Construction of diverse supramolecular assemblies of dimetal subunits differing in coordinated water molecules via strong hydrogen bonding interactions: Synthesis, crystal structures and spectroscopic properties

Article abstract of DOI:10.1007/s12039-014-0685-x

Three new supramolecular assemblies (constructed through strong hydrogen bonding) of [ Cu₂(bpta)₂(fum)(H₂O)₂](ClO₄)₂ (2) and [Cu₂(bpta)₂(tdc)(H₂O) (ClO₄)](ClO₄)^.3H₂O (3), which are synthesised by one pot self-assembly of the metal salt, bpta ligand and the corresponding dicarboxylate under the same reaction conditions, are reported (where adc = acetylene dicarboxylate, fum = fumarate, tdc = 2,5-thiophenedicarboxylate and bpta =N,-Rfnet′-bis(2-pyridylmethyl)-tert-butylamine). These compounds have varying degrees of coordinated water molecules per dimetal subunits (four for 1, two for 2 and one for 3, respectively). Furthermore, the orientation of the coordinated water molecules in 1 and 2, with respect to the mono (carboxylato)-bridged dimetal subunit, is different (cis and trans, respectively). On the other hand, there is a coordinated perchlorate ion in 3 making the two metal centers inequivalent. Unlike 1 and 3, there are no lattice water molecules in 2. This difference in the dimetal subunit in 1-3 and the presence or absence of the lattice water molecules are the keys to forming the diverse supramolecular assemblies. In 1 and 3, the involvement of lattice water molecules in the construction of such assemblies is distinctly different. In case of 2, the formation of supramolecular assembly depends on the coordinated water molecule (trans to each other) and thus a ladder shaped supramolecular assembly is the result. The strength of hydrogen bonding observed in the networks of 1-3 is indicated in the O· · ·O distances (2.596 ? to 3.160 ?) and the O-H.O angles 124° to 176°. All are characterised by elemental analysis, FTIR spectroscopy and single crystal X-ray diffraction studies. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s12039-014-0685-x

J. Chem. Sci. Vol. 126, No. 5, September 2014, pp. 1515–1523. ꢀc Indian Academy of Sciences.
Construction of diverse supramolecular assemblies of dimetal subunits
differing in coordinated water molecules via strong hydrogen bonding
interactions: Synthesis, crystal structures and spectroscopic properties
a,b
a,∗
SADHIKA KHULLAR and SANJAY K MANDAL
a
Department of Chemical Sciences, Indian Institute of Science Education and Research, Mohali, Sector 81,
Manauli PO, S.A.S. Nagar, Mohali (Punjab) 140 306, India
Department of Chemistry, DAV University, Jalandhar, Punjab 144 001, India
b
e-mail: sanjaymandal@iisermohali.ac.in
MS received 3 May 2014; revised 27 June 2014; accepted 29 June 2014
Abstract. Three new supramolecular assemblies (constructed through strong hydrogen bonding) of
.
2
[
Co2(bpta) (adc)(H2O)4](ClO4) 2H2O (1), [Cu2(bpta) (fum)(H2O)2](ClO4)2 (2) and [Cu2(bpta)2(tdc)(H2O)
2
2
.
(
ClO4)](ClO4) 3H2O (3), which are synthesised by one pot self-assembly of the metal salt, bpta ligand and
the corresponding dicarboxylate under the same reaction conditions, are reported (where adc = acetylene
ꢁ
dicarboxylate, fum = fumarate, tdc = 2,5-thiophenedicarboxylate and bpta = N,N -bis(2-pyridylmethyl)-tert-
butylamine). These compounds have varying degrees of coordinated water molecules per dimetal subunits (four
for 1, two for 2 and one for 3, respectively). Furthermore, the orientation of the coordinated water molecules
in 1 and 2, with respect to the mono (carboxylato)-bridged dimetal subunit, is different (cis and trans, respec-
tively). On the other hand, there is a coordinated perchlorate ion in 3 making the two metal centers inequivalent.
Unlike 1 and 3, there are no lattice water molecules in 2. This difference in the dimetal subunit in 1–3 and the
presence or absence of the lattice water molecules are the keys to forming the diverse supramolecular assem-
blies. In 1 and 3, the involvement of lattice water molecules in the construction of such assemblies is distinctly
different. In case of 2, the formation of supramolecular assembly depends on the coordinated water molecule
(
trans to each other) and thus a ladder shaped supramolecular assembly is the result. The strength of hydrogen
bonding observed in the networks of 1–3 is indicated in the O· · · O distances (2.596 Å to 3.160 Å) and the O-
◦
◦
H· · · O angles 124 to 176 . All are characterised by elemental analysis, FTIR spectroscopy and single crystal
X-ray diffraction studies.
Keywords. Supramolecular; hydrogen bonding; flexible ligand; dicarboxylates.
1
. Introduction
atom clusters as building blocks adds to the advan-
tage due to different binding abilities of the metal cen-
tre. The selection of ancillary ligands and the multi-
topic organic linkers is crucial in making such assem-
blies with varied dimensionality. The role of ancillary
ligands that surround and protect the metal cores leav-
ing open sites for the linkers is of great importance in
making such supramolecular assemblies. The strategy
of a step-wise association of discrete synthons, such
as mono- or di-nuclear metal complexes, to construct
supramolecular assemblies of higher dimensions shows
the hierarchical importance of the two bondings (coor-
dination bonds and hydrogen bonds) that are orthogo-
The field of supramolecular chemistry has seen an
exponential growth in the last few decades due to
interdisciplinary interests in crystal engineering of
supramolecular assemblies that are targeted for a vari-
ety of potential applications, such as catalysis, sepa-
ration, sensors, gas storage, luminescent materials, ion
exchange, magnetism, etc.1 Synthons in a coordina-
tion supramolecular assembly are held together through
various interactions, such as metal-donor atom coordi-
nate bonds, strong and/or weak hydrogen bonds, π − π
stacking of aromatic moieties, C-H. . . O interactions,
–3
4
5
–10
etc. Among these various interactions, hydrogen bond-
nal in nature.
For our interests to explore and iden-
ing is the most important one to study for its importance
in the biological systems, in understanding the struc-
ture of water, etc. The use of metal centres or metal
tify the factors governing the formation of supramolec-
ular assemblies through various interactions, a system-
atic study has been carried out using a flexible tridentate
ancillary ligand and multitopic dicarboxylate linkers
with Co(II) and Cu(II) as the metal centre.
∗
For correspondence
1
515

1
516
Sadhika Khullar and Sanjay K Mandal
ꢁ
In this paper, using the tridentate ligand, bpta =N,N - a Perkin-Elmer Spectrum I spectrometer with samples
bis(2-pyridylmethyl)-tert-butylamine, we report the prepared as KBr pellets.
formation of diverse supramolecular assemblies from
Caution! In this study metal perchlorates were used
the dinuclear metal complexes: [Co (bpta) (adc) without any problem but special care should be taken
2
2
(
H O) ](ClO ) ·2H O (1), [Cu (bpta) (fum)(H O) ] while handling such dangerous salts.
2
4
4
2
2
2
2
2
2
(
ClO ) (2) and [Cu (bpta) (tdc)(H O)(ClO )](ClO )·
4 2 2 2 4 4
2
3
H O (3), where adc = acetylene dicarboxylate, fum
2
2
.3 General synthesis method
=
fumarate and tdc = 2,5-thiophenedicarboxylate. The
dimetal subunits in these complexes are connected
through extensive hydrogen bonding network of coor-
dinated water molecules, lattice water molecules (in
case of 1 and 3) and uncoordinated oxygen atoms of
the carboxylate groups. Scheme 1 shows the structure
of the ligand and dicarboxylate linkers used in this
study.
In a round bottom flask (RBF) y mmol of M(ClO ) and
4
2
y mmol of the tridentate ligand were dissolved in 1.5
to 3 mL of methanol while stirring. To this was added
a clear solution of the disodium salt of a dicarboxy-
late (Na dc) which was prepared using y/2 mmol of the
2
dicarboxylic acid and y mmol of sodium hydroxide in 1
mL methanol and 1 mL to a minimum amount of water.
The reaction mixture was stirred for another 3 to 4 hours
at room temperature. Either a clear solution (in case of 1
and 3) or a solid precipitate (in case of 2) was obtained
which was processed further to get the desired product.
2. Experimental
2.1 Materials and methods
.
2
2
.3a [Co (bpta) (adc)(H O) ](ClO ) 2H O (1): It
2
2
2
4
4
2
All chemicals and solvents used for synthesis were
obtained from commercial sources and were used
as received, without further purification. All reac-
tions were carried out under aerobic conditions. The
bpta ligand was prepared by modifying the literature
was prepared using the sodium salt of acetylene dicar-
boxylic acid {14 mg (0.125 mmol) of acetylene dicar-
boxylic acid and 10 mg (0.25 mmol) of sodium hydrox-
ide}, 48 mg (0.125 mmol) of Co(ClO ) in 3 mL
4
2
11
methanol and 32 mg (0.125 mmol) of bpta. No precip-
itate was obtained; the pink filtrate was evaporated to
dryness. After re-dissolving the solid residue in 2 mL
of dry methanol completely, 10 mg of KCl was added
and stirred for 10 h. A white solid that appeared was
procedure.
2.2 Physical measurements
1
The H NMR spectrum of the ligand was obtained in removed via filtration and the filtrate was evaporated
◦
CDCl solution at 25 C on a Bruker ARX-400 spec- to dryness to isolate a pink solid. Yield: 39 mg (54%).
3
trometer; chemical shifts were reported relative to the Anal. Calcd (%) for C H N Co Cl O (MW 1047.6):
36
54
6
2
2
18
residual solvent signals. The elemental analysis (C, H, C, 41.27; H, 5.15; N, 8.02. Found: C, 41.62; H, 5.25;
−1
N) was carried out using a Mettler CHNS analyzer. IR N, 8.09. Selected FTIR peaks (KBr, cm ): 3404, 1567,
−1
spectra were measured in the 4000–400 cm range on 1435, 1345, 1096, 764, 621.
Scheme 1. Structures of the bpta ligand and the dicarboxylates.

Supramolecular assemblies of dimetal subunits
1517
Table 1. Crystal structure data and refinement parameters for 1, 2 and 3.
1
2
3
Chemical formula
Formula Weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C36H54Cl2Co2N6O18
1047.65
296(2)
C36H48Cl2Cu2N6O14
986.78
C38H52Cl2Cu2N6O16S
1078.90
296(2)
296(2)
0.71073
Monoclinic
P21/c
15.2144(15)
23.344(2)
26.753(3)
90
0.71073
Monoclinic
C2/c
19.9346(10)
18.8069(10)
13.6719(8)
90
0.71073
Monoclinic
P21/n
12.3812(4)
26.8191(9)
14.3028(5)
90
b (Å)
c (Å)
α( )
◦
◦
β( )
99.364(5)
122.227(3)
96.322(2)
◦
γ ( )
Z
Volume (Å )
90
8
90
4
4336.0(4)
1.512
90
4
4720.4(3)
1.518
3
9375.1(16)
1.484
3
Density (g/cm )
−1
μ (mm
)
0.898
1.16 to 25.14
1.175
1.86 to 25.10
1.132
1.52 to 25.10
◦
◦
◦
◦
◦
◦
Theta range
F(000)
4352
87093
16568
7608
0.1225
1133
2040
12866
3863
2476
0.0555
278
2232
32255
8388
4788
0.0825
589
Reflections Collected
Independent reflections
Reflections with I > 2σ(I)
Rint
Number of parameters
GOF on F
2
1.049
0.0841/0.2216
0.1896/0.2819
1.401 and −1.029
0.967
0.0536/0.1527
0.0908/0.1839
0.561 and −0.533
0.983
a
b
2
Final R /wR (I > 2σ(I))
0.0541/0.1395
0.1012/ 0.1589
0.864 and −0.575
1
a
1
b
2
R /wR (all data)
−3
Largest diff. peak and hole (eÅ
)
a
b
2
o
2 2
2 2 1/2
o
2
2
o
2
2
o
2
c
R1 = ꢀꢂFo| − |Fcꢂ/ꢀ|Fo|. wR2 = [ꢀw(F − F ) /ꢀw(F ) ] , where w = 1/[σ (F ) + (aP) + bP], P = (F + 2F )/3.
c
.
2
.3b [Cu (bpta) (fum)(H O) ](ClO ) (2): It was 2.3c [Cu (bpta) (tdc)(H O)(ClO )](ClO ) 3H O (3):
2
2
2
2
4
2
2
2
2
4
4
2
prepared using the sodium salt of fumaric acid {14.5 It was prepared using the sodium salt of thiophene
mg (0.125 mmol) of fumaric acid and 10 mg (0.25 dicarboxylic acid {21.5 mg (0.125 mmol) of thiophene
mmol) of sodium hydroxide}, 46.5 mg (0.125 mmol) of dicarboxylic acid and 10 mg (0.25 mmol) of sodium
Cu(ClO ) in 3 mL methanol and 32 mg (0.125 mmol) hydroxide}, 46.5 mg (0.125 mmol) of Cu(ClO ) in
4
2
4 2
of bpta. A blue precipitate was collected via filtra- 3 mL methanol and 32 mg (0.125 mmol) of bpta.
tion, washed with methanol and air-dried. Yield: 41 mg No precipitate was obtained and the dark blue filtrate
(
69%). Anal. Calcd (%) for C H N Cu Cl O (MW was evaporated to dryness. After re-dissolving the solid
36 48 6 2 2 14
9
86.8): C, 44.98; H, 4.86; N, 8.57. Found: C, 45.34; residue in 2 mL of dry methanol completely, 10 mg
−1
H, 4.63; N, 8.38. Selected FTIR peaks (KBr, cm ): of KCl was added and stirred for 3 h. A white solid
3438, 1606, 1563, 1481, 1441, 1380, 1077, 762, 698, that appeared was filtered off and the filtrate was evap-
619.
orated to dryness to isolate a dark blue solid. Yield: 64
Scheme 2. Synthesis of 1–3.
Figure 1. Structure of the dimetal subunit in 1.

1
518
Sadhika Khullar and Sanjay K Mandal
mg (98%). Anal. Calcd (%) for C H N Cu Cl SO
(
CHN analysis two water molecules could be included
MW 1060.9): C, 43.02; H, 4.71; N, 7.92. Found: C, while three water molecules were found in its X-ray
38
50
6
2
2
15
−1
43.36; H, 4.58; N, 7.93. Despite our best efforts, in the crystal structure. Selected FTIR peaks (KBr, cm ):
Table 2. Selected bond distances and bond angles for 1, 2 and 3.
1
Bond distances (Å)
Co1-O1
Co1-O3
Co1-O4
Co1-N1
Co1-N2
Co1-N3
2.106(5)
2.115(6)
2.144(7)
2.253(6)
2.121(7)
2.102(6)
Co2-O5
Co2-O8
Co2-O7
Co2-N4
Co2-N5
Co2-N6
2.119(5)
2.095(5)
2.120(5)
2.235(6)
2.095(6)
2.116(6)
Co3-O9
Co3-O11
Co3-O12
Co3-N7
Co3-N8
Co3-N9
2.106(5)
2.126(5)
2.123(5)
2.242(6)
2.140(7)
2.118(6)
Co4-O13
Co4-O15
Co4-O16
Co4-N10
Co4-N11
Co4-N12
2.093(5)
2.073(6)
2.178(5)
2.271(6)
2.103(7)
2.134(7)
◦
Bond angles ( )
N3-Co1-O1
O1-Co1-O3
O1-Co1-N2
N3-Co1-O4
O3-Co1-O4
N3-Co1-N1
O3-Co1-N1
O4-Co1-N1
N3-Co1-O3
N3-Co1-N2
O3-Co1-N2
O1-Co1-O4
N2-Co1-O4
O1-Co1-N1
N2-Co1-N1
173.3(3)
89.3(2)
88.1(2)
87.6(3)
87.6(3)
77.6(2)
166.4(3)
97.8(3)
90.2(3)
98.6(3)
97.3(3)
85.7(2)
172.1(2)
103.5(2)
78.8(2)
N5-Co2-N6
N5-Co2-O5
N6-Co2-O5
O8-Co2-O7
O5-Co2-O7
O8-Co2-N4
O5-Co2-N4
N5-Co2-O8
O8-Co2-N6
O8-Co2-O5
N5-Co2-O7
N6-Co2-O7
N5-Co2-N4
N6-Co2-N4
O7-Co2-N4
97.3(2)
91.0(2)
171.7(2)
91.6(2)
85.8(2)
163.0(2)
104.9(2)
91.7(2)
89.6(2)
89.7(2)
175.4(2)
86.0(2)
79.5(2)
77.2(2)
98.1(2)
O9-Co3-N9
N9-Co3-O12
N9-Co3-O11
O11-Co3-N8
N9-Co3-N7
O11-Co3-N7
O9-Co3-N8
O12-Co3-N8
O9-Co3-N7
O12-Co3-N7
N8-Co3-N7
O9-Co3-O12
O9-Co3-O11
O12-Co3-O11
N9-Co3-N8
174.6(2) O15-Co4-O13
88.1(2)
87.7(2)
92.1(2)
90.4(2)
78.4(2)
O13-Co4-N11 172.2(2)
O13-Co4-N12
O15-Co4-O16
N11-Co4-O16
83.0(2)
87.1(3)
93.3(3)
162.9(2) O15-Co4-N10 107.9(2)
84.1(2) N11-Co4-N10 77.6(3)
172.5(2) O16-Co4-N10 162.0(2)
98.6(2) O15-Co4-N11 88.5(3)
106.3(2) O15-Co4-N12 170.7(2)
77.4(2)
88.8(2)
91.9(2)
87.3(2)
99.5(2)
N11-Co4-N12 100.6(3)
O13-Co4-O16
N12-Co4-O16
O13-Co4-N10
N12-Co4-N10
93.6(2)
90.9(3)
96.8(2)
75.8(2)
2
Bond distances (Å)
Cu1-N1
Cu1-N2
1.967(4)
1.955(4)
2.065(4)
Cu1-O1
Cu1-O2
2.485(4)
1.945(3)
Cu1-N3
Bond angles ( )
◦
O2-Cu1-N2
N2-Cu1-N1
N2-Cu1-N3
O2-Cu1-O1
N1-Cu1-O1
94.35(15)
O2-Cu1-N1
97.12(16)
165.78(17) O2-Cu1-N3 170.12(14)
84.99(15)
103.37(15) N2-Cu1-O1
85.79(15)
N1-Cu1-N3
85.14(16)
83.39(15)
86.37(14)
N3-Cu1-O1
3
Bond distances (Å)
Cu1-N1
Cu1-N2
Cu1-N3
Cu1-O1
1.950(4)
2.053(4)
1.964(4)
1.940(3)
Cu2-N4
Cu2-N5
Cu2-N6
Cu2-O3
Cu2-O5
1.980(4)
2.062(4)
1.970(4)
1.942(3)
2.361(4)
◦
Bond angles ( )
O1-Cu1-N1
N1-Cu1-N3
N1-Cu1-N2
O1-Cu1-N3
O1-Cu1-N2
N3-Cu1-N2
O3-Cu2-O5
N4-Cu2-O5
98.27(17)
O3-Cu2-N4
96.47(16)
163.54(18) O3-Cu2-N5 169.19(16)
85.03(17)
94.09(16)
N4-Cu2-N5
N6-Cu2-O5
84.23(16)
90.01(16)
97.99(15)
96.36(17)
169.15(16) N5-Cu2-O5
84.83(16)
92.82(16)
85.50(15)
O3-Cu2-N6
N6-Cu2-N4 166.60(18)
N6-Cu2-N5 83.90(17)

Supramolecular assemblies of dimetal subunits
1519
3
6
435, 1610, 1586, 1377, 1352, 1121, 1108, 1091, 777, using PLATON.15 The final positional and thermal
24.
parameters of the non-hydrogen atoms for all structures
are listed in the CIF files.
2.4 Single crystal X-ray data collection
and refinement
3. Results and Discussion
From a batch of crystals of each compound that was
transferred from mother liquor to mineral oil for manip-
ulation and selection, a single crystal was placed inside
a nylon loop on a goniometer head. Initial crystal eval-
uation and data collection were performed on a Kappa
APEX II diffractometer equipped with a CCD detector
3
.1 Synthesis
Supramolecular assemblies of 1–3 were prepared from
the one pot self-assembly reaction of the metal salt, bpta
and the respective sodium salt of the acid (scheme 2).
In case of 1 and 3, the desired product was obtained
from the filtrate utilizing the process to remove free
(with the crystal-to-detector distance fixed at 60 mm)
and sealed-tube monochromated MoKα radiation and
interfaced to a PC that controlled the crystal centering,
unit cell determination, refinement of the cell parame-
NaClO with slight excess of KCl in dry methanol. On
4
the other hand, a blue solid of 2 was obtained directly
under the same reaction conditions. It should be noted
here that the combination of Cu(II) and adc linker did
not allow the isolation of a product similar to 1; in
fact, there are only a few adc complexes reported in the
12
ters and data collection through the program APEX2.
By using the program SAINT12 for the integration of
the data, reflection profiles were fitted, and values of
2
2
16,17
F and σ(F ) for each reflection were obtained. Data
literature where any ancillary ligand is used.
.2 Spectroscopic data
The IR spectra of 1, 2 and 3 were recorded in the solid
were also corrected for Lorentz and polarization effects.
12
The subroutine XPREP was used for the processing of
data that included determination of space group, appli-
3
12
cation of an absorption correction (SADABS), merg-
ing of data, and generation of files necessary for solu-
tion and refinement. The crystal structures were solved
−1
state as KBr pellets. The peaks at 3404 cm (1), 3438
−
1
−1
cm (2) and 3434 cm (3) correspond to the O-H
stretching frequencies of water molecules. The asym-
metric and symmetric stretching frequencies for the car-
13
and refined using SHELX 97. In each case, the space
group was chosen based on systematic absences and
confirmed by the successful refinement of the struc-
ture. Positions of most of the non-hydrogen atoms were
obtained from a direct method solution. Several full-
matrix least-squares/difference Fourier cycles were per-
formed, locating the remainder of the non-hydrogen
atoms. All non-hydrogen atoms were refined with
anisotropic displacement parameters. In order to obtain
reasonable thermal parameters compared to other
atoms, the lowest residual factors and optimum good-
ness of fit with convergence of refinement, occupancy
factors of the oxygen atoms in the disordered perchlo-
rate anions were adjusted accordingly. All hydrogen
atoms of 1–3 except those for lattice water molecules
O37 and O15 in 1 and 3, respectively, were placed
in ideal positions and refined as riding atoms with
individual isotropic displacement parameters. In the
final difference Fourier map of 1, the largest resid-
−1
boxylate group appears at 1567 and 1345 cm (1),
563 and 1380 cm (2) and 1586 and 1377 cm (3),
respectively. A difference of 183 to 222 cm between
the two stretching frequencies corresponds to the mon-
odentate binding mode of the carboxylate. The peaks at
−1
−1
1
−1
−1
−1
1
096 and 621 cm (1) and 1077 and 619 cm (2) are
due to the anionic perchlorate. In case of 3, the peaks
−1
at 1121, 1108, 1091 and 623 cm can be attributed to
the anionic and coordinated perchlorates present in it.
3
ual peak of 1.401 e/Å located close to one of the
perchlorate ions has been found to be insignificant
while in those of 2 and 3 there was no significant
3
peaks >1 e/Å . Crystallographic parameters and basic
information pertaining to data collection and struc-
ture refinement for all compounds are summarized in
table 1. All figures were drawn using MERCURY V
Figure 2. A perspective view of the 3D supramolecular
14
3
.0 and hydrogen bonding parameters were generated assembly in 1 (hanging contacts are deleted for clarity).

1
520
Sadhika Khullar and Sanjay K Mandal
Other peaks with a shift by few wave numbers are due 3.3a [Co (bpta) (adc)(H O) ](ClO ) ·2H O (1): It
2
2
2
4
4
2
2
to the bpta ligand which is common in all.
is a dinuclear cobalt(II) complex that crystallizes in the
monoclinic P2 /c space group. There are two indepen-
1
dent molecules in the asymmetric unit. Each hexacoor-
dinated Co(II) center is surrounded by three nitrogens
of the bpta ligand, two coordinated water molecules
3.3 Description of the structures
Single crystals of all three compounds were grown and one oxygen of the adc (figure 1). The carboxylate
by slow evaporation of the solution in a mixture of binds to the Co(II) centers in a bis(monodentate) syn-
methanol and water.
syn fashion which is different from those found in the
Table 3. Hydrogen bonding parameters for 1, 2 and 3.a
◦
D—H...A
r (D-H), Å
r (H...A), Å
r (D...A), Å
<D—H... ( )
Symmetry
1
O3 —H3A...O2
O4 —H4A...O32
O4 —H4B...O21
O7 —H7A...O30
O7 —H7B...O35
O8 —H8A...O2
O8 —H8B...O6
O11 —H11A...O14
O11 —H11B...O38
O12 —H12A...O28
O15 —H15B...O36
O16 —H16A...O35
O35 —H35D...O6
O35 —H35E...O11
O36 —H36E...O25
O38 —H38C...O10
O38 —H38D...O2
C1 —H1A...O18
C1 —H1B...O21
C5 —H5...O19
C16 —H16E...O1
C17 —H17A...O1
C27 —H27A...O17
C28 —H28A...O30
C33 —H33...O8
C36 —H36A...O5
C44 —H44A...O23
C49 —H49...O33
C53 —H53A...O15
C64 —H64A...O23
C64 —H64B...O24A
C68 —H68. . . O33
C72 —H72A...O12
2
0.89
0.87
0.87
0.85
0.85
0.86
0.86
0.87
0.87
0.85
0.86
0.85
0.85
0.85
0.85
0.85
0.85
0.97
0.97
0.93
0.96
0.96
0.97
0.97
0.93
0.96
0.97
0.93
0.96
0.97
0.97
0.93
0.96
1.93
2.36
2.21
2.28
2.21
1.87
1.8
1.89
1.81
2.28
1.94
2.18
1.82
2.26
2.55
1.9
2.646(10)
3.160(19)
3.068(14)
3.086(17)
2.775(8)
2.702(9)
2.596(8)
2.732(7)
2.673(8)
2.932(15)
2.727(10)
2.869(8)
2.668(8)
3.092(7)
3.367(18)
2.681(9)
3.150(10)
3.558(13)
3.105(11)
3.368(12)
3.355(10)
3.359(9)
3.284(13)
3.276(18)
3.098(9)
3.346(11)
3.338(11)
3.29(2)
137
153
168
158
124
163
153
164
174
133
153
138
176
165
162
153
156
172
142
141
147
147
139
130
117
151
139
163
153
145
125
153
150
x,1/2−y,−1/2+z
1−x,1−y,−z
2−x,−1/2+y,1/2−z
1−x,−1/2+y,1/2−z
2−x,−y,−z
1−x,1−y,−z
1−x,−1/2+y,1/2−z
x,1/2−y,−1/2+z
x,1/2−y,−1/2+z
1−x,1/2+y,1/2−z
1−x,1−y,−z
2.36
2.6
2.29
2.6
1−x,1−y,−z
1−x,1−y,−z
2.51
2.51
2.49
2.56
2.56
2.47
2.55
2.39
2.5
2.52
2.55
2.41
2.55
2−x,−1/2+y,1/2−z
2−x,−1/2+y,1/2−z
3.387(11)
3.357(11)
3.21(2)
3.27(3)
3.413(10)
1−x,−1/2+y,1/2−z
1−x,−1/2+y,1/2−z
2−x,−1/2+y,1/2−z
O1 —H1A...O3
O1 —H1B...O6
O1 —H1B...O7
C13—H13...O6
3
O5—H5A. . . O14
O14 —H14D...O15
O16 —H16A...O4
C24 —H24...O6
0.85
0.86
0.86
0.93
1.97
2.35
2.28
2.33
2.750(5)
149
146
163
162
x,−y,−1/2+z
3.112(15)
3.114(10)
3.227(15)
1/2−x,1/2−y,1−z
1/2 +x, 1/2 −y,−1/2+z
−1+x,y,z
0.87
0.85
0.85
0.93
1.91
2.32
2.31
2.51
2.747
162
131
147
152
2.954(10)
3.055(13)
3.362(9)
aValues in parenthesis are estimated standard deviations in the last significant digits.

Supramolecular assemblies of dimetal subunits
1521
16
Mn(II)-adc complex of the same ligand. The Co-O
water
distances vary from 2.073 Å to 2.178 Å whereas
Co-Oadc distances vary from 2.093Å to 2.119Å. All
other selected bond distances and angles are listed in
table 2.
Two discrete dinuclear units are hydrogen bonded
with each other via coordinated and lattice water
molecules to form a supramolecular assembly as shown
in figure 2. All the hydrogen bonding parameters are
listed in table 3. The coordinated water molecule O4
of one discrete dinuclear unit is hydrogen bonded to
the O32 (perchlorate oxygen atom), O8 is hydrogen
bonded to O2 (uncoordinated oxygen atom of adc of
the next same subunit), O8 is intramolecularly hydro-
gen bonded to O6 (uncoordinated oxygen atom of
adc of same subunit), O7 is hydrogen bonded to O35
(lattice water molecule) which is further hydrogen
bonded to O16 (coordinated water molecule on second
subunit) connecting the two subunits. Similar hydro-
gen bonding pattern is found for the second dinuclear
unit. Thus, these two subunits are connected with each
other via a network of hydrogen bonding which can be
clearly seen in figure 3. In another view shown in fig-
ure 4 the two layers formed by hydrogen bonding of two
subunits are arranged in a spiral manner and it forms a
channel in which perchlorate anions are sitting; in other
words, a perchlorate channel is formed between the two
hydrogen bonded units.
Figure 4. A schematic view of the perchlorate channel
between the hydrogen bonded network of two independent
units in 1.
3
.3b [Cu (bpta) (fum)(H O) ](ClO ) (2): It is a
2
2
2
2
4 2
distance is 2.485 Å whereas Cu-Ofum distance is 1.946
Å. In figure 5, the schematic drawing of the dimetal
synthon in 2 shows trans orientation of the coordinated
water molecules that are involved in the formation of
a supramolecular assembly (vide infra). Similar types
of complexes are reported with 1,10-phenanthroline
but with no coordinated water molecule on the Cu(II)
discrete dinuclear Cu(II) complex that crystallizes in
the C2/c space group. Due to the presence of a
2-fold axis, the five coordinated Cu(II) centers are
crystallographically equivalent. The fumarate binds
in a bis(monodentate) syn-anti mode. The Cu-Owater
18
center. The selected bond distances and angles are
listed in table 2.
Due to the trans orientation of the coordinated
water molecules on the Cu(II) centers, O1 (coordinated
Figure 3. Hydrogen bonded network in 1 along the ‘a’
axis.
Figure 5. Structure of the dimetal subunit in 2.

1
522
Sadhika Khullar and Sanjay K Mandal
Figure 6. A ladder-shaped supramolecular assembly in 2 (perchlorates are not included for clarity).
.
3
.3c [Cu (bpta) (tdc)(H O)(ClO )](ClO ) 3H O (3):
2
2
2
4
4
2
The Cu (II) centers in 3 are pentacoordinated and
inequivalent. One Cu(II) center is surrounded by three
nitrogens of the ligand, one coordinated water molecule
and one oxygen of tdc while the other does not have
coordinated water molecule and its fifth site is occu-
pied by the perchlorate oxygen. The tdc binds in a
bis(monodentate) syn-syn mode between the two Cu(II)
centers as shown in figure 7, similar to the ones with
1,10-phenanthroline and imidazole ligands reported in
Figure 7. A view of the dimetal subunit (along with the
free perchlorate ion) in 3.
19–21
the literature.
The selected bond distances and
angles are listed in table 2.
water molecule) is hydrogen bonded to the uncoordi-
The dinuclear subunit forms a polymeric chain struc-
nated oxygen O3 of the fumarate of next dinuclear ture in one direction due to hydrogen bonding of the
unit forming a ladder shaped supramolecular assem- coordinated perchlorate oxygen (O10) with uncoordi-
bly shown in figure 6 (O1. . . O3 distance: 2.750 Å nated oxygen atom of tdc (O2) via a lattice water
◦
and O1-H1A· · · O3 angle: 149 ). The coordinated water molecule (O15) (figure 8), which is further hydrogen
molecule O1 is also hydrogen bonded to one of the per- bonded to another lattice water molecule O14. In the
chlorate anions which is not shown in the figure for next layer, the dinuclear subunits are hydrogen bonded
clarity. All hydrogen bonding parameters are listed in via the third lattice water molecule (O16) and the
table 3.
coordinated water molecule (O5) and uncoordinated
Figure 8. A perspective view of the 3D supramolecular assembly in 3 (hanging contacts are deleted for clarity).

Supramolecular assemblies of dimetal subunits
1523
carboxylate oxygen atom (O4). These alternate layers
are repeated to form the 3D supramolecular assembly
in 3. The hydrogen bonding parameters for 3 are listed
in table 3.
2. Dmitriev A, Lin N, Barth J V and Kern K 2003 Angew.
Chem. Int. Ed. 42 2670
3
. (a) Kitagawa S, Kitaura R and Noro S 2004 Angew.
Chem. Int. Ed. 43 2334; (b) Tranchemontagne D J,
Mendoza-Cortés J L, O’Keeffe M, Yaghi O M 2009
Chem. Soc. Rev. 38 1257; (c) Kurmoo M 2009 Chem.
Soc. Rev. 38 1353; (c) O’Keeffe M, Yaghi O M 2012
Chem. Rev. 112 675; (d) Suh M K, Park H J, Prasad T K
and Lim D-W 2012 Chem. Rev. 112 782; (e) Li J-R,
Sculley J and Zhou H-C 2012 Chem. Rev. 112 869;
4. Conclusion
We have reported structural diversities in the
supramolecular assemblies with varying degrees of
coordinated water molecules per dimetal subunits of
Co(II) or Cu(II) (four for 1, two for 2 and one for 3,
respectively) comprised of a flexible tridentate ligand
and different dicarboxylate linkers. It is clear that these
carboxylates play an important role in determining the
coordination architectures with respect to their size,
conformation and properties. Unlike 1 and 3, there is
no lattice water molecule in 2. However, the role played
by lattice water molecules in 1 and 3 in the construction
of such assemblies is distinctly different. The forma-
tion of a ladder shaped supramolecular assembly in 2
is the result of the trans orientation of the coordinated
water molecules in the dimetal subunit. Based on the
results presented here, further work continues in our
laboratory to understand the effect of the change in the
ancillary ligands and other metal centres.
(
f) Kreno L F, Leong K, Farha O K, Allendorf M, Van
Duyne R P and Hupp J T 2012 Chem. Rev. 112 1105;
g) Cui Y, Yue Y, Qian G and Chen G 2012 Chem. Rev.
12 1126
(
1
4. (a) Desiraju G R 2003 In Crystal Design: Structure and
Functions (Perspectives in Supramolecular Chemistry)
(
England: John Wiley); (b) Desiraju G R, Vittal J J and
Ramanan A 2011 In Crystal Engineering. A Text Book
Singapore: World Scientific)
(
5
. Burrows A D, Chan C W, Chowdhry M M, McGrady
J E and Mingos D M P 1995 Chem. Soc. Rev. 24 329
6. Brammer L 2003 In Perspective in Supramolecular
Chemistry - Crystal Design: Structure and Function
G. R. Desiraju (Ed.) (England: Wiley) Vol. 7, pp 1–75
. Beatty A M 2001 CrystEngComm 3 243
. Aakeroy C B and Beatty A M 2001 Aust. J. Chem. 54
4
9. Desiraju G R 2000 J. Chem. Soc., Dalton Trans. 3745
0. Subramanian S and Zaworotko M J 1994 Coord. Chem.
Rev. 137 357
1. Mok H J, Davis J A, Pal S, Mandal S K and Armstrong
W H 1997 Inorg. Chim. Acta 263 385
2. APEX2, SADABS and SAINT 2008 Bruker AXS inc:
Madison, WI, USA
3. Sheldrick G M 2008 Acta Crystallogr., Sect. A: Found.
7
8
09
1
1
1
1
1
Supplementary Information
Crystallographic data of the structures 1–3 in CIF for-
mat (CCDC 1000552-1000554, respectively). Copies
of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK, (fax: +44-(0)1223-336033 or e-mail:
deposit@ccdc.cam.ac.uk)
Crystallogr. 64 112
4. Macrae C F, Bruno I J, Chisholm J A, Edginton P R,
McCabe P, Pidocck E, Rodriguez-Monge L, Taylor T,
Van de Streek J and Wood P A 2008 J. Appl. Crystallogr.
4
1 266
1
1
5. Spek A L 1999 PLATON, Version 1.62, University of
Utrecht
6. (a) Khullar S and Mandal S K 2012 Cryst. Growth
Des. 12 5329 and references therein; (b) Khullar S and
Mandal S K 2013 Cryst. Growth Des. 13 3116;
Acknowledgements
(
c) Khullar S, Gupta V and Mandal S K 2014 Cryst Eng
Funding for this work was provided by IISER, Mohali.
S. K. is grateful to CSIR, India for research fellowship.
The use of X-ray and NMR facilities at IISER, Mohali,
and CIL, NIPER, Mohali for CHN analysis are grate-
fully acknowledged. We thank one of the referees for
helpful suggestions.
Comm 16 5705
1
7. (a) Skoulika S, Dallas P, Siskos M G, Deligiannakis
Y and Michaelides A 2003 Chem. Mater. 15 4576;
(b) Stein I and Ruschewitz U 2009 Z. Naturforsch., B:
J. Chem. Sci. 64 1093; (c) Wang H-Y, Gao S, Huo L-H
and Zhao J-G 2007 Acta Crystallogr., Sect. E: Struct.
Rep. Online 63 m2995
1
8. Wang Y Y, Wang X, Shi Q Z and Gao Y C 2002 Trans.
Metal Chem. 27 481
References
19. (a) Chen B L Mok K F, Ng S C, Feng Y L and Liu S X
998 Polyhedron 17 4237; (b) Chen B L, Mok K F,
Ng S C and Drew M G B 1999 Polyhedron 18 1211
1
1
. (a) Lehn J-M 1995 In Supramolecular Chemistry: Con-
cepts and Perspectives (New York: VCH); (b) Steed J 20. Xiao H P 2005 Acta Crystallogr. E61 m2592
W, Atwood J L 2009 In Supramolecular Chemistry (UK: 21. Ye s¸ ilel O Z, ˙I lker I, Büyükgüngor O 2009 Polyhedron
John Wiley)
28 3010