CF3-Inspired Synthesis of Air-Tolerant 9-Phosphaanthracenes that Feature Fluorescence and Crystalline Polymorphs

Article abstract of DOI:10.1002/asia.201701669

9-Phosphaanthracene (dibenzo[b,e]phosphorin, acridophosphine) has attracted interest as one of the heavier acenes. Herein, we demonstrate an efficient synthetic process that provides air-tolerant 1,8-bis(trifluoromethyl)-9-phosphaanthracenes. The sterically encumbered and electron-withdrawing trifluoromethyl (CF₃) groups are quite advantageous not only to stabilize the intrinsically unstable heavier unsaturated phosphorus atom but also to facilitate construction of the phosphinine skeleton based on a putative increase in aromaticity. The isolated 9-phosphaanthracenes allowed characterization of their fluorescence functionality and planar heteroanthracene frameworks. The crystal structures of 9-phosphaanthracenes are remarkably dependent on the aryl substituents at the 10 position; anthryl-substituted 9-phosphaanthracene showed unique polymorphs that induced different-colored crystals.

Full text of DOI:10.1002/asia.201701669

DOI: 10.1002/asia.201701669
Full Paper
Fluorescent Compounds
CF3-Inspired Synthesis of Air-Tolerant 9-Phosphaanthracenes that
Feature Fluorescence and Crystalline Polymorphs
Shigekazu Ito,* Kota Koshino, and Koichi Mikami*[a]
Abstract: 9-Phosphaanthracene (dibenzo[b,e]phosphorin, ac-
ridophosphine) has attracted interest as one of the heavier
acenes. Herein, we demonstrate an efficient synthetic pro-
cess that provides air-tolerant 1,8-bis(trifluoromethyl)-9-
phosphaanthracenes. The sterically encumbered and elec-
tron-withdrawing trifluoromethyl (CF3) groups are quite ad-
vantageous not only to stabilize the intrinsically unstable
heavier unsaturated phosphorus atom but also to facilitate
construction of the phosphinine skeleton based on a puta-
tive increase in aromaticity. The isolated 9-phosphaanthra-
cenes allowed characterization of their fluorescence func-
tionality and planar heteroanthracene frameworks. The crys-
tal structures of 9-phosphaanthracenes are remarkably de-
pendent on the aryl substituents at the 10 position; anthryl-
substituted 9-phosphaanthracene showed unique poly-
morphs that induced different-colored crystals.
achieved.[2b,c] The spectroscopic data of II and III indicated that
the P=C double bond has a structural character similar to the
C=C and N=C bonds,[3] which stimulated the development of
various heavier PAH analogues with P=C units.[4] The photo-
electron (PE) spectrum of III indicated that the phenyl substitu-
ent at the 10 position is perpendicular to the phosphaanthra-
cene plane,[2c] which would be useful to stabilize the intrinsical-
ly unstable heavier anthracene system kinetically rather than
thermodynamically. A further extension of the p system of
phosphaanthracene could be promising to develop, for exam-
ple, novel organic semiconductors.[5–7] However, III is quite air
sensitive, and almost no information about 9-phosphaanthra-
cene with respect to functionality has been available until
now. Thus, the synthesis of isolable crystalline 9-phosphaan-
thracenes is a requisite for an exploration of the functionality
of the heavier congeners of acenes.
Introduction
Replacement of the sp2 carbon atom(s) of polyaromatic hydro-
carbon (PAH) molecules with heavier main-group elements has
been attractive because the heavier unsaturated double bonds
induce intriguing p-orbital (band) properties. After Mꢀrkl syn-
thesized phosphabenzene (phosphorin, phosphinine) I as a
phosphorus analogue of benzene in 1966,[1] Bickelhaupt suc-
ceeded in generating 9-phosphaanthracene II in 1967 (Fig-
ure 1a).[2a] Introduction of a substituent at the 10 position was
effective to improve the stability of 9-phosphaanthracene, and
characterization of III by using UV/Vis spectroscopy was thus
Figure 1b depicts a design for isolable 9-phosphaanthra-
cenes under ambient conditions. We posited that the introduc-
tion of sterically demanding groups at the 1 and 8 positions of
9-phosphaanthracene should be effective to protect the P=C
unsaturated bond sterically. As an approach for the synthesis
of isolable 9-phosphaanthracenes, herein we employed CF3
groups as substituents at the 1 and 8 positions because the
CF3 group has been useful for kinetic stabilization of unstable
molecular structures.[8] In addition to the steric effect, the elec-
tron-withdrawing CF3 group substantially reduces the LUMO
level of the 9-phosphaanthracene unit, which might be advan-
tageous to develop, for example, n-type organic semiconduc-
tors based on strong p-accepting character.[3,4] DFT calcula-
tions[9] for 1,8-bis(trifluoromethyl)-9-phosphaanthracene at the
B3LYP/6-311G(d) level showed LUMO and HOMO energetic
levels of À2.92 and À6.06 eV, respectively, whereas the corre-
sponding frontier orbital levels for 9-phosphaanthracene (II)
were estimated as À2.38 and À5.47 eV at the same level. Fur-
Figure 1. a) Reported phosphorus analogues of aromatic molecules.
b) Design for stable 9-phosphaanthracenes.
[a] Prof. Dr. S. Ito, K. Koshino, Prof. Dr. K. Mikami
Department of Chemical Science and Engineering, School of Materials and
Chemical Technology
Tokyo Institute of Technology
2-12-1-H113 Ookayama, Meguro, Tokyo 152-8552 (Japan)
E-mail: ito.s.ao@m.titech.ac.jp
mikami.k.ab@m.titech.ac.jp
Supporting information and the ORCID identification number(s) for the au-
thor(s) of this article can be found under:
https://doi.org/10.1002/asia.201701669.
Chem. Asian J. 2018, 00, 0 – 0
1
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
thermore, the CF3 group would be relatively advantageous for
molecular assembly in the crystalline state, which might be
useful to promote solid-state functionality.[10] Also, we speculat-
ed that the presence of a sterically demanding aromatic sub-
stituent at the 10 position of 9-phosphaanthracene would be
effective to retard decomposition of the 9-phosphaanthracene
skeleton. Below we demonstrate the synthesis of air-tolerant 9-
phosphaanthracenes and reveal their fluorescence and particu-
lar crystal characteristics. The effects of the CF3 groups are also
discussed through the synthesis of non-trifluoromethylated 9-
phosphaanthracene.
Table 1. The Friedel–Crafts reaction of 4 to afford 5a–c.
Ar
Solvent
Reaction time
Yield [%]
98
CH2Cl2
24 h
(5a)
ClCH2CH2Cl
5 d
76
71
(5b)
(5c)
Results and Discussion
CH2Cl2
48 h
The synthetic procedures for precursors 5 were in part analo-
gous to previous studies (Scheme 1, Table 1).[2] Commercially
available 1-bromo-2-(trifluoromethyl)benzene (1) was treated
with lithium diisopropylamide (LDA) and chlorotrimethylsi-
lane,[11] and silylated product 2 was converted into 2-bromo-1-
iodo-3-(trifluoromethyl)benzene (3).
A halogen–metal ex-
change of 3 followed by treatment with ethyl formate gave di-
arylcarbinol 4, and the subsequent Friedel–Crafts reaction suc-
cessfully afforded triarylmethanes 5.
Scheme 2. The construction step of 9-phosphaanthracenes 6 through elimi-
nation of dimethylamine from possible intermediate 7.
cal chemical shifts of the P=C moiety (dP =204–211 ppm) ac-
companied by substantial coupling with 19F nuclei (ꢀ70 Hz)
were observed. The elimination of dimethylamine from an ami-
nophosphorin intermediate (7) could proceed in this process,
which indicated that the CF3 groups might facilitate the aro-
matization step to afford the phosphinine unit. The effect of
trifluoromethyl on the elimination/aromatization step was sup-
ported by the fact that reaction of 2,2’-(mesitylmethylene)bis-
(bromobenzene) did not afford the desired 10-mesityl-9-phos-
phaanthracene at ambient temperature, and the 31P NMR
signal of non-trifluromethylated derivative 7a’ (Ar=Mes: dP =
42.7 ppm) was observed under the same reaction conditions
(Figure S1 in the Supporting Information). However, heating
7a’ at 608C for 40 h afforded 6a’ in 40% isolated yield. Be-
cause the NICS (nucleus-independent chemical shift) parame-
ters[12] over the C5P rings in 6a and 9-phosphaanthracene were
comparable (À10.9 (6a), À11.2 ppm (9-phosphaanthracene);
NICS(1), B3LYP/6-311+G(2d,p)),[9] the prompt elimination of di-
methylamine from 7 might relate to increased acidity at the
methine proton.
Scheme 1. Synthesis of triarylmethanes 5 as precursors for 9-phosphaanthra-
cenes.
The construction of 9-phosphaanthrace from 5 was unex-
pectedly easy compared with the synthesis of II and III
(Scheme 2). After halogen–metal exchange of 5 with two
equivalents of butyllithium, reaction of the generated dilithium
intermediate with 1,1-dichloro-N,N-dimethylphosphanamine
(Me2NPCl2) afforded desired 9-phosphaanthracenes 6a–c di-
rectly in moderate isolated yields. In the 31P NMR spectra, typi-
&
&
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
2
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
Figure 2 highlights the UV/Vis spectra of 6. The longest
wavelength absorptions of 6a (l=436 nm, e=6710) and 6b
(l=438 nm, e=3130) are comparable to II (l=429 nm)[2a] and
III (l=432 nm, e=7970),[2b] which is compatible to the ener-
Figure 2. UV/Vis spectra of 6 in dichloromethane.
getic difference between the HOMO and LUMO mentioned
above. TD-DFT studies assigned absorptions at around l=350
to 450 nm for 6a and 6b, which could be assigned as a
HOMO-to-LUMO transition (Figure 3, top).[2,9] Similar to anthra-
cene, the vibrational bands of the 0–0 (see above), 0–1 (6a:
l=414 nm, 6b: l=416 nm), and 0–2 (6a: l=395 nm, 6b: l=
397 nm) vibronic peaks could be characterized. The weaker ab-
sorption of 6b compared with 6a might relate to steric en-
cumbrance around the 10 position. In the UV/Vis spectrum of
6c, the peaks of the anthryl group are accompanied by those
of the 9-phosphaanthracene unit (l0–0 =433, l0–1 =411, l0–2
=
391 nm). The HOMO–LUMO transition of 6c could not be ob-
served, which indicates a lack of overlap between the HOMO
and LUMO (Figure 3, bottom). The UV/Vis spectrum of 6c also
confirms the smaller frontier-orbital energetic gap of the phos-
phaanthracene unit compared with the anthryl group. Non-tri-
fluoromethylated phosphaanthracene 6a’ showed a lower re-
duction potential compared with trifluromethylated derivatives
6 (Figures S2, S3).
The CF3 groups substantially stabilized the 9-phosphaanthra-
cene unit, and crystalline 6 can be handled in air. Furthermore,
as indicated by monitoring of the decay of the UV/Vis peak
under exposure to air, the approximate half-life of 6a (110 min)
was considerably longer than that of 6a’ (7.2 min; in dichloro-
methane, Figure S4).
Figure 3. Top: Frontier orbitals of 6a,b accompanied by transitions relating
to photoabsorption and -emission; Mes=2,4,6-Me3C6H2 (mesityl),
Trip=2,4,6-iPr3C6H2. Bottom: Frontier orbitals of 6c accompanied by transi-
tions relating to photoabsorption and -emission. Transitions mainly from
HOMOÀ1 to LUMO (442 nm, 2.81 eV, f=0.1505) and from HOMO to
LUMO+1 (394 nm, 3.15 eV, f=0.0706) are omitted; Ant=9-anthryl. The
structures were optimized at the B3LYP/6-31G(d) level. The transition param-
eters were determined by using TD-DFT calculations at the B3LYP/6-
31+G(d)//B3LYP/6-31G(d) level.[9]
Figure 4 shows the fluorescence spectra of 6 (lex =420 nm)
in dichloromethane, and Table 2 summarizes the emission pa-
rameters. Compounds 6a and 6b showed almost the same
fluorescence characters in solution, which indicated that the in-
fluence of bulky Mes and Trip substituents on the excited CF3-
containing 9-phosphaanthracene unit would be identical. Con-
versely, 6c showed quite weak emission around l=580 nm
due to the forbidden relaxation from LUMO to HOMO.[9] The
fluorescence property of an amorphous solid of 6a was com-
parable with that in solution (Figure 5; lem =503 nm, F=
12%), whereas 6b showed a remarkable reduction in quantum
yield together with an additional fluorescence peak (l=496,
538 nm, F=2%). Although a detailed analysis of the fluores-
cence data of 6a and 6b is ongoing, the combination of CF3
groups and the Mes substituent are effective to minimize con-
centration quenching. An amorphous solid of 6c showed
almost no fluorescence, which might be related to the crystal-
line polymorphs mentioned below.
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
3
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Figure 6. Molecular structures of 6a (top view: 50% probability level, side
view: 20% probability level). Hydrogen atoms are omitted for clarity. Select-
ed bond lengths [ꢂ] and angles [8]: P1ÀC1 1.745, C1ÀC6 1.442(2), C6ÀC7
1.416; C1-P1-C1* 102.2, P1-C1-C6 124.4, C1-C6-C7 122.5, C6-C7-C6* 123.6.
Figure 4. Normalized fluorescence spectra of 6 in dichloromethane.
Table 2. Fluorescence parameters of 6.
structure of 6a might relate to fluorescence properties in the
solid state, that is, the mesityl group might minimize substan-
tial interactions and induce a decrease in the quantum yield.
The sterically encumbered Trip substituent in 6b prevented
substantial p–p interactions in the crystalline state, and the
crystal structure showed almost no effective p–p overlap (Fig-
ure S6). However, the fluorescence efficiency of 6b was re-
markably reduced in the solid state compared with in solution,
putatively due to the enhanced CH–p interaction.[15]
Ar
lem [nm][a]
F [%][b]
6a
6b
6c
Mes
Trip
9-anthryl
508
511
583
13
13
0.1
[a] In dichloromethane; lex =420 nm. [b] Quantum yield, as determined
by using the integrating sphere method.
Recrystallization of 6c from a mixture of THF and methanol
(1:1) provided single crystals suitable for X-ray crystallographic
analysis, but both a large amount of red crystals and a few
yellow prisms were obtained (see the Table of Contents figure).
The X-ray crystallography results for the red and yellow crystals
revealed notably different crystal structures. As displayed in
Figure 7a, the red crystal of 6c showed weak dimeric p–p in-
Figure 5. Normalized fluorescence spectra of 6 in dichloromethane.
Figure 6 displays an ORTEP drawing of the molecular struc-
ture of 6a. The heavier anthracene skeleton is slightly distort-
ed, with a dihedral angle of 6.108 between the two benzene
rings, and the metric parameters around the phosphinine ring
are comparable to those of the isolated phosphinine deriva-
tives.[13] The mesityl ring at the 10 position is almost perpen-
dicular to the 9-phosphaanthracene plane, which corresponds
to previous findings based on the PE spectra of 10-aryl-9-phos-
phaanthracenes.[2c] Figure S5 shows the packing structure of
6a in the crystal state. The 9-phosphaanthracene skeletons in-
dicated weak p–p interactions with offset-like overlaps along
the c axis (Figure S5a), and the distance between the 9-phos-
phaanthracene planes is 3.635 ꢂ (Figure S5b).[14] The packing
Figure 7. Selected dimers of 6c in a) the reddish orthorhombic and b) the
yellowish monoclinic space. Ellipsoids are drawn at the 50% level.
teraction between the 9-phosphaanthracene planes with a dis-
tance of 4.016 ꢂ and an offset dimeric p–p interaction be-
tween the 10-anthryl groups in the orthorhombic unit. In con-
trast, the yellow crystal of 6c adopted a p–p contact of
3.704 ꢂ between the anthryl substituents in the monoclinic
space (Figure 7b). The anthryl group in 6c showed almost per-
pendicular conformation with the 9-phosphaanthracene plane,
but the reddish orthorhombic space induced a smaller torsion
angle of 80.08 compared with that in the yellowish monoclinic
unit (86.78). The slightly smaller torsion angle in the reddish
&
&
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
4
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
crystals seems to be compatible with the redshift of the single
crystals. Indeed a plot of HOMO of 6c in the reddish form indi-
cates weak p conjugation between the phosphaanthryl and
anthryl planes (Figure 8). However, DFT calculations (B3LYP/6-
Conclusions
Air-tolerant 9-phosphaanthracenes were successfully synthe-
sized by using the effect of CF3 groups to promote the aroma-
tization process and stabilize the heavier acene unit. The emis-
sion properties of 9-phosphaanthracene were characterized
and the almost planar 9-phosphaanthracene skeleton was un-
ambiguously determined by using X-ray crystallography. The
crystal structure was remarkably dependent on the substituent
at the 10 position, and the 9-anthryl group promoted poly-
morphism to afford red and yellow single crystals. The present
work provides candidate materials for novel fluorescence ma-
terials that incorporate phosphorus and fluorine and might be
attractive for biological studies. The solid-state character of the
induced 9-phosphaanthracene polymorphs could be applicable
to the development of, for example, sensoring devices.[17]
Figure 8. Plots of the HOMO of 6c in a) the orthorhombic and b) the mono-
clinic space (isovalue=0.02), calculated at the B3LYP/6-31+G(d) level.
31+G(d))[9] showed that the smaller torsion angle induced
almost no reduction in the HOMO–LUMO energetic gap of the
single molecule (red: DEHOMO–LUMO =2.9347 eV, yellow: DEHOMO–
LUMO =2.9349 eV). A reflection spectrum of the reddish sample
of 6c (6c-R) indicated that the visible absorption was clearly
redshifted (Figure 9). Therefore, the redshift might be due to
the effect of multiple molecules.
Experimental Section
1H, 13C, 31P, and 19F NMR spectra were measured by using a Bruker
1
Avance 300 (300 MHz) spectrometer. Chemical shifts of the H NMR
signals are expressed in parts per million downfield from CHCl3 as
an internal standard (d=7.26 ppm) in CDCl3. Chemical shifts of the
13C NMR signals are expressed in parts per million downfield from
CDCl3 as an internal standard (d=77.16 ppm) in CDCl3. Chemical
shifts of the 31P NMR signals are expressed in parts per million
downfield from 85% H3PO4 as an external standard (d=0 ppm) in
CDCl3. Chemical shifts of the 19F NMR signals are expressed in parts
per million downfield from benzotrifluoride as an internal standard
(d=À63.24 ppm) in CDCl3. Mass spectra were measured by using
a JEOL JMS-T100LC spectrometer. X-ray crystal analyses were mea-
sured by using a Rigaku RAXIS-RAPID diffractometer. Electrochemi-
cal analyses were measured by using a BAS Electrochemical Ana-
lyzer Model 620Ds. UV/Vis spectra (absorption, reflection) were
measured by using a Hitachi U4100 spectrometer. Photolumines-
cence spectra were measured by using a Shimadzu RF-6000 spec-
trometer equipped with an integrating sphere.
Preparation of 2-bromo-3-(trifluoromethyl)-1-(trimethylsilyl)-
benzene (2)[11]
A solution of LDA was prepared by mixing nBuLi (82.7 mmol,
2.65m in hexane) and diisopropylamine (12.5 mL, 82.7 mmol) in
THF (40 mL) at 08C, then added slowly to a solution of 2-bromo-
benzotrifluoride (10.2 mL, 75.2 mmol) and trimethylsilyl chloride
(10.4 mL, 82.7 mmol) in THF (100 mL) at À608C under an argon at-
mosphere. After stirring at the same temperature for 4 h, the reac-
tion mixture was quenched with 1m aqueous HCl and warmed to
RT. The layers were separated, then the aqueous layer was extract-
ed with AcOEt and the combined organic layers were washed with
brine and dried over MgSO4. The solvent was removed in vacuo,
and the residue was distilled under reduced pressure (758C/6 hPa)
to afford 2 as a colorless liquid (16.3 g, 73% yield). 1H NMR
(300 MHz, CDCl3): d=7.69 (dd, 3J(H,H)=7.8, 4J(H,H)=1.5 Hz, 1H),
7.62 (dd, J(H,H)=7.5, J(H,H)=1.2 Hz, 1H), 7.40 (m, 1H), 0.46 ppm
(s, 9H); 13C{1H} NMR (75 MHz, CDCl3): d=145.4, 139.4, 130.4 (q,
2J(F,C)=30.3 Hz), 128.8 (q, 3J(F,C)=5.7 Hz), 127.8, 126.6, 123.5 (q,
1J(F,C)=273.6 Hz), À0.1 ppm; 19F NMR (282 MHz, CDCl3): d=
À62.1 ppm (s).
Figure 9. Reflection spectra of reddish crystals of 6c (6c-R) and yellowish
crystals of 6c (6c-Y).
The smaller density of 6c in the orthorhombic unit would in-
dicate inferior thermodynamic stability compared with the
monoclinic system, and thus the large amount of red crystals
might be due to crystallization under kinetic control.[16] Howev-
er, most of the amorphous solids after evaporation of the sol-
vent were yellowish. One of the reasons for the crystalline
polymorphs of 6c could be related to conformational flexibility
around the single bond between the phosphaanthryl and the
anthryl units. Also, the putative conformational flexibility of 6c
might reduce the efficiency of photoluminescence.
3
4
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
5
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Preparation of 2-bromo-1-iodo-3-(trifluoromethyl)benzene
(3)
Preparation of 3,3’-[(2,4,6-triisopropylphenyl)methylene]-
bis[2-bromo-1-(trifluoromethyl)benzene] (5b)
Iodine monochloride (4.56 mL, 87.0 mmol) was added slowly to a
solution of 2 (21.6 g, 72.5 mmol) in CH2Cl2 (200 mL) at À788C
under an argon atmosphere. The reaction mixture was allowed to
warm to RT and stirred for 20 h, then quenched with saturated
aqueous NaHSO3. The layers were separated and the aqueous layer
was extracted with CH2Cl2. The combined organic layers were
washed with brine and dried over MgSO4, then the solvent was re-
moved in vacuo and the residue was distilled under reduced pres-
sure (858C/7 hPa) to afford 3 as a pale yellow liquid (20.9 g, 82%
yield). 1H NMR (300 MHz, CDCl3): d=8.08 (dd, 3J(H,H)=8.1,
4J(H,H)=0.9 Hz, 1H), 7.68 (dd, 3J(H,H)=7.8, 4J(H,H)=1.2 Hz, 1H),
7.12 ppm (td, 3J(H,H)=7.8, 4J(H,H)=0.6 Hz, 1H); 13C{1H} NMR
(75 MHz, CDCl3): d=143.8, 131.9 (q, 2J(F,C)=30.9 Hz), 128.4, 127.6
(q, 3J(F,C)=5.7 Hz), 127.5, 122.5 (q, 1J(F,C)=274.0 Hz), 106.2 ppm;
19F NMR (282 MHz, CDCl3): d=À63.3 ppm (s); APCI-MS: m/z calcd
for C7H279Br1F3I [MÀH]À: 348.8337; found: 348.8328.
Trifluoromethanesulfonic acid (5 mL, 0.06 mmol) was added to a so-
lution of 4 (359 mg, 0.75 mmol) and 1,3,5-triisopropylbenzene
(0.90 mL, 3.75 mmol) in 1,2-dichloroethane (10 mL) under an argon
atmosphere, and the reaction mixture was heated at reflux for 5 d.
After cooling to RT, the reaction mixture was quenched with water,
the layers were separated, and the aqueous layer was extracted
with CH2Cl2. The combined organic layers were washed with brine
and dried over MgSO4, then the solvent was removed in vacuo
and the residue was purified by using silica gel column chromatog-
raphy (eluent: hexane) to afford 5b as a colorless solid (378 mg,
1
76% yield). H NMR (300 MHz, CDCl3): d=7.64 (brs, 2H), 7.39 (brs,
3
2H), 7.00 (brs, 4H), 6.55 (s, 1H), 3.11 (brs, 1H), 2.89 (sept., J(H,H)=
3
6.9 Hz, 1H), 2.78 (brs, 1H), 1.40 (brs, 3H), 1.27 (d, J(H,H)=6.9 Hz,
6H), 1.15 (brs, 3H), 0.69 (brs, 3H), 0.33 ppm (brs, 3H); 19F NMR
(282 MHz, CDCl3): d=À62.1 ppm (s); APCI-MS: m/z calcd for
C30H2979Br2F6 [MÀH]À: 661.0540; found: 661.0547. A well-resolved
13C NMR spectrum was not obtained due to broadening of the sig-
nals.
Preparation of bis[2-bromo-3-(trifluoromethyl)phenyl]me-
thanol (4)
Preparation of 9-{bis[2-bromo-3-(trifluoromethyl)phenyl]me-
thyl}anthracene (5c)
iPrMgBr (27.0 mmol, 1.0m in THF) was added slowly to a solution
of 3 (9.47 g, 27.0 mmol) in THF (70 mL) at À788C under an argon
atmosphere. The reaction mixture was warmed to À408C and
stirred for 4 h, then ethyl formate (1.09 mL, 13.5 mmol) was added
dropwise to this mixture at the same temperature. The reaction
mixture was warmed to RT and stirred for 24 h. The reaction mix-
ture was quenched with saturated aqueous NH4Cl. The layers were
separated and the aqueous layer was extracted with AcOEt. The
combined organic layers were washed with brine and dried over
Na2SO4, then the solvent was removed in vacuo and the residue
was purified by using silica gel column chromatography (eluent:
hexane/EtOAc 6:1) to afford 4 as a colorless solid (5.30 g, 82%
yield). 1H NMR (300 MHz, CDCl3): d=7.69 (dd, 3J(H,H)=7.5,
4J(H,H)=1.8 Hz, 2H), 7.51–7.38 (m, 4H), 6.60 (s, 1H), 3.12 ppm (s,
1H); 13C{1H} NMR (75 MHz, CDCl3): d=143.3, 131.9, 131.3 (q,
Trifluoromethanesulfonic acid (21 mL, 0.24 mmol) was added to a
solution of
4 (1.43 g, 3.00 mmol) and anthracene (1.07 g,
6.00 mmol) in CH2Cl2 (30 mL) under an argon atmosphere, and the
reaction mixture was heated at reflux for 48 h. After cooling to RT,
the reaction mixture was quenched with water, the layers were
separated, and the aqueous layer was extracted with CH2Cl2. The
combined organic layers were washed with brine and dried over
MgSO4, then the solvent was removed in vacuo and the residue
was purified by using silica gel column chromatography (eluent:
hexane/EtOAc 30:1) and then recrystallized from hexane and CHCl3
to afford 5c as a pale yellow solid (1.37 g, 71% yield). 1H NMR
3
(300 MHz, CDCl3): d=8.53 (s, 1H), 8.04 (d, J(H,H)=9.0 Hz, 2H), 7.93
(brs, 2H), 7.70–7.62 (m, 2H), 7.49–7.23 ppm (m, 9H); 13C{1H} NMR
(75 MHz, CDCl3): d=144.8, 134.8, 132.1, 132.0, 131.8 (q, 2J(F,C)=
30.7 Hz), 131.3, 129.9, 129.3, 127.5, 127.0 (m), 126.6, 124.9, 124.2,
123.4, 123.2 (q, 1J(F,C)=273.6 Hz), 54.3 ppm; 19F NMR (282 MHz,
CDCl3): d=À62.1 ppm (s); APCI-MS: m/z calcd for C29H1579Br2F6
[MÀH]À: 634.9445; found: 634.9467.
3
1
2J(F,C)=30.7 Hz), 127.9 (q, J(F,C)=5.7 Hz), 127.8, 123.1 (q, J(F,C)=
273.7 Hz), 121.8 (m), 74.3 ppm; 19F NMR (282 MHz, CDCl3): d=
À62.1 ppm (s); APCI-MS: m/z calcd for C15H779Br2F6O [MÀH]À:
474.8768; found: 474.8769.
Preparation of 3,3’-(mesitylmethylene)bis[2-bromo-1-(tri-
fluoromethyl)benzene] (5a)
Preparation of 10-mesityl-1,8-bis(trifluoromethyl)-9-phos-
pha-anthracene (6a)
Trifluoromethanesulfonic acid (32 mL, 0.36 mmol) was added to a
nBuLi (0.200 mmol) was added slowly to a solution of 5a (58.0 mg,
0.100 mmol) in THF (1.5 mL) at À788C under an argon atmosphere.
After stirring at the same temperature for 1 h, dichloro(dimethyla-
mino)phosphine (17 mL, 0.15 mmol) was added dropwise to the re-
action mixture, which was stirred at the same temperature for 2 h,
then the reaction mixture was allowed to warm to RT and stirred
for 10 min. The solvent was removed in vacuo and the residue was
purified by using silica gel column chromatography (eluent:
hexane/EtOAc 30:1) to afford 6a as a yellow solid (31.0 mg, 69%
solution of
4 (2.15 g, 4.50 mmol) and mesitylene (3.14 mL,
22.5 mmol) in CH2Cl2 (30 mL) under an argon atmosphere, and the
reaction mixture was heated at reflux for 24 h. After cooling to RT,
the reaction mixture was quenched with water, the layers were
separated, and the aqueous layer was extracted with CH2Cl2. The
combined organic layers were washed with brine and dried over
MgSO4, then the solvent was removed in vacuo and the residue
was purified by using silica gel column chromatography (eluent:
hexane/EtOAc 30:1) to afford 5a as a colorless solid (2.56 g, 98%
yield). 1H NMR (300 MHz, CDCl3): d=7.66 (d, 3J(H,H)=7.5 Hz, 2H),
7.32 (t, 3J(H,H)=7.7 Hz, 2H), 7.06 (brs, 2H), 6.86 (s, 2H), 6.31 (s,
1H), 2.29 (s, 3H), 1.92 ppm (brs, 6H); 13C{1H} NMR (75 MHz, CDCl3):
d=144.3, 137.4, 137.1, 134.8, 133.9, 131.5 (q, 2J(F,C)=30.6 Hz),
130.9, 127.3, 126.7 (m), 123.6, 123.2 (q, 1J(F,C)=273.7 Hz), 54.6,
22.3, 20.9 ppm; 19F NMR (282 MHz, CDCl3): d=À62.1 ppm (s); APCI-
MS: m/z calcd for C24H1779Br2F6 [MÀH]À: 576.9601; found: 576.9618.
1
yield). M.p. 1658C (decomp.); H NMR (300 MHz, CDCl3): d=7.96 (d,
3J(H,H)=6.9 Hz, 2H), 7.86 (dd, 3J(H,H)=8.7, 4J(H,H)=1.5 Hz, 2H),
3
7.52 (t, J(H,H)=8.0 Hz, 2H), 7.12 (s, 2H), 2.48 (s, 3H), 1.63 ppm (s,
6H); 13C{1H} NMR (75 MHz, CDCl3): d=150.8 (d, 1J(P,C)=57.4 Hz),
3
5
142.8 (d, J(P,C)=25.7 Hz), 138.3, 137.1 (d, J(P,C)=3.0 Hz), 135.9 (d,
4J(P,C)=3.8 Hz), 134.0 (d, 3J(P,C)=2.3 Hz), 132.9 (qd, 2J(F,C)=29.7,
2J(P,C)=21.4 Hz), 132.6 (d, J(P,C)=14.1 Hz), 129.0, 126.7 (d, J(P,C)=
6.8 Hz), 124.9 (q, J(F,C)=275.5 Hz), 124.3 (dq, J(P,C)=18.5, J(F,C)=
2
4
1
3
3
&
&
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
6
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
6.8 Hz), 21.4, 20.1 ppm; 31P{1H} NMR (121 MHz, CDCl3): d=
205.6 ppm (sept., 4J(F,P)=70.5 Hz); 19F NMR (282 MHz, CDCl3): d=
À57.5 ppm (d, 4J(P,F)=68.9 Hz); APCI-MS: m/z calcd for C24H16F6P
[MÀH]À: 449.0894; found: 449.0878.
stirred at the same temperature for 2 h. The reaction mixture was
allowed to warm to 608C gradually and stirred for 60 h, then
cooled to RT and the solvent was removed in vacuo. The residue
was extracted with dry hexane (2ꢃ3 mL) and the suspension was
filtered off. After the solution was concentrated to ꢀ0.5 mL, a
yellow solid formed. The precipitate was separated and washed
with a small amount of dry hexane to afford 6a’ as an orange solid
(37.4 mg, 40% yield). M.p. 1158C (decomp.); 1H NMR (300 MHz,
CDCl3): d=8.60–8.49 (m, 2H), 7.68–7.61 (m, 2H), 7.49–7.41 (m, 4H),
2.47 (s, 3H), 1.67 ppm (s, 6H); 13C{1H} NMR (75 MHz, CDCl3): d=
156.8 (d, 1J(P,C)=38.0 Hz), 140.9 (d, 3J(P,C)=27.3 Hz), 137.5, 137.3
(d, 5J(P,C)=3.5 Hz), 136.1 (d, 4J(P,C)=3.7 Hz), 134.0 (d, 2J(P,C)=
Preparation of 1,8-bis(trifluoromethyl)-10-(2,4,6-triisopropyl-
phenyl)-9-phosphaanthracene (6b)
nBuLi (0.200 mmol) was added slowly to a solution of 5b (66.4 mg,
0.100 mmol) in THF (1.5 mL) at À788C under an argon atmosphere.
After stirring at the same temperature for 1 h, dichloro(dimethyla-
mino)phosphine (17 mL, 0.15 mmol) was added dropwise and the
mixture was stirred at the same temperature for 2 h. The reaction
mixture was allowed to warm to RT and stirred for 10 min, then
the solvent was removed in vacuo and the residue was purified by
using silica gel column chromatography (eluent: hexane/EtOAc
30:1) to afford 6b as a yellow solid (28.9 mg, 54% yield). M.p. 113–
114 8C; 1H NMR (300 MHz, CDCl3): d=7.99–7.89 (m, 4H), 7.51 (t,
2
3
35.7 Hz), 132.7 (d, J(P,C)=15.5 Hz), 129.4 (d, J(P,C)=4.0 Hz), 128.7,
4
3
128.0 (d, J(P,C)=7.5 Hz), 123.4 (d, J(P,C)=26.2 Hz), 21.4, 20.0 ppm;
31P{1H} NMR (121 MHz, CDCl3): d=198.3 (s); APCI-MS: m/z calcd for
C24H16F6P [M]À: 314.1224; found: 314.1213.
3
3J(H,H)=8.0 Hz, 2H), 7.24 (s, 2H), 3.08 (sept., J(H,H)=6.9 Hz, 1H),
X-ray crystallographic data for 6a
1.86 (sept., 3J(H,H)=6.9 Hz, 2H), 1.42 (d, 3J(H,H)=7.2 Hz, 6H),
0.84 ppm (d, 3J(H,H)=6.9 Hz, 12H); 13C{1H} NMR (75 MHz, CDCl3):
C24H17F6P; yellow prisms (hexane, 298 K); MW =450.34; crystal di-
mensions 0.430ꢃ0.350ꢃ0.230 mm3; monoclinic; space group C2/c
(#15); a=15.3153(8), b=13.5966(6), c=11.0363(5) ꢂ; b=
118.983(2)8; V=2010.34(17) ꢂ3; Z=4; l=0.71075 ꢂ; T=143 K;
1
5
d=149.6 (d, J(P,C)=57.5 Hz), 148.9, 146.4 (d, J(P,C)=2.9 Hz), 142.3
(d, 3J(P,C)=25.6 Hz), 134.3, 132.6 (d, 2J(P,C)=14.2 Hz), 132.5 (d,
4J(P,C)=3.3 Hz), 131.7 (qd, J(F,C)=29.8, J(P,C)=21.6 Hz), 124.9 (d,
2
2
1calcd =1.488 gcmÀ3; mMo =0.200 mmÀ1; F000 =920; 9732 total re-
4J(P,C)=6.7 Hz), 124.0 (q, J(F,C)=275.2 Hz), 123.4 (dq, J(P,C)=18.4,
3J(F,C)=6.7 Hz), 121.0, 33.5, 30.2, 23.5, 23.3 ppm; 31P{1H} NMR
(121 MHz, CDCl3): d=203.8 ppm (sept., 4J(F,P)=70.5 Hz); 19F NMR
1
3
Ka
flections (2qmax =54.968); index ranges=À19ꢁhꢁ19, À17ꢁkꢁ
17, À14ꢁlꢁ13; 2308 unique reflections (Rint =0.0321), R1 =0.0373
(I>2s(I)), 0.0475 (all data), wR2 =0.1185 (I>2s(I)), 0.1371 (all data);
S=1.037 (184 parameters).
4
(282 MHz, CDCl3): d=À57.5 ppm (d, J(P,F)=69.7 Hz); APCI-MS: m/
z calcd for C30H28F6P [MÀH]À: 533.1833; found: 533.1810.
X-ray crystallographic data for 6b
C30H29F6P; orange prisms (CH2Cl2/MeOH, 298 K); MW =534.50; crys-
tal dimensions 0.500ꢃ0.440ꢃ0.330 mm3; monoclinic; space group
P21/n (#14); a=17.1846(7), b=9.2562(4), c=17.6956(8) ꢂ; b=
93.8120(10)8; V=2808.5(2) ꢂ3; Z=4; l=0.71075 ꢂ; T=123 K;
Preparation of 10-(anthracen-9-yl)-1,8-bis(trifluoromethyl)-9-
phosphaanthracene (6c)
nBuLi (0.200 mmol) was added slowly to a solution of 5c (63.8 mg,
0.100 mmol) in THF (4 mL) at À788C under an argon atmosphere.
After stirring at the same temperature for 1 h, dichloro(dimethyla-
mino)phosphine (17 mL, 0.15 mmol) was added dropwise and the
mixture was stirred at the same temperature for 2 h. The reaction
mixture was allowed to warm to RT and stirred for 10 min, then
the solvent was removed in vacuo and the residue was purified by
using silica gel column chromatography (eluent: hexane/EtOAc
30:1) twice to afford 6c as a yellow solid (17.4 mg, 30% yield). M.p.
169–1718C (decomp.); 1H NMR (300 MHz, CDCl3): d=8.75 (s, 1H),
8.19 (d, 3J(H,H)=8.4 Hz, 2H), 7.92 (d, 3J(H,H)=6.9 Hz, 2H), 7.48
(ddd, 3J(H,H)=7.5, 3J(H,H)=6.6, 4J(H,H)=0.9 Hz, 2H), 7.42 (dd,
1calcd =1.264 gcmÀ3; mMo =0.150 mmÀ1; F000 =1112; 44040 total re-
Ka
flections (2qmax =54.968); index ranges=À22ꢁhꢁ22, À11 ꢁkꢁ12,
À22ꢁlꢁ22; 6420 unique reflections (Rint =0.0421), R1 =0.0439 (I>
2s(I)), 0.0521 (all data), wR2 =0.1415 (I>2s(I)), 0.1577 (all data); S=
1.183 (450 parameters).
X-ray crystallographic data for red 6c (6c-R)
C29H15F6P; (THF/MeOH, 298 K); MW =508.38; crystal dimensions
0.250ꢃ0.210ꢃ0.160 mm3; orthorhombic; space group Pbca (#61);
a=12.7636(6), b=24.6203(11), c=14.3172(8) ꢂ; V=4499.1(4) ꢂ3;
4
3
3J(H,H)=9.0, J(H,H)=1.5 Hz, 2H), 7.27 (t, J(H,H)=8.0 Hz, 2H), 7.19
(ddd, 3J(H,H)=8.7, 3J(H,H)=6.6, 4J(H,H)=1.2 Hz, 2H), 6.91 ppm (d,
3J(H,H)=8.7 Hz, 2H); 13C{1H} NMR (75 MHz, CDCl3): d=150.8 (d,
Z=8; l=0.71075 ꢂ; T=123 K; 1calcd =1.501 gcmÀ3
;
mMo =
Ka
0.189 mmÀ1; F000 =2064; 41196 total reflections (2qmax =54.968);
index ranges=À16ꢁhꢁ16, À31ꢁkꢁ31, À18ꢁlꢁ18; 5135
unique reflections (Rint =0.0421), R1 =0.0387 (I>2s(I)), 0.0573 (all
data), wR2 =0.1087 (I>2s(I)), 0.1407 (all data); S=0.933 (385 pa-
rameters).
1J(P,C)=58.2 Hz), 140.3 (d, J(P,C)=25.5 Hz), 135.1, 134.0 (d, J(P,C)=
13.7 Hz), 133.5 (d, J(P,C)=3.2 Hz), 132.8 (qd, J(F,C)=29.5, J(P,C)=
3
2
4
2
2
5
21.7 Hz), 131.7, 131.5 (d, J(P,C)=2.0 Hz), 128.9, 128.3, 126.9, 126.8
(d, 4J(P,C)=7.6 Hz), 126.3, 125.8, 124.9 (q, 1J(F,C)=275.0 Hz),
124.3 ppm (dq, 3J(P,C)=18.3, 3J(F,C)=6.3 Hz); 31P{1H} NMR
(121 MHz, CDCl3): d=210.5 ppm (sept., 4J(F,P)=70.5 Hz); 19F NMR
4
X-ray crystallographic data of yellow 6c (6c-Y)[18]
(282 MHz, CDCl3): d=À57.4 ppm (d, J(P,F)=72.9 Hz); APCI-MS: m/
z calcd for C29H14F6P [MÀH]À: 507.0737; found: 507.0750.
Preparation of 10-mesityl-9-phosphaanthracene (6a’)
C29H15F6P; MW =508.38; crystal dimensions 0.250ꢃ0.180ꢃ
0.150 mm3; monoclinic; space group P21/n (#14); a=9.482(10), b=
9.5543(10), c=24.657(3) ꢂ; b=92.954(4)8; V=2231.3(4) ꢂ3; Z=4;
nBuLi (0.600 mmol) was added slowly to a solution of 2,2’-(mesityl-
methylene)bis(bromobenzene) (133 mg, 0.300 mmol) in THF
(4.5 mL) at À788C under an argon atmosphere. After stirring at the
same temperature for 1 h, dichloro(dimethylamino)phosphine
(52 mL, 0.45 mmol) was added dropwise and the mixture was
l=0.71075 ꢂ; T=123 K; 1calcd =1.513 gcmÀ3; mMo =0.190 mmÀ1
;
Ka
F000 =1032; 21059 total reflections (2qmax =54.968); index ranges=
À12ꢁhꢁ12, À11 ꢁkꢁ12, À31ꢁlꢁ31; 5104 unique reflections
(Rint =0.1120); R1 =0.0616 (I>2s(I)), 0.1275 (all data), wR2 =0.1569
(I>2s(I)), 0.1839 (all data); S=0.875 (385 parameters).
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
7
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Toward the 21st Century (Eds.: J. S. Thrasher, S. H. Strauss), ACS, Wash-
ington, DC, 1994, Chap. 19.
Acknowledgements
[9] Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E.
Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Men-
nucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian,
A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara,
K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro,
M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, T. Keith,
R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S.
Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Strat-
mann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L.
Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dan-
nenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz,
J. Cioslowski, D. J. Fox, Gaussian, Inc., Wallingford CT, 2009.
This work was supported in part by Grants-in-Aid for Scientific
Research (nos. JP25288033 and JP15H00923 (Stimuli-Respon-
sive Chemical Species for the Creation of Functional Molecules,
no. 2408)) from the Ministry of Education, Culture, Sports, Sci-
ence, and Technology, Japan, the Collaborative Research Pro-
gram of Institute for Chemical Research, Kyoto University
(grant no. 2015-23), and Nissan Chemical Industries, Ltd. The
authors thank Prof. Toshiro Takao of Tokyo Institute of Technol-
ogy for support with X-ray crystallography. Prof. Ikuyoshi
Tomita and Dr. Hiroki Nishiyama of Tokyo Institute of Technolo-
gy supported the measurement of fluorescence spectra.
[10] a) J. Schwaben, N. Mꢄnster, M. Klues, T. Breuer, P. Hofmann, K. Harms, G.
Witte, U. Koert, Chem. Eur. J. 2015, 21, 13758; b) J. Schwaben, N. Mꢄn-
ster, T. Breuer, M. Klues, K. Harms, G. Witte, U. Koert, Eur. J. Org. Chem.
2013, 1639; c) S. Yamada, K. Kinoshita, S. Iwata, T. Yamazaki, T. Kubota,
T. Yajima, K. Yamamoto, S. Tahara, Org. Biomol. Chem. 2017, 15, 2522;
d) I. V. Kuvychko, K. P. Castro, S. H. M. Deng, X.-B. Wang, S. H. Strauss,
O. V. Boltalina, Angew. Chem. Int. Ed. 2013, 52, 4871; Angew. Chem.
2013, 125, 4971.
Conflict of interest
The authors declare no conflict of interest.
Keywords: acenes
·
fluorescence
·
heterocycles
·
´
[11] S. Lulinski, J. Serwatowski, J. Org. Chem. 2003, 68, 5384.
[12] P. V. R. Schleyer, C. Maerker, A. Dransfeld, H. Jiao, N. J. R. V. E. Hommes, J.
Am. Chem. Soc. 1996, 118, 6317.
phosphaalkenes · polymorphism
[13] C. Mꢄller, M. Lutz, A. L. Spek, D. Vogt, J. Chem. Crystallogr. 2006, 36, 869.
[14] Single crystals of 6a did not prove suitable for use in semiconductor
devices.
[15] a) M. Nishio, M. Hirota, Y. Umezawa, The CH/p Interaction. Evidence,
Nature and Consequences, Wiley-VCH, New York, 1998; b) M. Nishio,
Phys. Chem. Chem. Phys. 2011, 13, 13873; c) L. M. Salonen, M. Ellermann,
F. Diederich, Angew. Chem. Int. Ed. 2011, 50, 4808; Angew. Chem. 2011,
123, 4908.
[16] The total energy of 6c in the orthorhombic space indicated lower sta-
bility (11.8 kcalmolÀ1) than in the monoclinic space (B3LYP/6-31+G(d)).
[17] P. Trouillas, J. C. Sancho-Garcꢆa, V. De Freitas, J. Gierschner, M. Otyepka,
O. Dangles, Chem. Rev. 2016, 116, 4937.
[18] CCDC 1580575 (6a), 1580576 (6b), 1580577 (6c-R), and 1580578 (6c-Y)
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre.
[1] a) G. Mꢀrkl, Angew. Chem. Int. Ed. Engl. 1966, 5, 846; Angew. Chem.
1966, 78, 907; b) G. Mꢀrkl, F. Lieb, A. Merz, Angew. Chem. Int. Ed. Engl.
1967, 6, 87; Angew. Chem. 1967, 79, 59; c) G. Mꢀrkl, A. Kallmꢄnzer, H.
Noth, K. Pohlmann, Tetrahedron Lett. 1992, 33, 1597.
[2] a) P. de Koe, F. Bickelhaupt, Angew. Chem. Int. Ed. Engl. 1967, 6, 567;
Angew. Chem. 1967, 79, 533; b) P. de Koe, F. Bickelhaupt, Angew. Chem.
Int. Ed. Engl. 1968, 7, 889; Angew. Chem. 1968, 80, 912; c) G. Jongsma,
H. Vermeer, F. Bickelhaupt, W. Schꢀfer, A. Schweig, Tetrahedron 1975, 31,
2931.
[3] a) K. B. Dillon, F. Mathey, J. F. Nixon, Phosphorus: The Carbon Copy, Wiley,
Chichester, 1998; b) F. Mathey, Angew. Chem. Int. Ed. 2003, 42, 1578;
Angew. Chem. 2003, 115, 1616; c) M. Yoshifuji, J. Chem. Soc. Dalton
Trans. 1998, 3343.
[4] a) T. Baumgartner, R. Rꢅau, Chem. Rev. 2006, 106, 4681; b) M. A. Shame-
em, A. Orthaber, Chem. Eur. J. 2016, 22, 10718.
[5] G. Long, X. Yang, W. Chen, M. Zhang, Y. Zhao, Y. Chen, Q. Zhang, Phys.
Chem. Chem. Phys. 2016, 18, 3173.
[6] For 9-silaanthracene, see: a) N. Takeda, A. Shinohara, N. Tokitoh, Organo-
metallics 2002, 21, 256; b) N. Tokitoh, Acc. Chem. Res. 2004, 37, 86; c) N.
Tokitoh, Bull. Chem. Soc. Jpn. 2004, 77, 429.
[7] For a design for singlet fission, see: K. Bhattacharyya, S. M. Pratik, A.
Datta, J. Phys. Chem. C 2015, 119, 25696.
Manuscript received: November 30, 2017
Revised manuscript received: January 26, 2018
Accepted manuscript online: January 27, 2018
[8] “Organic and Main Group Chemistry of the 2,4,6-Tris(trifluoromethyl)-
phenyl Substituent”: F. T. Edelmann in Inorganic Fluorine Chemistry:
Version of record online: && &&, 0000
&
&
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
8
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
FULL PAPER
Fluorescent Compounds
Not so sensitive: An efficient synthetic
process that provides the first air-toler-
ant 1,8-bis(trifluoromethyl)-9-phos-
phaanthracene was developed. The CF3
groups not only stabilize the heavier an-
thracene skeleton but also aid prompt
construction of the phosphinine unit.
The isolable 9-phosphaanthracenes
showed fluorescence functionality, and
substituents at the 10 position could
promote plural forms of the crystal
structure (see figure).
Shigekazu Ito,* Kota Koshino,
Koichi Mikami*
&& – &&
CF3-Inspired Synthesis of Air-Tolerant
9-Phosphaanthracenes that Feature
Fluorescence and Crystalline
Polymorphs
Chem. Asian J. 2018, 00, 0 – 0
www.chemasianj.org
9
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ