Discotic nickel bis(dithiolene) complexes - Synthesis, optoelectrochemical and mesomorphic properties

FULL PAPER

DOI: 10.1002/ejic.201001288

Discotic Nickel Bis(dithiolene) Complexes – Synthesis, Optoelectrochemical

and Mesomorphic Properties

Thanh-Tuan Bui,^[a,b]Olivier Thiebaut,^[c]Eric Grelet,^[c]Marie-France Achard,^[c]

Bénédicte Garreau-de Bonneval,*^[a,b]and Kathleen I. Moineau-Chane Ching*^[a,b]

Keywords: Nickel / S ligands / Liquid crystals / Electrochemistry / Organic electronics

Fifteen neutral long-chain-substituted discotic nickel bis(1,2-

diphenyl-1,2-ethenedithiolene) complexes [Ni(dpedt)₂], in-

cluding thirteen new compounds, have been synthesized by

new short and efficient synthetic pathways. Physical investi-

gations show that these complexes are thermally stable, pos-

sess good electron-accepting properties, and absorb light

strongly in the near-infrared spectral region. Electrochemical

and optical properties of [Ni(dpedt)₂] depend moderately on

the functionalities attached to the phenyl rings of the com-

plexes. Their LUMO and HOMO energy levels are in the

range –4.7 to –5.0 and –5.7 to –6.0 eV, respectively. Two oc-

ta(n-alkoxy)-substituted complexes exhibit a columnar liquid

crystalline phase with hexagonal symmetry. These highly

soluble complexes are potential candidates for use as elec-

tron-accepting and electron-transporting materials for active

layers in organic electronic applications, such as field-effect

transistors or photovoltaic devices.

photovoltaics.^[6]In this aim, the realization of an oriented

bilayer heterojunction has been recently achieved by an-

nealing-induced macroscopic self-assembly of two colum-

nar liquid crystals based on perylene and pyrene deriva-

tives,^[7]bringing the first proof of principle of an organic

heterojunction based on two oriented columnar liquid crys-

tal layers. To continue, we are now expanding our investi-

gations towards new electron-accepting columnar liquid

crystalline materials that absorb in the near-infrared (NIR).

Nowadays, only a few discotic materials are known to ab-

sorb in the NIR region.^[8]Moreover, research on new NIR

materials for organic photovoltaics is mainly focused on

electron-donating materials;^[9]less work has been dedicated

to their electron-accepting counterparts. A recent example

of NIR acceptor materials is 9,9Ј-bifluorenylidene, which

leads to a power conversion efficiency of up to 2%.^[10]In

this context, neutral nickel bis(dithiolene) complexes are

promising potential candidates. The optical, magnetic, con-

ductive, and superconductive properties of these complexes

have placed them among the most important families of

precursors to new generations of optoelectronic devices.^[11]

In the present work, we are interested in the synthesis and

physical features of discotic compounds based on neutral

nickel bis(1,2-diphenylethene-1,2-dithiolene) complexes, ab-

breviated as [Ni(dpedt)₂].

Introduction

In the last decade, the research in organic photovoltaics

has led to many important achievements. The power con-

version efficiency of devices initially reported by Tang,^[1]

was 1%; nowadays it has risen to values higher than 7%.^[2]

The most promising results have been obtained with bulk

heterojunction device architectures, which are based on the

association of electron-donating and electron-accepting

semiconducting materials. Absorption of photons generates

excitons, which diffuse to the donor/acceptor interface,

where they are dissociated into free charge carriers, holes

and electrons, respectively. Donor/acceptor heterojunctions

in organic electronics can be created with different materials

for the active layer, and a smart way to improve the charge

carrier mobility is to use liquid crystalline ordering.^[3]Dis-

cotic columnar liquid crystals have been shown to exhibit

high exciton diffusion lengths and charge carrier mobilities

along the columns relative to conventional materials used

in organic photovoltaic cells.^[4,5]

In the last few years, many research activities have fo-

cused on the use of liquid crystalline materials in organic

[a] CNRS: LCC (Laboratoire de Chimie de Coordination),

205 Route de Narbonne, 31077 Toulouse, France

Fax: +33-561553003

E-mail: bdb@lcc-toulouse.fr

kathleen.chane@lcc-toulouse.fr

[b] Université de Toulouse (UPS, INPT, LCC),

31077 Toulouse, France

Results and Discussion

[c] Centre de Recherche Paul-Pascal, CNRS – Université de

Bordeaux,

Material Synthesis

115 Avenue Schweitzer, 33600 Pessac, France

Supporting information for this article is available on the

WWW under http://dx.doi.org/10.1002/ejic.201001288.

The synthetic pathways are outlined in Scheme 1, and

the list of nickel complexes is presented in Table 1.

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Scheme 1. Synthesis of nickel bis(dithiolene) complexes. Reagents and conditions: (i) DEAD (2.4 equiv.), PPh₃(2.4 equiv.), decanoic acid

(2.4 equiv.), tetrahydrofuran, 0 °C then 1 h at room temperature; (ii) and (v) RBr (2.4 equiv.), K₂CO₃(3.0 equiv.), dimethylformamide,

90 °C; (iii) Br₂(2 to 5.0 equiv.), FeCl₃(1.0 to 2.0 equiv.), dichloromethane/acetonitrile (1:0 to 1:1 v/v), room temperature or reflux

overnight; (iv) NIS, trifluoroacetic acid, reflux 3.5 h; (vi) ROH (2.4 equiv.), DEAD (2.4 equiv.), PPh₃(2.4 equiv.), tetrahydrofuran, 0 °C

then 1 h at room temperature; (vii) oxalyl chloride (0.6 equiv.), AlCl₃(0.5 equiv.), 1,2-dichloroethane, 0 °C then overnight at room tem-

perature; (viii) 1) NaCN (0.4 equiv.), water/ethanol (1:2 v/v), reflux 36 h 2) Cu(OAc)₂(0.01 equiv.), NH₄NO₃(1.25 equiv.), acetic acid/

water (4:1 v/v), reflux 2 h; (ix) 1) bromohydric acid/acetic acid (1:1 v/v), reflux 5 h 2) excess C₁₀H₂₁Br, K₂CO₃, dimethylformamide, 18 h

at 90 °C; (x) P₄S₁₀(2.2 equiv.), dioxane, reflux 5 h then adding NiCl₂·6H₂O (0.55 equiv.), water, reflux 2 h in air.

Synthesis of 4,4Ј-Didecyloxybenzil and Its Halogenated

nickel complexes, we use the ether and ester functions. The

Derivatives

symmetric 4,4Ј-didecyloxybenzil (2a) is obtained by the

In this part, we present the synthesis of disubstituted Mitsunobu reaction from the 4,4Ј-dihydroxybenzil (1) in

benzil derivatives. The substituents are in all cases long quantitative yield by heating the mixture of 1 with a large

alkyl chains. In order to study the influence of the connect- excess of decyl bromide and potassium carbonate in di-

ing group on the mesomorphic and physical properties of methylformamide. As demonstrated in a previous study,^[12]

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Discotic Nickel Bis(dithiolene) Complexes

Table 1. List of long-chain-substituted nickel bis(dithiolene) complexes [Ni(dpedt)₂].

[a] Racemic-3,7-dimethyloctyloxy. [b] Racemic-2-ethylhexyloxy. [c] Yields are related to complex formation.

the Mitsunobu reaction^[13]is a powerful tool for synthesis Synthesis of Tetraalkoxybenzils

of aromatic ethers directly from phenol derivatives and

1,2-Dialkoxybenzenes 3 are obtained from pyrocathecol.

alcohols. In this case, phenol derivatives play the role of The desired linear and branched alkyl chains are attached

the weak acid. Interestingly, in the Mitsunobu reaction, the to the phenol functions by either the classical nucleophilic

phenol derivatives may play an ambivalent role. When the substitution (3a, 3b, 3d–3e) or the Mitsunobu method (3c),

alcohol is replaced by n-decanoic acid, 1 reacts as an depending on the commercial availability of the alkyl

alcohol, providing the corresponding ester 2b in good yield chains. 3,3Ј,4,4Ј-Octaalkoxybenzil derivatives 4 are achieved

(93%) without any optimization. The halogenation of 2a by the double Friedel–Crafts reaction with oxalyl chloride

resulting in benzil derivatives 2c–2g is performed by using as the acylating agent.^[15]The benzil backbone is created in

modified procedures reported elsewhere.^[14]The treatment one step in moderate yields (around 30–40%). Although

of 2a with excess bromine in dichloromethane only gives 3- Mohr et al.^[15]reported that two equivalents of aluminum

bromo-4,4Ј-didecyloxybenzil (2c) in low yield (12% after chloride per equivalent of oxalyl chloride are needed, it is

12 h at room temperature). The introduction of one stoi- found that only one is sufficient. We then attempted to cou-

chiometric equivalent of ferric chloride gives a mixture of ple the intermediate complex aroyl chloride with additional

2c and dibromo-substituted benzil 2d with a mass ratio 2c/ 1,2-dialkoxybenzene in situ to prepare and isolate the

2d of approximately 1:2 after reaction overnight at ambient asymmetrical 1,2-diketones by a one-pot procedure as pre-

temperature. Compound 2d can be also achieved in good sented in Scheme 2 (see Experimental Section for more de-

yield (94%) by heating 2a at reflux overnight with an excess tail).

of Br₂and two equivalents of ferric chloride in an equivolu-

However, in each case, after purification by column

metric mixture of dichloromethane and acetonitrile. Di/tri/ chromatography, a mixture of inseparable benzil derivatives

tetraiodo-substituted benzils 2e–2g are synthesized by heat- is obtained. The three benzil derivative mixtures, B10.10 (R

ing 2a at reflux with N-iodosuccinimide (NIS) in trifluoro- = n-decyl, RЈ = 3,7-dimethyloctyl), B11.10 (R = n-undecyl,

acetic acid as solvent. Depending on the NIS/2a stoichiom- RЈ = 3,7-dimethyloctyl), and B11.8 (R = n-undecyl, RЈ =

etry (2:1, 3:1, or 5:1), 2e, 2f, and 2g are isolated as major n-octyl), appeared as a single spot when analyzed by thin

products in acceptable yields 88%, 43%, and 59%, respec- layer chromatography. This is due to the very similar molec-

tively. During the synthesis of 2e, careful purification of ular structures, weights, and polarities of these products.

crude product gives a small quantity of 2f. When the quan- The analysis of these mixtures by high-performance liquid

tity of NIS is raised up to five equivalents, 2g is obtained chromatography shows the presence of three benzils with a

as main product in addition to a small quantity of 2f. The mass proportion of approximately 1:2:1. None of the mix-

use of three equivalents of NIS gives a mixture of the three tures was further purified or characterized but transformed

compounds: 2e–2g, 2f being the major product.

directly into nickel bis(dithiolene) complexes.

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Scheme 2. Synthesis of mixture of asymmetrical benzils.

The synthesis of 3,3Ј,5,5Ј-tetradecyloxybenzil (4d) is de-

The three benzil mixtures B10.10, B11.10, and B11.8 are

picted in Scheme 1. This synthesis was developed by follow- transformed into three black mixtures of octaalkoxy-substi-

ing the modified route of Wenz^[16]and Ohta.^[17]The ben- tuted nickel bis(dithiolene) complexes, called 10.10, 11.10,

zoin condensation of 3,5-dimethoxybenzaldehyde catalyzed and 11.8, respectively (Scheme 3).

by sodium cyanide gives the corresponding benzoin. This

product is not purified but directly used in the next step.

The cupric acetate catalytic oxidation of benzoin to ben-

zil^[18]provides 3,3Ј,5,5Ј-tetramethoxybenzil (4e) in moderate

yields after two steps (22%). Compound 4e is then demeth-

ylated in a boiling mixture of bromic and acetic acids, giv-

ing the 3,3Ј,5,5Ј-tetrahydroxybenzil intermediate as a yellow

solid. This intermediate is then heated without any purifica-

tion with a large excess of decyl bromide and potassium

carbonate, providing 3,3Ј,5,5Ј-tetradecyloxybenzil (4d). The

yellow solid 4d is obtained in a 53% yield after two steps of

demethylation and alkylation from 4e. Globally, the desired

benzil 4d is achieved in a 12% yield from the commercially

available 3,5-dimethoxybenzaldehyde.

Synthesis of Tetra- and Octa-Long-Chain-Substituted

Nickel Bis(dithiolene) Complexes

Scheme 3. Synthesis of mixtures of octaalkoxy-substituted nickel

complexes.

As depicted in Scheme 1, the final neutral nickel com-

plexes are achieved from the benzil precursors. This step

has been already discussed in a previous work.^[12]Almost

all nickel complexes were obtained in quite good yields (see

Table 1), except for 5g, for which a major portion of black

crude product could not be purified because of its low solu-

bility. Repeated column chromatography purification pro-

vides two green compounds in small quantities (5g and 5h

with a mass ratio 5g/5h of ca. 6:1). The structure of 5h (Fig-

Theoretically, each of the three mixtures may contain up

to eight nickel complexes (cis/trans configuration is ig-

nored). Byproducts and impurities are eliminated by re-

peated precipitation processes from dichloromethane solu-

tion and repeated column chromatography with mixtures of

hexane and dichloromethane as eluents. However, it is not

possible to separate the nickel complexes from these mix-

tures.

1

ure 1) was elucidated by H and ¹³C NMR spectroscopy

and mass spectrometry.

By convention, all complexes in the present work are pre-

sented in their trans configuration, as their exact configura-

tions were not elucidated, because no suitable crystals for

single-crystal X-ray diffraction analysis were obtained. Ex-

cept for mixtures of complexes, all compounds were iden-

tified by usual analytical methods such as ¹H and ¹³C

NMR spectroscopy, mass spectrometry, electronic absorp-

tion spectroscopy, and elemental analysis.

In order to envisage the use of our nickel bis(dithiolene)

complexes as active materials in organic electronic devices,

physical properties of these complexes have to be charac-

Figure 1. Structure of 5h.

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Discotic Nickel Bis(dithiolene) Complexes

terized. In the following text, the electrochemical, optical

and phase behavior properties of these compounds will be

presented.

Electrochemical and Optical Properties

The electrochemical properties of these long-chain-sub-

stituted nickel complexes were investigated by cyclic and

square wave voltammetry (see Table S1 in the Supporting

Information). In some cases, we recorded irreversible redox

processes on platinum electrodes, and the results were

somewhat less exploitable than those obtained by using

glassy carbon electrodes. However, the results globally re-

mained in good accordance, regardless of the working elec-

trode. To a first approximation, the reduction potential Figure 2. Cyclic voltammograms of 5a, 5g, and 5f in dichlorometh-

ane (10^–3molL^–1) on glassy carbon at 0.1 Vs^–1with 0.1 molL^–1

(nBu₄N)[PF₆]; starting potential: 0.2 V/ECS.

(couple 2) can be related to the electron affinity, EA, and

thus to the LUMO energy level, according to the following

equation: EA (E_LUMO) = –(E_1/2²+ 4.8).^[19,20]A similar rela-

tionship can be used for the oxidation potential (couple 3),

trochemical properties.^[22]This is due to the difference of

the ionization potential, IP, and the HOMO energies: IP

3

the nature of the connecting group between the chains and

the phenyl groups. Compound 5g was synthesized to study

the influence of the connecting group. It differs from 5a by

the nature of the connecting group [–O– in 5a and –

OC(=O)– in 5g], whereas the chain lengths are the same

(C₁₀). The replacement of n-decyloxy substituents by n-dec-

anoate ones slightly increases the values of both redox po-

tentials of 5g in comparison with those of 5a. This is attrib-

uted to the electron-attracting effect of the carbonyl group,

which decreases the electron density on the complex core.

(E_HOMO) = –(E_1/2+ 4.8).

The optical properties of the nickel complexes were in-

vestigated by UV/Vis/NIR absorption spectroscopy in

dichloromethane. The experimental values of the maximum

of absorption (λ_max), the molar extinction coefficient (ε),

and the optical band gap (E_g^opt) are summarized in Table 2.

opt

The optical band gap is calculated by the equation: E_g

=

hc/λ_onsetaccording to Tauc’s law.^[20]The typical cyclic vol-

tammograms of 5a, 5g, and 5f in dichloromethane solution

are shown in Figure 2. Three redox waves are observed for

each compound, as described before.^[21]

2

3

As a consequence, the E_1/2and E_1/2values for 5g are

shifted to higher potential values (ca. 140 and 270 mV,

respectively), while the electrochemical band gap is slightly

broadened (ca. 130 mV) relative to that of 5a. The mea-

sured values of 5h are nearly identical to those of 5g. The

replacement of one oxygen atom in 5g by a sulfur atom in

5h has a negligible influence on the electrochemical proper-

ties of the complex (see the energy levels of 5g and 5h in

Table 2). Both HOMO and LUMO levels are lowered, while

the band gap of the new materials is increased. Table 2 also

presents the optical data for 5g and 5h. They have identical

absorption spectra as a result of the very small difference

between the two compounds and show a blue shift relative

All the electrochemical and optical data of the nickel

complexes in dichloromethane solution are presented in

Table 2. From cyclic voltammetry measurements, the half-

wave potentials of reversible electrochemical processes are

measured and used to evaluate the LUMO and HOMO en-

ergy levels.

Tetra-Long-Chain-Substituted Nickel Complexes and

Related Compounds

Influence of the Connecting Group

It has been demonstrated for the tetra-long-chain-substi- to 5a (Table 2). The optical band gaps of 5h and 5g are

tuted [Ni(dpedt)₂] that the replacement of alkoxy substitu- 1.26 eV and are consistent with values obtained from elec-

ents by alkyl ones causes moderate variation in their elec- trochemical measurements. In conclusion, the electrochemi-

Table 2. Electrochemical and optical data of tetra-long-chain-substituted nickel bis(dithiolene) complexes.

ε (Lcm^–1mol^–1) E_g

(eV)

2[a]

3[b]

CV[c]

opt[d]

Complex E_1/2(V)

E_1/2

(V)

E_g

(V)

E_LUMO(eV)

E_HOMO(eV)

λ_max(nm)

5a

5b

5c

5d

5e

5f

–0.09

–0.04

0.01

0.09

0.18

0.05

0.04

0.91

0.97

1.04

1.02

1.17

1.32

1.18

1.17

1.00

1.01

1.03

1.01

1.08

1.14

1.13

–4.7

–4.8

–4.9

–5.0

–4.8

–5.7

–5.8

–6.0

–6.1

–6.0

932

927

920

927

900

877

865

39000

33000

31000

50000

43000

34000

36000

1.17

1.18

1.16

1.19

1.23

1.26

5g

5h

CV

3

opt

[a] E_1/2²: half-wave potential of couple 2. [b] E_1/2³: half-wave potential of couple 3. [c] E_g= E_1/2– E_1/2². [d] E_g= hc/λ_onset

.

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B. Garreau-de Bonneval, K. I. Moineau-Chane Ching et al.

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cal properties of tetra-long-chain substituted [Ni(dpedt)₂] interesting finding opens the way to modulate the energy

depend to some extent on the nature of the connecting levels of semiconducting materials based on [Ni(dpedt)₂]

group.

derivatives for organic electronic applications.

Influence of Halogenation

Octa-Long-Chain-Substituted Nickel Complexes

The introduction of halogen atoms such as bromine and

iodine on the phenyl rings of tetraalkoxy-substituted [Ni-

The electrochemical data for octaalkoxy-substituted

(dpedt)₂] is expected to have an important influence on [Ni(dpedt)₂] are gathered in Table 3.

their physical properties. The redox properties of these ha-

The results obtained from cyclic and square wave vol-

logenated compounds (5b–f) and their HOMO and LUMO tammetry experiments are in good consistency with data

energy levels derived from cyclic voltammetry measure- reported elsewhere.^[17,23]The first one-electron oxidation

ments are given in Table 2. The results obtained from cyclic process of these compounds is irreversible. Therefore, the

or square wave voltammetry are in good agreement. The electrochemical band gap of these compounds is undeter-

redox potentials and electrochemical band gaps obtained minable. When comparing the electrochemical data of oc-

from cyclic voltammetry studies are gathered, together with taalkoxy-substituted [Ni(dpedt)₂] 5i, 5k, and 5l summed up

5a as reference, in Table 2 (see also Figures S1 and S2 in in Table 3, it can be deduced that their electrochemical

the Supporting Information). The electron affinity and the properties depend neither on the alkyl chain length nor on

electrochemical band gap of 5b increase slightly in compari- their configuration. Compound 5j differentiates from its

son with those of 5a. When two more bromine atoms are isomer 5i by the position of n-decyloxy chains on the phenyl

introduced (5c), the electron affinity and ionization poten- pendent rings; consequently these two compounds present

2

3

tials, expressed as E_1/2and E_1/2values, show more signifi- significant variation in their electrochemical properties. The

cant variation (a difference of 100 mV in comparison with electron affinity and ionization potential of 5j are higher

the value for 5a). The introduction of four iodine atoms than those of 5i. It is well known for [Ni(dpedt)₂] deriva-

gives 5d, whose properties are nearly identical to those of tives (or their heteroaromatic analogues) that there is a ste-

5c. When the number of iodine atoms in the complex in- ric constraint on the ligand, resulting in an out-of-plane

creases, one clearly observes the linear increase in both re- twist of the two phenyl (or heteroaromatic) rings, as attested

dox properties and electrochemical band gaps as a function by crystal structures obtained by X-ray diffraction.^[24]Nev-

of the number of iodine atoms (see also Figures S1 and S2 ertheless, the conjugation of the ether moieties is less ef-

in the Supporting Information). The introduction of halo- ficient in the meta-substituted 5j than that in the para-sub-

gen atoms on the phenyl rings of dpedt ligands lowers to stituted 5i. The electronic communication between the

some extent the HOMO and LUMO levels. However, as phenyl rings and the bis(dithiolene) complex core in 5j is

already discussed, the more abundant the halogen atoms reduced in comparison to that in 5i, 5k, and 5l. This inter-

are, the larger are the band gaps.

esting result is further confirmed by optical measurements.

Table 2 also summarizes the optical data for the haloge-

Table 3 also presents the LUMO levels of all the octaal-

nated complexes. The spectra of 5b–5d are nearly identical koxy-substituted [Ni(dpedt)₂]; their values are around

to that of 5a. However, 5e (containing six iodine atoms) and –4.7 eV and are nearly identical to those of tetra-long-

5f (containing eight iodine atoms) show a significant blue chain-substituted complexes.

shift. The optical band gaps vary from 1.16 to 1.23 eV, ac-

Table 3 summarizes optical properties of all octaalkoxy-

cording to the electrochemical data. Generally, we show substituted complexes (5i–5l) in dichloromethane solution.

that adding halogen atoms to the dpedt ligand is a com- Complexes 5i, 5k, and 5l have the same electronic absorp-

mon, effective route toward the modulation of the redox tion behavior.

properties of tetra-long-chain-substituted [Ni(dpedt)₂] with-

The typical UV/Vis/NIR absorption spectra of tetradecy-

out a major change in their electrochemical band gaps. This loxy-substituted complex 5a, octadecyloxy-substituted 5i,

Table 3. Electrochemical and optical data for octa-long-chain-substituted nickel bis(dithiolene) complexes; working electrode: Pt or glassy

carbon.^[a]

ε (Lcm^–1mol^–1) E_g

(eV)

2[b]

3[c]

CV[d]

opt[e]

Complex E_1/2

(V)

E_1/2(V)

E_g

(V)

E_LUMO(eV) E_HOMO(eV) λ_max(nm)

5i

–0.10

–0.01

–0.10

–0.12

–0.09

–0.08

*

–4.7

–4.8

–4.7

*

961

870

965

971

964

961

50000

41000

48000

45000

*

1.12

1.25

1.12

1.13

5j

5k

5l

10.10

11.10

11.8

CV

3

opt

[a] *: not workable. [b] E_1/2³: half-wave potential of couple 3. [c] E_1/2³: half-wave potential of couple 3. [d] E_g= E_1/2– E_1/2². [e] E_g

= hc/λ_onset

.

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Discotic Nickel Bis(dithiolene) Complexes

and its regioisomer 5j are shown in Figure 3. These com- tronic devices. Thermal analysis studies show that neutral

plexes have a maximum absorption peak in the near-infra- nickel bis(1,2-dithiolene) complexes are stable up to 300 °C

red spectral region, which can be attributed to a π–π* tran- as observed in Figure 4 for octadecyloxy-substituted com-

sition of the nickel bis(1,2-dithiolene) core.

plex 5i. At higher temperature, decomposition of the prod-

uct is observed, in accordance with data reported in the

literature.^[12,25]

Figure 4. Weight loss with temperature in 5i. Scan rate: 10 °Cmin^–1.

Figure 3. UV, visible, and NIR absorption spectra of 5a, 5i, and 5j

The phase behaviors of 5a–5l and of the three mixtures

10.10, 11.10, and 11.8 were studied by differential scanning

calorimetry (DSC), polarized optical microscopy (POM),

and powder X-ray diffraction. For calorimetry experiments,

all pristine samples were heated from ambient temperature

until they melted into their isotropic liquid (IL) phase and

subsequently cooled down. The heating–cooling cycles were

generally repeated twice with a scan rate of 10 °Cmin^–1.

in dichloromethane.

By comparison of the λ_maxand optical band gap values

for the octasubstituted 5i, 5k, and 5l with those of the tetra-

substituted 5a, we observe that increasing the number of

the side-chain substituent in [Ni(dpedt)₂] results in a small

redshift (ca. 30 nm). In compounds 5i and 5j, the change of

the position of the two n-decyloxy chains on the phenyl

rings from “3,4” (in 5i) to “3,5” (in 5j) induces a blueshift

of about 100 nm, their optical band gap moderately chang-

ing from 1.12 (5i) to 1.25 eV (5j). The electrochemical and

optical properties of three mixtures, 10.10, 11.10, and 11.8,

have also been studied (See Table 3). Their properties are

similar to those of their parent complexes 5i, 5k, and 5l.

Interestingly, electrochemical and optical measurements

show that the size, as well as the configuration or number

of alkoxy chains attached to dpedt ligands, do not influence

significantly the electronic properties of these alkoxy-substi-

tuted [Ni(dpedt)₂] compounds. Therefore, we can tune the

Tetraalkoxy-Substituted Complexes and Related

Compounds

The multiphase transition behavior of 5a, both on heat-

ing and cooling (see Figure S3 in the Supporting Infor-

mation), is in good accordance with reported data.^[22]In

Table 4. Phase transition (T) and enthalpy changes (ΔH), during

the second scan, of the tetraalkoxy-substituted complexes and re-

nature of the side chains to obtain mesomorphic properties lated compounds (scan rate: 10 °Cmin^–1).

without a major change in the electronic properties. Mean-

while, the halogenations of the dithiolene ligand, the con-

necting groups, and the relative positions of the alkoxy

chains have moderate influence on the properties of target

compounds. Generally, all the synthesized [Ni(dpedt)₂] de-

rivatives present LUMO and HOMO energy levels around

4.7–5.0 and 5.7–6.1 eV, respectively, depending on the func-

tional groups on the dithiolene ligands. Additionally, the

high molar absorption coefficient (ε) values range from

30000 to 55000 Lcm^–1mol^–1, demonstrating that these

[Ni(dpedt)₂] derivatives are efficient NIR absorbent materi-

als. For all complexes, the optical and electrochemical data

are in good accordance.

Phase Behavior with Temperature

Good thermal stability of targeted compounds is re-

quired to envisage their use as active layers in optoelec-

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B. Garreau-de Bonneval, K. I. Moineau-Chane Ching et al.

FULL PAPER

the present work, 5a has not been further studied. The in- chains are replaced in 5l by 2-ethylhexyl chains, used for

troduction of halogen atoms, either bromine or iodine, instance on arene tetraesters to very efficiently generate

strongly influences the phase behavior towards a simpler mesomorphic behavior,^[27]no liquid-crystalline phase is ob-

phase sequence relative to that in 5a, as reported in Table 4. served. Only a melting transition is seen on heating,

However, complementary POM studies reveal a direct crys- whereas the compound remains in a glassy isotropic state

tal-to-isotropic-liquid phase transition, showing that none on cooling down. Within discotic octaalkoxy-substituted

of these halogenated complexes exhibits liquid crystalline [Ni(dpedt)₂] molecules, the introduction of that kind of

properties.

bulky group does not induce mesomorphic properties. This

could arise from the fact that two alkoxy chains on the

same phenyl ring (at position “4” or “5”) of the dpedt li-

gand are too close, and they therefore disturb the planar

shape of the discotic molecules. We have then studied the

influence of two alkoxy chain positions on the same phenyl

ring of the dpedt ligand in 5i and 5j. In 5j, the two aliphatic

chains are far enough for a free rotation of the molecules

and an optimized self-organization to be expected. How-

ever, DSC and POM studies do not reveal any mesophase

in 5j. When the thermal behaviors of 5j, 5k, and 5l are com-

pared with that of the columnar liquid crystal (CLC) 5i,

one can conclude that the mesomorphic properties of oc-

taalkoxy-substituted [Ni(dpedt)₂] are very sensitive to their

detailed chemical structure. The replacement of linear alkyl

chains by branched ones or the modification of the position

of the alkoxy chain on the phenyl ring of the dpedt ligand

changes the melting temperature but does not favor the es-

tablishment of a mesophase.

Octaalkoxy-Substituted [Ni(dpedt)₂]

Prior to our work, only the liquid-crystalline property of

5i has been reported, and our structural investigations con-

firm the described results.^[17,23,26](see Supporting Infor-

mation Figures S4, S5, and S6). None of the other octaal-

koxy-substituted nickel bis(dithiolene) complexes have ever

been described before this present work. A considerable

change of the phase behavior of the new complexes is evi-

denced, which depends on the nature and configuration of

the side alkoxy chain (see Table 5).

Table 5. Phase transition (T) and enthalpy changes (ΔH), during

the second scan, of the octaalkoxy-substituted complexes and re-

lated compounds (scan rate: 10 °Cmin^–1).

Mixtures of Octaalkoxy-Substituted [Ni(dpedt)₂]

Differential scanning calorimetry analysis of the three

mixtures of octaalkoxy-substituted [Ni(dpedt)₂] suggests

that 10.10, 11.10, and 11.8 probably exhibit liquid-crystal-

line phases. Only the results for 11.8 are presented here,

whereas 10.10 and 11.10 will not be further studied in the

present work.

In Figure 5, after the first thermal cycle where a peak

exhibiting a high enthalpy characteristic of the fusion of a

crystal can be seen, two other peaks with a small enthalpy

are observed, the first one of which can be attributed to a

transition to liquid-crystalline phases and the second one

to a partial crystallization of the compound at low tempera-

ture. Further investigations by POM are shown in Figure 6,

where typical optical images of 11.8 at different tempera-

tures are given. After cooling down from the isotropic li-

quid phase, densely branched dendrites grow at T = 84 °C

without birefringence, which is characteristic of a hexagonal

CLC mesophase in homeotropic orientation. This optically

The replacement of the n-decyl group by the branched isotropic dendritic texture (in coexistence with some bire-

decyl chain 3,7-dimethyloctyl results in 5k. The behavior of fringent topological defects) is present down to ambient

5k differs from that of 5i in the following way: On heating temperature after a slow cooling process (Figure 6B). Con-

from ambient temperature, the pristine black paste-like trary to the calorimetry study, where a phase transition oc-

powder of 5k directly melts into an isotropic liquid phase curs at T = 40 °C, no phase transition to another phase is

at about 50 °C. On cooling down, the recrystallization peak evidenced by optical microscopy: the hexagonal columnar

is recorded at approximately 25 °C, and no mesophase is mesophase remains in a metastable state at room tempera-

detected. The use of the bulky 3,7-dimethyloctyl group in- ture. However, after a few hours, a new birefringent phase

fluences the molecular packing and decreases the melting appears (Figure 6C and D). The nature of this new phase

point dramatically from approximately 110 °C (for 5i), to is ambiguous, and it is difficult to say whether it is a liquid

approximately 50 °C (for 5k). Even when the linear decyl crystal or a pure crystal.

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Eur. J. Inorg. Chem. 2011, 2663–2676

Discotic Nickel Bis(dithiolene) Complexes

Figure 5. Differential scanning calorimetry (DSC) thermogram of

11.8, which shows, after the first heating, typical peaks characteris-

tic of mesophases on both heating and cooling (see data in Table 5).

Scan rate: 10 °Cmin^–1.

Figure 6. Optical microscopy for 11.8, in transmission with slightly

uncrossed polarizers, observed at 84 °C (A) with the dendritic

Nevertheless, DSC analysis shows that, after cooling

down slowly to ambient temperature in two days, the fusion growth of the hexagonal columnar mesophase in homeotropic ori-

entation, and at 28 °C (B), just after the cooling down from the

peak at 57 °C, which is attributed to the melting of the crys-

isotropic liquid phase. (C) Observation after one day at room tem-

talline phase into the liquid crystal phase, reappears (data

perature where a birefringent crystalline phase has nucleated, which

finally covers all the sample area (D). Each image size is 660 μm

not shown). This confirms that the liquid crystal is metasta-

ble at ambient temperature and slowly recrystallizes. X-ray

diffraction experiments have been performed at 70 °C and

are presented in Figure 7. The X-ray pattern at T = 70 °C

exhibits both a clear sixfold symmetry and many Bragg

peaks (100, 110, 200, 210), whose positions in reciprocal

ϫ490 μm.

Conclusions

This work is devoted to new short and efficient synthetic

space relative to the position of the first reflection are pathways of discotic nickel bis(dithiolene) complexes. The

¯

1:√3:√4:√7. This corresponds to the signature for 11.8 of electrochemical, optical, and thermal properties of these

the hexagonal columnar liquid-crystalline phase.^[4]The sig- complexes show that all these compounds absorb efficiently

nal of the disordered aliphatic chains corresponds to the in the near infrared spectral domain, according to a mea-

broad reflection at about 14 nm^–1, characteristic of a liquid- sured band gap of around 1 to 1.1 eV. Their electrochemical

like order.

and optical properties can be only moderately tuned, de-

This interesting finding opens new ways to form ambient pending on the nature and position of the functional groups

temperature CLCs based on nickel bis(dithiolene) com- attached to the phenyl rings. The octadecyloxy-substituted

plexes. As the synthesis of pure nickel bis(dithiolene) disco- complex 5i and the mixture 11.8 present an interesting hex-

tic liquid crystals (DLC) is very delicate, the formulation agonal columnar liquid-crystalline mesophase. However,

of different nickel complexes seems to be a very promising this mesophase is metastable at ambient temperature. The

direction.

possibility of stabilization of such mesophases by chemical

Figure 7. X-ray diffraction pattern (left) of a single domain of 11.8 probed at 70 °C, which exhibits Bragg peaks characteristic of a

hexagonal columnar mesophase (right).

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2671

B. Garreau-de Bonneval, K. I. Moineau-Chane Ching et al.

FULL PAPER

with a homemade heating stage with a thermal stability of Ϯ0.1 °C.

The spectra were recorded with a bidimensional detector located

at 180 mm from the sample, which was in the geometry of an open

supported droplet.

engineering or by mixing appropriate ligands is a crucial

point for their use in organic electronics and will be further

investigated.

Material Synthesis

Experimental Section

4,4Ј-Bis(decyloxy)benzil (2a): A mixture of 4,4Ј-dihydroxybenzil

(1a) (3 g, 12.39 mmol), decyl bromide (6.15 mL, 29.73 mmol), and

powdered potassium carbonate (5.14 g, 37.17 mmol) was stirred

overnight in DMF (75 mL) at 100 °C. Upon cooling to ambient

temperature, the reaction was quenched by adding water, and the

resulting mixture was extracted with dichloromethane. The organic

phases were combined, rinsed several times with water, dried with

anhydrous magnesium sulfate, and concentrated under reduced

pressure. The resulting crude product was purified by silica gel col-

umn chromatography (hexane/dichloromethane, 50:50) to provide

General Remarks

All used chemicals and solvents were purchased from chemical

companies and used as received, unless otherwise mentioned. All

reactions were performed in an ambient atmosphere of air unless

indicated otherwise. Purification of products was performed by col-

umn 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 chromatography, “60 F254”

substrates coated with silica gel from Merck were used.

¹H and ¹³C NMR spectroscopic experiments were recorded in the

listed deuteriated solvents (internal standard) with 4 Bruker Spec-

trometers (ARX 250, DPX 300, Avance 300 and Avance 400). The

multiplicity of the NMR signal is denoted as br (broad), m (mul-

tiplet), s (singlet), d (doublet), t (triplet), quart (quartet), quint

(quintet), sext (sextet), sept (septet), dd (double doublet), and dt

(double triplet).

1

a yellowish solid (6.35 g, 98%). H NMR (300 MHz, CD₂Cl₂): δ =

7.94 (dt, J = 2.7–9.0 Hz, 4 H, aromatic H), 7.01 (dt, J = 2.7–9.0 Hz,

4 H, aromatic H), 4.08 (t, J = 6.3 Hz, 4 H, -OCH₂-), 1.84 (quint,

J = 6.6 Hz, 4 H, -OCH₂CH₂-), 1.52–1.32 (m, 28 H), 0.92 (t, J =

6.3 Hz, 6 H, -CH₃) ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ = 193.55,

164.58, 132.17, 126.00, 114.68, 68.58, 31.90, 29.54, 29.31, 29.00,

25.89, 22.68, 13.88 ppm. MS (CI-NH₃): found 523.4 [M]⁺, 540.4

[M + NH₄]⁺.

Mass spectrometric analyses were performed at the Service de Spec-

trométrie de Masse de la Structure Fédérative Toulousaine en Chi-

mie Moléculaire. Elemental analyses (C, H, S, Ni) were carried out

on the nickel complexes at the Service Central d’Analyse du CNRS

in Lyon.

4,4Ј-Bis(decanoate)benzil (2b): A THF (50 mL) solution of 4,4Ј-di-

hydroxy benzil (2 g, 8.26 mmol), PPh₃(5.2 g, 19.82 mmol), and dec-

anoic acid (3.4 g, 19.82 mmol) was cooled to 0 °C. To the solution

was added diethyl azodicarboxylate in toluene solution (9 mL,

19.82 mmol, 40% w/v), the mixture was kept at that temperature

for 1 h and then was warmed to room temperature and stirred for

1 h. The reaction mixture was then concentrated. After addition of

hexane (500 mL), the mixture was filtered. The filtrate was concen-

trated, and the residue was purified by silica gel column chromatog-

raphy (hexane/dichloromethane, 25:75) to give a pure yellow solid

(4.25 g, 93%). ¹H NMR (300 MHz, CD₂Cl₂): δ = 8.06 (dt, J = 2.4–

9.3 Hz, 4 H, aromatic H), 7.31 (dt, J = 2.4–9.3 Hz, 4 H, aromatic

H), 2.63 [t, J = 7.5 Hz, 4 H, -OC(=O)CH₂-], 1.79 [m, 4 H, -OC-

(=O)CH₂CH₂-], 1.49–1.30 (m, 24 H), 0.94 (t, J = 6.6 Hz, 6 H,

-CH₃) ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ = 192.91, 171.42,

156.09, 131.51, 130.29, 122.44, 34.27, 31.88, 29.42, 29.26, 29.25,

29.03, 24.75, 22.68, 13.89 ppm. MS (CI-NH₃): found 568.3 ([M +

NH₄]⁺).

Phase transition was determined by differential scanning calorime-

try (DSC) thermograms, which were obtained with a DSC 204

NETZSCH system by using 2–5 mg samples in 30 μL sample pans

and a scan rate of 10 °Cmin^–1. ΔH is the enthalpy associated with

each phase transition, calculated in kJmol^–1.

Voltammetric measurements were carried out with a potentiostat

Autolab PGSTAT100 controlled by GPES 4.09 software. Experi-

ments were performed at room temperature in a homemade airtight

three-electrode cell connected to a vacuum/argon line. The refer-

ence electrode consisted of a saturated calomel electrode (SCE) sep-

arated from the solution by a bridge compartment. The countere-

lectrode was a platinum wire of ca 1 cm²apparent surface. The

working electrode was a Pt microdisk (0.5 mm diameter) or a glassy

carbon (1 mm diameter) electrode. The supporting electrolyte

(nBu₄N)[PF₆] (Fluka, 99% electrochemical grade) was used as re-

ceived after being simply degassed under argon. Dichloromethane

was freshly distilled from CaH₂prior to use. The solutions used

during the electrochemical studies were typically 10^–3molL^–1in

complex compound and 0.1 molL^–1in supporting electrolyte. Be-

fore each measurement, the solutions were degassed by bubbling

Ar through them, and the working electrode was polished with a

polishing machine (Presi P230).

3-Bromo-4,4Ј-bis(decyloxy)benzil (2c):

A suspension of FeCl₃

(0.28 g, 1.72 mmol) and 4,4Ј-didecyloxybenzil (2a) (0.9 g,

1.72 mmol) in dichloromethane (30 mL) was cooled to 0 °C. To the

suspension was added Br₂(0.2 mL, 3.93 mmol), and the mixture

was allowed to reach ambient temperature overnight. The reaction

was quenched by a 10% aqueous solution of Na₂S₂O₃(50 mL) and

then extracted with dichloromethane. The organic phases were

combined, rinsed several times with water, dried with anhydrous

magnesium sulfate, and concentrated under reduced pressure. The

resulting crude product was purified by silica gel column

chromatography (hexane/dichloromethane, 40:60 then 60:40) to

provide a yellowish solid of 2c (0.51 g, 49%) and 2d (0.26 g, 21%).

UV/Vis/NIR absorption spectra were recorded with two spectrome-

ters, Perkin–Elmer Lambda 35 and Perkin–Elmer GX 2000, by

using dichloromethane as solvent. The concentration of complex

in solutions used for the electronic absorption analyses was typi-

cally about 10^–5molL^–1.

1

For 2c: H NMR (250 MHz, CD₂Cl₂): δ = 8.22 (d, J = 2.1 Hz, 1

H, aromatic H), 7.94 (m, 3 H, aromatic H), 7.90 (dt, J = 2.8–

9.8 Hz, 3 H, aromatic H), 4.16 (t, J = 6.3 Hz, 2 H, -OCH₂-), 4.09

(t, J = 6.5 Hz, 2 H, -OCH₂-), 1.87 (m, 4 H, -OCH₂CH₂-), 1.55–1.44

(m, 28 H), 0.93 (6 H, -CH₃) ppm. ¹³C NMR (62.5 MHz, CD₂Cl₂): δ

= 192.70, 192.39, 164.77, 160.61, 134.68, 132.27, 131.45, 126.91,

125.71, 114.75, 112.64, 112.30, 69.78, 68.64, 31.89, 29.51, 29.30,

29.22, 28.98, 28.80, 25.87, 25.83, 22.67, 13.86 ppm. MS (CI-NH₃):

Optical observations were performed with a polarizing microscope

(Olympus, BX51), combined with both a color CCD camera (JAI,

CV-M7) and a heating stage (Mettler, FP90) with a temperature

accuracy of Ϯ0.1 °C.

X-ray diffraction experiments were performed by using a Rigaku

rotating anode generator having a wavelength of 1.54 Å together

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Discotic Nickel Bis(dithiolene) Complexes

found 601.3 [MBr⁷⁹+ H]⁺, 603.3 [MBr⁸¹+ H]⁺, 618.3 [MBr⁷⁹

NH₄]⁺, 620.3 [MBr⁸¹+ NH₄]⁺.

+

1054.9966 for [M + C₂H₅]⁺; found 1026.9668 and 1054.9985,

respectively.

3,3Ј-Dibromo-4,4Ј-bis(decyloxy)benzil (2d): To a solution of 4,4Ј-

didecyloxybenzil (2a) (1.5 g, 2.87 mmol) in a mixture of dichloro-

methane (25 mL) and acetonitrile (25 mL) were added Br₂

(0.73 mL, 14.35 mmol) and FeCl₃(0.93 g, 5.74 mmol). The mixture

was heated at reflux overnight (ca. 16 h). The reaction was

quenched by a 10% aqueous solution of Na₂S₂O₃(200 mL) and

then extracted with dichloromethane. The organic phases were

combined, rinsed several times with water, dried with anhydrous

magnesium sulfate, and concentrated under reduced pressure. The

resulting crude product was purified by silica gel column

chromatography (hexane/dichloromethane, 50:50) to provide a yel-

General Procedure for the Synthesis of 1,2-Dialkyloxybenzenes 3a,

3b, 3d, and 3e: A mixture of 1,2-benzenediol (1.0 equiv.), alkyl bro-

mide (2.4 equiv.), and powdered potassium carbonate (3.0 equiv.)

was stirred in dimethylformamide at 90 °C. The reaction was moni-

tored by TLC (hexane/ethyl acetate: 95:5 v/v). Upon being cooled

to ambient temperature, the reaction was quenched by adding

water, and the resulting mixture was extracted with dichlorometh-

ane. The organic phases were combined, rinsed several times with

water, dried with anhydrous magnesium sulfate, and concentrated

under reduced pressure. The crude products were then purified by

column chromatography (hexane/ethyl acetate).

1,2-Didecyloxybenzene (3a): White solid (3.6 g, yield 77%). ¹H

NMR (300 MHz, CD₂Cl₂): δ = 6.91 (s, 4 H, aromatic H), 4.00 (t,

J = 6.6 Hz, 4 H, -OCH₂-), 1.86–1.32 (m, 32 H, -CH₂-), 0.92 (t, J

= 6.9 Hz, 6 H, -CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ =

149.29, 121.02, 114.15, 69.29, 31.95, 29.68, 29.63, 29.48, 29.39,

26.10, 22.72, 14.13 ppm. GC–MS: found 390 [M]⁺.

1

lowish solid (1.83 g, 94%). H NMR (300 MHz, CDCl₃): δ = 8.22

(d, J = 2.1 Hz, 2 H, aromatic H), 7.90 (dd, J = 2.1–8.4 Hz, 2 H,

aromatic H), 6.96 (d, J = 8.4 Hz, 2 H, aromatic H), 4.13 (t, J =

6.6 Hz, 4 H, -OCH₂-), 1.88 (m, 4 H, -OCH₂CH₂-), 1.57–1.29 (m,

28 H), 0.89 (t, J = 6.6 Hz, 6 H, -CH₃) ppm. ¹³C NMR (75 MHz,

CDCl₃): δ = 191.46, 160.74, 135.02, 131.55, 126.67, 113.00, 112.16,

69.69, 31.89, 29.51, 29.30, 29.23, 28.79, 25.86, 22.68, 14.11 ppm.

MS (CI-NH₃): found 696.3 [MBr⁷⁹Br⁷⁹+ NH₄]⁺, 698.3 [MBr⁷⁹Br⁸¹

+ NH₄]⁺, 700.3 [MBr⁸¹Br⁸¹+ NH₄]⁺.

1,2-Bis(2-ethylhexyloxy)benzene (3b): Colorless liquid (7.35 g, yield

1

81%). H NMR (250 MHz, CD₂Cl₂): δ = 6.93 (m, 4 H, aromatic

H), 3.92 (d, J = 5.8 Hz, 4 H, -OCH₂-), 1.84–1.73 (m, 2 H,

-OCH₂CH-), 1.62–1.39 (m, 16 H, -CH₂-), 1.00 (t, J = 7.5 Hz, 12

H, -CH₃) ppm. ¹³C NMR (62.5 MHz, CD₂Cl₂): δ = 149.68, 120.77,

113.89, 71.58, 39.70, 30.59, 29.14, 23.91, 23.10, 13.86, 10.95 ppm.

HRMS (CI-NH₃): calcd. for [M + H]⁺335.2950; found 335.2948.

General Procedure for the Synthesis of 2e–2g: To a round-bottomed

flask were added 4,4Ј-didecyloxybenzil (2a) (1.54 g, 2.95 mmol),

TFA (35 mL), and NIS (2.0, 3.0, or 5.0 molar equivalents for 2e,

2f, and 2g, respectively). After stirring for 5 min at ambient tem-

perature, the reaction mixture was heated at reflux for 3.5 h. The

mixture was cooled to ambient temperature overnight and was

poured into ice water (300 mL), then dichloromethane (200 mL)

was added. The organic layers were separated, and the aqueous

phase was extracted with dichloromethane. The combined organic

phase was washed with a 10% aqueous solution of Na₂S₂O₃and

dried with MgSO₄. Removal of solvent in vacuo followed by silica

gel column chromatography (hexane/dichloromethane) provided

the desired products.

1

1,2-Diundecyloxybenzene (3d): White solid (45.9 g, yield 97%). H

NMR (250 MHz, CD₂Cl₂): δ = 6.93 (m, 4 H, aromatic H), 4.02 (t,

J = 6.6 Hz, 4 H, -OCH₂-), 1.81 (m, 4 H, -OCH₂CH₂-), 1.55–1.35

(m, 32 H, -CH₂-), 0.95 (t, J = 6.2 Hz, 6 H, -CH₃) ppm. ¹³C NMR

(62.5 MHz, CD₂Cl₂): δ = 149.35, 120.92, 114.12, 69.23, 31.96,

29.68, 29.48, 29.47, 29.40, 26.10, 22.72, 13.90 ppm. MS (CI-NH₃):

found 436.3 [M + NH₄]⁺.

1,2-Dioctyloxybenzene (3e): Colorless oil (13.47 g, yield 90%). ¹H

NMR (300 MHz, CD₂Cl₂): δ = 6.94 (m, 4 H, aromatic H), 4.03 (t,

J = 6.6 Hz, 4 H, -OCH₂-), 1.90 (m, 4 H, -OCH₂CH₂-), 1.60–1.38

(m, 20 H, -CH₂-), 1.00–0.95 (m, 6 H, -CH₃) ppm. ¹³C NMR

(75 MHz, CD₂Cl₂): δ = 149.36, 120.94, 114.11, 69.22, 31.91, 29.49,

29.47, 29.36, 26.13, 22.73, 13.92 ppm. HRMS (CI-CH₄): calcd. for

[M + H]⁺335.2950; found 335.2948.

3,3Ј-Diiodo-4,4Ј-bis(decyloxy)benzil (2e): Yellowish solid (2.24 g,

1

88%). H NMR (300 MHz, CDCl₃): δ = 8.41 (d, J = 2.1 Hz, 2 H,

aromatic H), 7.90 (dd, J = 2.1–8.4 Hz, 2 H, aromatic H), 6.83 (d,

J = 8.7 Hz, 2 H, aromatic H), 4.10 (t, J = 6.3 Hz, 4 H, -OCH₂-),

1.86 (m, 4 H, -OCH₂CH₂-), 1.55–1.27 (m, 28 H), 0.88 (t, J =

6.6 Hz, 6 H, -CH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 191.31,

162.74, 141.26, 132.56, 127.36, 111.08, 87.09, 69.81, 31.91, 29.52,

29.31, 29.22, 28.81, 25.96, 22.69, 14.13 ppm. MS (CI-NH₃): found

775.2 [M + H]⁺, 792.2 [M + NH₄]⁺.

1,2-Bis(3,7-dimethyloctyloxy)benzene (3c): A THF (50 mL) solution

of pyrocathecol (1.5 g, 6.2 mmol), PPh₃(3.9 g, 14.9 mmol), and

alcohol (14.9 mmol) was cooled to 0 °C. To the solution was added

diethyl 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 warmed to room temperature and stirred for 1 h. The

reaction mixture was then concentrated. After addition of hexane

(300 mL), the mixture was filtered. The filtrate was concentrated,

and the residue was purified by silica gel column chromatography

(eluent: hexane/dichloromethane, 1:1 v/v) to provide a colorless oil

3,3Ј,4-Triiodo-4,4Ј-bis(decyloxy)benzil (2f): White solid (1.14 g,

1

43%). H NMR (300 MHz, CDCl₃): δ = 8.40 (d, J = 2.1 Hz, 1 H,

aromatic H), 8.34 (s, 2 H, aromatic H), 7.91 (dd, J = 2.1–8.7 Hz,

1 H, aromatic H), 6.84 (d, J = 8.7 Hz, 1 H, aromatic H), 4.11 (t, J

= 6.3 Hz, 2 H, -OCH₂-), 4.03 (t, J = 6.6 Hz, 2 H, -OCH₂-), 1.50

(m, 4 H, -OCH₂CH₂-), 1.58–1.28 (m, 28 H), 0.88 (m, 6 H, -CH₃)

ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 190.10, 189.94, 163.44,

163.06, 141.54, 141.40, 132.69, 131.89, 126.86, 111.16, 91.54, 87.21,

73.99, 69.88, 31.90, 30.94, 30.04, 29.59, 29.52, 29.46, 29.34, 29.31,

29.22, 28.80, 25.95, 25.88, 22.69, 14.13 ppm. MS (CI-NH₃): found

901.1 [M + H]⁺, 918.1 [M + NH₄]⁺.

1

(3.95 g, yield 74%). H NMR (250 MHz, CDCl₃): δ = 6.93 (m, 4

H, aromatic H); 4.08 (m, 4 H, -OCH₂-); 1.95–1.14 (m, 20 H); 1.00–

0.91 (m, 18 H, -CH₃) ppm. ¹³C NMR (62.5 MHz, CD₂Cl₂): δ =

149.43, 133.89, 133.58, 128.74, 128.58, 128.47, 120.98, 114.11,

67.56, 39.37, 37.47, 36.49, 30.01, 28.09, 24.82, 22.59, 22.50, 19.57

ppm. HRMS (CI-CH₄): calcd. for [M + H]⁺391.3576; found

391.3584.

3,3Ј,4,4Ј-Tetraiodo-4,4Ј-bis(decyloxy)benzil(2g): Yellowish solid

1

(2.12 g, 59%). H NMR (300 MHz, CDCl₃): δ = 8.34 (s, 4 H, aro-

matic H), 4.04 (t, J = 6.6 Hz, 4 H, -OCH₂-), 1.94 (m, 4 H,

-OCH₂CH₂-), 1.60–1.28 (m, 28 H), 0.88 (t, J = 6.3 Hz, 6 H, -CH₃) General Procedure for the Synthesis of Tetraalkoxy-Substituted Ben-

ppm. ¹³C NMR (62.5 MHz, CDCl₃): δ = 188.81, 163.81, 141.66,

131.39, 91.65, 74.08, 31.91, 30.05, 29.59, 29.47, 29.34, 25.89, 22.71,

14.14 ppm. HRMS (CI-CH₄): calcd. 1026.9653 for [M + H]⁺and

zils (4a–4c): Solvents and glassware used in this synthesis were

dried thoroughly prior to use. To a 100 mL side-arm round-bot-

tomed flask under argon containing a solution of dialkyloxyben-

Eur. J. Inorg. Chem. 2011, 2663–2676

www.eurjic.org

2673

B. Garreau-de Bonneval, K. I. Moineau-Chane Ching et al.

FULL PAPER

zene (7.68 mmol) in 1,2-dichloroethane (30 mL), was added oxalyl

chloride (400μL, 4.61 mmol) by a microsyringe at 0 °C. The reac-

tion mixture was kept at 0 °C for 10 min, and then aluminum chlo-

ride (0.51 g, 3.84 mmol) was added. After 30 min at 0 °C, the mix-

ture was warmed gently to ambient temperature overnight. The

reaction mixture was then poured into an HCl solution (1 m). The

organic layer was separated, and the aqueous layer was extracted

twice with dichloromethane. The combined organic extracts were

dried with MgSO₄and concentrated. The residue was chromato-

graphed (hexane/dichloromethane) to give 5 as a pure product.

evaporated to give a yellowish brown viscous liquid (mass: 7.8 g).

This product was directly used in the next step without purification.

The mixture of crude 3,3Ј,5,5Ј-tetramethoxybenzoin (7.8 g), cop-

per(II) acetate (0.1 g, 0.24 mmol), NH₄NO₃(2.5 g, 29.35 mmol) in

acetic acid (20 mL) and water (5 mL) was heated at reflux. After

2 h of reflux, water was introduced, and the yellow precipitate was

collected by filtration. The filtrate was then extracted several times

with dichloromethane. The organic phases and the yellow precipi-

tate were combined, washed several times with water, dried with

MgSO₄, and the solvent was removed under reduced pressure. The

residue was purified by recrystallization from ethyl acetate to pro-

vide a yellow solid (2.0 g, yield 22%). ¹H NMR (250 MHz,

CD₂Cl₂): δ = 7.09 (d, J = 2.3 Hz, 4 H, aromatic H), 6.79 (t, J =

2.3 Hz, 2 H, aromatic H), 3.86 (s, 12 H, -OCH₃) ppm.

3,3Ј,4,4Ј-Tetra(decyloxy)benzil (4a): White solid (0.55 g, yield 51%).

¹H NMR (250 MHz, CD₂Cl₂): δ = 7.58 (d, J = 1.75 Hz, 2 H, aro-

matic H), 7.47 (dd, J = 2.0–8.5 Hz, 2 H, aromatic H), 6.94 (d, J =

8.25 Hz, 2 H, aromatic H), 4.10 (m, 8 H, -OCH₂-), 1.86 (m,

8 H, -OCH₂CH₂-), 1.52–1.33 (m, 56 H), 0.93 (t, J = 4.75 Hz, 12

H, -CH₃) ppm. ¹³C NMR (62.5 MHz, CD₂Cl₂) 193.81, 155.00,

149.32, 126.22, 126.13, 112.31, 111.61, 69.26, 69.14, 31.94, 29.65,

29.60, 29.41, 29.36, 29.10, 28.95, 26.01, 25.94, 22.71, 14.14. MS

(CI-NH₃): found 835.6 [M]⁺, 836.7 [M + H]⁺.

3,3Ј,5,5Ј-Tetradecyloxybenzil (4d): 3,3Ј,5,5Ј-tetramethoxybenzil

(1.05 g) was heated at reflux for 5 h in a mixture of aqueous HBr

(48%) and glacial acetic acid (100 mL, 50:50). The reaction mixture

was cooled in a bath of ice-water and extracted several times with

ethyl ether. The organic phases were combined, and the solvent was

removed under reduced pressure. The residue was analyzed by TLC

with a mixture of acetone and dichloromethane (50:50). Only one

product was observed. The residue was not purified but directly

used in the next step. To this residue were added decyl bromide

(4 mL), K₂CO₃(5.5 g), and dimethylformamide (40 mL), and the

mixture was heated at reflux for 18 h. The reaction mixture was

cooled in a bath of ice-water and extracted several times with

dichloromethane. The organic phases were combined, rinsed sev-

eral times with water, dried with MgSO₄, and the solvent was re-

moved under reduced pressure. The crude product was purified by

column chromatography (silica gel: hexane/dichloromethane,

50:50) to provide a yellow solid (1.41 g, yield 53%). ¹H NMR

(300 MHz, CD₂Cl₂): δ = 7.04 (d, J = 2.1 Hz, 4 H, aromatic H),

6.76 (t, J = 2.1 Hz, 2 H, aromatic H), 4.00 (t, J = 6.6 Hz, 8 H,

-OCH₂-), 1.79 (quint, J = 6.6 Hz, 8 H, -OCH₂CH₂-), 1.49–1.32 (m,

56 H), 0.92 (t, J = 6.3 Hz, 12 H, -CH₃) ppm. ¹³C NMR (75 MHz,

CD₂Cl₂): δ = 194.48, 160.71, 134.60, 107.95, 107.68, 104.46, 68.52,

68.34, 31.90, 29.55, 29.34, 29.31, 29.23, 29.18, 29.10, 25.94, 22.68,

13.87 ppm. MS (CI-NH₃): found 835.7 [M + H]⁺, 853.7 [M +

NH₄]⁺.

3,3Ј,4,4Ј-Tetra(2-ethylhexyloxy)benzil (4b): Yellowish oil (1.69 g,

yield 49%). ¹H NMR (300 MHz, CD₂Cl₂): δ = 7.58 (d, J = 2.1 Hz,

2 H, aromatic H), 7.45 (dd, J = 2.1–8.4 Hz, 2 H, aromatic H), 6.93

(d, J = 8.4 Hz, 2 H, aromatic H), 3.99 (d, J = 5.4 Hz, 8 H,

-OCH₂CH-), 1.80 (m, 4 H, -OCH₂CH-), 1.58–1.35 (m, 32 H), 1.00–

0.91 (m, 24 H, -CH₃) ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ =

193.95, 155.40, 149.70, 126.02, 125.83, 111.77, 111.37, 71.46, 71.37,

39.52, 39.40, 30.57, 30.49, 29.08, 29.03, 23.93, 23.92, 23.87, 23.85,

23.05, 23.02, 13.83, 13.81, 10.96, 10.91 ppm. HRMS (CI-CH₄):

calcd. for [M + H]⁺723.5564; found 723.5578.

3,3Ј,4,4Ј-Tetra(3,7-dimethyloctyloxy)benzil (4c): Yellowish oil

1

(1.58 g, yield 49%). H NMR (300 MHz, CD₂Cl₂): δ = 7.59 (d, J

= 2.1 Hz, 2 H, aromatic H), 7.47–7.42 (m, 2 H, aromatic H), 6.94

(m, 2 H, aromatic H), 4.16 (m, 8 H, -OCH₂-), 1.94–0.89 (m, 76 H)

ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ = 193.83, 155.06, 152.75,

149.36, 148.67, 130.67, 126.12, 125.89, 124.44, 114.49, 112.11,

111.56, 111.46, 67.60, 39.24, 39.21, 37.33, 37.28, 36.25, 36.10,

35.90, 29.96, 28.02, 24.74, 22.48, 22.38, 19.47, 19.41 ppm. HRMS

(CI-NH₃): calcd. for [M + H]⁺835.6816; found 835.6859.

General Procedure for the Synthesis of Benzil Mixtures B10.10,

B11.10, and 11.8: Solvents and glassware used in this synthesis were

dried thoroughly prior to use. To a 100 mL side-arm round-bot-

tomed flask under argon containing a solution of the first dialk-

oxybenzene (3.84 mmol) in 1,2-dichloroethane (20 mL) was added

oxalyl chloride (400 μL, 4.61 mmol) by a microsyringe at 0 °C. The

reaction mixture was kept at 0 °C for 10 min, and then aluminum

chloride (0.51 g, 3.84 mmol) was added. After 30 min at 0 °C, the

solution of the second dialkoxybenzene (3.84 mmol) in 1,2-dichlor-

oethane (20 mL) was added dropwise over a period of 30 min. The

mixture was then warmed gently to ambient temperature overnight.

The reaction mixture was then poured into an HCl solution (1 m).

The organic layer was separated, and the aqueous layer was ex-

tracted twice with dichloromethane. The combined organic extracts

were dried with MgSO₄and concentrated. The residue was chro-

matographed with a mixture of hexane and dichloromethane to

give a mixture of benzils B10.10 (1.77 g, yellow solid), B11.10

(1.71 g, yellow solid), and B11.8 (4.65 g, yellow solid).

General Procedure for the Synthesis of Nickel Bis(1,2-dithiolene)

Complexes and Mixtures of Nickel Complexes: A mixture of dialk-

oxybenzil (4.91 mmol) and P₄S₁₀(4.8 g, 10.80 mmol) in dioxane

(25 mL) was heated to reflux at 130 °C 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 NiCl₂·6H₂O (0.64 g, 2.70 mmol)

in water (5 mL), 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 re-

peated precipitation from solution in dichloromethane by using

ethanol (3 times), and the final purification was performed by col-

umn chromatography (hexane/dichloromethane).

Nickel Bis[1,2-bis(4-decyloxyphenyl)ethene-1,2-dithiolene] Complex

(5a): Brown solid (1.6 g, yield 70%). C₆₈H₁₀₀NiO₄S₄(1168.48):

calcd. C 69.90, H 8.63, S 10.98; found C 69.22, H 8.72, S 10.62.

¹H NMR (300 MHz, CD₂Cl₂): δ = 7.37 (dt, J = 3.0–9.6 Hz, 8 H,

aromatic H), 6.86 (dt, J = 3.0–9.6 Hz, 8 H, aromatic H), 4.00 (t, J

= 6.6 Hz, 8 H, -OCH₂-), 1.82 (quint, J = 6.6 Hz, 8 H, -OCH₂CH₂-),

1.51–1.33 (m, 56 H), 0.92 (t, J = 6.6 Hz, 12 H, -CH₃) ppm. ¹³C

NMR (75 MHz, CD₂Cl₂): δ = 180.73, 160.08, 134.10, 130.31,

114.28, 68.20, 31.89, 29.57, 29.55, 29.37, 29.31, 29.19, 25.97, 22.67,

3,3Ј,5,5Ј-Tetramethoxybenzil (4e): Sodium cyanide (1.0 g,

22.4 mmol) was dissolved in water (10 mL). To this solution were

added 3,5-dimethoxybenzaldehyde (9.3 g, 56.0 mmol) and ethanol

(20 mL of ). The mixture was heated at reflux with stirring for 36 h,

extracted with dichloromethane, and the organic layer was washed

with water, and then dried with MgSO₄. The dichloromethane was

2674

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Eur. J. Inorg. Chem. 2011, 2663–2676

Discotic Nickel Bis(dithiolene) Complexes

13.86 ppm. HRMS (CI-CH₄): calcd. for [M]⁺1166.5858; found

1166.5695.

Nickel Bis[1,2-bis(4-decanoylphenyl)ethene-1,2-dithiolene] Complex

(5g): Green solid (0.4 g, yield 10%). C₆₈H₉₂NiO₈S₄(1224.42):

calcd. C 66.70, H 7.57, S 10.48; found C 66.28, H 7.88, S 10.74.

¹H NMR (400 MHz, CD₂Cl₂): δ = 7.45 (dt, J = 2.8–9.6 Hz, 8 H,

aromatic H), 7.09 (dt, J = 2.8–9.6 Hz, 8 H, aromatic H), 2.60 [t, J

= 7.2 Hz, 8 H, -OC(=O)CH₂-], 1.77 [quint, J = 7.60 Hz, 8 H, OC-

(=O)CH₂CH₂-], 1.49–1.33 (m, 48 H), 0.93 (t, J = 6.8 Hz, 12 H,

-CH₃) ppm. ¹³C NMR (100 MHz, CD₂Cl₂): δ = 180.78, 171.77,

151.60, 138.43, 130.00, 121.81, 34.30, 31.86, 29.41, 29.25, 29.06,

24.83, 22.67, 13.86 ppm. HRMS (CI-CH₄): calcd. for [M + H]⁺

1223.5107; found 1223.5134.

Nickel Bis[1-(4-decyloxy-3-bromophenyl)-2-(4-decyloxyphenyl)eth-

ene-1,2-dithiolene] Complex (5b): Black solid (0.5 g, yield 76%).

C₆₈H₉₈Br₂NiO₄S₄(1326.27): calcd. C 61.58, H 7.45, S 9.67, Br

12.05; found C 61.81, H 7.46, S 10.89, Br 11.94. ¹H NMR

(400 MHz, CD₂Cl₂): δ = 7.72 (d, J = 2.4 Hz, 2 H, aromatic H),

7.36 (dt, J = 3.2–10 Hz, 4 H, aromatic H), 7.26 (dd, J = 2.4–8.8 Hz,

2 H, aromatic H), 6.86 (m, 6 H, aromatic H), 4.07 (t, J = 6.4 Hz,

4 H, -OCH₂-), 4.07 (t, J = 6.8 Hz, 4 H, -OCH₂-), 1.85 (m, 8 H,

-OCH₂CH₂-), 1.56–1.33 (m, 56 H), 0.93 (t, J = 6.8 Hz, 12 H, -CH₃)

ppm. ¹³C NMR (100 MHz, CD₂Cl₂): δ = 181.37, 178.57, 160.26,

156.12, 135.07, 133.64, 133.53, 130.37, 129.20, 114.43, 112.41,

111.90, 69.39, 68.27, 31.91, 29.58, 29.56, 29.39, 29.32, 29.18, 29.02,

25.99, 25.95, 22.68, 13.87 ppm. HRMS (CI-CH₄): calcd. for [M]⁺

1326.4039; found 1326.4076.

Nickel [1,2-Bis(4-decanoylphenyl)ethene-1,2-dithiolene][1-(4-decan-

oylphenyl)-2-(4-thiodecanoatephenyl)ethene-1,2-dithiolene] Complex

(5h) Isolated During the Synthesis of 5g: Green solid (70 mg).

C₆₈H₉₂NiO₇S₅(1240.48): calcd. C 65.84, H 7.48, S 12.92; found C

1

65.32, H 7.73, S13.94. H NMR (300 MHz, CD₂Cl₂): δ = 7.46 (m,

8 H, aromatic H), 7.05 (m, 8 H, aromatic H), 3.00 [t, J = 7.5 Hz,

2 H, -OC(=S)CH₂-], 2.59 [t, J = 7.5 Hz, 6 H, -OC(=O)CH₂-], 1.94

[quint, J = 7.5 Hz, 2 H, -OC(=S)CH₂CH₂-], 1.75 [quint, J = 7.8 Hz,

6 H, -OC(=O)CH₂CH₂-], 1.47–1.33 (m, 48 H), 0.94 (m, 12 H,

-CH₃) ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ = 181.03, 180.81,

180.42, 171.78, 155.12, 151.62, 139.13, 138.42, 138.31, 130.20,

130.06, 130.00, 122.34, 121.84, 46.77, 34.31, 31.88, 29.43, 29.27,

29.07, 24.84, 22.69, 13.88 ppm. HRMS (CI-CH₄): calcd. for [M +

H]⁺1239.4878; found 1239.4738.

Nickel

Bis[1,2-(4-decyloxy-3-bromophenyl)ethene-1,2-dithiolene]

Complex (5c): Black solid (1.1 g, yield 65%). C₆₈H₉₆Br₄NiO₄S₄

(1484.07): calcd. C 55.03, H 6.52, S 8.64, Br 21.54; found C 54.80,

H 6.59, S 8.41, Br 21.57. H NMR (300 MHz, CD₂Cl₂): δ = 7.71

(d, J = 2.7 Hz, 4 H, aromatic H), 7.18 (dd, J = 2.4–8.7 Hz, 4 H,

aromatic H), 6.76 (d, J = 8.7 Hz, 4 H, aromatic H), 4.06 (t, J =

6.3 Hz, 8 H, -OCH₂-), 1.88 (quint, J = 6.6 Hz, 8 H, -OCH₂CH₂-),

1.57–1.37 (m, 56 H), 0.93 (J = 6.6 Hz, 12 H, -CH₃) ppm. ¹³C NMR

(75 MHz, CD₂Cl₂): δ = 178.77, 156.17, 134.60, 133.53, 129.36,

112.39, 111.96, 69.41, 31.93, 29.58, 29.36, 29.35, 29.04, 25.97,

22.70, 13.90 ppm. MS (CI-CH₄): found 1483.43 [M]⁺.

1

Nickel

Bis[1,2-bis(3,4-di-n-decyloxyphenyl)ethene-1,2-dithiolene]

Complex (5i): Black green powder (0.1 g, yield 30%).

C₁₀₈H₁₈₀NiO₈S₄(1793.55): calcd. C 72.32, H 10.12; found C 72.70,

H 10.16. ¹H NMR (300 MHz, CD₂Cl₂): δ = 7.12 (dd, J = 2.1–

8.4 Hz, 4 H, aromatic H), 6.87 (s, 4 H, aromatic H), 6.85 (d, J =

2.1 Hz, 4 H, aromatic H), 4.04 (t, J = 6.6 Hz, 8 H, -OCH₂-), 3.80

(t, J = 6.6 Hz, 8 H, -OCH₂-), 1.84 (m, 8 H, -OCH₂CH₂-), 1.69 (m,

8 H, -OCH₂CH₂-), 1.56–1.32 (m, 112 H), 0.92 (m, 24 H, -CH₃)

ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ = 180.84, 150.24, 148.58,

134.36, 121.96, 114.40, 112.84, 69.17, 69.07, 31.94, 31.92, 29.70,

29.62, 29.60, 29.43, 29.39, 29.35, 29.26, 29.09, 26.03, 25.99, 22.69,

13.87 ppm. MS (FAB): found 1792 [M]⁺.

Nickel Bis[1,2-(4-decyloxy-3-iodophenyl)ethene-1,2-dithiolene] Com-

plex (5d): Black solid (2.16 g, yield 81%). C₆₈H₉₆I₄NiO₄S₄

(1672.07): calcd. C 48.85, H 5.79, S 7.67, I 30.36; found C 48.91,

H 5.67, S 8.35, I 29.73. ¹H NMR (300 MHz, CD₂Cl₂): δ = 7.96 (d,

J = 2.4 Hz, 4 H, aromatic H), 7.22 (dd, J = 2.4–8.7 Hz, 4 H, aro-

matic H), 6.72 (d, J = 8.7 Hz, 4 H, aromatic H), 4.06 (t, J = 6.3 Hz,

8 H, -OCH₂-), 1.88 (quint, J = 6.6 Hz, 8 H, -OCH₂CH₂-), 1.58–

1.33 (m, 56 H), 0.93 (m, 12 H, -CH₃) ppm. ¹³C NMR (75 MHz,

CD₂Cl₂): δ = 178.81, 158.42, 139.66, 135.26, 130.28, 111.27, 86.29,

69.55, 31.93, 29.58, 29.35, 29.33, 29.03, 26.05, 22.70, 13.90 ppm.

HRMS (CI-CH₄): calcd. for [M + H]⁺1671.1802; found 1671.1726.

Nickel

Bis[1,2-bis(3,5-di-n-decyloxyphenyl)ethene-1,2-dithiolene]

Complex (5j): Black powder (0.36 g, yield 28%). C₁₀₈H₁₈₀NiO₈S₄

(1793.55): calcd. C 72.32, H 10.12, S 7.15; found C 72.08, H 10.28,

S 7.17. H NMR (400 MHz, CD₂Cl₂): δ = 6.53 (d, J = 2.0 Hz, 4

Nickel

Bis[1-(4-decyloxy-3,5-diiodophenyl)-2-(4-decyloxy-3-iodo-

1

phenyl)ethene-1,2-dithiolene] Complex (5e): Black solid (0.85 g,

yield 55%). C₆₈H₉₄I₆NiO₄S₄(1923.86): calcd. C 42.45, H 4.92, S

6.67, I 39.58; found C 42.67, H 4.90, S 6.43, I 38.00. ¹H NMR

(400 MHz, CDCl₃): δ = 7.88 (J = 2.0 Hz, 2 H, aromatic H), 7.77

(s, 4 H, aromatic H), 7.20 (dd, J = 2.4–8.8 Hz, 2 H, aromatic H),

6.68 (d, J = 8.8 Hz, 2 H, aromatic H), 4.05 (t, J = 6.4 Hz, 4 H,

-OCH₂-), 4.02 (t, J = 6.8 Hz, 4 H, -OCH₂-),1.93 (quint, J = 6.8 Hz,

4 H, -OCH₂CH₂-), 1.86 (quint, J = 6.8 Hz, 4 H, -OCH₂CH₂-),

1.59–1.28 (m, 56 H), 0.89 (m, 12 H, -CH₃) ppm. ¹³C NMR

(100 MHz, CDCl₃): δ = 180.19, 176.12, 158.75, 158.68, 140.01,

139.89, 139.82, 134.37, 130.17, 111.36, 90.77, 86.73, 69.59, 31.93,

30.08, 29.63, 29.60, 29.54, 29.51, 29.36, 29.32, 28.97, 26.04, 25.98,

22.72, 14.14 ppm. MS (CI-CH₄): found 1923.8342 [M]⁺.

H, aromatic H), 6.47 (t, J = 2.0 Hz, 2 H, aromatic H), 3.82 (t, J =

6.8 Hz, 8 H, -OCH₂-), 1.68 (quint, J = 6.4 Hz, 8 H, -OCH₂CH₂-),

1.41–1.29 (m, 56 H), 0.88 (t, J = 6.8 Hz, 12 H, -CH₃) ppm. ¹³C

NMR (100 MHz, CD₂Cl₂): δ = 181.73, 160.09, 159.50, 142.68,

107.31, 106.72, 102.63, 68.30, 67.71, 31.92, 31.33, 29.62, 29.58,

29.35, 29.06, 29.03, 28.99, 28.76, 28.47, 25.96, 25.37, 22.69, 22.10,

13.89, 13.30 ppm. HRMS (CI-CH₄): calcd. for [M

1792.1993; found 1792.0989.

+

H]⁺

Nickel Bis[1,2-bis(3Ј,4Ј-bis(3,7-dimethyloctyloxy)phenyl)ethene-1,2-

dithiolene] Complex (5k): Black paste-like powder (0.44 g, yield

28%). C₁₀₈H₁₈₀NiO₈S₄(1793.55): calcd. C 72.32, H 10.12; found

1

C 72.40, H 10.18. H NMR (300 MHz, CD₂Cl₂): δ = 7.13 (dd, J =

2.0 Hz, 4 H, aromatic H), 6.87 (dd, J = 2.0–8.4 Hz, 8 H, aromatic

H), 4.06 (m, 8 H, -OCH₂-), 3.80 (m, 8 H, -OCH₂-), 1.95–0.90 (m,

152 H) ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ = 180.83, 150.23,

148.60, 134.34, 121.92, 114.23, 112.67, 67.47, 67.39, 39.25, 37.35,

36.18, 36.05, 29.98, 29.96, 28.00, 24.75, 24.71, 22.46, 22.37, 19.45,

19.32 ppm. HRMS (CI-CH₄): calcd. for [M + H]⁺1792.1993;

found 1792.1937.

Nickel Bis[1,2-(4-decyloxy-3,5-diiodomophenyl)ethene-1,2-dithiol-

ene] Complex (5f): Black solid (0.66 g, yield 30%). C₆₈H₉₂I₈NiO₄S₄

(2175.65): calcd. C 37.54, H 4.26, S 5.90, I 46.66; found C 37.94,

1

H 4.34, S 5.00, I 45.56. H NMR (400 MHz, CD₂Cl₂): δ = 7.80 (s,

8 H, aromatic H), 4.07 (t, J = 6.8 Hz, 8 H, -OCH₂-), 1.97 (quint,

J = 6.4 Hz, 8 H, -OCH₂CH₂-), 1.63–1.34 (m, 56 H), 0.93 (t, J =

6.8 Hz, 12 H, -CH₃) ppm. ¹³C NMR (100 MHz, CD₂Cl₂): δ =

177.70, 159.19, 140.10, 139.06, 90.70, 73.88, 31.93, 30.06, 29.62, Nickel Bis[1,2-bis(3Ј,4Ј-bis(2-ethylhexyloxy)phenyl)ethene-1,2-dithi-

29.51, 29.36, 25.95, 22.71, 13.89 ppm.

olene] Complex (5l): Black paste-like powder (0.56 g, yield 41%).

Eur. J. Inorg. Chem. 2011, 2663–2676

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B. Garreau-de Bonneval, K. I. Moineau-Chane Ching et al.

FULL PAPER

[10] F. G. Brunetti, X. Gong, M. Tong, A. J. Heeger, F. Wudl, An-

gew. Chem. Int. Ed. 2010, 49, 532–536.

C₉₂H₁₄₈NiO₈S₄(1569.12): calcd. C 70.42, H 9.51; found C 70.77, H

9.56. ¹H NMR (300 MHz, CD₂Cl₂): δ = 7.10 (dd, J = 2.1–8.4 Hz, 4

H, aromatic H), 6.86 (dd, J = 2.1–8.4 Hz, 8 H, aromatic H), 3.90

(d, J = 5.7 Hz, 8 H, -OCH₂-), 3.64 (d, J = 5.7 Hz, 8 H, -OCH₂-),

1.81–0.88 (m, 120 H) ppm. ¹³C NMR (75 MHz, CD₂Cl₂): δ =

180.89, 150.60, 148.97, 134.28, 121.83, 114.21, 112.55, 71.53, 71.37,

39.59, 39.33, 30.58, 30.52, 29.13, 29.01, 23.92, 23.81, 23.06, 13.85,

10.98, 10.88 ppm. HRMS (CI-CH₄): calcd. for [M]⁺1566.9563;

found 1566.9460.

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Three Mixtures of Octaalkoxy-Substituted Nickel Bis(dithiolene)

Complexes: 10.10: 0.77 g (black paste-like powder), 11.10: 0.66 g

(black paste-like powder), 11.8: 1.75 g (black paste-like powder).

Supporting Information (see footnote on the first page of this arti-

cle): CV and SWV data of the nickel complexes, DSC of com-

pounds 5a and 5i, POM images of compound 5i.

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Received: December 6, 2010

Published Online: March 25, 2011

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Article Doi

Discotic nickel bis(dithiolene) complexes - Synthesis, optoelectrochemical and mesomorphic properties

DOI: 10.1002/ejic.201001288

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