Full text of DOI:10.1016/j.saa.2018.01.004

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 194 (2018) 111–116
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, structures and photophysical properties of two
regioisomeric phenalenocarbazoles
Chang-En Luo a,1, Zhe Ding a,b,1, Xiang-Wen Wu , Zhiqiang Liu
c
a,b,
⁎
a
State Key Laboratory of Crystal Materials, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai
00032, China
b
2
c
College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging, Key Laboratory of Molecular and Nano Probes,
Ministry of Education, Shandong Normal University, Jinan 250014, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 June 2017
Received in revised form 15 December 2017
Accepted 3 January 2018
Available online 04 January 2018
Two regioisomeric phenalenocarbazoles have been synthesized by direct reductive cyclization of 2′-Nitrophenyl-
pyrene isomers respectively. Their photophysical properties and crystal structures as well as CV properties were
investigated and compared with those of sulfur containing analogues. Although the fluorescence emission prop-
erties of 1N are very similar with those of 2N, the HOMO energy level of 1N is 0.16 eV higher than that of 2N in-
dicating that 1N has better electron donating ability.
©
2018 Elsevier B.V. All rights reserved.
Keywords:
Pyrene
Regioisomer
Phenalenocarbazole
Fluorescence
1
. Introduction
h]carbazole, dinaphtho[2,3-b:2′,3′-h]carbazole, indolo[3,2-b]carbazole,
have been experimentally and theoretically studied [11]. However, al-
though pyrene seems match the basic requirement as organic semicon-
ductor due to its remarkable intramolecular π-conjugation and
intermolecular π–π interaction, the pyrene anellated carbazole deriva-
tives were still seldom reported in literatures.
Carbazole has been extensively studied and functionalized as a flex-
ible synthon of biologically active natural product and pharmaceutical
drug [1–3]. Due to its highly rigid structure and excellent blue-emission
property, the carbazole moiety has also found wide application as a key
building block of organic optoelectronic material in organic light-emit-
ting device (OLEDs) [4,5] and polymeric light-emitting diode (PLEDs)
As part of our continuing work on pyrene−based PAH for optoelec-
tronic materials applications [12–14], we have presented interesting
structurally isomeric pyrene–thienoacenes (PTAs) through very differ-
ent synthetic routes. To examine the role of ring cyclization mode and
heteroatom for tuning their photo-physical properties, we also tried to
synthesize some structurally isomeric phenalenocarbazole. Among the
recently reported methods for the synthesis of carbazole derivatives
[15–21], nucleophilic substitution of dibenzothiophene dioxides with an-
ilines under transition-metal-free conditions was developed by Yorimitsu
and co-workers for N-substituted carbazoles [22]. Although our PTA
could be oxidized to sulfone-bridged phenyl-pyrene [13], it cannot be eas-
ily converted to a targeting N-H carbazole derivative through this route.
The modified Cadogan reaction was reported by Freeman et al. to cyclize
the 2-nitrobiphenyls via reductive deoxygenation of the nitro groups and
directly gives the related N-H carbazoles [23]. This straightforward reac-
tion is very convenient to execute and tolerate a broad range of functional
groups, so it was adapted in our research.
[6]. Recently, carbazole derivatives were also adapted as electron donors
in the thermally activated delayed fluorescence (TADF) materials dem-
onstrating very high external quantum efficiency [7–9]. In addition, the
carbazole embedded organic field-effect transistor (OFET) materials
were also reported [10].
Generally, benzo-annelation and introducing heteroatom into a local
aromatic compound are very common strategies to build or extend or-
ganic conjugate systems for organic materials. Nitrogen and sulfur are
the most popular doped elements. Certainly, even changing the mode
and sites of annelation between same building blocks will result in dif-
ferent electronic structures and properties. As analogue of angular poly-
cyclic aromatic hydrocarbons (PAH), the annellated carbazoles, such as
dibenzo[c,g]carbazole, naphtho[2,3-b]carbazole benzo[a]naphtho-[2,3-
⁎
Corresponding author at: State Key Laboratory of Crystal Materials, School of
We present here the synthesis, crystal structures and light emitting
properties of two phenalenocarbazoles. To easily identify the structural
difference, these two compounds were named as nitrogen-bridged
Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China.
E-mail address: zqliu@sdu.edu.cn (Z. Liu).
C. L. and Z. D. contributed equally.
1
https://doi.org/10.1016/j.saa.2018.01.004
1386-1425/© 2018 Elsevier B.V. All rights reserved.

112
C.-E. Luo et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 194 (2018) 111–116
phenyl-pyrene and abbreviated as 1N and 2N hereafter. The comparison
between regioisomers and between sulfur [12] and nitrogen bridged
phenyl-pyrene derivatives are especially emphasized to understand
structure-property relationships.
2.3. Theoretical Calculations
For all calculation, the B3LYP hybrid functional and 6-311G basis set
were used, as incorporated in the Gaussian 03 package. The ground state
geometries of 1N and 2N molecules were optimized using the initial ge-
ometry derived from their molecular structures as determined by X-ray
diffraction. Based on the optimized ground state geometries, the single
point excited state calculations were performed using time-dependent
density functional theory (TD-DFT) with the B3LYP functional.
2
. Experimental
2
.1. Materials and Instruments
Pyrenyl-1-boronic acid is commercial available and 2-Bpin-pyrene
was prepared as previously reported by Marder et al. [24]. All the other re-
agents were purchased from Acros Ltd. All solvents were freshly distilled
2.4. General Procedure for Synthesis of Phenalenocarbazoles (1N and 2N)
1
13
before using. H and C NMR spectra were recorded with Bruker 300 or
00 spectrometers in CDCl with TMS as internal references. High-Res
4
3
To a solution of Pyrenyl-1-boronic acid or 2-Bpin-pyrene (1.0 mmol)
in toluene (10 mL), was added 1-iodo-2-nitro-benzene (0.25 g,
Mass spectra were recorded using MALDI (DHB matrix) or DART modes.
UV–vis absorption spectra were recorded on a Shimadzu UV 2550
1.0 mmol), Pd(PPh
3 4
) (10 mg, 0.01 mmol) and aqueous solution
−
6
−1
spectrometer with C = 5.0 × 10 mol∙L . Steady state fluorescence
emission spectra were recorded on an Edinburgh FLS920 fluorescence
spectrometer equipped with a 450 W Xe lamp. Reconvolution fits of
the fluorescence decay curves were made with F900 analysis software
to obtain the lifetime values. To measure the quantum yields of these
compounds, pure pyrene and coumarin 307 were used as the reference.
Cyclic voltammetric measurements were carried out in a conven-
tional three-electrode cell using a Pt wire working electrodes, a Pt
wire counter electrode, and a Ag/AgCl reference electrode on AMETEK
Parstat 2273 instrument. Freshly distilled DCM was used as the solvent
Na CO (1.0 M, 2 mL). Then the mixture was heated to 80 °C for 12 h.
2
3
The organic phase was washed with water and extracted with DCM,
then the solvent was removed under vacuum and the residue was puri-
fied by column chromatography using dichloromethane as eluent to af-
ford yellow powders of products 1 (or 2).
To a solution of 2′-nitro-phenyl-1-pyrene (1) or 2′-nitro-phenyl-2-
pyrene (2) (0.10 g, 0.34 mmol) in dried 1,2-dichloro-benzene
(10 mL), was added tri-phenyl-phosphine (0.26 g, 1.0 mmol) and the
mixture was heated to reflux for 12 h. The solvent was removed
under vacuum and the residue was purified by column chromatography
and tetrabutylammonium hexafluorophosphate (Bu
4
NPF
with a scan rate of 100 mV·s
Fc /Fc was used as external reference.
6
)
as
.
using dichloromethane as eluent to afford yellow crystalline products.
−
1
−1
1
supporting electrolyte in 0.1 M·L
3
1: 75% yield. M.p. 168 °C. H NMR (300 MHz, CDCl ) δ 8.21 (d, 2H, J
+
= 10.0 Hz), 8.14–8.06 (m, 7H), 7.98 (dd, 1H, J = 10.8 Hz, J = 1.2 Hz),
1
3
7
.74–7.65 (m, 2H), 7.60–7.55 (m, 1H). C NMR (101 MHz, CDCl
149.64, 136.778, 135.05, 132.90, 132.35, 131.39, 131.19, 128.32,
28.15, 127.28, 126.23, 125.39, 124.38, 124.28, 124.21, 124.15. HRMS
3
) δ
2
.2. Crystallography
Suitable single crystals of 1N and 2N were grown from their DCM so-
1
+
+
(ESI+): m/z[M + Na] 346.0833, calcd for C22
2
H13NO Na 346.0844.
1
lutions. The diffraction data were collected on a Bruker ApexII CCD dif-
2: 70% yield. M.p. 175 °C. H NMR (400 MHz, CDCl
3
) δ 8.22 (d, J =
fractometer using a graphite mono-chromated Mo Kα radiation (λ =
8.0 Hz, 2H), 8.18–8.13 (m, 2H), 8.11 (d, J = 1.2Hz, 2 H), 8.02 (t, J =
8.0 Hz, 2H), 7.87 (d, J = 8.0 Hz, 1H), 7.75 (dt, J = 7.8 Hz, J = 1.2 Hz,
0
.71073 Å) at 20 °C. The structures were solved by directed method
using the program SHELXL and refined by full-matrix least-squares
method on F . The crystal structure of 1N and 2N were deposited at
1H), 7.71 (d, J = 9.2 Hz, 1H), 7.65 (dt, J = 7.8 Hz, J = 1.2 Hz, 1H), 7.59
(dd, J = 7.8 Hz, J = 1.2 Hz, 1H), C NMR (101 MHz, CDCl ) δ 150.04,
3
2
13
the Cambridge Crystallographic Data Centre with deposition numbers
CCDC 1559505 and 1559409, respectively.
135.77, 133.59, 132.62, 132.55, 131.39, 131.25, 130.87, 128.71, 128.28,
127.91, 127.38, 126.35, 126.20, 125.58, 125.33, 124.74, 124.71, 124.64,
Scheme 1. Synthetic approach to isomers of phenalenocarbazoles 1N and 2N.

C.-E. Luo et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 194 (2018) 111–116
113
Fig. 1. Crystal structures of 1N (a) top view (b) side view (some of disordered atoms are not presented for clarity); and 2N (c) top view (d) side view.
1
C
24.40, 124.06. HRMS (ESI+): m/z[M + Na]+ 346.0850, calcd for
a two-step route. The precursors, (2′-nitro-phenyl)pyrene (1 and 2)
+
22
H
13NO
2
Na 346.0844.
could be prepared via typical Suzuki coupling with high yield. If only
count the symmetry of the precursors 1 and 2 in mind, the straightfor-
ward producing of 1N from 1 is reasonable and no doubt, considering
the fact of 2′-nitro-phenyl connecting at 2-position of pyrene, and
therefore no other cyclization could happen. However, the cyclization
of 2 may give either 6-member ring with N atom connect to 10-position
of pyrene or 5-member ring with N atom connect to 2-position of
pyrene. Actually, for the sulfur-containing analogues, we had only ob-
tained 4-S-PTA containing a 6-member ring with S connect to 4-posi-
tion of pyrene via acid-induced cyclization of 1-(2′-methyl sulfoxide-
phenyl)pyrene [12]. However, in this nitrogen-containing case, the
only isolated product was exclusively determined by X-ray diffraction
as 2N, which have a 5-member ring formed with N atom connect to 1-
position of pyrene.
1
1N: 56% yield. M.p. 178 °C. H NMR (400 MHz, CDCl
3
) δ 8.92 (s,1H, N-
H), 8.85 (s,1H), 8.40–8.36 (m, 2H), 8.23–8.15 (m, 4H), 8.03 (m, 2H), 7.92
1
(
(
m, 1H), 7.66 (m, 1H), 7.54 (m, 1H). H NMR (400 MHz, DMSO) δ 12.48
s,1H, N-H), 9.05 (s,1H), 8.82 (d, 1H, J = 8.8 Hz), 8.47 (d, 1H, J = 7.8 Hz),
8
.33 (d, 1H, J = 8.8 Hz), 8.27–8.24 (m, 2H), 8.21 (d, 1H, J = 7.2 Hz),
8
.04–7.98 (m, 2H), 7.78 (m, 1H, J = 8.8 Hz), 7.59 (td, 1H, J = 7.8 Hz, J
0.8 Hz), 7.37 (td, 1H, J = 7.8 Hz, J = 0.8 Hz). 1 C NMR (101 MHz,
3
=
3
CDCl ) δ 139.95, 134.66, 131.68, 131.28, 128.52, 127.25, 126.95,
1
26.28, 125.86, 125.62, 125.56, 124.64, 124.35, 124.23, 123.93, 121.55,
1
20.73, 120.23, 120.05, 117.08, 115.12, 110.97. HRMS (ESI+): m/z[M
+
+
+
H] 292.1128, calcd for C22
2
H
13
N
292.1126.
1
N: 60% yield. M.p. 165 °C. H NMR (400 MHz, CDCl ) δ 9.16 (d, J =
3
9.1 Hz, 1H), 8.83 (d, J = 7.9 Hz, 1H), 8.59 (s, 1H, N-H), 8.38 (d, J = 9.1 Hz,
1H), 8.29 (d, J = 7.6 Hz, 1H), 8.21 (d, J = 9.7 Hz, 2H), 8.13 (d, J = 9.0 Hz,
1H), 8.07 (d, J = 9.0 Hz, 1H), 7.99 (t, J = 7.6 Hz, 1H), 7.68 (d, J = 8.0 Hz,
1
H), 7.59 (t, J = 7.2 Hz, 1H), 7.48 (t, J = 7.2 Hz, 1H). 13C NMR (101 MHz,
The difference between these two kinds of cyclization reactions may
be related to the nature of electronic structure of pyrene. As generally
accepted mechanism, the acid-induced cyclization of aromatic methyl
+
CDCl
3
) δ 140.24, 138.18, 130.47, 130.40, 129.91, 128.33, 127.60, 127.20,
sulfoxides was taken place via S intermediate [25,26]. Because 2-posi-
1
1
2
26.77, 125.64, 125.50, 125.33, 125.13, 124.63, 123.84, 123.53, 122.81,
tion of pyrene normally lies in the node plane of frontier orbitals, thus
the 4-position of pyrene is more electrophilic than 2-position and thus
6-member ring structure is favored. As proposed by Freeman et al.
+
20.18, 120.10, 117.34, 110.76, 107.15. HRMS (ESI+): m/z[M + H]
+
92.1120, calcd for C22
. Results and Discussion
.1. Synthesis and Structures
As shown in Scheme 1, all phenalenocarbazoles compounds were
13
H N
292.1126.
[
23], the mechanism of reductive cyclization of nitro-biphenyl may
−
3
have a N key intermediate being involved. In addition, Park et al. also
only got a 5-member ring structure using this triphenylphosphine-me-
diated reductive cyclization of 4-(2′-nitro-phenyl)pyrene [27]. Thus, the
formation of the 5-member ring structure should be reasonable due to
the different reactive-site selectivity relying on the different
mechanism.
3
synthesized starting from pyrenyl-1 or -2 boronic acid(ester) through
Fig. 2. UV–vis absorption spectra of phenalenocarbazoles 1N, 2N and PTAs in hexane (C =
5
Fig. 3. Normalized fluorescence emission spectra (λex = 375 nm) of phenalenocarbazoles
.0 × 10− mol∙L ).
6
−1
−6
−1
1N, 2N and PTAs in hexane (C = 5.0 × 10 mol∙L ).

114
C.-E. Luo et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 194 (2018) 111–116
3.2. Optical and Electrochemical Properties
The photophysical properties of 1N and 2N were examined. The ab-
sorption and emission spectra of 1N and 2N comparing with those of
un-cyclized precursor (1 and 2) and Sulfur-containing analogues are
shown in Fig. 2 and Fig. 3 and supplementary data (Fig. S-1 and S-2).
Generally, the absorption spectra of un-cyclized precursors (1 and 2)
are quite similar to those of pyrene maintaining the well-resolved
vibronic structures and strong absorption band at around 334 nm
which corresponds to the S
many other pyrene derivatives. The spectral shapes of isometric 1N
and 2N are quite different but cover the similar range. The typical S
transition of pyrene (280–340 nm) was degenerated for 1N and al-
most disappeared for 2N. Both of 1N and 2N have weak absorption
bands corresponding to the S → S transition at 417 nm and 410 nm,
0 2
→ S transition of pyrene as found in
0
→ S
2
0
1
respectively, which are greatly red-shifted by near 100 nm relative to
those of un-cyclized precursors. However, the molar extinction coeffi-
cient of 1N at about 415 nm is nearly 4 times of that of 2N, indicating
that the fusion mode of 1N seems much efficient than 2N. As shown in
Fig. 2, comparing with those of PTAs, the longest absorption bands of
Fig. 4. Cyclic voltammogram of phenalenocarbazoles 1N and 2N in CH
.1 M Bu NPF as supporting electrolyte (CV of 1-S-PTA, 2-S-PTA and Fc were shown for
comparison).
2 2
Cl solution with
0
4
6
1N and 2N are generally red-shifted by 13 nm (404 nm to 417 nm), in-
dicating a narrower HOMO-LUMO gap caused by linking a benzene ring
to pyrene with fusion mode via N-bridge rather than S-bridge.
The structures of 1N and 2N were confirmed by single-crystal X-ray
diffraction (Fig. 1). Although the molecular structure of 1N is asymmet-
ric, the crystal of 1N belongs to tetragonal I4 cd space group and the
1
molecules are mirror disordered. The disorder precludes obtaining
highly accurate parameters, but it still can be seen that the molecular
keep in nearly perfect co-planar manner. 2N crystallized in the mono-
As shown in Fig. 3, the fluorescence emission spectra of 1N and 2N
possess nearly the same position (λem = 423 nm) and very similar
vibronic structures. 2N has a higher quantum yields and longer fluores-
cence lifetime (Φ = 0.38, τ = 8.6 ns) than those of 1N (Φ = 0.28, τ =
5.7 ns), but they are all comparable with those of PTAs. However, the
comparison of radiative transfer rate (K
r
= Φ/τ) and non-radiative
1
clinic P2 /c space groups. The dihedral angle between the phenyl and
transfer rates (Knr = (1-Φ)/τ) for 1N and 2N show that the two isomeric
7
−1
7 −1
pyrenyl is only 4.06°. The bond length of CC bond, which connect phenyl
and pyrenyl in 2N is 1.439 Å, which is obviously shorter than that of 2S–
PTA (1.476 Å).
compounds share similar K
r
(4.4 × 10 s for 1N and 4.9 × 10 s for
8
−1
2N) but the Knr of 2N (1.26 × 10 s ) is almost double that of 1N (7.2
7
−1
× 10 s ).
H
N
NH
LUMO
(
MO-77)
-
-
1.64 eV
-1.86 eV
HOMO
MO-76)
(
5.15 eV
-5.26 eV
Fig. 5. The isosurface (isovalue = 0.02 a. u.) of selected molecular orbitals of 1N and 2N, as calculated by DFT at B3LYP/6-311G(d) level.

C.-E. Luo et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 194 (2018) 111–116
115
The electrochemical properties of 1N and 2N were investigated by
of post-functionalizing of carbazole moiety, we believe these prelimi-
nary results will provide new insight for the further design and applica-
tion of pyrene-based heteroatom-containing PAHs.
+
cyclic voltammetry (CV) (Fig. 4) using ferrocene/ferrocium (Fc/Fc
)
couple [28] as external standard (the HOMO energy level was taken to
be −4.80 eV) [29]. Although the reduction wave are not clearly measur-
able in CH
versible oxidation wave with half-wave potentials at 0.85 eV for 1N and
.01 eV for 2N and that of ferrocene is 0.48 eV, respectively. Thus, the
HOMO energy level could be estimated as of −[4.8 + (0.85–0.48)] =
5.17 eV for 1N and −[4.8 + (1.01–0.48)] = −5.33 eV for 2N. Clearly,
2
Cl
2
under this condition, the CV of both 1N and 2N show re-
Acknowledgements
1
This work was supported by the National Natural Science Founda-
tion of China (21672130), the Fundamental Research Funds of Shan-
dong University (2017JC011), the State Key Laboratory of Crystal
Materials and also open project of Key Laboratory of Synthetic and
Self-Assembly Chemistry for Organic Functional Molecules (K2017-5).
−
the fusion mode of 1N can efficiently heighten the HOMO energy level
and enhance electron-donating ability.
As reported before, the isometric 1-S-PTA and 2-S-PTA have very
similar oxidation potentials at about 0.80 eV (vs Ag/AgCl). So the direct
comparison between phenalenocarbazoles and PTAs clearly indicated
the N-bridged fusion mode can effectively extend the π-delocalization
with little lower HOMO level than S-bridged fusion mode. Considering
the narrower bandgap from the absorption spectroscopy (2.97 eV for
Appendix A. Supplementary Data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.saa.2018.01.004.
1
=
N, 3.02 eV for 2N, 3.07 eV for 1-S-PTA and 2-S-PTA, calculated at λabs
417 nm for 1N and λabs = 410 nm for 2N, λabs = 404 nm for 1-S-
References
[
1] A.W. Schmidt, K.R. Reddy, H.-J. Knölker, Occurrence, biogenesis, and synthesis of bi-
PTA and 2-S-PTA), the LUMO energy level of phenalenocarbazoles are
much lower than those of PTAs.
ologically active carbazole alkaloids, Chem. Rev. 112 (2012) 3193–3328.
[2] G. Yaqub, E.A. Hussain, M.A. Rehman, B. Mateen, Advancements in syntheses of car-
bazole and its derivatives, Asian J. Chem. 21 (2009) 2485–2520.
[
[
3] N. Blouin, M. Leclerc, Poly(2,7-carbazole)s: structure−property relationships, Acc.
Chem. Res. 41 (2008) 1110–1119.
4] K. Brunner, A. van Dijken, H. Börner, J.J.A.M. Bastiaansen, N.M.M. Kiggen, B.M.W.
Langeveld, Carbazole compounds as host materials for triplet emitters in organic
light-emitting diodes: tuning the HOMO level without influencing the triplet energy
in small molecules, J. Am. Chem. Soc. 126 (2004) 6035–6042.
3
.3. Theoretical Calculations
In order to gain insight into the π-conjugation modes and under-
stand the photophysical properties of the present molecules, we con-
ducted some theoretical calculations of them. The pictorial drawing of
frontier molecular orbitals are shown in Fig. 5. Generally, the TD-DFT
calculated lowest energy transitions of phenalenocarbazoles seem able
to reproduce their main absorption bands and relative energy of frontier
orbitals as observed experimentally very well. Especially, the calculated
energy level of HOMO of 1N is 0.11 ev higher than that of 2N, which is
very close to the experimental CV results.
[5] H. Jiang, Hosts for high-performance phosphorescent organic light-emitting diodes
based on carbazole derivatives, Asian J. Org. Chem. 3 (2014) 102–112.
[6] F. Dumur, Carbazole-based polymers as hosts for solution-processed organic light-
emitting diodes: simplicity, efficacy, Org. Electron. 25 (2015) 345–361.
[7] H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Highly efficient organic light-
emitting diodes from delayed fluorescence, Nature 495 (2012) 234–238.
[8] Y. Tao, K. Yuan, T. Chen, P. Xu, H. Li, R. Chen, C. Zheng, L. Zhang, W. Huang, Thermally
activated delayed fluorescence materials towards the breakthrough of
organoelectronics, Adv. Mater. 26 (2014) 7931–7958.
It is well known, that the nature and the site of substituent will ob-
viously tune the photophysical properties of pyrene derivatives [30–
[9] L. Bergmann, D.M. Zink, S. Brӓse, T. Baumann, D. Volz, Metal–organic and organic
TADF-materials: status, challenges and characterization, Top. Curr. Chem. 374 (22)
(2016).
3
2]. Marder et al. had reported that in the 2-substituted pyrene deriva-
tives, the substituent only make strong influence on the S ← S excita-
tion, which is initially a weak excitation; In contrast, the 1-substituted
pyrene derivatives display a strong influence on both the S ← S and
the S ← S excitations [32]. In other words, the substituents at 1 posi-
[
[
10] H. Jiang, H. Zhao, K.K. Zhang, X. Chen, C. Kloc, W. Hu, High-performance organic sin-
gle-crystal field-effect transistors of indolo[3,2-b]carbazole and their potential ap-
plications in gas controlled organic memory devices, Adv. Mater. 23 (2011)
1
0
5075–5080.
1
0
11] A.L. Marzinzik, P. Rademacher, M. Zander, Structural chemistry of polycyclic
heteroaromatic compounds. Part 9. Photoelectron spectra and electronic structures
of anellated carbazoles. Extension of Clar's aromatic sextet model to hetarenes, J.
Mol. Struct. 375 (1996) 117–126.
12] S. Zhang, X. Qiao, Y. Chen, Y. Wang, R.M. Edkins, Z. Liu, H. Li, Q. Fang, Synthesis,
structure, and opto-electronic properties of regioisomeric pyrene–thienoacenes,
Org. Lett. 16 (2014) 342–345.
13] S. Zhang, Y. Chen, Z. Liu, Q. Fang, Synthesis, structure and photophysical properties
of regioisomeric sulfone-bridged pyrene–thienoacenes, J. Photochem. Photobiol. A
Chem. 311 (2015) 25–29.
2
0
tion make the main influence on the excitations between the frontier
orbitals. In our cases, the conjugations of phenalenocarbazoles isomers
are greatly depend on the substituent of the position 1 of pyrene: phe-
nyl or N atom with lone pairs. As shown in Fig. 5, there are nodal planes
in the HOMO and LUMO of pyrene motif passing through the 2- and 7-
positions, perpendicular to the molecular plane, which mean the sub-
stituent will not involve in the excitations between the frontier orbitals.
For 1N, the phenyl ring is bonded with pyrene through the 2-position of
pyrene, and the orbital coefficients of the frontier orbitals are relative
small on the phenyl group. However, the N atom is clearly involved in
the frontier orbitals since it is bonded at the 1-position of pyrene for
[
[
[14] S. Zhang, Z. Liu, Q. Fang, Synthesis, structures, and optoelectronic properties of
pyrene-fused thioxanthenes, Org. Lett. 19 (2017) 1382–1385.
15] K. Takamatsu, K. Hirano, T. Satoh, M. Miura, Synthesis of carbazoles by copper-cata-
[
lyzed intramolecular C−H/N−H coupling, Org. Lett. 16 (2014) 2892–2895.
[16] W.D. Guerra, R.A. Rossi, A.B. Pierini, S.M. Barolo, “Transition-metal-free” synthesis of
carbazoles by photostimulated reactions of 2′-halo[1,1′-biphenyl]-2-amines, J. Org.
Chem. 80 (2015) 928–941.
17] D.-Y. Goo, S.K. Woo, One-pot synthesis of carbazoles via tandem C–C cross-coupling
and reductive amination, Org. Biomol. Chem. 14 (2016) 122–130.
18] I.T. Alt, B. Plietker, Iron-catalyzed intramolecular C(sp2)–H amination, Angew.
Chem. Int. Ed. 55 (2016) 1519–1522.
19] C. Suzuki, K. Hirano, T. Satoh, M. Miura, Direct synthesis of N–H carbazoles via
iridium(III)-catalyzed intramolecular C−H amination, Org. Lett. 17 (2015)
1
N. Vice versa, in the case of 2N, phenyl is more involved in the frontier
[
[
[
orbitals instead of N atom. Combined with the experimental data, it
seems that the position of N atom play much important role than phenyl
to increase the electron-donating ability in these phenalenocarbazoles
cases.
1597–1600.
[
20] H. Gao, Q.-L. Xu, M. Yousufuddin, D.H. Ess, L. Kürti, Rapid synthesis of fused N-het-
erocycles by transition-metal-free electrophilic amination of arene C–H bonds,
Angew. Chem. Int. Ed. 53 (2014) 2701–2705.
4
. Conclusions
Two regioisomeric phenalenocarbazoles, named as N-bridged
[21] J. Wu, X. Chen, Y. Xie, Y. Guo, Q. Zhang, G.-J. Deng, Carbazole and triarylpyrrole syn-
thesis from anilines and cyclohexanones or acetophenones under transition-metal-
free condition, J. Org. Chem. 82 (2017) 5743–5750.
pyrene-phenyl carbazole derivatives, have been synthesized by direct
reductive cyclization of 2′-Nitrophenyl-pyrene isomers. The compari-
son between these N bridged phenalenocarbazoles and earlier reported
S-bridged PTA indicate that phenalenocarbazoles will greatly extend
the conjugation as presented spectral red-shifts and keep good quan-
tum yield and electronical properties. Considering the ground potential
[
22] M. Bhanuchandra, K. Murakami, D. Vasu, H. Yorimitsu, A. Osuka, Transition-metal-
free synthesis of carbazoles and indoles by an S Ar-based “aromatic metamorpho-
N
sis” of thiaarenes, Angew. Chem. Int. Ed. 54 (2015) 10234–10238.
23] A.W. Freeman, M. Urvoy, M.E. Criswell, Triphenylphosphine-mediated reductive cy-
clization of 2-nitrobiphenyls: a practical and convenient synthesis of carbazoles, J.
Org. Chem. 70 (2005) 5014–5019.
[

116
C.-E. Luo et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 194 (2018) 111–116
[
24] D.N. Coventry, A.S. Batsanov, A.E. Goeta, J.A.K. Howard, T.B. Marder, R.N. Perutz, Se-
lective Ir-catalysed borylation of polycyclic aromatic hydrocarbons: structures of
naphthalene-2,6-bis(boronate), pyrene-2,7-bis(boronate) and perylene-2,5,8,11-
tetra(boronate) esters, Chem. Commun. (2005) 2172–2174.
25] K. Yamamoto, E. Shouji, H. Nishide, E. Tsuchida, Aryl sulfide bond formation using
the sulfoxide-acid system for synthesis of PPS via Poly(sulfonium cation) as a Pre-
cursor, J. Am. Chem. Soc. 115 (1993) 5819–5820.
[28] G. Gritzner, J. Kuta, Recommendations on reporting electrode potentials in nonaque-
ous solvents, Pure Appl. Chem. 56 (1984) 461–466.
[29] J. Pomrnerehne, H. Vestweber, W. Guss, R.F. Mahrt, H. Bӓssler, M. Porsch, J. Daub, Ef-
ficient two layer leds on a polymer blend basis, Adv. Mater. 7 (1995) 551–554.
[30] X. Feng, J.-Y. Hu, C. Redshaw, T. Yamato, Functionalization of pyrene to prepare lu-
minescent materials−typical examples of synthetic methodology, Chem. Eur. J. 22
(2016) 11898–11916.
[
[
26] L.-X.
Poly(phenylenesu1fidephenylenamine)
polyphenylenesulfide with polyaniline, Angew. Chem. Int. Ed. 35 (1996)
495–1497.
Wang,
T.
Soczka-Guth,
E.
Havinga,
K.
Müllen,
[31] T.M. Figueira-Duarte, K. Müllen, Pyrene-based materials for organic electronics,
(PPSA)-the
“compound”
of
Chem. Rev. 111 (2011) 7260–7314.
[32] A.G. Crawford, A.D. Dwyer, Z. Liu, A. Steffen, A. Beeby, L.-O. Palsson, D.J. Tozer, T.B.
Marder, Experimental and theoretical studies of the photophysical properties of 2-
and 2,7-functionalized pyrene derivatives, J. Am. Chem. Soc. 133 (2011)
13349–13362.
1
[27] J. Lee, J. Park, Synthesis and electroluminescence of novel pyrene-fused chromo-
phores, Org. Lett. 17 (2015) 3960–3963.