Studying fluorous interactions in a series of coordination compounds derived from mono-pyridyl ligands equipped with hydrogen bonding functionality: Exploiting anion...πF interaction in separating ClO 4- anion from a competing mixture of anions

Article abstract of DOI:10.1039/c3ce40359a

A series of coordination compounds (both coordination complexes (CCs) and coordination polymers (CPs)) viz. [Cu(L1)₄·(SO ₄)·(DMSO)]CC1, [(H₂O)₂(DMSO)Cd(L1) ₂(μ₂SO₄)(Cd(L1)₂·(SO ₄)·(DMSO)·(H₂O)] CC2, [Cu(L2) ₂(H₂O)·(Cl)₂] CC3, [Cu(L2) ₂(μ-SO₄)(H₂O)]_∝CP1, [{Cu(L2)₄(μ-SiF₆)}·3H₂O] _∝CP2, [{Cu(L3)₄(ClO₄)}·ClO ₄·H₂O]·CC4, [{Cu(L3)₄(H ₂O)}·H₂O·2BF₄] CC5, [{(Cl)Cu(L3)₄(μ-Cl)Cu(L3)₄}·Cl·H ₂O] CC6, [{Cu₂(L3)₄(μ-Cl) ₂·(Cl)₂}·H₂O] CC7, [Cu(L3) ₂(Cl)₂] CC8, and [{Cu(L4)₄·(H ₂O)₂}·SO₄·5H₂O] CC9 derived from ligands equipped with pyridyl and pentafluorophenyl/phenyl moieties along with hydrogen bonding backbone (amide/urea) with Cu^II/Cd ^II metal centers have been synthesized and characterized by single crystal X-ray diffraction (SXRD). Their various fluorous interactions along with hydrogen bonding have been investigated. The results show that almost all the coordination compounds except CC9 studied herein display various fluorous interactions; in one such example i.e. in CC4, anion-π_F along with other supramolecular interactions (F...F, C-H...F) shapes the supramolecular assembly, which is exploited to separate environmentally relevant perchlorate anion from a competing mixture of anions viz. SO₄ ^2-, NO₃^-, ClO₄^-, BF ₄^-, Cl^- by following in situ synthesis of the corresponding coordination compound.

Full text of DOI:10.1039/c3ce40359a

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PAPER
Studying fluorous interactions in a series of
coordination compounds derived from mono-pyridyl
ligands equipped with hydrogen bonding functionality:
exploiting anion⋯πF interaction in separating ClO4
anion from a competing mixture of anions†
Cite this: CrystEngComm, 2013, 15,
9415
−
*
Subhabrata Banerjee and Parthasarathi Dastidar
A series of coordination compounds (both coordination complexes (CCs) and coordination polymers (CPs)) viz.
[Cu(L1)4·(SO4)·(DMSO)]CC1, [(H2O)2(DMSO)Cd(L1)2(μ2SO4)(Cd(L1)2·(SO4)·(DMSO)·(H2O)] CC2, [Cu(L2)2(H2O)·(Cl)2]
CC3, [Cu(L2)2(μ-SO4)(H2O)]∝ CP1, [{Cu(L2)4(μ-SiF6)}·3H2O]∝ CP2, [{Cu(L3)4(ClO4)}·ClO4·H2O]·CC4, [{Cu(L3)4(H2O)}·H2O·2BF4]
CC5, [{(Cl)Cu(L3)4(μ-Cl)Cu(L3)4}·Cl·H2O] CC6, [{Cu2(L3)4(μ-Cl)2·(Cl)2}·H2O] CC7, [Cu(L3)2(Cl)2] CC8, and
[{Cu(L4)4·(H2O)2}·SO4·5H2O] CC9 derived from ligands equipped with pyridyl and pentafluorophenyl/phenyl
moieties along with hydrogen bonding backbone (amide/urea) with CuII/CdII metal centers have been
synthesized and characterized by single crystal X-ray diffraction (SXRD). Their various fluorous interactions along
with hydrogen bonding have been investigated. The results show that almost all the coordination compounds
except CC9 studied herein display various fluorous interactions; in one such example i.e. in CC4, anion–πF
Received 27th February 2013,
Accepted 11th April 2013
along with other supramolecular interactions (F⋯F, C–H⋯F) shapes the supramolecular assembly, which is
exploited to separate environmentally relevant perchlorate anion from a competing mixture of anions viz. SO4
NO3−, ClO4−, BF4−, Cl− by following in situ synthesis of the corresponding coordination compound.
DOI: 10.1039/c3ce40359a
2−
,
www.rsc.org/crystengcomm
Introduction
Research in this area received thrust with the early discovery
of phenyl–perfluorophenyl stacking interactions in benzene–
hexaflurobenzene complex,3a later a crystal structure of
the benzene-d6-hexaflurobenzene complex has also been
reported.3b Since then a lot of effort has been made to exploit
these weak interactions in crystal engineering.4–6 Phenyl–
perfluorophenyl stacking interaction has been exploited in
carrying out topochemical [2+2] photodimerization and
photopolymerization of olefinic compounds.7 Gdaniec et al.
have shown that phenyl–perfluorophenyl interaction plays an
important role in self-assembling hydrogen bonded carbox-
ylic acid dimers.8 Weak interaction (20–50 kJ mol−1) involving
anion and electron deficient aromatics (anion–π) is one of
the non-covalent interactions currently being studied with
vigor in supramolecular chemistry.9 Various studies indicate
that such weak interaction offers a new avenue for the design
of neutral anion receptors.10 Anion–π interaction has been
successfully implemented in developing synthetic ion-
channel that displays remarkable anion selectivity.11 Anion–π
interaction is also shown to display strong synergistic effect
along with cation–π and π–π interactions.12
Organic fluoro compounds are an important class of com-
pounds that are beneficial to chemistry in general and mate-
rials science in particular. This class of compounds possesses
low polarity and high thermal stability because of the
remarkable C–F bond strength. The molecular self-assembly
of fluoro compounds are mainly governed by the weak inter-
actions such as π–πF, C–H⋯F, C–F⋯πF, F⋯F, C–F⋯CO,
C–F⋯M+, anion⋯πF etc.1 Such properties have been exploited
in catalysis,2a liquid crystals,2b solid-state photoreactions,2c
inclusion materials,2d chirality,2e molecular recognition and
sensing,2f organic electronics,2g alternative energy,2h and
biomedical applications.2i Among the various organic fluoro
compounds, perfluoro aromatic units play an important
role in designing intriguing supramolecular assemblies.
Department of Organic Chemistry, Indian Association for the Cultivation of Science,
2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India.
E-mail: ocpd@iacs.res.in, parthod123@rediffmail.com
† Electronic supplementary information (ESI) available: ORTEP diagram,
hydrogen bonding parameter, PXRD patterns and TGA Plots of the compounds.
CCDC 926124–926134. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c3ce40359a
As a part of our ongoing research endeavour to develop
intriguing coordination compounds13 displaying remarkable
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structure and properties (anion separation, metallogelation
etc.), we have been investigating pyridyl based ligands
equipped with hydrogen bonding backbone. To study
the effect of both anion–π and hydrogen bonding on
the resultant supramolecular structures of coordination
compounds, we synthesized three new ligands, namely
N-(3-pyridyl),N′-(pentafluorophenyl) urea (L1),14a N-(3-picolyl)-
pentafluorobenzamide (L2) and N-(4-pyridyl)-pentafluorobenzamide
(L3), equipped with both perfluorophenyl moiety and hydro-
gen bonding backbone; we also synthesized the non-
fluorous analogue of L1 i.e. N-(3-pyridinyl)-N′-phenyl-urea
(L4) in order to compare the corresponding structure of the
coordination compound with that obtained from L1. These
ligands were reacted with various transition metal (CuII, CdII)
salts to produce as many as 11 new coordination com-
pounds namely, [Cu(L1)4·(SO4)·(DMSO)]CC1, [(H2O)2(DMSO)Cd
(L1)2(μ2SO4)(Cd(L1)2·(SO4)·(DMSO)·(H2O)] CC2, [Cu(L2)2(H2O)·(Cl)2]
CC3, [Cu(L2)2(μ-SO4)(H2O)]∝ CP1, [{Cu(L2)4(μ-SiF6)}·3H2O]∝ CP2,
[{Cu(L3)4(ClO4)}·ClO4·H2O] CC4, [{Cu(L3)4(H2O)}·H2O.2BF4] CC5,
[{(Cl)Cu(L3)4(μ-Cl)Cu(L3)4}·Cl·H2O] CC6, [{Cu2(L3)4(μ-Cl)2·(Cl)2}·H2O]
CC7, [Cu(L3)2(Cl)2] CC8, [{Cu(L4)4·(H2O)2}·SO4·5H2O] CC9.
Single crystal structures of these coordination compounds
were studied in detail in order to understand various weak
noncovalent interactions involving perfluorophenyl ring,
hydrogen bonding functionality and various anions. It may
be important to mention that CSD searches with
perfluorophenyl moiety, any transition metal and amide/
urea functionality as search fragments resulted in 33 and 11
hits, respectively.14b It was demonstrated that L3 was capable
−
of separating ClO4 from a complex mixture of anions (Cl−,
−
−
−
SO42−, BF4 , NO3 , ClO4 ) in the form of a crystalline CuII
coordination complex.
Results and discussions
Thus, we reacted L1, L2, L3, L4 (Scheme 1) with various CuII
and CdII salts in 1 : 0.5 (ligand : metal salt) molar ratio in
Scheme 1
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distorted octahedral geometry wherein the equatorial posi-
tions were coordinated by the four ligand molecules and the
apical centers were occupied by sulfate anion and DMSO
(both disordered) molecules. The crystallographically inde-
pendent molecules in the asymmetric unit were held together
by πF–πF (∼4.089 Å) and C–F⋯πF (∼3.070 Å) interactions. The
ligand molecules display highly non-planer conformation
(dihedral angles: central urea moiety–terminal pyridyl units =
8.6–14.3°, central urea moiety–pentafluoro rings = 64.0–70.8°,
pentafluoro rings–terminal pyridyl rings = 74.2–81.5°). The
urea moiety was found to be involved in hydrogen bonding
interactions with the disordered sulfate anion of the adjacent
coordination complex [N⋯O = 2.784(17)–3.34(3) Å; ∠N–H⋯O =
137.0–177.5°] resulting in a two dimensional hydrogen bonded
network. Intermolecular F⋯F (2.723(13)–2.997(12) Å) and
C–F⋯π (∼3.063 Å) interactions were also observed within
the crystal lattice (Fig. 1).
Crystal structure of [(H2O)2(DMSO)Cd(L1)2
(μ2-SO4)(Cd(L1)2·(SO4)·(DMSO)·(H2O)](CC2)
Reaction of L1 with CdSO4 in aqueous DMSO/acetonitrile
mixture resulted in X-ray quality crystals (colourless, block
shaped) of CC2. SXRD data revealed that the compound crys-
Fig.
1
a) Two crystallographically independent molecular complex in the
asymmetric unit and b) 2D hydrogen bonded network in CC1.
¯
tallized in the centrosymmetric triclinic space group P1. The
asymmetric unit contained a bi-metallic CdII coordination
complex which was formed by sulfate bridging; each metal
center displayed slightly distorted octahedral geometry. The
equatorial positions of the metal centers were coordinated
the O atoms of sulfate, DMSO and water molecules whereas
the axial positions were occupied by the pyridyl N atoms.
Some disordered solvent molecules which could not be iden-
tified from difference Fourier map were removed by applying
SQUEEZE.14c The ligands displayed highly non-planar confor-
mation (dihedral angles: central urea moiety–terminal pyridyl
units = 4.07–11.90°, central urea moiety–pentafluoro rings =
56.0–59.86°, pentafluoro rings–terminal pyridyl rings = 55.5–
66.4°). The bi-metallic coordination complex molecules were
further assembled into a 2D hydrogen bonded network
sustained by intermolecular urea–sulfate hydrogen bonding
[N⋯O = 2.800 (7)–3.243(8) Å; ∠N–H⋯O = 141.8–170.7°]. The
2D networks were further packed in parallel fashion sustained
separate trials. These resulted in a series of coordination
polymers (CPs) and coordination complexes (CCs) depending
on counteranion used. Suitably grown single crystals of the
CPs and CCs were then subjected to SXRD experiments (see
Table 1). It may be mentioned here that all the crystals were
of relatively poor X-ray quality and our continuous efforts to
grow better X-ray quality crystals proved unsuccessful.
Crystal structure of [Cu(L1)4·(SO4)·(DMSO)] (CC1)
Reaction of L1 with CuSO4 in aqueous DMSO/acetonitrile
mixture resulted in X-ray quality crystals (blue, block shaped)
of CC1. SXRD data revealed that the compound crystallized
¯
in the centrosymmetric triclinic space group P1. The asym-
metric unit contained two coordination complex molecules of
CC1 – each having a CuII metal center displaying slightly
Fig. 2 a) Discrete molecular complex and b) interdigited packing of the 2D network in CC2.
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pentafluoro rings = 55.2°, pentafluoro rings–terminal pyridyl
rings = 37.1°). The coordination complex self-assembled into
1D hydrogen bonded network sustained by N–H⋯O interactions
[N⋯O = 2.9 (13) Å; ∠N–H⋯O = 146.7°] involving the amide
functionality. The 1D networks were further self-assembled into
a 2D network via O–H⋯Cl interactions [O⋯Cl = 3.072(6) Å].
F⋯F short contacts (2.675(19)–2.960(18) Å) were also observed
between the adjacent 2D networks (Fig. 3).
Crystal structure of [Cu(L2)2(μ-SO4)(H2O)]∝ (CP1)
Reaction of L2 with CuSO4 in aqueous ethanol/methanol mix-
ture resulted in X-ray quality crystals (blue, plate shaped) of
CP1. The compound CP1 crystallized in the centrosymmetric
monoclinic space group P21/m. The asymmetric unit was com-
prised of a fully occupied metal bound ligand, a half occupied
CuII, a half occupied water molecule and half a molecule of
counteranion sulfate – all the partially occupied species were
residing on a mirror plane. The ligand displayed non-planar
conformation (dihedral angles: central amide moiety–terminal
pyridyl units = 62.2°, central amide moiety–pentafluoro rings =
55.0°, pentafluoro rings–terminal pyridyl rings = 41.3°). The
metal center displayed distorted square pyramidal geometry
wherein the equatorial sites were occupied by N and O atoms
of the pyridyl ligand, a counteranion sulfate and a water mole-
cule, and the axial position was coordinated by the O atoms of
a bridging sulfate. Classical amide–amide intra-polymeric
Fig. 3 a) Unidirectional propagation of molecular complex via H bonding and
b) overall 2D propagation of 1D hydrogen bonded network sustained F⋯F
interactions in CC3.
by inter-layer F⋯F (2.915(8)–2.937(9) Å) and πF–πF (3.838 Å)
interactions (Fig. 2).
Crystal structure of [Cu(L2)2(H2O)·(Cl)2] CC3
Reaction of L2 with CuCl2 in aqueous ethanol/methanol mix-
ture resulted in X-ray quality crystals (blue, needle shaped) of
CC3. The compound CC3 crystallized in the centrosymmetric
monoclinic space group C2/c. The crystal was thin and poorly
diffracting, which resulted a low quality data set which was
reflected in its high R factor (11.41%). The asymmetric unit
was comprised of half occupied CuII and a water molecule
(coordinated to the metal center) – both sitting on a 2-fold axis,
one fully occupied ligand and one chloride ion – both coordi-
nated to the metal center, which displayed a highly distorted
square pyramidal geometry wherein the equatorial positions
were occupied by N and Cl and the axial position was coordi-
nated by the water molecule. The ligand displayed a highly
nonplanar conformation (dihedral angles: central amide
moiety–terminal pyridyl units = 85.9°, central amide moiety–
hydrogen bonding was observed [N⋯O
= 2.874 (9) Å;
∠N–H⋯O = 178.2°]. The 1D chains were further packed in
parallel fashion into 2D sheet sustained by O–H⋯O [O⋯O =
2.735–2.838 Å] interactions involving metal bound water and
sulfate O atoms of the adjacent chains. Short contact interactions
like CO⋯πF (3.191 Å) were observed in this structure (Fig. 4).
Crystal structure of [{Cu(L2)4(μ-SiF6)}·3H2O]∝ (CP2)
Reaction of L2 with Cu(BF4)2 in aqueous ethanol/methanol
mixture resulted in X-ray quality crystals (blue, plate shaped)
2−
of CP2. SXRD analysis established the existence of SiF6
−
instead of BF4 as counteranion; it was known in the literature
Fig. 4 a) 1D coordination polymer displaying classical amide⋯amide hydrogen bonding and b) parallel packing of the 1D coordination polymeric chains sustained via
O–H⋯O interactions in CP1.
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Fig. 5 Parallel packing of 1D coordination polymeric chains sustained via F⋯F interactions in CP2.
−
that such occurrence happened due to the reaction of BF4
anion with SiO2 component of a reaction glass vessel.14d The
compound CP2 crystallized in the centrosymmetric monoclinic
space group C2/c. The asymmetric unit was comprised of one
CuII metal center, one metal coordinated SiF62− – both residing
on a 2-fold axis, two fully occupied ligands coordinated to the
metal center and three lattice occluded water molecules.
Unidentified solvent molecules that could not be identifed
from difference Fourier map were removed by applying
SQUEEZE.14c The ligand displayed highly non-planar confor-
mation (dihedral angles: central amide moiety–terminal
pyridyl units = 87.6–76.7°, central amide moiety–pentafluoro
rings = 57.4–48.4°, pentafluoro rings–terminal pyridyl rings =
72.9–30.9°). The metal center displayed slightly octahedral
geometry wherein the equatorial positions were occupied by
pyridyl N atoms and the apical positions were coordinated by
Inter-chain F⋯F (2.891 Å), C–F⋯πF (3.116 Å) interactions were
also observed (Fig. 5).
[{Cu(L3)4(ClO4)}·ClO4·H2O] CC4
Reaction of L3 with Cu(ClO4)2 in aqueous ethanol/methanol
mixture resulted in X-ray quality crystals (blue, plate shaped)
of CC4. The compound CC4 crystallized in the tetragonal
space group P4/ncc. In the asymmetric unit the metal center
CuII (residing on a 4-fold symmetry) was coordinated by a
−
fully occupied ligand and a ClO4 counteranion disordered
over a 4-fold axis; a non-coordinated highly disordered count-
−
eranion ClO4 and a water molecule – both located on a
4-fold axis – were also present. The metal center displayed
distorted square pyramidal geometry. The ligand displayed a
highly non-planar conformation (dihedral angles: central
amide moiety–terminal pyridyl units = 17.71°, central amide
moiety–pentafluoro rings = 78.62°, pentafluoro rings–terminal
pyridyl rings = 84.35°). However, the coordinated counteranion
2−
F atoms coming from the bridging SiF6 resulting in a 1D
coordination polymer. The 1D chains were packed in parallel
fashion and the lattice occluded water molecules were tightly
held in the crystal structure via O–H⋯O [O⋯O = 2.818(14)–
2.886(12) Å] and N–H⋯O [N⋯O = 2.768(13)–2.852(12) Å; ∠N–
H⋯O = 158.2–165.4°] interactions involving the amide moiety.
ClO4− was found to display anion–π interactions with pentafluoro-
−
phenyl ring (dClO oxygen–pentafluoro ring centroid ∼ 3.490 Å,
4
∠Opentafluoro
centroid–Cpentafluoro
∼
96.14°). In the
ring
ring
Fig. 6 a) anion–π interaction between anion and pentafluoro ring and b) overall packing diagram viewed along c axis in CC4.
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Fig. 7 a) Anion–π interaction between BF4− and pentafluoro ring and b) lattice occluded water mediated hydrogen bonded dimers in CC5.
complex, appreciable F⋯F contact (2.806 Å) and C–H⋯F
interactions (C⋯F = 3.243 Å, ∠C–H⋯F = 137°) were also
observed (Fig. 6).
complex (O⋯O = 2.689(11)–2.858(12) Å). Fluorine atoms of
−
BF4 anion were involved in various hydrogen bonding [N⋯F
= 2.751(14)–2.887(14) Å; ∠N–H⋯F = 151.1–172.2°] with the
−
amide moiety. The counteranion BF4 were found to display
[{Cu(L3)4(H2O)}·H2O·2BF4] (CC5)
anion–π interactions with the adjacent pentafluorophenyl rings
Reaction of L3 with Cu(BF4)2 in aqueous ethanol/methanol
mixture resulted in X-ray quality crystals (blue, block shaped)
of CC5. The compound CC5 crystallized in the monoclinic
space group P21/c. The asymmetric unit contained four
(dtetrafluoroborate
∠Ftetrafluoroborate–pentafluoro
99.03°). Various other fluorous short contacts such as F⋯F
[∼2.883(19), 2.901(14) Å], C–F⋯π.(∼3.166 Å), C–F⋯πF (∼3.097 Å)
were observed within the crystal lattice (Fig. 7).
∼ 2.963–3.426 Å,
fluorine–pentafluoro ring centroid
centroid–Cpentafluoro
∼ 98.13–
ring
ring
−
ligands, one metal center (CuII), two BF4 anion and one water
molecule. The ligand displayed a highly non-planar conforma-
tion (dihedral angle: pentafluoro–phenyl ring = 62.40–85.17°,
the dihedral angle between amide plane–phenyl ring = 76.72–
87.60°, the corresponding angle with amide plane–pentafluoro
ring = 57.40–74.1°). Interestingly, the amide functionality did
not display any classical amide⋯amide hydrogen bonding;
instead, it was found to be involve in hydrogen bonding with
the lattice occluded solvent molecules, which in turn were
interacting with the metal bound water resulting in solvate
mediated hydrogen bonded dimer of the coordination
Interestingly when L3 was reacted with CuCl2 in aqueous
ethanol/methanol mixture, it gave three different coordina-
tion compounds namely [{(Cl)Cu(L3)4(μ-Cl)Cu(L3)4}·Cl·H2O]
CC6, [{Cu2(L3)4(μ-Cl)2·(Cl)2}·H2O] CC7 and [Cu(L3)2(Cl)2]
(CC8) under different temperatures; while CC6 was formed in
a crystallization room equipped with air conditioning that
maintained a constant temperature of 22 °C round the clock,
CC7 and CC8 were grown concomitantly during summer
when the room temperature was ∼30–40 °C with occasional
formation of CC7 alone in a few batches (Scheme 2).
Scheme 2
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Fig. 8 a) Discrete molecular complex and b) 2D propagation of the supramolecular
assembly along the a–b plane sustained by N–H⋯O and N–H⋯Cl interactions.
Fig. 9 1D propagation of the supramolecular assembly via O–H⋯O and N–H⋯Cl
hydrogen bonding in CC7.
[{(Cl)Cu(L3)4(μ-Cl)Cu(L3)4}·Cl·H2O] CC6
The block shaped blue crystals of CC6 crystallized in the
tetragonal space group P4/n. The asymmetric unit contained
two metal centers, two coordinated chloride – all resided on
a 4-fold axis, two ligands both coordinated to each metal cen-
ter, one uncoordinated chloride seated on a glide plane and
a solvate water molecule. The complex CC6 can be best
described as a bimetallic coordination complex wherein the
metal centers were bridged by chloride; while one of the CuII
centers displayed perfect octahedral geometry, the other one
showed slightly distorted square pyramidal geometry. Some
disordered solvent molecules which could not be identified
from difference Fourier map were removed by applying
SQUEEZE.14c The equatorial positions in both metal centers
were occupied by pyridyl N atoms and the apical positions
were coordinated by chloride on both the metal centers. The
ligand displayed highly non-planar conformation (the dihe-
dral angles: pentafluoro–phenyl ring = 73.03–73.19°, amide
plane–phenyl ring = 46.21°–57.80°, amide plane–pentafluoro
ring = 28.43–28.11°). The complex was found to propagate
through the a–b plane via hydrogen bonding involving amide
N–H moiety and a solvate water molecule as well as a non-
coordinated chloride anion [N⋯O = 2.745(8), ∠N–H⋯O =
166.5°; N⋯Cl = 3.050(7) Å, ∠N–H⋯Cl = 165.3°]. Supramolec-
ular assembly was governed by various fluorous interactions
viz. F⋯F short contact (2.939(7)–2.955(7) Å), weak C–H⋯F
interaction (C⋯F = 3.184 Å, ∠C–H⋯F = 135°) and πF–πF
stacking interaction (∼4.00 Å). Interestingly, orthogonal C–
F⋯CO interaction (2.904 Å) was observed in this complex,
which is not so common in the literature (Fig. 8).1
the pyridyl N and chloride whereas the apical positions in
each metal center were coordinated by chloride. The ligand
displayed a highly non-planar conformation (dihedral angles:
central amide moiety–terminal pyridyl units = 11.89°–22.54°,
central amide moiety–pentafluoro rings
= 58.79°–76.61°,
pentafluoro rings–terminal pyridyl rings = 39.43°–58.67°). The
amide moiety did not display classical amide⋯amide hydro-
gen bonding; instead, it was involved in hydrogen bonding
interactions with both the metal bound chloride and solvate
water molecule resulting into 1D network [N⋯Cl = 3.174(4)–
3.272(4) Å ; ∠N–H⋯Cl = 159.6–168.8°, N⋯O = 2.913 (5) Å ;
∠N–H⋯O
=
172.9°, O⋯O
= 2.844(6)]; in this complex
various fluorous contacts viz. F⋯F short contact (∼2.822 Å),
a rarely observed1 C–F⋯CO interaction (2.911 Å), and
C–F⋯π interactions (∼3.054 Å) were observed (Fig. 9).
[Cu(L3)2(Cl)2] (CC8)
The deep blue needle shaped crystals of CC8 crystallized in
the monoclinic centrosymmetric space group P21/c. The
asymmetric unit contained one half occupied CuII metal cen-
ter located on a center of symmetry, a ligand and a chloride –
both coordinated to the metal center. It is a slightly distorted
square planar complex wherein the metal center was coordi-
nated by two ligands and two chloride ions in a trans fash-
ion. The ligand displayed highly non-planar conformation
(dihedral angles: central amide moiety–terminal pyridyl
units = 9.47°, central amide moiety–pentafluoro rings =
56.04°, pentafluoro rings–terminal pyridyl rings = 49.29°).
In the crystal structure, the molecules were held together
by N–H⋯Cl interactions [N⋯Cl = 3.287 (4) Å; ∠N–H⋯Cl =
152.4°] leading to the formation of a 2D network. Several
fluorous short contacts such as F⋯F (2.710(8)–2.873(7) Å),
C–F⋯π (3.137 Å), C–H⋯F (C⋯F = 3.227(7), ∠C–H⋯F =
138° were also observed (Fig. 10).
[{Cu2(L3)4(μ-Cl)2·(Cl)2}·H2O] CC7
The sky-blue plate shaped crystals of CC7 crystallized in the
monoclinic space group P21/c. The crystal was thin and
poorly diffracting, which resulted low quality data. The asym-
metric unit contained four fully occupied ligands, two metal
atoms, one solvate water molecule and four coordinated chlo-
rides. It is a bimetallic complex wherein two crystallographi-
cally independent chlorides acted as bridges to coordinate
the adjacent metal centers. Both the metal centers displayed
slightly distorted square pyramidal geometry wherein the
equatorial positions on each metal center were occupied by
[{Cu(L4)4·(H2O)2}·SO4·5H2O] (CC9)
Reaction of L4 with CuSO4 in aqueous ethanol/methanol mix-
ture resulted in X-ray quality crystals (blue, block shaped) of
CC9. The compound CC9 crystallized in the tetragonal space
group P4/n. The asymmetric unit was comprised of one CuII
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Fig. 11 a) Discrete molecular complex and b) its propagation in 3D sustained by
O–H⋯O and N–H⋯O hydrogen bonding interactions in CC9.
anion–π interaction with the pentafluoro ring; one of the
−
counteranions (ClO4 ) in CC4 is also coordinated to the metal
center. We have taken cue from this observation and tried to
exploit it in selective separation of ClO4− via in situ crystalliza-
−
tion. It may be noted that the hydration energies of ClO4
−
and BF4 are significantly different (ΔhydG*, −430 kJ mol−1;
Fig. 10 a) Discrete molecular complex and b) its propagation in 2D sustained by
N–H⋯Cl hydrogen bonding in CC8.
ΔhydG*, −190 kJ mol−1)17 and it would normally be difficult to
−
−
get selectivity towards ClO4 over BF4 as it would have to
overcome Hofmeister bias.18 Considering significant differ-
ences in the supramolecular environment of the respective
metal center, two coordinated water molecules – all located
on a 4-fold axis, one fully occupied ligand coordinated to the
metal center, one solvate water molecule located a glide
−
−
anions (ClO4 and BF4 ) in CC4 and CC5 as discussed above,
−
we tried to separate ClO4 from a complex mixture of aque-
2−
plane and disordered around
a
center of symmetry,
ous solution containing competing anions namely SO4
,
−
−
an uncoordinated counteranion sulfate seating on a 4-fold
rotation–inversion axis and a solvate water molecule disordered
over two positions. It is a coordination complex wherein the
metal center displayed a perfect octahedral geometry; the equa-
torial positions were occupied by the pyridyl N atoms whereas
the apical positions were coordinated by the water molecules.
The ligand displayed a non-planar conformation (dihedral
angles: central urea moiety–terminal pyridyl units = 30.08°,
15.43°; terminal pyridyl rings = 20.43°). The uncoordinated
sulfate counteranion was found to be involved in extensive
hydrogen bonding with the urea functionalities of the
neighbouring metal complexes; all four O atoms of the sulfate
was found to be involving in N–H⋯O interactions with
the urea moieties [N⋯O = 2.836(7)–2.981 (6) Å; ∠N–H⋯O =
152.4–167.9°]. Further hydrogen bonding interactions involving
the metal bound water, lattice occluded water and urea
carbonyl O atom lead to the formation of an overall 3D
network. Weak interactions such as C–H⋯π (3.66 Å) were also
present. However, π–π interactions, as observed in its fluorous
analogue (CC1), were not observed in this structure (Fig. 11).
NO3−, ClO4 , BF4 , Cl−. For this purpose, we have carried out
two sets of experiments under two different conditions (con-
dition I and II). In condition I, L3 was reacted with a mixture
of CuSO4, Cu(NO3)2, Cu(ClO4)2, Cu(BF4)2, and CuCl2 in aque-
ous ethanol/methanol (metal : ligand = 1 : 2). In condition II,
all the metal salts except Cu(ClO4)2 were taken in twice the
amount used in condition I. FT-IR, PXRD, elemental analysis
and EDX data (Fig. 12 and 13) clearly indicated that the
−
anion ClO4 was separated out exclusively as crystalline CC4
in each case. Thus it is apparent that the synergistic effect of
both anion–metal coordination and anion–π interactions in
the crystal structure of CC4 play a crucial role in selective
−
separation of ClO4 (Scheme 3).
Conclusion
In this present work a series of coordination compounds viz.
CC1–CC8, CP1 and CP2 derived from monopyridyl ligands
equipped with hydrogen bonding functionality (urea/amide)
and perfluoro moiety have been synthesized and the corre-
sponding single crystal structures were determined in order
to study the various fluorous interactions such as π–πF, πF–πF,
C–F⋯H, C–F⋯πF, F⋯F, C–F⋯CO, C–F⋯M+, anion⋯πF
present in the crystal structures. Except C–F⋯M+, all the
other fluorous interactions were present in these structures.
In CC1 intermolecular F⋯F and C–F⋯π interactions were
observed; in CC2 inter-layer F⋯F and πF–πF interactions were
evident; in CC3 only F⋯F short contacts were present; in
CP1, CO⋯πF could be seen; in CP2 inter-chain F⋯F and
C–F⋯πF were the main fluorous interactions. In CC4
Anion separation
Anion separation and anion binding is important in the con-
−
text of environmental cleanup.15 Perchlorate (ClO4 ) anion is
an important environmental contaminant that causes various
health hazards. It can halt the production of thyroid hor-
−
mone.16 Therefore selective removal of ClO4 is important.
From the crystal structures of CC4 and CC5 (vide supra), it is
evident that the counteranion in both the structures display
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Fig. 12 PXRD patterns, FT-IR spectra, and elemental analysis data in various conditions of ClO4− separation for CC4.
Fig. 13 EDX data for condition I (a) and condition II (b) showing presence of chlorine in both conditions.
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Scheme 3
anion–πF interactions along with pentafluorophenyl ring
F⋯F contacts and C–H⋯F interactions were prominent. In
CC5 along with anion–πF and F⋯F short contacts, C–F⋯π
and C–F⋯πF were noticed; CC6 contained F⋯F short con-
tacts, weak C–H⋯F interactions, πF–πF stacking interactions,
rarely observed C–F⋯CO interaction. In CC7, F⋯F short
contacts, C–F⋯CO interactions and C–F⋯π interactions,
and lastly in CC8 short contacts like F⋯F, C–F⋯π and
C–H⋯F were present. It is interesting to note that in the
nonfluorous analogue of CC1 i.e. CC9, no π–π interactions were
observed whereas in CC1, πF–πF interaction was present. In the
case of CC4, the anion⋯πF interaction has been exploited
to separate perchlorate (ClO42−−) from a competing mixture
b) In the next step nicotinoyl azide (1.00 g, 6.75 mmol)
was dissolved in dry toluene (50 mL) and stirred at reflux for
2 h when no more N2 was evolved. The solution was cooled
to room temperature, then 2,3,4,5,6-pentafluoroaniline (1.1 g,
6.01 mmol) in toluene (10 ml) was added dropwise through
an addition funnel and
a colorless precipitation was
obtained. The suspension was stirred for 15 min at room
temperature. The entire mass was evaporated, the white mass
was purified through column chromatography, 60–120 mesh
silica and 4% methanol/chloroform as eluent.
Analytical data: (yield: 450 mg, 24.7%) m.p.: 196 °C.
Elemental analysis calcd for C12H6 F5 N3O (%): C 47.54, H
1.99, N 13.86. Found: C 48.04, H 2.01, N 13.54. 1H NMR
(500 MHz, [D6] DMSO): δ = 9.286 (s, 1H, N–H), 8.67 (s, 1H,
N–H), 8.613–8.616 (d, J = 1.5 Hz 1H, Py–H), 8.220–8.211
(d, J = 4.5 Hz, 1H, Py–H), 7.922–7.906 (d, J = 8 Hz, 1H, Py–H),
7.334–7.308 (dd, J = 4.5, 1 Hz, 1H, Py–H), IR (KBr pellet):
3294 (s, N–H stretch), 3259 (m, aromatic C–H stretch),
3134w, 3101w, 2899m, 2827w, 1680 (s, urea CO stretch),
1653s, 1600s, 1548 (s, amide N–H bend), 1525s, 1489s,
1410w, 1329s, 1288s, 1226s, 1193m, 1062s, 1041s, 1003s,
979s, 802s, 705s cm−1. HRMS ESI (CH3OH): m/z (%):
304 [(PyNHCONHC6F5)]+, 121, 301.
of anions viz. SO42−, NO3 , ClO4 , BF4 , Cl−.
−
−
Experimental section
Materials and method
All chemicals were commercially available and used without
further purification. The elemental analysis was carried out
using a Perkin-Elmer 2400 Series-II CHN analyzer. FT-IR spec-
tra were recorded using Perkin-Elmer Spectrum GX, and TGA
analyses were performed on a SDT Q Series 600 Universal
VA.2E TA instrument. Powder X-ray patterns were recorded
on a Bruker AXS D8 Advance Powder (Cu Kα1 radiation, λ =
1.5406 Å) Diffractometer. The mass spectrum was recorded
on QTOF Micro YA263. NMR spectra were recorded using
300 MHz Bruker Avance DPX300 spectrometer.
Synthesis of L2 (N-(3-picolyl)-pentafluorobenzamide)
Synthetic procedure: 2,3,4,5,6-pentafluorobenzoyl chloride
(1.00 g, 4.34 mmol) was taken in a 250 ml RB flask in 80 ml
DCM, 3-picolylamine (0.47 g, 4.34 mmol) in 30 ml DCM was
dropwise added to this solution at 0 °C and the mixture was
then allowed to stir for 12 hours at room temperature. Then
the resulting solution was evaporated, a white mass was
obtained and recrystallized in methanol–water mixture. Yield:
65% (0.85 g, 2.8 mmol).
Synthesis of L1 (N-(3-pyridyl), N′-(pentafluorophenyl) urea)
Synthetic procedure: the synthesis of ligand includes
two steps a) and b).
a) This step includes synthesis of nicotinoyl azide which is
done according to ref. 19.
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Analytical data: m.p.: 118 °C. Elemental analysis calcd for
CrystEngComm
analysis calcd for C52H36Cd2F20N12O17S4 (%): C 44.06, H, 1.98,
N 9.16. Found: C, 33.95; H, 2.51; N, 9.41. FT-IR (KBr pellet):
3342s, 3304m, 3080w, 2294m, 1722s (s, urea CO stretch),
1595 (s, urea N–H bend), 1570s, 1546s, 1525s, 1496s, 1479s,
1427s, 1334s, 1280s, 1205 (s, bridge sulfate asymmetric S–O
stretching), 1190m, 1066s, 1020 (s, unidentate asymmetric S–O
stretching), 970s, 923w, 864s, 808m, 748m, 707s, 630m, 574w,
547s 513s cm−1.
[Cu(L2)2(H2O)·(Cl)2] CC3. Coordination complex CC3 was
synthesized by layering a methanolic toluene solution of CuCl2
(13.5 mg, 0.049 mmol) over a methanolic solution of L2
(30 mg, 0.097 mmol). After two weeks sky blue needle shape
X-ray quality crystals were obtained. Yield: 58% (22 mg,
0.029 mmol). Elemental analysis calcd for C26H14Cl2CuF10N4O3
(%): C 41.37, H, 1.87, N 7.42. Found: C, 36.77; H, 2.41; N, 6.36.
FT-IR (KBr pellet): 3263s, 3099w, 1658 (s, amide CO stretch),
1558 (s, amide N–H bend), 1521s, 1500s, 1427s, 1338s, 1352s,
1257s, 1122s, 1062s, 991s, 757s, 696m cm−1.
[Cu(L2)2(μ-SO4)(H2O)]∝ CP1. Coordination polymer CP1
was synthesized by layering an aqueous methanolic solution
of CuSO4 (12 mg, 0.049 mmol) over a methanolic solution
of L2 (30 mg, 0.097 mmol). After two weeks blue block shape
X-ray quality crystals were obtained. Yield: 53.7% (38 mg,
0.027 mmol). Elemental analysis calcd for C26H16CuF10N4O7S
(%): C 39.93, H, 1.81, N 7.81. Found: C, 37.87; H, 1.62; N,
6.40. FT-IR (KBr pellet): 3282s (asymmetric O–H stretching),
3090, 3018, 2831, 1658 (s, amide CO stretch), 1564m, 1523
(s, amide N–H bend), 1492s, 1444m, 1417w, 1348m, 1323m,
1273m, 1203m, 1122 (s, asymmetric S–O stretching), 1104m,
1064s, 1018s, 1010m, 987s, 950m, 810s, 765s, 704s, 686,
650w, 603s cm−1.
C13H7F5N2O (%): C 51.67, H 2.33, N 9.27. Found: C 51. 4, H
1
2.13, N 9.08. H NMR (500 MHz, [D6] DMSO): δ = 9.522 (s, 1H,
N–H), 8.552 (s, 1H, Py–H), 8.502–8.494 (d, 1H, J = 4 Hz, Py–H),
7.728–7.712 (d, 1H, J = 8 Hz, Py–H), 7.420–7.395 (dd, J = 8,
4.7 Hz, 1H, Py–H), 4.662 (s, 2H,–CH2–), IR (KBr pellet): 3180 (s,
N–H stretch), 2985s, 2970m, 2819s, 1677 (s, urea CO stretch),
1656w, 1627w, 1571 (s, amide N–H bend), 1525s, 1449s, 1429w,
1413m, 1365s, 1326s, 1269m, 1118s, 1053s, 1037s, 983s, 881m,
802s, 742m, 709s, 682m, 646m, 632m cm−1. HRMS ESI
(CH3OH): m/z (%): 302 [(PyCH2NHCOC6F5)]+, 121, 301.
Synthesis of L3 (N-(4-pyridyl)-pentafluorobenzamide)
Synthetic procedure: 4-aminopyridine (0.42 g, 4.34 mmol) was
taken in a 250 ml RB flask in 40 mL THF. 2,3,4,5,6-
Pentafluorobenzoyl chloride (0.41 g, 4.34 mmol) in 30 ml
DCM was added to this solution at 0 °C and the mixture was
stirred for 30 minutes. Then the resulting solution was stirred
for 6 days at room temperature. The product was separated as
white colored precipitate, the precipitate was filtered and used
without further purification. Yield: 70% (0.88 g, 3.05 mmol).
Analytical data: m.p.: 159 °C. Elemental analysis calcd for
C12H5F5N2O (%): C 50.01, H 1.75, N 9.72. Found: C 49.45,
H 1.96, N 9.42.1H NMR (300 MHz, [D6] DMSO): δ = 11.407
(s, amide N–H), 8.551–8.541 (d, J = 5 Hz, 2H, Py–H), 7.641–7.632
(d, J = 4.5, 2H, Py–H), IR (KBr pellet): 3169 (s, N–H stretch),
3051 (m, aromatic C–H stretch), 2968s, 2883m, 2804w, 1708
(s, urea CO stretch), 1651s, 1626s, 1595 (s, amide N–H
bend), 1537s, 1514s, 1492s, 1421m, 1338s, 1301s, 1219s,
995s, 947s, 864s, 773m, 682w, 669m, 565s, 538s cm−1. HRMS
ESI (CH3OH): m/z (%): 289 [(PyNHCOC6F5)]+, 96.
[{Cu(L2)4(μ-SiF6)}·2H2O]∝ CP2. Coordination polymer CP2
was synthesized by layering a toluene methanolic solution of
Cu(BF4)2 (13.5 mg, 0.049 mmol) over a methanolic solution
of L2 (30 mg, 0.097 mmol). After two weeks blue block shape
X-ray quality crystals were obtained. FT-IR (KBr pellet): 3496,
3258, 3051, 1676 (s, amide CO stretch), 1520 (s, amide N–H
bend), 1501s, 1439w, 1663w, 1333s, 1270m, 1194m, 1118s,
1056w, 991s, 890s, 799s, 744s, 686w, 659s, 482m cm−1. Yield:
42% (35 mg, 0.021 mmol). Elemental analysis calcd for
C52H34CuF26N8O7Si (%): C 42.52, H, 2.33, N 7.63. Found: C,
40.62; H, 2.27; N, 7.20. FT-I.R (KBr pellet): 603s cm−1.
Synthesis of L4 (N-(3-pyridinyl)-N′-phenyl-urea)
Ligand is synthesized according to the literature procedure20
Synthesis of CCs and CPs
[Cu(L1)4·(SO4)·(DMSO)] CC1. Coordination complexes CC1
was synthesized by layering an aqueous ethanolic solution of
CuSO4 (12 mg, 0.049 mmol) over a methanolic solution of L1
(30 mg, 0.097 mmol). After two weeks blue plate shaped X-ray
quality crystals were obtained. Yield: 15.51% (45 mg, 0.027
mmol). Elemental analysis calcd for C50H30CuF20N12O9S2 (%):
C 41.40, H, 2.08, N 11.59. Found: C, 40.79; H, 2.12; N, 11.69.
FT-IR (KBr pellet): 3267s, 3220m, 3078w, 3031w, 2989, 1733s
(s, urea CO stretch), 1720s (s, urea CO stretch), 1652m,
1622s, 1593 (s, urea N–H bend), 1525s, 1504m, 1483m, 1463w,
1433m, 1328m, 1298m, 1251w, 1217s, 1135 (s, asymmetric S–O
stretching), 1086m, 1049s, 1010m, 981s, 950m, 883m, 800m,
694s, 648w, 611m, 555s cm−1.
[(H2O)2(DMSO)Cd(L1)2(μ2SO4)(Cd(L1)2·(SO4)·(DMSO)·(H2O)]
CC2. Coordination complex of L1 was synthesized by layering
an aqueous ethanolic solution of CdSO4 (38 mg, 0.049 mmol)
over a methanolic solution of L1 (30 mg, 0.097 mmol). After
two weeks colourless plate shaped X-ray quality crystals were
obtained. Yield: 46.9% (43 mg, 0.0234 mmol). Elemental
[{Cu(L3)4(ClO4)}·ClO4·H2O] CC4. Coordination complex
CC4 was synthesized by layering an aqueous ethanolic
solution of Cu(ClO4)2 (18.5 mg, 0.049 mmol) over
a
methanolic solution of L3 (28 mg, 0.097 mmol). After two
weeks deep blue blocked shape X-ray quality crystals were
obtained. Yield: 48.84% (35 mg, 0.024 mmol). Elemental
analysis calcd for C48H22Cl2F20N8O13Cu (%): C 40.23, H, 1.55,
N 7.82. Found: C, 40.66; H, 1.82; N, 7.36. FT-IR (KBr pellet):
3342 (s, aromatic C–H stretch), 3311w, 1720 (s, amide CO
stretch), 1658s, 1623s, 1596 (s, amide N–H bend), 1431s,
1338s, 1319s, 1319s, 1298s, 1211s, 1118 (s, asymmetric Cl–O
stretching of free ClO4), 1097 (s, asymmetric Cl–O stretching
of unidentate ClO4), 1058m, 1029s, 993s, 952s, 873m, 864m,
838s, 783s, 622s, 590s, 572s, 541s cm−1.
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[{Cu(L3)4(H2O)}·H2O·2BF4] CC5. Coordination complex
CC5 was synthesized by layering an aqueous ethanolic
solution of CuSO4 (12.1 mg, 0.049 mmol) over a methanolic
solution of L4 (21.4 mg, 0.097 mmol). After two weeks green
block shaped X-ray quality crystals were obtained. Yield: 46.22%
(26 mg, 0.0231 mmol). Elemental analysis calcd for
C48H45CuN12O15S (%): C 51.56, H, 5.04, N 15.00. Found: C, 51.64;
H, 4.31; N, 15.42. FT-IR (KBr pellet): 3340w, 3274s, 3199m,
3136m, 3082s, 3029m, 1703s (s, urea CO stretch), 1620 (s, urea
N–H bend), 1589s, 1566s, 1550s, 1483s, 1444s, 1326s, 1290s,
1259s, 1240s, 1227s, 1112 (s, free sulfate asymmetric S–O
stretching), 1097s, 1064w, 973s, 906m, 810m, 752s, 692s cm−1.
solution of Cu(BF4)2 (13.5 mg, 0.049 mmol) over
a
methanolic solution of L3 (28 mg, 0.097 mmol). After two
weeks deep blue blocked shape X-ray quality crystals were
obtained. Yield: 52% (38 mg, 0.026 mmol). Elemental ana-
lysis calcd for C48H24B2CuF28N8O6 (%): C 40.95, H, 1.58, N
7.96. Found: C, 40.12; H, 1.62; N, 7.51. FT-IR (KBr pellet):
3338 (m, aromatic C–H stretch), 3309m, 3193w, 3103w, 1720
(s, amide CO stretch), 1693s, 1656s, 1600 (s, amide N–H
bend), 1514s, 1431s, 1336s, 1321s, 1299s, 1211s, 1097s,
1083s, 1027s, 995ms, 875s, 838s, 783s, 572m, 541s cm−1.
−
ClO4 anion separation as CC4 by L3
[{(Cl)Cu(L3)4(μ-Cl)Cu(L3)4}·Cl·H2O]
CC6.
Coordination
Condition I (L3 : Cu(ClO4)2 : other copper salt = (2 : 1 : 1)).
a) To a methanol and ethanol solution of L3 (28.8 mg,
0.1 mmol), an aqueous solution of a mixture of CuCl2
(8 mg, 0.05 mmol), CuSO4·5H2O (12.1 mg, 0.05 mmol),
Cu(NO3)2·3H2O (12.2 mg, 0.05 mmol), Cu(ClO4)2 (18.5 mg,
0.05 mmol), Cu(BF4)2 (13.5 mg, 0.049 mmol) was kept
undisturbed and the solution allowed to evaporate slowly.
After one week good looking block shaped green crystals
were obtained. The crystals were washed in distilled water
and finally with methanol and characterized by elemental
analysis, X-ray powder diffraction (XRPD) and FT-IR.
complex CC6 was synthesized by layering an aqueous ethanolic
solution of CuCl2·2H2O (8.5 mg, 0.05 mmol) over a methanolic
solution of L3 (28 mg, 0.097 mmol). After two weeks deep blue
blocked shape X-ray quality crystals were obtained at 22 °C.
Yield: 30.5% (40 mg, 0.015 mmol). Elemental analysis calcd for
C96H48Cl4F40N16O23Cu2 (SQUEEZE calculation included) (%): C
40.85, H, 1.71, N 7.88. Found: C, 39.57; H, 1.81; N, 7.33. FT-IR
(KBr pellet): 3064 (s, aromatic C–H stretch), 2887, 1705
(s, amide CO stretch), 1654 (s, amide CO stretch), 1600
(s, amide N–H bend), 1518s, 1506s, 1429m, 1296m, 1213m,
1099, 1026s, 995m, 833m, 781, 572, 532 cm−1.
Thermogravimetric analysis (TG) revealed the weight loss
of 9.5% in the first step which corresponds the solvated two
water molecules (calc. weight loss = 19.6%). These results
indicate solvent loss while loading the sample.
[{Cu2(L3)4(μ-Cl)2·(Cl)2}·H2O] CC7. Coordination complex
CC7 was synthesized by layering an aqueous ethanolic
Condition II (L3 : Cu(ClO4)2 : other copper salts) = (2 : 1 : 2).
b) To a methanol and ethanol solution of L3 (28.8 mg,
0.1 mmol), an aqueous solution of
a
mixture of
CuCl2(16.2 mg, 0.05 mmol), CuSO4·5H2O (24.2 mg, 0.1 mmol),
Cu(NO3)2·3H2O (24.2 mg, 0.1 mmol), Cu(ClO4)2 (18.5 mg,
0.05 mmol), Cu(BF4)2 (27.8 mg 0.1 mmol) was kept
undisturbed and the solution allowed to evaporate slowly.
After one week good looking block shaped green crystals
were obtained. The crystals were washed in DMF, distilled
water and finally with methanol and characterized
by elemental analysis, X-ray powder diffraction (XRPD)
and FT-IR.
solution of CuCl2·2H2O (8.5 mg, 0.05 mmol) over
a
methanolic solution of L3 (28 mg, 0.097 mmol). After one
week sky blue plate shape X-ray quality crystals were obtained
at 38 °C. Yield: 51.5% (37 mg, 0.0257 mmol). Elemental anal-
ysis calcd for C48H22Cl4Cu2F20N8O5 (%): C 40.05, H, 1.54, N
7.78. Found: C, 40.48; H, 1.53; N, 7.46. FT-IR (KBr pellet):
3344 (s, water O–H stretch), 3224 (m, aromatic C–H stretch),
3164w, 3078w, 3001w, 1716 (s, amide CO stretch), 1710,
1652s, 1596 (s, amide N–H bend), 1504s, 1425s, 1336s,
1321w, 1292m, 1211s, 1099m, 1064m, 1027m, 995s, 952m,
873m, 829s, 781s, 669m, 572m, 536m cm−1.
[Cu(L3)2(Cl)2] CC8. Coordination complex CC8 was
synthesized by layering an aqueous ethanolic solution of
CuCl2·2H2O (8.5 mg, 0.05 mmol) over a methanolic solution
of L3 (28 mg, 0.097 mmol). After one week deep blue needle
shape X-ray quality crystals were obtained below ∼38 °C and
above 22 °C. Yield: 61.8% (22 mg, 0.0309 mmol). Elemental
analysis calcd for C24H10Cl2F10N4O2Cu (%): C 40.55, H, 1.42,
N 7.78. Found: C, 40.49; H, 1. 35; N, 7.73. FT-IR (KBr pellet):
3309, 3253 (s, aromatic C–H stretch), 3172 (w), 3085w, 3004w,
1720 (s, amide CO stretch), 1685s, 1618s, 1595 (s, amide
N–H bend), 1515s, 1504s, 1431s, 1415m, 1338s, 1321s,
1294m, 1211m, 1095m, 1066s, 1029m, 993s, 948s, 873s, 831s,
781m, 671, 590w, 570w, 532s cm−1.
Acknowledgements
We thank Department of Science & Technology (DST), New
Delhi, India for financial support. S. B. thanks IACS for
research fellowships. S. B. also acknowledges Dr N. N Adarsh
for his fruitful discussion during solving structure of some
the compounds and Tapas for the table of content artwork.
Single crystal X-ray diffraction was performed at the
DST-funded National Single Crystal Diffractometer Facility
at the Department of Inorganic Chemistry, IACS.
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