2,6-Diacylnaphthalene-1,8:4,5-bis(dicarboximides): Synthesis, reduction potentials, and core extension

Article abstract of DOI:10.1021/jo3006232

2,6-Diacyl derivatives of naphthalene-1,8:4,5-bis(dicarboximide)s have been synthesized via Stille coupling reactions of the corresponding 2,6-distannyl derivative with acyl halides. Reaction of these diketones with hydrazine gave phthalazino[6,7,8,1-lmna

Full text of DOI:10.1021/jo3006232

Article
pubs.acs.org/joc
2,6-Diacylnaphthalene-1,8:4,5-Bis(dicarboximides):
Synthesis, Reduction Potentials, and Core Extension
Lauren E. Polander,† Laxman Pandey,† Alexander Romanov,‡ Alexandr Fonari,‡ Stephen Barlow,†
Brian M. Seifried,† Tatiana V. Timofeeva,‡ Jean-Luc Bredas,† and Seth R. Marder*,†
́
†School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics, Georgia Institute of Technology,
Atlanta, Georgia 30332-0400, United States
‡Department of Chemistry, New Mexico Highlands University, Las Vegas, New Mexico 87701, United States
S
* Supporting Information
ABSTRACT: 2,6-Diacyl derivatives of naphthalene-1,8:4,5-bis(dicarboximide)s have been synthesized via Stille coupling
reactions of the corresponding 2,6-distannyl derivative with acyl halides. Reaction of these diketones with hydrazine gave
phthalazino[6,7,8,1-lmna]pyridazino[5,4,3-gh][3,8]phenanthroline-5,11(4H,10H)-dione fused-ring derivatives. The products
were characterized by UV−vis absorption spectroscopy and electrochemistry, modeled using density functional theory
calculations, and, in some cases, studied and compared using single-crystal X-ray diffraction.
have been obtained with reduction potentials ranging from
INTRODUCTION
■
−0.40 to −1.49 V versus FeCp2 (Cp = η5-cyclopentadienyl)
+/0
Rylene diimide derivatives, particularly napthalene and perylene
diimides (NDIs and PDIs, respectively), are extensively studied as
building blocks in optoelectronic devices, such as field-effect
transistors (OFETs),1,2 photovoltaic cells (OPVs),3−5 dye lasers,6
optical switches,7 and photodetectors,8 as electron acceptors for
studying photoinduced energy- and electron-transfer processes9−11
and as ligands in nucleic acid studies of telomerase inhibition
in metastatic cancer cells.12,13 Interest in rylene diimides for these
applications stems from their thermal, chemical, and photo-
chemical stability, large electron affinities (EAs), large charge-
carrier mobility values, and the ability to tune their electronic
properties through well-established organic chemistry.1,14
Recently, many groups have focused on tuning the electronic
properties and solid-state interactions of these rylene cores to
achieve improved charge-carrier stability under ambient
conditions, energy-level alignment with suitable electrodes, and
specific solid-state molecular packing demonstrating stacking
between aromatic systems.15−20 The electronic properties of
NDI, in particular, have been successfully tuned via core substitu-
tion, which typically has a much more significant effect on the
redox potentials than variation of the N,N′-substituents (a
consequence of the presence of nodes on the N atoms in both
HOMO and LUMO wave functions), and via extension of the
aromatic core system. Core-functionalized NDIs have been
synthesized from brominated NDIs, either through nucleophilic
substitutions to afford amino, thiol, or alkoxy derivatives,21,22 or
through Pd-catalyzed coupling reactions to yield cyano,23,24
phenyl,24,25 alkynyl,24 and thienyl25−27 products. Derivatives
for a 2,6-dicyano-NDI23 and a 2,6-dipyrrolidino-NDI,24
respectively. So-called core-expanded NDIs, in which additional
rings are fused to a NDI core, have been reported: Hu et al. used
the reaction of tetrabromo-NDI with dithiines and dithiolyli-
denes, with the first reduction potentials of these core-expanded
28
+/0
NDIs ranging from −0.52 to −0.67 V versus FeCp2
.
However, core-metalated NDIs that could be used to broaden
the scope of NDI chemistry and to yield a wide variety of new
NDI products were, until the recent synthesis of 2,6-distannyl-
NDIs,29 unknown.
Mono- or diketones obtained by acylation of the NDI core may
be of interest due to the influence of the electron-withdrawing acyl
moieties on the reduction potential; moreover, use of different
alkanoyl or aroyl groups may allow this reduction potential to be
tuned. The electron-poor nature of NDIs, however, means direct
acylation of the core by Friedel−Crafts methods is impractical. On
the other hand, our recent synthesis of 2,6-distannyl-NDIs29 offer
the possibility of using the well-known palladium-catalyzed Stille
coupling of aryl-stannanes with acyl halides.30 Here, we describe
the use of a 2,6-distannyl NDI derivative (1)29 to synthesize
hitherto unreported 2,6-diacyl-NDIs (2a−e), their reaction with
hydrazine to yield planar fused-ring 1,7-dialkyl (3a) or 1,7-diaryl
(3b) phthalazino[6,7,8,1-lmna]pyridazino[5,4,3-gh][3,8]-
phenanthroline-5,11(4H,10H)-diones (PPPs), the optical and
Received: March 26, 2012
Published: May 23, 2012
© 2012 American Chemical Society
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electronic properties of these new classes of compounds (2a−e, 3a
and 3b, and crystal structures of representative examples (2b, 3a
and 3b).
R = C5H11 replaced by ethyl groups to reduce computational
cost. Compounds 2 are characterized by a planar core with a large
torsion angle between the plane of the NDI core and the planes
containing the ketone functional groups (on average 71° and 76°
for alkyl and aryl ketone, respectively); this is mainly due to steric
interactions between the CO and alkyl/aryl groups of the
ketone functionalities with the CO of the NDI imides. As a
result, any influence of the acyl substituents on the electronic
properties of the core is primarily inductive in nature. Compounds
3a and 3b, on the other hand, are characterized by a planar fused
core. The phenyl group of 3b is (on average) estimated to be twisted
some 40° out-of-plane with respect to the central core, consistent
with the effects of steric interactions between hydrogen atoms in its
ortho-position with the hydrogen atoms on the core.
The B3LYP/6-31G** HOMO and LUMO wave functions
are illustrated for NDI, 2a−e, PPP, 3a and 3b in Figure 1. The
HOMO wave functions of 2c and 2d are strongly localized on
the C(O)R segments, while those for 2a, 2b, and 2e, although
still significantly keto-based, are also characterized by partial
delocalization onto the core of the NDI. The LUMO wave
functions, on the other hand, are strongly localized on the
core for all derivatives. The LUMO energy of 2a is stabilized
relative to that of an isolated NDI, a consequence of the inductive
withdrawing effect of the acyl substituents. The fluoro- and
trifluoromethyl-substituted benzoyl species 2c−e have still lower
LUMO energies, that of 2d being ca. 0.45 eV lower than that of
the parent NDI (Table S1, Supporting Information).
RESULTS AND DISCUSSION
■
Synthesis. Commercially available alkanoyl and aroyl R
groups were chosen to investigate the possibility of obtaining
diacyl NDIs by Stille coupling of distannyl NDIs and acyl halides.
As noted above, acylation is anticipated to result in anodically
shifted reduction potentials; in order to gauge the extent to which
the substituents of the aroyl groups may be used to lead to even
more facile reduction, aroyl groups with varied degrees of
fluorination were used. N,N′-Di(n-hexyl)-2,6-bis(tri(n-butyl)-
stannyl)naphthalene-1,8:4,5-bis(dicarboximide),29 1, was con-
verted using Pd(PPh3)2Cl2, CuI, and the appropriate acylhalide,
XCOR (X = Cl, Br), under Stille conditions to N,N′-bis(n-hexyl)-
2,6-diacylnaphthalene-1,8:4,5-bis(dicarboximide) derivatives,
2a−e, in 26−32% yield (Scheme 1).
Scheme 1. Preparation of 2a-e, 3a and 3b
Hydrazine hydrate has been used extensively in the literature
in reactions with 1,2-diacyl-ethylene derivatives to form
pyridazine derivatives;31,32 this chemistry was applied to the
synthesis of new fused-ring structures. 1,7-Di(n-pentyl)-4,10-
di(n-hexyl)phthalazino[6,7,8,1-lmna]pyridazino[5,4,3-gh][3,8]-
phenanthroline-5,11(4H,10H)-dione, 3a, and 1,7-di(n-phenyl)-
4,10-di(n-hexyl)phthalazino[6,7,8,1-lmna]pyridazino[5,4,3-gh]-
[3,8]phenanthroline-5,11(4H,10H)-dione, 3b, were synthesized
from 2a and 2b, respectively, via condensation with hydrazine
hydrate in ethanol at reflux (Scheme 1) and were isolated in
35−37% yield.33 This condensation reaction was not performed
on compounds 2c−e because of poor solubility associated
with these compounds under the reaction conditions. The new
compounds were characterized by 1H, 19F, and, with the excep-
tion of the very poorly soluble 2d and 2e, 13C{1H} NMR spectro-
scopy, high-resolution mass spectrometry, and elemental analysis.
DFT Molecular Geometry and Frontier Orbitals. The
neutral ground-state structures were obtained at the DFT
(B3LYP/6-31G**) level for NDI, 2a−e, PPP, 3a and 3b with all
N,N′-alkyl groups replaced by methyl groups and, for 2a and 3a,
The HOMOs of the PPP systems, 3a and 3b, in contrast to
those of the acyl derivatives, are π orbitals delocalized over the
fused-ring system, with that of 3b being more extensive than that
of 3a or an unsubstituted PPP because of additional delocaliza-
tion onto the phenyl substituents. The LUMO wave functions for
3a and 3b are similar to one another and to that of the unsubstituted
PPP. The HOMO and LUMO energies are destabilized relative to
those of an NDI without core substitution by ca. 0.5−1.0 and 0.3 eV,
respectively (Figure 1, Table S1, Supporting Information), because
of a combination of the reduced electronegativity of nitrogen versus
oxygen and of the antibonding interaction between the naphthalene
segment and the CN portions of the phenazine rings that are
derived from the acyl groups.
Optical Properties and Electrochemistry. Electronic
absorption spectra of N,N′-bis(n-hexyl) naphthalene diimide
(NDI6), 2a−e, 3a and 3b were recorded in dilute dichloro-
methane solution (ca. 10−5 M). Representative spectra are shown
in Figure 2; the corresponding absorption maxima and molar
absorptivities are summarized in Table 1. The spectra of 2c−e are
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Figure 1. Pictorial representations of the HOMO (H) and LUMO (L) wave functions for N,N′-dimethyl derivatives of NDI, 2a (R = C2H5), 2b−e, PPP,
3a (R = C2H5), and 3b, as determined at the B3LYP/6-31G** level of theory (isovalue surface 0.03 a.u.).
Table 1. Absorption Maxima (nm) and Absorptivities
(104 M−1 cm−1) for the Strong UV−vis Absorptions of 2 and 3
in Dichloromethane along with Thin-Film Absorption
Maxima (nm), Electrochemical Potentials
a
(V vs FeCp2+/0) and DFT Estimates of Electron Affinity and
b
Reorganization Energy (eV)
λmax
c
d
0/−
−/2−
cmpd
soln
film
εmax
E1/2
E1/2
EAadi(g)
λe
e
NDI6
2a
380
380
380
381
381
381
423
433
393
401
2.76
1.79
−1.13
−0.90
−0.87
−0.84
−0.80
−0.78
−1.40
−1.30
−1.70
−1.34
−1.32
−1.28
−1.26
−1.24
−1.91
−1.73
−2.03
−2.45
−2.40
−2.50
−2.69
−2.74
−1.83
0.336
0.432
0.452
0.464
0.470
0.477
0.271
0.276
2b
386
f
1.88
f
2c
f
f
f
f
2d
2e
3a
444
443
1.52
1.30
Figure 2. Representative UV−vis spectra of NDI6, 2a, 2b, 3a and 3b in
dilute dichloromethane solutions.
3b
−1.91
b
a
n
Cyclic voltammetry in CH2Cl2/0.1 M Bu4NPF6. SCF values for
c
isolated molecules. Adiabatic EA = SCF energy difference between
the relaxed ground-state anion and the ground-state neutral species
(obtained for structures in which the alkyl groups are all replaced by
essentially identical to that of 2a and 2b and are shown in Figure
S1, Supporting Information. The absorption spectra of 2a−e
exhibit prominent vibronically structured absorption bands with
maxima at 380−381 nm, similar to that of the corresponding
NDI derivative (NDI6, 380 nm). Fluorination of the phenyl
moiety does not significantly affect the spectra, which is
consistent with all the acyl groups acting primarily as inductively
electron-withdrawing substituents.
d
methyl groups at the B3LYP/6-31G** level). Internal reorganization
−
−
energies for MA + MB = MA + MB obtained as sum of the SCF
energy difference between anion at the neutral geometry and at anion
geometry and that between the neutral species at anion geometry and
e
f
at neutral geometry. N,N′-bis(n-hexyl) naphthalene diimide. Not
measured because of solubility limitations.
The absorption spectra of 3a and 3b exhibit prominent
absorption bands with maxima at 423 and 433 nm, respectively.
The absorption maxima of 3a and 3b are bathochromically
shifted by ca. 50−80 nm relative to that of NDI6 and the diacyl-
NDI analogues 2a−e.
To gain insight into the origin of the spectroscopic properties
observed in solution, the vertical S0 → Sn excitation energies were
calculated for the isolated molecules at the time-dependent
density functional theory (TD-DFT) level with the B3LYP
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functional and the 6-31G** basis set (Table S2, Figures S2 and
S3, Supporting Information). The strong low-energy transitions
calculated for 2a and 2b represent a superposition of S0 → S4 and
S0 → S5 in 2a, and S0 → S9 in 2b. These transitions are
predominantly HOMO−2 → LUMO and HOMO−6 → LUMO
contributions for 2a and 2b, respectively; in fact, both the
HOMO−2 of 2a and HOMO−6 of 2b closely resemble the NDI
HOMO (Figure 3). The transitions for 3a and 3b correspond to
B3LYP/6-31G** level (Table 1). The calculated λe values for all
five diacyl-NDI derivatives are on the order of 450 meV, which is
significantly larger (by 100−140 meV) than that estimated for
NDI6. The calculated λe values for 3a and 3b are smaller by ca.
60 meV than those estimated for NDI6 and are much smaller
than the values calculated for the diacyl-NDI derivatives (by ca.
200 meV). For the sake of comparison, λe values in a series of
30 PDI derivatives have been calculated to fall in the range
250−350 meV.36
Crystal Structure and Electronic Coupling. Crystals of
2b, 3a, and 3b suitable for single-crystal X-ray structure
determination were obtained by slow evaporation of a 1:1
solution of dichloromethane and ethyl acetate, slow evaporation
of a dichloromethane solution, and liquid−liquid diffusion
of a 1,1,2,2-tetrachloroethane−pentanol mixture, respectively
(Figure 4).37 Compound 3b crystallized with the incorporation
Figure 3. Pictorial representations of the HOMO (−7.04 eV),
HOMO−2 (−7.30 eV), and HOMO−6 (−7.27 eV) wave functions
for N,N′-dimethyl derivatives of NDI, 2a (R = C2H5), and 2b,
respectively, as determined at the B3LYP/6-31G** level of theory
(isovalue 0.03).
the S0 → S3 and S0 → S2 transitions, respectively, and are
predominantly HOMO → LUMO in nature. Accordingly, the
bathochromic shifts of the strong transitions of 3a and 3b relative
to NDI can be attributed to the reduced HOMO−LUMO
separation calculated, where both orbitals are destabilized by
extension of the NDI core, but with the HOMO being more
strongly affected (Table S1, Supporting Information). The
additional bathochromic shift seen in 3b relative to 3a can be
attributed to the reduced HOMO−LUMO separation seen for
that compound, which arises from the extension of the HOMO
onto the phenyl substituents, as described above.
Cyclic voltammetry (CV) was used to measure the reduction
potentials of NDI6, 2a−e, 3a and 3b in CH2Cl2/0.1 M nBu4NPF6
(Table 1, Figures S4 and S5, Supporting Information). Two
sequential reversible one-electron reduction processes were
observed for each molecule. The half-wave reduction potentials
corresponding to reduction to the radical anions (E1/20/−) of 2b−
e are cathodically shifted with increasing fluorine substitution, as
expected on the basis of the Hammett parameters34 of the
appropriate fluoro-phenyl substituents and consistent with
the trend observed in the DFT calculated adiabatic EA values
(Table 1). Although more readily reduced NDIs have been
reported (notably, a 2,6-dicyano-NDI derivative exhibits a first
+/0
reduction potential of −0.40 V versus FeCp2 in dichloro-
methane23), these ketones are significantly more readily reduced
than unsubstituted NDIs, and the potential of 2e at least falls
in the range where stable electron-transport properties might
be expected in ambient atmosphere.35 However, the poor
π-stacking, low calculated intermolecular couplings, and
moderate calculated reorganization energies (vide infra) suggest
that electron mobility would be likely to be low.
Both of the hydrazine-fused products, 3a and 3b are
significantly more difficult to reduce than NDI6, which is
consistent with the trends in DFT-calculated LUMO energies
and EAs (Tables 1 and S1, Supporting Information). The alkyl-
substituted derivative 3a is ca. 0.10 V less readily reduced than the
aryl-substituted derivative 3b, also consistent with calculations and
with the relative inductive properties of alkyl and phenyl groups.34
The intramolecular reorganization energies for a self-exchange
electron-transfer reaction between the neutral molecules and the
corresponding radical anions, λe, were also calculated at the
Figure 4. Molecular structures of 2b (top), 3a (middle), and 3b
(bottom) determined by X-ray crystallography (50% thermal ellipsoids).
of 1,1,2,2-tetrachloroethane molecules into the lattice; these
solvent molecules were found to be severely disordered (details
in the Experimental Section). In each case, the conformations of
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the molecules (shown in Figure 4) are similar to those found in
the calculations on isolated molecules (Figure 1). The packing in
the structures are described using pitch and roll angles and
distances as described by Curtis et al.38 (Figure S6, Supporting
Information), where P and R are the pitch and roll angles
corresponding to the molecular slipping along the long (zL) and
short (zS) axis of the molecule, respectively; d is the π−π distance
between two stacked molecular planes; dP and dR are the slip
distances along the long and short axis, respectively; and dtot is
approximation, this would provide for a conduction bandwidth
along the stacking direction on the order of 350 meV, which is similar
to the valence bandwidth in rubrene.41 These values are comparable
to the effective electronic couplings calculated earlier on the basis
of the single-crystal structure of N,N′-cyclohexyl-NDI by similar
methods (91 and 19 meV for a- and b-axis, respectively).42
Compound 2b also adopts a slipped π-stack structure with
much larger π−π and total slip distances when compared to
NDI6 (Table 2, Figures 5 and S8, Supporting Information). The
large distances observed in 2b are attributed to the aryl-ketone
units, which are approximately perpendicular to the plane of the
NDI core (the angle between planes formed by the carbon atoms
of the NDI and C(O)C of the ketone moiety is 86.5°), consistent
with the large torsion angles predicted by DFT. For 2b, the
electronic coupling along the π−π stacking direction (b-axis) is
determined to be low for electrons (20 meV) compared to that
for NDI6, while along the a- and c-axis they are negligible.
Crystals of 3a and 3b (C2H2Cl4 solvate) adopt a slipped
π-stack structure with parallel neighboring molecular stacks
similar to that observed for NDI6 (Figures 5, S9 and S10,
Supporting Information). Although the relative pitch and roll
angles and distances are different, the π−π and total slip distances
for 3a and 3b are very similar to those measured in the crystal
structure of NDI6 (Table 2) and allow for a significant amount of
spatial overlap between the cores (Figure 5). However, the core
wave function overlap in 3a leads to much smaller electronic
couplings than for the solvate of 3b. Unlike the aroyl groups of
2b, the aryl moiety in 3b does not impede π−π interactions; the
torsion angle between this group and the plane of the core is
60.7°, which is consistent with a decrease in the Ph−core torsion
angle calculated for 3b relative to the acyl−core torsion angle
calculated for 2b using DFT. Thus, these calculations suggest
that, given that 3b displays a significant electronic coupling along
the stacking direction (leading to an estimated conduction
bandwidth of ∼250 meV) and a relatively low reorganization
energy, the electron mobility in this compound could be
substantial along the a-axis.
2
2
defined as the total slip distance (dtot = (dP + dR )1/2). These
values are summarized for each crystal in Table 2. On the basis
a
a
Table 2. Pitch and Roll Angles (deg) and Distances (Å)
b
along with Electronic Couplings (B3LYP/6-31G**)
between Nearest Pairs (meV) for NDI6, 2b, 3a, and 3b
cmpd
P
R
d
dP
dR
dtot
ta
tb
tc
NDI6
2b
19.4
13.0
45.4
45.7
45.6
47.6
11.3
18.1
3.3
3.8
3.3
3.3
1.2
3.4
3.6
4.3
3.4
3.6
85
0
31
20
−
0
0
0.88
3.3
4.2
3a
0.67
1.1
7
−
0
c
3b
3.4
63
−
a
As defined in the text and respresented by Figure S8, Supporting
b
Information. Electronic couplings calculated along the a- (ta), b- (tb),
and c- (tc) axes, respectively, between LUMO levels of pairs of adjacent
molecules with intermolecular distances less than 7 Å along the
c
specified axis. C2H2Cl4 solvate.
of the crystal structures of NDI6,39 2b, 3a, and 3b, the inter-
molecular effective electronic couplings were evaluated using DFT
(Table 2, B3LYP/6-31G**, using the fragment orbital approach40).
The X-ray single-crystal structure of NDI6 reported by Shukla
et al. was used for comparison purposes.39 The molecular
packing in the NDI6 crystal is characterized as a slipped π-stack
with close π−π distances (d = 3.3 Å) and a total slip distance,
dtot, of 3.6 Å resulting in substantial overlap of the NDI cores
(Figure 5). The stacks are arranged parallel to one another
CONCLUSION
■
2,6-Diacyl-NDIs have been synthesized for the first time from the
reaction of a 2,6-distannyl NDI and acyl halides, and two
examples have been converted to the first examples of the PPP
fused-ring system. The new compounds have been characterized
by quantum-chemical calculations, UV−vis spectroscopy, cyclic
voltammetry, and, in some cases, X-ray crystallography. The
redox potentials of these materials can be easily tuned through
varying core substitution, with the use of electron-poor acyl-
halide coupling partners leading to particularly readily reduced
examples. This general synthetic method can potentially be
applied in a variety of NDI systems to develop new diacyl-NDI
and fused-ring NDI derivatives.
EXPERIMENTAL SECTION
■
General Experimental Methods. Starting materials were reagent
grade and were used without further purification unless otherwise
indicated. Anhydrous toluene was obtained by passing through columns
of activated alumina. All Stille coupling reactions were performed using
oven-dried glassware under nitrogen atmosphere. Chromatographic
separations were performed using standard flash column chromatog-
raphy methods. Electrochemical measurements were carried out
under nitrogen in dry deoxygenated 0.1 M tetra-n-butylammonium
hexafluorophosphate in dichloromethane using a conventional three-
electrode cell with a glassy carbon working electrode, platinum wire
counter electrode, and a Ag wire coated with AgCl as pseudoreference
Figure 5. Crystal structure of NDI6 (top left), 2b (top right, R =
C(O)C5H11), 3a (bottom left, R = C5H11), and 3b (bottom right,
C2H2Cl4 solvate) showing the overlap of the cores. N,N′-alkyl groups
have been removed for clarity.
(Figure S7, Supporting Information). The LUMO−LUMO
electronic couplings (t) for NDI6 were determined to be high for
electrons along the a-axis (π−π stacking direction, 85 meV) and
relatively low along the b-axis (31 meV); in a tight-binding
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+/0
electrode. Potentials were referenced to FeCp2 by using ferrocene
as an internal reference. Cyclic voltammagrams were recorded at a
scan rate of 50 mV s−1. UV−vis spectra were recorded in 1 cm cells in
dichloromethane solvents. Melting points were measured using
differential scanning calorimetry (DSC) at a scanning rate of 5 °C min−1.
X-ray Diffraction. Crystals of 2b, 3a, and 3b suitable for single-
crystal X-ray structure determination were obtained by slow evaporation
of a 1:1 solution of dichloromethane and ethyl acetate, slow evaporation
of a dichloromethane solution, and liquid−liquid diffusion of a 1,1,2,2-
tetrachloroethane−pentanol mixture, respectively.
flash chromatography (silica gel, 0−2% methanol in dichloromethane).
The product was recrystallized twice from ethyl acetate and collected
1
as a white solid (0.376 g, 0.596 mmol, 30%, mp 327 °C). H NMR
(400 MHz, CDCl3) δ 8.63 (s, 2H), 7.79 (d, J = 7.3 Hz, 4H), 7.62 (t, J =
7.4 Hz, 2H), 7.47 (t, J = 7.8 Hz, 4H), 4.02 (t, J = 7.1 Hz, 4H), 1.59 (m,
4H), 1.33−1.15 (m, 12H), 0.81 (t, J = 6.9 Hz, 6H). 13C{1H} NMR
(100 MHz, CDCl3) δ 194.8, 161.8, 161.7, 145.0, 135.5, 134.1, 130.6,
129.2, 128.9, 126.8, 126.6, 123.9, 41.2, 31.3, 27.8, 26.5, 22.4, 13.9. HRMS
(EI) m/z calcd for C40H39N2O6 (M+), 642.2730; found, 642.2741. Anal.
Calcd. for C40H38N2O6: C, 74.75; H, 5.96; N, 4.36. Found: C, 74.49; H,
5.85; N 4.29. IR (KBr) ν 3063 (w), 2962, 2926, 2853, 1708 (s), 1679
(s, br), 1583, 1450, 1347, 1315, 1225, 1196, 1130, 861, 793, 686 cm−1.
N,N′-Di(n-hexyl)-2,6-bis(4-fluorobenzoyl)naphthalene-
1,8:4,5-bis(dicarboximide), 2c. This compound was synthesized
according to the general procedure using 1 (0.490 mmol), hexanoyl
chloride (1.04 mmol), CuI (0.020 mmol), Pd(PPh3)2Cl2 (0.010 mmol),
and toluene (5 mL). After cooling, the reaction mixture was filtered
through a plug of Celite eluting with toluene, and the filtrate was
concentrated via rotary evaporation. The crude product was purified by
flash chromatography (silica gel, 0−1% ethyl acetate in chloroform).
The product was recrystallized twice from ethyl acetate and collected
The X-ray diffraction data were collected at 100 K using graphite
monochromated Mo Kα radiation (λ = 0.71073 Å). Absorption
corrections were applied semiempirically using APEX2 program.43 The
structures were solved by direct methods and refined by full matrix least-
squares on F2 in the anisotropic approximation for non-hydrogen atoms.
The phenyl ring of molecule 3b was found to be disordered over two
positions with the occupancies 0.51/0.49. For the final refinement,
the contribution of a severely disordered 1,1,2,2-tetrachloroethane
molecule of crystallization was removed from the diffraction data with
PLATON44/SQUEEZE.45 All hydrogen atom positions were refined in
isotropic approximation in “riding” model with the Uiso(H) parameters
equal to 1.2 Ueq(Ci), for methyl groups equal to 1.5 Ueq(Cii), where
U(Ci) and U(Cii) are respectively the equivalent thermal parameters
of the carbon atoms to which the corresponding H atoms are bonded.
Data reduction and further calculations were performed by using the
SHELXS-9746 and SHELXL-9747 (2b and 3a) or SHELXTL48 (3b)
program packages. Selected refinement data and structure parameters
are shown in Table S3, Supporting Information.
Computational Methodology. Calculations for the isolated
(neutral, radical-cation, and radical-anion) molecules in their electronic
ground state were carried out at the density functional theory (DFT)
level, using B3LYP hybrid,49−51 a global hybrid functional, in
conjunction with a 6-31G**52−54 basis set. All N,N′-alkyl groups were
replaced with methyl groups, and all alkyl R groups were replaced with
ethyl groups to reduce the computational cost. The optimized
geometries are true minima with no imaginary harmonic vibrational
frequencies. All calculations were performed using the Gaussian (03
revision E.0155 and 09 revision A.0256) suite of programs.
1
as a white solid (0.106 g, 0.156 mmol, 32%, mp 306 °C). H NMR
(400 MHz, CDCl3) δ 8.61 (s, 2H), 7.81 (dd, JHF = 5.2, JHH = 8.8 Hz,
4H), 7.14 (apparent t, JHF ∼ JHH ∼ 8.6 Hz, 4H), 4.02 (t, J = 7.3 Hz, 4H),
1.67−1.53 (m, 4H), 1.35−1.13 (m, 12H), 0.82 (t, J = 6.9 Hz, 6H).
13C{1H} NMR (100 MHz, CDCl3) δ 193.2, 166.3 (d, JCF = 255 Hz),
161.7, 161.6, 144.7, 132.1, 131.9, 131.8, 130.5, 126.8 (d, JCF = 20 Hz),
123.5, 116.2 (d, JCF = 22 Hz), 41.2, 31.3, 27.8, 26.5, 22.4, 13.9. 19F NMR
(375 MHz, CDCl3, referenced to (trifluoromethyl)benzene in CDCl3) δ
−104.15 (s). HRMS (EI) m/z [M]+ calcd for C40H36F2N2O6 678.2541;
found, 678.2557. Anal. Calcd. for C40H36F2N2O6: C, 70.78; H, 5.35; N,
4.13. Found: C,70.55; H, 5.42; N 4.09. IR (KBr) ν 3069 (w), 2965, 2929,
2860, 1708 (s), 1657 (s, br), 1598, 1507, 1450, 1317, 1225, 1154, 849,
618, 509 cm−1.
N,N′-Di(n-hexyl)-2,6-bis(4-(trifluoromethyl)benzoyl)-
naphthalene-1,8:4,5-bis(dicarboximide), 2d. This compound was
synthesized according to the general procedure using 1 (0.490 mmol),
hexanoyl chloride (1.04 mmol), CuI (0.020 mmol), Pd(PPh3)2Cl2
(0.010 mmol), and toluene (5 mL). After cooling, the reaction mixture
was diluted with 1,1,2,2-tetrachloroethane and filtered through a plug
of silica gel eluting with 1,1,2,2-tetrachloroethane and ethyl acetate.
The filtrate was diluted with hexanes and placed at −20 °C for 1 h to
precipitate a white solid. The crude product was recrystallized from
dichloromethane and collected as a white solid (0.112 mg, 0.144 mmol,
General Procedure for Preparation of Compounds 2a−e. A
solution of 129 (1 equiv), acylchloride (2−3 equiv), and copper(I)
iodide (10 mol %) in dry toluene (0.05 M wrt 1) was deoxygenated
with nitrogen for 5 min. Dichloro-bis(triphenylphosphine)palladium
(5 mol %) was added, and the reaction mixture was heated to 100 °C for
1.5−4 h.
1
29%, mp 347 °C). H NMR (400 MHz, C2D2Cl4) δ 8.64 (s, 2H),
N,N′-Di(n-hexyl)-2,6-dihexanoylnaphthalene-1,8:4,5-bis-
(dicarboximide), 2a. This compound was synthesized according
to the general procedure using 1 (1.98 mmol), hexanoyl chloride
(5.93 mmol), CuI (0.198 mmol), Pd(PPh3)2Cl2 (0.099 mmol), and
toluene (40 mL). After cooling, the reaction mixture was filtered
through a plug of Celite eluting with toluene, and the filtrate was
concentrated via rotary evaporation. The crude product was purified by
flash chromatography (silica gel, 0−2% methanol in dichloromethane).
The product was recrystallized twice from ethyl acetate and collected as
a white solid (0.333 g, 0.518 mmol, 26%, mp 262 °C). 1H NMR (400
MHz, CDCl3) δ 8.46 (s, 2H), 4.11 (t, J = 7.6 Hz, 4H), 2.86 (t, J = 7.4 Hz,
4H), 1.85 (quint., J = 7.4 Hz, 4H), 1.66 (quint., J = 7.5 Hz, 4H), 1.50−
1.20 (m, 20H), 0.92 (t, J = 7.0 Hz, 6H), 0.87 (t, J = 6.9 Hz, 6H). 13C{1H}
NMR (100 MHz, CDCl3) δ 205.0, 162.2, 161.8, 146.9, 129.4, 126.9,
126.4, 122.2, 43.2, 41.2, 31.4, 31.3, 27.9, 26.6, 23.4, 22.5, 22.4, 14.0, 13.9.
HRMS (EI) m/z calcd for C38H51N2O6 (M+), 630.3669; found,
630.3674. Anal. Calcd. for C38H50N2O6: C, 72.35; H, 7.99; N, 4.44.
Found: C, 72.65; H, 7.94; N 4.47. IR (KBr) ν 3058 (w), 2958, 2930,
2872, 1697 (s), 1652 (s), 1453, 1381, 1324, 1182, 1149, 798, 768 cm−1.
N,N′-Di(n-hexyl)-2,6-dibenzoylnaphthalene-1,8:4,5-bis-
(dicarboximide), 2b. This compound was synthesized according
to the general procedure using 1 (1.98 mmol), hexanoyl chloride
(5.93 mmol), CuI (0.198 mmol), Pd(PPh3)2Cl2 (0.099 mmol), and
toluene (40 mL). After cooling, the reaction mixture was filtered
through a plug of Celite eluting with toluene, and the filtrate was
concentrated via rotary evaporation. The crude product was purified by
7.92 (d, J = 8.0 Hz, 4H), 7.76 (d, J = 8.3 Hz, 4H), 4.03 (t, J = 7.3 Hz,
4H), 1.70−1.50 (m, 4H + H2O overlap), 1.35−1.15 (m, 12H), 0.83
(t, J = 6.6 Hz, 6H). 19F NMR (375 MHz, C2D2Cl4, referenced to
(trifluoromethyl)benzene in CDCl3) δ −62.94 (s). HRMS (EI) m/z
calcd for C42H36F6N2O6 (M+), 778.2478; found, 778.2477. Anal. Calcd.
for C42H36F6N2O6: C, 64.78; H, 4.66; N, 3.60. Found: C, 64.58; H, 4.54;
N 3.59. IR (KBr) ν 3067 (w), 2962, 2932, 2859, 1710 (s), 1685 (s, br),
1659, 1452, 1328, 1225, 1132, 1068, 855 cm−1. A 13C NMR spectrum
was not obtained because of the poor solubility of 2d.
N,N′-Di(n-hexyl)-2,6-bis(3,4,5-trifluorobenzoyl)naphthalene-
1,8:4,5-bis(dicarboximide), 2e. This compound was synthesized
according to the general procedure using 1 (0.490 mmol), hexanoyl
chloride (1.04 mmol), CuI (0.020 mmol), Pd(PPh3)2Cl2 (0.010 mmol),
and toluene (5 mL). After cooling, the reaction mixture was diluted
with 1,1,2,2-tetrachloroethane and filtered through a plug of Celite. The
solvent was removed under reduced pressure. The crude product
was recrystallized from chlorobenzene and collected as a white solid
1
(0.034 mg, 0.045 mmol, 9.2%, mp 350 °C). H NMR (400 MHz,
C2D2Cl4) δ 8.62 (s, 2H), 7.45 (m, 4H), 4.04 (m, 4H), 1.70−1.50 (m,
4H + H2O overlap), 1.40−1.20 (m, 12H), 0.85 (m, 6H). 19F NMR (375
MHz, C2D2Cl4, referenced to (trifluoromethyl)benzene in CDCl3)
δ −68.05 (d, J = 18.8 Hz, 2F), −87.07 (m, 4F). HRMS (EI) m/z calcd
for C40H32F6N2O6 (M+), 750.2165; found, 750.2150. Anal. Calcd. for
C40H32F6N2O6: C, 64.00; H, 4.30; N, 3.73. Found: C, 63.72; H, 4.34;
N 3.79. IR (KBr) ν 3072, 2961, 2926, 2859, 1715 (s), 1668 (s, br), 1529,
5549
dx.doi.org/10.1021/jo3006232 | J. Org. Chem. 2012, 77, 5544−5551

The Journal of Organic Chemistry
Article
1446, 1355, 1314, 1193, 1043, 736 cm−1. A 13C NMR spectrum was not
obtained because of the poor solubility of 2e.
Risko for helpful discussion, and Yadong Zhang for DSC
measurements.
1,7-Di(n-pentyl)-4,10-di(n-hexyl)phthalazino[6,7,8,1-lmna]-
pyridazino[5,4,3-gh][3,8]phenanthroline-5,11(4H,10H)-dione,
3a. To a solution of 2a (0.200 g, 0.317 mmol) in ethanol (6 mL) at
80 °C was added hydrazine monohydrate (0.5 mL). The reaction
mixture was heated at 100 °C in a pressure tube for 2 days while being
monitored by TLC. After cooling, the reaction mixture was diluted with
dichloromethane and filtered. The solvent was removed under reduced
pressure. The crude product was purified by flash chromatography
(silica gel, 0−3% methanol in dichloromethane). The product was
recrystallized from dichloromethane and twice from methanol to
yield yellow crystals (0.073 g, 0.117 mmol, 37%, mp 136 °C). 1H NMR
(400 MHz, CDCl3) δ 9.47 (s, 2H), 4.86 (t, J = 7.6 Hz, 4H), 3.65 (t, J =
7.8 Hz, 4H), 2.08 (quint., J = 7.6 Hz, 4H), 1.97 (quint., J = 7.6 Hz, 4H),
1.60−1.50 (m, 8H), 1.50−1.25 (m, 12H), 0.93 (t, J = 7.2 Hz, 6H), 0.88
(t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ 160.6, 157.4,
149.7, 128.3, 125.7, 124.4, 123.3, 110.9, 42.4, 33.3, 31.8, 31.6, 29.4, 27.8,
26.8, 22.6, 22.5, 14.0, 13.9. HRMS (MALDI) m/z calcd for C38H51N6O2
(MH+), 623.4034; found, 623.4074. Anal. Calcd. for C38H50N6O2: C,
73.28; H, 8.09; N, 13.49. Found: C, 72.69; H, 7.97; N 13.63. IR (KBr) ν
2958, 2927, 2860, 1680 (s), 1457, 1413, 1270, 761 cm−1. We were
unable to obtain an elementally pure sample of 3a (C analysis differs
from calculated value by 0.6%); however, the reported 1H NMR
spectrum (Supporting Information) and X-ray crystal structure of 3a
indicate essential purity of the sample and formation of the desired
structure, respectively.
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Corresponding Author
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Notes
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