved emission measurements
at different temperatures (monitored = 640 nm), which showed a
In an attempt to harvest the triplets in these cNDI
derivatives, we further studied them in solid state as non-radiative
pathways arising from vibrational relaxation can quench the triplet
excitons in solution state. However, neat thin films of both CzNDI
and CzPhNDI, made from chloroform solutions showed only weak
emission due to the aggregation induced quenching (Figure S3-
S4). On the other hand, emission spectra of CzNDI and CzPhNDI
dispersed in poly(methylmethacrylate) (PMMA, 1 wt. % dye to
polymer ratio, exc. = 380 nm) showed a substantial blue-shift (30
nm and 50 nm for CzNDI and CzPhNDI, respectively) and
concomitant enhancement in charge-transfer (CT) emission
intensity compared to neat films (Figure S3-S4) suggesting less
aggregation and also a plausible triplet state stabilization due to
reduced oxygen diffusion contributing effectively in the total
emission (vide infra).[16] Unlike the solution state, the intensity of
LE emission (400-500 nm) in PMMA films was less compared to
the CT emission and hence all further studies were focussed on
CT emission. CzPhNDI films showed higher emission quantum
yield of 32% compared to the 2% of CzNDI.
decrease in average lifetime on increasing temperature (tavg.
=
6.45 ms and 2.43 ms at 15 K and 300 K, respectively, Figure
3b).[17] Along with this long lifetime decay, CzPhNDI also showed
a prompt CT fluorescence with an average lifetime of 7.3 ns (exc.
= 373 nm, monitored = 640 nm) (Figure S5). On the other hand,
average lifetime of the delayed emission at lower wavelength
region, selectively monitored at 550 nm showed an increase in
lifetime with increase in temperature (exc. = 380 nm, tavg. = 78 µs
and 1.2 ms at 15 K and 300 K, respectively) characteristic of
molecules with delayed fluorescence (DF) mediated via triplet
excitons (Figure 3c) consistent with its small singlet-triplet energy
gap (ΔEST = 0.17 ± 0.03 eV). In addition, a threefold increase in
emission intensity and corresponding increase in average lifetime
under vacuum compared to the emission under ambient
conditions, reiterates the contribution from triplet states in
CzPhNDI emission (Figure 3d, Figure S6).[13c] Low temperature
solvatochromism studies with appropriate control molecules
further revealed that triplet states are of locally excited character
To elucidate the triplet contribution in the emission of
CzPhNDI detailed time-resolved and temperature dependent
fluorescence spectroscopy measurements were performed by
exciting the LE state at 380 nm. Steady-state emission at 300 K,
showed a broad emission (500-800 nm) with a maximum at 640
nm (Figure 3a). Interestingly, a gated emission spectrum with a
short time delay (0.5 ms) showed similar emission spectrum
3
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originating from the acceptor NDI unit rather than charge-transfer
in nature (Figure S7-S9). These experiments provides an
unequivocal proof for the co-existence of both DF and RTP
emission in the red-wavelength region with excellent quantum
yield. To the best of our knowledge, this is the first report of dual
DF and RTP from donor-acceptor cNDI derivatives under ambient
conditions.[12] Direct excitation at the charge-transfer band at 500
nm, also resulted in similar spectroscopic features suggesting
that triplet state harvesting is possible via both LE and CT states
(Figure S10).
On the other hand, PMMA (1 wt. %) films of CzNDI showed
a weak CT emission (exc. = 380 nm) in the 550-800 nm region
unlike its non-fluorescent nature in solution state (Figure 3e) with
a prompt lifetime of 3.45 ns (exc. = 373 nm, monitored = 680 nm),
probably due to a non-orthogonal, excited state conformation in
the solid-state (Figure S11). Delayed emission feature is also
observed for CzNDI films at 300 K as confirmed by a gated
emission spectrum (delay time = 50 µs, exc. = 380 nm) in the
same wavelength region (550-800 nm, max. = 680 nm) hinting
towards similar DF and RTP characteristics like CzPhNDI (Figure
3a and 3e). Time-gated emission spectra (20 ms delay time, exc.
= 380 nm) obtained at 15 K showed a 80 nm red-shift compared
to room temperature steady-state emission (Figure 3e). This low
energy emission with a maximum at 680 nm, can be attributed to
the locally excited phosphorescence because of its high lifetime
(tavg.= 3.1 ms, exc. = 380 nm, monitored = 680 nm) (Figure 3f, Figure
S12a). However, unlike CzPhNDI, this phosphorescence band
neither originates from carbazole (donor) or NDI (acceptor)
components (Figure S12b). Similar phosphorescence behaviour
at low temperatures has been recently shown in donor-acceptor
cNDI derivatives, wherein certain conformations of the molecule
lead to enhanced conjugation between the donor (triphenyl
amine) and acceptor sub-units (NDI) resulting in new locally
excited triplet state.[13b] In addition, gradual decrease in the
lifetime on increasing the temperature (Figure 3f) reiterates (3.1
ms at 15 K to 80.5 µs at 300 K, exc. = 380 nm, monitored = 680 nm)
its phosphorescence character similar to CzPhNDI at this
wavelength. Accordingly, temperature dependent steady-state
emission also showed a gradual red-shift (652 nm to 672 nm) and
enhanced emission intensity on decreasing the temperature
(Figure S13). Presence of triplet mediated (ΔEST = 0.15 ± 0.02 eV)
deep-red-NIR dual DF and RTP emission was further confirmed
via various experiments (Figure S14-S16). However, overall
quantum yield (2 %) was found to be much weaker than
CzPhNDI.
In conclusion, we have shown an efficient dual DF and RTP
emission under ambient and amorphous conditions from cNDI
derivatives by a clever molecular design to facilitate the triplet
harvesting. Time-resolved photoluminescence studies and
TDDFT calculations further provided
a structure-property
relationship to fine-tune the emission oscillator strength and
charge-transfer states of these donor-acceptor molecules. We
envisage that this study opens up an exciting, hitherto unexplored
triplet harvesting of interesting class of cNDI family, by using the
well-established, rich chemistry of core-substitution. Further
extension of these designs to other electron deficient arylene
diimides would be the next step to achieve NIR-emitting triplet-
emitting dyes for applications in bio-imaging and OLEDs.[18]
[5]
a) Y. Zhao, Y. Domoto, E. Orentas, C. Beuchat, D. Emery, J. Mareda, N.
Sakai, S. Matile, Angew. Chem. Int. Ed. 2013, 52, 9940-9943; b) L. Liu, Y.
Cotelle, A.‐B. Bornhof, C. Besnard, N. Sakai, S. Matile, Angew. Chem.
Int. Ed. 2017, 56, 13066-13069.
Acknowledgements
Funding from Technology Research Centre at JNCASR
(JNC/DST/TRC/SJG-KSN/4397) & DST-JNCASR Nanomission
Project (SR/NM/TP-25/2016) by Government of India are greatly
acknowledged. S. K. thanks UGC; A. G. and P. K. S. thank
JNCASR for fellowship. The authors thank Prof. Satish Patil,
SSCU, IISc for fruitful discussions.
[6]
[7]
R. E. Dawson, A. Hennig, D. P. Weimann, D. Emery, V. Ravikumar, J.
Montenegro, T. Takeuchi, S. Gabutti, M. Mayor, J. Mareda, C. A.
Schalley, S. Matile, Nat. Chem. 2010, 2, 533-538.
a) Y. Kumar, S. Kumar, K. Mandal, P. Mukhopadhyay, Angew. Chem.
Int. Ed. 2018, 57, 16318-16322; b) S. Kumar, M. R. Ajayakumar, G.
Hundal, P. Mukhopadhyay, J. Am. Chem. Soc. 2014, 136, 12004-12010;
c) G. Bẽlanger-Chabot, A. Ali, F. P. Gabbaï, Angew. Chem. Int. Ed. 2017,
56, 9958-9961.
Keywords: Donor-acceptor systems• Naphthalenediimide•
Delayed Fluorescence• Room Temperature Phosphorescence •
Charge-transfer.
[8]
[9]
P. D. Frischmann, K. Mahata, F. Würthner, Chem. Soc. Rev. 2013, 42,
1847-1870.
a) A. Sarkar, S. Dhiman, A. Chalishazar, S. J. George, Angew. Chem.
Int. Ed. 2017, 56, 13767-13771; b) R. Sethy, J. Kumar, R. Métivier, M.
Louis, K. Nakatani, N. Mohan, T. Mecheri, A. Subhakumari, K. G.
Thomas, T. Kawai, T. Nakashima, Angew. Chem. Int. Ed. 2017, 56,
15053-15056; c) A. Takai, M. Takeuchi, Bull. Chem. Soc. Jpn. 2018, 91,
44–51.
[1]
[2]
a) N. Sakai, J. Mareda, E. Vauthey, S. Matile, Chem. Commun. 2010,
46, 4225-4237; b) S. V. Bhosale, C. H. Jani, S. J. Langford, Chem. Soc.
Rev. 2008, 37, 331-342.
a) J. H. Oh, S.-L. Suraru, W.-Y. Lee, M. Könemann, H. W. Höffken, C.
Röger, R. Schmidt, Y. Chung, W.-C. Chen, F. Würthner, Z. Bao, Adv.
Funct. Mater. 2010, 20, 2148-2156; b) T. He, M. Stolte, F. Würthner Adv.
Mater. 2013, 25, 6951-6955; c) H. Yan, Z. Chen, Y. Zheng, C. Newman,
J. R. Quinn, F. Dötz, M. Kastler, A. Facchetti, Nature 2009, 457, 679-
686.
[10] a) H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Nature 2012,
492, 234-238; b) M. Y. Wong, E. Zysman-Colman, Adv. Mater. 2017, 29,
1605444.
[11] a) P. Ganesan, J. Baggerman, H. Zhang, E. J. R. Sudhölter, H. Zuilhof,
J. Phys. Chem. A 2007, 111, 6151-6156; b) O. Yushchenko, G. Licari, S.
Mosquera-Vazquez, N. Sakai, S. Matile, E. Vauthey, J. Phys. Chem. Lett.
2015, 6, 2096-2100.
[3]
[4]
a) S.-L. Suraru, F. Würthner, Angew. Chem. Int. Ed. 2014, 53, 7428-
7448; b) F. Würthner, S. Ahmed, C. Thalacker, T. Debaerdemaeker,
Chem. Eur. J. 2002, 8, 4742-4750; b) C. Röger, F. Würthner, J. Org.
Chem. 2007, 72, 8070-8075; c) R. S. K. Kishore, V. Ravikumar, G.
Bernardinelli, N. Sakai, S. Matile, J. Org. Chem. 2008, 73, 738-740; d) A.
Takai, T. Yasuda, T. Ishizuka, T. Kojima, M. Takeuchi, Angew. Chem.
Int. Ed. 2013, 52, 9167-9171.
[12] a) S. Kuila, K. V. Rao, S. Garain, P. K. Samanta, S. Das, S. K. Pati, M.
Eswaramoorthy, S. J. George, Angew. Chem. Int. Ed. 2018, 57, 17115-
17119; b) V. Martinez-Martinez, R. S. Llano, S. Furukawa, Y. Takashima,
I. L. Arbeloa, S. Kitagawa, ChemPhysChem 2014, 15, 2517-2521.
[13] a) J. H. Kim, J. H. Yun, J. Y. Lee, Adv. Opt. Mater. 2018, 6, 1800255; b)
H. F. Higginbotham, P. Pander, R. Rybakiewicz, M. K. Etherington, S.
Maniam, M. Zagorska, A. Pron, A. P. Monkman, P. Data, J. Mater. Chem.
C 2018, 6, 8219-8225; c) F. B. Dias, J. Santos, D. R. Graves, P. Data,
a) S. Guha, S. Saha, J. Am. Chem. Soc. 2010, 132, 17674-17677; b) S.
Guha, F. S. Goodson, L. J. Corson, S. Saha, J. Am. Chem. Soc.
2012, 134, 13679-13691.
4
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R. S. Nobuyasu, M. A. Fox, A. S. Batsanov, T. Palmeira, M. N. Berberan‐
Santos, M. R. Bryce, A. P. Monkman, Adv. Sci. 2016, 3, 1600080.
[14] a) Y. Tao, K. Yuan, T. Chen, P. Xu, H. Li, R. Chen, C. Zheng, L. Zhang,
W. Huang, Adv. Mater. 2014, 26, 7931-7958; b) Y. Im, M. Kim, Y. J. Cho,
J.-A Seo, K. S. Yook, J. Y. Lee, Chem. Mater. 2017, 29, 1946-1963; c)
T. J. Penfold, F. B. Dias, A. P. Monkman, Chem. Commun. 2018, 54,
3926-3935.
[15] J. Shukla, M. R. Ajayakumar, P. Mukhopadhyay, Org. Lett. 2018, 20,
7864-7868. Attempt has been made towards synthesizing similar
derivative; however triplets are not explored in this work.
[16] D. Lee, O. Bolton, B. C. Kim, J. H. Youk, S. Takayama, J. Kim, J. Am.
Chem. Soc. 2013, 135, 6325-6329.
[17] L. Yu, Z. Wu, C. Zhong, G. Xie, Z. Zhu, D. Ma, C. Yang, Adv. Opt. Mater.
2017, 5, 1700588.
[18] a) M. Schulze, A. Steffen, F. Würthner, Angew. Chem. Int. Ed. 2015, 54,
1570-1573; b) X. Zhen, Y. Tao, Z. An, P. Chen, C. Xu, R. Chen, W.
Huang, K. Pu, Adv. Mater. 2017, 29, 1606665; c) N. Gan, H. Shi, Z. An,
W. Huang, Adv. Funct. Mater. 2018, 28, 1802657.
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COMMUNICATION
Air-stable, amorphous and purely organic triplet mediated IrSeCd emission is achieved
Suman Kuila, Anaranya Ghorai, Pralok K.
Samanta, Raja Bhaskar Kanth Siram,
Swapan K. Pati, K. S. Narayan, and Subi
J. George*
Ambient Triplet Harvesting from cNDIs
S1
via delayed fluorescence and room temperature phosphorescence from donor
T1
RISC
(carbazole) core-substituted, naphthalene dimide molecules
Page No. – Page No.
S0
Red-emitting Delayed Fluorescence and
Room Temperature Phosphorescence
from Core-Substituted Naphthalene
Diimides
Air-stable, amorphous and purely organic triplet mediated red emission is achieved
via delayed fluorescence and room temperature phosphorescence from donor
(carbazole) core-substituted, naphthalene diimide molecules.
6
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