Poly(1,1-bis(dialkylamino)propan-1,3-diyl)s; Conformationally-controlled oligomers bearing electroactive groups

Article abstract of DOI:10.1039/b901060b

The design of polymers with repeating [C(NR₂)₂CH ₂CH₂] units which may simultaneously provide conformational control and contain repeating electroactive centres is discussed; (NR₂)₂ groups would be ideally provided by ortho-phenylenediamine derivatives, with 1,8-diaminonaphthalenes as alternatives. Oligomers containing 1,8-bis(methylamino)naphthalenes, up to the hexamer, were obtained by condensation of oligomers of CH₃[COCH ₂CH₂]_nCOCH₃ with 1,8-bis(methylamino)naphthalene, but attempts to prepare related oligomers from 1,2-bis(alkylamino)benzenes were unsuccessful, as only terminal ketone groups could be converted to aminals. Evidence for a strong preference for all-anti conformations of the main chain in the naphthalenediamine oligomers is provided by ring current effects on ¹H NMR shifts, and by X-ray structures, which also provide evidence of intercalation in the solid state. Electrochemical studies of these oligomers show irreversible oxidation of oligomers in solution, but oxidation of longer oligomers leads to the deposition of a reddish-pink insoluble material which shows two reversible oxidation waves. Possible interpretation of these results is discussed. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b901060b

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Poly(1,1-bis(dialkylamino)propan-1,3-diyl)s; conformationally-controlled
oligomers bearing electroactive groups†
Roger W. Alder,* Niall P. Hyland, John C. Jeffery, Thomas Riis-Johannessen and D. Jason Riley
Received 20th January 2009, Accepted 1st April 2009
First published as an Advance Article on the web 8th May 2009
DOI: 10.1039/b901060b
The design of polymers with repeating [C(NR2)2CH2CH2] units which may simultaneously provide
conformational control and contain repeating electroactive centres is discussed; (NR2)2 groups would be
ideally provided by ortho-phenylenediamine derivatives, with 1,8-diaminonaphthalenes as alternatives.
Oligomers containing 1,8-bis(methylamino)naphthalenes, up to the hexamer, were obtained by
condensation of oligomers of CH3[COCH2CH2]nCOCH3 with 1,8-bis(methylamino)naphthalene, but
attempts to prepare related oligomers from 1,2-bis(alkylamino)benzenes were unsuccessful, as only
terminal ketone groups could be converted to aminals. Evidence for a strong preference for all-anti
conformations of the main chain in the naphthalenediamine oligomers is provided by ring current
effects on 1H NMR shifts, and by X-ray structures, which also provide evidence of intercalation in the
solid state. Electrochemical studies of these oligomers show irreversible oxidation of oligomers in
solution, but oxidation of longer oligomers leads to the deposition of a reddish-pink insoluble
material which shows two reversible oxidation waves. Possible interpretation of these results is
discussed.
Introduction
Conducting and semi-conducting polymers are an active re-
search area, with most useful materials being based on extended
p-systems. In this paper we explore the synthesis of some oligomers
that might provide materials whose conductivity would be based
on quite different mechanisms. We were intrigued that one of two
possible charge-hopping mechanisms1–3 might operate (Scheme 1
below), with polymers and oligomers based on the structure
1. Given a highly ordered chain conformation (see below),
through-bond electron transfer via the perfectly aligned (all-anti)
–[CH2CH2]– links might be rapid (Scheme 1(a)), in spite of their
saturated nature. In addition (or alternatively), these compounds
have the potential to organise themselves into intercalated struc-
tures, see Scheme 1(b), so that under appropriate conditions, direct
through-space electron transfer via the stacked p-systems might be
efficient.
In earlier work, we showed that [Ar2CCH2CH2]n polymers
(Ar2 = 2,2¢-biphenylyl) possess essentially straight (all-anti)
chains, and developed routes to oligomers such as 2 and related
polymers involving novel anionic ring-opening polymerisation of
spiro[cyclopropane-1,9¢-fluorene].4,5 The original aim of the work
described in this paper was therefore the preparation of polymers
such as 1, in which the 1,2-bis(alkylamino)benzene units should
Scheme 1 (a) Possible through-bond electron transfer for partially
charged 1; (b) Possible through-space electron transfer in stacked (interca-
lated) structures based on 1.
provide similar conformational control to 2,2¢-biphenylyl units,
but would also be electroactive. Derivatives of N,N¢-dialkyl-
o-phenylenediamines are readily oxidised to long-lived radical
cations and even dications,6–10 and these have been incorporated
into other novel polymeric structures.11 In this paper, we de-
scribe our attempts to prepare oligomers and polymers related
to 1, and preliminary studies of their structure and electro-
chemistry.
School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8
1TS, UK
† Electronic supplementary information (ESI) available: Additional ex-
perimental procedures and 1H and 13C NMR data. CCDC reference
numbers 709694–709697. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/b901060b
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while not introducing other steric interactions.4,5 Thus polymers
like 1 should exhibit all-anti main chains.
Synthetic routes
We initially envisioned two routes to oligomers and polymers
like 1 (Scheme 3).
Results and discussion
Design
Quaternary centres have profound effects on the conformations
of both the adjacent set of bonds and also the set of bonds one
atom away. More distant bonds are normally unaffected. These
effects have been analysed in detail elsewhere,5,12 but they result in
a compound like 4,4-dipropylheptane having two conformations
which are strongly preferred to all others, Scheme 2(a). Two
conformations is one too many(!) for most control purposes,
but if one of the chains is made rigid, this problem can be
overcome, as we showed for the fluorene-based oligomers 2.4,5
Thus, the conformation shown in Scheme 2(b) for 2,3-dihydro-1,3-
dimethyl-2,2-dipropyl-1H-benzo[d]imidazole is more stable than
any other by 10.1 kJ mol-1, according to a Merck Molecular
Force Field (MMFF) conformational search, while the con-
formation shown for 2,3-dihydro-1,3-dimethyl-2,2-dipropyl-1H-
perimidine (Scheme 2(c)) is preferred by 10.9 kJ mol-1. Actually
the aromatic rings in both (b) and (c) are somewhat canted
due to the pyramidisation at the nitrogen atoms but this does
not compromise the conformational control of the main chain.
Note however that the presence of any substituents on the
first two carbon atoms of the R groups creates additional non-
bonded interactions and so partially destroys the conformational
control.
Scheme 3 Routes to polymers 1; (a) Cationic ring-opening polymerisa-
tion of spiro-1,1-diaminocyclopropanes, and (b) aminal formation from
oligomeric/polymeric ketones 5.
1,1-Bis(dialkylamino)cyclopropanes are very reactive towards
electrophiles, and so might undergo cationic ring-opening poly-
merisation. Unfortunately, preliminary experiments using the
known13 1,1-bis-piperidinocyclopropane 3 showed that several
imidazolium ions were not strong enough electrophiles to cause
ring opening, so this route was not pursued further.
Polymer 1 might be prepared alternatively by polyaminal
formation from the ethylene/CO copolymer 4 (Scheme 3(b)).
Two obvious problems with the second route are (a) incomplete
aminal formation, and (b) the insolubility of the ethylene/CO
copolymer. The ethylene/propylene/CO terpolymer is more sol-
uble, but would destroy some of the designed conformational
control. Fortunately, several low-molecular-mass oligomers with
the repeating [COCH2CH2] unit are known, and could provide a
test of the feasibility of route (b).
Scheme 2 Preferred conformations of (a) 4,4-dipropylheptane (b) 2,3-di-
hydro-1,3-dimethyl-2,2-dipropyl-1H-benzo[d]imidazole, (c) 2,3-dihydro-
1,3-dimethyl-2,2-dipropyl-1H-perimidine.
Preparation of CH3[COCH2CH2]nCOCH3 oligomers
In order to explore route (b) in Scheme 3, we required a series of
CH3[COCH2CH2]nCOCH3 oligomers. A repetitive synthesis that
might be extended to any desired chain length would be ideal,
but we have been unable to devise a suitable scheme. However,
acetonylacetone (n = 1) is readily available, and the literature
We have shown that, in a polymeric structure, repeating
quaternary centers need to be placed either 3 or 4 atoms apart in
order to retain conformational control over all bonds in the chain,
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describes a number of methods14–16 for the synthesis of polyketones
with repeating [CH2CH2CO] units. We elected to use procedures
described by Poirier17,18 for the preparation of 2,5,8-nonanetrione
and 2,5,8,11-dodecanetetraone using methylfuran and furan as
respective starting materials (Scheme 4).
Scheme
6
Preparation of N,N¢-dihexyl-1,2-benzenediamine and
Scheme 4 Preparation of 2,5,8-nonanetrione and 2,5,8,11-dodecanete-
traone. Reagents and conditions: (i) Methyl vinyl ketone, BF3·Et2O, EtOH,
MeNO2, -20 ◦C; (ii) HCl, H2O, 100 ◦C.
monomer and dimer aminals. Reagents and conditions: (i) CH3(CH2)4-
COCl, Et3N, 84%; (ii) (CH3(CH2)4CO)2O, 78%; (iii) LiAlH4, THF,
-40 to 66 ◦C, 86%; (iv) Me2CO, HOAc, 87%; (v) acetonylacetone,
p-toluenesulfonic acid, toluene, Dean–Stark trap, 79%.
We extended these methods to prepare 2,5,8,11,14,17-
octadecanehexaone from 2-[2-(2-furyl)ethyl]furan (Scheme 5). 2-
[2-(2-furyl)ethyl]furan was prepared from furoin via reduction
to deoxyfuroin with chlorotrimethylsilane and sodium iodide in
acetonitrile, followed by a modified Wolff–Kishner reduction, as
described by Wenkert et al.19
At this point, a major problem was encountered. Reaction with
2,5,8-nonanetrione, under Dean–Stark conditions only led to low
yields (~15%) of product in which only the terminal carbonyl
groups were converted to aminals; no significant amount (<2%)
of product involving aminal formation at the central carbonyl
groups could be detected, even after 1 week of refluxing. The
same problems were encountered in attempts to synthesise the
tetramer using 2,5,8,11-dodecanetetraone. Although the 5-endo-
trig cyclisation is formally not allowed by Baldwin’s rules, many
5-membered ring acetals and aminals have been prepared in acidic
conditions. We initially believed that the hexyl groups might be
causing the problem, but repetition of this work with ethyl groups
produced the same results; internal carbonyl groups could not be
converted to aminals.
We therefore turned our attention to compounds contain-
ing 1,8-naphthalenediamine units, in spite of the fact that
these were known not to be electroactive in the same way as
o-phenylenediamines.
Scheme 5 Preparation of 2,5,8,11,14,17-octadecanehexaone. Reagents
and conditions: (i) Methyl vinyl ketone, BF3·Et2O, EtOH, MeNO2, -20 ◦C;
(ii) HCl, H2O, 100 ◦C.
Attempted preparation of polyaminals from
Preparation of oligomers containing 1,8-naphthalenediamine units
N,N¢-dialkyl-o-phenylenediamines
N,N¢-Dimethyl-1,8-naphthalenediamine, prepared via N-methyl-
ation of perimidine followed by hydrolysis,23 was readily con-
verted to aminals with both acetone and 3-pentanone. More
significantly, fully protected polyaminals could be prepared from
all the CH3[COCH2CH2]nCOCH3 oligomers in excellent yields
(Scheme 7). We can offer no simple explanation why polyaminal
formation is much more favourable with the apparently bulkier
naphthalenediamines, although the 6-endo-trig nature of the
cyclisation step may play its part.
These polyaminals were found to be quite soluble in chloroform
and dichloromethane, and could be crystallised by diffusion of
ether or pentane into CHCl3 solutions. Although not strictly
correct, we will refer to these oligomers from now on as monomers,
dimers, trimers, etc. for simplicity.
We hoped that it would be possible to prepare polyaminals from
polyketones 4 by reaction with a range of diamines (e.g. 5 in
Scheme 3), or their simple aminal deriviatives (e.g. 6). While
a number of electroactive diamines might be considered,8,20–22
o-phenylenediamines were our preferred choice of diamines for
the synthesis of target oligomers due to the established stability of
their radical cations.
Initially, hexyl chains were chosen as R groups because we
anticipated that the solubility of the oligomeric aminals would be
a problem; these groups would still provide maximum conforma-
tional control. N,N¢-Dihexyl-o-phenylenediamine was prepared
and converted to the monomer and dimer acetals as shown in
Scheme 6.
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with the X-ray structures (see below). We were concerned whether
PM3 gave a good account of the geometry around the nitrogen
atoms in these structures. The simple monomer, 2,2-diethyl-1,3-
dimethyl-2,3-dihydro-1H-perimidine showed very similar ground-
state geometry at the PM3 and B3LYP/6-31G* level, but the
calculated ring-inversion barrier was higher (38 kJ mol-1) with
DFT than PM3 (20 kJ mol-1).
NMR data for oligomers derived from
N,N¢-dimethyl-1,8-naphthalenediamine
1
The H NMR spectrum of the hexamer is shown in Figs. 2(a)
and (b).
Scheme 7 Preparation of oligomeric aminals containing 1,8-naph-
thalenediamine units. Reagents and conditions: (i) CH3[COCH2CH2]n-
COCH3 oligomer, p-toluenesulfonic acid, toluene, Dean–Stark trap,
82–93%.
Modelling oligomers containing 1,8-naphthalenediamine units
For comparison with the X-ray structure discussed below, the 1,8-
naphthalenediamine oligomers were modelled with the PM3 semi-
empirical method in Spartan.24 First, conformational searches
were performed for the dimer and trimer using the MMFF. As
expected, this showed that conformations with an all-anti main
chain were the lowest energy by a substantial margin. It was not
possible to extend these searches to the tetramer or hexamer, but
the all-anti conformers were modelled, first with the MMFF, and
then using PM3. The preferred structures are shown in Fig. 1.
Note that the aromatic moieties are tilted with respect to the main
chain, reflecting pyramidalisation of the nitrogen atoms. It was
found that structures with the nitrogen lone pairs on the terminal
1,8-naphthalenediamine units pointing inwards were preferred to
alternatives where these pointed outwards, and this is in accord
Fig. 2 IH NMR spectrum of the hexamer; (a) aromatic region, (b)
aliphatic region.
In the aromatic region, the doublets at d 6.1–6.3 ppm represent
the ortho protons in the naphthalene ring. Para protons are
represented by three doublets at d 6.8–7.0 ppm, while the meta
protons are at d 7.0–7.2 ppm. The differential shielding within
these groups must result from ring current effects from distant
aromatic rings; those in the central naphthalene unit likely being
shifted furthest upfield. Fig. 2(b) displays the aliphatic protons;
the peaks at d 0.96 ppm (terminal CH3s) and the three peaks at
d 2.7 ppm (N–Me) are singlets. The peaks at d 1.4–1.7 ppm are
1
complex multiplets representing the 20 protons in the chain. H
NMR chemical shifts for other monomers and oligomers are listed
in Table 1.
Fig. 1 Calculated structures for the (a) tetramer, and (b) hexamer.
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Table 1 1H NMR chemical shifts of protons in monomers and oligomers
Molecule
Me2C (monomer)
Et2C (monomer)
8 (dimer)
9 (trimer)
10 (tetramer)
11 (hexamer)
Cq–CH3
CH2
CH2
N–CH3
1.4
—
—
2.97
6.6
—
—
—
—
—
—
—
—
2.96
6.4
—
—
—
1.31
1.93
1.93
2.76
6.47
—
7.26
—
7.26
—
1.19
1.09
0.96
1.66–1.71
1.93–1.97
2.77
6.45
6.22
7.7
7.20
7.15
7.02
1.61–1.67
1.79–1.85
2.71
6.42
6.26
7.24
7.24
7.11
7.03
1.45–1.55
1.64–1.70
2.59
6.3
6.15
7.11
7.11
6.98
6.86
ortho-H(terminal)
ortho-H(central)
meta-H(terminal)
meta-H(central)
para-H(terminal)
para-H(central)
—
—
In general, the longer the chain size, the more shielded almost all
the protons become. Thus the terminal methyl groups of the chain
are at 1.4 ppm for the model monomer but are steadily shifted
upfield to 0.96 ppm for the hexamer. Methylene protons in the
main chain become more shielded due to ring current shielding
by the naphthalene units in the chain, as do the N–Me groups
and this pattern is also replicated in the aromatic protons, with
the central oligomer units shifted more than the terminal ones.
This information corresponds with our published data on the
fluorene oligomers 2, but, perhaps because the naphthalene units
are displaced more to either side of the main chains, the shifts are
less dramatic than for the fluorenes.
due to packing forces. The naphthalene diamine units are not
perpendicular to the main chain, and the nitrogen atoms are quite
pyramidal. These factors undoubtedly also contribute to the low
degree of conformational control of the main C6 chain in the solid-
state structure.
Trimer crystals (CCDC 709695†), obtained by slow diffusion of
pentane into a chloroform solution, were very weakly diffracting
due to extensive disorder. The cause of this is clear: channels of ca.
˚
12 A in diameter propagate along the crystallographic c-axis and
provide such an effective means of escape for the co-crystallized
solvent (CHCl3) that removal of the crystal from the mother liquor
results in immediate collapse of the lattice (Fig. 4). Nevertheless,
¯
the structure was solved in the tetragonal space group P421c using
X-Ray structural data for oligomers derived from
N,N¢-dimethyl-1,8-naphthalenediamine
standard direct methods, and 2.5 crystallographically independent
trimer units were found in the asymmetric unit (one lies astride
a two-fold rotation axis). Although the structure is insufficiently
resolved to merit detailed analysis of geometric parameters, as
with the dimer, conformational control along the central C9 chain
appears limited.
X-Ray diffraction data was collected for crystals of the dimer,
trimer, tetramer and hexamer. We will discuss these structures in
turn, but note that the conformations become more regular as
the chain grows longer, encouraging the idea that the internal
section of an extended polymer would have a highly controlled
conformation, as intended.
The dimer (CCDC 709694†) crystallised in the orthorhombic
space group Pna21 and one crystallographically independent
molecule was found in the unit cell. Anomalous scattering was
insufficient to determine the absolute structure but we were able
to locate and refine hydrogens without positional constraints. The
dimer (Fig. 3) is not as conformationally controlled as we had
expected. There is significant twisting along the chain as evidenced
by the C1–C2–C3–C4 dihedral angle of ca. 58◦. This is perhaps
Fig. 4 Packing diagram for the trimer 9 as viewed down the crystallo-
graphic c-axis.
The solid-state structure of the tetramer (CCDC 709696†) is
shown in Fig. 5 and that of the hexamer in Fig. 6.
The tetramer was crystallised from chloroform–hexane, and
both solvents are present in the lattice as slightly disordered
solvates. The hexamer (CCDC 709697†) was crystallised from
chloroform–diethyl ether, and well-ordered molecules of the latter
occupy the clefts between adjacent naphthalene units on the same
side of the main chain in the structure, as can be seen in Fig. 7.
Fig. 3 Solid-state structure of the dimer 8. Thermal ellipsoids are shown
at a 50% probability level. Hydrogens have been omitted for clarity.
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planar (sum of angles around nitrogen ~358◦ for the inner rings in
the tetramer and ~354◦ in the hexamer). The detailed structures
are undoubtedly influenced by packing forces, and these can
apparently force the inner nitrogen close to planarity. Nevertheless,
it does seem clear that conformational control is stronger towards
the interior of the chain, and that in an extended polymer, the
inner portion would resemble our proposed model quite closely.
Attempted polymer synthesis
Ethylene/propylene/CO terpolymer was refluxed with N,N¢-
dimethyl-1,8-naphthalenediamine with a catalytic amount of
p-toluenesulphonic acid in toluene. The mixture was refluxed for
a number of weeks, but no conversion of ketone to aminal groups
could be detected by infra-red spectroscopy and the majority of
the product after refluxing for this time was starting material.
A number of related procedures were tried with no success. We
presume that the difficulty is the extreme insolubility of the
polymeric ketone.
Fig. 5 Solid-state structure of the tetramer 10. Thermal ellipsoids are
shown at a 50% probability level. Hydrogens have been omitted for clarity.
The symmetry operator for generating equivalent atoms (_2) is: 1 - x,
1 - y, 1 - z.
Cyclic voltammetry of oligomeric derivatives of
1,3-dialkyl-2,2-disubstituted 2,3-dihydro-1H-perimidines
One of our principal aims in making the compounds of the
type previously described was to study their redox chemistry and
electrochemical behaviour. As described above, we were unable to
prepare suitable derivatives of N,N¢-dialkyl-o-phenylenediamines.
While the related polyaminals derived from N,N¢-dimethyl-
1,8-naphthalenediamine could be prepared, simple derivatives
of N,N¢-dialkyl-1,8-naphthalenediamine unfortunately do not
show reversible oxidation. One possible way out would be
to make derivatives of corresponding oligomers derived from
1,4,5,8-tetraaminonaphthalenes, since these have been shown to
undergo reversible oxidation.20–22 However, synthesis of these
molecules is complicated, so this was not pursued. In spite of
all the anticipated difficulties, the electrochemical behaviour of
the dimer, trimer, tetramer and hexamers derived from N,N¢-
dialkyl-1,8-naphthalenediamines was investigated. The monomers
1,2,2,3-tetramethyl-2,3-dihydro-1H-perimidine, and 2,2-diethyl-
1,3-dimethyl-2,3-dihydro-1H-perimidine were also examined for
comparison.
Fig. 6 Solid-state structure of the hexamer 11. Thermal ellipsoids are
shown at a 50% probability level. Hydrogens have been omitted for clarity.
The symmetry operator for generating equivalent atoms (_3) is: 2 - x,
1 - y, 2 - z.
All the compounds above behaved essentially similarly during
initial oxidation scans, each showing completely irreversible
oxidation waves at +0.55 0.1 V versus SCE. However, with
the trimer 9 (Fig. 8), tetramer 10, and hexamer 11 (but not the
dimer 8 (inset in Fig. 8) or monomers), new reversible waves were
observed which grew on repeated cycling. A red insoluble material
was deposited on the electrode at the same time. For trimer 9
(Fig. 8), a pair of reversible peaks appeared at ca. -0.1 and +0.1 V
that increased in intensity with cycling, the peak current density
for the oxidation of the oligomer decreased with cycling as the
electrode became coated with polymer. For the tetramer 10, the
pair of reversible peaks appeared at ca. -0.15 and +0.1 V. It was
noticed that the peak height of the latter was 2–3 times that of
the former; peak separations were about 0.1 V. Finally, for the
hexamer 11, the pair of reversible peaks again appeared at ca.
-0.15 and +0.1 V, but now the wave at ca. +0.1 V was more than
3 times bigger than the one at ca. -0.15 V.
Fig. 7 Packing diagram for the hexamer as viewed down the crystallo-
graphic a-axis.
In spite of this, there is a limited amount of intercalation between
naphthalenes from adjacent molecules.
The oligomer chains in both the tetramer and hexamer are
all-anti as expected from our calculations: the carbon-backbone
dihedral angles in the solid-state structures range from 164(1)◦
(between the two outer naphthalenediamines in the tetramer) to
180(1)◦. It is interesting to compare these structures with the PM3
models. In both, the outer naphthalenediamines have strongly
pyramidal nitrogen atoms pointing inwards. However, the internal
naphthalenediamines are much closer to being perpendicular to
the main chain, and their nitrogen atoms are significantly more
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Scheme 8 Possible intercalation.
by chemical, electrochemical and even enzymatic oxidation of
anilines. These studies have been extended to the oxidative
polymerisation of many aromatic diamines,25 including 1,8-
diaminonaphthalene. The proposed26 structure for poly(1,8-
diaminonaphthalene) is shown in Scheme 9(a). This structure has
both 1,4- and 1,5-linked naphthalenes, although there is no clear
evidence which supports this, and formation of corresponding
structures from our oligomers would require rupture of the
aminal units or demethylation. 1,8-Diaminonaphthalenes can
undergo oxidative dimerisation to 4,9-diaminoperylenequinone-
3,10-diimines,27 admittedly under rather different conditions
(see Scheme 9(b)). This suggests the possibility of a polymer
structure based on 4,4-coupling of the naphthalene units as
another alternative. Such a linkage would be expected to give
a stable radical cation, as shown in Scheme 9(c), but could
get oxidised further to a perylene derivative. It is noteworthy
that the electronic spectrum of the polymer film is relatively
similar to that reported for 4,9-diaminoperylenequinone-3,10-
diimines.27
Fig. 8 Cyclic voltammograms of the trimer 9 and the dimer 8 (inset). The
I–V curves were recorded at a scan rate of 50 mV s-1.
These results suggested that some kind of aggregation or
polymerisation process was occurring, and so we examined one
of these oligomers, using a transparent indium tin oxide electrode
suitable for spectroelectrochemical studies. It was found that a
pinkish-red, conducting, film was deposited on the electrode, and
an electronic spectrum of this film, in the reduced state, was
obtained (Fig. 9).
Fig. 9 UV–visible spectrum of the polymer deposited on an ITO electrode
during a cyclic voltammetric study of the trimer 9.
Possible structures for the conducting film
Without more detailed studies, it is only possible to speculate
about the nature of this polymer film. As discussed previously,
these oligomers were designed to be able to intercalate and/or
stack. The formation of a conducting polymer film through non-
covalent interactions of this type would be novel and worthy of
extended study. Therefore, it can be pointed out that conducting
films are only formed from trimer 9 onwards, and this is surely the
smallest oligomer which could form a stable intercalated structure,
as shown in Scheme 8.
Scheme 9 (a) Suggested structure for poly(1,8-diaminonaphthalene)26;
(b) Structure of 4,9-diaminoperylenequinone-3,10-diimines27; (c) Sug-
gested structure for a 4,4-linked unit in the oxidised film.
Conclusions
An alternative view would be that some form of covalent
polymerisation process is occurring to lay down the polymer
film. Polyanilines have received considerable attention, prepared
A series of oligomeric polyaminals derived from N,N¢-dimethyl-
1,8-naphthalenediamine up to the hexamer 11 were pre-
pared. Attempts to prepare the corresponding oligomers with
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N,N¢-dialkyl-o-phenylenediamine-derived pendant groups were
frustrated by the unreactivity of internal ketone groups of
polyketones towards aminal formation with these diamines. This
result with the apparently less bulky diamine is puzzling. The
naphthalene-derived oligomeric polyaminals proved to be quite
tractable, and were characterised using NMR spectroscopy and
X-ray diffraction. The conformational preference for all-anti
main chains increases with chain length, and the structures show
interesting alignments of the aryl groups and signs of intercalation.
However, these oligomers do not show simple oxidation behaviour,
but form deposits on the electrode, suggesting that some form of
electropolymerisation is occurring.
nitromethane (30 mL) in a flask under nitrogen with stirring.
The solution was cooled to -20 ◦C and a solution of boron
trifluoride etherate (0.64 g, 4.48 mmol) in ethanol (1.03 g,
22.4 mmol) was prepared in a separate flask under nitrogen.
The catalyst was added dropwise to the solution at -20 ◦C
with stirring resulting in a red colour. Stirring was contin◦ued for
90 min at which the brown solution was warmed to -10 C and
NaHCO3 (saturated solution, 30 mL) was added. The product
was extracted with dichloromethane (4 ¥ 40 mL), dried over
MgSO4, filtered, concentrated in vacuo and purified by flash
column chromatography (silica gel 60H, hexane–diethyl ether, 30 :
70) to afford the desired ◦product as a white crystalline powder
(1.39 g, 41%). M.p. 57–58 C; 1H NMR (400 MHz; CDCl3) d 2.16
(6 H, s), 2.73–2.89 (8 H, m), 2.88 (4 H, s), 5.86 (4 H, s); 13C NMR
(100 MHz; CDCl3) d 22.4 & 26.9 (C-1¢, -4¢, 2t), 29.9 (C-1, q), 41.9
(C-3¢, t), 105.7 (C-3, -4, 4d), 152.9 & 153.5 (C-2, -5, 4 s), 207.4
(C-2¢, 2 s); MS m/z (EI) 302 (M+, 21), 151 (100), 107 (24), 94 (13)
81 (29) 55 (9); Anal. Calcd for C18H22O4: C, 71.50; H, 7.33. Found
Experimental
General procedures
1H and 13C NMR spectra were recorded on JEOL Eclipse 400
or JNM-GX400 spectrometers. Chemical shifts (d) are quoted
in parts per million downfield from tetramethylsilane (TMS).
Coupling constants (J) are expressed in Hertz (Hz). The following
abbreviations for multiplicities have been used: (s) singlet, (d)
doublet, (t) triplet, (q) quartet, (qn) quintet, (sp) septet, and (m)
multiplet. The abbreviation (br) is used as a prefix if the signal
showed broadening. When broadening was very large, the range
is given.
Low-resolution mass spectra (m/z) were recorded in the Fast
Atom Bombardment (FAB), Electron Impact (EI) (70 eV) or
Chemical Ionisation (CI) modes using a Fisons VG Analytical
Autospec spectrometer with only molecular ions (M+ or [M + H]+),
and major peaks being reported with intensities being quoted as
percentages of the base peak. High-resolution EI and CI mass
determinations were performed on the same instrument as the
corresponding low-resolution spectra.
C, 71.38; H, 7.39; IR (ATR) nmax/cm-1 2920 (C–H & C C), 1712
=
=
=
(C O), 1567 (C C), 1161 (C–O–C).
2,5,8,11,14,17-Octadecanehexaone. 3 M HCl (8.5 mL) was
added to a solution of 4-(5-2-[5-(3-oxobutyl)-2-furyl]ethyl-2-
furyl)-2-butanone (0.50 g, 1.65 mmol) with stirring. The solu-
tion was refluxed for 2 h and the product was extracted with
dichloromethane (4 ¥ 20 mL), dried over MgSO4, filtered and
concentrated under reduced pressure to afford the desired product.
Further purification involved crystallisation from hot ethanol,
affording a white crystalline powder (0.51 g, 91%). M.p. 142–
143 ◦C; 1H NMR (400 MHz; CDCl3) d 2.05 (6 H, s), 2.59 (4 H, s),
2.61 (8 H, 2 s); 13C NMR (100 MHz; CDCl3) d 29.7 (C-1, q), 36.0
(t), 36.8 (t), 37.2 (t), 207.2 (C-2, s), 208.1 (C-5, -8, 2 s); MS m/z
(EI) 338 (M+, 1), 320 (2), 302 (2), 267 (14) 249 (16) 211 (58), 165
(54), 151 (87), 127 (97), 107 (54), 99 (100), 71 (41), 55 (50); Anal.
Calcd for C18H26O6: C, 63.89; H, 7.74. Found C, 64.00; H, 7.62;
Elemental combustion analyses were performed using a Perkin–
Elmer 240C elemental analyser and were performed by the staff
of the microanalytical department at the School of Chemistry,
University of Bristol.
IR (ATR) nmax/cm-1 2911 (C–H), 1691 (C O), 1172 (C–O).
=
1,3-Dihexyl-2,2-dimethyl-2,3-dihydro-1H-benzo[d]imidazole. Ace-
tic acid (55 mL, 0.90 mmol) was added to a solution of N,N-
dihexyl-1,2-benzenediamine (2.48 g, 9.0 mmol) in acetone (20 mL)
with stirring under nitrogen. The solution was refluxed for 20 h.
The acetone was removed under reduced pressure and diethyl
ether (40 mL) was added. The solution was washed with water
(2 ¥ 30 mL), dried over MgSO4, filtered, and the solvent removed
under reduced pressure. The resulting black oil was purified by
column chromatography (neutral alumina, hexane–ethyl acetate,
95 : 5) to afford the desired product as a brown solid (2.48 g,
GC-MS was performed using an Agilent 6890 apparatus
equipped with a capillary column HP-5MS (HP190915–433, 5%
phenyl pethyl siloxane, 30 m ¥ 250 mm ¥ 0.25 mm nominal) under
the following conditions: helium 1 mL min-1 (constant-flow mode),
injector ◦250 ◦C (splitle◦ss mode), detector EI (Agilen MSD 5973),
oven 70 C (3 min), 15 C min-1 (15.3 min), 300 ◦C (18 min) unless
otherwise specified.
4-(5-Methyl-2-furyl)-2-butanone, 2,5,8-nonanetrione, 4-[5-(3-
oxobutyl)-2-furyl]-2-butanone, and 2,5,8,11-dodecanetetraone
were prepared using the procedures of Poirier and Dujardin.17,18
Preparative details for 1,2-di(2-furyl)-1-ethanone,19 2-[2-(2-furyl)-
ethyl]furan,19 N-[2-(acetylamino)phenyl]acetamide, N,N-diethyl-
1,2-benzenediamine, N-[2-(hexanoylamino)phenyl]hexanamide,
N,N-dihexyl-1,2-benzenediamine, 2-methyl-1H-perimidine,28 1,2-
dimethyl-1H-perimidine,23 1,2-dimethylperimidinyl methiodide,23
and 1,2,2,3-tetramethyl-2,3-dihydro-1H-perimidine29 are in the
ESI†.
1
87%). H NMR (400 MHz; CDCl3) d 0.89 (6 H, t, J = 7.0 Hz),
1.27 (6 H, s), 1.30–1.40 (12 H, m), 1.62 (4 H, m), 2.95 (4 H, t,
J = 7.3 Hz), 6.17 (2 H, dd, J = 3.3, 2.9 Hz), 6.50 (2 H, dd, J =
3.0, 3.3 Hz); 13C NMR (100 MHz; CDCl3) d 14.2 (C-6¢, 2q),
22.6 (C-5¢, 2t), 22.8 (C-4¢, 2t), 27.2 (C-1, 2q), 29.6 (C-3¢, 2t), 31.8
(C-2¢, 2t), 43.9 (C-1¢, 2t), 86.9 (C-2, s), 102.9 (C-4, -7, 2d), 117.2
(C-5, -6, 2d), 140.5 (C-3a, -8, 2q); MS m/z (EI) 316 (M+, 22), 301
(100), 272 (20), 229 (26), 217 (15), 201 (21), 159 (14), 145 (30), 133
(26), 119 (20), 55 (10); HRMS found 316.2884, C21H36N2 requires
316.2879. IR (ATR) nmax/cm-1 2926 (C–H), 1312 (tertamine) &
1174, 1109, 874 (1,2-disubstituted benzene).
4-(5-[2-[5-(3-Oxobutyl)-2-furyl]ethyl]-2-furyl)-2-butanone.
A
solution of but-3-en-2-one (1.57 g, 22.4 mmol) was added to
a mixture of 2-[2-(2-furyl)ethyl]furan (1.84 g, 11.2 mmol) and
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2-[2-(1,3-Dihexyl-2-methyl-2,3-dihydro-1H-benzo[d]imidazol-2-
yl)ethyl]-1,3-dihexyl-2-methyl-2,3-dihydro-1H-benzo[d]imidazole
7. Dimer 7 was prepared from N,N-dihexyl-1,2-benzenediamine
(1.21 g, 4.38 mmol), acetonylacetone (0.25 g, 2.19 mmol) and
p-toluenesulphonic acid (83.0 mg, 0.44 mmol) in toluene (20 mL).
The solution was refluxed under nitrogen for 20 h using a flask
provided with a condenser and a Dean–Stark trap. The toluene was
removed under reduced pressure and dichloromethane (30 mL)
was added. The solution was washed with NaHCO3 (saturated
solution, 2 ¥ 20 mL), water (2 ¥ 20 mL), dried over MgSO4,
filtered and concentrated in vacuo to give a black oil. This
oil was purified by column chromatography (neutral alumina,
hexane–ethyl acetate, 99 : 1) to afford green crystals which were
recrystallised from hot methanol, precipitating the d◦esired product
was neutralised with glacial acetic acid until the pH was weakly
basic to litmus. A brown solid precipitated out during this time.
The solid was filtered, washed with water and dried under reduced
pressure to yield the desired amine. The crude material was
purified by column chromatography (neutral alumina, hexane–
dichloromethane, 60 : 40) to afford the desi◦red product as◦a light-
1
brown solid (20.8 g, 66%). M.p. 102–103 C (Lit.,30 101 C); H
NMR (400 MHz; CDCl3) d 2.81 (6 H, s), 5.40 (2 H, br s), 6.52
(2 H (H 2 & 7), br dd, J = 7.3, 1.0 Hz), 7.18 (2 H (H 4 & 5), br dd,
J = 8.3, 1.5 Hz), 7.24 (2 H (H 3 & 6), br dd, J = 8.0, 7.6 Hz); 13
C
NMR (100 MHz; CDCl3) d 32.3 (C-1¢, q), 106.6 (C-2, d), 117.1
(C-8a, s), 119.3 (C-4, d), 126.6 (C-3, d), 137.0 (C-1, s), 147.9 (C-8a,
s); MS m/z (EI) 186 (M+, 100), 168 (83) 154 (57), 143 (23), 127 (38),
115 (46); Anal. Calcd for C12H14N2: C, 77.38; H, 7.58; N, 15.04.
Found C, 77.52; H, 7.60; N, 14.75; IR (ATR) nmax/cm-1 3354
(aromatic secN–H), 3052 (aromatic C–H), 2902 (aliphatic C–H),
1300 (secamine), 1585, 806 & 752 (1,2,3-trisubstituted aromatic).
1
as fine white crystals (1.09 g, 79%). M.p. 83–84 C; H NMR
(400 MHz; CDCl3) d 0.83 (12 H, t, J = 6.8 Hz), 1.12 (6 H, s),
1.25 (28 H, br m), 1.54 (4 H, s), 1.61 (8 H, m), 2.90 (8 H, m),
6.03 (4 H, dd, J = 3.1, 3.4 Hz), 6.41 (4 H, dd, J = 3.2, 3.2 Hz));
13C NMR (100 MHz; CDCl3) d 14.1 (C-6¢, 4q), 22.8 (C-5¢, 4t),
24.1 (C-1, 4q), 27.3 (C-4¢, 4t), 29.0 (C-3¢, 4t), 31.0 (C-¢2, 2t), 31.8
(C-2¢, 4t), 43.6 (C-1¢, 4t), 88.3 (C-2, 2 s), 101.7 (C-4, -7, 2d), 116.7
(C-5, -6, 2d), 140.6 (C-3a, -7a, 4 s); MS m/z (EI) 631 (M+, 2), 313
(32), 301 (100) 145 (9), 133 (8); HRMS found 630.5609, C42H70N4
requires 630.5601; Anal. Calcd for C42H70N4: C, 79.94; H, 11.18;
N, 8.88. Found C, 80.48; H, 11.13; N, 9.11; IR (ATR) nmax/cm-1
2925 (C–H), 1300 (tertamine) & 1159, 1119, 870 (1,2-disubstituted
benzene).
2,2-Diethyl-1,3-dimethyl-2,3-dihydro-1H-perimidine. To a so-
lution of N,N¢-dimethyl-1,8-naphthalenediamine (0.62 g,
3.33 mmol) and pentan-3-one (0.32 g, 0.37 mmol) in toluene
(10 mL) was added p-toluenesulphonic acid (63.3 mg, 0.33 mmol)
in a flask under nitrogen with stirring. The solution was refluxed
˚
for 20 h in the presence of 4 A molecular sieves. The toluene was
removed under reduced pressure and dichloromethane (20 mL)
was added. The solution was washed with NaHCO3 (saturated
solution, 2 ¥ 15 mL), water (2 ¥ 15 mL), dried over MgSO4,
filtered and concentrated under reduced pressure to give a brown
solid. This solid was purified by column chromatography (neutral
alumina, hexane–dichloromethane, 80 : 20) to afford the desired
product as a white solid (0.75 g, 80%). M.p. 97–98 ◦C.
2-[2-(1,3-Diethyl-2-methyl-2,3-dihydro-1H-benzo[d]imidazol-2-
yl)ethyl]-1,3-diethyl-2-methyl-2,3-dihydro-1H -benzo[d]imida-
zole. The dimer was prepared from N,N-diethyl-1,2-benzenedi-
amine (1.45 g, 8.84 mmol), acetonylacetone (0.50 g, 4.42 mmol)
and p-toluenesulphonic acid (168.0 mg, 0.88 mmol) in toluene
(15 mL). The solution was refluxed under nitrogen for 20 hours us-
ing a flask provided with a condenser and a Dean–Stark trap. The
toluene was removed under reduced pressure and dichloromethane
(30 mL) was added. The solution was washed with NaHCO3
(saturated solution, 2 ¥ 20 mL), brine (2 ¥ 20 mL), dried over
MgSO4, filtered and concentrated under reduced pressure to give
a black oil. This oil was purified by column chromatography
(neutral alumina, hexane–dichloromethane, 85:15) to afford the
desired product as a blue solid. This blue powder was◦recrystallised
from isopropyl alcohol (1.53 g, 85%). M.p. 140–142 C; 1H NMR
(400 MHz; CDCl3) d 1.19 (6 H, s), 1.23 (12 H, t, J = 7.0), 1.72 (4
H, s), 2.98 - 3.19 (8 H, m), 6.16 (4 H, dd, J = 3.4, 2.9 Hz), 6.49 (4
H, dd, J = 3.4, 3.4 Hz); 13C NMR (100 MHz; CDCl3) d 14.3 (C-2¢,
q), 23.1 (C-1, q), 31.1 (C-¢2, t), 37.2 (C-1¢, t), 88.6 (C-2, s), 102.0
(C-4, -7, d), 116.9 (C-5, -6, d), 140.2 (C-3a, 7a, s); MS m/z (EI)
406 (M+, 12), 201 (12) 189 (100), 160 (20), 145 (28), 133 (25), 119
(6), 92 (10); HRMS found 406.3089, C26H38N4 requires 406.3096;
IR (ATR) nmax/cm-1 2980 (C–H), 1330 (tertamine), 1165, 1112, 929
(1,2-disubstituted benzene).
1,2,3-Trimethyl-2-[2-(1,2,3-trimethyl-2,3-dihydro-1H-2-peri-
midinyl)ethyl]-2,3-dihydro-1H-perimidine 8. Dimer 8 was pre-
pared from a solution of N,N¢-dimethyl-1,8-naphthalenediamine
(0.34 g, 1.81 mmol), acetonylacetone (0.10 g, 0.90 mmol) and
p-toluenesulphonic acid (17.2 mg, 0.09 mmol) in toluene (5 mL).
The solution was refluxed under nitrogen for 20 h using a flask
provided with a condenser and a Dean–Stark trap. The toluene was
removed under reduced pressure and dichloromethane (20 mL)
was added. The solution was washed with NaHCO3 (saturated
solution, 2 ¥ 15 mL), water (2 ¥ 15 mL), dried over MgSO4,
filtered and concentrated under reduced pressure to give a brown
solid. This brown solid was purified by column chromatography
(neutral alumina, hexane–dichloromethane, 70 : 30) to afford a
white powder. Further purification involved crystallisation from
hot ethanol or dissolving in a minimum amount of toluene
and crystallisation by slow diffusion of pentane, precipitating
colourless crystals (1.76 g, 89%). M.p. 147–150 ◦C.
2-(2-[1,3-Dimethyl-2-[2-(1,2,3-trimethyl-2,3-dihydro-1H-2-peri-
midinyl)ethyl]-2, 3-dihydro-1H -2-perimidinylethyl)]-1, 2, 3-tri-
methyl-2,3-dihydro-1H-perimidine 9. Trimer 9 was prepared
from a solution of N,N¢-dimethyl-1,8-naphthalenediamine (0.62 g,
3.34 mmol), 2,5,8-nonanetrione (0.14 g, 0.83 mmol) and
p-toluenesulphonic acid (16.0 mg, 0.08 mmol) in toluene (5 mL).
The solution was refluxed under nitrogen for 20 h using a flask
provided with a condenser and a Dean–Stark trap. The toluene was
removed under reduced pressure and dichloromethane (20 mL)
was added. The solution was washed with NaHCO3 (saturated
N,N¢-Dimethyl-1,8-naphthalenediamine. Nitrogen was bub-
bled through a solution of potassium hydroxide (145.6 g, 2.60 mol)
in ethanol (800 mL) for 5 min. 1,2-Dimethylperimidinyl methio-
dide (58.45 g, 0.17 mol) was added in one portion to the alkaline
ethanolic solution and the resultant solution was refluxed under
nitrogen. After 3 h, the reaction mixture was cooled and diluted
with water to yield a final volume of 2.5 L. The resulting solution
2712 | Org. Biomol. Chem., 2009, 7, 2704–2715
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solution, 2 ¥ 15 mL), water (2 ¥ 15 mL), dried over MgSO4, filtered
and concentrated under reduced pressure to give a brown solid.
This brown solid was purified by column chromatography (neutral
alumina, dichloromethane) to afford the desired product as a white
powder. Further purification involved dissolving in a minimum
amount of chloroform and crystallising by slow diffusion of
pentane, precipitating fine colourless crystals (0.47 g, 84%). M.p.
268–269◦C.
epoxy resin, mounted on a glass fibre and quickly transferred
to a Bruker-AXS SMART or PROTEUM (CCD area-detector)
diffractometer under a stream of cold N2 gas. Preliminary scans
were taken to assess crystal quality, lattice symmetry, ideal expo-
sure time etc. prior to collecting a sphere or hemisphere (for low-
and high-symmetry crystal systems respectively) of diffraction
intensity data using SMART operating software.31 Intensities were
then integrated from several series of exposures (each exposure
covering 0.3◦ in w), merged and corrected for Lorentz and polar-
isation effects using SAINT software.32 Solutions were generated
by conventional heavy-atom Patterson or direct methods and
refined by full-matrix non-linear least squares on all F2 data, using
SHELXS-97 and SHELXL software respectively (as implemented
in the SHELXTL suite of programs).33 Empirical absorption
corrections were applied based on multiple and symmetry-
equivalent measurements using SADABS.34 All structures were
refined until convergence (max shift/esd <0.01) and in each case,
the final Fourier difference map showed no chemically sensible
features. Crystallographic refinement parameters are summarised
in Table 2.
Tetramer 10. Tetramer 10 was prepared from a solution
of N,N¢-dimethyl-1,8-naphthalenediamine (1.85 g, 9.96 mmol),
2,5,8,11-dodecanetetraone (0.50 g, 2.21 mmol) and p-toluene-
sulphonic acid (42 mg, 0.22 mmol) in toluene (10 mL). The
solution was refluxed under nitrogen for 20 h using a flask provided
with a condenser and a Dean–Stark trap. The toluene was removed
under reduced pressure and dichloromethane (30 mL) was added.
The solution was washed with NaHCO3 (saturated solution, 2 ¥
20 mL), water (2 ¥ 20 mL), dried over MgSO4, filtered and
concentrated under reduced pressure to give a brown solid. This
brown solid was purified by column chromatography (neutral
alumina, dichloromethane) to afford the desired product as a white
powder. Further purification involved dissolving in a minimum
amount of chloroform and crystallising by slow diffusion of
pentane, ◦precipitating fine colourless crystals (1.62 g, 82%). M.p.
Dimer 8. All hydrogens were located in the Fourier difference.
map and refined without positional constraints. Anomalous
scattering was not sufficient to determine absolute configuration.
1
159–160 C; H NMR (400 MHz; CDCl3) d 1.09 (6 H, s), 1.61–
Trimer 9. As discussed in the text, crystals of the trimer 9
are extensively disordered due to rapid solvent loss on removal
from the mother liquor, which in turn causes partial collapse
of the crystal lattice. The data obtained was measured from
a pre-cooled crystal, which was transferred rapidly from the
mother liquor to the cryostream, and it constitutes the best of
numerous attempts. In the large channels between the stacked
trimer units were located ca. three CHCl3 solvent molecules (per
asymmetric unit). However, these were so poorly resolved that
attempts to model their geometries and positional disorder were
abandoned in favour of removing their scattering contributions
using the SQUEEZE routine in PLATON.35 These solvents have
been included in the moiety formula. The 2.5 fragments of trimer
located in the asymmetric unit are also poorly resolved. Rigid-
body constraints were applied for many of the naphthalenyl
rings during the early stages of refinement to enforce sensible
geometries. These were then replaced by extensive distance,
similarity and planarity restraints (DFIX, SAME and FLAT) for
the final stages of refinement. Hydrogens were placed in calculated
positions and refined with riding constraints and with isotropic
displacement parameters 1.2¥ or 1.5¥ their parent carbons (for sp2
and sp3 carbons respectively). Methyl hydrogens were, however,
not included in the model as reliable positions could not be
determined. We stress that the structure of the trimer 9 does
not merit detailed analysis beyond establishing its basic atomic
connectivity.
1.67 & 1.79–1.85 (8 H, m), 1.69 (4 H, s), 2.70 (12 H, s), 2.71 (12 H,
s), 6.26 (4 H, br d, J = 7.8 Hz), 6.42 (4 H, br d, J = 7.5 Hz), 7.03
(4 H, br d, J = 8.3 Hz), 7.11 (4 H, br d, J = 8.3 Hz), 7.24 (12 H, br
dd, J = 8.5, 7.9 Hz); 13C NMR (100 MHz; CDCl3) d 19.3 (C-1, q),
30.1 (C-1, t), 31.0 (C-2, t), 32.8 (C-1, q), 33.4 (C-1, q), 75.0 (C-2, s),
78.2 (C-2, s), 100.7 (C-4, d), 105.2 (C-4, d), 110.5 (C-9b, s), 114.3
(C-9b, s), 115.6 (C-6, d) 117.1 (C-6, d), 126.9 (C-5, d), 127.3 (C-5,
d), 133.7 (C-6a, s), 133.9 (C-6a, s), 141.8 (C-3a, s), 142.5 (C-3a,
s); MS m/z (FAB) 899 ([M + H]+, 2) 660 (16), 435 (38), 223 (12),
211 (100), 196 (43) 182 (9), 168 (14); Anal. Calcd for C60H66N8:
C, 80.14; H, 7.40; N, 12.46. Found C, 80.53; H, 7.74; N, 12.40;
IR (ATR) nmax/cm-1 3049 (aromatic C–H), 2861 (aliphatic C–H),
1329 (tertamine), 1575, 803 & 749 (1,2,3-trisubstituted aromatic).
Hexamer 11. Hexamer 11 was prepared from a solution
of N,N¢-dimethyl-1,8-naphthalenediamine (0.54 g, 2.90 mmol),
2,5,8,11,14,17-octadecanehexaone (0.14 g, 0.41 mmol) and
p-toluenesulphonic acid (7.8 mg, 0.04 mmol) in toluene (4 mL).
The solution was refluxed under nitrogen for 20 h using a flask
provided with a condenser and a Dean–Stark trap. The toluene was
removed under reduced pressure and dichloromethane (30 mL)
was added. The solution was washed with NaHCO3 (saturated
solution, 2 ¥ 20 mL), water (2 ¥ 20 mL), dried over MgSO4, filtered
and concentrated under reduced pressure to give a brown solid.
This brown solid was purified by column chromatography (neutral
alumina, dichloromethane) to afford the desired product as a white
powder. Further purification involved dissolving in a minimum
amount of chloroform and crystallising by slow diffusion of diethyl
ether, precipitating fine colourless crystals (0.52 g, 93%). M.p. 185–
188 ◦C.
Tetramer 10. All hydrogen atoms were placed in calculated
positions and refined with riding constraints and isotropic dis-
placement parameters fixed at 1.2¥ or 1.5¥ their parent carbons
(for sp2 and sp3 carbons respectively). The bond length of
one C(sp3)–C(sp3) in a partially disordered hexane solvate was
˚
X-Ray crystallography
restrained (DFIX) to a target value of 1.53(1) A.
Crystals were inspected under a binocular microscope fitted with
a polarising attachment. Suitable crystals were then coated with
Hexamer 11. Aromatic hydrogens were placed in calculated
positions and refined with riding constraints and isotropic
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Table 2 Crystal data and refinement parameters for the dimer 8, trimer 9, tetramer 10 and hexamer 11
Complex
Dimer
Trimer·1.2CHCl3
Tetramer·2CHCl3·C6H14
Hexamer·4C4H10O
Empirical formula
Formula weight/g mol-1
Temperature/K
Wavelength/A
Crystal system
C30H30N4
450.61
100(2)
0.71073
Orthorhombic
C46.2H51.2Cl3.6N6
818.15
100(2)
C65H75Cl6N8
1181.03
100(2)
0.71073
Triclinic
¯
P1
a = 13.395(3)
b = 13.920(3)
c = 18.238(4)
a = 82.99(3)◦
b = 74.76(3)◦
g = 63.01(3)◦
2923.8(14)
2 (1)
C106H138N12O4
1644.28
100(2)
1.54178
Monoclinic
˚
0.71073
Tetragonal
¯
Space group
Unit cell dimensions/A
Pna21
P421c
P21/c
˚
a = 11.836(2)
b = 16.170(3)
c = 12.621(3)
a = 90◦
a = 30.277(4)
b = 30.277(4)
c = 25.361(5)
a = 90◦
a = 8.6359(7)
b = 40.315(8)
c = 13.478(3)
a = 90◦
b = 90◦
b = 90◦
b = 107.58(1)◦
g = 90◦
g = 90◦
g = 90◦
3
˚
Volume/A
2415.5(8)
4 (1)
23248(7)
4473.4(13)
2 (0.5)
Z (Z¢)
20 (2.5)
1.169
0.269
8632
Density (calculated)/mg m-3
Absorption coefficient/mm-1
F(000)
1.239
0.074
968
1.342
0.343
1246
1.221
0.577
1780
Crystal size/mm
q range for data collection
Index ranges
0.3 ¥ 0.1 ¥ 0.1
2.05–27.48◦
-14 ≤ h ≤ 15
-13 ≤ k ≤ 20
-16 ≤ l ≤ 15
16500
5171 [Rint = 0.0565]
5171/1/443
S = 0.944
0.2 ¥ 0.2 ¥ 0.15
1.05–22.50◦
-32≤ h ≤ 32
-24 ≤ k ≤ 32
-27 ≤ l ≤ 23
88405
15215 [Rint = 0.0930]
15215/972/511
S = 1.629
0.4 ¥ 0.3 ¥ 0.3
2.32–27.44◦
-15 ≤ h ≤ 15
-16 ≤ k ≤ 16
-21 ≤ l ≤ 21
26699
10253 [Rint = 0.0201]
10253/1/723
S = 1.008
0.3 ¥ 0.2 ¥ 0.05
2.19–70.48◦
-10 ≤ h ≤ 10
-47 ≤ k ≤ 49
-16 ≤ l ≤ 16
35123
8399 [Rint = 0.0337]
8399/0/755
S = 0.956
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
R indices [for reflections
with I > 2s(I)]a,b
R1 = 0.0428, wR2 = 0.0854 R1 = 0.1808, wR2 = 0.4508 R1 = 0.0791, wR2 = 0.2112 R1 = 0.0367, wR2 = 0.0960
R1 = 0.0487, wR2 = 0.0875 R1 = 0.2136, wR2 = 0.4742 R1 = 0.0922, wR2 = 0.2168 R1 = 0.0429, wR2 = 0.0987
R indices (for all data)a,b
Weighting schemeb
a = 0.0395, b = 0.0000
0.214 and -0.233
a = 0.2000, b = 0.0000
0.616 and -0.490
a = 0.0895, b = 10.8805
1.455 and -0.789
a = 0.0701, b = 0.0000
0.267 and -0.242
-3
˚
Largest diff. peak and hole/e A
a Structure was refined on F2o using all data; the value of R1 is given for comparison with older refinements based on Fo with a typical threshold of
ꢀ
ꢀ
1
2
2
2
2
F ≥4s(F). b wR2 = [ [w(Fo2 - Fc2)2]/ w(Fo) ] where w-1 = [s (F2o) + (aP)2 + bP] and P = [max(Fo2 , 0) + 2F2o]/3.
displacement parameters fixed at 1.2¥ their parent carbons. All
aliphatic hydrogens were located in the Fourier difference map
and refined without constraints.
7 A. S. Morkovnik, A. N. Suslov and B. A. Tertov, Zh. O. Khim., 1991,
61, 471–478.
8 S. F. Nelsen, E. L. Clennan, L. Echegoyan and L. A. Grezzo, J. Org.
Chem., 1978, 43, 2621.
9 S. F. Nelsen, L. A. Grezzo and W. C. Hollinsed, J. Org. Chem., 1981,
46, 283.
10 F. A. Neugebauer, B. Funk and H. A. Staab, Tetrahedron Lett., 1994,
35, 4755.
Electrochemistry
11 S. M. Silence, J. C. Scott, J. J. Stankus, W. E. Moerner, C. R. Moylan,
G. C. Bjorklund and R. J. Twieg, J. Phys. Chem., 1995, 99, 4096.
12 R. W. Alder, C. M. Maunder and A. G. Orpen, Tetrahedron Lett., 1990,
31, 6717–6720.
13 H. H. Wasserman and M. S. Baird, Tetrahedron Lett., 1970, 11, 1729.
14 H. Stetter and A. Mertens, Liebigs Ann. Chem., 1981, 1981, 1550.
15 H. Stetter and H. J. Bender, Chem. Ber., 1981, 114, 1226.
16 H. Stetter, W. Basse, H. Kuhlmann, A. Landscheidt and W. Schlenker,
Chem. Ber., 1977, 110, 1007–1019.
Cyclic voltammograms were recorded on an Autolab potentiostat
(Ecochemie, Netherlands) operating in three-electrode mode. A
platinum or ITO working electrode, a saturated calomel reference
electrode and a platinum gauze counter electrode were immersed
in dichloromethane solutions containing 5 ¥ 10-3 mol dm-3 of
oligomer and 0.1 mol dm-3 tetra-n-butylammonium perchlorate.
17 G. Dujardin and J. M. Poirier, Bull. Soc. Chim. Fr., 1994, 131, 900–909.
18 J. M. Poirier and G. Dujardin, Heterocycles, 1987, 25, 399–407.
19 E. Wenkert, M. Guo, R. Lavilla, B. Porter, K. Ramachandran and J. H.
Sheu, J. Org. Chem., 1990, 55, 6203–6214.
20 T. Barth and F. A. Neugebauer, J. Org. Chem., 1995, 60, 5401–5406.
21 T. Barth, C. Krieger, H. A. Staab and F. A. Neugebauer, J. Chem. Soc.,
Chem. Commun., 1993, 1129.
22 T. Barth, C. Krieger, F. A. Neugebauer and H. A. Staab, Angew. Chem.,
Int. Ed. Engl., 1991, 30, 1028.
23 V. A. Ozeryanskii and A. F. Pozharskii, Russ. Chem. Bull., 2003, 52,
271.
References
1 K. Geramita, J. McBee, Y. Tao, R. A. Segalman and T. D. Tilley, Chem.
Commun., 2008, 5107.
2 G. R. Hutchison, M. A. Ratner and T. J. Marks, J. Am. Chem. Soc.,
2005, 127, 16866.
3 A. P. Kulkarni, C. J. Tonzola, A. Babel and S. A. Jenekhe, Chem. Mater.,
2004, 16, 4556.
4 R. W. Alder, K. R. Anderson, P. A. Benjes, C. P. Butts, P. A. Koutentis
and A. G. Orpen, Chem. Commun., 1998, 309.
24 Spartan ‘06, Wavefunction Inc., Irvine, CA, USA, 2006.
25 X. G. Li, M. R. Huang, W. Duan and Y. L. Yang, Chem. Rev., 2002,
102, 2925.
26 J. W. Lee, D. S. Park, Y. B. Shim and S. M. Park, J. Electrochem. Soc.,
1992, 139, 3507.
5 R. W. Alder, P. R. Allen, K. R. Anderson, C. P. Butts, E. Khosravi, A.
Martin, C. M. Maunder, A. G. Orpen and C. B. St. Pourcain, J. Chem.
Soc., Perkin Trans. 2, 1998, 2083.
6 A. S. Morkovnik, A. N. Suslov, E. S. Klimov, Z. S. Morkovnik and
O. Y. Okhlobystin, Khim. Geterotsikl. Soedin., 1995, 973–979.
2714 | Org. Biomol. Chem., 2009, 7, 2704–2715
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
27 L. H. Gade, C. H. Galka, K. W. Hellmann, R. M. Williams, L. De
Cola, I. J. Scowen and M. McPartlin, Chem.–Eur. J., 2002, 8, 3732.
28 J. S. Whitehurst, J. Chem. Soc., 1951, 226–230.
29 V. A. Ozeryanskii, E. A. Filatova, V. I. Sorokin and A. F. Pozharskii,
Russ. Chem. Bull., 2001, 50, 846.
30 P. Maslak, A. Chopra, C. R. Moylan, R. Wortmann, S. Lebus, A. L.
Rheingold and G. P. A. Yap, J. Am. Chem. Soc., 1996, 118, 1471.
31 SMART Diffractometer Control Software, Bruker Analytical X-ray
Instruments Inc., Madison, WI, 1998.
32 SAINT Integration Software, Siemens Analytical X-ray Instruments
Inc., Madison, WI, 1994.
33 SHELXTL Program System, Vers. 5.1, Bruker Analytical X-ray
Instruments Inc., Madison, WI, 1998.
34 G. M. Sheldrick, SADABS: A Program for Absorption Correction with
the Siemens SMART System, University of Go¨ttingen, Germany, 1996.
35 A. L. Spek, Acta Crystallogr., Sect. A, 1990, 46, C-34; A. L. Spek,
PLATON—A Multipurpose Crystallographic Tool, Utrecht University,
Utrecht, The Netherlands, 2003.
This journal is
The Royal Society of Chemistry 2009
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