Molecular tectonics: Homochiral coordination networks based on combinations of a chiral neutral tecton with Hg(ii), Cu(ii) or Ni(ii) neutral complexes as metallatectons

Article abstract of DOI:10.1039/c3dt52850b

The use of compound 1 as an enantiomerically pure neutral and rigid organic linear tecton bearing two divergently oriented monodentate coordinating sites appended with two chiral centres of the same (S) configuration leads, in the presence of neutral metal complexes behaving either as a linear (Cu(hfac) ₂, Cu(OAc)₂) or a V-shaped (HgCl₂) 2-connecting node or a 4-connecting square node (NiCl₂), to the formation of four homochiral 1- and 2-D coordination polymers.

Full text of DOI:10.1039/c3dt52850b

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Molecular tectonics: homochiral coordination
networks based on combinations of a chiral
neutral tecton with Hg(II), Cu(II) or Ni(II) neutral
complexes as metallatectons†
Cite this: Dalton Trans., 2014, 43,
2000
Patrick Larpent, Abdelaziz Jouaiti,* Nathalie Kyritsakas and Mir Wais Hosseini*
The use of compound 1 as an enantiomerically pure neutral and rigid organic linear tecton bearing two
divergently oriented monodentate coordinating sites appended with two chiral centres of the same (S)
configuration leads, in the presence of neutral metal complexes behaving either as a linear (Cu(hfac)2,
Cu(OAc)2) or a V-shaped (HgCl2) 2-connecting node or a 4-connecting square node (NiCl2), to the for-
mation of four homochiral 1- and 2-D coordination polymers.
Received 10th October 2013,
Accepted 5th November 2013
DOI: 10.1039/c3dt52850b
www.rsc.org/dalton
Introduction
Molecular networks are extended periodic architectures dis-
playing translational symmetry.1–3 These infinite architectures
are formed upon mutual interconnection of self-complemen-
tary or complementary molecular building blocks called
tectons.4–6 Coordination polymers7 or coordination networks,6
also called metal–organic frameworks,8 form a subclass of
molecular networks for which coordinating organic tectons
are associated with metal cations or metal complexes. The
latter category has attracted considerable interest over the last
two decades9 owing to the various effective or potential appli-
cations they offer in catalysis, storage, sensing or separation
for example.10,11 Although a large number of coordination net-
works has been reported over the last few years, despite the
importance of chirality in biology and in chemistry, a relatively
small number deals with chiral networks.12–20 Among several
possible design principles, chiral coordination networks may
be generated by combining metal centres or metal complexes
with chiral organic tectons. However, a challenge in this area
remains the design and generation of enantiomerically pure
architectures.
Scheme 1
homochiral neutral coordination networks (1·HgCl2, 1·Cu(hfac)2,
1·Cu2(AcO)4 and 1·NiCl2).
Experimental part
Characterization techniques
1H- and 13C-NMR spectra were recorded at 25 °C on a Bruker
AV 300 spectrometer in deuterated solvents with the residual
solvent peak used as the internal reference. Elemental analyses
Herein we report on the combinations of the enantiomeri-
cally pure tecton 1 (see Scheme 1) with three different metal
cations (Hg(II), Cu(II) or Ni(II)) associated with three different
anions (Cl−, hfac− and AcO−) leading to the formation of four
were performed on
a Thermo Scientific Flash 2000 by
the “Service Commun de Microanalyse” of the University of
Strasbourg. Polarimetric measurements were performed on
a Perkin Elmer (model 341) instrument.
Molecular Tectonic Laboratory, UMR UDS-CNRS 7140, icFRC, University of
Strasbourg, Institut Le Bel, 4, rue Blaise Pascal, F-67000 Strasbourg, France.
E-mail: hosseini@unistra.fr
†CCDC 959987–959991. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt52850b
Synthesis
of
tectons
1. 1,2,4,5-Tetramethylbenzene,
(S)-(+)-sec-butylamine (Fluka, lot no. 1245162, optical rotation:
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+8.5°, purity (GC) 99.2%) and bis(triphenylphosphine)palla-
Crystals of 1·Cu(hfac)2. Through a buffered layer of a 1 : 1
dium(II) dichloride were commercially available and were used C2H4Cl2–EtOH mixture (0.1 mL), the diffusion of an EtOH
without further purification.
solution (1 mL) of Cu(hfac)2 (5 mg) into a C2H4Cl2 solution
Compounds 2–421a,b,g and 4-ethynylpyridine22 were pre- (1 mL) of tecton 1 (3 mg) afforded bluish-green single crystals
pared according to reported procedures. Their characteriz- after two days.
ations were consistent with reported data.
Crystals of 1·Cu2(OAc)4. Diffusion of an EtOH solution
Synthesis of intermediate 5. To a suspension of dianhydride (1 mL) of Cu(OAc)2 (5 mg) into a CHCl3 solution (1 mL) of
4 (1 g, 2.66 mmol) in acetic acid (30 mL), (S)-(+)-2-amino- tecton 1 (3 mg) afforded bluish-green single crystals after five
butane (0.8 mL, 7.98 mmol, 3 eq.) was added via a syringe. The days.
reaction mixture was refluxed overnight before it was allowed
Crystals of 1·NiCl2. Through a buffered layer of a 1 : 1
to reach RT. The white precipitate was collected by filtration, C2H2Cl4–EtOH mixture (0.1 mL), diffusion of an EtOH solution
washed with H2O (50 mL) and dried under vacuum to yield (1 mL) of NiCl2 (5 mg) into a C2H2Cl4 solution (1 mL) of tecton
compound 5 as a white solid (1.16 g, 90% yield). 1H-NMR 1 (3 mg) afforded light-green single crystals after two days.
(300 MHz, CDCl3, 25 °C) δ (ppm): 4.31 (m, 2H), 2.04 (m, 2H),
3
3
Single crystal analysis
1.82 (m, 2H), 1.48 (d, 6H, J = 7.0 Hz), 0.89 (t, 6H, J = 7.3 Hz);
13C-NMR (75 MHz, CDCl3, 25 °C): δ (ppm): 163.6, 135.8, 114.1, Data were collected on a Bruker APEX8 CCD diffractometer
50.5, 26.6, 18.2, 11.3; Elemental analysis: calc. for equipped with an Oxford Cryosystem liquid N2 device at 173(2) K
C18H18Br2N2O4: C 44.47%; H 3.73%; N 5.76%; found C using a molybdenum microfocus sealed tube generator with
44.48%; H 3.73%; N 5.68%; [α]4D0: +21.4° (c = 0.5 in CHCl3); mirror-monochromated Mo-Kα radiation (λ = 0.71073 Å), ope-
m.p. > 330 °C.
rated at 50 kV/600 mA. For both structures, diffraction data
Synthesis of tecton 1. A solution of compound 5 (500 mg, were corrected for absorption. Structures were solved using
1.03 mmol) along with 4-ethynylpyridine (318 mg, 3.09 mmol, SHELXS-97 and refined by full matrix least-squares on F2 using
3 eq.) in Et3N (30 mL) was degassed with argon for 15 min SHELXL-97. The hydrogen atoms were introduced at calculated
before cat. PdCl2(PPh3)2 (145 mg, 0.21 mmol, 0.2 eq.) and CuI positions and not refined (riding model).23
(40 mg, 0.21 mmol, 0.2 eq.) were added. The reaction mixture
Crystallographic data for 1. C32H26N4O4, M = 530.67, mono-
was heated to reflux for 48 h before it was allowed to reach RT. clinic, space group P21, a = 5.1611(17) Å, b = 21.520(7) Å, c =
The mixture was evaporated to dryness and the resulting solid 12.209(4) Å, α = 90°, β = 101.474(6)°, γ = 90°, V = 1328.9(7) Å3,
was washed with MeOH (30 mL). The crude product was T = 173(2) K, Z = 2, Dc = 1.326 Mg m−3, μ = 0.089 mm−1, 11 214
further purified by column chromatography on silica gel collected reflections, 6034 [R(int) = 0.0652], GooF = 1.024, R1 =
(eluent CH2Cl2, 1% MeOH and 2% MeOH) affording tecton 1 0.0791, wR2 = 0.1813 for I > 2σ(I) and R1 = 0.1445, wR2 = 0.2020
(430 mg, 79% yield) as a yellowish solid. 1H-NMR (300 MHz, for all data.
3
CDCl3, 25 °C) δ (ppm): 8.71 (d, 4H, J = 5.9 Hz), 7.65 (d, 4H,
Crystallographic data for 1·HgCl2. C32H26N4HgCl2, M =
3J = 5.9 Hz), 4.37 (m, 2H), 2.15 (m, 2H), 1.89 (m, 2H), 1.53 (d, 802.06, orthorhombic, space group P21212, a = 21.6201(6) Å, b =
6H, J = 6.8 Hz), 0.94 (t, 6H, J = 7.4 Hz); 13C-NMR (75 MHz, 29.5433(9) Å, c = 5.0964(2) Å, α = β = γ = 90°, 3255.22(19) Å3, T =
CDCl3, 25 °C): δ (ppm): 164.9, 150.4, 136.9, 130.2, 126.4, 114.9, 173(2) K, Z = 4, Dc = 1.637 Mg m−3, μ = 4.933 mm−1, 49 104
101.8, 84.8, 50.6, 27.1, 18.7, 11.8; Elemental analysis: calc. for collected reflections, 7416 [R(int) = 0.0653], GooF = 1.029, R1 =
C32H26N4O4 C 72.44%; H 4.94%; N 10.56%; found C 71.96%; 0.0514, wR2 = 0.1271 for I > 2σ(I) and R1 = 0.0732, wR2 = 0.1372
H 4.77%; N 10.34%; [α]2D0: +22.6° (c = 1.0 in CHCl3); m.p. for all data, Flack parameter = 0.037(13).
3
3
> 330 °C.
Crystallographic data for 1·Cu(hfac)2. C32H26N4O4Cu·
2C5HF6O2·2C2H4Cl2, M = 1206.13, triclinic, space group P1, a =
6.4908(2) Å, b = 14.5434(5) Å, c = 15.0317(5) Å, α = 66.668(2)°,
Preparation of crystalline materials
Crystals of tecton 1. Vapour diffusion at 25 °C of pentane β = 82.427(2)°, γ = 80.980(2)°, V = 1283.01(7) Å3, T = 173(2) K,
contained in an external glass vial into a glass vial (height = Z = 1, Dc = 1.561 Mg m−3, μ = 0.733 mm−1, 36 928 collected
4.5 cm, diameter = 1.5 cm) containing tecton 1 (10 mg) in reflections, 12 000 [R(int) = 0.0368], GooF = 1.058, R1 = 0.0490,
CHCl3 (2 mL) produced colourless needle-like single crystals wR2 = 0.1359 for I > 2σ(I) and R1 = 0.0645, wR2 = 0.1509 for all
after two days.
data, Flack parameter = 0.018(10).
Crystallographic data for 1·Cu2(OAc)4. C32H26N4O4Cu2·
4C2H3O2·2CHCl3, M = 1371.30, triclinic, space group P1, a =
Crystals of coordination polymers
General. Crystallizations were carried out by liquid–liquid 8.2342(5) Å, b = 19.7423(10) Å, c = 19.9269(12) Å, α = 65.3440(10)°,
diffusion techniques in glass crystallization tubes (height = β = 89.542(2)°, γ = 86.931(2)°, V = 2939.4(3) Å3, T = 173(2) K,
15 cm, diameter = 0.4 cm) at ca. 25 °C.
Z = 2, Dc = 1.549 Mg m−3, μ = 1.327 mm−1, 26 531 collected
Crystals of 1·HgCl2. Through a buffered layer of a 1 : 1 reflections, 24 176 [R(int) = 0.0216], GooF = 1.031, R1 = 0.0632,
CHCl3–EtOH mixture (0.1 mL), the diffusion of an EtOH solu- wR2 = 0.1394 for I > 2σ(I) R1 = 0.1160, wR2 = 0.1626 for all data,
tion (1 mL) of HgCl2 (5 mg) into a CHCl3 solution (1 mL) of Flack parameter = 0.029(14).
tecton 1 (3 mg) afforded colourless single crystals after three
Crystallographic
data
for
1·NiCl2. C64H52N8O8NiCl2·
days.
3C2H2Cl4·2H2O, M = 1730.29, monoclinic, space group C2, a =
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24.5378(9) Å, b = 24.9529(11) Å, c = 19.2940(7) Å, α = γ = 90°,
β = 121.6010(10)°, V = 10 061.8(7) Å3, T = 173(2) K, Z = 4, Dc =
1.142 Mg m−3, μ = 0.612 mm−1, 26 843 collected reflections,
26 843 [R(int) = 0.0458], GooF = 0.997, R1 = 0.0957, wR2
=
0.2411 for I > 2σ(I) R1 = 0.1472, wR2 = 0.2605 for all data, Flack
parameter = 0.07(2).
Results and discussion
Design of the enantiomerically pure tecton 1
Tecton 1 is a C2 chiral unit based on a diimide backbone
derived from pyromellitic acid. Analogous diimide based
derivatives have been used as monomers for the formation of
covalent π-donor–acceptor polymers.21a–f As coordinating sites,
two pyridyl groups are used. The connection between the back-
bone and pyridyl units is achieved through an ethynyl spacer
using the para position of the aromatic ring. The chirality is
introduced through both imide moieties using an alkyl frag-
ment bearing an enantiomerically pure chiral centre of the
S configuration. Compound 1 should behave as a rigid bis-
monodentate chiral tecton in the presence of metal cations
displaying at least two free coordination sites.
Fig. 1 X-Ray structure of tecton 1 (a) and views of the stacking of two
consecutive molecules (b). H atoms are omitted for clarity. For bond dis-
tances and angles see text.
ca. 2.46 Å. The length of the tecton i.e. the distance between
the two N atoms of the pyridyl units is 16.47 Å. It is worth
noting that in the crystalline phase, the two ethyl groups and
thus the two methyl groups of the two chiral centres are syn
oriented. Consecutive molecules are stacked in a parallel and
staggered fashion. However, in consecutive stacks, the C–C
triple bonds of the ethynyl moieties are located above and
below the phenyl group of the pyromellitic backbone with dis-
tances in the 3.46–4.23 Å range (Fig. 1b).
Synthesis of the enantiomerically pure C2-chiral tecton 1
The synthetic strategy followed is based on the use of com-
pound 4 which allows, through sequential transformations,
the introduction of both chiral centres using the two anhy-
dride moieties and the two coordinating sites using the two
bromine atoms.
Choice of metallatectons
The starting material for the synthesis of tecton
1
The chiral and enantiomerically pure compound 1 is a neutral
tecton. Thus, its combination with metal cations may be either
achieved using metal cations associated with non-coordinating
anions or with neutral metal complexes for which anions are
coordinated to the metal centre. Whereas for the first possi-
bility, owing to the charge neutrality requirement, the anion
must necessarily be present in the crystal, for the second case,
one may take advantage of the binding of the anion by the
metal centre to design neutral metal complexes as metalla-
tectons. Indeed, for example for a metal cation such as Hg(II)
adopting usually a tetrahedral coordination geometry (Fig. 2a),
(Scheme 1) was the commercially available durene (1,2,4,5-
tetramethyl benzene). The latter was transformed into the
dibromo compound 2 by a double bromination process.21a
Using an excess of KMnO4, all four methyl groups of 2 were
fully oxidized affording thus the tetracarboxylic derivative 3 in
38% yield.21a,b Upon refluxing the latter in a mixture of acetic
acid and acetic anhydride, the bisanhydride derivative 4 was
obtained in 68% yield.21a,b,g The condensation between com-
pound 4 and (S)-(+)-2-aminobutane in acetic acid at 90 °C
afforded the chiral compound 5 in 90% yield. Finally, the coor-
dinating sites, i.e. 4-ethynyl-pyridines, were introduced by a
Pd(PPh3)2Cl2 catalysed Sonogashira coupling reaction at 90 °C
between 5 and 4-ethynyl-pyridine in Et3N along with a catalytic
amount of CuI. The desired enantiomerically pure tecton 1
was obtained in 79% yield (see the Experimental section).
In addition to classical characterizations in solution, the
structure of the enantiomerically pure tecton 1 was established
in the solid state by X-ray diffraction on single crystal (see the
Experimental section). Upon vapour diffusion of pentane into
a solution of 1 in CHCl3, needle-like single crystals were
obtained. As expected, tecton 1 crystallises in a chiral space
group (P21). No solvent molecules are present in the lattice.
The pyridyl units are tilted with respect to the centre pyromel-
litic core by ca. 17.1 and 3.5° (Fig. 1a). The shortest distance
Fig. 2 Schematic representations of tetrahedral (a), dimeric complexes
(b), and octahedral metal complexes (c and d) for which some of the
coordination sites are blocked by coordinating anions (red spheres)
leading to a V-shaped (e) and a linear 2-connecting node (f and g) and a
between atoms belonging to two consecutive tectons 1 is 4-connecting node (h). The blue spheres represent free coordination sites.
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one may use two coordinating monodentate anions such as
chloride anions to block two coordination sites out of the four
possible ones and thus generate a neutral metallatecton
offering two free coordination sites as a V-shaped 2-connecting
node (Fig. 2e). In a similar fashion, if not considering the
M–M interaction, one may combine a pentacoordinated metal
centre such as Cu(II) with four bridging anions such as the
acetate anion (AcO−) and thus generate a dimeric species of
the paddlewheel type (Fig. 2b) behaving as a linear 2-connect-
ing node (Fig. 2f). Another possibility for the formation of a
linear 2-connecting node (Fig. 2g) is the use of a metal centre
in the oxidation state 2 adopting an octahedral coordination
geometry (Fig. 2c), for example Cu(II), and block four out of the
six coordination sites by two monoanionic chelating ligands
such as hexafluoroacetylacetonate (hfac−). Finally, one may
form a 4-connecting node (Fig. 2h) by blocking the two apical
coordination sites on a metal centre such as Ni(II) adopting an
octahedral coordination geometry by two monodentate coordi-
nating anions such as chloride anions (Cl−) (Fig. 2d).
Fig. 4 Comparison of the simulated (a) and recorded (b) PXRD patterns
for 1·HgCl2.
1D chain, each Hg2+ cation, adopting a distorted Td geometry
(N–Hg–N and Cl–Hg–Cl angles of 94.48° and 157.04° respect-
ively), is surrounded by two Cl− anions (Cl–Hg distance of
ca. 2.45 Å) and two N atoms (N–Hg distance of ca. 2.45 Å)
belonging to the pyridyl moieties of two consecutive tectons 1
(Fig. 3a). Within the 1D network consecutive cations are
distant by 21.45 Å.
Generation of enantiomerically pure coordination networks
Along the c axis (Fig. 3b), the close staggered packing of
consecutive 1D networks in a parallel fashion leads to a 3.28 Å
distance between the nearly flat pyromellitic cores of consecu-
tive layers. As for the free tecton 1, the two ethyl groups of the
two chiral centres are syn oriented.
The purity of crystals of 1·HgCl2 was established by PXRD
on microcrystalline powder, which revealed good match
between the simulated (Fig. 4a) and observed patterns
(Fig. 4b).
Copper 1D chiral coordination networks. As expected, com-
binations of tecton 1 with two different Cu(II) complexes
(Cu(hfac)2 and Cu(AcO)2) behaving as 2-connected linear
nodes generate again two homochiral 1D linear coordination
networks.
Mercury 1D chiral coordination networks. Upon slow
diffusion of an EtOH solution of HgCl2 into a CHCl3 solution
of the organic tecton 1 through a buffered layer (EtOH–CHCl3),
colourless crystals were obtained after one week. The X-ray
diffraction on single crystal investigation revealed that the
crystal (chiral space group P21212) is exclusively composed of
tecton 1 and HgCl2. The latter behaves as a 2-connecting
V-shaped node leading thus to the formation of a 1D stair type
mercury coordination network resulting from the bridging of
consecutive organic tectons 1 by HgCl2 complexes. Owing to
the enantiomerically pure nature of tecton 1, the 1D network
is chiral (Fig. 3). For the organic tecton, pyridyl units are tilted
with respect to the backbone by ca. 7.9 and 7.3°. Within the
Upon slow diffusion of an EtOH solution of Cu(hfac)2 into a
C2H4Cl2 solution of tecton 1 through a buffered layer com-
posed of a C2H4Cl2–EtOH mixture (see the Experimental part),
bluish-green crystalline materials were obtained after ca. one
week. The X-ray diffraction study on single crystal revealed the
formation of a neutral 1D linear chiral coordination polymer
(Fig. 5a) resulting from the bridging of consecutive tectons 1
by Cu(hfac)2 complexes. The crystal (chiral space group P1) is
composed of tecton 1, Cu2+ cations, hfac− anions and C2H4Cl2
solvent molecules. For the organic linker 1, the pyridyl units
are tilted with respect to the backbone by ca. 27.0 and 23.6°.
The Cu(II) centre, in a distorted octahedral coordination geo-
metry, is surrounded by four O atoms belonging to two hfac−
anions occupying the apices of the square base of the octa-
hedron (Cu–O distance in the 1.9–2.3 Å range) and two N
atoms belonging to the pyridyl moiety of two consecutive
tectons 1 occupying the two apical positions (N–Cu distances
of ca. 2.0 Å and N–Cu–N angles of ca. 180.0°). Within the 1D
network, consecutive Cu2+ cations are distant by 20.62 Å.
Consecutive 1D chains are packed in a staggered fashion
(Fig. 5b) forming layers of stacked 1D coordination polymers.
However in contrast with 1·HgCl2, no π–π interactions are
Fig. 3 Portion of the X-ray structure 1·HgCl2 showing the formation of
the 1D stair type coordination network (a) and the packing of consecu-
tive networks along the a axis (b). H atoms are not represented for
clarity. For bond distances and angles see text.
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molecules. For the two crystallographically independent
organic tectons 1, the pyridyl units are tilted with respect to
the backbone by ca. 6.9 and 19.3° and 10.3 and 8.7°. The Cu(II)
centres, adopting a square based pyramidal coordination geo-
metry, form
a neutral dimer of the paddlewheel type
(Cu2(AcO)4). Each metal centre is surrounded by four O atoms
belonging to four bridging acetate anions (O–Cu distance in
the 1.95–1.99 Å range) and one N atom belonging to the
pyridyl moiety of tecton 1 (N–Cu distance in the 2.14–2.19 Å
range). Within the 1D network, two paddlewheel motifs are
distant by ca. 20.7 Å.
As for 1·Cu(hfac)2 discussed above, the 1D chains are
packed in a staggered and parallel fashion (Fig. 6b). The
CHCl3 molecules are intercalated between consecutives chains
without any specific interaction with the 1D networks.
Unfortunately, again owing to the presence of volatile
CHCl3 solvent molecules in the crystal, the removal of the
mother liquor leads to the loss of the latter. Consequently,
although the material remains crystalline, no good match
between the simulated and observed powder diffraction
patterns is obtained.
Fig. 5 Portion of the X-ray structure of 1·Cu(hfac)2 showing the for-
mation of the 1D neutral and chiral linear coordination network resulting
from bridging of consecutive tectons 1 by Cu(hfac)2 behaving as a
neutral 2-connecting linear node (a) and packing of consecutive chains
along the b axis (b). H atoms and C2H4Cl2 solvent molecules are not pre-
sented for clarity. For bond distances and angles see text.
Nickel 2D chiral coordination networks. In order to gene-
rate a 2D chiral coordination network, tecton 1 was combined
with NiCl2 (see the Experimental section). The crystallisation
process afforded light green crystals, which were analysed by
X-ray diffraction on single crystal. The structural investigation
revealed the formation of a 2D enantiomerically pure co-
ordination network. The crystal (chiral space group C2) is
composed of the organic tecton 1, Ni2+ cations, Cl− anions and
highly disordered solvents molecules. Thus, the squeeze
command24 had to be applied to solve the structure.
The formation of the 2D grid-type neutral and chiral
architecture results from the interconnection of four different
tectons 1 by NiCl2 complexes behaving as 4-connected nodes
Fig. 6 Portions of the X-ray structure of 1·Cu2(AcO)4 showing a view
along the a axis of the 1D linear and chiral coordination network formed
upon combining the organic chiral tecton 1 and Cu2(AcO)4 as a linear 2-
connecting node (a) and the packing of consecutive chains viewed (Fig. 7a). Within the 2D network, the two pyridyl moieties of
along the c axis (b). H atoms and CHCl3 solvent molecules are not pre-
sented for clarity. For bond distances and angles see text.
tecton 1 are tilted with respect to the backbone by ca. 13.6 and
85.8°. The Ni(II) centre, adopting a distorted octahedral geome-
try, is linked to four organic tectons occupying the apices of
the square base of the octahedron through N–Ni bonds
observed, mainly due to the more crowded hfac anions. The
C2H4Cl2 solvent molecules occupy the interstices without any
specific interaction with the organic and metalloorganic
components.
Unfortunately, owing to the presence of solvent molecules
in the crystal lattice, the removal of the mother liquor leads to
the loss of C2H4Cl2 molecules. Although the material remains
crystalline, no good match between the simulated and
observed powder diffraction patterns is obtained.
Upon slow diffusion of an EtOH solution of Cu(OAc)2 into a
CHCl3 solution of 1, blue crystals were obtained after ca. one
week. X-Ray diffraction on single crystal revealed again the
Fig. 7 Portions of the X-ray structure of 1·NiCl2 along the a axis
showing the neutral 2D chiral grid resulting from the interconnection of
tectons 1 by NiCl2 neutral complexes acting as 4-connected nodes (a)
and the staggered packing of two consecutive grids (b). H atoms and
solvent molecules are not presented for clarity. For bond distances and
angles see text.
formation of a 1D homochiral linear coordination network
resulting from bridging of consecutive tectons 1 by Cu2(AcO)4
dimers behaving as 2-connecting linear nodes (Fig. 6a).
The crystal (chiral space group P1) is composed of the organic
tecton 1, Cu2+ cations, OAc− anions and CHCl3 solvent
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Fig. 9 Schematic representations of the C2-chiral linear tecton 1 bearing
two chiral centres (a), linear coordination networks obtained upon com-
bining 1 with Cu(hfac)2 or Cu(OAc)2 behaving as 2-connecting nodes (b), a
stair type 1D network formed with HgCl2 behaving as a bent connector
(c) and a 2D network formed with NiCl2 acting as a 4-connecting square
planar node (d). * indicates the presence of the chiral centre.
Fig. 8 Portions of the X-ray structure of 1·NiCl2 showing the packing of
consecutive chiral 2D grid type networks leading to a porous chiral
crystal. H atoms and solvent molecules are not presented for clarity. For
bond distances and angles see text.
the use of tecton 1 for the generation of pillared 2- and 3-D
coordination networks is under study.
(distance in the 2.12–2.14 Å range). The two Cl− anions are
located on the apical positions with Cl–Ni distances in the
2.43–2.45 Å range. Within the 2D sheet, consecutive Ni2+
cations are distant by ca. 20.74 Å. Within the crystal, consecu-
tive 2D networks are packed in a staggered fashion along the
a axis (Fig. 7b). The distance between consecutive layers, with
respect to the planes formed by the Ni(II) centres, is ca. 6.08 Å.
The packing of consecutive 2D chiral networks, although in a
staggered manner, leads to the formation of porous crystals
with a solvent accessible void of 50.6% (Fig. 8).
Acknowledgements
We thank the University of Strasbourg, the Institut Universi-
taire de France, the International Centre for Frontier Research
in Chemistry (icFRC, scholarship to P.L.), the C.N.R.S. and the
Ministère de l’Enseignement Supérieur et de la Recherche for
financial support.
Once again, owing to the presence of solvent molecules in
the lattice, the removal of crystals from the mother liquor
leads to the loss of solvent molecules. Again, although the
material remains crystalline, no good match between the simu-
lated and observed powder diffraction patterns is obtained.
Notes and references
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Compound 1 is an enantiomerically pure neutral and rigid
organic linear tecton bearing two divergently oriented mono-
dentate coordinating sites appended with two chiral centres of
the same (S) configuration. The latter are located orthogonal to
the pyridyl coordinating sites. Combinations of the chiral and
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formed, for the 4-connecting node, a 2D chiral and neutral
coordination network is obtained (Fig. 9d).
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