Cobalt(ii) coordination polymers with 4′-substituted 4,2′:6′,4′′- and 3,2′:6′,3′′- terpyridines: Engineering a switch from planar to undulating chains and sheets

Article abstract of DOI:10.1039/c2ce06609b

Two new ligands 4′-(1H-imidazol-4-yl)-4,2′:6′, 4′′-terpyridine (3) and 4′-(4-dimethylaminophenyl)-3,2′: 6′,3′′-terpyridine (4) are described. Structure determination of 3·CHCl₃ reveals the assembly of hydrogen-bonded chains of molecules of 3; the preference for NH_imidazole...N_tpy over NH_imidazole...N_imidazole hydrogen bonds is consistent with the relative basicities of the heterocyclic rings. Reactions of Co(NCS)₂ with 4′-phenyl-4,2′:6′,4′′- terpyridine (1), 4′-(4-ethynylphenyl)-4,2′:6′,4′′- terpyridine (2) or 3, produce two-dimensional networks. In each, the Co ²⁺ ion is in an octahedral trans-{Co(N_tpy) ₄(NCS)₂} environment. [{2Co(1)₂(NCS) ₂·5H₂O}_n] and [{Co(3) ₂(SCN)₂·2MeOH}_n] exhibit (4,4) nets. In [{Co(2)₂(NCS)₂·0.67C₂H ₄Cl₂·MeOH·H₂O}_n], a (6,3) net is present. In all three coordination networks, there is substantial twisting of the 4,2′:6′,4′′-terpyridine backbone and as a consequence, the dominant packing interactions are not the face-to-face π-stacking of tpy domains that are ubiquitous in many solid-state structures containing metal-bound tpy domains. As a preliminary investigation of the effects of altering the directionality of the donor set in the terpyridine domain, Co(SCN)₂ was reacted with ligand 4, and the one-dimensional coordination polymer [{Co(4)(MeOH)₂(NCS)₂}_n] was isolated. Ligand 4 adopts a trans,trans-arrangement and the zig-zag chains are undulating. The buckled sheets that result from the intermeshing of the chains contrast with the planar sheets observed in [{Cd(5)(OH₂) ₂(ONO₂)(O₂NO)·H₂O} _n] (5 = 4′-(4-dimethylaminophenyl)-4,2′:6′, 4′′-terpyridine). The observed packing interactions suggest that the change from planar to undulating chains and sheets on going from 5 to 4 is a consequence of optimizing face-to-face π-stacking interactions.

Full text of DOI:10.1039/c2ce06609b

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PAPER
Cobalt(II) coordination polymers with 40-substituted 4,20:60,400- and
3,20:60,300-terpyridines: engineering a switch from planar to undulating chains
and sheets†
*
*
Edwin C. Constable, Catherine E. Housecroft, Markus Neuburger, Srboljub Vujovic, Jennifer A. Zampese
and Guoqi Zhang
Received 30th November 2011, Accepted 23rd February 2012
DOI: 10.1039/c2ce06609b
Two new ligands 40-(1H-imidazol-4-yl)-4,20:60,400-terpyridine (3) and 40-(4-dimethylaminophenyl)-
3,20:60,300-terpyridine (4) are described. Structure determination of 3$CHCl3 reveals the assembly of
hydrogen-bonded chains of molecules of 3; the preference for NHimidazole/Ntpy over NHimidazole
/
imidazole hydrogen bonds is consistent with the relative basicities of the heterocyclic rings. Reactions of
N
Co(NCS)2 with 40-phenyl-4,20:60,400-terpyridine (1), 40-(4-ethynylphenyl)-4,20:60,400-terpyridine (2) or 3,
produce two-dimensional networks. In each, the Co2+ ion is in an octahedral trans-{Co(Ntpy)4(NCS)2}
environment. [{2Co(1)2(NCS)2$5H2O}n] and [{Co(3)2(SCN)2$2MeOH}n] exhibit (4,4) nets. In
[{Co(2)2(NCS)2$0.67C2H4Cl2$MeOH$H2O}n], a (6,3) net is present. In all three coordination
networks, there is substantial twisting of the 4,20:60,400-terpyridine backbone and as a consequence, the
dominant packing interactions are not the face-to-face p-stacking of tpy domains that are ubiquitous in
many solid-state structures containing metal-bound tpy domains. As a preliminary investigation of the
effects of altering the directionality of the donor set in the terpyridine domain, Co(SCN)2 was reacted
with ligand 4, and the one-dimensional coordination polymer [{Co(4)(MeOH)2(NCS)2}n] was isolated.
Ligand 4 adopts a trans,trans-arrangement and the zig-zag chains are undulating. The buckled sheets
that result from the intermeshing of the chains contrast with the planar sheets observed in
[{Cd(5)(OH2)2(ONO2)(O2NO)$H2O}n] (5 ¼ 40-(4-dimethylaminophenyl)-4,20:60,400-terpyridine). The
observed packing interactions suggest that the change from planar to undulating chains and sheets on
going from 5 to 4 is a consequence of optimizing face-to-face p-stacking interactions.
However, the variation in zinc(II)/40-substituted 4,20:60,400-ter-
Introduction
pyridine structural motifs (metallohexacycles, polycatenated
metallocapsules or one-dimensional chains) that can spontane-
ously arise illustrates that we are far from understanding the
assembly process, and as a consequence, controlling it.15
Subtleties of crystallization conditions apart, the structural
diversity in complexes of terpyridines depends upon the N,N0,N00-
substitution pattern in the tpy ligand (48 possible isomers) and
the coordination geometry at the metal ion. In this paper, we
focus on an octahedral cobalt(II) centre which functions as
a linear node for network assembly. We describe the reactions of
Co(SCN)2 with three 40-substituted 4,20:60,400-tpy ligands (1–3,
Scheme 1) and one 40-substituted 3,20:60,300-terpyridine
(3,20:60,300-tpy) ligand 4 (Scheme 1). Both peripheral N,N0-donor
sets are divergent, and both could subtend a 120ꢀ angle (Scheme
2). However, whereas rotations about the inter-ring C–C bonds
in 4,20:60,400-tpy have no effect on the directionalities of the
peripheral N-donors, rotations about the corresponding C–C
bonds in 3,20:60,300-tpy lead to different ligand conformations,
three of which are shown in Scheme 2. The coordination chem-
istry of 3,20:60,300-tpy and its derivatives is little explored. Granifo
The divergent 4,20:60,400-terpyridine (4,20:60,400-tpy) ligand is
becoming popular as a building block for the assembly of
coordination polymers and networks.1–16 The ease with which the
li0gand synthesis can be adapted to introduce substituents at the
4 -position using Krohnke, one-pot or cascade strategies18
17
€
allows facile engineering of the properties of the ligand and its
complexes. Only the terminal pyridine rings of the tpy domain
are involved in metal-binding (Scheme 1), and materials con-
taining coordinated 4,20:60,400-terpyridines have application as
sensors for protons6,7 and other Lewis acids. To date, zinc(II) has
been commonly chosen as a node, either as a bent {ZnN2X2}
node (e.g. X ¼ OAc, Cl, I)1–4,7,11 or a linear {Zn2N2(m-OAc)4}
node.6,7 Both these are topologically the same. The reported
examples indicate that one-dimensional polymers are favoured.
Department of Chemistry, University of Basel, Spitalstrassse 51, CH-4056
Basel, Switzerland. E-mail: catherine.housecroft@unibas.ch; edwin.
constable@unibas.ch; Fax: +41 61 267 1018; Tel: +41 61 267 1008
† CCDC reference numbers 856244–856248. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c2ce06609b
3554 | CrystEngComm, 2012, 14, 3554–3563
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and coworkers have reported that 40-phenyl-3,20:60,300-tpy, 5,
reacts with Zn(OAc)2 to yield the discrete, dinuclear complex
[(AcO-O,O0)2Zn(m-5)Zn(AcO-O,O0)2]$H2O in which the water
molecule is hydrogen-bonded between the two {Zn(AcO-O,O0)2}
domains.19 To the best of our knowledge, only three coordina-
tion polymers based on 3,20:60,300-tpy metal-binding domains
have been structurally characterized20,21 and all contain 40-(4-
pyridyl)-3,20:60,300-tpy in which the central N-donor of the tpy
unit remains uncoordinated.22,23
Experimental
1H and 13C NMR spectra were recorded on a DRX-500 NMR
spectrometer (chemical shifts referenced to residual solvent peaks,
TMS ¼ d 0 ppm). Infrared spectra of solid samples wererecorded on
a Shimadzu FTIR-8400S spectrophotometer with a Golden Gate
diamondATR accessory. Electrospray ionizationmassspectra were
recorded on a Bruker esquire 3000plus mass spectrometers.
Ligands 1 and 2 were prepared as previously reported.1,8
Ligand 3
4-Acetylpyridine (2.42 g, 20.0 mmol) was added to a solution of
1H-imidazole-4-carbaldehyde (0.960 g, 10.0 mmol) in EtOH
Scheme 2 Divergent binding mode of 4,20:60,400-tpy, compared to
possible binding modes of 3,20:60,300-tpy.
(40 cm3). KOH pellets (1.12 g, 20 mmol) were added, followed by
aqueous NH3 (32%, 40 cm3). The resulting orange solution was
stirred at room temperature for 16 h, after which time, aqueous
NaHCO3 was added. The suspension was stirred for 10 min and
then filtered. The product was washed with H2O and EtOH and
dried in vacuo over P2O5. Compound 3 was isolated as a white
solid (1.20 g, 40.1%). m.p. > 300 ꢀC. 1H NMR (500 MHz, CDCl3/
CD3OD) d (ppm)) 8.50 (d, J ¼ 5.2 Hz, 4H, HA2), 8.11 (s, 2H,
HB3), 7.99 (d, J ¼ 5.2 Hz, 4H, HA3), 7.61 (s, 1H, HC2), 7.57 (s, 1H,
HC5); 13C NMR (126 MHz, CDCl3/CD3OD) d (ppm) 154.5 (CA4),
149.5 (CB4), 149.3 (CA2), 146.9 (CA4), 136.8 (CC2/C4), 136.75
(CC2/C4), 121.4 (CA3), 116.5 (CB3), 115.4 (CC5). IR (solid, cmꢁ1) n
3087br, 2851br, 2675w, 1596s, 1558s, 1458s, 1424m, 1307w,
1175m, 1124w, 1084w, 1062m, 1004m, 959m, 921w, 897w, 826s,
785m, 739m, 668s, 655s, 633s. ESI-MS m/z 621.1 [2M + Na]+
(calc. 621.2), 322.1 [M + Na]+ (base peak, calc. 322.1), 300.2 [M +
H]+ (calc. 300.1). Found
C 71.36, H 4.56, N 22.90;
C18H13N5$0.2H2O requires C 71.37, H 4.46, N 23.12%.
Ligand 4
3-Acetylpyridine (1.45 g, 12.0 mmol) was added to a solution of
4-dimethylaminobenzaldehyde (0.89 g, 6.0 mmol) in EtOH (20
cm3). KOH pellets (0.67 g, 12 mmol) were added to the reaction
mixture, followed by aqueous NH3 (32%, 20 cm3). The resulting
orange solution was stirred at room temperature for 18 h, during
which time a yellow suspension formed. The solid was collected
by filtration, washed well with H2O and EtOH and dried in vacuo
over P2O5. Compound 4 was isolated as a yellow solid (1.25 g,
1
59.2%). m.p. 112–113 ꢀC. H NMR (500 MHz, CDCl3) d 9.34
Scheme 1 Structures of ligands 1–5 showing atom labelling for NMR
spectroscopic assignments.
(s, 2H, HA2), 8.66 (d, J ¼ 4.4 Hz, 2H, HA6), 8.47 (d, J ¼ 7.9 Hz,
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2H, HA4), 7.89 (s, 2H, HB3), 7.66 (dAB, J ¼ 8.7 Hz, 2H, HC2), 7.42
(m, 2H, HA5), 6.81 (dAB, J ¼ 8.8 Hz, 2H, HC3), 3.03 (s, 6H, HMe).
13C NMR (126 MHz, CDCl3) d (ppm) 155.3 (CB2), 151.5 (CC4),
150.7 (CB4), 150.2 (CA6), 148.6 (CA2), 135.3 (CA3), 134.7 (CA4),
128.0 (CC2), 125.1 (CC1), 123.8 (CA5), 116.6 (CB3), 112.7 (CC3), 40.5
(CMe). IR (solid, cmꢁ1) n 1598s, 1520s, 1447w, 1430w, 1417w,
1357m, 1233w, 1199m, 1172w, 1025m, 946w, 875w, 802s, 730s.
ESI-MS m/z 727.4 [2M + Na]+ (base peak, calc. 727.3), 375.2 [M
+ Na]+ (calc. 375.2), 353.2 [M + H+] (calc. 353.2). Found C 77.00,
H 5.79, N 15.37; C23H20N4$0.3H2O requires C 77.20, H 5.80, N
15.66%.
[{Co(4)(MeOH)2(NCS)2}n]
A solution of 4 (17.6 mg, 0.0500 mmol) in MeOH/1,2-Cl2C6H4
(10 cm3, 1: 4, v/v) was placed in a test tube, and a mixture of
MeOH and 1,2-Cl2C6H4 (5 cm3, 1: 1, v/v) was layered on top. A
final layer of a solution of Co(SCN)2 (8.75 mg, 0.050 mmol) in
MeOH (10 cm3) was added carefully. The tube was sealed and left
to stand at room temperature for a month, during which time
X-ray quality orange blocks formed on the glass walls. The
crystals were isolated by decanting the solvent and were washed
with MeOH, and dried in air. Yield: 23.0 mg (77.8%). IR (solid,
n, cmꢁ1) 3234br, 2087s, 1595s, 1576m, 1533s, 1481w, 1388m,
1361m, 1215w, 1193w, 1170w, 1055w, 1033w, 1014s, 950w, 885w,
809s, 702s. Found C 54.76, H 4.74, N 13.72; C27H28Co-
N6O2S2$0.33H2O requires C 54.27, H 4.83, N 14.06%.
[{2Co(1)2(NCS)2$5H2O}n]
A solution of 1 (15.5 mg, 0.0500 mmol) in MeOH/1,2-Cl2C6H4
(10 cm3, 1: 4, v/v) was placed in a test tube. A mixture of MeOH
and 1,2-Cl2C6H4 (5 cm3, 1: 1, v/v) was layered on the top of this
solution, followed by a solution of Co(SCN)2 (8.75 mg,
0.0500 mmol) in MeOH (10 cm3). The tube was sealed and
allowed to stand at room temperature for one month, during
which time X-ray quality orange blocks grew on the walls of the
tube. The crystals were collected by decanting the solvent and
were washed with MeOH and dried in air. Yield: 13.1 mg (62.5%
based on 1). IR (solid, n, cmꢁ1) 2058s, 1657m, 1598s, 1560s,
1540s, 1510m, 1398m, 1215w, 1063w, 1015w, 835s, 764s, 689s,
Crystallography
Data were collected on a Bruker-Nonius KappaAPEX diffrac-
tometer, with data reduction, solution and refinement using the
programs APEX,24 SIR9225 and CRYSTALS,26 or on a Stoe
IPDS diffractometer with data reduction, solution and refine-
ment using Stoe IPDS software27 and SHELXL97.28 Ortep
figures were drawn using Ortep-3 for Windows,29 and Mercury v.
2.3 and 2.430,31 were used to analyse the structures. See Table 1
for crystallographic data.
668s, 646s. Found
C
63.85,
H
4.23,
N
13.45;
C44H30CoN8S2$2.5H2O requires C 63.00, H 4.21, N 13.36%.
Results and discussion
[{Co(2)2(NCS)2$0.67C2H4Cl2$MeOH$H2O}n]
Ligand synthesis and characterization
A solution of 2 (33.3 mg, 0.100 mmol) in MeOH/1,2-Cl2C6H4
(10 cm3, 1: 4, v/v) was placed in a test tube, and a mixture of
MeOH and 1,2-C2H4Cl2 (5 cm3, 1: 1, v/v) was layered on the top.
Finally, a solution of Co(SCN)2 (17.5 mg, 0.100 mmol) in MeOH
(10 cm3) was layered on the top of the second layer. The tube was
sealed and allowed to stand at room temperature for a month,
during which time X-ray quality pink blocks grew on the walls of
the tube. The product was isolated by decanting the solvent and
was washed with MeOH, and dried in air. Yield: 29.8 mg (62.3%
based on 2). IR (solid, n, cmꢁ1) 3278s, 3215w, 2066s, 1598s,
1570m, 1539s, 1510m, 1397m, 1215m, 1064m, 1014s, 853w, 825s,
Ligands 3 and 4 were prepared in moderate yields by treatment
of 4-acetylpyridine with 1H-imidazole-4-carbaldehyde or 3-ace-
tylpyridine with 4-dimethylaminobenzaldehyde in the presence
of KOH followed by addition of aqueous NH3. The electrospray
mass spectrum of each compound exhibited peaks corresponding
to [2M + Na]+, [M + Na]+ and [M + H]+. Solution (CDCl3) H
1
and 13C NMR spectra were fully assigned with the aid of COSY,
NOESY, DEPT, HMBC and HMQC techniques, and were
consistent with a symmetrical tpy domain. AB-Pattern doublets
at d 8.55 and 7.99 ppm for protons HA2 and HA3 in 3 (Scheme 1)
are replaced by signals at d 9.34, 8.66, 8.47 and 7.42 pm for HA2
,
673s, 649s, 638s. Found
C 63.81, H 3.89, N 12.07;
HA6, HA4 and HA5 in 4. The change from the 40-imidazolyl to 40-
C48H30CoN8S2$0.67C2H4Cl2$MeOH$H2O requires C 63.10, H
4.07, N 11.69%.
(4-N,N-dimethylamino)phenyl substituent results in a shift in the
singlet for HB3 from d 8.11 ppm in 3 to d 7.89 ppm in 4. In the 13
C
NMR spectrum of 3, the signal for CC5 was poorly resolved and
a chemical shift of d 115.4 ppm was confirmed from a crosspeak
in the HMQC spectrum.
[{Co(3)2(NCS)2$2MeOH}n]
A solution of 3 (29.9 mg, 0.100 mmol) in MeOH/1,2-Cl2C6H4
(10 cm3, 1: 4, v/v) was placed in a test tube, and a mixture of
MeOH and 1,2-Cl2C6H4 (5 cm3, 1: 1, v/v) was layered over the
first solution, followed by a layer of a solution of Co(SCN)2
(35.0 mg, 0.200 mmol) in MeOH (10 cm3). The tube was sealed
and left to stand at room temperature for a month. During this
period, X-ray quality brown needles formed on the walls of the
tube. Crystals were collected by decanting the solvent, were
washed with MeOH, and dried in air. Yield: 31.2 mg (74.5%
based on 3). IR (solid, n, cmꢁ1) 2070s, 1657s, 1604s, 1560m,
1510m, 1458m, 1214w, 1014m, 836s, 668s, 642m. Found C 54.07,
H 4.07, N 19.22; C38H26CoN12S2$MeOH$3H2O requires C
54.48, H 4.22, N 19.55% (see text).
Crystals of 3$CHCl3 were grown from a chloroform/methanol
solution of the compound by slow evaporation. The molecular
structure of 3 is illustrated in Fig. 1a, with selected bond
distances and angles listed in the caption. Three of the rings in the
ligand are essentially coplanar, while the pyridine ring containing
N1 exhibits a greater deviation from the plane; the angles
between the least squares planes of the rings containing N1/N2,
N2/N3 and N2/N4 are 17.42(8), 6.93(8) and 5.34(9)ꢀ. The
twisting of the N1-containing ring is associated with the crystal
packing: chloroform molecules reside in pockets between pairs of
the N1-containing pyridine units of adjacent ligands (Fig. 1b).
The relative basicities of the pyridine and imidazole moieties in 3
3556 | CrystEngComm, 2012, 14, 3554–3563
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Table 1 Crystallographic data for 3$CHCl3, [{2Co(1)2(NCS)2$5H2O}n], [{Co(2)2(NCS)2$0.67C2H4Cl2$MeOH$H2O}n], [{Co(3)2(NCS)2$2MeOH}n]
and [{Co(4)(MeOH)2(NCS)2}n]
[{2Co(1)2(NCS)2$
5H2O}n]
[{Co(2)2(NCS)2$0.67C2H4Cl2$
MeOH$H2O}n]
[{Co(3)2(NCS)2$
2MeOH}n]
[{Co(4)(MeOH)2
(NCS)2}n]
Compound
3$CHCl3
Formula
C18H13N5$CHCl3
418.70
colourless block
Monoclinic
P21/c
7.0576(8)
21.727(3)
12.0929(12)
103.978(8)
1799.5(4)
1.546
C88H70Co2N16O5S4
1677.72
orange block
Monoclinic
C2/c
24.608(2)
10.6168(10)
17.7748(16)
116.118(6)
4169.7(6)
1.328
C50.33H38.67Cl1.33CoN8O2S2
957.90
pink block
Monoclinic
C2/c
28.199(6)
10.371(2)
32.295(7)
103.51(3)
9184(3)
1.383
8
0.593
C40H34CoN12O2S2
837.85
brown needle
Monoclinic
P21/c
23.3334(7)
10.3868(3)
17.3827(6)
109.477(2)
3971.8(2)
1.401
C27H28CoN6O2S2
591.62
orange block
Orthorhombic
Pbca
14.3014(8)
14.3112(7)
26.2091(12)
90
5364.2(5)
1.465
Formula weight
Crystal colour and habit
Crystal system
Space group
ꢀ
a, b, c/A
b (ꢀ)
3
ꢀ
U/A
Dc/Mg mꢁ3
Z
4
0.524
173
29140
2
0.560
173
45214
4
0.590
123
102487
8
0.833
173
139949
m(Mo-Ka)/mmꢁ1
T/K
Refln. collected
173
81174
Unique refln. (Rint
)
4014 (0. 0611)
3531
244
I > 2s(I)
0.0368 (0.0437)
0.0894 (0.0931)
1.054
3715 (0. 0647)
3582
274
I > 2s(I)
0.0581 (0.0597)
0.1598 (0.1612)
1.119
10540 (0.0426)
9902
615
I > 2s(I)
0.0463 (0.0487)
0.1244 (0.1264)
1.043
17451 (0.056)
12290
678
I > 2s(I)
0.0697 (0.1092)
0.0669 (0.1443)
1.0536
6116 (0.0591)
5980
353
I > 2s(I)
0.0415 (0.0425)
0.0928 (0.0933)
1.216
Refln. for refinement
Parameters
Threshold
R1 (R1 all data)
wR2 (wR2 all data)
Goodness of fit
can be estimated from values of pKb of 4-phenylpyridine (8.56)
and of 4-phenylimidazole (7.90).32 From the difference in pKb
values, one predicts that NHimidazole/Npyridine hydrogen
bonding should be preferred over NHimidazole/Nimidazole
hydrogen bond formation. Indeed, this is observed in the solid
state structure of 4-(5-(4-fluorophenyl)-1H-imidazol-4-yl)pyri-
dine.33 The pKa of 4-phenylimidiazole is 13.42,32 suggesting that
complete transfer of H+ from the imidazole to pyridine domain
will not occur. The solid-state structure of 3 is consistent with
these predictions: chains of molecules assemble (Fig. 1b) sup-
ported by NHimidazole/N3pyridine hydrogen-bonds (Table 2). The
chains are connected into sheets through weak CH/N and
CH/Cl contacts (Table 2). The overall lattice consists of a layer
assembly and face-to-face p-stacking is a dominant contribution
to the packing interactions. Centrosymmetric pairs of tpy
domains engage in face-to-face p-stacking at a separation of
position a). The N–Co–N bond angles lie in the range 88.61(10)
to 91.39(10)ꢀ. Ligand 1 coordinates through atoms N1 and
N3, bridging Co1 and Co1i (symmetry code i ¼ ꢁ½ ꢁ x, ½ + y,
½ ꢁ z); atom N2 remains uncoordinated. Extension of the C–N
connectivities through symmetry related ligands leads to a two-
dimensional network consisting of interconnected [4 + 4] met-
allomacrocyclic motifs (Fig. 3). The (4,4) net mimics that
observed in [{Cd(1)2(ONO2)2$MeOH$CHCl3}n].5
The tpy unit of coordinated ligand 1 is highly twisted, with
angles of 26.72(19) and 13.83(17)ꢀ between the least squares
planes of the rings containing pairs of atoms N1/N2 and N2/N3.
This deformation gives rise to the undulating structural motifs
evident in Fig. 2b. The phenyl ring of ligand 1 is twisted
15.45(19)ꢀ out of the plane of the pyridine (py) ring to which it is
attached. Despite the non-planarity of the phenylpyridine unit,
centrosymmetric pairs of phenylpyridine domains in adjacent
sheets engage in face-to-face p-interactions, with the separation
ꢀ
3.5 A; the distance between the centroids of the pyridine rings
containing atoms N2 and N3iv (symmetry code iv ¼ ꢁx, 1 ꢁ y, 2
of planes between rings containing C16 and C16 being 3.15 A
3
ii
ꢀ
ꢁ z) is 3.9 A.
(symmetry code ii ¼ 3/2 ꢁ x, /2 ꢁ y, 1 ꢁ z), and the distance
34
ꢀ
between the centroids of rings containing C16 and N2ii being
3.94 A.34 Fig. 4 illustrates two such stacking interactions between
ꢀ
[{2Co(1)2(NCS)2$5H2O}n]
parts of three adjacent sheets. Since there is only one independent
ligand in the asymmetric unit, all phenylpyridine entities are
involved in stacking interactions and are responsible for locking
the two-dimensional coordination networks together in the
crystal lattice. One and a half water molecules are disordered
within a void in the asymmetric unit, and have been modelled as
half occupancy oxygen atoms over three positions (the H atoms
could not be located).
Given the extended p-system in 1, it is not surprising that face-to-
face p-interactions34–36 feature significantly in the solid state
packing of coordination polymers and networks of complexes
containing 1 or 40-(4-X-C6H4) (X ¼ Me, Et, C^CH, Br, SMe,
NMe2) derivatives.3–8 Reaction of 1 with Co(NCS)2 resulted in
the growth of crystals of [{2Co(1)2(NCS)2$5H2O}n], and
elemental analytical data were consistent with the crystal chosen
for X-ray diffraction being representative of the bulk sample.
Fig. 2a depicts the contents of the asymmetric unit to provide the
atom labelling scheme for [{2Co(1)2(NCS)2$5H2O}n]. Atom Co1
is in an octahedral CoN6-environment (Fig. 2b), being located on
the inversion centre (0, 1, ½) of space group C2/c (Wyckoff
[{Co(2)2(NCS)2$0.67C2H4Cl2$MeOH$H2O}n]
Slow diffusion of solutions of ligand 2 in MeOH/1,2-Cl2C6H4
and Co(SCN)2 in MeOH in a sealed tube at room temperature
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Fig. 2 (a) The asymmetric unit in [{2Co(1)2(NCS)2$5H2O}n] (ellipsoids
plotted at 30% probability level, and solvent molecules excluded).
Selected bond parameters: Co1–N1 ¼ 2.186(3), Co1–N100 ¼ 2.065(3),
ꢀ
N100–C100 ¼ 1.156(4), S100–C100 ¼ 1.624(4) A; C100-N100-Co1 ¼
160.4(2)ꢀ. (b) Octahedral coordination environment around atom Co1
(green).
Fig. 1 (a) Structure of 3 in 3$CHCl3 (ellipsoids plotted at 40% proba-
bility level). Selected bond parameters: N1–C1 ¼ 1.326(2), N1–C5 ¼
1.331(2), N2–C10 ¼ 1.3346(19), N2–C6 ¼ 1.3392(19), N3–C15 ¼
1.329(2), N3–C11 ¼ 1.333(2) C16–C17 ¼ 1.364(2), C16–N4 ¼ 1.3764(19),
ꢀ
C17–N5 ¼ 1.357(2), C18–N4 ¼ 1.313(2), C18–N5 ¼ 1.340(2) A; C17-
C16-N4 ¼ 109.27(13), N5-C17-C16 ¼ 106.68(13), C18-N4-C16 ¼
104.82(13), C18-N5-C17 ¼ 106.60(13), N4-C18-N5 ¼ 112.62(14)ꢀ. (b)
Chains of hydrogen-bonded molecules of 3 and location of CHCl3
solvent molecules between N1-containing pyridine rings.
resulted in the growth of crystals of [{Co(2)2(N-
CS)2$0.67C2H4Cl2$MeOH$H2O}n]. Elemental analysis of the
bulk sample confirmed the same stoichiometry as that deter-
mined by X-ray diffraction using a single crystal selected from
the bulk material. The complex crystallizes in the monoclinic
space group C2/c, and Fig. 5a shows the asymmetric unit in order
to define the atom labelling. Each tpy unit coordinates through
the outer pyridine rings, leaving atoms N2 and N5 unbound. The
octahedral coordination sphere of Co1 is completed by bonds to
Fig. 3 Part of one sheet in [{2Co(1)2(NCS)2$5H2O}n] with one [4 + 4]
metallomacrocyclic building block depicted in red. Co atoms are shown
in ball representation.
2.1723(16), symmetry codes i ¼ 2 ꢁ x, 1 ꢁ y, 1 ꢁ z; ii ¼ 3/2 ꢁ x,
3
ꢁ½ + y, /2 ꢁ z), and the Co–N bond angles are in the range
87.58(7) to 93.21(7)ꢀ. Pairs of cobalt atoms (Co1 and Co1i) are
bridged by two ligands to produce [2 + 2] metallomacrocyclic
atoms N3i and N6ii (Co1–N3i ¼ 2.1695(16), Co1–N6ii
¼
Table 2 Intermolecular contacts in 3$CHCl3. The symmetry code refers to the atom with the asterisk
D–H/A/ꢀ
Symmetry code
ꢀ
ꢀ
D–H/A
H/A /A
D/A /A
N5H5B/N3*
C14H14A/N1*
C15H15A/Cl*
2.00
2.57
2.67
2.8473(19)
3.482(2)
3.5385(19)
162
160
152
ꢁ1 + x, y, ꢁ1 + z
ꢁx, ½ + y, 3/2 ꢁz
3
x, /2 ꢁ y, ½ + z
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Fig. 4 Face-to-face p-stacking of pairs of phenylpyridine units between
adjacent sheets in [{2Co(1)2(NCS)2$5H2O}n] (see text). Phenylpyridine
units are shown in space-filling representation.
Fig. 6 (a) Part of one sheet in the solid state structure of [{Co(2)2-
(NCS)2$0.67C2H4Cl2$MeOH$H2O}n] emphasizing the [6
+
6]
metallomacrocyclic building block (orange and red) with the two
component [2 + 2] macrocylic motifs in red. (b) The same unit as in
diagram (a), viewed approximately along the b-axis showing the
peripheral alkynylphenyl substituents.
4-HChCC6H4 substituents protrude above and below the sheet.
Alkyne unit C23H23 is directed towards a phenyl ring37 (Table 3)
in a non-adjacent sheet. In contrast, alkyne C46H46 is involved
in a CH/S contact (Table 3) with a thiocyanate ligand in an
adjacent sheet. There are additional CH/palkyne packing inter-
actions (Table 3).
It is noteworthy that both the independent 40-phenyltpy
domains in [{Co(2)2(NCS)2$0.67C2H4Cl2$MeOH$H2O}n] are
significantly twisted (Fig. 5a). The angles between the least
squares planes of the pairs of rings containing atoms N1/N2,
N2/N3, N2/C16, N4/N5, N5/N6 and N5/C39 are 34.20(9),
29.76(9), 14.29(9), 16.61(10), 40.87(10) and 20.90(10)ꢀ. Conse-
quently, embraces of the 40-phenyltpy domains which are often
a dominant feature of the crystal packing of compounds con-
taining these and related ligands,38,39 are not important in
[{Co(2)2(NCS)2$0.67C2H4Cl2$MeOH$H2O}n].
[{Co(3)2(SCN)2$2MeOH}n]
Fig.
5 (a) Asymmetric unit in [{Co(2)2(NCS)2$0.67C2H4-
As discussed earlier, one aim in appending an imidazole domain
is to explore the extent to which NHimidazole/Npyridine hydrogen
bonds contribute to the crystal packing of systems containing
this ligand. Crystals of [{Co(3)2(SCN)2$2MeOH}n] grew in
a tube containing three layers: a MeOH/1,2-Cl2C6H4 solution of
3, an intermediate layer of MeOH and 1,2-Cl2C6H4, and a final
layer consisting of a MeOH solution of Co(SCN)2. Multiple
elemental analyses of the bulk sample are consistent with this
being [{Co(3)2(SCN)2$MeOH$3H2O}n] rather than the crystal-
lographically determined [{Co(3)2(SCN)2$2MeOH}n].
Cl2$MeOH$H2O}n] (ellipsoids plotted at 40% probability level; solvent
molecules and H atoms except for ChCH excluded). Hashed lines used
to show the octahedral Co1 coordination geometry. Selected bond
parameters: Co1–N1
¼
2.1940(16), Co1–N4
¼
2.1723(16), Co1–
N50 ¼ 2.0712(18), Co1–N60 ¼ 2.0911(18), N50–C50 ¼ 1.151(3), C50–
ꢀ
S50 ¼ 1.635(2), N60–C60 ¼ 1.151(3), C60–S60 ¼ 1.631(2) A; C50-N50-
Co1 ¼ 165.19(18), C60-N60-Co1 ¼ 149.74(17)ꢀ. (b) A [2 + 2] metal-
lomacrocyclic motif (see text).
assembly motifs (Fig. 5b). Two such motifs (shown in red in
Fig. 6a) form opposite sides of a [6 + 6] metallomacrocycle, and
the latter are connected into a (6,3) net; (this net description
uses the cobalt ions as nodes). Viewing the two-dimensional net
along the crystallographic b-axis (Fig. 6b) reveals that the
Fig.
7
illustrates the asymmetric unit in [{Co(3)2-
(SCN)2$2MeOH}n] to define the atom numbering. Each of the two
independent ligands 3 binds to the cobalt(II) ions through the outer
pyridine rings, leaving pyridine atoms N4 and N9, and imidazole
donors N6 and N11 non-coordinated. The octahedral coordination
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Table 3 Intermolecular contacts in [{Co(2)2(NCS)2$0.67C2H4Cl2$
MeOH$H2O}n]. The symmetry code refers to the atom with the asterisk
[{Co(4)(MeOH)2(NCS)2}n]
Ligand 4 was selected for a preliminary investigation of complex
formation using Co(NCS)2 and a 3,20:60,300-tpy metal-binding
domain. We have previously described the assembly of a
one-dimensional coordination polymer [{Cd(5)(OH2)2(ONO2)-
(O2NO)$H2O}n] in which ligand 5 is 40-(4-dimethylamino-
phenyl)-4,20:60,400-terpyridine.8 This polymer contains approxi-
mately octahedral Cd(II) ions, with a trans-arrangement of
N-donors that produces linear nodes. Polymer chains assemble
into sheets with the NMe2 unit sitting snuggly into the V-shaped
cavity of the tpy unit of an adjacent chain. Sheets interact with
one another through efficient face-to-face p-stacking of Phtpy
domains.8
ꢀ
D–H/A
H/A /A
Symmetry code
3
C23H23/centroid of
ring with C19*
C46H46/ S60*
CH/palkyne
C43*H43*/C46
C43*H43*/C45
2.87
/
ꢁ x, ꢁ½ + y, ½ ꢁ z
2
2.69
x, ꢁy, ½ + z
2.87
3.19
2 ꢁ x, ꢁy, 2 ꢁ z
2 ꢁ x, ꢁy, 2 ꢁ z
environment of Co1 is completed by bonds to atoms N5i and N10ii
ꢀ
(2.1953(19) and 2.2228(10) A, respectively, symmetry codes i ¼
1 ꢁ x, ½ + y, ½ ꢁ z, ii ¼ x, ꢁ½ + y, ½ ꢁ z). The tpy domain of the
ligand containing atoms N8/N9/N10 is disordered, the outer rings
severely so. The disorder has been modelled over two positions of
occupancies 0.76 and 0.24; only the major occupancy sites are
shown in Fig. 7 and the discussion of the structure is restricted to
this ligand orientation. Each of the two independent ligands is
highly twisted, just as is observed in the two coordination networks
described above. The angles between the least squares planes of the
pyridine rings including atoms N3/N4, N4/N5, N8/N9 and N9/N10
are 28.37(11), 26.55(11), 22.31(15) and 44.52(13)ꢀ. The deviation
from planarity facilitates the assembly of a two-dimensional
network, but as a consequence, tpy-tpy face-to-face p-interactions
are not able to play a significant role in crystal packing (see below).
The cobalt(II) nodes in [{Co(3)2(SCN)2$2MeOH}n] are connected
into a (4,4)-net and Fig. 8a depicts part of one sheet and highlights
one [4 + 4] metallomacrocyclic building block. The assembly
therefore resembles that in [{2Co(1)2(NCS)2$5H2O}n]. The imid-
azole substituents protrude from the upper and lower surfaces of
the two-dimensional network (Fig. 8b). Each imidazole ring in one
sheet is directed into a pocket formed by a tpy domain and thio-
cyanate ligands of the next sheet, and the packing interactions
The reaction of ligand 4 with Co(SCN)2 was performed using
a layering technique in MeOH and 1,2-Cl2C6H4 which yielded
crystals within a month at room temperature. Crystals suitable
for X-ray diffraction were selected, and structural determination
confirmed a formulation of [{Co(4)(MeOH)2(NCS)2}n]. Analysis
of the bulk sample was consistent with a formulation of
[{Co(4)(MeOH)2(NCS)2}n]$0.33H2O. The coordination polymer
[{Co(4)(MeOH)2(NCS)2}n] crystallizes in the orthorhombic
space group Pbca, and the asymmetric unit is shown in Fig. 9. A
i
i
ꢀ
bond to tpy donor atom N3 (Co1–N3 ¼ 2.1658(16) A, symmetry
code i ¼ ½ ꢁ x, ꢁy, ꢁ½ + z) completes the octahedral
between adjacent sheets involve weak CHimidazole/p, CHpyridine
/
S and CHimidazole/S contacts. Small cavities in the lattice are
occupied by MeOH solvent molecules.
Fig. 7 The asymmetric unit in [{Co(3)2(SCN)2$2MeOH}n] (ellipsoids
plotted at 30% probability level; solvent molecules and H atoms except
for imidazole NH are excluded). Only the major occupancy sites of the
ligand containing N8/N9/N10 are shown (see text). Hashed lines
emphasize that the overall coordination geometry at Co1 is octahedral.
Important bond parameters: Co1–N1 ¼ 2.063(2), Co1–N2 ¼ 2.062(2),
Co1–N3 ¼ 2.2188(18), Co1–N8 ¼ 2.2242(10), N1–C1 ¼ 1.156(4), N2–C2
Fig. 8 (a) Part of one sheet in [{Co(3)2(SCN)2$2MeOH}n] with one [4 +
4] metallomacrocyclic assembly motif coloured red. (b) A view down the
a-axis showing interlocking of adjacent sheets. In both diagrams, Co
atoms are shown in ball representation.
ꢀ
¼ 1.165(3), C1–S1 ¼ 1.615(3), C2–S2 ¼ 1.624(3) A; Co1-N1-C1 ¼
156.85(18), Co1-N2-C2 ¼ 154.79(19)ꢀ.
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coordination sphere of Co1. Each ligand 4 bridges between a pair
of cobalt(II) centres and the trans-arrangement of the bridging
ligands means that each metal ion acts as a linear node. The
remaining four coordination sites are occupied by thiocyanate
and methanol ligands (Fig. 9). Of the three possible conforma-
tions shown in Scheme 2, ligand 4 adopts a trans,trans-arrange-
ment. Atom N2 of the tpy unit and N4 of the dimethylamino
group remain non-coordinated. The tpy domain deviates from
planarity, the angles between the least squares planes of the
pyridine rings containing N1/N2 and N2/N3 being 24.01(9) and
29.02(19)ꢀ. In contrast, the phenyl ring is coplanar with the
pyridine unit to which it is bonded (angle between the ring planes
¼ 2.10(10)ꢀ). The curved profile of ligand 4 results in the prop-
agation of undulating chains that follow the crystallographic
a-axis (Fig. 10a).
The chains in [{Co(4)(MeOH)2(NCS)2}n] mesh together to
give sheets, and chains in adjacent sheets associate through face-
Fig. 10 (a) Part of one chain in [{Co(4)(MeOH)2(NCS)2}n] running
parallel to the c-axis. (b) Packing of two adjacent chains showing
p-stacking of pairs of phenylpyridine units.
to-face p-stacking of centrosymmetric pairs of phenylpyridine
ꢀ
units (inter-plane separation ¼ 3.39 A, Phcentoid/pycentroid
¼
3.60 A).34 The relative orientations of the Phpy units render this
a highly efficient interaction (Fig. 11a). The Me2N substituent is
accommodated in a shallow bowl-shaped cavity between the
outer pyridine rings of the tpy unit of the adjacent ligand, and is
involved in the close CH/p contact40 shown in Fig. 11b
ꢀ
ii
ꢀ
(C23H23A/centroid of ring with N1 ¼ 2.8 A, symmetry code ii
¼ 1 ꢁ x, ꢁy, 1 ꢁ z). The offset arrangement of the Phpy units
required for effective p-stacking precludes the NMe2 group (red
in Fig. 11) from engaging in CH/p interactions with both sides
of the tpy domain (blue in Fig. 11).
A comparison of the one-dimensional coordination polymers
formed between ligands 4 and 5 (3,20:60,300- and 4,20:60,400-tpy
metal-binding domain, respectively) and a linear metal node, M, is
instructive. The diagrammatic representation shown in Scheme 3 is
based on the structures determined for [{Co(4)(MeOH)2(NCS)2}n]
Fig. 11 Offset face-to-face p-stacking of a centrosymmetric pair of
phenylpyridine units in [{Co(4)(MeOH)2(NCS)2}n], and the concomitant
evolution of a CH/p interaction involving an H atom of the NMe2 unit
and pyridine ring containing atom N1ii (symmetry code ii ¼ 1 ꢁ x, ꢁy,
1 ꢁ z).
(this work) and [{Cd(5)(OH2)2(ONO2)(O2NO)$H2O}n].8 Although
these polymers do not contain a common metal ion, both metal
nodes are linear (N1-Co1-N3 ¼ 178.35(7)ꢀ and N1-Cd1-N3 ¼
174.17(13)ꢀ, and the metal/metal separations along the chain are
ꢀ
ꢀ
similar (Co/Co ¼ 13.1339(7) A and Cd/Cd ¼ 12.472(3) A).
Despite the change in the substitution pattern on going from ligand
5 to 4, Scheme 3 reveals similarities in the zig-zag topologies
(distances between turning points and angle at each turning point).
In practice, the change from a 4,20:60,400- to 3,20:60,300- substitution
pattern on going from 5 to 4 is accompanied by a buckling of each
tpy unit, and each undulating sheet in [{Co(4)(MeOH)2(NCS)2}n] is
replaced by a planar array in [{Cd(5)(OH2)2(ONO2)(O2NO)$
H2O}n] (Fig. 12). This influences the manner in which chains in
adjacent sheets interact. In both compounds, the recognition events
between adjacent chains are p-stacking. However, whereas in
[{Co(4)(MeOH)2(NCS)2}n] this involves interactions between pairs
Fig. 9 The asymmetic unit in [{Co(4)(MeOH)2(NCS)2}n] with ellipsoids
plotted at 40% probability level and H atoms omitted. Hashed lines
indicate the propagation of the polymer chain. Selected bond parameters:
Co1–N1 ¼ 2.1677(16), Co1–N40 ¼ 2.0627(17), Co1–N30 ¼ 2.0755(17),
Co1–O60 ¼ 2.1057(16), Co1–O50 ¼ 2.1093(16), C19–N4 ¼ 1.373(3), N4–
of
phenylpyridine
units,
stacking
interactions
in
ꢀ
[{Cd(5)(OH2)2(ONO2)(O2NO)$H2O}n] are between pairs of pyri-
dine rings. The resulting packing motif (Fig. 13) is also observed
C23 ¼ 1.455(3), N4–C22 ¼ 1.459(3) A; C30-N30-Co1 ¼ 154.56(16), C40-
N40-Co1 ¼ 160.31(17), N40-Co1-N30 ¼ 178.30(7)ꢀ.
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Fig.
13 Packing
of
two
adjacent
chains
in
[{Cd(5)(OH2)2(ONO2)(O2NO)$H2O}n].
Conclusions
The single crystal structures of the complexes [{2Co(1)2(N-
CS)2$5H2O}n], [{Co(3)2(SCN)2$2MeOH}n] and [{Co(2)2(N-
CS)2$0.67C2H4Cl2$MeOH$H2O}n] reveal the assembly of (4,4)
or (6,3) nets. These three coordination polymers contain 40-
substituted 4,20:60,400-tpy ligands connected through trans-
{Co(Ntpy)4(NCS)2} units (i.e. square-planar metal nodes), and
reveal a common pattern: significant twisting of the tpy back-
bone facilitates network assembly and as a result, packing
interactions are unable to utilize face-to-face p-stacking of tpy
domains. In [{2Co(1)2(NCS)2$5H2O}n], the coordinated ligands
1 do exhibit p-stacking of pairs of Phpy units between adjacent
two-dimensional networks, but these stacking interactions are
not as extensive as is present in related systems containing linear
and bent nodes.
Scheme 3 Comparison of the zig-zag chains defined by connectivity
through linear metal nodes of the outer N-donors in ligands 4 (top) and 5
(bottom).
The
one-dimensional
coordination
polymer
[{Co(4)(MeOH)2(NCS)2}n] features undulating, zig-zag chains
which are locked together to produce buckled sheets. A
comparison between this assembly and the planar sheets
observed in [{Cd(5)(OH2)2(ONO2)(O2NO)$H2O}n],8 suggests
that the structural modification is a consequence of optimizing
face-to-face p-stacking interactions between adjacent 40-(4-
dimethylaminophenyl)-4,20:60,400-terpyridine or 40-(4-dimethyla-
minophenyl)-3,20:60,300-terpyridine ligands. Whereas the rigidly
defined orientation of the donor atoms in 4,20:60,400-terpyridines
predetermines the topology and topography of self-assembled
one-dimensional systems, the use of the rotationally variable
3,20:60,300-terpyridine allows access not only to one-dimensional
systems as shown here, but also to materials with a higher
dimensionality. This molecular diversity can be seen as an
example of fuzzy logic41 in the engineering of molecular mate-
rials. We are currently undertaking systematic studies of the
variation in coordination polymer assemblies resulting from
reactions of a given metal node and different isomers of
40-substituted terpyridines.
[{Zn2(OAc)4(1)}n] and in analogous complexes containing 40-(4-
bromophenyl)-4,20:60,400-terpyridine and 40-(4-methylthiophenyl)-
4,20:60,400-terpyridine, each of which contains linear {Zn2(OAc)4}
nodes.6,7 We propose that the switch from planar to undulating
chains and sheets is a consequence of optimizing the p-stacking
interactions.
Acknowledgements
We thank the Swiss National Science Foundation, the European
Research Council (Advanced Grant 267816 LiLo), and the
University of Basel for financial support. GZ thanks the Novartis
Foundation, formerly Ciba-Geigy Jubilee Foundation for
support.
Fig. 12 Arrangements of two adjacent polymer chains in one
sheet
in
(a)/(b)
[{Co(4)(MeOH)2(NCS)2}n],
and
(c)/(d)
[{Cd(5)(OH2)2(ONO2)(O2NO)$H2O}n].
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20 CSD version 5.32 with updates, Nov 2011.
References
21 F. H. Allen, Acta Crystallogr., Sect. B: Struct. Sci., 2002, 58, 380.
22 B.-C. Wang, X.-L. Chen, H.-M. Hu, H.-L. Yao and G.-L. Xue, Inorg.
Chem. Commun., 2009, 12, 856.
ꢁ
ꢁ
1 M. Barquın, J. Cancela, M. J. Gonzalez Garmendia, J. Quintanilla
and U. Amador, Polyhedron, 1998, 17, 2373.
2 G. W. V. Cave and C. L. Raston, J. Supramol. Chem., 2002, 2, 317.
3 L. Hou and D. Li, Inorg. Chem. Commun., 2005, 8, 190.
4 X.-Z. Li, M. Li, Z. Li, J.-Z. Hou, X.-C. Huang and D. Li, Angew.
Chem., Int. Ed., 2008, 47, 6371.
23 C. Liu, Y.-B. Ding, X.-H. Shi, D. Zhang, M.-H. Hu, Y.-G. Yin and
D. Li, Cryst. Growth Des., 2009, 9, 1275.
24 Bruker Analytical X-ray Systems, Inc., 2006, APEX2, version 2 User
Manual, M86-E01078, Madison, WI.
25 A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori and M. Camalli, J. Appl. Cryst., 1994, 27,
435.
26 P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout and
D. J. Watkin, J. Appl. Crystallogr., 2003, 36, 1487.
27 Stoe & Cie IPDS software v. 1.26, Stoe & Cie, Darmstadt, Germany,
1996.
28 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008,
64, 112.
29 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
30 I. J. Bruno, J. C. Cole, P. R. Edgington, M. K. Kessler, C. F. Macrae,
P. McCabe, J. Pearson and R. Taylor, Acta Crystallogr., Sect. B:
Struct. Sci., 2002, 58, 389.
31 C. F. Macrae, I. J. Bruno, J. A. Chisholm, P. R. Edgington,
P. McCabe, E. Pidcock, L. Rodriguez-Monge, R. Taylor, J. van de
Streek and P. A. Wood, J. Appl. Crystallogr., 2008, 41, 4646.
32 H. Walba and R. W. Isensee, J. Org. Chem., 1961, 26, 2789.
33 P. Koch, D. Schollmeyer and S. Laufer, Acta Crystallogr., Sect. E:
Struct. Rep. Online, 2009, 65, o573.
34 C. Janiak, J. Chem. Soc., Dalton Trans., 2000, 3885.
35 M. Munakata, L. P. Wu and T. Kuroda-Sowa, Adv. Inorg. Chem.,
1998, 46, 173.
5 E. C. Constable, G. Zhang, C. E. Housecroft, M. Neuburger and
J. A. Zampese, CrystEngComm, 2009, 11, 2279.
6 E. C. Constable, G. Zhang, E. Coronado, C. E. Housecroft and
M. Neuburger, CrystEngComm, 2010, 12, 2139.
7 E. C. Constable, G. Zhang, C. E. Housecroft, M. Neuburger and
J. A. Zampese, CrystEngComm, 2010, 12, 2146.
8 E. C. Constable, G. Zhang, C. E. Housecroft, M. Neuburger and
J. A. Zampese, CrystEngComm, 2010, 12, 3733.
9 B.-C. Wang, Q.-R. Wu, H.-M. Hu, X.-L. Chen, Z.-H. Yang,
Y.-Q. Shangguan, M.-L. Yang and G.-L. Xue, CrystEngComm,
2010, 12, 485.
10 J. Song, B.-C. Wang, H.-M. Hu, L. Gou, Q.-R. Wu, X.-L. Yang,
Y.-Q. Shangguan, F.-X. Dong and G.-L. Xue, Inorg. Chim. Acta,
2011, 366, 134.
€
11 J. Heine, J. Schmedt auf der Gunne and S. Dehnen, J. Am. Chem.
Soc., 2011, 133, 10018.
12 X.-Z. Li, X.-P. Zhou, D. Li and Ye-Gao Yin, CrystEngComm, 2011,
13, 6759.
13 K.-R. Ma, F. Ma, Y.-L. Zhu, L.-J. Yu, X.-M. Zhao, Y. Yang and
W.-H. Duan, Dalton Trans., 2011, 40, 9774.
14 J. Song, B.-C. Wang, H.-M. Hu, L. Gou, Q.-R. Wu, X.-L. Yang,
Y.-Q. Shangguan, F.-X. Dong and G.-L. Xue, Inorg. Chim. Acta,
2011, 366, 134.
36 M. J. Zaworotko, Chem. Commun., 2001, 1.
37 S. Tsuzuki and A. Fujii, Phys. Chem. Chem. Phys., 2008, 10, 2584.
38 E. C. Constable, C. E. Housecroft, E. A. Medlycott, M. Neuburger,
F. Reinders, S. Reymann and S. Schaffner, Inorg. Chem. Commun.,
2008, 11, 805.
15 E. C. Constable, G. Zhang, C. E. Housecroft and J. A. Zampese,
CrystEngComm, 2011, 13, 6864.
16 E. C. Constable, C. E. Housecroft, P. Kopecky, M. Neuburger,
J. A. Zampese and G. Zhang, CrystEngComm, 2012, 14, 446.
€
17 F. Krohnke, Synthesis, 1976, 1.
18 J. Wang and G. S. Hanan, Synlett, 2005, 1251.
ꢁ~ ~
19 J. Granifo, M. Vargas, M. T. Garland, A. Ibanez, R. Gavino and
R. Baggio, Inorg. Chem. Commun., 2008, 11, 1388.
39 J. McMurtie and I. Dance, CrystEngComm, 2009, 11, 1141.
40 M. Nishio, Y. Umezawa, K. Honda, S. Tsuboyama and H. Suezawa,
CrystEngComm, 2009, 11, 1757.
41 L. A. Zadeh, Inf. Control, 1965, 8, 338.
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