Synthesis and preliminary physical properties of new neutral tetraalkoxy-substituted nickel bis(1,2-dithiolene) complexes

Article abstract of DOI:10.1039/b9nj00519f

Nineteen neutral nickel bisdiphenylethenedithiolene complexes [Ni(dpedt)₂], including seventeen new compounds, were synthesized and characterized by a new short, efficient and multigram-scale synthetic method. Preliminary physical investigations show that these complexes are electron-withdrawing materials exhibiting good thermal stability and high molecular absorption coefficient in the near-infrared spectral region. Electrochemical and optical properties of [Ni(dpedt)₂] depend strongly on the nickel bis(1,2-dithiolene) core and very slightly on the alkyl chain lengths or configurations. These highly soluble coordination compounds are potential candidates as acceptor solution-processable materials for active layers in organic electronic devices, such as field effect transistors or photovoltaic devices.

Full text of DOI:10.1039/b9nj00519f

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Synthesis and preliminary physical properties of new neutral
tetraalkoxy-substituted nickel bis(1,2-dithiolene) complexesw
ab
Thanh-Tuan Bui,ab Benedicte Garreau-de Bonneval and
´
´
Kathleen I. Moineau-Chane Ching*ab
Received (in Montpellier, France) 29th September 2009, Accepted 30th October 2009
First published as an Advance Article on the web 18th December 2009
DOI: 10.1039/b9nj00519f
Nineteen neutral nickel bisdiphenylethenedithiolene complexes [Ni(dpedt)2], including seventeen
new compounds, were synthesized and characterized by a new short, efficient and multigram-scale
synthetic method. Preliminary physical investigations show that these complexes are electron-
withdrawing materials exhibiting good thermal stability and high molecular absorption coefficient
in the near-infrared spectral region. Electrochemical and optical properties of [Ni(dpedt)2] depend
strongly on the nickel bis(1,2-dithiolene) core and very slightly on the alkyl chain lengths or
configurations. These highly soluble coordination compounds are potential candidates as acceptor
solution-processable materials for active layers in organic electronic devices, such as field effect
transistors or photovoltaic devices.
infrared (NIR) photodetectors,11 optical switching devices,12
Introduction
organic dyes,6 non linear optics,13 and organic electronics.14
Results of extensive research on metal bis(1,2-dithiolene)
complexes chemistry have been the subject of several
reviews.15 These kinds of complexes are potentially molecular
materials for organic electronic applications due to their
high molecular absorption coefficients in the NIR spectral
region. In this work, our interest is concentrated on
synthesizing new neutral nickel bis[1,2-bis(4-alkoxyphenyl)-
ethene-1,2-dithiolene] complexes in order to obtain room
The chemistry of neutral transition-metal (1,2-dithiolene)
complexes in the 1960’s decade started with the first report
on an authentic trisdithiolene complex by Gilbert et al.1 In
1962, Schrauzer et al.2 reported the preparation of an unusual
nickel complex, formulated as [NiS4C4Ph4], in the somewhat
esoteric reaction between Ni(CO)4, sulfur and diphenylacetylene.
This new nickel complex, quite unlike any other nickel
complex known at that time, was intensely colored (green),
diamagnetic, and volatile. This was the first authentic neutral
nickel bisdiphenylethenedithiolene [Ni(dpedt)2] reported. Later,
they reported the formation of a large number of neutral metal
complexes with diaryl and dialkyl ‘‘a,b-dithioketones’’
[MS4C4R4].3 Their methods only give low yields and are not
sufficiently general. A little later, they reported a new synthetic
method using benzoin.4 This method is still generously used
nowadays in order to prepare (a)symmetric tetra(hetero)aryl-
substituted nickel bis(1,2-dithiolene) complexes.5,6 However, it
cannot be adopted for long-chain substituted complexes,
because one cannot obtain long alkyl/alkoxy chain-substituted
benzoins by the benzoin condensation, except for dimethyl-,
dimethoxy- and tetramethoxy-benzoins. Ohta et al.7–10 over-
came this limitation and succeeded in obtaining several series
of alkyl- and alkoxy-substituted nickel bis(1,2-bisphenyl-
ethene-1,2-dithiolene) complexes by using the corresponding
benzils as the precursors. Based on the chemical reactivities
and physical properties of the nickel bis(1,2-dithiolene)
complexes, many applications were developed such as near
temperature discotic liquid crystals (DLC) for
a new
conception of multi-layer organic photovoltaic device based
on NIR absorbent DLC semiconducting materials. The use
of DLC semiconducting molecules would help increasing
the efficiency of organic photovoltaic devices due to their
high charge mobilities.16 The first discotic mesogenic neutral
nickel bis(1,2-dithiolene) complexes, which contains four
n-dodecyloxy chains (Fig. 1), was reported in 1983 by
Veber et al.17
Later, Ohta et al.8 synthesized two new homologous discotic
mesospheric complexes with n-nonyloxy and n-undecyloxy
chains (Fig. 1). In 2001, they synthesized a new series of nickel
bis(1,2-dithiolene) complexes containing 4-fold linear alkoxy
moieties and fully re-studied this family.10 They claimed
that these complexes with n Z 9 exhibit discotic liquid
a CNRS: LCC (Laboratoire de Chimie de Coordination),
205 Route de Narbonne, F-31077 Toulouse, France.
E-mail: kathleen.chane@lcc-toulouse.fr; Fax: +33561553003;
Tel: +33561333152
b
´
Universite de Toulouse (UPS, INPT, LCC), F-31077 Toulouse,
France
w Electronic supplementary information (ESI) available: 1H and 13C
NMR spectra of all nickel complexes. See DOI: 10.1039/b9nj00519f
Fig. 1 First discotic mesogenic neutral nickel bis(1,2-dithiolene)
complexes reported by Veber et al.17 and then Ohta et al.8,10
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New J. Chem., 2010, 34, 337–347 | 337

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crystalline properties. Prior to this work, the lowest transition
temperatures reported were situated between 50 1C and 60 1C
with linear dodecyloxy and linear tetradecyloxy chains.10
The introduction of branched alkyloxy chains and the
synthesis of asymmetric complexes, i.e. complexes containing
two kinds of alkyloxy (either linear (L) or branched (B)) chains
could play an important role on the molecular packing, and
thus on the transition temperature.
after 50 h of reflux. The complete treatment of reaction
mixture after only 17 h gave a mixture of three products:
starting 1,2-diketone (E20% of starting materials), mono-
demethylation intermediate product 1b, E30% and 1a,
E30%. Example of high yield synthesis of 1b was also
reported22 but in the present work the synthesis of 1b was
not optimized. Both 1a and 1b were engaged in the next steps
for preparing long chain substituted benzils: the precursor of
1,2-dithiolene ligands.
Results and discussion
Synthesis
Based on the successful benzil method of Ohta et al.,8,10 new
synthetic pathways were developed to obtain asymmetric
compounds or new symmetric complexes. The starting
material, p-anisil, is a commercially available product. It can
be also easily prepared from 4-methoxybenzaldehyde by the
method of Wenz.18 The synthetic pathways are outlined in
Scheme 1. The list of all intermediate and final complexes is
given in Table 1. As depicted in Scheme 1, the final neutral
complexes are achieved from the benzil precursors 3a–3s.
The transformation of 3a–3s into nickel bis(1,2-dithiolene)
complexes is well known as a ‘‘one-pot’’ procedure.4,19 The
thionating reaction of the a-diketone 3 is performed by
P4S10 in boiling dioxane leading to thiophosphate ester
intermediates.4 Recently Arumugam et al.20 demonstrated
the preparation and isolation of stable thiophosphate ester
consisting in the protected forms of 1,2-dithiolene ligands.
According to our synthesis pathway, this thiophosphate ester
is not isolated but directly hydrolyzed in the reaction medium.
The hydrolysis followed by adding nickel salt in air condition
gives neutral products [Ni(dpedt)2] with quite good yields after
purification by repeated processes of precipitation and column
chromatography. By convention, all [Ni(dpedt)2] derivatives in
the present work are presented as trans configuration as the
exact configuration of nickel complexes are not elucidated. In
order to obtain the long alkoxy chain-substituted benzil
derivatives 3b–3s, we started from p-anisil 3a. By removing
one methyl-group of 3a in hydrobromic acid we obtained the
phenol derivative 1b. We were then able to graft another linear
or branched alkyl chain to get asymmetric benzils 3b–3f. If
both methoxy groups are removed, two free phenol functions
are available for chemical modification. The introduction of
two-fold alkyl chain yielded to symmetric benzils 3g–3m. At
this stage, it was possible to graft two different alkyl chains on
1a by successive substitutions. The monoalkoxy-substituted
intermediates 2n–2p were systematically purified before the
second alkyl chains were introduced. All branched alkyl chains
were used as racemic mixtures. The 4,40-dihydroxybenzil 1a
was prepared in big quantities from 3a. The demethylation
reaction was performed by a boiling mixture of concentrated
hydrobromide acid and glacial acetic acid according to the
literature.21 In this reaction conditions, the conversion of
4,40-dimethoxybenzil to a-diketone 1a strongly depends on
the reaction times and the quantity of starting material
(the longer the reflux time is, the higher the conversation rate is).
We started from 26 g of 3a in 550 ml of acid mixture and the
desired product 1a was obtained with nearly quantitative yield
Scheme 1 Synthetic pathways of neutral nickel bis(1,2-dithiolene)
complexes. Reagents and conditions: (a) HBr 48%, glacial
CH3COOH, reflux; (b) RBr (0.9 equiv.), K2CO3 (0.9 equiv.), DMF,
90 1C, 1 h; (c) RBr (1.2 equiv.), K2CO3 (1.5 equiv.), DMF, 90 1C; (d)
ROH (1.2 equiv.), DEAD (1.2 equiv.), PPh3 (1.2 equiv.), THF, 0 1C
then 1 h at R.T.; (e) RBr (2.4 equiv.), K2CO3 (3.0 equiv.), DMF, 90 1C;
(f) ROH (2.4 equiv.), DEAD (2.4 equiv.), PPh3 (2.4 equiv.), THF, 0 1C
then 1 h at R.T.; (g) P4S10 (2.2 equiv.), dioxane, reflux 5 h then
NiCl2.6H2O (0.55 equiv.), H2O, reflux 2 h.
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338 | New J. Chem., 2010, 34, 337–347

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Table 1 Intermediate and final synthesized compounds. All branched alkyl chains are racemic mixture and yields (%) are listed in bracket. 3h was
isolated from the synthesis of 2p and 3a is a commercial product. Melting points (1C) are determined from DSC diagrams
R
R0
1
2
3
Nickel complexes
Yield/color/Mp
H
Methyl
2-Ethylhexyl
n-Decyl
n-Dodecyl
Methyl
n-Decyl
2-Ethylhexyl
3,7-Dimethyloctyl
2-Butyloctyl
2-Hexyldecyl
2-Ethylhexyl
n-Dodecyl
3,7-Dimethyloctyl
2-Butyloctyl
2-Hexyldecyl
2-Octyldodecyl
2-Decyltetradecyl
2-Ethylhexyl
n-Decyl
H
H
H
H
H
Methyl
Methyl
Methyl
Methyl
Methyl
Methyl
2-Ethylhexyl
n-Dodecyl
3,7-Dimethyloctyl
2-Butyloctyl
2-Hexyldecyl
2-Octyldodecyl
2-Decyltetradecyl
n-Decyl
3,7-Dimethyloctyl
n-Tetradecyl
n-Undecyl
2-Butyloctyl
3,7-Dimethyloctyl
1a (96)
1b (28)
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
2n (41)
2o (57)
2p (46)
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
3a
—
—
—
—
[Ni((4-OC1,40-OC1)dpedt)2]
[Ni((4-OC1,40-OC10L)dpedt)2]
[Ni((4-OC1,40-OC8B)dpedt)2]
[Ni((4-OC1,40-OC10B)dpedt)2]
[Ni((4-OC1,40-OC12B)dpedt)2]
[Ni((4-OC1,40-OC16B)dpedt)2]
[Ni((4-OC8B,40-OC8B)dpedt)2]
[Ni((4-OC12L,40-OC12L)dpedt)2]
[Ni((4-OC10B,40-OC10B)dpedt)2]
[Ni((4-OC12B,40-OC12B)dpedt)2]
[Ni((4-OC16B,40-OC16B)dpedt)2]
[Ni((4-OC20B,40-OC20B)dpedt)2]
[Ni((4-OC24B,40-OC24B)dpedt)2]
[Ni((4-OC10L,40-OC8B)dpedt)2]
[Ni((4-OC10L,40-OC10B)dpedt)2]
[Ni((4-OC12L,40-OC14L)dpedt)2]
[Ni((4-OC12L,40-OC11L)dpedt)2]
[Ni((4-OC12L,40-OC12B)dpedt)2]
[Ni((4-OC12L,40-OC10B)dpedt)2]
18/black/nd
3b (95)
3c (97)
3d (84)
3e (77)
3f (96)
3g (70)
3h
3i (78)
3j (90)
3k (69)
3l (75)
3m (82)
3n (69)
3o (91)
3p (99)
3q (80)
3r (100)
3s (95)
51/black/147.3
45/brown/199.1
53/black/170.3
49/black/154.8
50/black/147.4
47/brown/163.7
48/brown/168.8
59/black/129.9
51/black/103.2
49/black/-
43/black/-
57/black/-
—
—
—
—
—
—
73/black/153.2
59/black/158.5
52/brown/163.7
68/brown/171.9
71/black/99.0
55/brown/149.7
n-Dodecyl
n-Dodecyl
n-Dodecyl
n-Dodecyl
Synthesis of symmetric 4,40-dialkoxybenzils (3g–3m)
resulting in 3n–3s. The dialkoxy-substituted benzils containing
one methyl chain 3b–3f were synthesized from 1b in similar
conditions.
The symmetric 4,40-dialkyloxybenzils 3g–3m were synthesized
by grafting alkyl chains on the phenol function of 1a. Two
different methods were used, depending on the commercial
availability of alkyl chains as halogenated alkanes or alcoholic
compounds. In the first case, the classical nucleophilic
substitution reaction gave 3g in high yield by heating the
mixture of 1a and large excess of 2-ethylhexylbromide and a
Lewis base (K2CO3) in DMF.
In the later case, the Mitsunobu’s method23 was applicable
leading to 3i–3m. The Mitsunobu reaction is very efficient in
mild experimental conditions (ambient temperature) and an
easy work-up reaction. This allows the conversion of primary
and secondary alcohols to esters, phenyl ethers, thioethers and
various other compounds with high yields. We are able to
graft a large choice of alkyl chains in one step, particularly
branched ones that are often available as primary or
secondary alcohols.
In comparison with other methods of synthesis of
asymmetrical long alkoxy-substituted benzils,25 this method
presents some advantages. It uses common intermediates such
as 1a and 1b and allows synthesizing many asymmetric benzils
without any difficulty. Moreover, the alkyl chains are
introduced in the last steps starting from either halogenated
alkanes or alcohols that allow numerous alkyl chains
combinations.
All of the synthesized compounds were identified by 1H and
13C NMR spectra. The elemental analyses and mass spectro-
metry analyses gave complementary confirmations. The
analytical data of all [Ni(dpedt)2] such as visual colors, melting
points, elemental analysis results, mass studies are summarized
in Table 1 and the experimental section. All attempts to form a
suitable crystal for single crystal X-ray diffraction analysis
failed. As observed from Table 1, the introduction of long
chains generally decreases the melting temperature of the
nickel bis(1,2-dithiolene) complexes.
Synthesis of asymmetric 4,40-dialkoxybenzils (3b–3f, 3n–3s)
The asymmetric precursors 4,40-dialkyloxybenzil 3n–3s, which
contain two different alkyl chains (different from methyl), were
synthesized from 1a. For this, the two chains were successively
introduced. The reaction of 1a with a little less than one
equivalent of alkyl bromide in short reaction time forms
monoalkoxy-substituted benzils 2n–2p with acceptable yields
(41–57%). Usually the symmetric benzils 3 were also isolated
as co-products (e.g. 4,40-dodecyloxybenzil 3h is isolated in the
synthesis of 2p in 30% yield). The quantitative conversion of
1a to 2o–2p could be realized by using a large excess of 1a as
described for a similar reaction.24 The introduction of the
second alkyl chain was performed either by nucleophilic
substitution or the Mitsunobu reaction, as described above,
1H NMR spectra of benzil derivatives and corresponding
nickel complexes are similar. Two typical spectra are gathered
1
in Fig. 2: H NMR spectra of 4-decyloxy-40-methoxybenzil
(Fig. 2b) and the corresponding nickel dithiolene complex
(Fig. 2a). As observed, the peaks corresponding to protons
Hc (triplet) and Hd (singlet) are well distinguishable, both in
the case of benzil and dithiolene complex. In the aromatic
region, the protons in the metal complex are shifted to higher
fields. The metal bis(1,2-dithiolene) core is less electro-
attractive than the corresponding 1,2-diketonic group. In
addition to the NMR analysis, the good cohesiveness between
the theoretical and experimental values of elemental analyses
and mass spectroscopy studies confirmed the purity of the
ꢀc
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Fig.
4
DSC trace of [Ni((4-OC8B,40-OC8B)dpedt)2], scan rate:
1
Fig. 2 Partial H NMR spectra of (b) 4-decyloxy-40-methoxybenzil
10 1C minꢁ1
.
3d and (a) the corresponding nickel complex [Ni((4-OC1,40-OC10L)-
dpedt)2]. The peaks of CD2Cl2 solvent have a star.
The phase transition behaviors of [Ni(dpedt)2] are studied
by differential scanning calorimetry (DSC), polarized optical
microscopy (POM) and temperature-dependence powder
X-rays diffraction. Fig. 4 shows the phase transition of the
[Ni((4-OC8B,40-OC8B)dpedt)2]. This complex was obtained as
a brown powder. On heating, it melts into an isotropic liquid at
162.8 1C and on cooling down, the crystallization peak appears
at 109.3 1C. This phase behavior of [Ni((4-OC8B,40-OC8B)dpedt)2]
is much simpler than its analogue’s: the tetraoctyloxy-
substituted [Ni(dpedt)2],10 which contains four linear octyl
chains. Its lower melting point is due to the highly steric bulky
effect of the 2-ethylhexyl chain.
synthesized products. It is noteworthy that all nickel
complexes were obtained from repeated precipitation
processes and finally purified by silica-gel column chromato-
graphy. Table 1 also summarizes the visual aspects of all
[Ni(dpedt)2]. The colors of some compounds appear to
be different. Six of them are brown and thirteen others are
black/dark-green.
Preliminary physical investigations
In order to envisage their use as active materials in organic
electronic devices, the physical properties of these complexes
have to be characterized. Currently, advanced studies are
being carried out. Only the preliminary physical properties
are given and discussed in this present paper. The typical
results on [Ni((4-OC8B,40-OC8B)dpedt)2] are presented.
Optical and electrochemical properties
The electrochemical and optical properties of the synthesized
compounds were studied by cyclic voltammetry and UV-VIS-NIR
absorption spectroscopy. The cyclic voltammogram of
[Ni((4-OC8B,40-OC8B)dpedt)2] in dichloromethane is shown
in Fig. 5. Three pairs of redox waves are observed. In
reduction, two successive near –0.1 and –0.8 V vs. SCE waves
correspond to 1- and 2-electron reduction (respectively, couple
2 and couple 1).27 In oxidation, the first 1-electron oxidation
is observed near 1 V vs. SCE (Couple 3).27 The solution
absorption spectra in the UV-VIS-NIR region of
[Ni((4-OC8B,40-OC8B)dpedt)2] is presented in Table 2. The
complex shows a maximum absorption peak in the near-
infrared spectral region, which can be attributed to a p–p*
transition of the nickel bis(1,2-dithiolene) core. All
potentials are determined in CH2Cl2 solution using a Pt
electrode except for [Ni((4-OC12B,40-OC12B)dpedt)2] and
[Ni((4-OC24B,40-OC24B)dpedt)2]: for these two compounds,
reproducible results are obtained using a glassy carbon electrode.
From this table, it appears that the reduction potentials of
these complexes change very slightly depending on the alkoxy
chain length and configuration. These experimental values are
in good agreement with values reported in the literature.10 The
values, –0.06 to –0.12 V vs. SCE, observed for these complexes
are less positive than that of the core complex, the [Ni(dpedt)2]
Thermal behaviors
The highly thermal stability of the targeted compounds is
required to envisage their use as active materials in organic
electronic devices (e.g. OPV, OFET). The thermal analysis
studies show that neutral nickel bis(1,2-dithiolene) complexes
are thermally stable until 300 1C, as observed in Fig. 3
for compound [Ni((4-OC8B,40-OC8B)dpedt)2]. At higher
temperature, the decomposition of the product is observed.
This thermal behavior is in good accordance with data
reported in the literature.26
(E1/2
= 0.03 V vs. SCE in CH2Cl2).10 This difference is
red
attributable to the mesomeric electron donating effect of the
alkoxy substituents. As observed from Table 2, the values of
lmax change only slightly from 924–936 nm. The nature of the
alkyl chains does not influence the optical properties of
Fig. 3 Thermal analysis trace of [Ni((4-OC8B,40-OC8B)dpedt)2].
ꢀc
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or optical properties. The same result and claim were reported
for the first time by Ohta et al. in 19919 and then in 2001.10
Conclusion
Nineteen [Ni(dpedt)2], including seventeen new compounds,
were synthesized by new short and efficient synthetic
pathways. The synthesis of two common intermediates
4,40-dihydroxybenzil 1a and 4-hydroxy-40-methoxybenzil 1b
and the introduction of alkyl chains in the later steps allows us
to synthesize easily a series of [Ni(dpedt)2]. The Mitsunobu
reaction has proven to be a very efficient method to prepare
various alkoxy-substituted aromatic compounds from phenol
derivatives. The alternative choice of either the classical
nucleophilic substitution reaction or the Mitsunobu reaction
gives us a large source of alkyl chains, either from alkyl halides
or from primary or secondary alcohols. The complete
investigation of mesomorphic properties of this [Ni(dpedt)2]
series and advanced studies by electrochemical and optical
methods are being carried out and will be fully discussed in a
separate article.
Fig. 5 Cyclic voltammogram of [Ni((4-OC8B,40-OC8B)dpedt)2] in
CH2Cl2 containing 0.1 mol Lꢁ1 (Bu4N)PF6 as an electrolyte by using
Pt metal working and counter electrodes and a standard SCE reference
electrode at 25 1C (scan rate 0.1 V sꢁ1).
Table 2 First half-wave reduction potentials and electronic absorption
data for [Ni(dpedt)2]
Nickel complexes
E1/2/Va max/nmb e/L molꢁ1cmꢁ1
l
[Ni((4-OC1,40-OC1)dpedt)2]
[Ni((4-OC1,40-OC10L)dpedt)2]
[Ni((4-OC1,40-OC8B)dpedt)2]
[Ni((4-OC1,40-OC10B)dpedt)2]
[Ni((4-OC1,40-OC12B)dpedt)2]
[Ni((4-OC1,40-OC16B)dpedt)2]
[Ni((4-OC8B,40-OC8B)dpedt)2]
[Ni((4-OC12L,40-OC12L)dpedt)2] –0.10
[Ni((4-OC10B,40-OC10B)dpedt)2] –0.10
[Ni((4-OC12B,40-OC12B)dpedt)2] –0.11
[Ni((4-OC16B,40-OC16B)dpedt)2] –0.12
[Ni((4-OC20B,40-OC20B)dpedt)2] –0.09
[Ni((4-OC24B,40-OC24B)dpedt)2] –0.11
[Ni((4-OC10L,40-OC8B)dpedt)2] –0.10
[Ni((4-OC10L,40-OC10B)dpedt)2] –0.06
[Ni((4-OC12L,40-OC14L)dpedt)2] –0.11
[Ni((4-OC12L,40-OC11L)dpedt)2] –0.11
[Ni((4-OC12L,40-OC12B)dpedt)2] –0.12
[Ni((4-OC12L,40-OC10B)dpedt)2] –0.12
–0.09
–0.09
–0.09
–0.09
–0.10
–0.08
–0.10
924
929
931
928
931
929
934
934
933
935
936
935
935
934
933
933
933
934
933
47 000
50 000
38 000
44 000
54 000
51 000
47 000
49 000
50 000
43 000
54 000
51 000
54 000
47 000
51 000
48 000
51 000
51 000
52 000
Experimental
General remarks
All used chemicals and solvents were purchased from chemical
companies and used as received, unless otherwise mentioned.
All reactions were realized under ambient atmosphere unless
special indication. 1H and 13C NMR experiments were
recorded in the listed deuterated solvents (internal standard)
on a 4 Bruker Spectrometers (ARX 250, DPX 300, Avance 300
and Avance 400). Purification of product was performed by
column chromatography on silica gel from Merck with a grain
size of 0.04–0.063 mm (flash silica gel, Geduran Si 60) with
analytically pure solvents. For analytical thin layer chromato-
graphy (TLC), silica gel coated substrates ‘‘60 F254’’ from
Merck were used and compounds were detected by fluores-
cence quenching at 254 nm, self-fluorescence at 365 nm.
Melting points were determined by DSC thermograms, which
were obtained on a DSC 204 NETZSCH system using 2–5 mg
a
Volts vs. SCE in CH2Cl2 using platinum metal electrode, except for
[Ni((4-OC12B,40-OC12B)dpedt)2] and [Ni((4-OC24B,40-OC24B)dpedt)2]
using Glassy carbon electrode. Cyclic voltammogram of
[Ni((4-OC8B,40-OC8B)dpedt)2] in CH2Cl2 containing 0.1 mol Lꢁ1
(Bu4N)PF6 as an electrolyte and a standard SCE reference electrode
b
at 25 1C (scan rate 0.1 V sꢁ1). In CH2Cl2 solution.
samples in 30 ml sample pans and a scan rate of 10 1C minꢁ1
.
DH is calculated in J gꢁ1. Mass analyses were performed at
the MS Service at the Paul Sabatier University. Elemental
analyses (C, H, S, Ni) were carried out at the CNRS Central
Analyses Service in Lyon. UV-VIS-NIR absorption spectra
were recorded on two spectrometers Perkin-Elmer Lambda
35 and Perkin-Elmer GX 2000. Voltammetric measurements
were carried out with a potentiostat Autolab PGSTAT100
controlled by GPES 4.09 software. Experiments were
performed at room temperature in a homemade airtight
three-electrode cell connected to a vacuum/argon line. The
reference electrode consisted in a saturated calomel electrode
(SCE) separated from the solution by a bridge compartment.
The counter electrode was a platinum wire of ca. 1 cm2
apparent surfaces. The working electrode was a Pt microdisk
(0.5 mm diameter) or a glassy carbon (1 mm diameter).
The supporting electrolyte (nBu4N)[PF6] (Fluka, 99% electro-
chemical grade) was used as received and simply degassed
[Ni(dpedt)2]. In addition, the high values of molecular absorp-
tion coefficient e range from 38 000 to 54 000 Mꢁ1 cmꢁ1
demonstrating that the [Ni(dpedt)2] are efficient NIR absorbent
materials. The full results of cyclic voltammetry and electronic
absorption spectroscopy will be used further to estimate the
optical and electrochemical bandgaps, electron affinities (Ea)
and ionization potentials (Ip) of all [Ni(dpedt)2]. From the first
results of electrochemical and electronic absorption measure-
ments, one can conclude that the nature of alkyl chains do not
influence significantly electrochemical or optical properties in
this [Ni(dpedt)2] series. This could be a very interesting result
because the mesomorphic property of the complexes depends
on the alkoxy chain length and configuration, whereas the
reduction potential and optical absorption do not. That is to
say, we can change the peripheral chain length to obtain the
mesomorphic properties without changing the electrochemical
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under argon. CH2Cl2 was freshly distilled over CaH2 prior
to use. The solutions used during the electrochemical
studies were typically 10ꢁ3 mol Lꢁ1 in complex compound
and 0.1 mol Lꢁ1 in supporting electrolyte. Before each
measurement, the solutions were degassed by bubbling Ar
and the working electrode was polished with a polishing
machine (Presi P230).
4-Methoxy-40-(2-ethylhexyloxy)benzil (3c). Yellowish oil
(1.4 g, 97%). dH(300 MHz, CD2Cl2) 7.96 (4 H, m, aromatic H),
7.03 (4 H, m, aromatic H), 3.98 (2 H, d, J = 5.7 Hz, –OCH2–),
3.92 (3 H, s, –OCH3), 1.79 (1 H, m, –CH2–CH–), 1.53–1.35
(8 H, m), 0.97 (6 H, t, J = 7.5 Hz, –CH3). dC(75 MHz,
CD2Cl2) 193.60, 193.52, 164.94, 164.84, 132.17, 132.10, 126.26,
125.92, 114.72, 114.28, 70.99, 55.68, 39.24, 30.37, 28.99, 23.75,
23.00, 13.81, 10.82.
4,40-Dihydroxybenzil (1a). 4,40-Dimethoxybenzil (26 g,
96.2 mmol) was heated to reflux for 50 h in a mixture of
aqueous HBr (48%) and glacial acetic acid (550 mL, 50/50).
The reaction mixture was cooled by a bath of ice-water and the
yellow precipitate was collected by filtration. The filtrate was
then extracted several times with ethyl acetate. The organic
phases and the yellow precipitate were combined, washed
several times with water, dried with MgSO4 and the solvent
was removed under reduced pressure. The residue was purified
by column chromatography (CH2Cl2/acetone: 85/15) giving 1a
as pure yellowish solid (22.45 g, 96%). dH(250 MHz, CD3OD)
7.82 (4 H, d, J = 9.0 Hz, aromatic H), 6.91 (4 H, d, J =
9.0 Hz, aromatic H), 4.92 (2 H, br s, phenol H). dC(75 MHz,
CD3OD): 194.26, 164.09, 132.17, 124.89, 115.51. HRMS(CI):
found 243.0669, [M + H]+ requires 243.0657.
4-Decyloxy-40-(2-ethylhexyloxy)benzil (3n). Yellow oil
(0.54 g, 69%). dH(250 MHz, CD2Cl2) 7.96 (4 H, dd, J =
1.75–7.0 Hz, aromatic H), 7.02 (4 H, m, aromatic H), 4.09
(2 H, t, J = 6.5 Hz, –OCH2CH2–), 4.00 (2 H, d, J = 5.75 Hz,
–OCH2CH–), 1.87–1.77 (3 H, m), 1.51–1.33 (22 H, m),
1.00–0.90 (9 H, m, –CH3). dC(62.5 MHz, CD2Cl2) 193.60,
164.82, 164.60, 132.17, 126.01, 125.97, 114.70, 71.01, 68.61,
39.27, 31.91, 30.40, 29.55, 29.32, 29.02, 25.90, 23.77, 23.02,
22.69, 13.88, 13.82, 10.84.
4-Dodecyloxy-40-tetradecyloxybenzil (3p). Yellow solid
(1.17 g, 99%). dH(250 MHz, CD2Cl2) 7.96 (4 H, m, aromatic H),
7.03 (4 H, m, aromatic H), 4.11 (4 H, t, J = 6.5 Hz, –OCH2–),
1.87–1.32 (44 H, m,–CH2–), 0.95 (6 H, t, J = 6.3 Hz, –CH3).
dC(62.5 MHz, CD2Cl2) 193.57, 164.59, 161.06, 132.17, 126.00,
114.68, 68.60, 64.01, 31.92, 29.64, 29.57, 29.54, 29.50, 29.34,
29.31, 29.19, 29.00, 28.53, 25.88, 25.80, 22.68, 13.87.
4-Hydroxy-40-methoxybenzil (1b). As described for the
synthesis of 1a but the reflux time was decreased to 17 h.
Complete workup gave a mixture of three products: 4,40-
dimethoxybenzil (18% of starting material), 1a (yellowish
solid, 33%) and 1b (yellow solid, 28%). dH(250 MHz,
(CD3)2CO) 9.58 (1 H, s, phenol H), 7.93 (2 H, d, J =
9.0 Hz, aromatic H), 7.87 (2 H, d, J = 9.0 Hz, aromatic H),
7.13 (2 H, d, J = 9.0 Hz, aromatic H), 7.03 (2 H, d, J =
9.0 Hz, aromatic H), 3.94 (3 H, s, –OCH3). dC(62.5 MHz,
(CD3)2CO) 193.46, 165.04, 163.51, 132.30, 131.94, 126.29,
125.45, 115.95, 114.47, 55.31. HRMS(CI): found 257.0826,
[M + H]+ requires 257.0814.
4-Dodecyloxy-40-undecyloxybenzil (3q). Yellowish solid
(1.1 g, 80%). dH(300 MHz, CD2Cl2) 7.96 (4 H, dt, J =
9.6–2.7 Hz, aromatic H), 7.03 (4 H, dt, J = 9.6–2.7 Hz,
aromatic H), 4.08 (4 H, t, J = 6.6 Hz, –OCH2–), 1.84 (4 H, m,
–OCH2CH2–), 1.51–1.31 (34 H, m), 0.92 (6 H, t, J = 6.3 Hz,
–CH3). dC(75 MHz, CD2Cl2) 193.57, 164.59, 132.17, 125.99,
114.69, 68.60, 66.75, 31.93, 29.59, 29.55, 29.33, 29.01, 25.90,
22.70, 13.89. HRMS(CI): found 565.4244, [M + H]+ requires
565.4257.
General procedure for the synthesis of benzils 3d, 3e, 3f, 3o, 3r, 3s
A THF (50 mL) solution of 4-hydroxy-40-methoxy benzil
(1.5 g, 5.85 mmol), PPh3 (1.85 g, 7.02 mmol), and alcohol
(7.02 mmol) were cooled to 0 1C. To the solution was
added diethyl azodicarboxylate in toluene solution (3.2 mL,
7.02 mmol, 40% w/v), the mixture was kept at that
temperature for 1 h and then was allowed to warm to room
temperature and stirred for 1 h. The reaction mixture was
then evaporated. After addition of 300 mL of hexane, the
mixture was filtered. The filtrate was evaporated, and the
residue was purified by silica gel column chromatography
(hexane/CH2Cl2 50/50)
General procedure for the synthesis of benzils 3b, 3c, 3n, 3p, 3q
A mixture of 1b (for 3b–3c) or 2n–2p (for 3n, 3o, 3p, 3q)
(3.9 mmol), alkyl bromide (5.9 mmol), and powdered
potassium carbonate (1.1 g, 7.8 mmol) was stirred in DMF
(25 mL) at 90 1C. The reaction was monitored by TLC
(hexane/CH2Cl2 50/50). Upon cooling to room temperature,
the reaction was quenched by adding water and the resulting
mixture was extracted by CH2Cl2. The organic phases were
combined, rinsed several time by water, dried over anhydrous
magnesium sulfate and concentrated under reduced pressure
resulting in the crude product which was purified by silica gel
column chromatography (hexane/CH2Cl2 50/50).
4-(3,7-Dimethyloctyloxy)-40-methoxybenzil (3d). Yellow oil
(1.95 g, 84%). dH(250 MHz, CD2Cl2) 7.96 (4 H, m, aromatic H),
7.03 (4 H, m, aromatic H), 4.13 (2 H, t, J = 6.6 Hz, –OCH2–),
3.93 (3 H, s, –OCH3), 1.93–1.20 (10 H, m), 1.00 (3 H, d, J =
6.4 Hz, –CH3), 0.93 (6 H, d, J = 6.6 Hz, –CH3). dC(62.5 MHz,
CD2Cl2) 193.58, 193.51, 164.95, 164.60, 132.19, 126.27, 125.98,
114.73, 114.27, 66.97, 61.01, 55.70, 39.21, 37.20, 35.90, 29.83,
27.99, 24.64, 22.44, 22.34, 19.36, 13.89.
4-Decyloxy-40-methoxybenzil (3b). Yellowish solid (1.47 g,
95%). dH(300 MHz, CD2Cl2) 7.95 (4 H, m, aromatic H), 7.02
(4 H, m, aromatic H), 4.08 (2 H, t, J = 6.6 Hz, –OCH2–), 3.92
(3 H, s, –OCH3), 1.84 (2 H, m, –OCH2CH2–), 1.49–1.32
(14 H, m), 0.92 (3 H, t,
J = 6.6 Hz, –CH2CH3).
dC(75 MHz, CD2Cl2) 193.58, 193.51, 164.94, 164.61, 132.18,
126.25, 125.95, 114.69, 114.25, 68.60, 55.68, 31.89, 29.53,
29.30, 28.99, 25.88, 22.67, 13.86.
4-(2-Butyloctyloxy)-40-methoxybenzil (3e). Yellow oil (1.92 g,
77%). dH(250 MHz, CD2Cl2) 7.95 (4 H, m, aromatic H), 7.05
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(2 H, d, J = 9.0 Hz, aromatic H), 7.00 (2 H, d, J = 8.8 Hz,
aromatic H), 3.99 (2 H, d, J = 5.8 Hz, –OCH2–), 3.93 (3 H, s,
–OCH3), 1.88–0.92 (23 H, m). dC(62.5 MHz, CD2Cl2) 193.60,
193.53, 164.94, 164.86, 132.18, 126.28, 125.93, 114.74, 114.26,
71.43, 65.46, 55.69, 40.58, 37.81, 31.84, 31.23, 30.93, 29.64,
29.01, 26.75, 23.03, 22.66, 13.87, 13.83.
azodicarboxylate in toluene solution (6.8 mL, 14.9 mmol,
40% w/v), the mixture was kept at that temperature for 1 h
and then was allowed to warm to room temperature and
stirred for 1 h. The reaction mixture was then evaporated.
After addition of 300 ml of hexane, the mixture was filtered.
The filtrate was evaporated, and the residue was purified by
silica gel column chromatography (hexane/CH2Cl2 50/50)
4-(2-Hexyldecyloxy)-40-methoxybenzil (3f). Yellow oil
(2.71 g, 96%). dH(250 MHz, CD2Cl2) 7.95 (4 H, m, aromatic H),
7.05 (2 H, d, J = 9.0 Hz, aromatic H), 7.00 (2 H, d, J =
8.8 Hz, aromatic H), 3.99 (2 H, d, J = 5.8 Hz, –OCH2), 3.93
(3 H, s, –OCH3), 1.88–0.90 (31 H, m). dC(62.5 MHz, CD2Cl2)
193.6, 164.86, 132.17, 126.28, 125.91, 114.74, 114.26, 71.44,
65.47, 55.70, 40.60, 37.82, 31.91, 31.22, 29.96, 29.64, 29.56,
29.31, 26.76, 22.69, 13.88.
4,40-Di(3,7-dimethyloctyloxy)benzil (3i). Yellow oil (2.52 g,
78%). dH(300 MHz, CD2Cl2) 8.13 (4 H, d, J = 9.0 Hz,
aromatic H), 7.20 (4 H, d, J = 9.0 Hz, aromatic H), 4.31
(4 H, m, –OCH2–), 2.09–1.37 (20 H, m), 1.17 (6 H, d, J =
6.6 Hz, –CH3), 1.10 (12 H, d, J = 6.6 Hz, –CH3). dC(75 MHz,
CD2Cl2) 193.75, 164.75, 132.36, 126.18, 114.89, 67.15, 39.39,
37.37, 36.07, 31.78, 30.00, 28.17, 24.82, 22.62, 22.52,
19.54, 14.07.
4-Decyloxy-40-(3,7-dimethyloctyloxy)benzil (3o). Yellow
solid (2.45 g, 91%). dH(300 MHz, CD2Cl2) 7.96 (4 H, m,
aromatic H), 7.03 (4 H, m, aromatic H), 4.15–4.06 (4 H, m,
–OCH2), 1.86–1.19 (26 H, m), 1.00–0.90 (12 H, m, –CH3). dC
(75 MHz, CD2Cl2) 193.56, 164.58, 164.56, 132.17, 126.00,
114.69, 68.59, 66.95, 39.19, 37.18, 35.88, 31.89, 29.80, 29.54,
29.31, 29.00, 27.97, 25.89, 24.62, 22.68, 22.43, 22.33,
19.35, 13.88.
4,40-Di(2-butyloctyloxy)benzil (3j). Yellow oil (4.3 g, 90%).
dH(250 MHz, CD2Cl2) 7.96 (4 H, dd, J = 1.8–8.8 Hz,
aromatic H), 7.03 (4 H, d, J = 8.8 Hz, aromatic H), 3.99
(4 H, d, J = 5.8 Hz, –OCH2–), 1.88–1.83 (2 H, m,
–OCH2CH–), 1.47–1.34 (32 H, m, –CH2–), 0.95–0.91 (12 H,
m, –CH3). dC(62.5 MHz, CD2Cl2) = 193.62, 164.83, 132.16,
125.98, 114.73, 71.42, 37.81, 31.84, 31.24, 30.94, 29.65, 29.01,
26.76, 23.03, 22.67, 13.87, 13.84.
4-Dodecyloxy-40-(2-butyloctyloxy)benzil (3r). Yellow solid
(1.97 g, 100%). dH(300 MHz, CD2Cl2) 7.96 (4 H, dt, J =
9.6–2.7 Hz, aromatic H), 7.03 (4 H, dt, J = 9.6–2.7 Hz,
aromatic H), 4.09 (2 H, t, J = 6.6 Hz, –OCH2CH2–), 3.98
(2 H, d, J = 6.6 Hz, –OCH2–CH), 1.86 (4 H, m), 1.51–1.31
(33 H, m), 0.94 (9 H, m, –CH3). dC(75 MHz, CD2Cl2): =
193.59, 164.83, 164.59, 132.17, 126.01, 125.95, 114.72, 114.69,
71.41, 68.60, 37.80, 31.93, 31.84, 31.23, 30.92, 29.64, 29.59,
29.55, 29.36, 29.33, 29.01, 26.75, 25.90, 23.03, 22.70, 22.67,
13.87, 13.83. HRMS(CI): found 579.4433, [M + H]+ requires
579.4413.
4,40-Di(2-hexyldecyloxy)benzil (3k). Yellow oil (3.94 g,
69%). dH(250 MHz, CD2Cl2) 7.96 (4 H, d, J = 9.0 Hz,
aromatic H), 7.04 (4 H, d, J = 9.0 Hz, aromatic H), 3.99
(4 H, d, J = 5.5 Hz, –OCH2–), 1.88–1.81 (2 H, m,
–OCH2CH–), 1.46–1.21 (48 H, m, –CH2–), 0.95–0.90
(12 H, m, –CH3). dC(62.5 MHz, CD2Cl2) 193.61, 164.83,
132.16, 125.98, 114.73, 71.44, 37.83, 31.91, 31.85, 31.61,
31.24, 29.97, 29.65, 29.57, 29.32, 26.77, 22.69, 13.88.
4,40-Di(2-octyldodecyloxy)benzil (3l). Yellow oil (5 g, 75%).
dH(250 MHz, CD2Cl2) 7.96 (4 H, d, J = 8.8 Hz, aromatic H),
7.03 (4 H, d, J = 8.8 Hz, aromatic H), 3.99 (4 H, d, J =
5.6 Hz, –OCH2–), 1.87–1.83 (2 H, m, –OCH2CH–), 1.46–1.31
(64 H, m, –CH2–), 0.95–0.90 (12 H, t, J = 5.9 Hz, –CH3).
dC(62.5 MHz, CD2Cl2) 193.60, 164.82, 132.14, 125.96, 114.72,
71.42, 37.80, 31.91, 31.20, 29.95, 29.63, 29.58, 29.55, 29.34,
29.30, 26.75, 22.68, 13.87.
Synthesis of 4,40-di(2-ethylhexyloxy)benzil (3g)
A mixture of 4,40-dihydroxybenzil (3) (3.26 g, 13.5 mmol),
alkyl bromide (40.5 mmol), potassium iodide (0.68 mmol) and
powdered potassium carbonate (54 mmol) was stirred in DMF
(80 mL) at 90 1C and the reaction was monitored by TLC.
Upon cooling to room temperature, the reaction was
quenched by adding water and the resulting mixture was
extracted by CH2Cl2. The organic phases were combined,
rinsed several times with water, dried over anhydrous magne-
sium sulfate and concentrated under reduced pressure
resulting in a crude product which was purified by silica gel
column chromatography (hexane/CH2Cl2 50/50). Yellowish
oil (4.32 g, 70%). dH(250 MHz, CD2Cl2) 7.94 (4 H, d, J =
9.0 Hz, aromatic H), 7.02 (4 H, d, J = 9.0 Hz, aromatic H),
3.99 (4 H, d, J = 5.8 Hz, OCH2CH), 1.83–1.78 (2 H, m,
OCH2CH), 1.52–1.24 (16 H, m, –CH2–), 1.01–0.93 (12 H, m,
–CH3). dC(75 MHz, CD2Cl2): 193.61, 164.81, 132.15, 125.97,
114.71, 70.98, 39.25, 30.37, 29.00, 23.75, 23.00, 13.81, 10.82
4,40-Di(2-decyltetradecyloxy)benzil (3m). Yellow oil (6.21g,
82%). dH(250 MHz, CD2Cl2) 7.96 (4 H, d, J = 8.8 Hz,
aromatic H), 7.04 (4 H, d, J = 8.8 Hz, aromatic H), 3.99
(4 H, d, J = 5.6 Hz, –OCH2–), 1.88–1.31 (82 H, m), 1.03–0.90
(12 H, m, –CH3). dC(62.5 MHz, CD2Cl2) 193.60, 164.82,
132.14, 125.97, 114.72, 71.43, 37.80, 31.92, 31.20, 29.95,
29.64, 29.59, 29.35, 26.76, 22.69, 13.87.
General procedure for the synthesis of 4-alkoxy-40-hydroxy-
benzil 2n–2p and 3h
To a mixture of 4,40-dihydroxybenzil (3) (1.0 g, 4.13 mmol),
powdered potassium carbonate (3.72 mmol) in DMF (40 mL)
at 90 1C was added dropwise and slowly (in about 1 h) a
solution of alkyl bromide (3.72 mmol) in DMF (40 mL). After
1 h, the reaction was quenched by adding water and the
resulting mixture was extracted by ethyl acetate. The organic
phases were combined, rinsed several times with water, dried
General procedure for the synthesis of benzils 3i–3m
A THF (50 mL) solution of 4,40-dihydroxy benzil (1.5 g,
6.2 mmol), PPh3 (3.9 g, 14.9 mmol), and alcohol (14.9 mmol)
was cooled to 0 1C. To the solution was added diethyl
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over anhydrous magnesium sulfate and concentrated
under reduced pressure resulting in the crude product
which was purified by silica gel column chromatography
(hexane/CH3COOC2H5: 75/25).
7.39 (8 H, d, J = 7.5 Hz, aromatic H), 6.88 (8 H, d, J =
7.5 Hz, aromatic H), 3.86 (12 H, s, –OCH3). dC(75 MHz,
CD2Cl2) 180.77, 160.48, 134.28, 130.34, 113.81, 55.37.
HRMS(CI): found 663.0297, [M + H]+ requires 663.0302.
4-(2-Ethylhexyloxy)-40-hydroxybenzil (2n). Yellow oil
(0.54 g, 41%). dH(300 MHz, CD2Cl2) 7.91 (4 H, m, aromatic H),
7.00 (4 H, m, aromatic H), 6.74 (1 H, br s, phenol H), 3.98
(2 H, d, J = 5.7 Hz, –OCH2–), 1.79 (1 H, m, –OCH2CH–),
1.50–1.28 (8 H, m, –CH2–), 0.99–0.91 (6 H, m, –CH3).
dC(75 MHz, CD2Cl2) 193.79, 193.69, 164.98, 162.00, 132.56,
132.27, 126.16, 125.80, 115.89, 114.78, 71.04, 60.55, 39.25,
30.38, 29.00, 23.76, 23.01, 20.85, 13.96, 13.82, 10.83.
Nickel bis[1-(4-decyloxyphenyl)-2-(4-methoxyphenyl)ethene-
1,2-dithiolene] complex ([Ni((4-OC1,40-OC10L)dpedt)2])
Black powder (0.86 g, 51%, mp 147.3 1C). Elemental analysis:
found C, 65.60; H, 7.10; Ni, 6.25; S, 14.10. C50H64NiO4S4
requires C, 65.56; H, 7.04; Ni, 6.41; S, 14.00%. dH(400 MHz,
CD2Cl2) 7.37 (8 H, m, aromatic H), 6.86 (8 H, m, aromatic H),
4.03 (4 H, t, J = 6.4 Hz, –OCH2CH2–), 3.86 (6 H, s, –OCH3),
1.85–1.80 (4 H, m, –OCH2CH2–), 1.56–1.33 (28 H, m, –CH2–
0.94 (6 H, t, J = 6.8 Hz, –CH3). dC(75 MHz, CD2Cl2) 183.52,
180.93, 160.47, 160.12, 134.08, 130.35, 114.30, 113.81, 68.22,
55.36, 31.89, 29.56, 29.55, 29.37, 29.31, 29.19, 25.98, 22.67,
13.86. HRMS(CI): found 915.3100, [M + H]+ requires
915.3119.
4-Decyloxy-40-hydroxybenzil (2o). Yellow solid (4.06 g,
57%). dH(300 MHz, CD2Cl2) 7.96–7.88 (4 H, m, aromatic
H), 7.03–6.93 (4 H, m, aromatic H), 6.01 (1 H, br s, phenol H),
4.1 (2 H, t, J = 6.3 Hz, –OCH2–), 1.88–1.79 (2 H, m,
–OCH2CH2–), 1.51–1.31 (14 H, m, –CH2–), 0.94 (3 H, t,
J = 6.3 Hz, –CH3). dC(62.5 MHz, CD2Cl2) 193.72, 193.64,
164.75, 161.86, 132.56, 132.28, 126.25, 125.86, 115.88, 114.76,
68.66, 31.91, 29.55, 29.32, 29.01, 25.90, 22.69, 13.98, 13.88.
Nickel bis[1-(4-(2-ethylhexyloxy)phenyl)-2-(4-methoxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC1,40-OC8B)dpedt)2])
Brown powder (0.64 g, 45%, mp 199.1 1C). Elemental analysis:
found C, 64.11; H, 6.44; Ni, 6.61; S, 15.20 C46H56NiO4S4
requires C, 64.25; H, 6.56; Ni, 6.83; S, 14.92%. dH(400 MHz,
CD2Cl2) 7.39 (8 H, m, aromatic H), 6.88 (8 H, m, aromatic H),
3.92 (4 H, d, J = 5.6 Hz, –OCH2CH–), 3.86 (6 H, s, –OCH3),
1.79–1.71 (2 H, m, –OCH2CH–), 1.57–1.39 (16 H, m, –CH2–),
1.00 (12 H, t, J = 7.6 Hz, –CH3). dC(100 MHz, CD2Cl2)
180.75, 180.50, 160.43, 160.32, 134.37, 134.03, 130.35, 130.33,
114.33, 113.80, 70.66, 55.34, 39.39, 30.47, 29.07, 23.83, 23.05,
13.85, 10.88. HRMS(CI): found 859.2512, [M + H]+ requires
859.2493.
4-Dodecyloxy-40-hydroxybenzil (2p). Yellow solid (3.47g,
46%). dH(250 MHz, CD2Cl2) 8.04 (1 H, br s, phenol H),
7.96 (4 H, m, aromatic H), 7.09 (4 H, m, aromatic H), 4.11
(2 H, t, J = 6.5 Hz, –OCH2–), 1.87–1.31 (20 H, m), 0.95
(3 H, t, J = 6.2 Hz, –CH3). HRMS(CI): found 411.2546,
[M + H]+ requires 411.2535.
4,40-Didodecyloxybenzil (3h). Yellowish solid isolated from
the synthesis of 2p (3.59 g, 30%). dH(250 MHz, CD2Cl2) 7.96
(4 H, m, aromatic H), 7.03 (4 H, m, aromatic H), 4.11 (4 H, t,
J = 6.5 Hz, –OCH2–), 1.87–1.32 (40 H, m, –CH2–), 0.95
(6 H, t, J = 6.3 Hz, –CH3). dC(62.5 MHz, CD2Cl2) 193.57,
164.59, 132.17, 126.00, 114.68, 68.60, 45.33, 31.93, 29.64,
29.59, 29.56, 29.36, 29.33, 29.02, 25.90, 22.70, 13.89.
HRMS(CI): found 579.4441, [M + H]+ requires 579.4413.
Nickel bis[1-(4-(3,7-dimethyloctyloxy)phenyl)-2-(4-methoxy-
phenyl)ethene-1,2-dithiolene] complex ([Ni((4-OC1,40-OC10B)-
dpedt)2])
Black powder (1.08 g, 53%, mp 170.3 1C). Elemental analysis:
found C, 65.64; H, 6.91; Ni, 6.32; S, 14.63. C50H64NiO4S4
requires C, 65.56; H, 7.04; Ni, 6.41; S, 14.00%. dH(300 MHz,
CD2Cl2) 7.38 (8 H, m, aromatic H), 6.87 (8 H, m, aromatic H),
4.07 (4 H, m, –OCH2CH2–), 3.85 (6 H, s, –OCH3), 1.88–1.20
(20 H, m), 1.00 (6 H, d, J = 6.3 Hz, –CH3), 0.93 (12 H, d, J =
6.6 Hz, –CH3). dC(75 MHz, CD2Cl2) 180.72, 180.53, 160.43,
160.07, 134.34, 134.07, 130.35, 114.30, 113.80, 66.55, 55.34,
39.23, 37.25, 36.11, 29.87, 27.98, 24.65, 22.45, 22.35, 19.41.
HRMS(CI): found 915.3079 and 943.3484, [M + H]+ requires
915.3119 and [M + C2H5]+ requires 943.3432
General procedure for the synthesis of nickel bis(1,2-dithiolene)
complexes (4a–4s)
A mixture of dialkoxybenzil (4.91 mmol) and P4S10 (4.8 g,
10.80 mmol) in 25 mL of dioxane was heated to reflux at
130 1C for 5 h. When the initial yellow suspension became a
clear dark brown solution, the hot mixture was filtered to
remove an insoluble pale yellow solid. To the filtrate was
added a solution of NiCl2ꢂ6H2O (0.64 g, 2.70 mmol) in 5 mL of
water, and the mixture was heated to reflux for 2 h. The
mixture was then cooled to room temperature and a small
quantity of water was added. The black crystalline precipitate
appeared and was collected by filtration. The crude product
was purified by repeated precipitation from solution in
CH2Cl2 by ethanol (3 times) and the final purification was
performed by column chromatography (hexane/CH2Cl2).
Nickel bis[1-(4-(2-butyloctyloxy)phenyl)-2-(4-methoxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC1,40-OC12B)dpedt)2])
Black powder (1.06 g, 49%, mp 154.8 1C). Elemental analysis:
found C, 66.93; H, 7.36; Ni, 5.86; S, 13.02. C54H72NiO4S4
requires C, 66.72; H, 7.47; Ni, 6.04; S, 13.19%. dH(300 MHz,
CD2Cl2) 7.40 (8 H, m, aromatic H), 6.89 (8 H, m, aromatic H),
3.91 (4 H, d, J = 5.7 Hz, –OCH2CH–), 3.86 (6 H, s, –OCH3),
1.84 (2 H, m, –OCH2CH–), 1.57–1.32 (32 H, m), 0.97–0.90
(12 H, m, –CH3). dC(75 MHz, CD2Cl2) 180.93, 180.68, 160.45,
160.34, 134.40, 134.06, 130.32, 130.30, 114.34, 113.80, 71.07,
Nickel bis[1,2-di(4-methoxyphenyl)ethene-1,2-dithiolene]
complex ([Ni((4-OC1,40-OC1)dpedt)2])
Black powder (0.87 g, 18%). Elemental analysis: found C,
57.88; H, 4.19; Ni, 8.71; S, 19.58. C32H28NiO4S4 requires C,
57.93; H, 4.25; Ni, 8.85; S, 19.33%. dH(300 MHz, CD2Cl2)
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55.34, 37.90, 31.85, 31.30, 30.99, 29.66, 29.04, 26.78, 23.04,
22.66, 13.86, 13.84. HRMS(CI): found 971.3742, [M + H]+
requires 971.3745.
Nickel bis[1,2-di(4-(2-butyloctyloxy)phenyl)ethene-1,2-dithiolene]
complex ([Ni((4-OC12B, 40-OC12B)dpedt)2])
Black powder (2.36 g, 51%, mp 103.2 1C). Elemental analysis:
found C, 71.57; H, 9.14; Ni, 4.32; S, 10.06. C76H116NiO4S4
requires C, 71.28; H, 9.13; Ni, 4.58; S, 10.01%. dH(300 MHz,
CD2Cl2) 7.39 (8 H, m, aromatic H), 6.88 (8 H, m, aromatic H),
3.91 (8 H, d, J = 5.7 Hz, –OCH2CH–), 1.85–1.79 (4 H, m,
–OCH2CH–), 1.54–1.34 (64 H, m, –CH2–), 0.97–0.91 (24 H,
m, –CH3), dC(75 MHz, CD2Cl2) 180.71, 160.32, 134.07,
130.29, 114.33, 71.05, 37.91, 31.85, 31.30, 31.00, 29.67, 29.05,
26.78, 23.05, 22.67, 13.87, 13.85. HRMS(CI): found
1279.7188, [M + H]+ requires 1279.7188.
Nickel bis[1-(4-(2-hexyldecyloxy)phenyl)-2-(4-methoxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC1,40-OC16B)dpedt)2])
Black powder (1.47 g, 50%, mp 147.4 1C). Elemental analysis:
found C, 68.43; H, 8.18; Ni, 5.17; S, 12.08. C62H88NiO4S4
requires C, 68.68; H, 8.18; Ni, 5.41; S, 11.83. dH(400 MHz,
CD2Cl2) 7.39 (8 H, m, aromatic H), 6.87 (8 H, m, aromatic H),
3.90 (4 H, d, J = 5.2 Hz, –OCH2CH–), 3.86 (6 H, s, –OCH3),
1.84 (2 H, m, –OCH2CH–), 1.50–1.35 (48 H, m), 0.94 (12 H,
m, –CH3). dC(100 MHz, CD2Cl2) 180.66, 180.40, 160.42,
160.31, 134.40, 134.04, 130.38, 130.35, 114.34, 113.80, 71.10,
55.33, 37.96, 31.93, 31.88, 31.33, 30.03, 29.70, 29.61, 29.35,
26.84, 26.82, 22.70, 13.91. HRMS(CI): found 1083.5101,
[M + H]+ requires 1083.4997.
Nickel bis[1,2-bis(4-(2-hexyldecyloxy)phenyl)ethene-1,2-dithiolene]
complex ([Ni(4-OC16B,4-OC16B)dpedt)2])
Black pasty powder (2.03 g, 49%). Elemental analysis: found
C, 73.75; H, 9.96; Ni, 3.58; S, 8.18. C92H148NiO4S4 requires C,
73.42; H, 9.91; Ni, 3.90; S, 8.52%. dH(300 MHz, CD2Cl2) 7.38
(8 H, d, J = 8.7 Hz, aromatic H), 6.87 (8 H, d, J = 8.7 Hz,
aromatic H), 3.91 (8 H, d, J = 5.7 Hz, –OCH2CH–), 1.83–1.80
(4 H, m, –OCH2CH–), 1.56–1.34 (96 H, m, –CH2–), 0.93–0.91
(24 H, m, –CH3), dC(75 MHz, CD2Cl2) 180.69, 160.32, 134.07,
130.29, 114.65, 114.33, 71.06, 37.94, 31.91, 31.86, 31.30, 30.00,
29.67, 29.58, 29.32, 26.81, 26.79, 22.68, 13.88. HRMS(CI):
found 1503.9624, [M + H]+ requires 1503.9692.
Nickel bis[1,2-di(4-(2-ethylhexyloxy)phenyl)ethene-1,2-dithiolene]
complex ([Ni((4-OC8B,40- OC8B)dpedt)2])
Brown powder (2 g, 47%, mp 163.7 1C). Elemental analysis:
found C, 68.55; H, 8.07; Ni, 5.42; S, 12.10. C60H84NiO4S4
requires C, 68.23; H, 8.02; Ni, 5.56; S, 12.14. dH(400 MHz,
CD2Cl2) 7.38 (8 H, d, J = 8.4 Hz, aromatic H), 6.88 (8 H, d,
J = 8.4 Hz, aromatic H), 3.92 (8 H, d, J = 5.6 Hz,
–OCH2CH–), 1.80 (4 H, m, –OCH2CH–), 1.57–1.37 (32 H,
m,–CH2–), 0.99–0.95 (24 H, m, –CH3). dC(100 MHz, CD2Cl2)
180.78, 160.34, 134.07, 130.33, 114.33, 70.67, 39.38, 30.46,
29.06, 23.82, 23.04, 13.83, 10.87. HRMS(CI): found
1055.4709, [M + H]+ requires 1055.4684.
Nickel bis[1,2-bis(4-(2-octyldodecyloxy)phenyl)ethene-1,2-
dithiolene] complex ([Ni((4-OC20B,40-OC20B)dpedt)2])
Black pasty powder (2.28 g, 43%). Elemental analysis: found
C, 75.19; H, 10.64; Ni, 3.16; S, 6.72. C108H180NiO4S4 requires
C, 75.00; H, 10.49; Ni, 3.39; S, 7.42%. dH(400 MHz, CD2Cl2)
7.38 (8 H, d, J = 8.8 Hz, aromatic H), 6.87 (8 H, d, J = 8.8 Hz,
aromatic H), 3.91 (8 H, d, J = 5.2 Hz, –OCH2CH– 1.84
(4 H, m, –OCH2CH–), 1.50–1.34 (128 H, m, –CH2–), 0.95
(24 H, m, –CH3). dC(100 MHz, CD2Cl2) 180.60, 160.31,
134.11, 130.32, 114.33, 71.09, 37.97, 31.95, 31.32, 30.03,
29.70, 29.67, 29.66, 29.61, 29.38, 29.36, 26.85, 22.71, 13.92.
MS(CI): found 1729.10, [M + H]+ requires 1729.21.
Nickel bis[1,2-di(4-dodecyloxyphenyl)ethene-1,2-dithiolene]
complex ([Ni((4-OC12L,40- OC12L)dpedt)2])
Brown powder (1.6 g, 48%, mp 168.8 1C). Elemental analysis:
found C, 71.62; H, 9.08; Ni, 4.46; S, 9.32. C76H116NiO4S4
requires C, 71.28; H, 9.13; Ni, 4.58; S, 10.01%. dH(300 MHz,
CD2Cl2) 7.37 (8 H, dd, J = 2.0–9.0 Hz, aromatic H), 6.86
(8 H, dd, J = 2.0–9.0 Hz, aromatic H), 4.00 (8 H, t, J = 6.6 Hz,
–OCH2CH2–), 1.86–1.77 (8 H, m, –OCH2CH2–), 1.51–1.42
(72 H, m), 0.92 (12 H, t, J = 6.3 Hz, –CH3). dC(75 MHz,
CD2Cl2) 180.73, 160.09, 134.11, 130.33, 114.29, 68.21,
31.94, 29.65, 29.61, 29.40, 29.36, 29.30, 29.21, 26.01, 22.71,
Nickel bis[1,2-bis(4-(2-decylyltetradecyloxy)phenyl)ethene-1,2-
dithiolene] complex ([Ni((4-OC24B,40-OC24B)dpedt)2])
Black pasty powder (3.74 g, 57%). Elemental analysis: found
C, 76.79; H, 11.11; Ni, 2.86; S, 6.91. C124H212NiO4S4 requires
C, 76.22; H, 10.94; Ni, 3.00; S, 6.56. dH(300 MHz, CD2Cl2)
7.38 (8 H, d, J = 8.7 Hz, aromatic H), 6.87 (8 H, d, J =
8.7 Hz, aromatic H), 3.90 (8 H, d, J = 5.7 Hz, –OCH2CH–),
1.82 (4 H, m, –OCH2CH–) 1.56–1.30 (160 H, m, –CH2–),
0.94–0.85 (24 H, m, –CH3), dC(75 MHz, CD2Cl2) 180.72,
160.32, 134.07, 130.28, 114.33, 71.07, 37.91, 31.92, 31.27,
29.99, 29.66, 29.62, 29.35, 26.80, 22.69, 13.88. MS (CI): found
1953.57, [M + H]+ requires 1953.47.
13.89. HRMS(CI): found 1279.7148, [M
requires 1279.7188.
+
H]+
Nickel bis[1,2-di(4-(3,7-dimethyloctyloxy)phenyl)ethene-1,2-
dithiolene] complex ([Ni((4-OC10B,40-OC10B)dpedt)2])
Black powder (1.44 g, 59%, mp 129.9 1C). Elemental analysis:
found C, 69.85; H, 8.74; Ni, 4.78; S, 11.25. C68H100NiO4S4
requires C, 69.90; H, 8.63; Ni, 5.02; S, 10.98%. dH(400 MHz,
CD2Cl2) 7.37 (8 H, d, J = 8.4 Hz, aromatic H), 6.86 (8 H, d,
J = 8.4 Hz, aromatic H), 4.07 (8 H, m, –OCH2CH2–),
1.90–1.84 (8 H, m, –OCH2CH2–), 1.73–1.21 (32 H, m), 1.01
(12 H, d, J = 6.4 Hz, –CH3), 0.94 (24 H, d, J = 6.4 Hz, –CH3).
dC(100 MHz, CD2Cl2) 180.58, 160.05, 134.14, 130.35, 114.30,
66.55, 39.24, 37.27, 36.14, 29.88, 28.00, 24.66, 22.47, 22.37,
19.43. HRMS(CI): found 1167.5953, [M + H]+ requires
1167.5936.
Nickel bis[1-(4-(2-ethylhexyloxy)phenyl)-2-(4-decyloxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC10L,40-OC8B)dpedt)2])
Black powder (1.24 g, 73%, mp 153.2 1C). Elemental analysis:
found C, 68.80; H, 8.23; Ni, 5.06; S, 11.57. C64H92NiO4S4
requires C, 69.10; H, 8.34; Ni, 5.28; S, 11.53%. dH(400 MHz,
CD2Cl2) 7.37 (8 H, d, J = 8.4 Hz, aromatic H), 6.86 (8 H, m,
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aromatic H), 4.02 (4 H, t, J = 6.4 Hz, –OCH2CH2–), 3.92
(4 H, d, J = 5.2 Hz, –OCH2CH–), 1.84–1.75 (6 H, m),
1.57–1.34 (44 H, m), 1.00–0.92 (18 H, m, –CH3). dC(100 MHz,
CD2Cl2) 180.59, 180.55, 160.29, 160.05, 134.16, 134.10, 130.35,
114.32, 114.28, 70.65, 68.20, 39.40, 31.92, 30.48, 29.60, 29.58,
29.41, 29.34, 29.23, 29.08, 26.02, 23.84, 23.06, 22.70, 13.89,
13.87, 10.90. HRMS(CI): found 1111.5359, [M + H]+
requires 1111.5310.
1.87–1.78 (6 H, m), 1.57–1.32 (68 H, m), 0.97–0.90 (18 H, m,
–CH3). dC(75 MHz, CD2Cl2) 180.71, 180.65, 160.31, 160.07,
134.13, 134.05, 130.32, 130.30, 114.32, 114.28, 71.05, 68.20,
37.91, 31.92, 31.86, 31.30, 31.00, 29.67, 29.64, 29.60, 29.58,
29.39, 29.35, 29.21, 29.05, 26.79, 26.00, 23.05, 22.69, 22.67,
13.88, 13.86. HRMS(CI): found 1279.7188, [M + H]+
requires 1279.7188.
Nickel bis[1-(4-(3,7-dimethyloctyloxy)phenyl)-2-(4-dodecyloxy-
phenyl)ethene-1,2-dithiolene] complex ([Ni((4-OC12L,40-OC10B)-
dpedt)2])
Nickel bis[1-(4-(3,7-dimethyloctyloxy)phenyl)-2-(4-decyloxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC10L,40-OC10B)dpedt)2])
Brown powder (1.13 g, 55%, mp 149.7 1C). Elemental analysis:
found C, 70.80; H, 8.88; Ni, 4.64; S, 10.20. C72H108NiO4S4
requires C, 70.62; H, 8.89; Ni, 4.79; S, 10.47%. dH(300 MHz,
CD2Cl2) 7.38 (8 H, d, J = 9.0 Hz, aromatic H), 6.87 (8 H, dd,
J = 1.5–9.0 Hz, aromatic H), 4.08–3.99 (8 H, m, –OCH2–),
1.85–1.20 (60 H, m), 1.00–0.90 (24 H, m, –CH3). dC(75 MHz,
CD2Cl2) 180.71, 160.07, 134.10, 130.31, 114.29, 68.20, 66.54,
39.22, 37.23, 36.10, 31.92, 29.86, 29.65, 29.63, 29.59, 29.57,
29.38, 29.34, 29.19, 27.98, 25.99, 24.64, 22.68, 22.43, 22.34,
19.39, 13.89. HRMS(CI): found 1223.6636, [M + H]+
requires 1223.6562.
Black powder (1.7 g, 59%, mp 158.5 1C). Elemental analysis:
found C, 70.04; H, 8.68; Ni, 4.94; S, 11.11. C68H100NiO4S4
requires C, 69.90; H, 8.63; Ni, 5.02; S, 10.98%. dH(300 MHz,
CD2Cl2) 7.37 (8 H, m, aromatic H), 6.86 (8 H, m, aromatic H),
4.04 (8 H, m, –OCH2CH2–), 1.90–1.20 (52 H, m), 1.00–0.90
(24 H, m, –CH3). dC(75 MHz, CD2Cl2) 180.61, 160.05, 134.12,
130.34, 114.28, 68.20, 66.54, 39.23, 37.25, 36.12, 31.91, 29.87,
29.59, 29.57, 29.39, 29.33, 29.21, 27.99, 26.01, 24.65, 22.69,
22.45, 22.35, 19.41, 13.89. HRMS(CI): found 1167.5985,
[M + H]+ requires 1167.5936.
Nickel bis[1-(4-dodecyloxyphenyl)-2-(4-tetradecyloxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC12L,40-OC14L)dpedt)2])
Acknowledgements
Brown powder (0.67 g, 52%, Mp 163.7 1C). Elemental
analysis: found C, 71.82; H, 9.42; Ni, 4.21; S, 8.68.
C80H124NiO4S4 requires C, 71.88; H, 9.35; Ni, 4.39; S,
9.59%. dH(300 MHz, CD2Cl2) 7.37 (8 H, dd, J = 2.0–9.0 Hz,
aromatic H), 6.86 (8 H, dd, J = 2.0–9.0 Hz, aromatic H), 4.00
(8 H, t, J = 6.6 Hz, –OCH2CH2–), 1.88–1.75 (8 H, m,
–OCH2CH2–), 1.54–1.31 (80 H, m), 0.92 (12 H, t, J =
6.3 Hz, –CH3). dC(75 MHz, CD2Cl2) 180.98, 160.08, 134.10,
130.31, 114.28, 68.20, 31.92, 29.65, 29.59, 29.57, 29.37, 29.34,
29.19, 25.98, 22.68, 13.86. HRMS(CI): found 1335.7930,
[M + H]+ requires 1335.7814.
Authors thank the French National Research Agency for
financial support as part of ANR CPA-FALOIR 2007–2010
Project. Authors also thank A. Sournia-Saquet for the
preliminary electrochemical investigation.
References
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Nickel bis[1-(4-dodecyloxyphenyl)-2-(4-undecyloxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC12L,40-OC11L)dpedt])2])
Brown powder (0.79 g, 68%, mp 171.9 1C). Elemental analysis:
found C, 70.68; H, 9.12; Ni, 4.52; S, 9.06. C74H112NiO4S4
requires C, 70.95; H, 9.01; Ni, 4.69; S, 10.24%. dH(300 MHz,
CD2Cl2) 7.38 (8 H, dd, J = 2.0–9.0 Hz, aromatic H), 6.86
(8 H, dd, J = 2.0–9.0 Hz, aromatic H), 4.00 (8 H, t, J = 6.6 Hz,
–OCH2CH2–), 1.84–1.77 (8 H, m, –OCH2CH2–), 1.56–1.32
(68 H, m), 0.92 (12 H, t, J = 6.6 Hz, –CH3). dC(75 MHz,
CD2Cl2) 180.72, 160.08, 134.10, 130.31, 114.28, 68.20, 31.91,
29.65, 29.63, 29.60, 29.57, 29.38, 29.34, 29.19, 25.99, 22.68,
13.87. HRMS(CI): found 1251.6968, [M + H]+ requires
1251.6875.
8 K. Ohta, A. Takagi, H. Muroki, I. Yamamoto, K. Matsuzaki,
T. Inabe and Y. Maruyama, Mol. Cryst. Liq. Cryst., 1987, 147,
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Nickel bis[1-(4-(2-butyloctyloxy)phenyl)-2-(4-dodecyloxyphenyl)-
ethene-1,2-dithiolene] complex ([Ni((4-OC12L,40-OC12B)dpedt)2])
9 K. Ohta, H. Hasebe, M. Moriya, T. Fujimoto and I. Yamamoto,
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A. Mancini, L. Pala, G. Verani, T. Agostinelli, M. Caironi,
D. Natali and M. Sampietro, Inorg. Chem. Commun., 2007, 10,
191–194.
Black powder (1.48 g, 71%, mp 99.0 1C). Elemental analysis:
found C, 70.98; H, 9.17; Ni, 4.33; S, 9.59. C76H116NiO4S4
requires C, 71.28; H, 9.13; Ni, 4.58; S, 10.01%. dH(300 MHz,
CD2Cl2) 7.38 (8 H, d, J = 8.7 Hz, aromatic H), 6.87 (8 H, dd,
J = 1.5–8.7 Hz, aromatic H), 4.00 (4 H, t, J = 6.6 Hz,
–OCH2CH2–), 3.90 (4 H, d, J = 5.7 Hz, –OCH2CH–),
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