Photooxygenations and Self-Sensitizations of Naphthylamines: Efficient Access to Iminoquinones

Article abstract of DOI:10.1155/2018/9180671

A series of spiro [fluorene-9,7′-dibenzo[c,h]acridine]-5′-one (SFDBAO) derivatives have been concisely and cleanly obtained by exposure to sunlight without external photosensitizers in the higher yields than that when using a UV lamp. An interesting autocatalyst and self-sensitive procedure have been proposed to explain the effective photooxygenation. SFDBAO derivatives exhibit the continuous π-stacks in single-crystal and electron-withdraw properties with red light-emitting and photovoltaic properties.

Full text of DOI:10.1155/2018/9180671

Hindawi
Journal of Chemistry
Volume 2018, Article ID 9180671, 9 pages
https://doi.org/10.1155/2018/9180671
Research Article
Photooxygenations and Self-Sensitizations of Naphthylamines:
Efficient Access to Iminoquinones
Ying Wei, Lei Tang, Chunxiao Zhong, Xinmiao Xie, Pengju Sun, Chen Sun, He Zhang,
Xiang-ping Zheng, Xiuli Wang, and Ling-hai Xie
Centre for Molecular Systems and Organic Devices (CMSOD), Key Laboratory for Organic Electronics and Information Displays
and Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation
Center for Advanced Materials (SICAM), Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing
210023, China
Correspondence should be addressed to Ling-hai Xie; iamlhxie@njupt.edu.cn
Received 10 February 2018; Accepted 20 March 2018; Published 20 May 2018
Academic Editor: Sedat Yurdakal
Copyright © 2018 Ying Wei et al. ,is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
A series of spiro [fluorene-9,7′-dibenzo[c,h]acridine]-5′-one (SFDBAO) derivatives have been concisely and cleanly obtained
by exposure to sunlight without external photosensitizers in the higher yields than that when using a UV lamp. An interesting
autocatalyst and self-sensitive procedure have been proposed to explain the effective photooxygenation. SFDBAO deriva-
tives exhibit the continuous π-stacks in single-crystal and electron-withdraw properties with red light-emitting and
photovoltaic properties.
temperature and requires irradiation by sunlight in order
to proceed, is sufficient for achieving iminoquinones
with synthetically useful results. In general, most photo-
oxygenations require the effective photocatalysis or pho-
tosensitizers such as, Ir or Ru complexes [11], rose bengal
[12–14], porphyrins [15], 9-mesityl-10-methylacridinium
[16, 17], inorganic TiO2 [18, 19], or organic molecule
[20]. However, our visible light mediates photooxygenation
of naphthylamines with the advantages of high chemo-
selectivity without any external photosensitizers. In this
reaction, naphthylamines play a dual role of providing both
photosensitizer and substrate, and O2 functions as triplet
state trapping agent and oxygen sources.
Spirofluorenes are widely used in semiconductors, including
OLEDs, PLEDs, solar cells, fuel cells, memories, and so on [21].
Common electron-rich spirofluorenes include spirobifluorenes,
spirofluoreneacridines, spirobisindane, spirofluorenexanthenes,
spiropyran, and so on. Till now, electron-deficient spirofluorenes
have not been synthesized and reported because of the lack of
convenient and efficient synthetic route. ,erefore, we describe
a novel strategy for the one-pot synthesis of electron-deficient
1. Introduction
Iminoquinones constitute the core structures of many naturally
occurring compounds and display important antineoplastic,
antifungal, and antibacterial activities (Figure 1) [1–4]. Com-
monly used approaches for the construction of iminoquinones
include (i) metal catalysis [5–7], (ii) photosynthesis by UV
lamps and photosensitizers [7], (iii) 2-iodoxybenzoic acid [IBX,
1-hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide] oxidation [8, 9],
and (iv) Dess–Martin periodinane [DMP, 1,1,1-triacetoxy-
1,1-dihydro-1,2-benziodoxol-3(1H)-one]-mediated oxidative re-
action [10]. Although the aforementioned elegant methods
appear to be general and efficient, further development of the
low-cost and eco-friendly methods that allow the facile assembly
of highly functionalized iminoquinone from readily available and
simple starting materials is still required, because they have wide
range of applications in medicine and biology.
Herein, we report a photochemical strategy for gener-
ating excited state species from naphthylamines, which does
not rely upon any metal- or organic-based photoredox
catalysts (Scheme 1). ,e reaction, which occurs at ambient

2
Journal of Chemistry
NH
O
N
N
O
NH2
O
H
N
N
N
O
O
N
O
O
O
R
R
N
N
N
R
NH2
N
O
O
O
Figure 1: Bioactive molecules containing iminoquinone constitute the core structures.
NH2
N
NH2
O
IBX
H
N
N
R
R
Air
O
(a)
(b)
Scheme 1: Photooxygenations and self-sensitizations of naphthylamine strategies. (a) Previous work [4]. (b) Our work.
5H-spiro[dibenzo[c,h]a-crdine-7,9′-ꢀuoren]-5-one (SFDBAO)
2.2. Syntheses of the Intermediates and the Target Compounds
through a photooxygenation-initiated cascade process.
2.2.1. General Procedure for Preparation of 2 and 3. In
a round bottom ꢀask, compound 1 (2 mmol) was dissolved
in MeCN (400 mL) and the mixture was stirred in the
sunlight irradiation under air atmosphere for 6 hours to
produce compound 2. -e crude product was puri¥ed by
ꢀash column chromatography (silica gel, CH2Cl2/petroleum
ether, 1: 3) to give puri¥ed products.
2. Experimental
2.1. Reagents and Instruments. All the reagents used were of
analytical pure. -e UV lamp irradiation is carried out indoors
by a household 23 W compact ꢀuorescent light (CFL) bulb. 1H
and 13C NMR spectra were performed on a Bruker 400 MHz
spectrometer in CDCl3 or DMSO-d6 with tetramethylsilane
(TMS) as the interval standard. Mass spectra were recorded on
a Shimadzu GCMS-QP2010 plus equipped with DB-5 ms
column or a Shimadzu AXIMA-CFR plus spectrometer. For the
MALDI-TOF MS spectra, the spectra were recorded in reꢀective
mode, and substrates were used. Molecular weights of the
samples were measured by gel permeation chromatography
(GPC) on a Shimadzu LC-20A HPLC system equipped with
7911GP-502 and GPNXC columns. Elemental analyses were
carried out in an Elementar Analysensysteme GmbH-vario EL
III element analyzer. Absorption spectra were measured with
a Shimadzu UV-3600 spectrometer at 25°C, and emission
spectra were recorded on a Shimadzu RF-5301(PC)S lumines-
cence spectrometer. Cyclic voltammetric (CV) studies were
conducted using a CHI660C electrochemical workstation in
a typical three-electrode cell with a platinum sheet working
electrode, a platinum wire counter electrode, and a silver/silver
nitrate (Ag/Ag+) reference electrode. X-ray crystallographic data
were collected at 293 K on a P4 Bruker di¤ractometer equipped
with a ¥ne-focus sealed tube and a rotating anode utilizing
(1) Spiro[uorene-9,7′-dibenzo[c,h]acridi-ne]-5′-one (SFDBAO,
2a). -is compound was prepared following the general
procedures by applying 1a (0.862 g, 2 mmol) to give 2a
(0.69 g, 1.56 mmol) as a red solid with the yield of 78%. GC-
MS (EI-m/z) calcd for C33H19NO+ [M]+ 445.15, found 445.00.
1H NMR (400 MHz, CDCl3, ppm): δ 9.28–9.26 (d, J ꢀ 8.4 Hz,
1H), 9.06–9.04 (d, J ꢀ 8.8 Hz, 1H), 8.14–8.12 (d, J ꢀ 8.8 Hz, 1H),
7.87–7.84 (m, 3H), 7.76–7.73 (t, J ꢀ 9.2 Hz, 2H), 7.68–7.64
(t, J ꢀ 8.4 Hz, 1H), 7.61–7.57 (t, J ꢀ 7.6 Hz, 1H), 7.55–7.53
(d, J ꢀ 8.4 Hz, 1H), 7.45–7.41 (t, J ꢀ 7.6 Hz, 2H), 7.22–7.18
(t, J ꢀ 7.6 Hz, 2H), 7.04–7.02 (d, J ꢀ 7.6 Hz, 2H), 6.57–6.55
(d, J ꢀ 8.8 Hz, 1H), 6.04 (s, 1H). 13C NMR (100 MHz, CDCl3): δ
184.5, 151.7, 150.0, 145.4, 140.8, 137.8, 135.6, 133.6, 132.7,
132.2, 131.4, 130.8, 130.3, 128.9, 128.8, 128.6, 127.7, 127.2,
126.7, 125.9, 125.3, 124.8, 124.6, 123.8, 120.7, 57.7. Anal. Calcd
for C33H19NO: C, 89.04; H, 4.30; N, 3.15. Found: C, 89.07; H,
4.28; N, 3.18.
(2) 9′-Chlorospiro[uorene-9,7′-dibenzo[c,h]acridine]-5′-one
(ClSFDBAO, 2b). -is compound was prepared following
the general procedures by applying 1a (0.862 g, 2 mmol) and
CCl4 (400 mL). Puri¥ed by ꢀash column chromatogra-
phy using CH2Cl2 : petroleum ether ꢀ 1 : 3 to give 2b
(0.785 g, 1.64 mmol) as a red solid with the yield of 82%.
GC-MS (EI-m/z) calcd for C33H18ClNO+ [M]+ 479.11,
˚
graphite-monochromated Mo Kα radiation (λ ꢀ 0.71073 A).
Data processing was carried out using the program SAINT,
while the program SADABS was utilized for the scaling of
di¤raction data, the application of a decay correction, and an
empirical absorption correction based on redundant reꢀec-
tions. -e structures were solved by direct methods and re-
¥ned against F2 with the full-matrix, least-squares methods
using SHELXS-97 and SHELXL-97, respectively. Column
chromatography puri¥cation was carried out using the silica
gel (200–300 mesh).
1
found 479.05. H NMR (400 MHz, CDCl3, ppm): δ 9.32–
9.29 (d, J ꢀ 7.6 Hz, 1H), 9.02–9.00 (d, J ꢀ 8.0 Hz, 1H), 8.21–
8.19 (d, J ꢀ 8.4 Hz, 1H), 8.13–8.11 (d, J ꢀ 7.6 Hz, 1H), 7.88–7.86
(d, J ꢀ 7.6 Hz, 3H), 7.84–7.79 (m, 1H), 7.72–7.66 (m, 2H),

Journal of Chemistry
3
Table 1: Optimization of the reaction conditionsa.
7.47–7.43 (t, J � 7.4 Hz, 2H), 7.24–7.20 (t, J � 7.4 Hz, 2H),
7.04–7.02 (d, J � 7.6 Hz, 2H), 6.64 (s, 1H), 6.02 (s, 1H). 13C
NMR (100 MHz, CDCl3, ppm): 13C NMR (100 MHz, CDCl3):
δ 184.4, 151.1, 150.3, 145.0, 140.7, 137.0, 135.4, 133.8, 133.2,
132.8, 131.4, 130.9, 130.9, 130.4, 129.2, 129.0, 128.9, 127.9,
127.7, 126.0, 125.3, 124.8, 124.4, 124.2, 120.9, 57.5. Anal. Calcd
for C33H18ClNO: C, 82.73; H, 3.79; N, 2.92. Found: C, 82.76;
H, 3.77; N, 2.90.
Entry
Solvent
Irradiation Gas Time (h) Yield (%)b
H
N
H
N
N
O
O
Solvent, r.t.
O
1a
2a
3
(3) 2-Bromospiro[fluorene-9,7′-dibenzo[c,h]acridine]-5′-one
(BrSFDBAO, 2c). ,is compound was prepared following
the general procedures by applying 1c (1.02 g, 2 mmol) to
give 2c (0.765 g, 1.46 mmol) as a red solid with the yield of
73%. GC-MS (EI-m/z) calcd for C33H18BrNO+ [M]+
523.06, found 522.85. 1H NMR (400 MHz, CDCl3, ppm): δ
9.27–9.25 (d, J � 8.4 Hz, 1H), 9.05–9.03 (d, J � 7.6 Hz, 1H),
8.14–8.12 (d, J � 8.4 Hz, 1H), 7.89–7.95 (t, J � 7.6 Hz, 1H),
7.84–7.82 (d, J � 7.6 Hz, 1H), 7.80–7.75 (m, 2H), 7.75–7.67
(m, 2H), 7.62–7.54 (m, 3H), 7.46–7.42 (t, J � 7.6 Hz, 1H),
7.25–7.21 (t, J � 7.4 Hz, 1H), 7.14 (s, 1H), 7.03–7.01 (d,
J � 7.6 Hz, 1H), 6.55–6.53 (d, J � 8.4 Hz, 1H), 6.02 (s, 1H).
13C NMR (101 MHz, CDCl3): δ 184.4, 153.5, 151.5, 149.9,
144.4, 139.7, 139.7, 137.8, 135.5, 133.7, 132.9, 132.2, 131.9,
131.3, 130.9, 130.5, 130., 129.4, 128.9, 128.0, 127.8, 127.7,
127.4, 126.9, 126.0, 125.4, 124.9, 124.4, 123.8, 122.2, 122.1,
120.7, 57.5. Anal. Calcd for C33H18BrNO: C, 75.78; H, 3.47;
N, 2.68. Found: C, 75.81; H, 3.45; N, 2.66.
1
CCl4
CCl4
UV lampc
Air
Air
Air
Air
Air
Air
Air
Air
Air
O2
24
6
6
6
6
6
6
6
6
3
6
40d
82d
76
30
10
20
50
78
nr
2
Sunlight
Sunlight
Sunlight
Sunlight
Sunlight
Sunlight
Sunlight
Dark
3
Acetone
MeOH
THF
4
5
6
DMF
7
Toluene
MeCN
MeCN
MeCN
MeCN
8
9e
10
11
Sunlight
Sunlight
83
nr
N2
aReactions were carried out with 1a (2.0 mmol) in solvent (400 mL) for 6 h.
c
d
e
bIsolated yields. 365 nm. With isolated yield of 2b. At 80°C.
(6) 5H-spiro[dibenzo[c,h]acridine-7,9′-fluorene]-5,6(14H)-dione
(SFDBAOO, 3). ,is compound was prepared following the
general procedures by applying 1a (0.862 g, 2 mmol) and ac-
etone as solvent to give 3 (0.085 g, 0.184 mmol) as a red solid
(4) 2,7-Dibromospiro[fluorene-9,7′-dibenzo[c,h]acridine]-5′-
one (DBrSFDBAO, 2d). ,is compound was prepared fol-
lowing the general procedures by applying 1d (1.18 g, 2 mmol)
to give 2d (0.844 g, 1.40 mmol) a red solid with the yield of
1
with the yield of 9%. H NMR (400 MHz, CDCl3, ppm): δ
9.23–9.21 (d, J � 8.0 Hz, 1H), 9.18–9.16 (d, J � 8.0 Hz, 1H),
8.19–8.17 (d, J � 8.0 Hz, 1H), 7.93–7.87 (m, 3H), 7.74–7.66 (m,
3H), 7.57–7.53 (m, 1H), 7.44–7.40 (m, 3H),7.21–7.17 (t,
J � 7.6 Hz, 2H), 7.11–7.09 (d, J � 7.6 Hz, 2H), 7.03 (s, 1H),
6.40–6.38 (d, J � 8.4 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ
179.4, 150.6, 149.7, 149.5, 142.0, 137.4, 136.2, 133.6, 133.3, 132.0,
130.4, 129.6, 128.8, 128.3, 128.0, 127.6, 127.6, 127.0, 126.6, 126.1,
126.0, 124.8, 124.5, 123.8, 119.9, 116.1, 54.9. MALDI-TOF-MS
calcd for C33H19NO2: 461.49 [M+], Found: 462.14.
1
70%. H NMR (400 MHz, CDCl3, ppm): δ 9.26–9.24 (d,
J � 8.4 Hz, 1H), 9.05–9.03 (d, J � 7.6 Hz, 1H), 8.15–8.13 (d,
J � 8.8 Hz, 1H), 7.90–7.86 (t, J � 7.6 Hz, 1H), 7.79–7.76 (m,
2H), 7.70–7.68 (d, J � 8.4 Hz, 3H), 7.64–7.58 (m, 2H), 7.57–
7.55 (dd, J � 8.2, 1.8 Hz, 2H), 7.14–7.14 (d, J � 1.6 Hz, 2H),
6.53–6.51 (d, J � 8.8 Hz, 1H), 6.01 (s, 1H). 13C NMR (100 MHz,
CDCl3, ppm): δ 184.3, 153.4, 149.7, 143.4, 138.6, 137.7, 135.3,
133.8, 133.0, 132.2, 132.1, 131.3, 131.0, 130.8, 130.6, 128.1,
127.8, 127.5, 127.1, 126.5, 126.0, 125.5, 124.2, 123.9, 122.8,
122.1, 57.3. Anal. Calcd for C33H17Br2NO: C, 65.95; H, 2.85;
N, 2.33. Found: C, 65.92; H, 2.86; N, 2.35.
2.2.2. Syntheses of 2-(Biophen-2-yl)-spiro [Fluorene-9,7′-
dibenzo[c,h]acridine]-5′-one (TSFDBAO). A mixture of 2c
(0.523 g, 1.0 mmol), 2-thiopheneboronic acid 4 (0.154 g,
1.2 mmol), Pd(PPh3)4 (122 mg, 0.10 mmol), K2CO3 (2.0 M
aqueous solution, 3.5 mL), and toluene (5 mL)/THF (5 mL)
was stirred at 90°C under nitrogen atmosphere for 24 h. After
it was cooled to room temperature, 200 mL of CH2Cl2 was
added to the reaction mixture. ,e organic portion was
separated and washed with brine before dried over anhy-
drous MgSO4. ,e solvent was evaporated off, and the solid
residues were purified by flash column chromatography using
CH2Cl2 : petroleum ether � 1 : 3 to afford TSFDBAO (0.437 g,
(5) (Z)-4-(Naphthalen-1-ylimino)naphthalen-1(4H)-one (NINO,
2e). ,is compound was prepared following the general
procedures by applying 1e (0.538 g, 2 mmol) to give 2e
(0.463 g, 1.64 mmol) as a red solid with the yield of 82%. GC-
MS (EI-m/z) calcd for C20H13NO+ [M]+ 283.10, found 282.95.
1H NMR (400 MHz, CDCl3, ppm): δ 8.68–8.66 (d, J � 8.4 Hz,
1H), 8.23–8.21 (d, J � 7.6 Hz, 1H), 7.91–7.88 (d, J � 8.8 Hz,
2H), 7.83–7.79 (t, J � 7.6 Hz, 1H), 7.75–7.73 (d, J � 8.0 Hz, 2H),
7.57–7.53 (t, J � 7.6 Hz, 1H), 7.51–7.47 (t, J � 7.8 Hz,2H),
7.26–7.23 (d, J � 10.4 Hz, 1H), 6.79–6.78 (d, J � 7.2 Hz, 1H),
6.69–6.66 (d, J � 10.4 Hz, 1H). 13H NMR (100 MHz, CDCl3,
ppm): δ 185.6, 155.4, 146.2, 134.7, 134.1, 134.0, 133.1, 131.4,
131.4, 130.5, 127.9, 127.1, 126.7, 126.2, 126.1, 125.7, 125.5,
124.0, 114.7. Anal. Calcd for C20H13NO: C, 84.78; H, 4.63; N,
4.94. Found: C, 84.95; H, 4.59; N, 4.82.
1
0.83 mmol) as red solids with the yield of 83%. H NMR
(400 MHz, CDCl3, ppm): δ 9.29–9.27 (d, J � 8.4 Hz, 1H), 9.08
9.05 (d, J � 8.4 Hz, 1H), 8.14–8.12 (d, J � 8.4 Hz, 1H), 7.87–7.83
(m, 3H), 7.78–7.75 (t, J � 8.0 Hz, 2H), 7.71–7.69 (d, J � 7.2 Hz,
1H), 7.69 7.66 (t, J � 8.4 Hz, 1H), 7.61–7.57 (t, J � 8.4 Hz, 1H),
7.57–7.55 (d, J � 8.4 Hz, 1H), 7.43–7.39 (t, J � 8.0 Hz, 1H), 7.25
(s, 1H), 7.19–7.17 (d, J � 7.6 Hz, 1H), 7.17–7.15 (m, 2H),

4
Journal of Chemistry
SFDBAOO, 3
CISFDBAO, 2b
(a)
(b)
(c)
Figure 2: Single-crystal X-ray structures of 2b and 3 and the packing structure of 2b.
H
7.00–6.98 (d, J ꢀ 7.6 Hz, 1H), 6.97–6.95 (m, 1H), 6.62–6.60
(d, J ꢀ 8.4 Hz, 1H), 6.09 (s, 1H). 13C NMR (100 MHz, CDCl3,
ppm): δ 184.5, 152.5, 152.2, 149.9, 145.0, 143.6, 140.3, 140.0,
137.8, 135.6, 135.2, 133.7, 132.8, 132.2, 131.4, 130.8, 130.5,
130.4, 128.9, 128.7, 128.5, 128.0, 127.8, 127.3, 126.8, 126.7,
126.0, 125.3, 125.1, 124.7, 124.7, 123.8, 123.5, 122.2, 121.1,
120.7, 57.7. Anal. Calcd for C37H21NOS: C, 84.30; H, 4.02; N,
2.66. Found: C, 84.32; H, 4.01; N, 2.68.
N
N
R
R
CH3CN, r.t.
N
O
1
2
N
N
Cl
O
O
O
Br
2a (78%)
2b (82%)
2c (73%)
2.2.3. Syntheses of 2,7-Di(thiophen-2-yl)-spiro [Fluorene-9,7′-
dibenzo[c,h]acridine]-5′-one (DTSFDBAO). A mixture of
2d (0.60 g, 1.0 mmol), 2-thiopheneboronic acid 4 (0.282 g,
3.0 mmol), Pd(PPh3)4 (245 mL, 0.20 mmol), K2CO3 (2.0 M
aqueous solution, 7.2 mL), and toluene (5 mL)/THF (5 mL)
was stirred at 90°C under nitrogen atmosphere for 24 h.
After it was cooled to room temperature, 200 mL of CH2Cl2
was added to the reaction mixture. -e organic portion was
separated and washed with brine before dried over anhy-
drous MgSO4. -e solvent was evaporated o¤, and the solid
residues were puri¥ed by ꢀash column chromatography
using CH2Cl2 : petroleum ether ꢀ 1 : 3 to a¤ord DTSFDBAO
(0.487 g, 0.80 mmol) as red solids with the yield of 80%. 1H
NMR (400 MHz, CDCl3, ppm): δ 9.31–9.29 (d, J ꢀ 8.4 Hz,
1H), 9.09–9.07 (d, J ꢀ 8.4 Hz, 1H), 8.14–8.12 (d, J ꢀ 7.6 Hz,
1H), 7.90–7.84 (m, 3H), 7.80–7.60 (t, J ꢀ 8.0 Hz, 2H),
7.70–7.67 (m, 3H), 7.62–7.56 (m, 2H), 7.20–7.20 (d, J ꢀ
1.6 Hz, 2H), 7.19–7.18 (d, J ꢀ 5.2 Hz, 2H), 7.16–7.15 (d, J ꢀ
3.6 Hz, 2H), 6.97–6.94 (m, 2H), 6.66–6.64 (d, J ꢀ 8.4 Hz, 1H),
6.13 (s, 1H). 13C NMR (100 MHz, CDCl3, ppm): δ 184.5,
N
HN
N
HN
O
Br
O
Br
O
O
2d (70%)
2e (82%)
2f (0%) 2g (0%)
Scheme 2: Scope of the iminoquinones. aReactions were carried out
with 1 (2.0 mmol) in MeCN (400 mL) for 6 h. Isolated yields.
b
153.1, 149.9, 144.7, 143.6, 139.5, 137.7, 135.5, 135.2, 133.7,
132.8, 132.2, 131.4, 130.9, 130.9, 130.5, 128.1, 128.0, 127.8,
127.3, 126.9, 126.7, 126.0, 125.4, 125.1, 124.8, 123.8, 123.6,
122.0, 121.1, 57.5. Anal. Calcd for C41H23NOS2: C, 80.84; H,
3.81; N, 2.30. Found: C, 80.86; H, 3.82; N, 2.28.
3. Results and Discussion
Initially, our explorations toward an photooxygenation
protocol under mild reaction conditions focused on the

Journal of Chemistry
5
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0.6
0.4
0.2
0.0
300
400
500
600
300
400
500
600
700
Wavelength (nm)
Wavelength (nm)
10 min
100 min
SFDBA
SFDBAO
20 min
40 min
60 min
80 min
120 min
140 min
160 min
180 min
(a)
(b)
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
300
400
500
Wavelength (nm)
600
700
300
400
500
600
700
Wavelength (nm)
490 nm 10 min
490 nm 20 min
490 nm 40 min
490 nm 60 min
490 nm 80 min
490 nm 100 min
490 nm 120 min
490 nm 140 min
490 nm 160 min
490 nm 180 min
365 nm 10 min
365 nm 20 min
365 nm 40 min
365 nm 60 min
365 nm 80 min
365 nm 100 min
365 nm 120 min
365 nm 140 min
365 nm 160 min
365 nm 180 min
(c)
(d)
Figure 3: (a) -e absorption spectra of SFDBA and SFDBAO. Absorption spectra of 1a at di¤erent reaction times: (b) under the sunlight,
(c) under the 365 nm UV lamp, and (d) under 490 nm UV lamp.
reaction of 14H-spiro- [dibenzo[c,h]acridine-7,9′-ꢀuorene]
(SFDBA, 1a) (Table 1). First, the reaction of 1a was pur-
posively carried out in CCl4 by exposure to UV irradiation of
365 nm for 24 h, giving the chloro-substituted oxidative
product (ClSFDBAO) 2b in 40% yield, whereas the SFDBAO
product 2a was not observed (entry 1). -e structure of 2b
was con¥rmed unambiguously by X-ray single-crystal dif-
fraction (Figure 2). It is exciting that the conversion yield of
2b was improved up to 82% by exposure to sunlight at room
temperature in CCl4 (entry 2). A possible mechanism for the
formation of ClSFDBAO (2b) is depicted in Figure S6 (see
Supplementary Materials). When acetone was used as the
solvent and conducted at room temperature, the desired
product (SFDBAO) 2a was obtained in 76% yield, and 9%
of 5H-spiro[dibenzo[c,h] acridine-7,9′-ꢀuorene]-5,6(14H)-
dione (SFDBAOO) 3 as a by-product was detected (entry 3).
-e structure of 3 was con¥rmed unambiguously by X-ray
single-crystal di¤raction (Figure 2). Solvent screening in-
dicates that MeCN was the most e®cient. Other solvents
such as, MeOH, THF, DMF, and toluene gave relatively low

6
Journal of Chemistry
∗
Visible
light
N
R
R
N
H
∗
Visible
light
O
1
R
N
H
N
R
O
O2
O
N
O2
+
N
H
R
O2
O2
I
R
Resonance
O
+
N
H
[4 + 2]
O2
O2
O
R
N
N
R
R
HN
II
H2O
OH
O
R
2
III
IV
Scheme 3: -e proposed triplet sensitization mechanism.
N
N
10 mol% Pd(PPh3)4
2 eq K2CO3
2 eq KF
THF/toluene (1:1)
90°C, N2
HO
O
(1)
O
+
B
S
HO
Br
S
2c (1 mmol)
4 (1.2 eq)
TSFDBAO (83%)
N
(a)
N
10 mol% Pd(PPh3)4
2 eq K2CO3
2 eq KF
THF/toluene (1:1)
90°C, N2
HO
O
+
O
B
(2)
S
HO
Br
Br
S
S
2d (1 mmol)
4 (2.2 eq)
DTSFDBAO (80%)
(b)
Scheme 4: Synthesis of the thiophene-substituted SFDBAO D-A (p-n)-type organic semiconductors.
yields of 2a (entries 4–8). No target compound 2a was ob-
tained in the dark when heating up more than 80°C (entry 9).
Additionally, no product 2a was obtained in N2 atmosphere
(entry 11), indicating oxygen in the atmosphere participated
in the visible-light-mediated photooxygenation of 1a. -is
result was further supported by the control experiments using
the puri¥ed O2 source to give 2a in 83% yield (entry 10).
Moreover, a write-once, read-many (WORM) type memory
device based on SFDBAO derivative nanosheets as electro-
active layers shows an ON/OFF ratio of 6.0 ×104, accom-
panied by an interesting photoswitching behavior. -e results
presented have shown that SFDBAO derivatives are prom-
ising electroactive materials for the memory device applica-
tion [22, 23]. Compared with our previous reports, further
study of the conditions and the scope of this reaction were
conducted in detail.
Under the optimized conditions (Table 1, entry 8), a range of
reactions were performed with various substrates 1 (Scheme 2).
-e reactions of spiroꢀuoreneacridines proceeded smoothly to
a¤ord the corresponding photooxygenation products 2(a–d) in
good to excellent yields (70–82%). -en, di (naphthalen-1-yl)
amine was compatible with this reaction, a¤ording the desired
product 2e in 82% yields. To our disappointment, no desired
products were obtained when naphthylamine and anilines were
employed in the present reaction system (see Supplementary
Materials Figure S6).
Chemical structures of the SFDBAO derivatives were
1
unambiguously con¥rmed by GC-MS, H and 13C NMR,

Journal of Chemistry
7
300
400
500
600
700
1200
1000
800
600
400
200
0
150
100
50
1.0
0.8
0.6
0.4
0.2
0.0
0
–50
–100
–150
–2
–1
0
1
2
300
400
500
600
700
Voltage (V)
Wavelength (nm)
Fe(C5H5)2
SFDBAO
TSFDBAO
DTSFDBAO
SFDBAO-UV
SFDBAO-PL
TSFDBAO-UV
TSFDBAO-PL
DTSFDBAO-UV
DTSFDBAO-PL
(a)
(b)
Figure 4: -e photophysical and electrochemical properties of SFDBAO. (a) UV-vis electronic absorption spectra and photoluminescence
spectra. (b) Reductive and oxidative cyclic voltammograms, 0.1 M n-Bu4NPF6 in THF (reduction) and 0.1 M n-Bu4NPF6 in CH2Cl2
(oxidation), were used as supporting electrolytes. A platinum sheet electrode was used as the working electrode; the scanning rate was
100 mV/s, where E+ (Fc/Fc) is about 0.03 V.
X-ray crystallography, and elementary analyses. -e single-
crystal X-ray di¤raction structures of ClSFDBAO (2b)
and SFDBAOO (3) are shown in Figure S3–S5 and
Table S1. ClSFDBAO and SFDBAOO from a mixture of
dichloromethane/alcohol and a mixture idines in ClSFDBAO
are incompletely perpendicular with ꢀuorene plane according
to X-ray crystallography, obviously di¤erent from spirobi-
ꢀuorenes. ClSFDBAO exhibit well-de¥ned consecutive inter-
molecular π-stacked motifs among adjacent dibenzoacridines
On the basis of all the results described above, a plausible
and preliminary mechanism has been proposed, as depicted
in Scheme 3. In the self-sensitizations cycle, naphthylamines
is converted to the excited singlet state under the sunlight
irradiation. Subsequently, the excited triplet singlet state is
formed through intramolecularly intersystem crossing (ISC)
of the excited singlet state. -e triplet energy of the naph-
thylamines can be transferred to the ground state oxygen
molecule to produce singlet oxygen to close this catalytic
cycle. After that, an electron transfer of singlet oxygen from
1 occurs, leading to the formation of radical cation species
I/II. -en, a [4 + 2] cycloaddition is given to intermediate II,
and the O–O bond cleavage of intermediate III led to in-
termediate IV, which was readily oxidized by dioxygen to
produce the desired iminoquinones 2 [24–26].
In order to explore the photoelectric property of n-type
spiro-based organic semiconductors SFDBAO, we smoothly
synthesized the thiophene-substituted SFDBAO D-A (p-n)-
type organic semiconductors, which will become important
monomers for low-bandgap π-conjugated polymers in solar
cells (Scheme 4). -e reactions of 2c and 2d with thiophen-
2-ylboronic acid 4 under Pd(PPh3)4 catalytic conditions gave
˚
with a close distance of 3.346 A in the molecular packing graph
(Figure 2), which is in the range of the distance of the
typical π-π stacking interactions relative to range over 3.4–
˚
3.8 A. -e closely interplanar distances are favorable for the
electron delocalization and the improvement of mobility in
organic ¥lms and devices.
To clarify the SFDBA and SFDBAO together as a pho-
tosensitive catalyst involved in the reaction leading to
SFDBAO, control experiments were performed (Figure 3).
-e optical absorption properties of the SFDBA and SFDBAO
were investigated by UV-vis absorption spectra as shown in
Figure 3. -e absorption spectra in dilute CHCl3 of SFDBA
and SFDBAO show absorption at 370 nm and 470 nm, re-
spectively. -erefore, we tested the absorption spectra of
2′-(thiophen-2-yl)- 5H-spiro[dibenzo[c,h]acridine-7,9′-ꢀuoren]-
SFDBA 1a at di¤erent reaction times under the sunlight, the
365 nm UV lamp, and the 490 nm UV lamp, respectively. As
a result, we found that the yield of SFDBAO increased
gradually with the increase of reaction time under the sunlight
and 490 nm UV lamp. However, the yield of SFDBAO in-
creased very slowly with the increase of reaction time under
the 365 nm UV lamp. -e experimental results indicate that
SFDBA acts as a photosensitive catalyst to induce the for-
mation of SFDBAO in the initial reaction period, and then,
SFDBAO also acts as another photosensitive catalyst accel-
erating the conversion together with SFDBA.
5-one (TSFDBAO) and 2′,7′-di(thiophen-2-yl) -5H-spiro
[dibenzo[c,h]acridine-7,9′-ꢀuoren]-5-one (DTSFDBAO) in
83% and 80% yields, respectively.
-e optical and electrochemical properties of the
SFDBAO, TSFDBAO, and DTSFDBAO were investigated by
UV-vis absorption spectra, photoluminescence (PL) spectra,
and cyclic voltammetry (CV), as shown in Figure 4 and
summarized in Table S2 (see Supplementary Materials). UV-
vis spectra exhibit the maximum absorption peak at 470 nm
for SFDBAO. SFDBAO with a red-yellow color about
565 nm. -iophene-substituted SFDBAO exhibit the new

8
Journal of Chemistry
electronic absorption bands at 322 nm for TSFDBAO and
353 nm for DTSFDBAO without the obvious change of PL
peaks, expect for the reduced emission intensity probably
owing to heavy atom effects of sulfur. ,e first turn-on
oxidation potentials of SFDBAO occur at 0.98 V (vs Fe+/Fe)
for SFDBAO, 0.96 V (vs Fe+/Fe) for TSFDBAO, and 0.71 V
for DTSFDBAO, respectively. ,ese results indicate that
DTSFDBAO has better electron-donating properties owing
to the introduction of the double thiophene groups. Fur-
thermore, all the SFDBAO derivatives exhibit the reversible
reduction processes with the similar onset first potential of
around −1.00 V (vs Fe+/Fe). ,eir LUMO energy levels are
estimated and determined from the onset of the reduction to
be −3.73 eV for SFDBAO, −3.78 eV for TSFDBAO, and
−3.77 eV for DTSFDBAO with regard to the energy level of
ferrocene (4.8 eV below vacuum), respectively. ,e lower
LUMO is probably assigned to the spiro-dibenzoacridine
moieties with the electron-withdrawing properties, which
are in the range of the LUMO energy level of acceptor material
in solar cells [27, 28]. ,eir bandages are 2.02 eV for SFDBAO,
1.95 V for TSFDBAO, and 1.71 V for DTSFDBAO, respectively.
,ese data suggest that the SFDBAOs are potential n-type
green organic semiconductors.
Foundation (NUPTSF) (NY215078, NY215172, NY217082),
and Six Peak Talents Foundation of Jiangsu Province (XCL-
CXTD-009).
Supplementary Materials
2–4 p.: general procedure for synthesis and analytical data of
spiro[fluorene-9,7′-dibenzo[c,h]acridine] (1a) and its derivatives
of 2-bromospiro[fluorene-9,7′-dibenzo[c,h]acridine] (1c), 2,7-
dibromospiro[fluorene-9,7′-dibenzo[c,h]acridine] (1d), and di
(naphthalen-1-yl)amine (1e). 4 p.: Figure S1: photograph about
this green reaction in different reaction times in sunlight: SFDBA
−1
1a in acetone solution (0.005 mol·L ). (a) 0 min; (b) 10 min; (c)
3 h. 5 p.: Figure S2: photographs of the color and emission
change of reaction solution of SFDBA 1a in the various solvents
−1
(0.005 mol·L ). (a) Before exposure to sunlight and shooting in
daylight. (b) Before exposure to sunlight and shooting under
UV lamp at 365 nm. From left to right the solvents are MeOH,
THF, DMF, acetone, CHCl3, toluene, and acetonitrile. 6-7 p.:
the crystal data of 2b and 3, 8 p.: Figure S6: GC-MS of the crude
product of 2f, and Figure S7: MALDI-TOF-MS of 3. 9–20 p.:
1H and 13C NMR spectra of products. 21 p.: H-NMR and
1
13C-NMR spectra of DTSFDBAO. CCDC 802655(2b) and
1821185(3) contain the supplementary crystallographic data for
this paper, and the data can be obtained free of charge from ,e
Cambridge Crystallographic Data Centre via http://www.ccdc.
cam.ac.uk/data_request/cif. (Supplementary Materials)
4. Conclusions
We have developed a green efficient access to iminoquinones
from naphthylamines based on the photooxygenation and
self-sensitizations, in which naphthylamines play a dual role
of providing both photosensitizer and substrate, and O2
functions as triplet state trapping agent and oxygen source.
Air atmosphere and sunlight irradiations are crucial con-
ditions of the photooxygenation reaction to obtain the high-
yield products. ,is sunlight-induced C-H activation gives
a kind of new n-type spiro-based organic semiconductors.
Further work on the application of SFDBAO-based mate-
rials is ongoing in our laboratory.
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