Properties and structure of two fluorinated 1,10-phenanthrolines

Article abstract of DOI:10.1016/j.jfluchem.2015.02.011

We report the synthesis, X-ray structure, absorbance and emission of 4,7-bis(4-fluorophenyl)-1,10-phenanthroline and 4,7-bis-(4′-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline. 4,7-Bis(4-fluorophenyl)-1,10-phenanthroline was synthesized by successive Skraup reactions and features absorbance at 274 nm and emission at 384 nm while 4,7-bis-(4′-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline featured absorbance at 283 nm and emission at 400 nm. The structures show molecular stacking of the phenyl groups and phenanthroline structure and longitudinal fluorine atom associations within the crystal lattice. Furthermore, the three fused rings of the 4,7-bis(4-fluorophenyl)-1,10-phenanthroline unit exhibited torsion up to 13.97(9)° throughout the crystal lattice whereas no torsion is observed for 4,7-bis-(4′-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline.

Full text of DOI:10.1016/j.jfluchem.2015.02.011

Journal of Fluorine Chemistry 173 (2015) 63–68
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Properties and structure of two fluorinated 1,10-phenanthrolines
b
b
c
Brenden Carlson a, , Sarah Flowers , Werner Kaminsky , Gregory D. Phelan
*
a Seattle Polymer Company, 454 North 34th Street, STE 100, Seattle, WA 98103, United States
b X-ray Laboratory, Chemistry Department, University of Washington, Box 351700, Seattle, WA 98195, United States
c Chemistry Department, State University of New York College at Cortland, Cortland, NY 13045, United States
A R T I C L E I N F O
A B S T R A C T
Article history:
We report the synthesis, X-ray structure, absorbance and emission of 4,7-bis(4-fluorophenyl)-1,10-
phenanthroline and 4,7-bis-(40-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline. 4,7-Bis(4-fluoro-
phenyl)-1,10-phenanthroline was synthesized by successive Skraup reactions and features absorbance
at 274 nm and emission at 384 nm while 4,7-bis-(40-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthro-
line featured absorbance at 283 nm and emission at 400 nm. The structures show molecular stacking of
the phenyl groups and phenanthroline structure and longitudinal fluorine atom associations within the
crystal lattice. Furthermore, the three fused rings of the 4,7-bis(4-fluorophenyl)-1,10-phenanthroline
unit exhibited torsion up to 13.97(9)8 throughout the crystal lattice whereas no torsion is observed for
4,7-bis-(40-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline.
Received 12 December 2014
Received in revised form 18 February 2015
Accepted 20 February 2015
Available online 1 March 2015
Keywords:
Fluorination
Biphenyl
Phenanthroline
Skraup
ß 2015 Elsevier B.V. All rights reserved.
X-ray
Structure
1. Introduction
reports we used phosphorescent metal-phenanthroline complexes
in a fluorinated polymer as oxygen sensors [6], and we reported
1,10-Phenanthrolines are a widely used class of hetero aromatic
compounds that consist of a central structure of three fused rings
with adjacent nitrogen atoms. Historically, 1,10-phenanthrolines
were produced using ortho-nitroaniline as the initial compound,
and as such, the 1,10-phenanthroline structure is sometimes
referred to as ortho-phenanthroline. This class of compounds is
commonly used by themselves or for chelation of Lewis acid
centers such as the ions of metals. 1,10-Phenanthrolines have
found applications in enzyme inhibition [1], in the creation of
luminescent compounds with a wide variety of metal centers [2],
in the photometric determination of the ferrous ion and in the
determination of organometallic reagents [3], and in various types
of organic electronics [4].
Phenanthroline compounds (either as single molecules or as
coordination ligands) are extensively used materials, and fluorina-
tion has become popular in recent years due to the electronic or
physical properties imparted by one or more fluorine atoms [5]. The
fluorinated phenanthrolines being reported were synthesized in an
attempt to increase compatibility with fluorinated polymeric
materials and as chelators for metal ions or atoms. In our previous
osmium fluorinated1,10-phenanthroline complexes in organiclight
emittingdevices [7]. Here, we reportthe physical characterizationof
two fluorinated 1,10-phenanthrolines: 4,7-bis(4-fluorophenyl)-
1,10-phenanthroline (1), and 4,7-bis-(40-trifluoromethyl-biphenyl-
4-yl)-1,10-phenanthroline (2).
2. Results and discussion
1 was synthesized by contacting 3-chloro-1-(4-fluoro-phenyl)-
propan-1-one with o-nitroaniline in a mixture of arsenic acid and
o-phosphoric acids by using successive Skraup reactions [8]. After
the first Skraup reaction, the nitro moiety was reduced to an amine
and the Skraup process repeated to yield the desired fluorinated
phenanthroline. Using a similar procedure to the synthesis of 1, a
brominated phenanthroline (4,7-bis(4-bromophenyl)-1,10-phe-
nanthroline) was synthesized and subsequently reacted with
trifluoromethanebenzene boronic acid in a palladium mediated
coupling to yield 2 (Fig. 1). The identity of species 1 and 2 was
confirmed by mass spectrometry, 1H NMR, and single crystal X-ray
crystallography.
The absorbance, emission, and excitation of 1 and 2 are shown in
the supplementary materials. 1 features an absorbance peak at
274 nm with an extinction coefficient of 40,000 ꢀ 10% L molꢁ1 cmꢁ1
at 20 8C and 2 has an absorbance peak at 283 nm with an extinction
*
Corresponding author. Tel.: +1 2066052633.
E-mail address: wcarlson@seattlepolymer.com (B. Carlson).
http://dx.doi.org/10.1016/j.jfluchem.2015.02.011
0022-1139/ß 2015 Elsevier B.V. All rights reserved.

64
B. Carlson et al. / Journal of Fluorine Chemistry 173 (2015) 63–68
Cl
Cl
Mg
O
X
X
Br
X
MgBr
THF, 0 oC
-MgBrCl
THF, Δ
X
NH2
O
N+
O-
Cl
SnCl2
H3AsO4
H3PO4
EtOH, reflux
NO2
O
N
100-150 oC
X
X
Cl
X
X
O
H3AsO4
H3PO4
N
N
100-150 oC
N
NH2
X = F (1), Br
F3C
CF3
Br
Br
F3C
B(OH)2
Pd(TPP)4; DMF
N
N
N
N
K2CO3; H2O, 100 oC
(2)
Fig. 1. Method to produce compounds 1 and 2.
coefficient of 60,000 ꢀ 10% L molꢁ1 cmꢁ1 at 20 8C. 1 has an extinction
coefficient of 13,500 L molꢁ1 cmꢁ1 at 300 nm which is similar to other
phenyl derivatives [9]. 2 has a bathochromic shift and increased
absorbancestrengthfromthatof1, bothofwhichareconsistentwith its
larger p structure. Both 1 and 2 are luminescent at 20 8C at a
concentration of 1.28 ꢂ 10ꢁ6 and 4.37 ꢂ 10ꢁ6 mol Lꢁ1 respectively.
The luminescence of 1 is mostly in the UV. The structured Gaussian
emission for 1 peaks at 384 nm and has a fwhm of 53 nm. 2 has
emission that peaks at 400 nm with a fwhm of 61 nm. The bath-
ochromic shift in the emission of 2 is consistent with the larger p
Fig. 2. Single crystal X-ray structure for 1 with 75% probability spheres. Hydrogen atoms removed for clarity.

B. Carlson et al. / Journal of Fluorine Chemistry 173 (2015) 63–68
65
Table 2
structure of the molecule. The excitation is measured at the previously
˚
Selected bond lengths [A] for 4,7-bis(4-fluorophenyl)-1,10-phenanthroline (1) and
4,7-bis-(40-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline (2).
stated concentrations and closely follows the UV–vis absorbance for
each compound.
Bond system
Compound 1
Compound 2
The X-ray structure of 1 is shown in Fig. 2. Refinement details of
the structure are listed Table 1 and selected bond lengths are given
in Table 2. Clear, colorless, crystals of the compounds were grown
from benzene–dimethylformamide. The 4-fluorophenyl groups
present in 1 show considerable rotation with respect to the three
fused rings of the 1,10-phenanthroline structure. A short single
bond between the phenanthroline and 4-flurophenyl rings allows
for rotation of the phenyl moiety. The single bond between C5–C7
F–C
F(1)–C(12) 1.3616(11)
N(1)–C(1) 1.3244(12)
N(1)–C(2) 1.3583(11)
C(7)–C(5) 1.4841(12)
C(5)–C(3) 1.3814(13)
C(5)–C(4) 1.4271(12)
C(4)–C(6) 1.4388(12)
C(6)–C(6)a 1.3625(18)
N.A.
F(1)–C(25) 1.313(3)
N(1)–C(1) 1.321(3)
N(2)–C(10) 1.327(3)
C(3)–C(13) 1.483(3)
C(2)–C(3) 1.379(3)
C(3)–C(4) 1.426(3)
C(4)–C(5) 1.414(3)
C(11)–C(12) 1.353(3)
C(16)–C(19) 1.484(3)
C(22)–C(25) 1.495(4)
N5C (phenanthroline)
N5C (phenanthroline)
Phenanthroline-phenyl
Phenanthroline C5C
Phenanthroline C5C
Phenanthroline C5C
Phenanthroline C5C
Biphenyl C–C
˚
˚
is 1.4841(12) A which is somewhat shorter than 1.5 A expected for
a ‘‘normal’’ C–C single bond between phenyl rings. In the 1
molecule, the phenyl group C7–C12 shows a rotation of 52.43 (13)8
with respect to the quasi-planar phenanthroline group C1–C4
along the 4 atom system C4–C5–C7–C9. A non-negligible torsion is
observed within the fused phenanthroline system throughout the
crystal lattice. The torsion angle between N1i–C2i–C2–N1 is
13.97(9)8 and C4i–C6i–C6–C4 is 5.37(9)8 within the fused ring
system of the phenanthroline.
Phenyl–CF3
N.A.
a
Symmetry transformation used to generate equivalent atom: ꢁx, y, ꢁz +1/2.
1 is related to the common industrial chemical bathophenan-
throline which has two reported crystal structures [10]. 1,
however, packs into a different lattice for the observed molecular
order than bathophenanthroline, which allows for Fꢃ ꢃ ꢃF associa-
tions that are not present in bathophenanthroline. We can
distinguish between two types of inter Fꢃ ꢃ ꢃF associations: side
by side associations due to molecular stacking in addition to
longitudinal associations between pairs (Fig. 3). In the bath-
ophenanthroline reports it was noted that the phenanthroline
units of a few of the molecules exhibited non-negligible torsions of
the three fused rings similar to what is observed for 1. However, 1
is different in that the torsion is observed for all fused ring systems
inside the lattice.
The unit cell of 1 as seen in Fig. 3 contains offset pairs of the
molecule. Neither of the crystal growth solvents benzene nor
dimethylformamide is present in the lattice. Two distinct
interactions between the molecules are observed in the unit cell.
The first is electrostatic
p–p molecular stacking of the aromatic
groups. The inter-molecular distance of the 4-fluorophenyl groups
˚
is 7.187 A. The phenanthroline moieties exhibit molecular stacking
˚
and are offset by about half of an A. The distance between
˚
phenanthroline moieties is 7.187 A. The phenanthroline moieties
are offset to allow for the molecular interactions between the 4-
fluorophenyl groups. The second interaction observed is between
The single crystal X-ray structure of compound 2 is shown in
Fig. 4. Refinement details of the structure are given in Table 1 and
selected bond lengths are given in Table 2. Clear, colorless crystals
of 2 were grown from chloroform. The phenyl groups present in 2
exhibit rotation with respect to the three fused rings of the 1,10-
phenanthroline structure and the trifluoromethylphenyl group is
rotated with respect to the phenyl moiety. The rotated geometry
can be explained by a short single bond between the phenanthro-
line and the biphenyl which allows for rotation of the phenyl
˚
the fluorine groups themselves with Fꢃ ꢃ ꢃF distances of 5.732 A,
which is a shorter intermolecular distance than the
˚
p stacking
distance of 7.187 A, and this Fꢃ ꢃ ꢃF interaction along with the
molecular stacking of the phenyl groups seem to cause intermo-
lecular phenanthroline moieties that are stacked upon each other
to be offset.
˚
moiety. The single bond between C3–C13 is 1.483(5) A and
Table 1
˚
between C16–C19 (connecting the phenyl moieties) 1.484(3) A
Crystal data and structure refinement for compounds 1 and 2.
˚
which are both somewhat shorter than 1.5 A expected for a
Property
1
2
‘‘normal’’ C–C single bond. In 2 the phenyl group attached to the
phenanthroline structure shows a rotation of 46.0(2)8 with respect
to the planar phenanthroline group C1–C4 along the 4 atom system
Empirical formula
C24 H14 F2 N2
0.0013
C39 H23 Cl3 F6 N2
0.0031
˚
C–C bond precision (A)
Formula weight
368.37
739.94
Temperature (K)
100(2)
100(2)
˚
Wavelength (A)
0.71073
0.71073
Crystal/color
Crystal system,
space group
Prism/colorless
Monoclinic, C 2/c
Piece/colorless
Monoclinic, C 2/c
Unit cell dimensions
˚
a (A)
11.0565(7)
7.1868(7)
21.0019(16)
90.00
17.3952(8)
10.8887(8)
34.418(2)
90
˚
b (A)
˚
c (A)
a
b
g
(8)
(8)
(8)
91.076(5)
90
100.104(4)
90
3
˚
Volume (A )
Density (mg/m3)
Independent
reflections
1668.5(2)
1.466
6418.0(7)
1.532
2580
1875
[R(int) = 0.0420]
[R(int) = 0.0365]
Final R indices
[I > 2sigma(I)]
R1
0.0398
0.1098
0.0519
0.1207
wR2
R indices (all data)
Fig. 3. Unit cell for 4,7-bis(4-fluorophenyl)-1,10-phenanthroline (1) crystals grown
R1
0.0477
0.1172
0.0629
0.1277
from benzene-DMF. The unit cell exhibits
p–p stacked molecules of the compound
wR2
as well as electrostatic interaction between the fluorine atoms.

66
B. Carlson et al. / Journal of Fluorine Chemistry 173 (2015) 63–68
Fig. 4. Single crystal X-ray structure of compound 2. Hydrogen has been removed and probability spheres are at 75%. The C38 trifluoromethyl group exhibits rotation due to
strong thermal activity.
C2–C3–C13–C14 and 42.2(2)8 along the C8–C9–C26–C31 system.
The two phenyl moieties are rotated to each other with an
observed rotation of 24.2(2)8 along the C15–C16–C19–C20 system
and 31.7(2)8 along the C30–C29–C32–C37 system. Unlike what is
observed for 1 or bathophenanthroline, very little torsion (ꢄ18) is
observed for the N1–C5–C6–N2 and for the C4–C11–C12–C7 atom
systems and as such the three fused rings of the phenanthroline
structure are nearly coplanar throughout the entire lattice.
structures and intermolecular attraction between the C–Fꢃ ꢃ ꢃF–C of
the trifluoromethyl groups. The energy of interaction between
trifluoromethyl groups is reported to be about 1.5 kcal/mol which
provides lattice energy toward the packing of the molecule
[11]. The distance between intermolecular CF3 groups ranges from
˚
3.124 to 3.575 A. The fused ring phenanthroline structure of 2
˚
completely stack on each other at a distance of 4.279 A at the
˚
nitrogen, and 4.494 A at the C11–C12 bridge with no offset
The phenanthroline molecules of
differently from 1 but share a common feature of molecular
stacking and fluorine association (Fig. 5). The intermolecular
2
arrange themselves
observed. Some biphenyl moieties do not exhibit molecular
stacking and the trifluoromethylphenyl groups are rotated
65.768 in respect to each other which results in a intermolecular
C22–C35 (aromatic carbon with the trifluoromethyl group
interactions of compound 2 are
p-stacking between the aromatic
˚
attached) distance of 5.236 A. Other biphenyl moieties are planar
to each other and molecularly stack at an intermolecular distance
˚
of 10.261 A. One in six of 2 ‘‘chelate’’ a single chloroform with a N–C
˚
distance of 3.044 and 3.302 A and the chloroform hydrogen was
found to hydrogen bond to both nitrogen atoms of the phenanthro-
line. The molecules of 2 are arranged in a sinusoidal like pattern
though longitudinal interactions between the CF3 groups.
3. Conclusion
The compound, 4,7-bis(4-fluorophenyl)-1,10-phenanthroline
has been successfully synthesized from o-nitroaniline, 4-fluoro-
bromobenzene and 3-chloropropionic acid chloride using succes-
sive Skraup reactions. The same reaction sequence was used to
synthesize a brominated phenanthroline followed by a coupling
reaction to yield 4,7-bis-(40-trifluoromethyl-biphenyl-4-yl)-1,10-
phenanthroline. 1 and 2 featured absorbance maximum of 274 nm
and 283 nm respectively and emission at 384 nm and 400 nm in
deoxygenated absolute ethanol at 20 8C. Single crystals of 1
Fig. 5. Unit lattice cell for compound 2 as viewed approximately along [1, 0, 1];
hydrogen omitted for clarity. The unit cell consists of six molecules of 2 that are
˚
stacked at an intermolecular distance of 4.279–10.261 A. The trifluoromethyl
˚
˚
moieties associate at a distance of 3.124 A–3.375 A. A chloroform unit is ‘‘chelated’’
˚
(not shown) by a unit of 2 at N–CCl3 distance of 3.044–3.302 A.

B. Carlson et al. / Journal of Fluorine Chemistry 173 (2015) 63–68
67
suitable for X-ray analysis were grown from benzene and DMF and
single crystals of 2 suitable for X-ray analysis were grown from
chloroform. The structures featured molecular stacking of the
three fused rings of the phenanthroline group as well as
longitudinal fluorine atom associations. The intermolecular Fꢃ ꢃ ꢃF
p-fluoro-3-chloropropriophenone (44.655 mmol) was added drop
wise. The solution was then heated to 140–150 8C and the solution
solidified. The solid was placed onto ice and brought to a pH of
12 followed by extraction with chloroform. The solid was
recrystallized from methanol–water to yield 7.343 g of 4,7-bis(4-
fluorophenyl)-1,10-phenanthrolineas a colorlesscrystalline solid. 1H
associations were of a shorter range than the intermolecular
p
stacking distances. Furthermore, the three fused rings of the 1,10-
phenanthroline of 1 unit exhibited torsion up to 13.97(9)8
throughout the crystal lattice whereas 2 featured no torsion of
the phenanthroline structure. More highly fluorinated phenan-
throline analogs can be synthesized using the methods discussed.
NMR (300 MHz, DOCD3, shown in the supplementary materials): d
9.3223(d, 2H, J = 4 Hz), 8.0996s, 2H), 7.9528(d, 2H, J = 5 Hz),
7.7775(m, 4H, J = 5 Hz), 7.4951(t, 4H, J = 9 Hz). Mass spectrometry
(ESI, shown in the supplementary materials) calculated for
C
C
24H14F2N2: 368.11; found 369.1223 for M+H. Anal. calcd for
24H14F2N2: C, 78.25; H, 3.83; F, 10.31; N, 7.60; found C, 77.78; H,
4. Experimental
3.87; N, 7.55.
4,7-Bis-(40-trifluoromethyl-biphenyl-4-yl)-1,10-phenanthroline.
Methods to synthesize 2 have been previously reported [13]. 1H
4-Fluorobromobenzene and 3-chloropropionic acid chloride
were purchased from Lancaster synthesis (now Alfa). Tin(II)
chloride, 4-fluorobromobenzene and o-nitroaniline were pur-
chased from Aldrich. Arsenic acid and o-phosphoric acid were
purchased from Alfa. All chemicals were used as received. Methods
to produce 2 using 4,7-bis-(4-bromophenyl)-1,10-phenanthroline
has been previously reported [12]. Absorbance was measured on
Shimadzu UV-1601 spectrophotometer. Emission and excitation
spectra of deoxygenated ethanol solutions were collected on
Photon Technologies, Inc. fluorescence spectrophotometer.
4,7-Bis-(4-fluorophenyl)-1,10-phenanthroline(1): (1) To an oven
dried 500 mL three neck flask equipped with stir bar, condenser,
and argon inlet was added 20,000 g of 4-fluorobromobenzene
(0.115 mol) and 200 mL of freshly distilled tetrahydrofuran.
5.555 g (0.230 mol) of freshly cleaned magnesium turnings was
added while under argon flow. The solution was gently heated
until the color changed to brown and visually half of the
magnesium was consumed. The resulting Grignard was then
canulated to a flask equipped with stir bar and argon inlet,
containing 14.982 g (0.118 mol) 3-chloropropionic acid chloride at
in 100 mL of freshly distilled tetrahydrofuran maintained at a
temperature of 0 8C on an ice bath. The Grignard was added over a
period of 90 min and stirred for 90 min after addition. The solvents
were then removed by rotary evaporation and the remaining solids
were flash chromatographed using methylene chloride and silica.
The resulting 3-chloro-1-(4-fluoro-phenyl)-propan-1-one was
used without further purification.
o-Nitroaminobenzene (5.00 g, 36.200 mmol), arsenic acid
(20.00 g, 52.000 mmol) and o-phosphoric acid (60 mL) were added
to a round bottom flask with stir bar and purged with nitrogen. The
solution was heated to 100 8C and a melt of 3-chloro-1-(4-fluoro-
phenyl)-propan-1-one (12.376 g, 66.320 mmol), was added drop
wise while maintaining the solution at 100 8C. The solution was
heated to 140–150 8C for 1.5 h and then cooled to 80 8C and poured
onto ice. The solution was then brought to a pH of 12 using K2CO3
and the organics were extracted from the aqueous phase using
methylene chloride. The contents were purified on basic alumina
(methylene chloride) to yield 9.890 g (36.870 mmol) of 4-(4-
fluorophenyl)-8-nitro-quinoline which was used without further
purification.
NMR (300 MHz, DMSO, shown in the supplementary materials):
d
9.1993(d, 2H, J = 1 Hz), 8.0133 (m, 10H, J = 9 Hz), 7.8699 (d, 4H,
J = 8 Hz), 7.7883 (m, 6H, J = 4 Hz). Mass spectrometry (ESI, shown
in the supplementary materials) calculated for C38H22F6N2:
620.1687; found 621.1742 for M+H, fragment found at
477.1563 which corresponds to cleavage of a trifluoromethylphe-
nyl group. Anal. calcd for C38H22F6N2: C, 73.54; H, 3.57; F, 18.37; N,
4.51; found C, 72.96; H, 3.65; N, 4.60.
Crystals of 1 suitable for X-ray analysis were grown from
benzene:dimethylformamide (90:10) while crystals of 2 were
grown from chloroform.
0.23 mm ꢂ 0.15 mm ꢂ 0.10 mm of 1 was mounted on a loop with
oil and clear colorless piece of
measuring 0.40 mm ꢂ
A clear colorless piece, measuring
a
2
0.30 mm ꢂ 0.05 mm was used. Data was collected at ꢁ173 8C on
a Bruker APEX II single crystal X-ray diffractometer, Mo-radiation.
Crystal-to-detector distance was 40.00 mm and exposure time
was 5 s per frame for all sets. The scan width was 0.58. Data
collection was 99.9% complete to 25.008 in W. A total of 52,225
reflections were collected covering the indices, h = ꢁ15 to 15,
k = ꢁ10 to 10, l = ꢁ30 to 30. 2580 reflections were symmetry
independent and the Rint = 0.0420 indicated that the data was
better than average quality (0.07) for 1. Indexing and unit cell
refinement indicated a monoclinic lattice. The space group was
found to be C 2/c (No.15).
Crystal-to-detector distance was 40 mm and exposure time was
10 s per frame for all sets for 2. The scan width was 0.58. Data
collection was 99.4% complete to 258 in W. A total of 151,750
reflections were collected covering the indices, h = ꢁ23 to 23,
k = ꢁ14 to 14, l = ꢁ46 to 46. 8033 reflections were symmetry
independent and the Rint = 0.0365 indicated that the data was
better than average quality (0.07). Indexing and unit cell
refinement indicated a C-centered monoclinic lattice. The space
group was found to be C 2/c (No. 15). The data was integrated and
scaled using SAINT, SADABS within the APEX2 software package by
Bruker [13].
Solution by direct methods (SHELXS, SIR97 [14]) produced a
complete heavy atom phasing model consistent with the proposed
structure. The structure was completed by difference Fourier
synthesis with SHELXL97 [15,16]. Both CF3 moieties for 2 show
strong thermal activities. The thermal activity of the CF3 resulted in
requiring the fluorine atoms be distributed over six instead of three
locations in one of them with site occupancy of 58% of the major
orientation. To stabilize the model, ISOR restraints were required
to avoid too oblate displacement ellipsoids. Scattering factors are
from Waasmair and Kirfel [17]. Hydrogen atoms were placed in
geometrically idealized positions and constrained to ride on their
4-(4-Fluorophenyl)-8-nitro-quinoline (9.890 g, 36.870 mmol)
was added to absolute ethanol (40 mL) and purged with argon. To
the 4-(4-fluorophenyl)-8-nitro-quinoline solution was added
tin(II) chloride (63.300 mmol) and was refluxed for 4 h. Aqueous
NaOH was added until a pH of 12 and the organics were extracted
using methylene chloride. The organics were then purified on basic
alumina (methylene chloride/methanol 99:1) to yield 7.067 g of
4-(4-fluoro-phenyl)-quinolin-8-ylamine which was used without
further purification.
˚
parent atoms with Cꢃ ꢃ ꢃH distances in the range 0.95–1.00 A.
Isotropic thermal parameters Ueq were fixed such that they were
1.2Ueq of their parent atom Ueq for CH’s and 1.5Ueq of their parent
atom Ueq in case of methyl groups. All non-hydrogen atoms were
refined anisotropically by full-matrix least-squares.
4-(4-Fluoro-phenyl)-quinolin-8-ylamine(7.067 g, 29.661 mmol),
arsenic acid (8.960 g, 23.333 mmol) and o-phosphoric acid (27 mL)
were heated to 100 8C under nitrogen. To this a melt of 8.333 g of

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B. Carlson et al. / Journal of Fluorine Chemistry 173 (2015) 63–68
(b) H.W. Lee, J. An, H. Yoon, H. Jang, N.G. Kim, Y. Do, Bull. Korean Chem. Soc. 26
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