Substitutent effects in the periphery of 2,9-bisaryl-tetraazaperopyrene dyes

Article abstract of DOI:10.1021/jo102141w

A series of 2,9-bisaryl-1,3,8,10-tetraazaperopyrene (TAPP) derivatives has been synthesized by reacting 4,9-diamino-3,10-perylenequinone diimine with a large excess of the corresponding benzoyl chloride in refluxing nitrobenzene. Among all derivatives only ortho-substituted phenyl congeners were sufficiently soluble for studying solutions of defined concentration in organic solvents. The molecular structures of the crystallized compounds, determined by X-ray diffraction of four derivatives, are determined by the planar tetraazaperopyrene core and the interplanar angle of the phenyl rings, which depends on the size of the ortho substituent (40-70°). The intermolecular packing pattern of all compounds is characterized by parallel stacks of molecules with the substituted phenyl rings rotated out of the peropyrene plane to reduce the steric repulsion. Crystals of a TAPP derivative suitable for X-ray diffraction were grown from trifluoroacetic acid (TFA) for the first time, establishing a 2-fold protonated species. The ground-state geometries of the TAPP derivatives were calculated by DFT [B3PW91/6-31g(d,p)] and the lowest unoccupied molecular orbital (LUMO) energies of derivatives possessing electron-withdrawing groups were decreased, as were the computed electron affinities. The results of the modeling study were confirmed experimentally by cyclic voltammetry to evaluate the substituent effects on the highest occupied molecular orbital (HOMO) and the LUMO of the peropyrene core. The UV-vis absorption spectra of all compounds recorded in trifluoroacetic acid are almost superimposable and display a characteristic visible absorption band between 460 and 490 nm (log ε = 4.64-5.01) with a strong vibrational progression of 1173-1475 cm^-1. Their fluorescence spectra are characterized by bands between 490 and 530 nm that are the mirror images of the absorption spectra (Stokes shifts of 10-50 nm). The luminescence quantum yields range from <0.01 to 0.30, thereby indicating a quenching effect for some substitution patterns.

Full text of DOI:10.1021/jo102141w

pubs.acs.org/joc
Substitutent Effects in the Periphery of 2,9-Bisaryl-tetraazaperopyrene Dyes
Susanne C. Martens, Till Riehm, Sonja Geib, Hubert Wadepohl, and Lutz H. Gade*
€
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
lutz.gade@uni-hd.de
Received October 29, 2010
A series of 2,9-bisaryl-1,3,8,10-tetraazaperopyrene (TAPP) derivatives has been synthesized by
reacting 4,9-diamino-3,10-perylenequinone diimine with a large excess of the corresponding benzoyl
chloride in refluxing nitrobenzene. Among all derivatives only ortho-substituted phenyl congeners were
sufficiently soluble for studying solutions of defined concentration in organic solvents. The molecular
structures of the crystallized compounds, determined by X-ray diffraction of four derivatives, are
determined by the planar tetraazaperopyrene core and the interplanar angle of the phenyl rings, which
depends on the size of the ortho substituent (40-70°). The intermolecular packing pattern of all compounds
is characterized by parallel stacks of molecules with the substituted phenyl rings rotated out of the
peropyrene plane to reduce the steric repulsion. Crystals of a TAPP derivative suitable for X-ray diffraction
were grown from trifluoroacetic acid (TFA) for the first time, establishing a 2-fold protonated species. The
ground-state geometries of the TAPP derivatives were calculated by DFT [B3PW91/6-31g(d,p)] and the
lowest unoccupied molecular orbital (LUMO) energies of derivatives possessing electron-withdrawing
groups were decreased, as were the computed electron affinities. The results of the modeling study were
confirmed experimentally by cyclic voltammetry to evaluate the substituent effects on the highest occupied
molecular orbital (HOMO) and the LUMO of the peropyrene core. The UV-vis absorption spectra of all
compounds recorded in trifluoroacetic acid are almost superimposable and display a characteristic visible
absorption band between 460 and 490 nm (log ε = 4.64-5.01) with a strong vibrational progression of
1173-1475 cm-1. Their fluorescence spectra are characterized by bands between 490 and 530 nm that are
the mirror images of the absorption spectra (Stokes shifts of 10-50 nm). The luminescence quantum yields
range from <0.01 to 0.30, thereby indicating a quenching effect for some substitution patterns.
Introduction
class of aromatics derived from the peropyrene family
in which four of the CH groups of the heptacyclic
Recently, there has been a resurgence in interest in the
chemistry of polycyclic aromatic hydrocarbons (PAHs)1
due to their manifold applications in electronic and opto-
electronic devices, such as light-emitting diodes, field-
effect transistors (FETs), and solar cells.2-4 The work
reported herein is concerned with a new polyheterocyclic
(1) (a) Harvey, R. G. Polycyclic Aromatic Hydrocarbons; Wiley-VCH:
New York, 1997. (b) Topics in Current Chemistry; de Meijere, A., Ed.;
Springer: Berlin, 1998; Vol. 196, Carbon Rich Compounds I. (c) Topics in
Current Chemistry; de Meijere, A., Ed.; Springer: Berlin, 1999; Vol. 201,
Carbon Rich Compounds II: Macrocyclic Oligoacetylenes and Other Line-
arly Conjugated Systems.
DOI: 10.1021/jo102141w
r
Published on Web 12/23/2010
J. Org. Chem. 2011, 76, 609–617 609
2010 American Chemical Society

Martens et al.
JOCArticle
hydrocarbon peropyrene (I) have been replaced by nitro-
gen atoms (III).
found to have nucleotide base-dependent emission behavior,
and Stang et al. reported the use of diazaperopyrene as a
difunctional molecular spacer in the construction of poly-
nuclear molecular squares by connecting square planar PdII
or PtII complex fragments.9 In these applications, the low
solubility of the dye molecules limits the practability of their
use as molecular building blocks.10
Recently, we developed an efficient metal-induced synth-
esis of 4,9-diamino-3,10-perylenequinone diimine (DPDI) by
oxidative coupling of two 1,8-diaminonaphthalene units11
and demonstrated their almost quantitative conversion to
derivatives of tetraazaperopyrene (TAPP),12 which are poten-
tially interesting materials for the application in organic elec-
tronic devices, in particular as n-channel semiconductors.
The low solubility of the parent compound precluded the
investigation of its photophysical properties and reactivity in
solution, which is why it has been extensively studied on
metal surfaces to date.13 Apart from their potential use as
organic semiconducting materials, appropriately substituted
tetraazaperopyrenes may act as functional dyes, since they
display a rich photo and redox chemistry. In this work, we
report the synthesis and characterization of new 2,9-bisaryl-
substituted tetraazaperopyrene derivatives. Electron-with-
drawing groups, such as F, Cl, Br, and CF3, were introduced
into the periphery of the aryl substituents. By changing the
position and the number of the substituents, we were able to
study the relationship between the substitution pattern in the
periphery of the aryl substitutent and the photophysical and
redox-chemical properties of the compounds. The nonhalo-
genated 2,9-bis-phenyl-1,3,8,10-tetraazaperopyrene and the
alkyl substituted 2,9-bis(2,4,6-trimethylphenyl)-1,3,8,10-tet-
raazaperopyrene were included for comparison.
Peropyrene (I) itself is a highly efficient fluorophore with
a quantum yield that approaches unity when dissolved in
benzene and was first synthesized by Clar in 1943, by reduc-
tive coupling of two molecules of perinaphthenone.5 Its elec-
tronic structure and photophysics have been studied exten-
sively in recent years.6 In contrast to the latter, diazapyrene
(II) has been known much longer. It was first described in the
literature in a German patent in 1913, and its derivatives
have found applications as functional dyes.7 The dimethyl-
diazaperopyrenium dicationic derivative interacts strongly
with nucleotides, nucleosides, and single-stranded nucleic
acids and effects their photocleavage.8 Notably, it was also
€
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(1-7) was achieved by reacting DPDI with a large excess of
the corresponding benzoyl chloride in refluxing nitroben-
zene (Scheme 1). Purification was accomplished either by
sublimation at 440 °C in a weak stream of nitrogen (1-3, 6a, 7)
or by recrystallization from nitrobenzene (6b-e). The
purity of the compounds was determined by elemental analysis,
and their structures were established by NMR spectroscopy.
Derivatives 1-7 represented in Scheme 1 may be divided
into three different groups: phenyl substituted (1), alkyl-
phenyl substituted (2), and halogenated aryl substituted
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SCHEME 1. Synthesis of 2,9-Bisaryl-1,3,8,10-tetraazapero-
pyrene Derivatives
As expected, the interplanar angles show a dependence on
the size of the ortho substituent (see Table 1). Interesting to
note is the difference of the interplanar angle in the crystal
structures of 6a, 6b, and 7b, which all contain fluorine atoms
in both ortho positions of the phenyl substituent on the one
hand and the deviation of the interplanar angles in the two
independent molecules of the solid state structures of 3 and
6b (3, 73.83° vs 86.13°; 6b, 65.87° vs 57.25°) on the other
hand. These observations can be taken as an indication for a
shallow potential energy minimum for the rotational orien-
tation of the aryl substituents.
The intermolecular packing pattern of all compounds is
characterized by parallel stacks of molecules. The interpla-
nar distances between the aromatic cores of neighboring
˚
molecules within a column lie in the range of about 3.4 A for
all structures. This value is close to the π-π stacking distance
of 3.37 A found in graphite,16 and is also in good accordance
˚
˚
with the range of 3.34-3.55 A previously established for
perylene bisimides.17
The relative orientation of the individual molecules within
the stacks is governed by the steric requirements of the
substituted phenyl rings. Neighboring molecules of 3, for
instance, are rotated by 43° within the molecular plane with
respect to one another (Figure 2), while they are superposed in
the case of 6a. The differences in the packing efficiency are also
obvious from the Kitajgorodskij packing index15 (percentage
of filled space, Table 1).
tetraazaperopyrenes (3-7). The examination of the proper-
ties of these compounds was limited by their low solubility in
common organic solvents. The substitution in ortho position
of the phenyl group usually led to an increase in solubility.
Among all derivatives only ortho-substituted phenyl congeners
were sufficiently soluble for studying solutions of defined
concentration in organic solvents. This effect is probably due
to the twist of the aryl substituent, which is imposed by steric
repulsion between the ortho substituents and the peropyrene
core and impedes efficient aromatic stacking upon crystal-
lization (vide infra). A similar behavior has already been
observed by Langhals for o-phenyl substituted 3,4,9,10-
perylene bisimides.14
The views of molecular stacking chosen in Figure 2 illus-
trate how the larger interplanar angle of the phenyl ring
bearing a trifluoromethyl group in the ortho position leads to
˚
˚
the increased π-π stacking distance (3, 3.46 A vs 6b, 3.36 A)
as well as to the above-mentioned relative orientation of the
molecules within the stack. In both cases (3 and 6b) weak
intermolecular hydrogen bonds are found between the fluor-
ine atoms of the phenyl groups and the ortho hydrogen atoms
˚
of the peropyrene core of the neighboring molecules (3, 2.49 A,
˚
6b, 2.52-2.57 A).
Given the lack of solubility in organic solvents, NMR
spectra were recorded either in deuterated trifluoroacetic acid
or concentrated deuterated sulfuric acid, in which they readily
dissolved without decomposition. Irrespective of the substitu-
ents in position 2 and 9, the resonances observed in the 13C
NMR spectra are almost identical for the central polycon-
densed arene moiety. In the 1H NMR spectra CH proton reso-
nances of the peropyrene core were detected between 10.44
and 10.76 ppm (Ha) and 9.21 and 9.41 ppm (Hb) with coupling
constants ranging from 9.3 to 9.7 Hz for all compounds.
Crystal Structures. Crystals suitable for X-ray diffraction
of compounds 3, 6a, 6b, and 7b were grown by sublimation at
440 °C in a horizontal glass tube in a weak stream of
nitrogen. All solid state structures show crystallographic Ci
molecular symmetry without exception. Their molecular
structures are determined by the planar tetraazaperopyrene
core with almost identical bond lengths and angles and the
phenyl substituents rotated out of the plane of the polycyclic
molecular core to reduce the steric repulsion. As an example,
the top and side views of 6a are depicted in Figure 1.
A different situation is observed for the solid state structures
of 6a and 7b. In both crystal structures the molecules are
superposed within the stacks and the long axes of the molecules
in neighboring stacks are not parallel orientated but tilted along
the molecule axes relative to each other (herringbone arrange-
ment, Figure 3). This closely resembles the situation found for
the X-ray analyses of the recently published 2,9-bis(2-bromo-
phenyl)-1,3,8,10-tetraazaperopyrene.12
To date, all crystallographically characterized TAPP de-
rivatives were crystallized either by sublimation in a stream
of nitrogen (3, 6a, 6b, 7b) or from an organic solvent (2,9-
bis(2-bromophenyl)-1,3,8,10-tetraazaperopyrene). However,
in this study we were able to grow crystals of a TAPP derivative
suitable for X-ray diffraction from trifluoroacetic acid (TFA)
for the first time, thus allowing a closer examination of the
protonation pattern pertinent to the photophysical studies
in acids (vide infra). The solid state structure reveals a 2-fold
protonated species, which directly indicates the previously
proposed degree of protonation in this acidic solvent as
shown by titration for alkyl substituted TAPPs.12
€
(14) (a) Rademacher, A.; Markle, S.; Langhals, H. Chem. Ber. 1982, 115,
2927–2934. (b) Langhals, H.; Demming, S.; Huber, H. Spectrochim. Acta
1988, 44A, 1189–1193.
(16) Forrest, S. R.; Kaplan, M. L.; Schmidt, P. H. J. Appl. Phys. 1984, 55,
1492–1507.
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(17) Klebe, G.; Graser, F.; Hadicke, E.; Berndt, J. Acta Crystallogr., Sect.
B 1989, 45, 69–77.
(15) Kitajgorodskij, A. I. Molecular Crystals and Molecules; Head Press:
New York, 1973.
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FIGURE 1. Molecular structure of 6a: top view (top) and side view (bottom). Thermal ellipsoids were drawn at the 50% probability level.
TABLE 1. Selected Details of Crystal Structures of Compounds 3, 6a, 6b, and 7b
3
6a
6b
7b
crystal system
monoclinic
˚
3.46 A
73.82°/86.13°
38.67°
70.6%
monoclinic
˚
3.37 A
41.10°
47.74°
75.7%
triclinic
˚
3.36 A
65.87°/57.25°
48.98°
72.5%
monoclinic
˚
3.36 A
43.51°
48.34°
72.3%
π-π plane distance
interplanar angle (expt)a
interplanar angle (DFT)b
packing indexc
aInterplanar angle between the peropyrene core and the phenyl substituent; in the case of compound 3 and 6b two independent molecules with unequal
c
interplanar angles were observed in the single crystal. bCalculated at the B3PW91/6-31g(d,p) level of theory. Determined according to literature
methods.15
Although twinning of the crystals, severe disorder within the
trifluoromethyl groups, and an apparent rotational disorder
(presumably due to dynamic effects) of the pentafluorophenyl
groups, which could not be modeled accurately with a split-
atom model, restrained the structure determination, it was still
possible to determine the 2-fold protonation of the tetraaza-
peropyrene. Inspection of the internal geometry of the potential
trifluoroacetic acid and/or trifluoroacetate moieties revealed
the presence of two trifluoroacetate and six trifluoroacetic acid
molecules per molecule of H26a2þ. On the basis of the short
˚
contact distance of 2.80 A between N(1) and the oxygen of a
trifluoroacetic acid molecule (Figure 4), which lies in the range
of a N-H O hydrogen bond, N(1) was identified as the
3 3 3
protonation site N(1). The position of H(1) was indeed found
from a difference Fourier synthesis and could be refined
satisfactorily.
The protonated molecules are arranged in parallel stacks
along the shorter cell axis with an intermolecular stacking
˚
distance of 7.93 A and having solvent molecules placed between
the layers. On the basis of the repulsive coulomb interaction
between the (charged) protonated molecules, the dramatically
increased stacking distance as well as the incorporated solvent
molecules, the presence of π-π interaction can no longer be
assumed for this species.
Notably, no significant change of bond lengths and angles
of the tetraazaperopyrene core is observed comparing the
X-ray analyses of the unprotonated and protonated species.
Only the torsion angle of the phenyl substituent is clearly
increased (6a, 40.2° vs H26a2þ, 47.0°).
Theoretical Modeling of the Structures and Frontier Orbital
Levels. The ground-state geometries of the TAPP derivatives
were calculated at the B3PW91/6-31g(d,p) level of DFT,
followed by frequency analyses to verify the energy minima.
In general, the optimized structures were in good agreement
FIGURE 2. Crystal packing of 3 (top) and 6b (bottom) in the
crystal form showing the twisted arrangement of the aryl substitu-
ents and weak hydrogen interactions. Thermal ellipsoids were
drawn at the 30% probability level.
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FIGURE 3. Herringbone arrangement of the molecules of 7b in the crystal form.
FIGURE 4. Molecular structure of H26a2þ. Front view (top) and top view (bottom). Thermal ellipsoids were drawn at the 30% probability
level. Trifluoroacetate anion and all except one trifluoroacetic acid molecules have been omitted for clarity.
with the metric parameters of the crystallographically
characterized tetraazaperopyrene derivatives. Only the in-
terplanar angle of the aryl substituent deviated considerably
(Table 1), which is probably due to the fact that the calculations
were performed on single molecules in the gas phase.
Nevertheless for compounds 6a, 6b, and 7b the computational
studies reflect the qualitative trend of the interplanar angle, while
it is not surprising that the experimental value of the interplanar
angle of compound 3 is significantly different for the DFT
optimized and the crystal structure (X-ray, 71.4° vs DFT,
37.4°). Since the trifluoromethyl group is significantly larger than
a single fluorine atom, it will give rise to the strongest steric
hindrance, and therefore the intermolecular interactions in the
solid state are expected to be more relevant than for the fluorine
substituted derivatives as is also illustrated in Figure 2.
the fact that because of the symmetry of the core system all
frontier molecular orbitals have a nodal plane at the long axis
of the molecules, running through the substituted carbon
atoms. The calculated gas-phase lowest unoccupied molec-
ular orbital (LUMO) energies for the soluble derivatives are
summarized in Table 2. According to these calculations, a
trend on going from an alkyl-substituted aryl to a fluoro-
phenyl substituent is observed. The insertion of an electron-
withdrawing group leads to the expected decrease in LUMO
energy. In addition to that, the computed electron affinities
(EA) exhibit the same trend. EAs were determined by optimiz-
ing the structure of the anionic species, using the previously
optimized geometry of the neutral species as a starting point
and taking the difference of the total energies of both species
(see Supporting Information for the full set of Kohn-Sham
frontier molecular orbital energies and total energies for
all derivatives discussed in this work).
According to the calculations, the frontier molecular
orbital energies depend on the substitution pattern, despite
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TABLE 2. Cyclovoltammetric Data for Soluble Compounds
compound Ered1 [V]a Ered2 [V] ELUMO [eV]b ELUMO [eV]c EA [eV]c
2
3
6a
6b
-0.89
-0.86
-0.74
-0.81
-1.17
-1.14
-1.01
-1.09
-3.44
-3.50
-3.61
-3.55
-3.13
-3.23
-3.47
-3.17
2.06
2.15
2.37
2.06
aMeasured against SCE in CH2Cl2. bDetermined according to litera-
ture methods,18 using Fc/Fcþ as an internal standard. cCalculated at the
B3PW91/6-31g(d,p) level of theory.
FIGURE 6. Normalized UV-vis absorption spectra of compound
6a measured in diluted solutions (10-5 mol/L) in toluene (solid line),
TFA (dotted line), and concentrated sulfuric acid (dashed line).
TABLE 3. π*rπ Transition λmax [nm] and Vibrational Progression
Δν [cm-1] in the Absorption Spectra Recorded in TFA
λ
max (log ε) [nm],
λem (Stokes shift)
[nm]
compound
Δν [cm-1
]
φ
1
2
3
4
479 (4.94), 1395
478 (4.81), 1209
478 (4.90), 1401
478 (4.89), 1401
483 (4.80), 1420
478 (4.97), 1401
479 (5.01), 1395
479 (4.64), 1445
480 (4.90), 1438
480 (4.93), 1438
481 (4.89), 1432
479 (5.04), 1395
519 (40)
491 (13)
490 (12)
490 (12)
529 (46)
491 (13)
496 (17)
511 (32)
507 (27)
504 (24)
520 (39)
520 (41)
0.03
<0.01
0.30
0.02
FIGURE 5. Cyclic voltammogram of 6a recorded in CH2Cl2
5
<0.01
0.29
0.06
0.17
0.16
0.15
<0.01
0.05
(sweep rate 50 mV s-1; supporting electrolyte Bu4NPF6).
6a
6b
6c
6d
6e
7a
7b
To put these results of our theoretical modeling to an experi-
mental test, we employed cyclic voltammetry to evaluate the
substituent effects on the highest occupied molecular orbital
(HOMO) and the LUMO of the peropyrene core. The cyclic
voltammograms of the soluble derivatives (2, 3, 6a, 6b) displayed
two reversible one-electron reduction waves that correspond to
the sequential formation of the mono- and dianionic species. The
electrochemical data are summarized in Table 2.
The cyclic voltammogram of 6a (Figure 5) displays two
reversible redox waves with half wave potentials at Ered1=-0.74 V
and Ered2=-1.01 V (vs SCE) with a difference between the
cathodic and anodic wave of about 70 mV in each case. The
observation of an ia/ic ratio of exactly 1 and a relationship of
ip ≈ ν1/2 indicate the reversibility of the electrochemical
process. Recording the CV in the presence of ferrocene as
an internal standard established them to be two one-electron
reductions and in addition to that allowed the estimation of
the LUMO energy levels.18
are yellow to brown in the solid state and yellow to orange in
solution, depending on the concentration. Because of their
lack of solubility in common organic solvents, a systematic
study of the optical properties for all derivatives was con-
ducted in trifluoroacetic acid (TFA). The UV-vis absorp-
tion spectra of compounds 1-7 recorded in neat TFA are
almost superimposable. They display a characteristic visible
absorption band between 460 and 490 nm (log ε=4.64-5.01,
Table 3). The band is characterized by a strong vibrational
progression of about 1173-1475 cm-1 as it is typical for π*rπ
transition in polycondensed aromatics and in particular
for perylene derivatives.19 The absence of, basically, any
effect of the substituents in position 2 and 9 on the absorption
spectra indicates that their influence on the HOMO-LUMO
gap of the tetraazaperopyrene core is negligible, as we already
observed previously for the alkyl substituted derivatives.12 As
noted above, this is due to the fact that a nodal plane in the
The comparison of the experimental values reveals a de-
crease of the LUMO energies of the derivatives bearing a
fluorophenyl substituent (2, -3.44 eV vs 6a, -3.61 eV). This
observation confirms the assumption that by insertion of
electron-withdrawing groups such as fluoro substituted phenyl
a stabilization of the mono- and dianionic species is achieved.
By increasing the number of the highly electronegative fluorine
substituents on the phenyl group, the electron-withdrawing
capability of the phenyl substituent and therefore the stabiliza-
tion of the mono- and dianionic species is enhanced. A similar
(18) Seguy, I.; Jolinat, P.; Destruel, P.; Mamy, R.; Allouchi, H.;
Courseille, C.; Cotrait, M.; Bock, H. ChemPhysChem 2001, 7, 448–452.
(19) (a) Feiler, L.; Langhals, H.; Polborn, K. Liebigs Ann. 1995, 1229–
1244. (b) Langhals, H. Helv. Chim. Acta 2005, 88, 1309–1343. (c) Sadrai, M.;
€
€
Bird, G. R. Opt. Commun. 1984, 51, 62–64. (d) Lohmannsroben, H. G.;
Langhals, H. Appl. Phys. B: Laser Opt. 1989, 48, 449–452. (e) Ford, W. E.;
Kamat, P. V. J. Phys. Chem. 1987, 91, 6373–6380. (f) Rohr, U.; Schlichting,
situation was observed by Chen and Bao et al.4a and Wurthner
€
et al.4b for perylenebisimides.
€
€
€
P.; Bohm, A.; Gross, M.; Meerholz, K.; Brauchle, C.; Mullen, K. Angew.
Chem. 1998, 110, 1463–1467; Angew. Chem., Int. Ed. 1998, 37, 1434-1437.
(g) Langhals, H.; Karolin, J.; Johannson, L. B. A. J. Chem. Soc., Faraday
Trans. 1998, 94, 2919–2922.
UV-vis Absorption Spectra and Emission Behavior. All of
the tetraazaperopyrene derivatives 1-7 reported in this work
614 J. Org. Chem. Vol. 76, No. 2, 2011

Martens et al.
JOCArticle
TABLE 4. LUMO Energies of Fluorine Substituted TAPP Derivates and Compounds 1 and 2 as References, Calculated at the B3PW91/6-31g(d,p)
Level of Theory, Listed in Order of Their Energy Level
aCalculated at the B3PW91/6-31g(d,p) level of theory.
HOMO and LUMO is present running through the carbon
atoms 2 and 9. Exemplary studies in toluene, trifluoroacetic
acid, and sulfuric acid have been carried out with compound 6a
to verify the protonation steps (Figure 6).12
On going from an organic solvent to TFA the protonation
of two nitrogen atoms occurs, whereas the protonation of all
four nitrogen atoms is achieved in an even more acidic medium
such as concentrated sulfuric acid.
importantly, heavy atoms such as chlorine and bromine seem
to cause fluorescence quenching, which is a known but as yet
incompletely understood phenomenon.22
The highest quantum yields of around 30% were found for
the perfluorophenyl substituted TAPP derivative 6a and the
2-trifluoromethyl phenyl substituted derivative 3. Interest-
ingly, the location of the fluorine substituents on the phenyl
group seems to be of importance. Whereas derivates 6b and
7b, in particular, with the same sterical hindrance regarding
the phenyl rotation, exhibited an emission quantum yield of
5-6%, the emission of compounds 6c-e occurred with
quantum yields of up to 17%, indicating a positive effect of
the fluorine atoms in the meta and para positions of the
phenyl ring. This observation is further supported by the
comparison of 5, 7a, and 7b. Whereas the fluorescence of
5 and 7a appeared to be quenched (Φ=<1%) probably as a
result of the bromine sustituent, derivative 7b exhibited an
emission quantum yield of approximately 5%. The same
effect is observed comparing 6b (Φ = 6%) with 6c-e (Φ=
15-17%).
The theoretical modeling of the energy levels (Table 4) also
indicated a special effect of the ortho and para substituents,
since the LUMO energies of TAPP derivatives bearing
fluorine substituents in the meta or para position are low-
ered, with the effect of the meta substituent being stronger. In
Table 4 the fluorine substituted TAPP derivatives (and
compound 1 and 2 for comparison) are listed in order of
decreasing LUMO energy level. The fluorescence quantum
yields of the TAPP derivatives increased with decreasing
LUMO energy, with the exception of 7a and 7b, which both
contain a bromo substituent (see discussion above), and
compound 3. For the latter neither the optimized structure
nor the calculated LUMO energies are in good accordance
with the experimental data. As already discussed above, this
is probably due to intermolecular interactions that we were
not able to model adequately with our methods.
The fluorescence spectra of compounds 1-7 recorded in
TFA are characterized by an emission band between 490 and
530 nm with the characteristic vibrational progression (Table 3).
The emission spectra display the mirror symmetry of the absor-
bance spectra with Stokes shifts of 10-50 nm. The lumi-
nescence quantum yields range from <0.01 to 0.30, thereby
indicating a quenching effect for some substitution patterns.
In an early study, Langhals et al. found that the quantum
yields observed for different phenyl substituted perylenebi-
simides are dependent on the steric hindrance in ortho
position, since the rotation of the phenyl substituents is a
favored pathway for the radiationless deactivation of excited
molecules.14 For our systems, we observed that the electronic
structure of the molecules 1-7 had a significant influence on
the quantum yields. Most recently, Flamingi and Langhals et
al. reported on a similar effect, focusing on the mechanism of
luminescence quenching by different electron-rich substituents.20
The enhancement of solubility by forcing an expanded
polycyclic aromatic system in a twisted conformation and
thereby inhibiting the molecular stacking is an effect reported
€
by Wurthner et al. for their core substituted perylenbis-
imides.21 As it turns out, for the TAPP derivatives a sterically
more demanding ortho substituent does not automatically lead
to a greater increase of solubility. While the insertion of a
fluorine atom, an alkyl group or a perfluorinated alkyl group
induced a significant enhancement of solubility in comparison
to the unsubstituted 2,9-bis-phenyl-1,3,8,10-tetraazaperopyr-
ene, only a slight improvement was observed for derivatives
bearing a chlorine or bromine atom in ortho position. More
Therefore, we assume that in the case of 3, the higher
emission quantum yield is more specifically related to steric
effects that result in a significant improvement of solubility
(20) Flamigni, L.; Ventura, B.; Barbieri, A.; Langhals, H.; Wetzel, F.;
Fuchs, K.; Walter, A. Chem.;Eur. J. 2010, 16, 13406–13416.
€
(21) See for example: (a) Gsanger, M.; Hak, Oh, J.; Konemann, M.;
Hoffken, H. W.; Krause, A.-M.; Bao, Z.; Wurthner, F. Angew. Chem. 2010,
€
€
€
€
122, 752–755; Angew. Chem., Int. Ed. 2010, 49, 740-743. (b) Wurthner, F.
Chem. Commun. 2004, 1564–1579. (c) Chen, S.; Debije, M. G.; Debaerdemaeker,
€
T.; Osswald, P.; Wurthner, F. ChemPhysChem 2004, 5, 137–140.
(22) (a) Lakowicz, J. R. Principles of Fluorescence Spectroscopy, 3rd ed.;
Springer: New York, 2006. (b) Martinho, J. M. C. J. Phys. Chem. 1989, 93,
6687–6692.
J. Org. Chem. Vol. 76, No. 2, 2011 615

Martens et al.
JOCArticle
and inhibition of aggregation rather than being due to the
electronic properties induced by the substituents.
2,9-Bis(2-trifluoromethyl-phenyl)-1,3,8,10-tetraazaperopyr-
ene (3). Acid chloride: 2-trifluoromethylbenzoyl chloride. Yield:
300 mg (0.5 mmol; 49%) of 3 as a yellow powder. H NMR
1
(600.13 MHz, TFA-d1) δ 10.54 (d, 4H, 3J=9.5 Hz, Hb), 9.22 (d,
4H, 3J=9.3 Hz, Ha), 8.05 (d, 2H, 3J=7.9 Hz, HAr), 7.98-7.91
(m, 4H, HAr), 7.89 (t, 2H, 3J=7.2 Hz, HAr). 13C NMR (150.90
MHz, TFA-d1, 295 K) δ 159.7 (C7), 153.6 (C6), 141.1 (C4Hb),
135.5 (C11HAr), 134.7 (C12), 133.7 (C13), 132.4 (C3), 132.3
(quar, 2JCF=32.6 Hz, C9), 131.0 (C8), 129.9 (quar, 3JCF=4.8
Hz, C10HAr), 128.7 (C5Ha), 125.7 (quar, 1JCF=274.4 Hz, CF3),
122.8 (C2), 116.5 (C1). HRMS (MALDI): m/z calcd for
C36H17F6N4 619.1357, found 619.1352. Anal. Calcd for
C36H16F6N4: C 69.91, H 2.61, N 9.06. Found: C 70.00, H
2.90, N 9.06.
Conclusions
In this work we have presented the synthesis and charac-
terization of a selection of aryl substituted tetraazaperopyr-
ene dyes. By growing crystals of a TAPP derivative suitable
for X-ray diffraction from TFA, we were able to prove the
previously postulated 2-fold protonation of the tetraazapero-
pyrene derivatives in this acidic solvent.
The effect of a series of electron-withdrawing substituents
on the periphery of an aryl group directly connected to a
tetraazaperopyrene on the electronic and optical properties
has been examined. The absorption and emission spectra,
almost superimposable for all compounds investigated, in-
dicated an insignificant effect of the substituents on the HOMO-
LUMO gap. In contrast to these observations, the fluores-
cence quantum yields range from approximately 1% to 30%,
thus displaying considerable dependence on the electronic
properties of the substituent. This is in accordance with the
results of a theoretical modeling of their energy levels, which
revealed that the insertion of electron-withdrawing groups
leads to a decrease of, particularly, the LUMO energies.
The computed LUMO energies and electron affinities of the
TAPP derivatives and the possibility to increase them further
by introduction of electron-withdrawing substituents at the
central aromatic core makes these materials promising candi-
dates for the development of organic n-channel semiconduc-
tors. Such work is currently under way in our laboratory.
2,9-Bis(2,6-dichloro-phenyl)-1,3,8,10-tetraazaperopyrene (4).
Acid chloride: 2,6-dichlorobenzoyl chloride. Yield: 407 mg
1
(0.7 mmol; 66%) of 4 as a brown powder. H NMR (600.13
MHz, TFA-d1) δ 10.76 (d, 4H, 3J=9.6 Hz, Hb), 9.46 (d, 4H, 3J=
9.3 Hz, Ha), 7.81 (m, 6H, HAr). 13C NMR (150.92 MHz, TFA-
d1, 295 K) δ 157.0 (C7), 154.0 (C6), 141.2 (C4), 137.0 (C8), 136.7
(C11), 132.6 (C3), 131.5 (C9), 131.1 (C10), 128.8 (C5), 122.9
(C2), 116.8 (C1). HRMS (FAB): m/z calcd for C34H15N4Cl4
619.0051, found 619.0081.
2,9-Bis(4-bromo-phenyl)-1,3,8,10-tetraazaperopyrene (5).
Acid chloride: 4-bromobenzoyl chloride. Yield: 477 mg (0.7
mmol; 57%) of 5 as a yellow powder. 1H NMR (600.13 MHz,
TFA-d1) δ 10.47 (d, 4H, 3J=9.6 Hz, Hb), 9.23 (d, 4H, 3J=9.2 Hz,
3
3
Ha), 8.59 (d, 4H, J = 8.3 Hz, HAr), 8.01 (d, 4H, J=8.8 Hz,
H
Ar). 13C NMR (150.92 MHz, TFA-d1, 295 K) δ 158.7 (C7),
154.2 (C6), 140.0 (C4Hb), 135.8 (C10HAr), 133.7 (C11), 132.5
(C9HAr), 131.8 (quar, C3), 130.5 (C8), 128.6 (C5), 123.0 (C2),
116.1 (C1). HRMS (EI): m/z calcd for C34H16N4Br2 637.9742,
found 637.9764. Anal. Calcd for C34H16N4Br2: C 63.77, H 2.52,
N 8.75. Found: C 63.73, H 2.62, N 8.69.
Experimental Section
2,9-Bis(2,3,4,5,6-pentafluoro-phenyl)-1,3,8,10-tetraazapero-
pyrene (6a). Acid chloride: 2,3,4,5,6-pentafluorobenzoyl chlo-
ride. Yield: 434 mg (0.7 mmol; 66%) of 6a as an orange powder.
General Procedure for the Preparation of the Tetraazapero-
pyrene (TAPP) Derivatives. To a suspension of 310 mg (1 mmol)
of 4,9-diaminoperylene-quinone-3,10-diimine (DPDI)11 in 25
mL of nitrobenzene was added 12 mmol of the corresponding
acid chloride, and the mixture was heated to reflux for 6 h. The
mixture was allowed to cool to room temperature. The resulting
suspension was filtered and washed several times with acetone,
ethanol, and finally pentane (200 mL). The brown solids were
either recrystallized from nitrobenzene or purified by sublima-
tion at 440 °C in a nitrogen stream.
2,9-Bis-phenyl-1,3,8,10-tetraazaperopyrene (1). Acid chloride:
benzoyl chloride. Yield: 381 mg (0.8 mmol; 79%) of 1 as an orange
powder. 1H NMR (600.13 MHz, TFA-d1) δ 10.56 (d, 4H, 3J=
9.6 Hz, Hb), 9.33 (d, 4H, 3J=9.4 Hz, Ha), 8.77 (d, 4H, 3J=7.6
Hz, HAr), 8.03 (t, 2H, HAr), 7.95 (t, 4H, HAr). 13C NMR (150.92
MHz, TFA-d1, 295 K) δ 159.9 (C7), 154.3 (C6), 140.2 (C4Hb),
137.7 (C11), 132.5 (C10HAr), 132.0 (C8), 131.9 (C3HAr), 131.6
(C9H Ar), 128.7 (C5Ha), 123.1 (C2), 116.3 (C1). HRMS (EI): m/z
calcd for C34H18N4 482.1531, found 482.1506. Anal. Calcd for
C34H18N4: C 84.63, H 3.76, N 11.61. Found: C 84.34, H 3.72,
N 11.50.
3
1H NMR (600.13 MHz, TFA-d1) δ 10.71 (d, 4H, J=9.4 Hz,
Hb), 9.32 (d, 4H, 3J=9.3 Hz, Ha). 13C NMR (150.92 MHz, TFA-
d1, 295 K) δ 154.2 (C7), 149.8 (C6), 148.0, 148.1 (C9/C11), 141.0
(C10), 140.9 (C4Hb), 132.5 (C3), 129.0 (C5Ha), 122.8 (C2), 116.6
(C1), 109.2 (C8). HRMS (EI): m/z calcd for C34H8N4F10
662.0589, found 662.0545. Anal. Calcd for C34H8N4F10
(662.4): C 61.65 H 1.22 N 8.46. Found: C 61.37 H 1.35 N 8.47.
2,9-Bis(2,6-difluoro-phenyl)-1,3,8,10-tetraazaperopyrene (6b).
Acid chloride: 2,6-difluorobenzoyl chloride. Yield: 400 mg (0.7
mmol; 72%) of 6b as an orange powder. 1H NMR (600.13 MHz,
TFA-d1) δ 10.58 (d, 4H, 3J=9.6 Hz, Hb), 9.30 (d, 4H, 3J=9.4 Hz,
Ha), 7.85 (m, 2H, HAr), 7.33 (m, 4H, HAr). 13C NMR (150.92
MHz, TFA-d1, 295 K) δ 163.1 (dd, 1JCF = 257.3 Hz, 3JCF=4.9
Hz, C9), 153.9 (C6), 152.5 (C7), 140.8 (C4Hb), 139.1 (t, 3JCF
=
10.7 Hz, C11HAr), 132.4 (C3), 128.7 (C5Ha), 122.8 (C2), 116.4
(C1), 115.1 (dd, 2JCF = 21.1 Hz, 4JCF = 3.4 Hz C10HAr), 111.1
(t, JCF=15.9 Hz, C8). HRMS (FAB): m/z calcd for C34H15-
2
N4F4 555.1233, found 555.1230. Anal. Calcd for C34H14N4F4: C
73.65, H 2.54, N 10.10. Found: C 73.77, H 2.62, N 10.13.
2,9-Bis(2,4-difluoro-phenyl)-1,3,8,10-tetraazaperopyrene (6c).
Acid chloride: 2,4-difluorobenzoyl chloride. Yield: 410 mg (0.7
mmol; 74%) of 6c as an orange powder. 1H NMR (600.13 MHz,
TFA-d1) δ 10.40 (d, 4H, 3J=9.6 Hz, Hb), 9.16 (d, 4H, 3J=9.3 Hz,
2,9-Bis(2,4,6-trimethyl-phenyl)-1,3,8,10-tetraazaperopyrene
(2). Acid chloride: 2,4,6-trimethylbenzoyl chloride. Yield:
410 mg (0.7 mmol; 72%) of 2 as yellow powder. 1H NMR
(399.98 MHz, TFA-d1) δ 10.58 (d, 4H, J=9.5 Hz, Hb), 9.28
3
3
(d, 4H, J=9.3 Hz, Ha), 7.17 (s, 4H, HAr), 2.41 (s, 6H, para-
Ha), 8.87 (m, 2H, HAr), 7.33 (m, 2H, HAr), 7.20 (m, 2H, HAr). 13
C
CH3), 2.20 (s, 12H, ortho-CH3). 13C NMR (150.92 MHz, TFA-
d1, 295 K) δ 163.1 (C7), 153.6 (C6), 146.7 (C11), 141.2 (C4Hb),
139.3 (C9), 132.4 (C3), 131.6 (C10HAr), 128.8 (C8), 128.3
(C5Ha), 122.9 (C2), 116.4 (C1), 21.9 (para-CH3), 20.5 (ortho-
CH3). HRMS (MALDI): m/z calcd for C40H31N4 567.2549,
found 567.2543. Anal. Calcd for C40H30N4: C 84.78, H 5.34,
N 9.89. Found: C 84.60, H 5.70, N 9.60.
NMR (150.92 MHz, TFA-d1, 295 K) δ 170.6 (dd, 1JCF=264.4
Hz, 3JCF=14.5 Hz, C11), 164.8 (dd, 1JCF=255.4 Hz, 3JCF=13.5
=
Hz, C9), 155.1 (C7), 153.9 (C6), 140.3 (C4Hb), 137.4 (d, 3JCF
10.7 Hz, C13HAr), 132.1 (C3), 128.9 (C5Ha), 123.0 (C2), 116.6
(dd, 2JCF=22.7 Hz, 4JCF=2.7 Hz, C12HAr), 116.4 (dd, 2JCF
=
9.0 Hz, 4JCF = 3.4 Hz, C8), 116.2 (C1), 107.7 (t, 2JCF = 26.6 Hz,
C10HAr). HRMS (EI): m/z calcd for C34H14N4F4 554.1155,
616 J. Org. Chem. Vol. 76, No. 2, 2011

Martens et al.
JOCArticle
Data for 6b: C34H14F4N4, triclinic, P-1, a=6.9689(4), b=
found 554.1163. Anal. Calcd for C34H14N4F4: C 73.65, H 2.54,
N 10.10. Found: C 73.92, H 2.65, N 10.18.
˚
10.5536(7), c=16.8584(10) A, R=82.549(1), β = 86.086(1), γ=
=
3
73.071(1) °, V=1175.5(1) A , Z=2, μ=0.116 mm-1, F000
˚
2,9-Bis(2,4,5-trifluoro-phenyl)-1,3,8,10-tetraazaperopyrene
(6d). Acid chloride: 2,4,5-trifluorobenzoyl chloride. Yield: 432
mg (0.7 mmol; 73%) of 6d as an orange powder. 1H NMR
(600.13 MHz, TFA-d1) δ 10.57 (d, 4H, 3J=9.7 Hz, Hb), 9.33 (d,
564. T=100(2) K, θ range 2.0 to 31.0°. Index ranges h, k, l
(indep set): -10-10, -15-15, 0-24. Reflections measd:
29190, indep: 7427 [Rint = 0.0469], obsvd [I > 2σ(I)]: 4731.
Final R indices [Fo>4σ(Fo)]: R(F) = 0.0505, wR(F2)=0.1299,
GOF=1.046.
4H, 3J=9.3 Hz, Ha), 8.84 (m, 2H, HAr), 7.48 (m, 2H, HAr). 13
C
NMR (150.92 MHz, TFA-d1, 295 K) δ 160.0 (dd, 1JCF=252.6
Hz, 3JCF=10.5 Hz, C9), 158.9 (C7), 157.9 (m, C11), 153.9 (C6),
151.0 (m, C12), 140.5 (C4), 132.2 (C3), 128.9 (C5), 123.6 (C2),
122.9 (C13HAr), 116.5 (C8), 116.3 (C1), 110.3 (C10HAr). HRMS
(EI): m/z calcd for C34H12N 4F6 590.0966, found 590.0929.
Anal. Calcd for C34H12N4F6 (590.5): C 69.16 H 2.05 N 9.49.
Found: C 68.86 H 2.23 N 9.48.
Data for 7b: C34H8Br2F8N4, monoclinic, P21/c, a =
˚
3.7285(18), b=30.356(15), c=11.801(6) A, β=93.334(9)°, V=
3
1333(1) A , Z = 2, μ=3.133 mm-1, F000=764. T=100(2) K,
˚
θ range 1.9 to 26.4°. Index ranges h, k, l (indep set): -4-4, 0-37,
0-14. Reflections measd: 23953, indep: 2742 [Rint = 0.068],
obsvd [I > 2σ(I)]: 2387. Final R indices [Fo > 4σ(Fo)]: R(F)=
0.0895, wR(F2)=0.2146, GOF = 1.227.
2,9-Bis(3,5-difluoro-phenyl)-1,3,8,10-tetraazapero-pyrene
(6e). Acid chloride: 3,5-difluorobenzoyl chloride. Yield: 400 mg
(0.7 mmol; 72%) of 6e as an orange powder. 1H NMR (600.13
MHz, TFA-d1) δ 10.59 (d, 4H, 3J=9.7 Hz, Hb), 9.35 (d, 4H, 3J=
9.3 Hz, Ha), 8.37 (m, 4H, HAr), 7.42 (m, 2H, HAr). 13C NMR
Data for H26a2þ
7.985(4), b = 11.766(6), c = 16.176(8) A, R = 80.477(11), β =
79.834(9), γ=74.240(8) °, V=1428(1) A , Z=1, μ=0.205 mm
:
C50H16F34N4O16, triclinic, P-1, a =
˚
3
-1
˚
,
F000=778. T=100(2) K, θ range 2.1 to 26.4°. Index ranges h, k, l
(indep set): -9-9, -14-14, 0-20. Reflections measd: 42448,
indep: 7606 [Rint = 0.0747], obsvd [I > 2σ(I)]: 4540. Final R
indices [Fo > 4σ(Fo)]: R(F)=0.0806, wR(F2)=0.1548, GOF=
1.031. The crystal was an approximately 1:1 twin. Singles and
composites that include domain 1 were used for refinement.
Intensity data were collected at low temperature (Bruker AXS
Smart 1000 CCD diffractometer, Mo KR radiation, graphite
1
(150.92 MHz, TFA-d1, 295 K) δ 166.7 (dd, JCF =252.9 Hz,
3JCF=12.4 Hz, C10), 157.0 (t, 4JCF=3.3 Hz, C7), 154.3 (C6),
140.4 (C4), 135.0 (t, 3JCF=9.8 Hz, C8), 132.1 (C3), 128.9 (C5),
123.0 (C2), 116.5 (C1), 114.7 (dd, 2JCF=21.8 Hz, 4JCF=6.9 Hz,
2
C9HAr), 112.4 (t, JCF =25.3 Hz, C11HAr). HRMS (EI): m/z
calcd for C34H14N4F4 554.1155, found 554.1140. Anal. Calcd
for C34H14N4F4: C 73.65 H 2.54 N 10.10. Found: C 73.36 H 2.78
N 10.09.
˚
monochromator, λ = 0.71073 A) and corrected for Lorentz,
2,9-Bis(4-bromo-2-fluoro-phenyl)-1,3,8,10-tetraazaperopyr-
ene (7a). Acid chloride: 4-bromo-2-fluorobenzoyl chloride.
Yield: 300 mg (0.4 mmol; 44%) of 7a as an orange powder. 1H
NMR (600.13 MHz, TFA-d1) δ 10.50 (d, 4H, 3J=9.4 Hz, Hb),
polarization, and absorption effects (semiempirical).23,24 Struc-
ture solution: conventional direct methods (3, H26a2þ),25,26
direct methods with dual-space recycling (6a, 6b),27 heavy atom
method combined with structure expansion by direct methods.28
Refinement: full-matrix least-squares methods based on F2;25 all
non-hydrogen atoms anisotropic, hydrogen atoms taken
from Fourier maps or at calculated positions (refined fully or
riding). Distance and adp restraints were applied to disordered
groups.
3
9.26 (d, 4H, J=9.3 Hz, Ha), 8.77 (m, 2H, HAr), 7.85 (m, 2H,
H
Ar), 7.76 (m, 2H, HAr). 13C NMR (150.92 MHz, TFA-d1, 295
1
K) δ 164.0 (C7), 162.4 (C9), 155.1 (d, JCF=Hz, C9F), 153.8
(C6), 140.2 (C4), 135.7 (t, C10), 132.0 (C3), 131.3 (C12), 128.5
(C5), 123.1 (C2), 122.9 (C13HAr), 118.6 (C11Br), 116.2 (C1).
HRMS (EI): m/z calcd for C34H14N479Br2F2 673.9553, found
673.9557. Anal. Calcd for C34H14N4Br2F2: C 60.38 H 2.09
N 8.28. Found: C 60.74 H 2.32 N 8.37.
Acknowledgment. Financial support from the University
of Heidelberg, the Doctoral College “Molekulare Sonden” is
gratefully acknowledged. We also thank the German Ministry
of Education and Research (BMBF) for this work within the
project POLYTOS (FKZ: 13N10205) in the Research Net-
work “Forum Organic Electronics” for funding.
2,9-Bis(4-bromo-2,3,5,6-tetrafluoro-phenyl)-1,3,8,10-tetra-
azaperopyrene (7b). Acid chloride: 4-bromo-2,3,5,6-tetrafluoro-
benzoyl chloride. Yield: 365 mg (0.2 mmol; 47%) of 7b as an
orange powder. 1H NMR (600.13 MHz, TFA-d1) δ 10.67 (d, 4H,
3J=9.4 Hz, Hb), 9.38 (d, 4H, 3J=9.1 Hz, Ha). 13C NMR (150.92
MHz, TFA-d1, 295 K) δ 163.8 (C7), 154.0 (d, C6), 140.7 (C4),
132.4 (C3), 128.9 (C5), 122.7 (C2), 122.9 (C13HAr), 116.5 (C1).
Supporting Information Available: General experimental
methods; compound characterization by 1H and 13C NMR
spectra for all compounds; computational, cyclovoltammetric,
and X-ray crystallographic data. This material is available free
of charge via the Internet at http://pubs.acs.org.
HRMS (EI): m/z calcd for C34H8N479Br2F 781.8988, found
8
781.9051. Anal. Calcd for C34H N4Br2F8: C 52.08 H 1.03 N
8
7.14. Found: C 52.55 H 1.21 N 7.08.
X-ray Crystal Structure Determinations. Crystal Data. Data
for 3: C36H16F6N4, monoclinic, P21/n, a = 10.2372(9), b =
3
˚
˚
7.3908(7), c = 34.902(3) A, β = 93.567(2)°, V = 2635.6(4) A ,
Z = 4, μ = 0.123 mm-1, F000 = 1256. T = 100(2) K, θ range
2.0-25.0°. Index ranges h, k, l (indep set): -12-12, 0-8, 0-41.
Reflections measd: 42526, indep: 4651 [Rint = 0.0761], obsvd
[I >2σ(I)]: 3206. Final R indices [Fo>4σ(Fo)]: R(F)=0.0583,
wR(F2)=0.1379, GOF=1.056.
(23) Blessing, R. H. Acta Crystallogr. 1995, A51, 33–38.
(24) Sheldrick, G. M. SADABS; Bruker AXS: Madison, WI, 2004-2008.
Sheldrick, G. M. TWINABS; Bruker AXS: Madison, WI, 2004-2008.
€
(25) Sheldrick, G. M. SHELXS-97; University of Gottingen: Germany,
1997.
(26) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
(27) (a) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.;
Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Spagna, R.
J. Appl. Crystallogr. 2005, 38, 381–388. (b) Burla, M. C.; Caliandro, R.;
Camalli, M.; Carrozzini, B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.;
Polidori, G.; Spagna, R. SIR2004; CNR IC: Bari, Italy, 2004.
Data for 6a: C34H8F10N4, monoclinic, P21/n, a=11.602(4),
˚
b=3.7260(13), c = 28.062(10) A, β=96.652(6) °, V=1204.9(7)
3
A , Z = 2, μ = 0.164 mm-1, F000 = 660. T = 100(2) K, θ range
˚
€
(28) (a) Beurskens, P. T. In Sheldrick, G. M., Kruger, C., Goddard, R.,
2.0 to 27.5°. Index ranges h, k, l (indep set): -15-14, 0-4, 0-36.
Reflections measd: 23373, indep: 2754 [Rint=0.057], obsvd [I >
2σ(I)]: 1774. Final R indices [Fo>4σ(Fo)]: R(F)=0.0808, wR(F2)=
0.1366, GOF=1.017.
Eds.; Crystallographic Computing 3; Clarendon Press: Oxford, U.K., 1985; p
216. (b) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Smits, J. M. M.,
Garcia-Granda, S.; Gould, R. O. DIRDIF-2008; Radboud University
Nijmegen: The Netherlands, 2008.
J. Org. Chem. Vol. 76, No. 2, 2011 617