Synthesis, Structure, and Physical Properties of Nickel Bis(dithiolene) Metal Complexes, [Ni(dmit)2], with Highly Polar Cyanine Dyes

Article abstract of DOI:10.1021/ic971550+

Three new compounds were obtained by slow diffusion of [Ni(dmit)₂]^- (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) into 4-(dimethylamino)-1-methylpyridinium [C₁]⁺, 4-[2-(4-(dimethylamino)phenyl)ethenyl]-1-methylpyridinium [C₂]⁺, and 4-[4-(4-(dimethylamino)phenyl)-1,3-butadienyl]-1-methylpyridinium [C₃]⁺. [C₃]⁺[Ni(dmit)₂]^- exhibits two crystallographic phases (1, 2) as does [C₂]⁺[Ni(dmit)₂]^- (3, 4). The structures have been determined: 1, monoclinic, P2₁/c, a = 17.450(2) ?, b = 10.646(1) ?, c = 23.891(2) ?, β= 97.42(1)°, Z = 4; 2, triclinic P1?, a = 9.776(1) ?, b = 15.195(2) ?, c = 16.999(2) ?, α = 114.14(1)°, β= 101.84(1)°, γ = 93.40(1)°, Z = 2; 3, monoclinic, P2₁/2, a = 9.813(1) ?, b = 11.589(1) ?, c = 24.345(3) ?, β= 93.12(1)°, Z = 4; 4, triclinic, P1?, a = 13.432(2) ?, b = 16.101(2) ?, c = 6.553(1) ?, α = 99.69(1)°, β= 94.34(1)°, γ = 102.88(2)°, Z = 2; [C₂]^-[Ni(dmit)₂]^- (1) exhibits a conductivity of 1.3 × 10^-2 S cm^-1. Due to centrosymmetry, none of the materials exhibits second-order nonlinear optical properties, but the structure of 1 demonstrates that layers of highly polarizable cations can be stabilized in a noncentrosymmetric environment between two-dimensional networks of [Ni(dmit)₂]^- species.

Full text of DOI:10.1021/ic971550+

Inorg. Chem. 1998, 37, 3361-3370
3361
Synthesis, Structure, and Physical Properties of Nickel Bis(dithiolene) Metal Complexes,
[Ni(dmit)2], with Highly Polar Cyanine Dyes
Isabelle Malfant, Raquel Andreu, Pascal G. Lacroix,* Christophe Faulmann, and
Patrick Cassoux
Equipe Pre´curseurs Mole´culaires et Mate´riaux, LCC/CNRS, 205 Route de Narbonne,
31077 Toulouse Cedex, France
ReceiVed December 10, 1997
Three new compounds were obtained by slow diffusion of [Ni(dmit)2]- (dmit ) 2-thioxo-1,3-dithiole-4,5-dithiolato)
into 4-(dimethylamino)-1-methylpyridinium [C1]+, 4-[2-(4-(dimethylamino)phenyl)ethenyl]-1-methylpyridinium
[C2]+, and 4-[4-(4-(dimethylamino)phenyl)-1,3-butadienyl]-1-methylpyridinium [C3]+. [C1]+[Ni(dmit)2]- exhibits
two crystallographic phases (1, 2) as does [C2]+[Ni(dmit)2]- (3, 4). The structures have been determined: 1,
monoclinic, P21/c, a ) 17.450(2) Å, b ) 10.646(1) Å, c ) 23.891(2) Å, â ) 97.42(1)°, Z ) 4; 2, triclinic P1h,
a ) 9.776(1) Å, b ) 15.195(2) Å, c ) 16.999(2) Å, R ) 114.14(1)°, â ) 101.84(1)°, γ ) 93.40(1)°, Z ) 2; 3,
monoclinic, P21/c, a ) 9.813(1) Å, b ) 11.589(1) Å, c ) 24.345(3) Å, â ) 93.12(1)°, Z ) 4; 4, triclinic, P1h, a
) 13.432(2) Å, b ) 16.101(2) Å, c ) 6.553(1) Å, R ) 99.69(1)°, â ) 94.34(1)°, γ ) 102.88(2)°, Z ) 2;
[C1]+[Ni(dmit)2]- (1) exhibits a conductivity of 1.3 × 10-2 S cm-1. Due to centrosymmetry, none of the materials
exhibits second-order nonlinear optical properties, but the structure of 1 demonstrates that layers of highly polarizable
cations can be stabilized in a noncentrosymmetric environment between two-dimensional networks of [Ni(dmit)2]-
species.
Introduction
very little has been published on molecular materials.7-9 We
have recently reported on a family of derivatives combining
The rapid developments in the field of telecommunications
and computing devices are pressing the need for improved
electronic components. The emerging technology of photonics,
which uses nonlinear optical (NLO) materials for high-speed
digital switching and frequency conversion, has been labeled
the technology of the twentyfirst century.1,2 In any case, the
possible shift from electronics to photonics will probably be
gradual, and during the transition period, the hybrid technology
of optoelectronics, in which electrons interface with photons,
will become increasingly important. Molecular chemistry offers
a unique opportunity to design materials combining several
properties (e.g. magnetism and conductivity,3,4 or magnetism
and nonlinear optics5) that could hopefully be coupled in an
actual interplay. Following this idea, linking conductivity and
NLO properties would also provide the interest to associate
semiconductor-based electronics and NLO-based photonics
within a research effort aiming at connecting these technologies.
The past few years have seen the emergence of a new class
of polymeric materials exhibiting photorefractivity, a property
that combines photoconductivity and electrooptic response,6 but
efficient second-order NLO chromophores and 7,7′,8,8′-tetra-
cyanoquinodimethane [tcnq] acceptors, a counterion that could
bring about NLO materials with conducting properties.9 The
absence of crystal structures did not allow the full understanding
of the origin and extent of the possibly coupled properties.
Following a similar strategy, [Ni(dmit)2]-based systems (dmit2-
) 2-thioxo-1,3-dithiole-4,5-dithiolato; Chart 1), instead of [tcnq],
could be used as a component awarding conducting properties
to the desired hybrid compound. Nickel bis(dithiolene) deriva-
tives such as [Ni(dmit)2] have received considerable attention
since the discovery of superconductivity in [ttf][Ni(dmit)2]2,10
a property that has never been observed in any [tcnq]-based
materials. Combining [Ni(dmit)2]-based anions with cationic
chromophores may lead to the preparation of molecular systems
exhibiting both NLO and conducting properties. Among
possible candidate cations, we have selected the highly polariz-
able “push-pull” cyanines, 4-(dimethylamino)-1-methylpyri-
dinium [C1]+, 4-[2-(4-(dimethylamino)phenyl)ethenyl]-1-methyl-
pyridinium [C2]+, and 4-[4-(4-(dimethylamino)phenyl)-1,3-
butadienyl]-1-methylpyridinium [C3]+ (Chart 1).
(1) Dalton, L. R.; Harper, A. W.; Ghosn, R.; Steier, W. H.; Ziari, M.;
Fetterman, H.; Shi, Y.; Mustacich, R. V.; Jen A. K. Y.; Shea, K. J.
Chem. Mater. 1995, 7, 1060.
(2) Dagani, R. Chem. Eng. News 1996, March 4, 22.
(3) Goze, F.; Laukhin, V. N.; Brossard, L.; Audouard, A.; Ulmet, J. P.;
Askenazy, S.; Naito, T.; Kobayashi, H.; Kobayashi M.; Cassoux, P.
Europhys. Lett. 1994, 28, 427.
(4) Kurmoo, M.; Graham, A. W.; Day, P.; Coles, S. J.; Hursthouse, M.
B.; Caulfield, J. L.; Singleton, J.; Pratt, F. L.; Hayes, W.; Ducasse L.;
Guionneau, P. J. Am. Chem. Soc. 1995, 117, 12209.
(5) (a) Cle´ment, R.; Lacroix, P. G.; O’Hare D.; Evans, J. AdV. Mater.
1994, 6, 794. (b) Lacroix, P. G.; Cle´ment, R.; Nakatani, K.; Zyss J.;
Ledoux, I. Science 1994, 263, 658.
Experimental Section
Starting Materials and Equipment. Acetonitrile was purchased
from SDS and distillated over P2O5 prior to use. (n-Bu4N)[Ni(dmit)2],11
(7) Sutter, K.; Hulliger J.; Gu¨nter, P. Solid State Commun. 1990, 74, 867.
(8) (a) Shan, B. Z.; Zhang, X. M.; You, X. Z.; Fun H. K.; Sivakumar, K.
Acta Cryst. 1996, C52, 1148. (b) Fun, H. K.; Sivakumar, K.; Shan B.
Z.; You, X. Z. Acta Crystallogr. 1996, C52, 1152.
(9) Lacroix P. G.; Nakatani, AdV. Mater. 1997, 9, 1105.
(10) (a) Brossard, L.; Ribault, M.; Valade L.; Cassoux, P. Phys. B 1986,
143, 378. (b) Cassoux, P.; Valade, L.; Kobayashi, H.; Kobayashi, A.;
Clark, R. A.; Underhill, A. Coord. Chem. ReV., 1991, 110, 115. (c)
Cassoux P.; Valade, L. In Inorganic Materials; Bruce D. W., O’Hare,
D., Eds.; Wiley: Chichester, 1992; pp 1-58.
(6) Yu, L.; Chan, W. K.; Peng Z.; Gharavi, A. Acc. Chem. Res. 1996, 29,
13.
S0020-1669(97)01550-4 CCC: $15.00 © 1998 American Chemical Society
Published on Web 06/06/1998

3362 Inorganic Chemistry, Vol. 37, No. 13, 1998
Malfant et al.
anisotropic thermal parameters have been deposited at the Cambridge
Crystallographic Data Center.
Chart 1
Electronic Band Structure Calculations. The electronic structures
were obtained on the basis of extended Hu¨ckel19 tight-binding (EHTB)
band structure calculations.20 The off-diagonal matrix elements of the
effective Hamiltonian were calculated according to the modified
Wolfsberg-Helmholz formula. The exponents, contraction coefficients,
and atomic parameters used in the calculations are tabulated as
previously reported.21
Conductivity. Temperature-dependent single-crystal conductivity
measurements were carried out following the standard four-probe
technique. Electrical contacts were obtained by gluing four gold wires
to the crystal with Emetron M8001 gold paint. The sample mounted
on a Motorola printed circuit was placed in an Oxford Instruments
model CF 200 continuous-flow cryostat. Temperature control and
temperature-resistance data acquisition were achieved using an Oxford
Instruments model DTC2 PID temperature controller, and a Hewlett-
Packard model 4263A LCR meter, respectively, both driven by a
personal computer running in-house software. Powder conductivity
measurements were carried out on pressed pellets of pure powder
materials (size: 1 mm2 × about 1 mm) obtained by careful grinding.
The cylinders used to press the materials were used as electrodes.
Results and Discussion
Synthesis. Every material presented in this study is obtained
by slow diffusion of [Ni(dmit)2]- anions through a solution
containing the appropriate [C]+ countercation. Contrary to what
was reported in our previous paper based on TCNQ0/TCNQ-
mixed-valence species, the highly unsoluble neutral [Ni(dmit)2]
compound is not a convenient starting material. The syntheses
have to be carried out with [Ni(dmit)2]- as the only nickel-
containing species allowed to react with [C]+. After 2 months
of slow diffusion, two types of single crystals were obtained
with [C1]+: black elongated plates designated hereafter as phase
1, and diamond-shaped dark solid designated hereafter as phase
2. Both phases have been characterized by X-ray diffraction
studies (see below) as having the same 1:1 [C1][Ni(dmit)2]
stoichiometry. Likewise, two types of single crystals were
obtained with [C2]+, as thick plates and square plates labeled
hereafter phase 3 and 4 respectively, and having the same 1:1
[C2][Ni(dmit)2] stoichiometry, as shown by X-ray studies.
Description of Structures. [C1][Ni(dmit)2] (Phase 1). The
asymmetric unit is shown in Figure 1 with the atomic numbering
scheme used. It consists of two planar [Ni(dmit)2] entities
labeled A and B, (largest deviations from planarity are 0.106
Å for S(5) in A and 0.072 for S(15) in B) and two [C1]+ cations.
No atoms are in special positions. A collection of some relevant
intramolecular distances is given in Table 2 for the [Ni(dmit)2]
species. The mean Ni-S distances are 2.165(1) and 2.164(1)
Å for molecules A and B, respectively, which is somewhat larger
than those observed for other compounds of general formula
[Cat]+[Ni(dmit)2]- were [Cat]+ is a closed-shell cation. For
comparison, the Ni-S distances observed for [Cat]+ ) [NMe4]+,
[NEt4]+, [NPr4]+, and [NBu4]+ are 2.158(3),22 2.157(4),23 2.160-
(3),22 and 2.15624 Å, respectively. However, this result is in
agreement with the situation encountered in [C6H11N2]+-
4-(dimethylamino)-1-methylpyridinium [C1]+,12 4-[2-(4-(dimethyl-
amino)phenyl)ethenyl]-1-methylpyridinium [C2]+,13 and 4-[4-(4-(di-
methylamino)phenyl)-1,3-butadienyl]-1-methylpyridinium [C3]+,14,15
were synthesized as previously described. Elemental analyses were
performed by the “Service de Microanalyses du Laboratoire de Chimie
de Coordination” in Toulouse, France.
Synthesis. Crystals were obtained by slow interdiffusion of saturated
solution of (n-Bu4N)[Ni(dmit)2] and [C1]+I- or [C2]+I-. These experi-
ments were carried out under argon, in a three-compartment H-tube
equipped with porous glass frits between the compartments. The
concentrations of the solutions were kept close to saturation during
the diffusion process by means of additional porous containers placed
in the appropriate compartment and filled with an excess of solid starting
reagents. Attempts to grow crystals from [C3]+I- were unsuccessful
and, therefore, [C3][Ni(dmit)2] has been obtained as powder samples
only. Anal. Calcd for C22H21N2NiS10: C, 40.22; H, 2.95; N, 3.91.
Found: C, 41.7; H, 2.6; N, 4.0.
Structure Analysis and Refinement. The structures were solved
by direct methods (SHELXS86)16 and refined by least-squares proce-
dures. Crystallographic data for [C1][Ni(dmit)2] and [C2][Ni(dmit)2]
are summarized in Table 1. The calculations were carried out with
the CRYSTALS package programs17 running on a PC. The drawings
of the molecular structures were obtained with the help of CAM-
ERON.17 The atomic scattering factors were taken from International
Tables for X-ray Crystallography.18 Full X-ray data, fractional atomic
coordinates, and the equivalent thermal parameters for all atoms and
(11) (a) Steimecke, G.; Sieler, H. J.; Kirmse R.; Hoyer, E. Phosphorous
Sulfur 1979, 7, 49. (b) Valade, L.; Legros, J. P.; Bousseau, M.;
Cassoux, P.; Garbauskas M.; Interrante, L. J. Chem. Soc., Dalton
Trans. 1985, 783.
(12) Rollema, H.; Johnson, E. A.; Booth, R. G.; Caldera, P.; Lampen, P.;
Youngster, S. K.; Trevor, A. J.; Naiman N.; Castagnoli, N. J. Med.
Chem. 1990, 33, 2221.
(13) Kung, T. K. J. Chin. Chem. Soc. 1978, 25, 131.
(14) Duan, X. M.; Okada, S.; Oikawa, H.; Matsuda H.; Nakanishi, H. Mol.
Cryst. Liq. Cryst. 1995, 267, 89.
(15) Matsui, M.; Kawamura, S.; Shibata, K.; Muramatsu, H. Bull. Chem.
Soc. Jpn. 1992, 65, 71.
(19) (a) Hoffmann, R. J. Chem. Phys. 1963, 39, 1397. (b) Ammeter, J. H.;
B.; Bu¨rgi, H. B.; Thibeault, J.; Hoffmann, R. J. Am. Chem. Soc. 1978,
100, 3686.
(16) Sheldrick G. M. SHELXS86: Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(17) (a) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P. W.
CRYSTALS, Issue 10; Chemical Crystallography Laboratory, University
of Oxford: Oxford, England, 1996. (b) Watkin, D. J.; Prout, C. K.;
Pearce, L. J. CAMERON; Chemical Crystallography Laboratory,
University of Oxford: Oxford, England, 1996.
(20) Whangbo, M.-H.; Hoffman, R. J. Am. Chem. Soc. 1978, 100, 6093.
(21) Canadell, E.; Rachidi, I. E.-I.; Ravy, S.; Pouget, J. P.; Brossard, L.;
Legros, J. P., J. Phys. France 1989, 50, 2967.
(22) van Diemen, J. H.; Groeneveld, L. R.; Lind, A.; de Graaff, R. A. G.;
Haasnoot, J. G.; Reedijk, J. Acta Crystallogr. 1988, C44, 1898.
(23) Groeneveld, L. R.; Schuller, B.; Kramer, G. J.; Haasnoot, J. G.;
Reedijk, J. Recl. TraV. Chim. Pays-Bas 1986, 105, 507.
(24) Lindqvist, O.; Andersen, L.; Sieler, H. J.; Steimecke, G.; Hoyer, E.
Acta Chem. Scand. 1982, A36, 855.
(18) Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystal-
lography; Kynoch Press: Birmingham, 1974; Vol. 4.

Nickel Bis(dithiolene)-Cyanine Dye Complexes
Inorganic Chemistry, Vol. 37, No. 13, 1998 3363
Table 1. Crystal Data for [C1][Ni(dmit)2] (Phases 1 and 2) and [C2][Ni(dmit)2] (Phases 3 and 4)
1
2
3
4
crystal data
formula
C28H26N4Ni2S20
1177.2
C28H26N4Ni2S20
1177.2
C22H19N2NiS10
690.7
C22H19N2NiS10
690.7
M (g mol-1
)
crystal shape
color
size (mm)
crystal system
space group
a (Å)
elongated plates
black
0.75 × 0.1 × 0.05
monoclinic
P21/c
17.450(2)
10.646(1)
diamond shapes
black
thick plates
black
0.3 × 0.425 × 0.04
monoclinic
P21/c
9.813(1)
11.589(1)
24.345(3)
squared plates
black
0.52 × 0.15 × 0.07
triclinic
P1h
13.432(2)
16.101(2)
6.553(1)
99.69(1)
94.34(1)
102.88(2)
1347
0.57 × 0.5 × 0.12
triclinic
P1h
9.776(1)
15.195(2)
16.999(2)
114.14(1)
101.84(1)
93.40(1)
2226.1
b (Å)
c (Å)
23.891(2)
R (°)
â (°)
97.42(1)
93.12(1)
γ (°)
U (Å3)
4401.1
4
2765
4
Z
2
2
Dc
F(000)
1.776
2403.1
1.756
1201.5
1.66
1417.6
1.70
708.8
data collection
diffractometer
monochromator
µ(Mo KR) (cm-1
temperature (K)
scan mode
scan range φ (deg)
2θ range (deg)
absorption correction
no. of reflcns collcd
no. of indep reflcns
no. of indep obsd reflcns
range of h, k, l
IPDS Stoe
graphite
18.0
160
φ
0 < φ < 200
2.9 e 2θ e 48.4
none
28 505
6928
4836 [I > 0.5σ(I)]
-15e h e 15
0 e k e 12
0 e l e 27
not significant
IPDS Stoe
graphite
17.8
293
φ
0 < φ < 250.5
2.9 e 2θ e 48.4
none
17 675
6533
5305 [I > 2σ(I)]
-11e h e 10
-17e k e 15
0e l e 19
not significant
IPDS Stoe
graphite
14.5
293
φ
0 < φ < 200.2
2.9 e 2θ e 48.4
none
16 184
4164
2311 [I > 3σ(I)]
-11e h e 11
0e k e 13
0e l e 27
not significant
Enraf-Nonius CAD4
graphite
14.8
293
ω/2θ
0.80 + 0.35 tan θ
θmax ) 25°
none
5205
4752
2947 [I > 3σ(I)]
-16e h e 16
-19e k e 19
0e l e 7
)
variation in standards (%)
not significant
refinement
refinement on
F
F
F
F
Ra
0.0480
0.0408
0.0382
0.0458
0.0253
0.0256
0.0255
0.0289
wRb
no. of reflections used
no. of reflcns used in refinement
no. of variables
H-atom treatment
4836
488
calculated
5305
520
calculated for CH3
otherwise refined
isotropically
Chebychev
1.101
2311
391
2947
391
refined isotropically
refined isotropically
weighting scheme
coeff. Ar
Chebychev
1.676
1.687
1.829
0.680
0.507
0.04
0.61
-0.81
1.09
Chebychev
1.557
0.475
1.822
0.180
0.536
0.09
0.34
-0.24
1.11
Chebychev
3.608
-3.116
2.744
0.823
0.711
-1.079
(∆/σ)max
0.06
0.41
-0.57
1.00
0.03
0.40
-0.21
1.14
∆Fmax (e Å-3
)
)
∆Fmin (e Å-3
GOF
a R ) ∑(||Fo| - |Fc||)/∑(|Fo|). b wR ) ∑w(|Fo| - |Fc|)2/∑w(Fo)2]1/2
.
[Ni(dmit)2]- reported by Reedijk et al.25 According to these
authors, the overall electronic structure of [Ni(dmit)2] may be
slightly modified through possible π-overlap of the orbital of
the cations with those of the anions, but is still very far from
the 2.216(6) Å reported for [Ni(dmit)2]2- derivatives.26 In
conclusion, the charge of [Ni(dmit)2] is undoubtedly -1.
A projection of the structure of 1 onto the bc plane is shown
in Figure 2. The structure is made up of layers of [Ni(dmit)2]-
anions separated by layers of [C1]+ cations. The angle between
the mean planes of two independent [Ni(dmit)2]- anions with
short S‚‚‚S contacts (A and B) is 10.19°. The intralayer distance
is equal to 5.209 Å. A projection of the anions onto the ac
plane (Figure 3) reveals that the [Ni(dmit)2]- units are organized
in a two dimensionnal network of molecules connected through
short S‚‚‚S van der Waals contacts (<3.7 Å). Three short S‚‚‚S
distances between neighboring molecules are observed along
the [001] direction versus only one along the [100] direction,
the latter one involving the external thione groups. The lengths
of S‚‚‚S contacts are gathered in Table 3. Between the
[Ni(dmit)2]- planes, layers of [C1]+ cations are inserted, their
molecular planes roughly parallel to the [Ni(dmit)2]- layers. A
projection onto the ac plane is shown in Figure 4. It reveals
that although phase 1 is centrosymmetric (space group P21/c),
the [C1]+ cations are engineered in a noncentrosymmetric
(25) Reefman, D.; Cornelissen, J. P.; Haasnoot, J. G.; de Graaff, R. A. G.;
Reedijk, J. Inorg. Chem. 1990, 29, 3933.
(26) Lindqvist, O.; Sjo¨lin, L.; Sieler, J.; Steimecke, G.; Hoyer, E. Acta
Chem. Scand. 1979, A33, 445.

3364 Inorganic Chemistry, Vol. 37, No. 13, 1998
Malfant et al.
Figure 1. Asymmetric unit and atomic labeling system for [C1][Ni(dmit)2] (phase 1). H atoms are omitted for clarity.
Table 2. Selected Bond Lengths (Å) for [C1][Ni(dmit)2] (Phases 1 and 2) and for [C2][Ni(dmit)2] (Phases 3 and 4) (A and B Refer to the Two
Nonequivalent [Ni(dmit)2]- Present in Phases 1 and 2)
phase 1
phase 2
compound [C2][Ni(dmit)2]
phase 3 phase 4
molecule A
molecule B
molecule A
molecule B
Ni(1)-S(1) 2.163(1) Ni(2)-S(11) 2.163(1) Ni(1)-S(1) 2.1648(8) Ni(2)-S(11) 2.1584(9) Ni(1)-S(1) 2.167(1) Ni(1)-S(1) 2.1634(8)
Ni(1)-S(2) 2.162(1) Ni(2)-S(12) 2.166(1) Ni(1)-S(2) 2.1639(8) Ni(2)-S(12) 2.1740(8) Ni(1)-S(2) 2.154(1) Ni(1)-S(2) 2.1709(8)
Ni(1)-S(6) 2.165(1) Ni(2)-S(16) 2.164(1) Ni(1)-S(6) 2.1684(8) Ni(2)-S(16) 2.1822(9) Ni(1)-S(6) 2.161(1) Ni(1)-S(6) 2.1579(8)
Ni(1)-S(7) 2.169(1) Ni(2)-S(17) 2.164(1) Ni(1)-S(7) 2.1650(8) Ni(2)-S(17) 2.1631(8) Ni(1)-S(7) 2.156(1) Ni(1)-S(7) 2.1663(8)
S(1)-C(1) 1.713(5) S(11)-C(7) 1.730(5) S(1)-C(1) 1.716(3) S(11)-C(7) 1.707(3) S(1)-C(1) 1.717(4) S(1)-C(1) 1.709(3)
S(2)-C(2) 1.695(5) S(12)-C(8) 1.715(5) S(2)-C(2) 1.711(3) S(12)-C(8) 1.720(3) S(2)-C(2) 1.710(4) S(2)-C(2) 1.720(3)
S(6)-C(4) 1.720(5) S(16)-C(10) 1.727(5) S(6)-C(4) 1.718(3) S(16)-C(10) 1.723(3) S(6)-C(4) 1.703(4) S(6)-C(4) 1.699(3)
S(7)-C(5) 1.728(5) S(17)-C(11) 1.719(4) S(7)-C(5) 1.714(3) S(17)-C(11) 1.717(3) S(7)-C(5) 1.699(4) S(7)-C(5) 1.710(3)
Figure 2. Projection of the [C1][Ni(dmit)2] unit of phase 1 onto the
bc plane.
environment between the layers of anions. The angle between
the two longitudinal nitrogen-nitrogen axis of the cations is
equal to 115.07°.
[C1][Ni(dmit)2] (Phase 2). The asymmetric unit contains two
planar [Ni(dmit)2] entities labeled A and B (largest deviations
are 0.135 Å for S(15) in A and 0.092 for S(20) in B) and two
[C1]+ cations, with the same atom labeling as in phase 1. A
collection of some relevant intramolecular distances in the
[Ni(dmit)2]- species is given in Table 2. The mean Ni-S
Figure 3. Projection of the [Ni(dmit)2] layers onto the ac plane for
[C1][Ni(C3S5)2] (phase 1). The dotted lines represent the S‚‚‚S distances
shorter than the sum (3.7 Å) of the van der Waals radii.
distances are 2.166(1) and 2.169(1) Å for molecules A and B,
respectively, which is very similar to what is observed in phase

Nickel Bis(dithiolene)-Cyanine Dye Complexes
Table 3. S‚‚‚S Intermolecular Contacts (<3.7 in Å) for [C1][Ni(dmit)2] (Phases 1 and 2) and [C2][Ni(dmit)2] (Phases 3 and 4)
phase 1 phase 2 phase 3 phase 4
Inorganic Chemistry, Vol. 37, No. 13, 1998 3365
atomsa
distances
atomsb
distances
atomsc
distances
atomsd
distances
S(1)-S(11i)
S(1)-S(13i)
S(7)-S(13i)
S(2)-S(2ii)
3.648 (2)
3.418 (2)
3.513 (2)
3.645 (2)
3.635 (2)
3.489 (2)
3.475 (2)
3.490 (2)
3.539 (2)
S(2)-S(13i)
S(6)-S(13i)
S(7)-S(9ii)
S(5)-S(10iii)
S(15)-S(20iii)
S(12)-(14iv)
3.573 (1)
3.539 (1)
3.490 (1)
3.469 (1)
3.597 (1)
3.509 (1)
S(2)-S(2i)
S(2)-S(4i)
S(4)-S(10ii)
3.667 (2)
3.496 (1)
3.662 (2)
S(1)-S(2i)
S(1)-S(6i)
S(7)-S(6i)
S(3)-S(2i)
S(7)-S(8i)
S(1)-S(7ii)
S(4)-S(5iv)
S(5)-S(5v)
3.663 (1)
3.491 (1)
3.661 (1)
3.618 (1)
3.602 (1)
3.699 (1)
3.608 (1)
3.670 (2)
S(2)-S(4ii)
S(5)-S(10iii)
S(20)-S(15iii)
S(12)-S(12iv)
S(14)-S(16iv)
a Symmetry operations for second atom: (i) x, y, z; (ii) 1 - x, 1 - y, 1 - z; (iii) 1 + x, y, z; (iv) 1 - x, 1 - y, -z. b Symmetry operations for
second atom: (i) x, y, z; (ii) -x, -y, 1 - z; (iii) x + 1, y + 1, z; (iv) 2 - x, -y, 2 - z. c Symmetry operations for second atom: (i) 1 - x, -y,
1 - z; (ii) -x, -y, 1 - z. d Symmetry operations for second atom: (i) x, y, z - 1; (ii) 2 - x, 2 - y, -z; (iii) 1 - x, 1 - y, -z; (iv) 1 - x, 1 -
y, -1 - z.
Figure 4. Projection of [C1]+ layers onto the ac plane for [C1][Ni-
(dmit)2] (phase 1) showing the acentric environment of the chro-
mophores. H atoms are omitted for clarity.
1. Consequently, a -1 charge can be assigned for [Ni(dmit)2]
species in this compound.
At first, the overall structure of phase 2 seems to be very
Figure 5. Projection of the [Ni(dmit)2] layers onto the (1h12) plane
for[C1][Ni(dmit)2] (phase 2). The dotted lines represent the S‚‚‚S
distances shorter than the sum (3.7 Å) of the van der Waals radii.
closely related to that of phase 1. It consists on layers of
overlapping [Ni(dmit)2]- anions in the (1h12) plane, separated
by layers of [C1]+ cations. The angle between the mean planes
of the two independent [Ni(dmit)2]- anions (A and B) is 3.06°.
The interlayer distance is equal to 5.603 Å versus 5.209 Å for
phase 1. A projection of the anions onto the (1h12) plane (Figure
5) reveals that the [Ni(dmit)2]- units are organized in a two
dimensionnal network through short S‚‚‚S van der Waals
contacts (<3.7 Å). A careful comparison of Figures 3 and 5
reveals an important difference between phases 1 and 2, mainly
involving the orientation of the B [Ni(dmit)2]- units in the cell.
These anions are slightly shifted apart from one another along
the [110] direction in phase 2 and along the [1h12] direction
(perpendicular to the mean plane of the [Ni(dmit)2]- layer), the
distance between their molecular planes reaching 1.817 Å versus
1.598 Å in phase 1. Consequently, the S‚‚‚S short contacts are
modified, with a loss of one-third of the short S‚‚‚S contacts
along the [201] direction. Compared to phase 1, another major
difference is observed in phase 2. A layer of [C1]+ cations is
shown in Figure 6. Contrary to the situation encountered in
phase 1, the cations are engineered in a centrosymmetric
environment within their layers in phase 2.
Figure 6. Projection of the centrosymmetric [C1]+ layers onto the (1h12)
plane for [C1][Ni(dmit)2] (phase 2). H atoms are omitted for clarity.
[Ni(dmit)2]- anion is planar (largest deviation 0.062 Å for S(5)).
A projection of the structure onto the bc plane is shown in Figure
8. The structure consists on alternating chains of [Ni(dmit)2]-
anions and [C2]+ cations. The anionic chains, which run along
the [100] direction, are built of diades of [Ni(dmit)2]- (inter-
planar distance 3.561 Å) (Figure 9) linked to each other through
S‚‚‚S contacts (Table 3). The angle between the [100] direction
[C2][Ni(dmit)2] (Phase 3). The asymmetric unit with the
atomic numbering scheme is shown in Figure 7. Intramolecular
distances are in agreement with those found in the previous
compound [C1][Ni(dmit)2]. Therefore, as for phases 1 and 2,
the -1 charge can be assigned to the [Ni(dmit)2] unit. The

3366 Inorganic Chemistry, Vol. 37, No. 13, 1998
Malfant et al.
Figure 7. Asymmetric unit and atomic labeling system for [C2][Ni(dmit)2] (phase 3).
Figure 8. Projection of [C2][Ni(dmit)2] unit (phase 3) onto the bc plane.
and the plane of the [Ni(dmit)2] units is 36.98°. The cations
[C2]+ are not planar: the angle between the two unsaturated
rings is 10.54°. Nevertheless, the averaged planes of the [C2]+
cations are almost parallel to the planes of the [Ni(dmit)2]- units
(6.27°), but the directions of the longitudinal axis of each
molecule form an angle of 6.84°.
of the [Ni(dmit)2]- units (94.7°). Opposite to the monoclinic
phase 3, the cations are much more planar: the dihedral angle
between the two rings is only 3.2° and the largest deviation is
only 0.064 Å for C(19). Along the [001] direction, the cations
are stacked head-to-head with an interplanar distance of 3.58
Å, but the adjacent stacks are oriented in such a way that the
dimethylamino groups are always pointed toward each other
(Figure 12).
Conductivity. The conductivities recorded on single crystals
or powder samples are gathered in Table 4. [C1][Ni(dmit)2]
(phase 2), [C2][Ni(dmit)2] (phases 3 and 4), and [C3][Ni(dmit)2]
all exhibit modest powder conductivities in the range10-6-10-5
S cm-1, as expected for integral oxidation state 1:1 salts, with
a tendency for slightly higher conductivity in [C2][Ni(dmit)2].
Due to small sizes and squared crystal shapes, no measurements
on single crystals could be performed for these three phases.
By contrast, very few crystals of phase 1 were obtained, which
did not allow a conductivity measurement on powder sample.
However, due to their elongated shape, four probes of conduc-
tivity measurements were possible on a single crystal for this
phase. The room-temperature conductivity is rather high, 1.3
× 10-2 S cm-1 with an activation energy (Ea) of 0.05 eV, which
is surprising for such a 1:1 salt. Indeed, most of the 1:1 salts
[C2][Ni(dmit)2] (Phase 4). As for phase 3, the asymmetric
unit contains one [Ni(dmit)2]- anion and one [C2]+ cation with
the same labeling used in Figure 7. In this compound, the
[Ni(dmit)2]- units are not as planar as in phase 3: the largest
deviations are 0.165 and 0.140 Å for S(10) and S(5), respec-
tively, indicating a slightly bent structure of the anions. A
projection of the structure onto the ab plane is shown in Figure
10. The structure is reminiscent of those of [C1][Ni(dmit)2] (1
and 2) and consists of layers of [Ni(dmit)2]- separated by layers
of [C2]+ cations. Contrary to phases 1 and 2, the anionic layers
are built of pairs of [Ni(dmit)2]- (interplanar distance 3.65 Å)
linked to each others through short S‚‚‚S contacts (Table 3).
Transverse S‚‚‚S contacts between neighboring molecules are
present along the [001] direction (Figure 11) and along the [110]
direction, the latter ones involving the external thione groups
(Figure 10). The [C2]+ cations lie between these layers and
are arranged in a perpendicular way with respect to the plane

Nickel Bis(dithiolene)-Cyanine Dye Complexes
Inorganic Chemistry, Vol. 37, No. 13, 1998 3367
Figure 9. Structure of phase 3 showing the chains of [Ni(dmit)2]- along the [100] direction.
Figure 10. Projection of [C2][Ni(dmit)2] unit (phase 4) onto the ab plane.
of [Ni(dmit)2]- with closed-shell type cations such as NR4+ (R
in the conductivity of phase 1 can be tentatively understood
+
) alkyl), or SMexEt3-x (x ) 1, 2, 3) exhibit conductivities
from the examination of the crystal structure. These contacts
correspond to a possible interplane path of conductivity. The
values of the charge-transfer integrals (â) are gathered in Table
5. The data reveal very small â values in the ac plane (Figure
3). While the conductivity in the [001] direction is limited by
the weak B‚‚‚B interaction (â ) 0.0001 eV through (iv)
lower than 10-5 S cm-1
.
The origin of the conductivity is well understood in these
systems and depends on short S‚‚‚S contacts between [Ni(dmit)2]-
units, the cation being not involved in the electronic properties
of the material. The role of the S‚‚‚S short contacts (Table 3)

3368 Inorganic Chemistry, Vol. 37, No. 13, 1998
Malfant et al.
Table 4. Conductivities (S cm-1) for [C1][Ni(dmit)2],
[C2][Ni(dmit)2], and [C3][Ni(dmit)2]
conductivity
powder crystal
compound
phase
[C1][Ni(dmit)2]
1
2
3
4
1.3 × 10-2
10-6
[C2][Ni(dmit)2]
[C3][Ni(dmit)2]
10-6 to 10-5
10-6 to 10-5
10-5
Table 5. Transfer Integrals (eV) Calculated with the Partially
Filled [Ni(dmit)2]- Orbital (Orbital 48) in Several Directions for
[C1][Ni(dmit)2] (Phases 1 and 2) and [C2][Ni(dmit)2] (Phases 3 and
4)
Figure 11. Details of the short S‚‚‚S contacts along the [001] direction
for [C2][Ni(dmit)2] (phase 4).
contacts), the largest interactions are calculated along the [100]
direction but are still very modest. This can be qualitatively
understood as the result of a π overlap of π orbitals. More
interestingly, although no short distances are present along the
[010] direction, they correspond to nearly parallel orientations
of the molecular units, therefore to σ overlaps of π orbitals
associated with large â value (0.1662 eV for A‚‚‚B through V
contact). Thus, two paths of conduction can be considered in
the bc plane along the [021] and [02h1] directions, both involving
B‚‚‚A (v) A‚‚‚A (ii) A‚‚‚B (v) B‚‚‚A (i) interactions and
avoiding the weakest B‚‚‚B (iv) interaction.
A similar investigation conducted on phase 2 reveals the same
general trend for modest â values in the (1h12) plane even if
short S‚‚‚S are present. As observed in phase 1, the possibility
of large σ overlap along the [1h12] direction allow two paths of
conduction in the ac plane along the [100] and [001] directions.
Phase 3 exhibits a strong one-dimensionnal character, with a
conductivity likely dominated by the weak (i) interaction (â )
0.0177 eV) along the [100] direction, while phase 4 exhibits
several S‚‚‚S short contacts in the (11h0) plane (Figures 10 and
11), all of them being associated with modest â values.
In the above discussion, the cations were assumed to play
no role in the conducting properties. Actually, cations with
delocalized π system such as 1,2,3-trimethylimidazolium were
investigated first by Reedijk et al. with the hope of changing
the overall electronic structure through possible π overlap
between cations and anions.25 Such an effect would be expected
not only to enhance the conductivity, but also to increase the
molecular hyperpolarizability of the NLO chromophore, as
previously reported.27 Although no charge transfer is observed
between cations and anions, it is interesting to note that several
short distances are observed in the crystal structures (Table 6),
although their possible role in the conduction mechanism is not
clear. In conclusion, the overall examination of Table 5
indicates transfer integrals lying in the same range of magnitude
for every phase investigated in the present study, in agreement
with the crystal structures which exhibit the same general
features.
symmetry
phase
direction
contact
operationa
â
1
ac plane
[100]
A‚‚‚A
B‚‚‚B
A‚‚‚A
A‚‚‚B
B‚‚‚B
iii
iii
ii
i
iv
0.0051
0.0047
0.0068
0.0081
0.0001
[001]
bc plane
[010]
(1h12) plane
[110]
B‚‚‚A
vb
0.1662
2
A‚‚‚A
B‚‚‚B
A‚‚‚A
iii
iii
ii
0.0017
0.0051
0.0002
[201]
ac plane
[1h12]
A‚‚‚A
B‚‚‚B
vb
vb
i
0.2688
0.1281
0.0177
0.2214
3
4
[100]
ii
ab plane
i
ii
iii
iv
vc
0.0059
0.0375
0.0019
0.0035
0.0360
a Symmetry operations are labeled according to Table 3. b Symmetry
operations for second molecule 1 - x, 1/2 + y, 1/2 - z (v). c Symmetry
operation for second molecule 2 - x, 2 - y, 1 - z (v).
with the aim of preparing ferromagnetically ordered molecular-
based charge-transfer salts.31-33 To the best of our knowledge,
the present work is the first attempt of combining [Ni(dmit)2]
with cationic cyanine dyes, which have emerged as promising
candidates for second-order optical nonlinearities.5,34 However,
one of the main bottlenecks to the development of such materials
is the compulsory noncentrosymmetric environment of the
chromophores if the molecular hyperpolarizability (â) is to
contribute to an observable bulk nonlinear susceptibility (ø2).35
Various strategies have been reported for the engineering of
molecules into noncentrosymmetric arrangements, but the most
traditional approach, which guarantees stable noncentrosym-
Multiproperty [Ni(dmit)2]-Based Materials Exhibiting
Second-Order Optical Nonlinearity. A great deal of work
has been devoted to the study of compounds derived from
M(dmit)2 complexes, with the aim of extending the range of
molecular conductors and superconductors based on transition-
metal complexes.10 More recently, metal-bis(dithiolene) was
combined with paramagnetic metallocenium counterions,28-30
(30) (a) Matsubayashi, G.; Yokozawa, A. Inorg. Chim. Acta 1992, 193,
137. (b) Tanaka, S.; Matsubayashi, G. J. Chem. Soc., Dalton Trans.
1992, 2837. (c) Matsubayasi, G.; Yokozawa, A. J. Chem. Soc., Dalton
Trans. 1990, 3535.
(31) Broderick, W. E.; Thompson, J. A.; Day, E. P.; Hoffman, B. M. Science
1990, 249, 401.
(32) (a) Miller, J. S.; Epstein, A. J. Angew. Chem., Int. Ed. Engl. 1994,
33, 385. (b) Chem. Eng. News 1995, 73, 30.
(33) Proceedings of the Conference on Molecular-Based Magnets. Mol.
Cryst. Liq. Cryst. 1995, 271.
(34) (a) Marder, S. R.; Perry, J. W.; Yakymyshyn, C. P. Chem. Mater.
1994, 6, 1137. (b) Marder, S. R.; Perry J. W.; Schaefer, W. P. J. Mater.
Chem. 1992, 2, 985; (c) Marder, S. R.; Perry J. W.; Schaefer, W. P.
Science 1989, 245, 626.
(27) Di Bella, S.; Ratner, M. A.; Marks, T. J. J. Am. Chem. Soc. 1992,
114, 5842.
(28) Miller, J. S.; Calabrese, J. C.; Epstein, A. J. Inorg. Chem. 1989, 28,
4230.
(29) Broderick, W. E.; Thompson, J. A.; Godfrey, M. R.; Sabat, M.;
Hoffman, B. M. J. Am. Chem. Soc. 1989, 111, 7656.
(35) Williams, D. J. Angew. Chem., Int. Ed. Engl. 1984, 23, 690.

Nickel Bis(dithiolene)-Cyanine Dye Complexes
Inorganic Chemistry, Vol. 37, No. 13, 1998 3369
Figure 12. Projection of [C2]+ layers onto the (11h0) plane for [C2][Ni(dmit)2] (phase 4), showing the stacking of cations along the a direction.
Table 6. Short Intermolecular Distances (<3.6 Å) between Cations and Anions (in Å) for [C1][Ni(dmit)2] (Phases 1 and 2) and
[C2][Ni(dmit)2] (Phases 3 and 4)
symmetry
operations
symmetry
operations
atoms
distances
Phase 1
atoms
distances
Phase 2
3.544(1)
3.558(1)
3.527(1)
3.473(1)
3.569(1)
3.562(1)
S(2)-C(21)
S(3)-C(26)
S(4)-C(22)
S(5)-C(17)
S(5)-C(20)
S(8)-C(15)
S(9)-C(13)
C(21)-S(12)
C(25)-S(17)
C(27)-S(11)
S(19)-N(2)
3.598(1)
3.547(1)
3.563(1)
3.590(1)
3.546(1)
3.583(1)
3.573(1)
3.541(1)
3.581(1)
3.562(1)
3.575(1)
1 - x, 1 - y, -z
x, y - 1, z
x, y - 1, z
S(3)-C(23)
S(4)-N(4)
S(4)-C(27)
S(10)-C(24)
S(19)-N(3)
S(16)-C(21)
x, 1 + y, z
x, 1 + y, z
x, 1 + y, z
x, y, z
x, y, z
x, y, z
1 - x, 1 - y, -z
1 - x, y - 1/2, -z + 1/2
x, y - 1, z
x, y - 1, z
1 - x, y + 1/2, -z + 1/2
x, 1 + y, z
1 - x, y + 1/2, -z + 1/2
1 - x, y - 1/2, -z + 1/2
Phase 3
3.572(1)
3.538(1)
Phase 4
3.564(1)
S(7)-C(21)
S(9)-C(22)
-x, -y, 1 - z
-x, -y, 1 - z
S(6)-C(11)
x, 1 + y, 1 + z
metric organizations of NLO chromophores in the solid state,
is based on the possibility of growing large noncentrosymmetric
stand edge-on to the slabs of the host [M2P2S6].5 This trend is
observed here also. It can therefore be expected from these
similar structural features that two-dimensional [Ni(dmit)2]
materials containing NLO chromophores should offer a promis-
ing approach toward multiproperty materials as do [M2P2S6]
lamellar compounds.
single crystals with a high phase-matchable coefficient.36
A
promising approach for reaching this goal, first explored by
Meredith,37 involves the use of cationic chromophores combined
with various counteranion. This author observed that most salts
of [C2]+ are noncentrosymmetric. Among them [C2]+[CH3-
OSO3]+ exhibited the highest second-order nonlinearity reported
at that time.35 It is now well established that variation of
counteranions in these stilbazolium salts is a simple and
successful approach for engineering a variety of crystalline
materials with large macroscopic optical nonlinearities.34 Un-
fortunatly, none of the compounds reported in this paper
crystalized in noncentrosymmetric space group. Indeed, a
statistical search conducted on every reported structure contain-
ing [Ni(dmit)2] reveals that only two structures in about one
hundred entries actually are noncentrosymmetric.
Further interest arises from the comparison of the physical
+
properties of both family of materials. [Mn1.72P2S6][C2
]0.56 was
found to exhibit an efficiency of several hundreds times that of
urea in second-harmonic generation.5 This was tentatively
explained by agregation of [C2]+ species in noncentrosymmetric
alignments during the intercalation process into [Mn2P2S6].39
Without crystal structures, it was not possible to establish
unambiguously the origin (kinetic or thermodynamic) of the
behavior. Interestingly [C1][Ni(dmit)2] (phase 1) proves the
possibility of thermodynamic stability for noncentrosymmetric
alignments of cations between guest layers of sulfur atoms. In
It is interesting to relate the layered structures of [C1][Ni-
(dmit)2] and [C2][Ni(dmit)2] to those of the same cations
intercalated into [M2P2S6] (M ) Mn2+, Cd2+). These com-
pounds form a class of lamellar materials made up of [M]2+
cations and [P2S6]4- anions, which were recently reported as a
promising family of magnetic-NLO multiproperty molecular
materials.5 The overall structural features of [M2P2S6]- and [Ni-
(dmit)2]-based structures (phases 1, 2, and 4) bear some
ressemblance: they both show lattice of sufur atoms bearing
negative charges in which [C1]+ and [C2] + cations are inserted.
It was observed that small size pyridinium derivatives (such as
[C1]+) are intercalated with their molecular planes parallel to
+
addition, [Mn1.72P2S6][C2
]0.56 was reported to exhibit permanent
magnetization under 40 K even if no interplay was observed
between NLO and magnetic properties. [Ni(dmit)2] is expected
to bring the NLO materials with additional conducting proper-
ties. The observation of short distances between chromophores
and [Ni(dmit)2]- species suggests that possible π-overlap
between cations and anions could slightly modify of the overall
electronic structure and hence the conductivity. Another effect
of intermolecular interaction is to modify the molecular hyper-
polarizability of the chromophores. This possibility has been
thoroughly investigated by Di Bella et al.24 Therefore this
family of hybrid organic-inorganic systems could be promising
for engineering multiproperty materials with efficient interplay.
+
the sulfur lattices,38 while C2 and other large chromophores
(36) Zyss J.; Oudar, J. L. Phys. ReV. A 1982, 26, 2028.
(37) Meredith, G. In Nonlinear Optical Properties of Organic and
Polymeric Materials; Williams, D. J., Ed.; ACS Symposium Series
233; American Chemical Society: Washington, DC, 1983; p 27.
(38) Cle´ment, R.; Lomas, L.; Audie`re, J. P. Chem. Mater. 1990, 2, 641.
(39) Coradin, T.; Cle´ment, R.; Lacroix, P. G.; Nakatani, K. Chem. Mater.
1996, 8, 2153.

3370 Inorganic Chemistry, Vol. 37, No. 13, 1998
Malfant et al.
Conclusion
acentric layers of chromophores can be stable in some cases.
This work is a step in the design of new multiproperty that
would theoretically offer potential interest in the emerging
optoelectronic technology.
This work was part of our general research effort aimed at
extending the range of molecular materials combining two
properties in the same crystal. We have found that second-
order NLO chromophores could be successfully inserted into
semiconducting (σ ) 10-6 to 10-2 S cm-1) layers of [Ni(dmit)2]-
anions. Although these materials are found to crystallize in
centrosymmetric space group, the crystal structures reveal that
Acknowledgment. R.A. thanks EEC T/raining and Mobility
of Researchers Program for a postdoctoral fellowship.
IC971550+