A novel type of coordination mode of chloranilic acid leading to the formation of polymeric coordination ribbon in the series of mixed-ligand copper(ii) complexes with 1,10-phenanthroline

Article abstract of DOI:10.1039/c3dt53332h

A series of four novel mixed-ligand complexes of copper(ii) with 3,6-dichloro-2,6-dihydroxy-1,4-benzoquinone (chloranilic acid) and 1,10-phenanthroline was prepared and characterised by X-ray structure analysis and IR spectroscopy. Three complexes exhibit square-pyramidal coordination, whereas one exhibits octahedral coordination. The ligand 1,10-phenanthroline acts in a bidentate chelating mode with N,N-metal binding. The chloranilate dianion coordinates to the Cu^II atom in a terminal bidentate ortho-quinone-like mode, forming a mononuclear complex species. However, in one structure a novel type of coordination mode of chloranilate is observed. In addition to the bidentate mode, a monodentate bridging mode through a carboxy oxygen of a symmetry-related dianion leads to the formation of polymeric coordination ribbon. The crystal packing of penta-coordinated species, in addition to hydrogen bonding, involves less common stacking interactions of chelate rings with the π-systems of the ligands.

Full text of DOI:10.1039/c3dt53332h

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
A novel type of coordination mode of chloranilic
acid leading to the formation of polymeric
coordination ribbon in the series of mixed-ligand
copper(II) complexes with 1,10-phenanthroline†
Cite this: Dalton Trans., 2014, 43,
7208
Krešimir Molčanov,* Marijana Jurić and Biserka Kojić-Prodić
A series of four novel mixed-ligand complexes of copper(II) with 3,6-dichloro-2,6-dihydroxy-1,4-benzo-
quinone (chloranilic acid) and 1,10-phenanthroline was prepared and characterised by X-ray structure
analysis and IR spectroscopy. Three complexes exhibit square-pyramidal coordination, whereas one exhi-
bits octahedral coordination. The ligand 1,10-phenanthroline acts in a bidentate chelating mode with
N,N-metal binding. The chloranilate dianion coordinates to the CuII atom in a terminal bidentate ortho-
quinone-like mode, forming a mononuclear complex species. However, in one structure a novel type of
coordination mode of chloranilate is observed. In addition to the bidentate mode, a monodentate brid-
ging mode through a carboxy oxygen of a symmetry-related dianion leads to the formation of polymeric
coordination ribbon. The crystal packing of penta-coordinated species, in addition to hydrogen bonding,
involves less common stacking interactions of chelate rings with the π-systems of the ligands.
Received 26th November 2013,
Accepted 14th February 2014
DOI: 10.1039/c3dt53332h
www.rsc.org/dalton
Introduction
Novel multifunctional materials based on conjugated π-elec-
tron systems have attracted a lot of attention in materials
chemistry.1–6 Of these compounds, complexes of transition
metals and organic π-functional ligands have been intensively
studied. It is well known that in the design of mono- and
polynuclear (homo- and hetero-) complexes as new functional
materials with desirable physical properties (mechanical,
optical, electrical, or magnetic), an important role belongs to
Scheme 1 Chloranilate dianion and an oxalate dianion, with their ana-
2−
the oxalate C2O4 anion,7 being arguably one of the most ver- logous functional groups responsible for the coordination to metal ions.
satile ligands. Its various possibilities of coordination to metal
centres and the ability to mediate magnetic interactions
prepare novel (multi)functional materials using quinoid
systems.18–20 The proper selection of mixed organic ligands to
complex suitable metal ions should lead to desired architec-
tures and properties. However, the large number of
compounds obtained during these syntheses, among which a
limited number reveal the desired properties, means that
entirely controlled syntheses are yet to be reported.
The chloranilate dianion ligand acts as a larger spacer, but
still may allow some degree of charge transfer between the
metal centres; it acts as an electron acceptor, and the inter-
action through its elongated conjugated π electron systems is
feasible.
between paramagnetic metal ions (separated by more than
5 Å) are responsible for the existence of a huge number of
oxalate-based transition metal species, of different nuclearity
and dimensionality.8–10 A recent example of oxalate complexes
as precursors in the synthesis of novel nanocrystalline mixed
metallic oxides11–13 has been widely exploited.
Thus, our recent (magneto)structural studies on oxalate-
based metal complexes14–17 have been extended to the reac-
tions of the similar, but more stretched, chloranilate dianion
(Scheme 1) and transition metals. Our research aims to
Rudjer Bošković Institute, Bijenička 54, HR-10000 Zagreb, Croatia.
E-mail: kmolcano@irb.hr
†CCDC 973343–973346. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt53332h.
Our research has been directed to prepare and characterise
mixed CuII complexes using 3,6-dichloro-2,6-dihydroxy-
1,4-benzoquinone (chloranilic acid) and the nitrogen donor
7208 | Dalton Trans., 2014, 43, 7208–7218
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
ligands 2,2′-bipyridine18 and its congener, 1,10-phenanthro-
line (in the present work). It is of interest to prepare mixed
complex species to resolve the impact of the binding mode of
both ligands on metal coordination and crystal packing. In the
series of CuII mixed complexes with chloranilic acid, coordi-
nating in a terminal bidentate ortho-quinone-like mode, mono-
nuclear species have been observed independently with the
use of 2,2′-bipyridine18 or 1,10-phenanthroline ligands. In
the case of CuII complexes, an addition of bidentate chelating
N-ligands generally favours the formation of mononuclear
units18 (as confirmed by the presented results in this study).
However, in the present series, a novel coordination
bonding mode of chloranilic acid leading to the formation of
polymeric species is observed. Both ligands include π-systems
that can be stacked, influencing the crystal packing. A striking
example is the recently described preparation, structure and
magnetic properties of the stable 1,2,5[thiadiazolo][3,4-f][1,10-
phenanthroline 1,1-dioxide] radical anion which combines the
strong electron-withdrawing properties of the thiadiazole
dioxide moiety and the acceptor ability of the entire radical
anion. The phenanthroline and thiadiazole dioxide moieties
act as the ligands, which are responsible for multidimensional
interactions.21
Scheme 2 Dissociation of chloranilic acid to the monoanion and
dianion, with resonance structures shown in brackets.
The selection of chloranilic acid and 1,10-phenanthroline
for the synthesis of the complexes was motivated by the highly
functionalised properties of both ligands. A variety of electrical
and magnetic properties can be engineered by a simple combi-
nation of quinones, metals and other ancillary ligands.4,22 The
electronic properties of conjugated systems can be modified,
thus allowing a wide variety of electrical and magnetic pro-
perties. Among the most interesting candidates for the syn-
Scheme 3 Three coordination modes of chloranilic acid: (a) bridging
(bis)bidentate is the most common, but not observed in the series
studied; (b) terminal bidentate is less common, but observed in this
study; and (c) the novel bidentate
+ bridging monodentate mode
observed for the first time in this study, which leads to the formation of
thesis of novel multifunctional materials are stable organic polynuclear species.
radicals4,23 such as semiquinones. Their closed-shell relatives,
quinones, often participate in charge transfer, since they are
stabilizes the solid-state structures. Usually, 2,5-dihydroxyqui-
easily reduced into the radical form. The combination of para-
magnetic metal centres and electron-accepting quinoid rings
is particularly interesting and promising in the synthesis
of novel functional materials,1–3,5,6,24 particularly spintronics,
that are in our focus.19,20,24
nones behave as (bis)bidentate ligands with the possibility
to perform catena-bridging that generates polymeric
complexes.29–37 However, mononuclear complexes with chlora-
nilic acid acting as a terminal bidentate ligand are also
known.18,33,34,38–40 Among the polymeric species known,35
there is an example of the structure comprising the chlorani-
late dianion and 1,10-phenanthroline ligands that we used to
prepare the complexes presented in this work. The bidentate
chloranilate dianion acting as a double bridging ligand
generates zig-zag polymeric eight-coordinated Cd(II) chains
connected into a 3D structure by stacking interactions between
phen ligands arranged in an offset face-to-face fashion.
The self-assembly of metal complexes with organic ligands,
and sometimes solvents or guest molecules, based on combi-
nations of intramolecular and intermolecular interactions
reveals various topologies. Architectures such as chains,
ladders, grids, honeycombs and others can be obtained,
forming voids shaped as cavities, channels and space between
layers. Differently shaped space among the molecules and
atoms, termed as nano-space, can be functionalized for
various purposes.28
Substituted 2,5-dihydroxyquinones, such as chloranilic acid
(3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone, CA, Scheme 2)
are a sub-class of quinoid compounds which are especially
promising for the synthesis of novel functional materials. They
are strong proton donors and acceptors25 which are capable of
forming various kinds of hydrogen bonds. The acidity of the
hydroxy-groups of 2,5-dihydroxyquinone is enhanced by elec-
tron-withdrawing substituents. Therefore, the unsubstituted
2,5-dihydroxyquinone behaves as a weak organic acid (with
pKa values of 2.73 and 5.18, respectively26), but its dinitro ana-
logue is a very strong acid comparable to sulfuric or perchloric
acid (its pKa values being −3.0 and −0.5, respectively26).
2,5-Dihydroxyquinones are also good ligands and easily
coordinate transition metals;27,28 they can act as bridging
(bis)bidentate or terminal bidentate ligands (Scheme 3). The
introduction of organic ligands containing N-donors influ-
ences the nuclearity and the topology of the metal centres and
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7208–7218 | 7209

View Article Online
Paper
Dalton Transactions
Scheme 4 Complexes described in this paper.
1,10-Phenanthroline has been widely exploited as a versatile
ligand due to its distinctive properties.41 The rigid structure
with the central aromatic ring keeps the two nitrogens juxta-
posed, in contrast to 2,2′-bipyridine where a free rotation
about the linking bond is possible. However, the size of the
two ligands is similar, so their analogous complexes may in
some cases be isostructural.17 Due to the entropic advantage,
1,10-phenanthroline easily forms metal complexes. The intro-
duction of hydrophobic and bulky ligands into complexes is
verified to be an effective way to enhance their stability,
whereas their bulkiness reduces intermolecular interactions
and can be of benefit for photoluminescence and electrolumi-
nescence. Thus, a plethora of metal complexes containing
N,N′-chelating heterocycles including 1,10-phenanthroline have
been used as functionalised molecules in optical devices,42
catalysis43 and as components of supramolecular structures.44
On the other hand, the ligand planarity allows 1,10-phenan-
throline to act as an intercalating or groove-binding species
with DNA and RNA,45,46 and also as a nucleoside constituent
for incorporation into the DNA backbone.47
In this paper we report on a series of mononuclear com-
plexes of chloranilic acid (its anion is abbreviated as CA) and
1,10-phenanthroline (abbreviated as phen) with copper(II)
(Scheme 4). A novel, bidentate + bridging coordination mode
of chloranilic acid is described (Scheme 3c), which has been
observed for the first time.
Results and discussion
Molecular structures
Fig. 1 Penta and hexa-coordinated complexes of: [Cu(CA)(phen)]n, 1,
[Cu(CA)(phen)(H2O)]·H2O, 2 (molecule a), [Cu(CA)(phen)(C2H5OH)], 3,
and [Cu(CA)(phen)2]·CH3OH, 4. Displacement ellipsoids are drawn at the
probability of 50% and hydrogen atoms are shown as spheres of arbi-
trary radii. Symmetry operators: (i) 1 − x, 1/2 + y, 1/2 − z; (ii) 1 − x, −1/2 +
y, 1/2 − z; (iii) 1 − x, y, 1/2 − z.
The novel mixed-ligand copper(II) complexes were prepared:
[Cu(CA)(phen)]n, (1), [Cu(CA)(phen)(H2O)]·H2O, (2), [Cu(CA)-
(phen)(C2H5OH)], (3), all three in the square-pyramidal coordi-
nation, and [Cu(CA)(phen)2]·CH3OH, (4) with an octahedral
coordination (Fig. 1, Table 1). The mononuclear complexes are
encountered in 2, 3 and 4, whereas 1 is a polynuclear species.
7210 | Dalton Trans., 2014, 43, 7208–7218
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Table 1 Geometric parameters of copper(II) coordination spheres (Å, °). Symmetry operators: (i) 1 − x, 1/2 + y, 1/2 − z; (ii) 1 − x, y, 1/2 − z
1
2a
2b
3
Cu1–O1
Cu1–O2
Cu1–N1
1.924(2)
1.9309(15)
1.9924(19)
1.991(2)
2.574(2)
85.12(8)
173.20(9)
96.19(8)
95.32(8)
94.95(8)
177.21(9)
97.09(8)
83.45(8)
91.42(8)
85.25(8)
4
Cu1–O1
Cu1–O2
Cu1–N1
Cu1–N2
1.943(2)
1.9577(19)
2.011(2)
2.009(2)
2.1980(18)
84.24(8)
165.54(9)
93.93(9)
101.68(8)
95.85(9)
166.11(8)
98.10(8)
82.51(9)
95.76(8)
92.64(8)
1.9481(19)
1.942(2)
1.986(2)
1.997(2)
2.281(2)
84.22(8)
166.66(9)
93.73(8)
102.53(8)
95.13(9)
164.11(9)
96.60(8)
83.25(9)
99.22(8)
90.80(8)
1.940(4)
1.948(4)
1.993(5)
1.985(5)
2.275(5)
84.00(17)
170.8(2)
95.02(18)
94.6(2)
96.99(18)
170.9(2)
91.4(2)
82.55(18)
97.67(19)
94.5(2)
Cu1–N2
Cu1–O3i
Cu1–O5
O1–Cu1–O2
O1–Cu1–N2
O1–Cu1–N1
O1–Cu1–O3i
O2–Cu1–N2
O2–Cu1–N1
O2–Cu1–O3i
N2–Cu1–N1
N2–Cu1–O3i
N1–Cu1–O3i
O1–Cu1–O2
O1–Cu1–N2
O1–Cu1–N1
O1–Cu1–O5
O2–Cu1–N2
O2–Cu1–N1
O2–Cu1–O5
N1–Cu1–N2
N1–Cu1–O5
N2–Cu1–O5
Cu1–N1ii
2.016(2)
2.016(2)
2.161(3)
2.161(3)
2.161(2)
2.161(2)
175.73(11)
80.10(10)
97.05(10)
92.21(10)
91.15(10)
97.05(10)
80.10(10)
91.15(10)
92.21(10)
97.34(10)
93.88(9)
166.52(9)
166.52(9)
93.88(9)
76.10(9)
Cu1–N1
Cu1–N2
Cu1–N2ii
Cu1–O1
Cu1–O1ii
N1ii–Cu1–N1
N1ii–Cu1–N2
N1ii–Cu1–N2ii
N1ii–Cu1–O1
N1ii–Cu1–O1ii
N1–Cu1–N2
N1–Cu1–N2ii
N1–Cu1–O1
N1–Cu1–O1ii
N2–Cu1–N2ii
N2–Cu1–O1
N2–Cu1–O1ii
N2ii–Cu1–O1
N2ii–Cu1–O1ii
O1–Cu1–O1ii
Their crystal structures and infrared spectroscopic character- complexes, is of high kinetic stability in comparison with
istics are described.
penta-coordination.53 The phen ligand is slightly twisted
The bite angles of the bidentate phen and chloranilate out of the equatorial plane with the Cremer–Pople54 puckering
ligands are considerably less than 90° (Table 1), significantly parameter Q = 0.176(3) Å.
contributing to the coordination polyhedra distortion. The
In [Cu(CA)(phen)(H2O)]·H2O (2) and [Cu(CA)(phen)
compound [Cu(CA)(phen)]n (1) comprises chloranilate (O,O) (C2H5OH)] (3), water and ethanol molecules are coordinated at
and phen ligands (N,N) coordinated to Cu in an equatorial the apical position of the square-pyramid (Fig. 1). The phen
plane (Fig. 1), with an additional O3 atom (from a symmetry- ligands in 2 are slightly twisted (with puckering amplitudes54
related chloranilate dianion: 1 − x, 1/2 + y, 1/2 − z) located at of 0.159(3) and 0.086(3) Å for molecules a and b, respectively)
an apical site of a square-pyramid. This bridging ligand gener- and the angle between the mean planes of the chloranilate
ates a polymeric coordination chain. The observed Cu–O3 dis- and phen ligands are 18.7° and 19.2°, respectively. However, 3
tance of 2.574(2) Å (Table 1) is significantly longer than the is more planar, with the mean planes of phen and chloranilate
typical Cu–O covalent bond (1.98 Å48), but it is shorter than being inclined by only 1.0°; the puckering amplitude of phen
the sum of the van der Waals radii (2.92 Å). According to the is 0.209(7) Å. The copper atom is displaced by 0.129 Å above
Cambridge Structural Database,49 the distribution of Cu–O the least-squares plane of the phen and CA ligands.
bonds is bimodal, with the average values of 1.95(4) Å and
In [Cu(CA)(phen)2]·CH3OH (4), two phen ligands are co-
2.36(16) Å; the larger value corresponds to longer distances ordinated to the CuII in an octahedral arrangement together
observed in the 4 + 1 and 4 + 2 coordinations, which are often with the ligand CA (Fig. 1), revealing the C2 molecular
longer than 2.5 Å. These coordination modes were recognised symmetry. The octahedron is significantly distorted due to the
from structural and spectroscopic data.33,50–52 The penta- O–Cu–O and N–Cu–N bite angles, which are considerably
coordination mode in CuII complexes reveals square-pyramidal smaller than 90° (Table 1).
and trigonal-bipyramidal coordinations. The square planar,
The geometry of the chloranilate ligand (Table 2) is some-
four-coordination mode, typical of the d9 configuration in CuII where between a dianion and an o-quinone (Scheme 2), as
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7208–7218 | 7211

View Article Online
Paper
Dalton Transactions
Crystal packing
Table 2 Bond lengths in the chloranilate dianion (Å)
In the series studied, penta-coordinated complexes crystallized
in noncentrosymmetric space groups, whereas the octahedral
complex reveals C2 molecular symmetry with CuII located on a
twofold rotation axis in the space group C2/c. The topology of
their packing patterns is entirely different (Fig. 2–7). The two
types of interactions occur in their crystal packing: hydrogen
bonding occurs in 3 and 4, whereas in 1, only stacking inter-
actions are encountered. However, the crystal packing of 2
reveals intensive interactions of both types (Tables 4 and 5).
In 3, both types of intramolecular interactions are presented,
including hydrogen bonding between ethanol molecules and
chloranilate, and phen⋯chloranilate stacking interactions
(Tables 4 and 5). In complexes 2 and 3 with ligands exhibiting
proton donor and acceptor functionalities, hydrogen bonding
interactions affect their crystal packing (Table 5, Fig. 4–6). The
crystal solvent molecules in 2 and 4 play a role in their crystal
packing via the formation of hydrogen bonds (Table 5).
Due to a lack of proton donor/acceptor functionalities in 1,
hydrogen bonding is not possible. However, the crystal
packing of 1 is dominated by stacks of (a) Cu–O–chloranilate
chelate rings with phen rings, (b) Cu–N–chelate–phen rings
1
2a
2b
3
4a
C1–C2
C2–C3
C3–C4
C4–C5
C5–C6
C6–C1
C1–O1
C2–O2
C4–O3
C5–O4
C3–Cl1
C6–Cl3
1.509(4)
1.378(3)
1.415(3)
1.563(4)
1.431(4)
1.364(4)
1.286(3)
1.284(3)
1.234(3)
1.215(3)
1.743(3)
1.734(3)
1.521(4)
1.377(3)
1.414(4)
1.556(4)
1.426(4)
1.375(4)
1.279(3)
1.280(3)
1.230(3)
1.220(3)
1.731(3)
1.725(3)
1.513(4)
1.370(4)
1.425(4)
1.556(4)
1.416(4)
1.381(4)
1.275(3)
1.281(3)
1.230(4)
1.237(3)
1.730(3)
1.726(3)
1.515(8)
1.374(8)
1.414(9)
1.543(10)
1.433(9)
1.368(8)
1.287(7)
1.277(6)
1.233(8)
1.213(9)
1.731(6)
1.735(6)
1.547(4)
1.373(4)
1.412(4)
1.547(4)
1.412(4)
1.373(4)
1.265(4)
1.265(4)
1.229(4)
1.229(4)
1.744(4)
1.744(4)
a Equivalent bonds; due to the molecular symmetry C2, the labelling is
different.
found in similar mononuclear complexes with bpy as the ancil-
lary ligand,18 and it appears to be usual when a 2,5-dihydroxy-
quinolate acts as a terminal bidentate ligand.25 There are two
sets of C–O bonds: those coordinated to Cu are longer (being
close to single bonds, Table 2), while the uncoordinated bonds
are shorter (being close to double bonds, Table 2). The
o-quinoid electronic structure is also confirmed by IR
spectroscopy (Table 3).
Selected absorption bands ascribed to the vibrations of the
bidentate chloranilate anion for compounds 1–4 are given in
Table 3.55 The red and blue shifts of the observed position of
ν(CvC) and ν(C–C), respectively, relative to the infrared
spectra of solid chloranilic acid (H2CA),56 are due to the exist-
ence of delocalization in the terminal bidentate chloranilate
anion in compounds 1–4. Two peaks of very low intensity at
1629 and 1611 cm−1, present in the spectrum of compound 1,
could be ascribed to the binding of one of the CvO bonds of
the chloranilate dianion to the copper(II) atoms in a bridging
mode, leading to the formation of the polymeric ribbon. Other
absorption bands of significant intensities in the spectra
of compounds 1–4 correspond to different vibrations of the
1,10-phenanthroline ligand.57
Fig. 2 A polymeric ribbon of 1 extending in the [010] direction.
The broad band of strong intensity with a maximum
around 3420 cm−1 in the spectrum of compound 2 originates
from the O–H stretching vibration [ν(OH)], and is in agreement
with the presence of coordinated and crystal water molecules.
The relatively sharp bands of medium intensity centred
at 3394 cm−1 in the spectra of 3 and 4 are consistent with the
O–H stretching vibration [ν(OH)] of alcohol solvates involved
in the intermolecular hydrogen bonds.55
Fig. 3 π-Interactions between two contiguous coordination polymers
of 1 reveal stacking of the 1,10-phenanthroline and chloranilate moi-
eties. To emphasize the stacking, a pair of [Cu(CA)(phen)] units has been
depicted as van der Waals spheres.
Table 3 Selected absorption bands (cm−1) of the bidentate chloranilate dianion in the IR spectra of compounds 1–4
Compound
ν(CvC)
ν(CvO)
ν(C–O)
ν(C–C)
ν(C–Cl)
δ(CCvO)
C–Cl wagging
1636, 1615
1629, 1611
1637, 1615
1632, 1614
1635, 1614
1
1646
1366
997
843
668
573
2
3
4
1646
1648
1647
1373
1374
1374
999
999
999
845
845
845
668
668
668
573
574
574
7212 | Dalton Trans., 2014, 43, 7208–7218
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 4 Crystal packing of 2, composed of hydrogen bonded chains of
the two symmetry-independent molecules a (green) and b (blue).
Fig. 6 (a) Hydrogen bonded chain of 3 parallel to [100]; (b) packing of
these chains viewed in the [100] direction.
Fig. 5 (a) Stacking of 1,10-phenanthroline ligands between hydrogen
bonded chains in 2 generating layers parallel to the (101) plane; (b)
packing of the layers viewed in the [100] direction.
with phen rings (Fig. 8), and (c) chloranilate⋯phen rings
(Table 4, Fig. 3 and 8). Electron delocalization occurring in the
five-membered Cu–chelate rings make them susceptible to
interactions with other π-systems in the unit cell.58–62 Direct
stacks between chelate rings are not encountered in this series
of complexes. On the contrary, such interactions were observed
in the structures of mixed Cu(II) complexes with bipyridine
and chloranilate.18
Fig. 7 Crystal packing of 4 viewed in the [001] direction with channels
occupied by disordered MeOH molecules, presented by van der Waals
spheres.
Chemically different rings being stacked in the complexes
1–3 are matched as follows (details in Table 4): (a) chelate
ring⋯phen, (b) chelate ring⋯chloranilate, (c) chloranilate⋯
phen and (d) phen⋯phen are arranged in nearly parallel
arrangement with the tilt angle in the range 0.63(14)–
19.86(11)°. The offset between the rings is observed in the
crystal packing of 2 and 3, whereas in 1 there is no offset. The
geometrical parameters point to the presence of specific inter-
actions in the crystal packing of these complexes. However, an
evaluation of their nature and the appropriate terminology are
open to discussion.20,63,64
Compound 1 reveals a polymeric coordination chain of
[Cu(CA)(phen)] units linked by the long Cu–O3i [symmetry
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7208–7218 | 7213

View Article Online
Paper
Dalton Transactions
Table 4 Geometric parameters of the π-interactions
π⋯π
Cga⋯Cg/Å
αb
βc
Cg⋯plane(Cg2)/Å
Offsetd/Å
Symm. op. on Cg2
1
Cu1→O2⋯C10→C17
Cu1→N2⋯C1→C6
N1→C11⋯C1→C6
C1→C6⋯C10→C17
C1→C6⋯C10→C17
2
3.6893(13)
3.9022(13)
3.4014(15)
3.5506(14)
3.9498(14)
8.58(11)
24.05
28.19
7.64
19.67
33.59
3.1189(9)
2.9241(9)
3.3446(11)
3.3583(10)
3.3321(10)
—
—
—
—
—
−x, −1/2 + y, 1/2 − z
1 − x, 1/2 + y, 1/2 − z
1 − x, 1/2 + y, 1/2 − z
−x, −1/2 + y, 1/2 − z
1 − x, −1/2 + y, 1/2 − z
15.64(11)
9.14(12)
8.34(12)
8.34(12)
Cu1a→N2a⋯N1b→C11b
Cu1a→N2a⋯C10b→C17b
Cu1b→N2b⋯N2a→C16a
Cu1b→O2b⋯C1a→C6a
Cu1b→N2b⋯C10a→C17a
N1a→C11a⋯N1b→C11b
N2a→C16a⋯N1b→C11b
N2a→C16a⋯C10b→C17b
C10a→C17a⋯N1b→C11b
3
3.6353(14)
3.6618(15)
3.4676(15)
3.8621(15)
3.8244(15)
3.8612(17)
3.7184(17)
3.7500(16)
3.6922(16)
3.17(12)
2.06(12)
0.84(12)
18.47(12)
3.86(11)
5.77(14)
1.12(14)
0.63(14)
4.14(13)
18.33
24.08
14.17
26.96
29.52
26.96
24.78
26.49
20.02
3.4050(9)
3.3947(8)
3.3596(12)
3.8104(10)
3.4429(11)
3.1547(9)
3.3460(12)
3.3745(12)
3.4613(11)
1.14
1.49
0.85
—
1.88
—
0.91
1.67
1.26
2 − x, 1/2 + y, 2 − z
2 − x, 1/2 + y, 2 − z
2 − x, 1/2 + y, 2 − z
−1 + x, y, z
2 − x, 1/2 + y, 2 − z
2 − x, 1/2 + y, 2 − z
2 − x, 1/2 + y, 2 − z
2 − x, 1/2 + y, 2 − z
2 − x, 1/2 + y, 2 − z
C1→C6⋯C10→C17
3.477(4)
2.1(3)
8.49
3.420(3)
0.51
−1 + x, y, z
a Cg = centre of gravity of the interacting ring. b α = angle between the planes of two interacting rings. c β = angle between the Cg⋯Cg line and the
normal to the plane of the first interacting ring. d Offset can be calculated only for the strictly parallel rings (α = 0.00°). For slightly inclined rings
(α ≤ 5°) an approximate value is given.
Table 5 Geometric parameters of hydrogen bonds
D–H/Å
H⋯A/Å
D⋯A/Å
D–H⋯A/°
Symm. op. on A
2
O5a–H5a⋯O4b
O5a–H5b⋯O3a
O5a–H5b⋯O4a
O5b–H5c⋯O3a
O5b–H5d⋯O3b
O5b–H5d⋯O4b
O6–H6b⋯O5b
3
0.92(3)
0.93(2)
0.93(2)
0.83(4)
0.93(3)
0.94(2)
0.97(9)
1.86(3)
2.29(4)
2.04(4)
2.06(4)
1.86(4)
2.19(5)
2.06(9)
2.777(3)
3.018(3)
2.852(3)
2.841(5)
2.755(3)
2.983(3)
2.958(5)
176(3)
135(4)
135(4)
158(5)
161(3)
143(6)
152(6)
1 − x, 1/2 + y, 1 − z
1 + x, y, z
1 + x, y, z
x, y, z
1 − x, −1/2 + y, 1 − z
1 + x, y, z
x, y, z
O5–H5⋯O4
O5–H5⋯O3
4
O3–H3⋯O2
C7–H7⋯O3
C9–H9⋯O2
C9–H9⋯Cl1
C13–H13⋯Cl1
0.82(4)
0.82(4)
2.06(5)
2.46(5)
2.844(7)
2.939(7)
161(6)
118(6)
1 + x, y, z
1 + x, y, z
0.82
0.93
0.93
0.93
0.93
2.31
2.77
2.61
2.91
2.92
2.764(8)
3.247(9)
3.473(7)
3.643(8)
3.662(7)
115
121
154
136
138
x, y, z
3/2 − x, −1/2 + y, 1/2 − z
x, 1 − y, −1/2 + z
x, 1 − y, −1/2 + z
3/2 − x, −1/2 + y, 1/2 − z
operator (i) 1 − x, 1/2 + y, 1/2 − z] bond extending in the [010] chains, connects them into layers parallel to the (101) plane
direction (Fig. 2). Lacking proton donor sites, these chains are (Fig. 5). However, these layers are connected only by dispersion
stacked through interactions of various π-systems, forming interactions.
layers parallel to the (110) plane (Fig. 3, Table 4). There are
The molecular structure of 3 reveals a coordinated ethanol
only dispersion interactions between these layers.
molecule, located in the apical position, acting as a proton
In the crystal structure of 2 there are two symmetry- donor in hydrogen bonds; the chains formed extend in the
independent molecules, a and b, and a molecule of crystal [100] direction (Fig. 6, Table 5). There is π-stacking between
water. The coordinated water molecule (O5) at the apical posi- the chloranilate and phen ligands (Table 4). Generally,
tion of the square-pyramid acts as a donor of two protons in dispersion interactions dominate in the crystal structure of 3.
hydrogen bonds, forming ladder-like double chains (a and b
Compound 4 crystallizes as a methanol solvate. The MeOH
molecules) extending in the [100] direction (Fig. 4, Table 5). molecule is disordered, with its methyl group lying on the
The crystal water molecule acts as a single proton donor in twofold rotation axis. The OH group is disordered over two
hydrogen bonds as a pendant to molecule b (Fig. 4). In the positions (of 0.5 population parameter), and in both orien-
crystal packing of 2, extensive hydrogen bonding, together tations it serves as a proton donor to O2 (chloranilate) of the
with various combinations of π-interactions involving chelate, same asymmetric unit (Table 5). Molecules of the complex are
aromatic (phen), and quinoid (chloranilate) rings between linked by C–H⋯O and C–H⋯Cl hydrogen bonds (Table 5). The
7214 | Dalton Trans., 2014, 43, 7208–7218
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
for compounds 2 and 3 (samples of other two compounds
were inhomogeneous due to the presence of free chloranilic
acid; however a few crystals could be separated to measure the
IR spectrum).
Preparation
Preparation of [Cu(CA)(phen)]n (1). After mixing a methanol
solution (4 mL) of CuCl2·2H2O (17.1 mg; 0.1 mmol) with a
methanol solution (4 mL) of 1,10-phenanthroline (19.9 mg;
0.1 mmol), the reaction mixture became cloudy and a green
precipitate immediately formed. It was removed by filtration
and the clear solution was carefully laid above an aqueous
solution (5 mL) of H2CA (20.9 mg; 0.1 mmol) into a test
tube. Deep dark violet, almost black, prismatic single crystals
of 1 were formed after a few weeks. The yield was ∼29%.
IR data (KBr, cm−1): ˜ν = 1646 (m), 1636 (w), 1629 (sh),
1615 (sh), 1611 (m), 1588 (w), 1550 (vs), 1518 (s), 1499 (vs),
1458 (w), 1427 (m), 1366 (s), 1343 (m), 1310 (m), 1254 (w),
1223 (w), 1209 (sh), 1144 (sh), 1110 (w), 1051 (sh), 997 (w),
875 (w), 843 (s), 775 (w), 742 (w), 722 (m), 668 (w), 653 (w),
604 (m), 573 (m), 435 (w), 419 (w).
Preparation of [Cu(CA)(phen)(H2O)]·H2O (2). After mixing
an ethanol solution (4 mL) of 1,10-phenanthroline (19.9 mg;
0.1 mmol) with an ethanol solution (4 mL) of H2CA (20.9 mg;
0.1 mmol), the clear solution was carefully laid above an
aqueous solution (6 mL) of CuCl2·2H2O (17.1 g; 0.1 mmol)
into a test tube. X-ray-quality black needle-like single crystals
of 2 were formed after two weeks. The yield was ∼78%. Anal.
Calcd for C36H22Cl4Cu2N4O11 (Mr = 955.49): C 45.21, H 2.32,
N 5.86%; found: C 45.47, H 2.22, N 5.86%.
Fig. 8 π-Interactions involving chelate rings in the crystal packing of 1:
(a) interaction of the Cu–O–chelate ring with a phen ligand and (b)
interaction of the Cu–N–chelate ring and chloranilate ligand.
porous crystal packing reveals channels running parallel to
[001] that are filled by disordered methanol molecules (Fig. 7).
The five-membered Cu-N,N-phen and Cu-O,O-chloranilate
chelate rings in 1 and 2 participate in stacking interactions
with quinoid chloranilate and aromatic phenanthroline rings
(Table 4). In both molecules (a and b) of the asymmetric unit
of 2, the Cu–N–phen and Cu–O–chloranilate chelate rings are
planar (the average value of deviations from the least-square
planes are: a 0.006(2), 0.007(2) Å; b 0.010(1), 0.013(2) Å,
respectively) and prone for stacking with the π-systems of the
ligands (Table 4). In contrast, in the series of CuII complexes
comprising chloranilate and bpy ligands, chelate⋯chelate
stacks have been observed.18
There are quite a few examples of π-stacking between
chelate and aromatic rings; the interactions are typically
established by geometric criteria. Most typical examples are
cyclopalladated azobenzenes;65–67 recently we described the
first examples of π-interactions between a chelate ring and a
quinoid ring.18 However, these are more similar to aromatic
stacks68,69 than quinoid stacks.19,70
IR data (KBr, cm−1): ˜ν = 3420 (s, br), 1646 (m), 1637 (w),
1615 (m), 1589 (w), 1543 (vs), 1517 (vs), 1475 (sh), 1458 (w),
1429 (m), 1373 (s), 1344 (m), 1331 (w), 1312 (w), 1267 (w),
1255 (sh), 1224 (w), 1149 (w), 1110 (w), 1050 (w), 999 (w),
877 (w), 845 (s), 775 (w), 742 (w), 721 (m), 668 (w), 652 (w),
602 (m), 573 (m), 435 (w), 419 (w).
Preparation of [Cu(CA)(phen)(C2H5OH)] (3). Aqueous
solutions of CuCl2·2H2O (17.7 mg; 0.1 mmol; 3 mL) and 1,10-
phenanthroline (19.9 g; 0.1 mmol; 3 mL) were mixed by
heating. The resulting solution was put into a test tube. Next,
an ethanol solution (8 mL) of H2CA (21.0 mg; 0.1 mmol) was
carefully laid above. X-ray-quality dark violet needle-like single
crystals of 3 were formed after two weeks. The yield was ∼57%.
Anal. Calcd for C18H8Cl2CuN2O4 (Mr = 450.72): C 47.96, H 2.85,
N 5.64%; found: C 45.20, H 2.34, N 5.83%.
IR data (KBr, cm−1): ˜ν = 3394 (m, br), 1648 (m), 1632 (w),
1614 (m), 1587 (w), 1541 (vs), 1526 (s), 1515 (vs), 1431 (m),
1374 (s), 1346 (m), 1330 (m), 1312 (sh), 1266 (w), 1225 (w),
1210 (sh), 1160 (sh), 1149 (w), 1110 (w), 1049 (w), 999 (w), 878
(w), 845 (s), 774 (w), 741 (w), 721 (m), 668 (w), 652 (w), 598 (m),
574 (m), 520 (w), 434 (w), 420 (w).
Experimental
Materials and physical measurements
The chemicals were purchased from commercial sources, and
Preparation of [Cu(CA)(phen)]·CH3OH (4). A hot aqueous
used without further purification. Infrared spectra were solution (3 mL) of 1,10-phenanthroline (19.9 mg; 0.1 mmol)
recorded by using KBr pellets with a Bruker Alpha FT-IR was added to an aqueous solution (4 mL) of H2CA (21.0 mg;
spectrometer, in the 4000–350 cm−1 region. Microanalysis was 0.1 mmol), followed by the appearance of thin dark needles,
performed on a Perkin Elmer 2400 Series II CHNS/O Analyzer that were removed by filtration (as detected spectroscopically,
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7208–7218 | 7215

View Article Online
Paper
Dalton Transactions
Table 6 Crystallographic, data collection and structure refinement details
Compound
1
2
3
4
Empirical formula
C
18H8Cl2CuN2O4
C36H22Cl4Cu2N4O11
955.49
C20H14Cl2CuN2O5
496.79
C31H30Cl2CuN4O5
662.98
Formula wt/g mol−1
450.72
Crystal dimensions/
0.25 × 0.12 × 0.07
0.20 × 0.18 × 0.02
0.22 × 0.10 × 0.05
0.16 × 0.10 × 0.06
mm
Space group
a/Å
b/Å
c/Å
α/°
P212121
7.44480(10)
13.1466(2)
16.0004(3)
90
P21
P21
C2/c
9.53230(10)
18.0066(2)
10.39350(10)
90
9.00760(10)
7.42350(10)
14.1624(2)
90
12.3532(6)
15.0096(7)
16.3027(8)
90
β/°
γ/°
90
90
96.8220(10)
90
90.8730(10)
90
111.011(6)
90
Z
4
2
2
4
V/Å3
1566.02(4)
1.912
5.399
4.35–75.74
293(2)
1771.35(3)
1.791
4.876
4.28–75.75
293(2)
946.90(2)
1.742
4.567
3.12–75.80
293(2)
2821.8(2)
1.561
3.255
4.84–75.75
293(2)
Dcalc/g cm−3
μ/mm−1
Θ range/°
T/K
Radiation wavelength 1.54179 (CuKα)
1.54179 (CuKα)
Xcalibur Nova
−11 < h < 7; −22 < k < 19;
−13 < l < 12
8683
1.54179 (CuKα)
Xcalibur Nova
−6 < h < 11; −9 < k < 8;
−17 < l < 17
4733
1.54179 (CuKα)
Xcalibur Nova
−15 < h < 15; −16 < k < 18;
−20 < l < 16
6044
Diffractometer type
Range of h, k, l
Xcalibur Nova
−9 < h < 6; −9 < k < 16;
−19 < l < 17
4842
Reflections collected
Independent
2853
5400
2775
2815
reflections
Observed reflections
(I ≥ 2σ)
Absorption correction Multi-scan
2771
5287
2724
2417
Multi-scan
0.0215
0.0273
0.0716
1.071
Mixed
534
Multi-scan
0.0212
0.0724
0.1997
1.137
Mixed
276
Multi-scan
0.0448
0.0467
0.1510
1.132
Mixed
207
Rint
0.0211
0.0303
0.0807
1.057
Constrained
245
R (F)
Rw (F2)
Goodness of fit
H atom treatment
No. of parameters
No. of restraints
Δρmax, Δρmin (e Å−3
0
11
3
9
)
0.403; −0.392
0.425; −0.453
1.219; −1.177
0.526; −0.637
the thin crystals contain phenanthroline and H2CA molecules, refined anisotropically. Hydrogen atoms bound to C atoms
but the crystals were not of the quality needed for X-ray analy- were modelled as riding entities using the AFIX command,
sis). The resulting violet solution was layered with a methanol while those bound to O were located in difference Fourier
solution (8 mL) of CuCl2·2H2O (17.1 mg; 0.1 mmol) in a test maps and refined with the following restraints: the geometry
tube. The reaction mixture was left to stand undisturbed for of water molecules was constrained to d(O–H) = 0.95(2) Å;
one week to yield X-ray-quality dark violet needle-like crystals d(H⋯H) = 1.50(4) Å, and the hydroxyl group to d(O–H) =
of 4. The yield was ∼10%.
0.82(2) Å.
IR data (KBr, cm−1): ˜ν = 3394 (m, br), 1647 (m), 1635 (w),
Methanol molecules in 4 are disordered, with the methyl
1614 (m), 1587 (w), 1541 (vs), 1526 (s), 1515 (vs), 1431 (m), carbon located on the twofold axis. Therefore, two sets of
1374 (s), 1346 (m), 1330 (m), 1312 (sh), 1266 (w), 1225 (w), hydroxy groups and methyl hydrogen atoms exist, with p.p.
1210 (sh), 1160 (sh), 1149 (w), 1110 (w), 1049 (w), 999 (w), 0.5. However, the geometry of the methanol molecule is not
879 (w), 845 (s), 774 (w), 741 (w), 721 (m), 668 (w), 652 (w), realistic due to the disorder.
598 (m), 574 (m), 520 (w), 434 (w), 419 (w).
Molecular geometry calculations were performed by
PLATON,73 and the molecular graphics were prepared using
ORTEP-374 and CCDC-Mercury.75 Crystallographic and refine-
ment data for the structures reported in this paper are shown
in Table 6.
Crystallography
Single crystal measurements were performed on an Oxford
Diffraction Xcalibur Nova R (microfocus Cu tube) instrument
at room temperature (293(2) K). Only the symmetry-indepen-
dent part of the Ewald sphere was measured; no Friedel pairs
were measured in the case of non-centrosymmetric crystals.
The CrysAlis PRO71 program package was used for data
reduction. The structures were solved using SHELXS9772 and
CCDC 973343–973346 contain the supplementary crystallo-
graphic data for this paper.
Conclusions
refined with SHELXL97.72 Models were refined using the full- In mixed ligand complexes of CuII comprising chloranilate
matrix least squares refinement; all non-hydrogen atoms were and phen ligands, square-pyramidal coordination is predomi-
7216 | Dalton Trans., 2014, 43, 7208–7218
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
nant. In a single case is an octahedral coordination found. The 13 L. Androš, M. Jurić, J. Popović, A. Šantić, P. Lazić,
N,N-ligand binding of phen has a significant impact on the
occurrence of mononuclear species. Chloranilate coordinates
M. Benčina, M. Valant, N. Brničević and P. Planinić, Inorg.
Chem., 2013, 52, 14299.
in a terminal bidentate ortho-quinone-like mode, also support- 14 M. Jurić, P. Planinić, N. Brničević, D. Milić, D. Matković-
ing the formation of mononuclear species. However, in
addition to this predominant mode of coordination, a brid-
Čalogović, D. Pajić and K. Zadro, Eur. J. Inorg. Chem., 2006,
2701.
ging monodentate mode of chloranilate is encountered in 1; 15 M. Jurić, B. Perić, N. Brničević, P. Planinić, D. Pajić,
the long Cu–O bridging bond of 2.574(2) Å connects complex K. Zadro and G. Giester, Polyhedron, 2007, 26, 659.
molecules into the polymeric coordination chain. The spectro- 16 M. Jurić, B. Perić, N. Brničević, P. Planinić, D. Pajić,
scopic IR data are in a good agreement with the structures
described.
K. Zadro, G. Giester and B. Kaitner, Dalton Trans., 2008,
742.
The crystal packing of the structures described here is 17 L. Androš, M. Jurić, K. Molčanov and P. Planinić, Dalton
controlled by hydrogen bonding and π-interactions (Tables 4 Trans., 2012, 41, 14611.
and 5). Predominant π-interactions in 1 include those of 18 K. Molčanov, M. Jurić and B. Kojić-Prodić, Dalton Trans.,
five-membered chelate rings and π-systems of the ligands 2013, 42, 15756.
(chloranilate and aromatic phen rings) in a near face-to-face 19 K. Molčanov, B. Kojić-Prodić, D. Babić and J. Stare,
arrangement (no offset and very small tilt angles between CrystEngComm, 2013, 15, 135.
stacked rings, Table 4). In the crystal packing of 4, the octa- 20 K. Molčanov, B. Kojić-Prodić, D. Babić, D. Pajić, N. Novosel
hedra connected by hydrogen bonds built a porous network
filled by disordered methanol solvate molecules.
and K. Zadro, CrystEngComm, 2012, 14, 7958.
21 Y. Shuku, R. Suizu, A. Domingo, C. J. Calzado, V. Robert
and K. Awaga, Inorg. Chem., 2013, 52, 9921.
22 J. S. Miller, Chem. Soc. Rev., 2011, 40, 3266.
23 N. A. Spaldin and M. Fiebig, Science, 2005, 309, 391.
24 K. Molčanov, D. Babić, B. Kojić-Prodić, J. Stare, N. Maltar-
Strmečki and L. Androš, Acta Crystallogr., Sect. B: Struct.
Sci., 2014, 70, 181.
Acknowledgements
This work was supported by the Ministry of Science, Education
and Sports of Croatia (grants no. 098-1191344-2943 and
098-0982904-2946) and the Croatian Academy of Sciences and 25 K. Molčanov, B. Kojić-Prodić and A. Meden, Croat. Chem.
Arts (grant for 2013).
Acta, 2009, 82, 387.
26 K. Wallenfels and K. Friedrich, Chem. Ber., 1960, 93, 3070.
27 S. Kitagawa and S. Kawata, Coord. Chem. Rev., 2002, 224,
11.
28 S. Kitagawa and R. Matsuda, Coord. Chem. Rev., 2007, 251,
2490.
Notes and references
1 V. Podzorov, Nat. Mater., 2010, 9, 616.
2 S. Sanvito, Chem. Soc. Rev., 2011, 40, 3336.
3 S. Sanvito, Nat. Mater., 2011, 10, 484.
29 D. F. Xiang, C. Y. Duan, X. S. Tan, Y. J. Liu and W. X. Tang,
Polyhedron, 1998, 17, 2647–2653.
4 I. Ratera and J. Veciana, Chem. Soc. Rev., 2012, 41, 303.
5 Y. Morita, S. Suzuki, K. Sato and T. Takui, Nat. Chem., 2011,
3, 197.
6 R. G. Hicks, Nat. Chem., 2011, 3, 189.
7 M. Jurić, P. Planinić and N. Brničević, Niobium in Oxalate
30 S. Kawata, S. Kitagawa, M. Kondo, I. Furuchi and
M. Munakata, Angew. Chem., Int. Ed. Engl., 1994, 33, 1759.
31 S. Kawata, S. Kitagawa, H. Kumagai, C. Kudo, H. Kamesaki,
T. Ishiyama, R. Suzuki, M. Kondo and M. Katada, Inorg.
Chem., 1996, 35, 4449.
Complexes: From Discrete Molecules to Heterometallic 32 S. Kawata, S. Kitagawa, H. Kumagai, T. Ishiyama, K. Honda,
Supramolecular Structures, in Niobium: Properties, Pro-
duction and Applications, ed. T. M. Wong, Nova Science Pub-
lishers, Hauppauge, NY, USA, 2011.
H. Tobita, K. Adachi and M. Katada, Chem. Mater., 1998,
10, 3902.
33 S. Kawata, H. Kumagai, K. Adachi and S. Kitagawa, J. Chem.
Soc., Dalton Trans., 2000, 2409.
8 R. Lescouezec, L. M. Toma, J. Vaissermann, M. Verdaguer,
F. S. Delgado, C. Ruiz-Perez, F. Lloret and M. Julve, Coord. 34 B. F. Abrahams, J. Coleiro, K. Ha, B. F. Hoskins,
Chem. Rev., 2005, 249, 2691.
S. D. Orchard and R. Robson, J. Chem. Soc., Dalton Trans.,
9 C. Yuste, L. Canadillas-Delgado, A. Labrador, F. S. Delgado,
2002, 1586.
C. Ruiz-Perez, F. Lloret and M. Julve, Inorg. Chem., 2009, 48, 35 A. Michaelides, Ch. D. Papadimitriou, J. C. Plakatouras,
6630. S. Skoulika and P. G. Veltsistas, Polyhedron, 2004, 23, 2587.
10 G. Marinescu, M. Andruh, F. Lloret and M. Julve, Coord. 36 M. K. Kabir, M. Kawahara, H. Kumagai, K. Adachi,
Chem. Rev., 2011, 255, 161.
11 J. Popović, M. Vrankić and M. Jurić, Cryst. Growth Des.,
2013, 13, 2161.
12 M. Jurić, J. Popović, A. Šantić, K. Molčanov, N. Brničević
and P. Planinić, Inorg. Chem., 2013, 52, 1832.
S. Kawata, T. Ishii and S. Kitagawa, Polyhedron, 2001, 20,
1417.
37 M. K. Kabir, N. Miyazaki, S. Kawata, K. Adachi,
H. Kumagai, K. Inoue, S. Kitagawa, K. Ijima and M. Katada,
Coord. Chem. Rev., 2000, 198, 157.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7208–7218 | 7217

View Article Online
Paper
Dalton Transactions
38 S. Liu, S. N. Shaikh and J. Zubieta, J. Chem. Soc., Chem. 56 N. Biliškov, B. Kojić-Prodić, G. Mali, K. Molčanov and
Commun., 1988, 1017. J. Stare, J. Phys. Chem. A, 2011, 115, 3154.
39 S. Liu, S. N. Shaikh and J. Zubieta, Inorg. Chem., 1989, 28, 57 K. Nakamoto, Infrared and Raman Spectra of Inorganic and
723.
Coordination Compounds, John Wiley, New York, 6th edn,
40 M. Kawahara, Md. K. Kabir, K. Yamada, K. Adachi,
2009.
H. Kumagai, Y. Narumi, K. Kindo, S. Kitagawa and 58 H. Masui, Coord. Chem. Rev., 2001, 219–221, 957.
S. Kawata, Inorg. Chem., 2004, 43, 92.
41 P. G. Smes and G. Yahioglu, Chem. Soc. Rev., 1994, 23, 327.
59 M. K. Miličić, B. D. Ostojić and S. D. Zarić, Inorg. Chem.,
2007, 46, 7109.
42 A. Bencini and V. Lippolis, Coord. Chem. Rev., 2010, 254, 60 M. Pitonak, P. Neogrady, J. Rezac, P. Jurecka, M. Urban and
2096. P. Hobza, J. Chem. Theory Comput., 2008, 4, 1829.
43 G. Roelfs and B. L. Feringa, Angew. Chem., Int. Ed., 2005, 61 D. N. Sredojević, D. Z. Vojisavljević, Z. D. Tomić and
44, 3230.
S. Zarić, Acta Crystallogr., Sect. B: Struct. Sci., 2012, 68,
261.
62 The Importance of Pi-Interactions in Crystal Engineering, ed.
E. R. T. Tiekink and J. Zukerman-Schpector, Wiley & Sons,
Inc., New York, 2012.
44 G. Accorsi, A. Listorti, K. Yoosaf and N. Armaroli, Chem.
Soc. Rev., 2009, 38, 1690.
45 H. Niyazi, J. P. Hall, K. O’Sullivan, G. Winter, T. Sorensen,
J. M. Kelly and C. Cardin, Nat. Chem., 2012, 4, 621.
46 H. Song, J. T. Kaiser and J. K. Barton, Nat. Chem., 2012, 4, 63 C. Janiak, J. Chem. Soc., Dalton Trans., 2000, 3885.
615.
64 C. R. Martinez and B. L. Iverson, Chem. Sci., 2012, 3,
2191.
65 M. Ghedini, I. Aiello, A. Crispini, A. Golemme, M. La Deda
and D. Pucci, Coord. Chem. Rev., 2006, 250, 1373.
47 K. Gislason and S. T. Sigurdsson, Eur. J. Org. Chem., 2010,
4713.
48 B. Cordero, V. Gómez, A. E. Platero-Prats, M. Revés,
J. Echeverría, E. Cremades, F. Barragán and S. Alvares, 66 K. Molčanov, M. Ćurić, D. Babić and B. Kojić-Prodić,
Dalton Trans., 2008, 2832. J. Organomet. Chem., 2007, 692, 3874.
49 F. H. Allen, Acta Crystallogr., Sect. B: Struct. Sci., 2002, 58, 67 H. Masui, Coord. Chem. Rev., 2001, 219–221, 957.
380–388.
68 C. A. Hunter and J. K. M. Sanders, J. Am. Chem. Soc., 1990,
112, 5525.
69 C. A. Hunter, K. R. Lawson, J. Perkins and C. J. Urch,
J. Chem. Soc., Perkin Trans. 2, 2001, 651.
70 K. Molčanov, B. Kojić-Prodić and I. Sabljić, CrystEngComm,
2011, 13, 4211.
71 CrysAlisPRO, Oxford Diffraction Ltd, U.K., 2007.
50 O. Castillo, A. Luque, J. Sertucha, P. Román and F. Lloret,
Inorg. Chem., 2000, 39, 6142.
51 O. Castillo, A. Luque, S. Iglesias, C. Guzmán-Miralles and
P. Román, Inorg. Chem. Commun., 2001, 4, 640.
52 H. Núñez, J.-J. Timor, J. Server-Carrió, L. Soto and
E. Escrivà, Inorg. Chim. Acta, 2001, 318, 8.
53 Molecular Machines and Motors, ed. J. P. Sauvage, Springer 72 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crystal-
Verlag, Berlin, 2001, p. 61. logr., 2008, 64, 112.
54 D. Cremer and J. A. Pople, J. Am. Chem. Soc., 1975, 97, 73 A. L. Spek, J. Appl. Crystallogr., 2003, 36, 7.
1354. 74 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
55 R. M. Silverstein, C. G. Bassler and T. C. Morrill, Spectro- 75 C. F. Macrae, P. R. Edgington, P. McCabe, E. Pidcock,
metric Identification of Organic Compounds, John Wiley &
G. P. Shields, R. Taylor, M. Towler and J. van de Streek,
Sons, Inc., New York, 3rd edn, 1974.
J. Appl. Crystallogr., 2006, 39, 453.
7218 | Dalton Trans., 2014, 43, 7208–7218
This journal is © The Royal Society of Chemistry 2014