The near infra red (NIR) chiroptical properties of nickel dithiolene complexes

Article abstract of DOI:10.1039/c4nj01244e

Enantiomerically pure dianionic, monoanionic and neutral dithiolene complexes formulated as [Ni((R,R)-CHMePh-thiazdt)₂]^-2,-1,0 and [Ni((S,S)-CHMePh-thiazdt)₂]^-2,-1,0 (CHMePh-thiazdt: N-(1-phenylethyl)-1,3-thiazoline-2-thione-4,5-dithiolate) have been synthesized from the enantiopure N-(1-phenylethyl)-1,3-thiazoline-2-thione precursors. The electrochemical and spectro-electrochemical investigations carried out on these complexes show that the CHMePh-thiazdt ligands act as electron rich ligands and that the complexes are strong near infrared (NIR) absorbers in the range of 800-1100 nm for the neutral species and 1050-1500 nm for the reduced radical anion species. Circular dichroism (CD) thin layer spectro-electrochemical experiments carried out on the neutral (R,R) enantiomer, [Ni((R,R)-CHMePh-thiazdt)₂], revealed a redox switching of CD-active bands, not only in the UV-vis but also in the NIR region.

Full text of DOI:10.1039/c4nj01244e

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The near infra red (NIR) chiroptical properties of
nickel dithiolene complexes†
Cite this: New J. Chem., 2015,
39, 122
Yann Le Gal, Antoine Vacher, Vincent Dorcet, Marc Fourmigue, Jeanne Crassous
´
and Dominique Lorcy*
Enantiomerically pure dianionic, monoanionic and neutral dithiolene complexes formulated as
[Ni((R,R)-CHMePh-thiazdt)2]ꢀ2,ꢀ1,0 and [Ni((S,S)-CHMePh-thiazdt)2]ꢀ2,ꢀ1,0 (CHMePh-thiazdt: N-(1-phenylethyl)-
1,3-thiazoline-2-thione-4,5-dithiolate) have been synthesized from the enantiopure N-(1-phenylethyl)-
1,3-thiazoline-2-thione precursors. The electrochemical and spectro-electrochemical investigations carried
out on these complexes show that the CHMePh-thiazdt ligands act as electron rich ligands and that the
complexes are strong near infrared (NIR) absorbers in the range of 800–1100 nm for the neutral species and
1050–1500 nm for the reduced radical anion species. Circular dichroism (CD) thin layer spectro-
electrochemical experiments carried out on the neutral (R,R) enantiomer, [Ni((R,R)-CHMePh-thiazdt)2],
revealed a redox switching of CD-active bands, not only in the UV-vis but also in the NIR region.
Received (in Montpellier, France)
25th July 2014,
Accepted 11th September 2014
DOI: 10.1039/c4nj01244e
www.rsc.org/njc
attractive platform. Indeed, the thiazoline core offers the possi-
bility of numerous structural modifications which can be brought
Introduction
Nickel bis(dithiolene) complexes exhibit versatile and unique prop- about through the substituent on the nitrogen atom. Therefore,
erties, associated with different redox states, for potential applica- we decided to investigate the synthesis of a thiazoline core
tions in optics and electronics.1 For instance, these dithiolene bearing a chiral substituent and to use this chiral precursor
complexes are strong near infrared (NIR) absorbers in the range in the preparation of homoleptic dithiolene complexes of the
of 700–1400 nm, and this absorption range can be tuned not only by general formula [Ni(R*-thiazdt)2] (Chart 1), with a chiral center
the electron withdrawing or releasing ability of the ligand but also
by controlling the degree of oxidation of the complex.2 The intro-
duction of chirality into such metal dithiolene complexes has also
recently emerged,3 either to generate NIR chiro-optical effects4 or for
the possible observation, in conducting dithiolene salts,5 of elec-
trical magneto-chiral anisotropy,6 as recently reported in fully
organic conductors.7 Interestingly,4 the chirality of cholesterol sub-
stituents was transferred to the NIR response of the complexes only
in a gel supramolecular organisation, but was absent in the diluted
molecular complexes. It is therefore an important issue to be able to
introduce chirality in the close vicinity of NIR-absorbing square-
planar dithiolene complexes. In that respect, two strategies have
been essentially reported to prepare such chiral salts: either the
chirality is introduced by the counter-ion associated with the
anionic metal dithiolene complex5,8 or a chiral substituent is
covalently linked to the dithiolene ligand.3
Our current interest in metal dithiolene complexes involving
the N-alkyl-1,3-thiazoline-2-thione-4,5-dithiolate (R-thiazdt) ligand9–12
prompted us to investigate the synthesis of chiral ligands on this
´
Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS-Universite de Rennes 1,
ˆ
Campus de Beaulieu, Bat 10A, 35042 Rennes cedex, France.
E-mail: dominique.lorcy@univ-rennes1.fr
Chart 1 Examples of reported chiral dithiolene complexes3,4 and the
desired [Ni(R*-thiazdt)2] complex derived from 1-phenylethylamine.
† CCDC 1015857 and 1015858. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c4nj01244e
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very close to the two metallacycles. The enantiopure (R- or S-) and
racemic, commercially available 1-phenyl-ethylamine was chosen
here as a first proof of concept. Herein, we report the synthesis
of the enantiopure nickel dithiolene complexes together with
spectroscopic and electrochemical investigations in solution. The
X-ray crystal structures, magnetic properties as well as the
chiroptical properties will be also presented, demonstrating for
the first time a circular dichroism effect in the NIR region in
diluted solution.
Results and discussion
Syntheses
The dithiolene complexes were prepared either from the enan-
tiopure or the racemic mixture of 1-phenylethylamine according
to the chemical route described in Scheme 1. The (R)-, (S)- and
(R,S)-3-(1-phenylethyl)-1,3-thiazoline-2-thione 1 were prepared
13
¨
according to a modified procedure of Sandstrom. Addition of
carbon disulfide and triethylamine to a suspension of 1-phenyl-
ethylamine leads to the dithiocarbamate salt which reacts with
chloroacetaldehyde. Cyclization and dehydration in the presence
of sulfuric acid affords the 1,3-thiazoline-2-thione (R)-, (S)- and
rac-1 in 55% yield.14 In order to prepare the organic dithiolate
protected form of the ligand, the N(-1-phenylethyl)-4,5-bis-
(cyanoethylthio)-1,3-thiazoline-2-thione 3 where the two thiolates
are protected by cyanoethyl groups, we choose a two-step
approach. The first step consists in the formation of the dithio-
late which is trapped with ZnCl2 as described in Scheme 1.9b
Fig. 1 1H NMR spectra of the phenyl and the benzylic protons of (S)-3
(top) and the methyl and the cyanoethyl groups (bottom) at various
temperatures.
Subsequent reaction of this Zn salt 2 with 3-bromo-
propionitrile affords the organic dithiolate protected form 3.
Even if this route is longer than the direct formation of 3 from 1,
it allows an easier isolation of 3, thanks to the precipitation in
the first step of the Zn salt 2. It is worth mentioning that at
room temperature the 1H NMR spectra of (R)-, (S)- and rac-3
exhibit two broad unresolved signals, one for the C–H at
7.12 ppm (Fig. 1) and the other one at 2.22 ppm for the CH2
of one cyanoethyl chain. This is reminiscent of what was
observed for other N(-1-phenylethyl)-thiazoline-2-thione deriva-
tives where broad signals were attributed to the presence of two
rotamers designated as the rotamer syn and anti, depending on
the orientation of the smallest substituent (C–H) in the plane of
the thiazole ring (Chart 2).13,15 A temperature-dependent
1H NMR study in CDCl3 was carried out on (S)-3 from ambient
temperature to 223 K. Upon lowering the temperature, the
Scheme 1 Synthetic procedure of (R,R) and (S,S)-4.
Chart 2
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Table 1 Redox potentials for the Ni complexes in CH3CN with [NBu4][PF6]
0.1 M, E in V vs. SCE, v = 100 mV sꢀ1
broad signal observed at 7.12 ppm, for the C–H, becomes a
quadruplet at 233 K indicating that at this temperature one of
the rotamers predominates strongly. Similar results have been
observed in previous studies related to other N-(1-phenylethyl)-
1,3-thiazoline-2-thiones, substituted in the 4 and 5 positions,
E1
E2
Epa
3
4
ꢀ0.33
ꢀ0.29
ꢀ1.20
ꢀ0.175
+0.25
0.86a
[Ni(Me-thiazdt)2]9b
+0.20/0.01b
ꢀ0.43
where it was demonstrated that these compounds exist pre- [Ni(DL-bordt)2]c,d
+1.00a
[Ni(dmit)2]17
+0.34/0.228b
dominantly in the anti form.13
a
b
Single crystals of good quality for X-ray diffraction studies
were obtained by slow diffusion of diethyl ether into a concen-
trated solution of (S)-3 in dichloromethane. Fig. 2 shows the
two crystallographically independent molecules, for the struc-
ture solved in the orthorhombic system, space group P212121.
Both crystallographically independent molecules (S)-3 exhibit a
planar thiazole skeleton with the C*–H of the chiral substituent
oriented towards the CQS thione, that is the anti rotamer
(Chart 2). The C–H bonds lie in the plane of the thiazole ring
with short C–Hꢁ ꢁ ꢁS distances (2.5662(1) and 2.577(1) Å). Within
this anti conformer, as observed in the NMR 1H study, the
phenyl group exerts a strong shielding effect on the closest
cyanoethyl group.
Not fully reversible process. Epa/Epc: anodic and cathodic peak
c
d
potentials. E values have been determined in CH2Cl2. DL-bordt
stands for bornylenedithiolate.
Fig. 3 Cyclic voltammogram of (R,R)-4 in CH3CN with 0.1 M Bu4NPF6 as
Deprotection of the dithiolate precursor 3 was performed in
basic medium using NaOMe,16 followed by addition of NiCl2
and Et4NBr, to afford the dianionic dithiolene complexes 4 as a
dark red crystalline material (Scheme 1). The reaction was
conducted on the enantiopure (R)-3 and (S)-3 affording respec-
tively the dianionic complexes (R,R)-4 and (S,S)-4. Attempts to
analyze the dianionic complexes using H1 NMR spectroscopy
were unsuccessful due to the fact that these complexes, as their
methyl analogues [NEt4][Ni(Me-thiazdt)2],9b are easily oxidized
in solution upon exposure to traces of air to the paramagnetic
radical anion species. This was confirmed by the investigation
of their redox properties by cyclic voltammetry (CV). These
studies were carried out in CH3CN using [Bu4N][PF6] as the
supporting electrolyte and the redox potentials of (R,R)-4 and
(S,S)-4 are collected in Table 1 together with those of [NEt4]-
[Ni(Me-thiazdt)2] and [NBu4]2[Ni(dmit)2]17 for comparison.
The Ni complexes 4 exhibit two reversible oxidation waves at
E1 = ꢀ0.33 V and E2 = +0.25 V vs. SCE, corresponding to the
oxidation of the dianionic species into the radical anion and
supporting electrolyte at a scan rate of 100 mV sꢀ1. Pt working electrode.
then to the neutral species (Fig. 3). A third irreversible redox
3
process is also observed at Epa = +0.86 V vs. SCE (Epa = anodic
peak potential) associated with the oxidation of the neutral
complex into the radical cation. Comparison with the Ni
dithiolene complexes belonging to the same family, [NEt4]-
[Ni(Me-thiazdt)2], and investigated under the same conditions,
shows no difference in the redox potentials, indicating that the
presence of the –C*HMePh substituent on the thiazole ring has
no significant effect. In contrast, comparison with the well-
known Ni(dmit)2 derivative shows a cathodic shift of about
150 mV for the potential of the ꢀ2/ꢀ1 redox process for 4,
confirming the electron rich character of the thiazole dithiolene
ligands.
In order to generate the radical anion species, (R,R)-4 and
(S,S)-4 were reacted with one equivalent of [Cp2Fe][PF6]. The
resulting anionic complexes (R,R)-5 and (S,S)-5, [NEt4][Ni((R)-
CHMePh-thiazdt)2] were then crystallized in an acetonitrile–
toluene solution, and crystals of the enantiopure (R,R)-5 suitable
for an X-ray diffraction study were obtained.
Structural properties
Complex (R,R)-5 crystallizes in the monoclinic system, space
group C2ꢂ with both Et4N+ cation and [Ni((R)-CHMePh-
thiazdt)2]ꢀ radical anion located in the general position in the
unit cell. The molecular structure represented in Fig. 4 shows a
slightly distorted square planar geometry around the Ni atom
and the formation of the trans-isomer. Concerning the thiazole
skeleton, the C–H groups of the chiral substituents are oriented
towards the thione bonds leading to the anti/anti rotamer
(Chart 3) as observed for the organic precursor 3 (Chart 2).
In the solid state, the enantiopure complexes are isolated
from each other by the Et4N+ counterion in the ac plane while
Fig. 2 Molecular structures of the two crystallographically independent
molecules (S)-3.
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ꢀ
Fig. 4 Molecular structure of the radical anion [Ni((R)-CHMePh-thiazdt)2]ꢂ
in [NEt4][Ni((R)-1-PhEt-thiazdt)2] 5 showing the atom labelling.
Chart 3
Fig. 5 Top: projection view along the ac plane of the unit cell of the
monoanionic radical (R,R)-5 the NEt4 groups have been omitted for clarity.
Bottom: view of the shortest Sꢁ ꢁ ꢁS contacts in the chains of radical anions
running along b.
several short lateral Sꢁ ꢁ ꢁS intermolecular contacts can be
observed along the b axis (Fig. 5). Actually, steric hindrance
due to the presence of the bulky N-1-phenylethyl substituent
on the nitrogen impedes shorter lateral contacts in the bc plane.
The temperature dependence of the magnetic susceptibility for
the enantiopure monoanionic radical (R,R)-5 shows a weak the near-IR region with a strong absorption band at 1013 nm
Curie-type behavior with a magnetic susceptibility accounting (e = 28 454 Mꢀ1 cmꢀ1). The gradual reduction of this neutral Ni
for only 3.8% S = 1/2 species, demonstrating that the radical complex to the monoanionic species induces the growth of a
anions in (R,R)-5 are interacting antiferromagnetically within the lower energy band in the near-IR region, at 1260 nm, concomi-
chains running along b, to such an extent that the remaining tantly with the disappearance of the band at 1013 nm, as shown
susceptibility in the investigated temperature range (5–300 K) is in Fig. 6. These values are in accordance with those obtained on
negligible.
the Ni(Et-thiazdt)2 analogue, where the neutral and monoanionic
Oxidation of the radical anion species, (R,R)-5 and (S,S)-5, species exhibit indeed absorption bands at comparable wave-
with one more equivalent of [Cp2Fe][PF6] leads to the neutral lengths, i.e. 1030 nm (in toluene) and 1219 nm (in CH2Cl2),
species [Ni(CHMePh-thiazdt)2] (R,R)-6 and (S,S)-6. These neutral respectively.18 These low-energy absorption bands are character-
diamagnetic species have been investigated by 1H NMR at room istic of square-planar nickel dithiolene complexes and are attri-
temperature where the signals associated with the benzylic buted to a p–p* transition of the HOMO–LUMO character within
protons are well resolved, compared to those observed for the these neutral species.19
protected ligands (R)-3 and (S)-3. This indicates the presence of
As mentioned in the Introduction, the chiral character of
only one rotamer at room temperature, most probably because these complexes opens perspectives toward the elaboration of
of the steric hindrance generated by the metallacycles.
electrochemically driven chiroptical switches.20,21 Accordingly,
the optical activity and circular dichroism of the dithiolene
complexes, as well as some organic chiral precursors were
UV-vis-NIR spectroelectrochemical investigations
UV-vis-NIR absorption spectra of freshly prepared solutions of the investigated, in the UV-vis range as well as in the NIR range
neutral dithiolene species in dichloromethane exhibit absorption when possible. The optical activity of two organic precursors, the
bands in the UV-vis region between 250 and 450 nm and also in non-substituted thiazole 1 and the organic protected dithiolate
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Fig. 6 UV-vis-NIR monitoring of the electrochemical reduction of
[Ni(CHMePh-thiazdt)2] (R,R)-6 from 0.25 V to ꢀ0.2 V in CH2Cl2 with
0.1 M Bu4NPF6 as the supporting electrolyte.
Table 2 Specific and molar optical rotations of compounds 1, 3 and 5 in
CH2Cl2, 0.5 ꢃ 10ꢀ3 g mLꢀ1, 23 1C
(R)-1a
(S)-1
(R)-3
(S)-3
(R,R)-5
(S,S)-5
[a]578
[a]546
[a]436
[F]578
[F]546
[F]436
+325
+391
ꢀ345
ꢀ407
+258
+312
ꢀ253
—
—
+1500
—
—
ꢀ1677
ꢀ305
+719
+865
ꢀ764
ꢀ901
1010
1221
ꢀ990
ꢀ1194
+11 300
ꢀ12 400
Previously reported value [a]D = +377 (c = 0.93, EtOH).10
a
Fig. 7 CD spectra in CH2Cl2 (inserts: UV-vis absorption spectra) of thiazo-
line 1 (top) and of neutral complexes 6 (bottom).
form 3, as well as the radical anion complex 5 are reported
in Table 2, as specific and molar optical rotations at three
different wavelengths, (436, 546 and 578 nm), in the visible
range. Note that both enantiomers of 5, (R,R)-5 and (S,S)-5,
exhibit practically no optical rotation (|a| o 0.002) at 365 nm
and between 546 nm and 589 nm but show a weak optical
activity at 436 nm (|a| o 0.048).
negative band ranging from 300 nm to 455 nm band with two
maxima at 320 nm and 430 nm and a broad positive band from
455 nm to 660 nm. Most of these CD-active bands undergo
changes in their intensities upon reduction accompanied by
slight bathochromic shifts.
The CD spectra of the neutral and the radical anion species
have been also investigated in the NIR region (insert Fig. 8),
where both compounds are known to absorb (see Fig. 6).
Remarkably, the neutral species exhibits a negative CD band
centered around 1000 nm, related to its 1013 nm absorption.
Circular dichroism (CD) spectra in the UV-visible range (Fig. 7)
were recorded in CH2Cl2 at room temperature for the neutral
complexes (R,R)- and (S,S)-6, together with those of starting
thiazoline (R)- and (S)-1 for comparison. These CD spectra of both
enantiomers, for 1 and for 6, exhibit mirror-image relationships.
The spectrum for the (R)-1 enantiomer exhibits a weak negative
band around 340 nm, a positive band at 320 nm and at shorter
wavelengths a positive band at 270 nm. This spectrum is similar
to the one reported for this compound by Sandstrom et al.13 The
¨
CD spectrum of the (S)-1 enantiomer is the mirror-image of the
(R)-1 spectrum. Besides some similarities in the short wavelengths
such as a positive band at around 270 nm for (R,R)-6, the CD
spectra of the neutral complexes (R,R)- and (S,S)-6 exhibit two
weak CD-active bands above 400 nm ((R,R)-6: De = ꢀ7.22 Mꢀ1 cmꢀ1
at 403 nm and De = ꢀ1.9 Mꢀ1 cmꢀ1 at 564 nm).
In order to investigate the CD spectra of the other redox
species such as the dianion in 4 and the radical anion in 5, we
set up a thin-layer spectro-electrochemical experiment on the
CD spectrometer, starting with a solution of the neutral (R,R)-6
enantiomer (Fig. 8). In the UV-vis region, the CD spectra of the
electrogenerated radical anion (R,R)-5 and the dianion (R,R)-4
show some similarities, a positive band at 280 nm, a broad
Fig. 8 CD spectra monitored electrochemically in CH2Cl2 at 293 K of the
neutral (R,R)-6, radical anion (R,R)-5 and dianion (R,R)-4 complexes (insert:
CD spectra from 900 to 1030 nm).
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This CD active band in the NIR disappears upon reduction to 0.1 mol) in 200 mL of diethyl ether at 0 1C under nitrogen was
the radical anion, while no clear CD signal can be observed for slowly dropped triethylamine (14.6 mL, 0.105 mol) and carbon
the radical anion species at lower energies, due to spectro- disulfide (6.34 mL, 0.105 mol). The mixture was stirred for
photometer limitations in the wavelength range. Note also that 3 hours at 0 1C and the precipitate was filtered off and washed
the UV-vis-NIR CD spectra monitored electrochemically exhibit with diethyl ether to afford 29.8 g of dithiocarbamate salt which
a very good reversibility, as the CD spectrum of the neutral was used without further purification. Yield 100%. 1H NMR
complex (R,R)-6 could be recovered from the dianionic and (300 MHz, D2O) d 1.25 (t, 9H, N(CH2CH3)3, J = 7.2 Hz), 1.50
monoanionic complexes, upon oxidation.
(d, 3H, CH3, J = 7.0 Hz), 3.18 (q, 6H, N(CH2CH3)3, J = 7.2 Hz),
5.43 (q, 1H, CH, J = 7.0 Hz), 7.38 (m, 5H, Ar); 13C NMR (75 MHz,
D2O) d 8.6, 21.1, 45.9, 54.3, 126.2, 126.4, 127.4, 128.2, 128.5,
142.2. To a suspension of the dithiocarbamate salt (29.8 g,
0.1 mol) in acetonitrile (300 mL) was added chloroacetaldehyde
(50% solution in water, 25.4 mL, 0.2 mol). The mixture was
stirred for 24 hours at room temperature under nitrogen. The
volume was reduced to approximately 1/5 in vacuo and the
solution was slowly added to a flask containing 20 mL of H2SO4
at 0 1C. The mixture was stirred 15 min at 0 1C, hydrolyzed with
120 mL of water, extracted with CH2Cl2 (3 ꢃ 80 mL), washed
with water (3 ꢃ 50 mL) and dried over MgSO4. The concentrated
solution was purified by chromatography on silica gel using
CH2Cl2 as the eluent to afford 1 as a thick, brown oil.
Conclusions
In conclusion, we have described here the synthesis of a novel chiral
Ni dithiolene complex where the chirality was provided by the
dithiolene ligand, in the close proximity of the complex metallacycles.
Electrochemical and spectro-electrochemical experiments showed
that these Ni complexes exhibit four redox states from the dianion,
radical anion, neutral to the radical cation with different UV-visible-
near infrared (UV-vis-NIR) spectra. The spectro-electrochemical
circular dichroism (CD) spectroscopy studies revealed changes in
several CD active bands when reducing the neutral enantiopure
complex (R,R)-6 to the radical anion (R,R)-5 and dianion (R,R)-4.
Interestingly, the appearance of a CD-active band in the NIR region
is observed in the neutral Ni–dithiolene complex upon oxidation of
the radical anion. These results suggest that chiral Ni–dithiolene
complexes may be potentially used as redox chiroptical switches both
in the UV-vis and NIR regions.21
(R)-1: yield 54%. 1H NMR (300 MHz, CDCl3) d 3.35 (t, 3H,
CH3, J = 6.9 Hz), 6.53 (m, 2H, QCH,*CH), 6.88 (d, 1H, CH,
J = 4.8 Hz), 7.33 (m, 5H, Ar). 13C NMR (75 MHz, CDCl3) d 18.4,
56.2, 111.2, 126.8, 128.2, 128.4, 128.8, 138.9, 186.0; HRMS (ESI)
calcd for C11H11NNaS2+: 244.02306. Found: 244.0230.
(S)-1: yield 55%. 1H NMR (300 MHz, CDCl3) d 3.35 (t, 3H,
CH3, J = 6.9 Hz), 6.53 (d, 1H, CH, J = 4.8 Hz), 6.59 (q, 1H, CH,
J = 6.9 Hz), 6.88 (d, 1H, CH, J = 4.8 Hz), 7.33 (m, 5H, Ar). 13C NMR
(75 MHz, CDCl3) d 18.4, 56.2, 111.7, 126.9, 128.2, 128.4, 128.8,
138.9, 186.9; Anal. calcd for C11H11NS2: C, 59.68; H 5.01; N, 6.33;
S, 28.97. Found: C, 59.81; H, 5.01; N, 6.35; S, 28.80; HRMS (ESI)
Experimental section
General
All air-sensitive reactions were carried out under an argon atmo-
sphere. Melting points were measured on a Kofler hot-stage appa-
ratus and are uncorrected. 1H NMR and 13C NMR spectra were
recorded on a Bruker AV300III spectrometer and chemical shifts are
quoted in parts per million (ppm) referenced to tetramethylsilane.
Optical rotation of the enantiopure compounds was determined
using a Perkin-Elmer 341 polarimeter. The circular dichroism (CD)
spectra were recorded on a Jasco spectropolarimeter J-815. Mass
spectra were recorded using a Thermo-fisher Q-Exactive instrument
+
calcd for C11H11NNaS2 : 244.02306. Found: 244.0229.
1
(R/S)-1: yield 55%. H NMR (300 MHz, CDCl3) d 3.35 (t, 3H,
CH3, J = 6.9 Hz), 6.53 (m, 2H, QCH,*CH), 6.88 (d, 1H, CH,
J = 4.8 Hz), 7.33 (m, 5H, Ar). 13C NMR (75 MHz, CDCl3) d 18.42,
56.2, 111.2, 126.8, 128.2, 128.4, 128.8, 138.9, 186.0; Anal calcd
for C11H11NS2: C, 59.68; H, 5.01; N, 6.33; S, 28.97. Found: C,
59.41; H, 5.03; N, 6.11; S, 28.86; HRMS (ESI) calcd for
C
11H11NNaS2+: 244.02306. Found: 244.0231.
(R)-, (S)- and (R,S)-3,30-[3-(1-phenylethyl)-2-thioxo-2,3-dihydro-
´
by the Centre Regional de Mesures Physiques de l’Ouest, Rennes.
´
Elemental analyses were performed at the Centre Regional de
1,3-(thiazole-4,5-diyl)bis(thio)]dipropanenitrile 3. To a cooled
solution at ꢀ10 1C of thiazoline 1 (2 g, 9 mmol) in 90 mL of
dry THF under nitrogen was added a solution of LDA prepared
from diisopropylamine (1.96 mL, 13.5 mmol) and n-BuLi 1.6 M
in hexane (8.5 mL, 13.5 mmol) in 20 mL of dry THF. After stirring
for 30 min at ꢀ10 1C, sulphur S8 (434 mg, 13.5 mmol) was added
and the solution was stirred for an additional 30 min. A solution
of LDA (diisopropylamine 2.56 mL, 18.0 mmol and n-BuLi 1.6 M
in hexane 11.3 mL, 18.0 mmol) in 40 mL of dry THF was added.
The mixture was stirred for 3 hours and S8 (578 mg, 18.0 mmol)
was added. After 30 min ZnCl2 (616 mg, 4.5 mmol) and NEt4Br
(1.9 g, 9.0 mmol) were added. The reaction mixture was stirred
overnight and the precipitate was filtered off and washed with
Mesures Physiques de l’Ouest, Rennes. Tetrahydrofuran was
distilled from sodium–benzophenone. Column chromatography
was performed using silica gel Merck 60 (70-260 mesh). The spectro-
electrochemical setup was performed in 0.2 M CH2Cl2-[NBu4][PF6].
A Cary 5000 spectrophotometer was employed to record the
UV-vis-NIR spectra. Cyclic voltammetry were carried out on a 10ꢀ3 M
solution of the complex in CH2Cl2, containing 0.1 M nBu4NPF6
as the supporting electrolyte. Voltammograms were recorded at
0.1 V sꢀ1 on a platinum disk electrode (A = 1 mm2). The potentials
were measured versus the saturated calomel electrode.
Syntheses
(R)-, (S)- and (R,S)-3-(1-phenylethyl)-1,3-thiazoline-2-thione diethyl ether to afford [NEt4]2[Zn(1-phenylethyl-thiazdt)2] 2 as a
1. To a suspension of 1-phenylethylamine (R/S, R or S) (12.8 mL, yellow powder. The Zn salt 2 was used in the next step without
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further purification. (R)-2 62% yield. Mp 222 1C. 1H NMR room temperature. The solution was stirred for 1 hour and a
(300 MHz, CD3CN) d 1.16 (t, 24H, CH3, J = 7.2 Hz), 1.93 (broad solution of NiCl2 (45 mg, 0.35 mmol) in 10 mL of dry EtOH was
signal, 6H, CH3), 3.12 (t, 16H, N(CH2CH3)3, J = 7.2 Hz), 6.42 added. The reaction mixture was stirred for 5 hours and a
(broad signal, 2H, CH), 7.27 (m, 10H, Ar). 13C NMR (75 MHz, solution of NEt4Br (72 mg, 0.35 mmol) in 5 mL of dry EtOH was
CD3CN) d 7.6, 19.0, 48.1, 52.9, 127.6, 128.5, 129.4, 129.6, 129.7, added. The mixture was stirred overnight and the precipitate
141.3, 184.1. (S)-2 67% yield. Mp 239 1C. 1H NMR (300 MHz, was filtered off, washed with EtOH to afford a red-brown
(CD3)2SO) d 1.15 (t, 24H, CH3, J = 7.2 Hz), 1.94 (broad signal, 6H, powder (150 mg), and (R,R)-4 and (S,S)-4 in 65–69% yield.
CH3), 3.20 (t, 16H, N(CH2CH3)3, J = 7.2 Hz), 6.35 (broad signal, Analysis of these dianions by 1H NMR was not possible due
2H, CH), 7.24 (m, 10H, Ar). 13C NMR (75 MHz, (CD3)2SO) d 7.1, to the presence of anion radical species in the medium.
15.4, 51.4, 55.8, 126.2, 126.5, 126.6, 126.8, 127.7, 139.8, 180.8.
[NEt4][Ni(1-phenylethyl-thiazdt)2] (S,S)-5 and (R,R)-5. To a
(R/S)-2: 73% yield. Mp 235 1C. 1H NMR (300 MHz, (CD3)2SO) solution of ferricinium hexafluorophosphate (53 mg, 0.16 mmol)
d 1.15 (t, 24H, CH3, J = 7.2 Hz), 1.94 (broad signal, 6H, CH3), 3.20 in 10 mL of CH2Cl2 under an inert atmosphere, the dianionic
(t, 16H, N(CH2CH3)3, J = 7.2 Hz), 6.37 (broad signal, 2H, CH), 7.22 species 4 (140 mg, 0.16 mmol) was added. After stirring for 1 h, the
(m, 10H, Ar). 13C NMR (75 MHz, (CD3)2SO) d 7.0, 15.4, 51.3, 55.6, addition of pentane (50 mL) afforded a precipitate, which was
126.1, 126.5, 126.6, 126.8, 127.5, 139.8, 179.12. To a solution of filtered out. Recrystallization of the precipitate in acetonitrile gave
the zinc complex 2 (1 g, 1.12 mmol) in 40 mL of degassed MeCN crystals of the monoanionic species in 57% yield for (S,S)-5 and in
under nitrogen was added bromopropionitrile (3.65 mL, 77% yield for (R,R)-5.
11.20 mmol). The mixture was refluxed for 24 hours and solvent
(S,S)-5. Mp 4 250 1C; Anal. calcd for C30H38N3S8Ni: C, 47.67; H,
was removed in vacuo and 150 mL of CH2Cl2 was added. The 5.07; N, 5.56. Found: C, 47.63; H, 5.07; N, 5.56. HRMS (ESI) calcd for
solution was washed with water (2 ꢃ 50 mL) and dried over Aꢀ(C22H18N2S8Ni): 623.85947. Found: 623.8596; calcd for the ioni-
MgSO4. The concentrated solution was purified by chromato- zation cluster [2Aꢀ,Et4N+]ꢀ: 1377.87797. Found: 1377.8788. UV-vis
graphy on silica gel using CH2Cl2 as the eluent to afford 3. (CH2Cl2) l (nm) (e [L molꢀ1 cmꢀ1]) 324 (16 442), 366 (18 846), 432
25
Recrystallisation in EtOH gave a white powder.
(6256), 1252 (13 558). [a]24356 = ꢀ1677, [F] = ꢀ12 400.
436
1
(R)-3: yield 41%, Mp = 108 1C. H NMR (300 MHz, (CDCl3)2
(R,R)-5. Mp 4 250 1C; Anal. calcd for C30H38N3S8Ni: C, 47.67;
1.97 (d, 3H, CH3, J = 7.2 Hz), 2.19 (broad s, 4H, CH2CN), 2.70 H, 5.07; N, 5.56; S, 33.94. Found: C, 47.50; H, 5.02; N, 5.34; S,
(t, 2H, SCH2, J = 6.9 Hz), 3.09 (t, 2H, SCH2, J = 6.9 Hz), 7.05 34.36. HRMS (ESI) calcd for Aꢀ(C22H18N2S8Ni): 623.85947.
(broad signal, 1H, CH), 7.36 (m, 5H, Ar)). 13C NMR (75 MHz, Found: 623.8601; calcd for the ionization cluster [2Aꢀ,Et4N+]ꢀ:
(CDCl3) d 16.4, 17.4, 18.6, 31.3, 31.4, 57.1, 117.0, 117.2, 126.5, 1377.87797. Found: 1377.8798. UV-vis (CH2Cl2)
l (nm)
127.7, 127.8, 128.6, 135.7, 138.7, 188.6). UV-vis (CH2Cl2) l (nm) (e [L molꢀ1 cmꢀ1]) 323 (15 220), 366 (18 693), 432 (5720), 1250
25
25
436
(e [L molꢀ1 cmꢀ1]) 318 (15 586); Anal. calcd for C17H17N3S4: (12 870). [a] = +1500, [F] = +11 300.
436
C, 52.14; H, 4.38; N, 10.73; S, 32.75. Found: C, 52.00; H, 4.42;
[Ni(1-phenylethyl-thiazdt)2] (S,S)-6 and (R,R)-6. To a solution
N, 10.70; S, 32.55. HRMS (ESI) calcd for C17H17N3NaS4 : of ferricinium hexafluorophosphate (33 mg, 0.1 mmol) in 7 mL
414.0203. Found: 414.0201. of CH2Cl2 under an inert atmosphere, the monoanionic species
+
1
(S)-3: yield 40%, Mp = 109 1C. H NMR (300 MHz, (CDCl3)2 5 (75 mg, 0.1 mmol) was added. After stirring for 1 h, the
1.99 (d, 3H, CH3, J = 7.2 Hz), 2.20 (broad s, 4H, CH2CN), 2.72 addition of pentane afforded a precipitate, which was filtered
(t, 2H, SCH2, J = 6.9 Hz), 3.11 (t, 2H, SCH2, J = 6.9 Hz), 7.12
(broad signal, 1H, CH), 7.38 (m, 5H, Ar)). 13C NMR (75 MHz,
(CDCl3) d 16.3, 17.3, 18.5, 31.2, 31.3, 57.0, 117.0, 117.2, 126.5,
Table 3 Crystallographic data for (S)-3 and (R,R)-5
126.9, 127.6, 128.5, 135.6, 138.5, 188.4); UV-vis (CH2Cl2) l (nm)
(e [L molꢀ1 cmꢀ1]) 318 (14 918); Anal. calcd for C17H17N3S4:
Compound
(S)-3
(R,R)-5
C, 52.14; H, 4.38; N, 10.73; S, 32.75. Found: C, 51.54; H, 4.46; Formula
2(C17H17N3S4)
783.15
C30H38N3NiS8
755.88
Monoclinic
C2
16.624(4)
7.8685(14)
28.101(5)
90
102.325(7)
90
3591.2(12)
293(2)
4
1.398
1.031
15 925
7860 (0.0828)
4396
0.0635, 0.1283
0.1250, 0.1560
0.996
FW (g molꢀ1
)
Crystal system
Space group
N, 10.64; S, 32.59. HRMS (ESI) calcd for C17H17N3NaS4 [M+Na]+:
414.0203. Found: 414.0203.
Orthorhombic
P212121
8.5565(3)
11.6085(3)
37.5518(10)
90
(R,S)-3: yield 38%, Mp = 108 1C. 1H NMR (300 MHz, (CDCl3)2 a (Å)
b (Å)
c (Å)
1.97 (d, 3H, CH3, J = 7.2 Hz), 2.19 (broad s, 4H, CH2CN), 2.71
(t, 2H, SCH2, J = 6.9 Hz), 3.08 (t, 2H, SCH2, J = 6.9 Hz), 7.09
a (1)
(broad signal, 1H, CH), 7.37 (m, 5H, Ar)). 13C NMR (75 MHz, b (1)
90
90
g (1)
(CDCl3) d 16.5, 17.5, 18.6, 31.4, 31.6, 57.2, 117.0, 117.1, 126.5,
V (Å3)
3729.95(19)
150(2)
4
1.395
0.513
33 125
8535 (0.0551)
7759
0.0365, 0.0756
0.042, 0.078
1.026
127.1, 127.8, 128.8, 135.9, 138.8, 188.8). UV-vis (CH2Cl2) l (nm)
T (K)
(e [L molꢀ1 cmꢀ1]) 318 (15 227); Anal. calcd for C17H17N3S4:
Z
Dcalc (g cmꢀ3
)
C, 52.14; H, 4.38; N, 10.73; S, 32.75. Found: C, 52.03; H, 4.38;
m (mmꢀ1
)
+
N, 10.73; S, 32.81; HRMS (ESI) calcd for C17H17N3NaS4 :
Total refls
Uniq. refls (Rint
Unique refls (I 4 2s(I))
R1, wR2
R1, wR2 (all data)
414.0203. Found: 414.0201.
[NEt4]2[Ni(1-phenylethyl-thiazdt)2] (S,S)-4 and (R,R)-4. To a
dry two necked flask containing thiazoline-2-thione 3 (225 mg,
)
0.58 mmol) 10 mL of 2 M NaOMe was added under nitrogen at GoF
128 | New J. Chem., 2015, 39, 122--129
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Paper
NJC
1
I. Olejniczak, J. D. Wallis, E. Canadell and N. Avarvari,
J. Am. Chem. Soc., 2013, 135, 17176–17186.
8 Q. Ye, T. Akutagawa, T. Endo, S. I. Noro, T. Nakamura and
R. G. Xiong, Inorg. Chem., 2010, 49, 8591–8600.
out in a quantitative yield. H NMR (300 MHz, CDCl3) d 2.14
(d, 3H, CH3, J = 7.2 Hz), 1.50 (q, 1H, CH, J = 6.9 Hz), 7.37 (m, 5H, Ar).
UV-vis (CH2Cl2) l (nm) (e [L molꢀ1 cmꢀ1]) 316 (23 875), 390 (14 462),
432 (5720), 1013 (28 454).
9 (a) S. Eid, M. Guerro and D. Lorcy, Tetrahedron Lett., 2006, 47,
Crystallography. Data were collected on an APEX II Bruker
AXS diffractometer using graphite-monochromated Mo-Ka
radiation (l = 0.71073 Å). The structures were solved using direct
methods and the SIR97 program,22 and then refined using full-
matrix least-square methods based on F2 (SHELXL-97)23 with the
´
8333–8336; (b) S. Eid, M. Fourmigue, T. Roisnel and D. Lorcy,
Inorg. Chem., 2007, 46, 10647–10654; (c) A. Filatre-Furcate,
´
N. Bellec, O. Jeannin, P. Auban-Senzier, M. Fourmigue,
A. Vacher and D. Lorcy, Inorg. Chem., 2014, 53, 8681–8690.
aid of the WINGX program.24 All non-hydrogen atoms were 10 (a) N. Tenn, N. Bellec, O. Jeannin, L. Piekara-Sady, P. Auban-
´
˜
refined with anisotropic atomic displacement parameters.
H atoms were finally included in their calculated positions. Details
of the final refinements are given in Table 3 for compounds (S)-3
and (R,R)-5 (CCDC 1015857 and 1015858).
Senzier, J. Iniguez, E. Canadell and D. Lorcy, J. Am. Chem.
Soc., 2009, 131, 16961–16967; (b) G. Yzambart, N. Bellec,
´
N. Ghassan, O. Jeannin, T. Roisnel, M. Fourmigue,
´
˜
P. Auban-Senzier, J. Iniguez, E. Canadell and D. Lorcy,
J. Am. Chem. Soc., 2012, 134, 17138–17148; (c) Y. Le Gal,
T. Roisnel, P. Auban-Senzier, T. Guizouarn and D. Lorcy,
Inorg. Chem., 2014, 53, 8755–8761.
Acknowledgements
11 S. Eid, T. Roisnel and D. Lorcy, J. Organomet. Chem., 2008,
693, 2755–2760.
Financial support was obtained from ANR (France) under contract
no. 12-BS07-0032-01. CD spectra were acquired on the spectroscopy
12 T. Bsaibess, M. Guerro, Y. Le Gal, D. Sarraf, N. Bellec,
´
facility from Biosit (Universite de Rennes 1) and X-ray data from the
´
`
M. Fourmigue, F. Barriere, V. Dorcet, T. Guizouarn,
´
CDIFX facility (ISCR, Universite of Rennes1).
T. Roisnel and D. Lorcy, Inorg. Chem., 2013, 52, 2162–2173.
¨
13 J. Roschester, U. Berg, M. Pierrot and J. Sandstrom, J. Am.
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This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem., 2015, 39, 122--129 | 129