Coordination and inclusion compounds formed by addition of quinoline (Q) or isoquinoline (Iq) to a metal(II) dibenzoylmethanate (Co, Ni, Zn, Cd): Composition, structure and thermal dissociation properties

Article abstract of DOI:10.1007/s10973-010-0689-9

Three isomorphous series of new compounds are reported: complexes [M(DBM)₂Q₂] and [M(DBM)₂Iq₂] (M = M(II) = Co, Ni, Zn, Cd; DBM is C₆H₅COCH-COC ₆H₅^-) and inclusion compounds [M(DBM) ₂Q₂]^*Q (M = Co, Zn, Cd). All the compounds comprise a trans configured octahedral complex molecule. Inclusion compounds of modified Zn and Cd DBM complexes are reported for the first time and their inclusion ability is attributed to the trans isomeric state induced by the bulky Q or Iq ligand. The TG measurements indicate the following order of thermal stability of the complexes defined by the strength of the metal-ligand bonds: Ni >Co >Cd >Zn. The inclusion compounds do not follow this trend. Akademiai Kiado, Budapest, Hungary 2010.

Full text of DOI:10.1007/s10973-010-0689-9

J Therm Anal Calorim (2010) 100:801–810
DOI 10.1007/s10973-010-0689-9
Coordination and inclusion compounds formed by addition
of quinoline (Q) or isoquinoline (Iq) to a metal(II)
dibenzoylmethanate (Co, Ni, Zn, Cd)
Composition, structure and thermal dissociation properties
•
E. B. Okeke D. V. Soldatov
CTAS2009 Special Chapter
´
´
Ó Akademiai Kiado, Budapest, Hungary 2010
Abstract Three isomorphous series of new compounds
are reported: complexes [M(DBM)2Q2] and [M(DBM)2Iq2]
(M = M(II) = Co, Ni, Zn, Cd; DBM is C6H5COCH-
COC6H5-) and inclusion compounds [M(DBM)2Q2]*Q
(M = Co, Zn, Cd). All the compounds comprise a trans
configured octahedral complex molecule. Inclusion com-
pounds of modified Zn and Cd DBM complexes are reported
for the first time and their inclusion ability is attributed to the
trans isomeric state induced by the bulky Q or Iq ligand. The
TG measurements indicate the following order of thermal
stability of the complexes defined by the strength of the
metal–ligand bonds: Ni [ Co [ Cd [ Zn. The inclusion
compounds do not follow this trend.
formulations of pharmaceuticals [14] and design of
bio-mimetic systems [15]. One of the most significant future
applications of inclusion compounds is their use as materials
that can reversibly change their structure and properties in
the process of guest inclusion, the change being reproduc-
ible and individual for each particular guest [16–18].
Crystalline inclusion compounds have a crystal lattice
built by the molecules of host, while the molecules of guest
reside in the cavities of this lattice. No chemical bonds
exist between host and guest; the solid is stabilized by
favorable non-covalent interactions. The utilization of
metal complexes as hosts is very convenient as whole
series of new host molecules may be created by varying
metal center and ligands in the complex formula [19].
Molecular host complexes as well as their inclusion com-
pounds readily form and dissociate. Therefore, their syn-
thesis can be well controlled thermodynamically, while
thermal dissociation can be used to examine their stability
and other fundamental parameters [20–23].
Keywords Metal complexes ꢀ Molecular crystals ꢀ
Clathrates ꢀ DBM ꢀ Cis–trans isomerism ꢀ
Thermal analysis ꢀ Stability
Introduction
Our recent studies concentrated on a new type of host com-
plexes, modified metal dibenzoylmethanates, [M(DBM)2A2],
-
where DBM = C6H5COCHCOC6H5 , dibenzoylmethanate-
The design and studies of new inclusion compounds
(clathrates) is a major direction in supramolecular chemistry
and crystal engineering [1–3]. Current and potential appli-
cations of inclusion compounds are numerous: encapsula-
tion, storage, and controlled release of gases [4, 5] and
flavors [6]; separation, purification, and specific nano-
confined reactions of chemicals [7–11]; design of highly
selective chemical sensors [12, 13]; creation of new
anion, and M = M(II) [24–32]. Several axial ligands A, such as
pyridine, were utilized to yield a family of host molecules with
so-called humming-top overall geometry [19]. In order to
maintain such geometry, the complex must have trans configu-
ration as shown in Fig. 1. After structural elucidation of the
complexes and their inclusion compounds we became interested
in better understanding what factors define the stability of these
solid materials. In particular, we are interested in the role of the
metal center.
In our previous studies on another type of hosts, Werner
complexes, we succeeded in preparing several series of
isostructural inclusions dissociating in a similar way and
differing only by the metal center in the host complex in
E. B. Okeke ꢀ D. V. Soldatov (&)
Department of Chemistry, University of Guelph,
50 Stone Rd. E, Guelph, ON N1G 2W1, Canada
e-mail: dsoldato@uoguelph.ca
123

802
E. B. Okeke, D. V. Soldatov
Experimental
A
M
A
Preparations
N
M
N
N
M
N
O
O
O
O
O
O
O
O
O
O
O
O
Metal dibenzoylmethanates M(DBM)2 were synthesized as
described elsewhere [24, 49]. Complexes were prepared by
adding 125–140 mg (0.25 mmol) of the corresponding
M(DBM)2, 78 mg (0.6 mmol) of quinoline or isoquinoline
and an excess of solvent (3 ml or more if necessary). The
mixtures were transformed into transparent solutions by
heating (red, green, or colorless), filtered if needed, and
then allowed to slowly cool down to room temperature.
Typically the products were recovered the next day. If no
solid formed, the solutions were allowed to evaporate.
All products were crystalline. Typical yields were from
50 to 80%. Co compounds were orange, Ni compounds
were green, Zn and Cd compounds were colorless. For TG
and other experiments, the crystals were pressed to dryness
on filter paper and then dried for *1 h. All products were
stable in air for days. For single crystal XRD measurements
crystals were taken directly from mother solutions.
For each of four metal DBMs and quinoline, eight
solvents were applied: acetone, benzene, DMSO, ethanol,
nitromethane, THF, toluene, and neat quinoline. Com-
plexes [M(DBM)2Q2] obtained from non-quinoline sol-
vents grew as plates. Identity of the products formed from
different solvents was confirmed by powder XRD analysis.
The inclusions [M(DBM)2Q2]*Q obtained from quinoline
grew up as prisms for Co, Zn, and Cd. Numerous crystal-
lizations of Ni(DBM)2 from neat quinoline always yielded
only [Ni(DBM)2Q2] complex.
[M(DBM)2A2]
[M(DBM)2Q2]
[M(DBM)2lq2]
Fig. 1 Molecular structure of a modified metal DBM (left) and
complexes specifically studied in this work
each of the series. Thermal analysis and equilibrium vapor
pressure studies were very helpful in explaining the ther-
modynamic parameters of the inclusion/dissociation pro-
cess and factors defining the limits of existence for those
solid materials [21, 31–36].
So far we were not able to prepare such a series for metal
DBMs. It turned out that the complexes of Zn(II) and Cd(II)
usually adopt cis configuration and differ in their properties
from complexes formed by metal cations with partially filled
d subshell. In the series of three [M(DBM)2Py2] complexes
(Py = pyridine) only Ni complex has trans configuration
and forms various inclusion compounds, while the corre-
sponding Zn and Cd complexes have cis configuration and
exist as guest-free solids [24]. With 2-methylpyridine as A,
Ni complex again is trans and versatile as host, while the
corresponding Zn complex does not form at all and Cd
complex forms both trans and cis isomers, the cis isomer
being thermodynamically stable and guest-free [27]. Among
similar complexes studied by other authors [Ni(benzoyl-
acetone)2(DMSO)2], (DMSO = dimethylsulfoxide) [37]
and [Ni(benzoylacetone)2(adamantylamine)2] [38] both
reported as trans isomers may be compared with [Cd(DBM)2
(DMSO)2] which is cis [39].
For each of four metal DBMs and isoquinoline five
solvents were applied: acetone, benzene, DMSO, nitro-
methane, and neat isoquinoline. Complexes [M(DBM)2Iq2]
obtained from the solvents grew either as plates or slanted
truncated blocks. Identity of the products formed from
different solvents was confirmed by powder XRD analysis
and/or single crystal XRD examination of randomly
selected crystals.
However, the energy difference between cis and trans
configurations does not seem to be very large for this type
of complexes. There are many examples when the same
complex was isolated in both trans and cis configurations
in different solids. For example [Zn(hfa)2(H2O)2] (hfa is
perfluorinated acetylacetonate) may be isolated both as
trans and as cis isomers [40]. Analogous Ni complex was
observed in both trans [41] and cis [42] forms; analogous
Co complex was also isolated in trans [43, 44] and in cis
[45] forms; finally, only cis isomer was reported for
[Cd(hfa)2(H2O)2] [46]. There are two examples when bis-
chelate complexes of Cd were isolated both as trans and cis
isomers related to each other as true polymorphs [47, 48].
In this study, we attempted to prepare and study a series
of host complexes of four metal DBMs (Co, Ni, Zn, Cd)
using bulky axial ligands, quinoline (Q), and isoquinoline
(Iq). These ligands would make cis configuration less
preferred due to sterical reasons and could favor the for-
mation of desired trans isomers for the whole series.
XRD studies
Powder XRD patterns were recorded on a STOE or Bruker
˚
D8 instruments with CuKa radiation (k = 1.5418 A) in
5–30° 2h range. No special precautions were taken to
protect the samples.
Single crystals, or pieces cut therefrom, were studied
on a Bruker diffractometer with Kappa goniometer,
˚
CCD detector and MoKa source (k = 0.7107 A). Unit cell
parameters were determined using 300–800 reflections
taken from several dozens of frames collected starting at
three different u positions. Some experimental parameters
and refined unit cell dimensions are listed in Table 1. Full
123

Coordination and Inclusion Compounds
803
diffraction data were collected at -100 °C and only pre-
liminary data are presented here; complete results of the
single crystal structural study will be reported elsewhere.
different molecular mass, the mass loss on the TG curves
was expressed as x, the ratio of moles of volatile compo-
nent (Q or Iq) per mole of M(DBM)2 in a compound
studied: x = (mexp - mref) 9 Mref/MQ 9 mref, where mexp
is the sample mass measured in a TG experiment, mref is
the mass of M(DBM)2 in the compound, Mref and MQ are
molecular masses of M(DBM)2 and Q, respectively. The
mref value is readily defined from the TG curve when the
plateau of M(DBM)2 is well pronounced. If the plateau is not
satisfactory, mref is calculated from initial mass assuming
certain stoichiometry. For another instance when the descri-
bed method was applied see our earlier paper [28].
Thermal analyses
Thermogravimetric measurements were conducted on a
Q5000 IR analyzer (TA Instruments). The samples varying
in mass (see Table 2) were heated in linear regime (5°/min)
and in the flow of nitrogen (25 mL/min) from room tem-
perature to *400 °C. Samples were gently grounded to
achieve uniform distribution of heat.
In order to reduce the dependence of the quantitative
measurements on texture and size of a sample, a variety of
independently prepared samples was analyzed. In particular,
the samples of complexes obtained from the different sol-
vents utilized were studied. The results are given with
standard deviations enclosed in round brackets and expres-
sed in the units of the last significant figure (Table 2).
As the purpose of this study was to compare thermal
properties of compounds with different metals and
Results and discussion
Structure of the compounds isolated
The 11 compounds isolated and studied in this work fall
into three isomorphous series (Table 1):
Table 1 Single crystal XRD measurements of unit cell dimensions of the isolated compounds at room temperature
3
D
calc/g cm-3
˚
a/A
˚
b/A
b/°
˚
c/A
c/°
˚
V/A
Compound
Solvent used Crystal Crystal
description sizes/mm
No of
reflections a/°
used
Za
[Co(DBM)2Q2]
[Ni(DBM)2Q2]
[Zn(DBM)2Q2]
[Cd(DBM)2Q2]
Acetone
Red plate
0.1 9 0.5 9 0.5
796
10.390(5) 16.673(7) 22.32(1) 3867(3) 1.312
90 90 90
10.321(6) 16.804(8) 22.25(1) 3859(3) 1.314
90 90 90
10.394(5) 16.765(7) 22.26(1) 3879(3) 1.319
90 90 90
11.048(5) 17.869(7) 20.356(9) 3946(3) 1.375
100.26(1) 93.18(1) 91.19(1)
9.280(4) 9.428(4) 13.380(5) 1134(1) 1.308
83.86(2) 88.53(2) 76.90(2)
9.302(6) 9.349(6) 13.328(9) 1122(1) 1.331
83.86(1) 88.51(1) 76.85(1)
9.397(7) 9.164(6) 13.85(1) 1158(1) 1.358
84.03(1) 88.62(1) 77.36(1)
17.66(1) 11.192(7) 20.96(1) 3868(4) 1.312
90 111.00(2) 90
17.81(1) 11.012(6) 20.99(1) 3833(4) 1.323
90 111.38(1) 90
17.60(1) 11.244(6) 20.76(1) 3835(4) 1.334
90 111.02(1) 90
17.078(7) 11.866(5) 20.01(1) 3824(3) 1.420
90 109.44(2) 90
4
Nitromethane Green plate 0.02 9 0.3 9 0.3 550
4
Nitromethane Colorless
plate
0.3 9 0.4 9 0.4
0.3 9 0.4 9 0.5
729
750
4
Toluene
Colorless
plate
4
[Co(DBM)2Q2]*Q Quinoline
[Zn(DBM)2Q2]*Q Quinoline
[Cd(DBM)2Q2]*Q Quinoline
Orange
prism
0.05 9 0.05 9 0.2 137
0.35 9 0.4 9 0.5 467
1
Colorless
prism
1
Colorless
prism
0.2 9 0.3 9 0.4
575
1
[Co(DBM)2Iq2]b
[Ni(DBM)2Iq2]b
[Zn(DBM)2Iq2]b
[Cd(DBM)2Iq2]b
Nitromethane Orange
plate
0.02 9 0.5 9 0.5 349
4
Isoquinoline Green
plate
0.1 9 0.2 9 0.4
0.5 9 0.5 9 0.5
0.4 9 0.5 9 0.5
462
476
689
4
Ethylacetate
Colorless
block
4
Isoquinoline Colorless
block
4
a
Assumed value
b
C-cell
123

804
E. B. Okeke, D. V. Soldatov
Table 2 The parameters of thermal dissociation of studied compounds as derived from TG experiments: average values with standard deviations
Compound
No of samples
studieda
Sample mass
range/mg
T
onset/°C
Mass loss/%
Calc. mass loss/%
Model
Co(DBM)2
1
5.7
*280e
*293e
*266e
*252e
150(2)
154(2)
96(1)
124(1)
89
–
–
(dec.)
(dec.)
(dec.)
(dec.)
-2Q
Ni(DBM)2
1
4.1
–
–
Zn(DBM)2
1
4.6
–
–
Cd(DBM)2
1
5.8
–
–
[Co(DBM)2Q2]
[Ni(DBM)2Q2]
[Zn(DBM)2Q2]
[Cd(DBM)2Q2]
[Co(DBM)2Q2]*Q
[Zn(DBM)2Q2]*Q
[Cd(DBM)2Q2]*Q
[Co(DBM)2Iq2]
[Ni(DBM)2Iq2]
[Zn(DBM)2Iq2]
[Cd(DBM)2Iq2]
a
7b
7b
7b
7b
1
0.4–6.3
2.8–6.0
3.8–10.0
1.6–7.5
5.1
34.6(3)
34.8(2)
33.9(1)
31.7(1)
43.6
33.8
33.8
33.5
31.6
43.4
43.1
40.9
33.8
33.8
33.5
31.6
-2Q
-2Q
-2Q
-3Q
1
4.6
66
43.1
-3Q
1
7.8
103
40.7
-3Q
4c
3d
4c
4c
1.2–6.2
2.5–4.3
5.3–7.3
4.3–7.1
142(3)
155(1)
107(1)
125(2)
34.2(2)
28–31.5f
33.8(1)
32.1(1)
-2 Iq
-2 Iq
-2 Iq
-2 Iq
Independently prepared samples
b
c
d
e
f
Crystals obtained from acetone, benzene, DMSO, ethanol, nitromethane, THF, and toluene
Crystals obtained from acetone, benzene, DMSO, and nitromethane
Crystals obtained from acetone, DMSO, and nitromethane
Broad onset
The plateau of Ni(DBM)2 is not well defined on the thermograms
Â
Â
Â
Ã
Ã
Inclusion compounds with an organic molecule playing the
role of both a ligand and guest are common [21, 34–36,
50–58] and, in the cases where the guest molecule is
included only due to van der Waals forces, it may be
replaced with another molecule that is chemically different
but possesses similar shape and dimensions [59, 60].
Compounds [Ni(DBM)2Iq2] are monoclinic (C2/c) and
isostructural. The crystal consists of trans (centrosymmetric)
complex molecules (Fig. 2c).
MðDBMÞ2Q2 ; where M ¼ Co; Ni; Zn; Cd;
MðDBMÞ2Q2 *Q; where M ¼ Co; Zn; Cd;
Ã
MðDBMÞ2Iq2 ; where M ¼ Co; Ni; Zn; Cd:
Compounds [M(DBM)2Q2] are orthorhombic and iso-
structural except for Cd-complex which, evidently, has a
similar structure distorted to triclinic. Preliminary single
crystal XRD studies indicate that the first three compounds
crystallize in space group Pcab with trans [M(DBM)2Q2]
complex molecules (centrosymmetric) (Fig. 2a). The
Cd-compound is similar but crystallizes in P–1 with three
crystallographically different molecules in the unit cell
(two are centrosymmetric and one is asymmetric).
One can immediately see the similarity of the complex
molecules observed in the studied structures (Fig. 2). All
possess trans configuration with two DBMs forming a bis-
chelate unit in the equatorial plane and two Q or Iq ligands
coordinated axially. The coordination environment is thus a
slightly distorted octahedral. For instance, in Zn complexes
Compounds [M(DBM)2Q2]*Q are triclinic (P–1) and
isostructural with each other. The crystal structure com-
˚
the Zn–O distance varies within 2.04–2.09 A, the Zn–N
˚
distance varies within 2.19–2.30 A and coordination angles
prises
a centrosymmetric trans [M(DBM)2Q2] host
complex (Fig. 2b) and a molecule of guest quinoline. The
molecule of the host complex adopts a very similar con-
formation as in guest-free crystals (cf. Fig. 2a, b). The
molecules of guest quinoline are retained inside cavities of
the crystal lattice and form only van der Waals contacts to
other molecules of the crystal structure (Fig. 3). Therefore,
the crystals are inclusion compounds, where two moles of
quinoline are incorporated as ligands in the host molecule
and one extra mole of quinoline is included as guest.
are in the range 86°–94°. The conformations of the mole-
cules are also quite similar. The phenyl rings of the DBM
units rotate from the equatorial planes by 13–30°. The
plane of Q or Iq forms 80–86° dihedral angle with the
equatorial plane. The Q ligand is almost in the plane
dividing the bis-chelate fragment into two DBMs, deviat-
ing from the plane by *12° and *6° in the guest-free and
inclusion crystals, respectively. This positioning is under-
standable from steric considerations as the only possibility
123

Coordination and Inclusion Compounds
805
Fig. 2 Molecules of Zn
(a)
(b)
complexes found in the crystal
structure of [Zn(DBM)2Q2] (a),
[Zn(DBM)2Q2]*Q (b), and
[Zn(DBM)2Iq2] (c). H-atoms are
omitted for clarity
(c)
ligands were used in the past to modulate properties of
known host complexes [61, 62] but in this study we use the
bulky ligands to endow complexes that do not have host
properties with inclusion capability. Second, the complexes
with quinoline do form inclusion compounds. The guest
quinoline can be replaced with other molecules. Our
ongoing studies yielded a series of such inclusions with
naphthalene, substituted benzenes, and cyclohexanes; this
work is currently underway. Third, the compounds isolated
in this study form three series with the same stoichiometry
and similar molecular and crystal structure in each of the
series and thus they are convenient objects for comparative
thermoanalytical studies.
c
b
Thermal stability and dissociation of the compounds
Fig. 3 Crystal packing in the inclusion compound [Zn(DBM)2Q2]*Q:
projection down the a axis. For clarity the host molecules are outlined
by sticks, while the guest molecules are shown in stick-and-balls.
H-atoms are omitted
TG results confirm stoichiometry of all the compounds
studied (as shown in Table 2). All the compounds contain
one volatile component (Q or Iq), while M(DBM)2 com-
plex salts have relatively high thermal stability and start to
decompose only after the volatile component has been
completely released (Table 2). Therefore, the TG curves
display a well-defined plateau of M(DBM)2 almost in all
experiments (Figs. 4, 5, 6). The presence of only one
volatile component makes TG results unambiguous and
useful for the determination of stoichiometry of inclusion/
coordination compounds and identification of the products
for the bulky Q moiety to approach the coordination center.
The Iq ligand is less restricted and rotates from the plane by
*20°.
The main results of the structural studies are the fol-
lowing. First, the complex molecules in the isolated crys-
tals are all trans. Therefore, the utilization of bulky ligands
helped to produce trans complexes that are more likely to
form inclusion compounds. It should be noted that big
123

806
E. B. Okeke, D. V. Soldatov
of their thermal dissociation [21, 34, 36, 63–68]. Although
closer look reveals that the stoichiometry of intermediate
states in some cases is irregular, the total amounts of
released Q or Iq correspond well to the values calculated
from the formulas (Table 2; Figs. 4, 5, 6). It should be
noted that irregular stoichiometries have been observed in
thermal dissociation of complexes with quinoline and other
bulky ligands [64–68] and may indicate either solid-state
chemical transformations or the formation of a liquid phase
in the sample.
[M(DBM)2lq2]
2
1
0
M(DBM)2lq
M(DBM)2
Co
Ni
Zn
Cd
[M(DBM)2Q2]
100
400
200
0
300
2
Temperature/°C
Fig. 6 Thermal dissociation of [M(DBM)2Iq2] complexes (see
comments to Fig. 4)
M(DBM)2Q
1
Qualitative consideration reveals a one-step dissociation
mode for most complexes:
M(DBM)2
0
Â
Ã
Co
MðDBMÞ2Q2 ! MðDBMÞ2þ2Q" ðM ¼ Co; Ni; ZnÞ
MðDBMÞ2Iq2 ! MðDBMÞ2þ2Iq" ðM ¼ Co; Zn; CdÞ
Ni
Zn
Cd
Â
Ã
100
400
200
0
300
Among inclusions, only the Co-compound dissociates
exhibiting a clear plateau of the corresponding host
complex:
Temperature/°C
Fig. 4 Thermal dissociation of [M(DBM)2Q2] complexes. For easier
comparison, the graphs show the ratio x = Q: M(DBM)2 in the
compound (for further explanation see ‘‘Experimental’’). Calculated
compositions are shown by dashes. Symbols on the curves are added
to distinguish curves belonging to different compounds
Â
Ã
Â
Ã
CoðDBMÞ2Q2 *Q ! CoðDBMÞ2Q2 þ Q"
For the Zn-compound, the plateau is barely pronounced.
The dissociation curve of Cd-compound is complicated due
to melting of [Cd(DBM)2Q2]*Q and [Cd(DBM)2Q2] at 120
and 157 °C (DSC results), respectively.
[M(DBM)2Q2]*Q
3
The comparison of thermal stability is useful in series of
stoichiometrically similar compounds undergoing the same
kind of dissociation reaction. The order of thermodynamic
stability can be estimated in such studies taking into
account that major contributors to the difference in ther-
modynamic stability are the volatility of the released
component and how strongly the volatile component is
retained in the solid. For coordination compounds (volatile
component is a ligand), the second parameter is defined
mainly by the enthalpy term, which is the strength of the
coordination bond. For inclusion compounds (volatile
component is a guest), the enthalpy contribution to the
second parameter is defined by the complementarity of the
guest molecule to the cavity in the host lattice. More
extended discussion on the subject was given elsewhere
[28, 69–71]. However, inclusion compounds usually dem-
onstrate the compensation effect [72–78] and inclusion
compounds with guest occupying larger cavities gain in
stability due to higher entropy. The stability of inclusion
compounds based on metal complexes may be also limited
[M(DBM)2Q2]
2
M(DBM)2Q
1
M(DBM)2
0
Co
Zn
Cd
100
400
200
0
300
Temperature/°C
Fig. 5 Thermal dissociation of [M(DBM)2Q2]*Q inclusion com-
pounds (see comments to Fig. 4)
123

Coordination and Inclusion Compounds
807
by the strength of coordination bonds in the host complex if
it is not sufficiently stable [34–36].
Conclusions
In this study, the comparison can be made using the
onset temperatures of the initial dissociation step in series
of isomorphous compounds. The comparison is based on
the assumption that at the beginning the dissociation pro-
cesses are similar and not complicated by melting or other
events. In both [M(DBM)2Q2] and [M(DBM)2Iq2] series,
the order of stability is
This study introduces bulky quinoline and isoquinoline
ligands in the modified M(DBM)2 unit to yield two series
of complexes (M = Co, Ni, Zn, and Cd). The special
choice of ligands made it possible to produce trans con-
figured complexes for Zn and Cd, with their overall
geometry being similar to the analogous complexes of Co
and Ni. For the first time, inclusion compounds of modified
Zn and Cd dibenzoylmethanates were prepared proving
that the inclusion ability of the host molecules is defined by
their overall shape rather than chemical nature of the metal
center. Therefore, appropriate choice of ligands may
become a useful strategy of generating host complexes for
metal cations which tend to exist in cis configuration
through stabilization of their corresponding trans isomers.
Moreover, the same strategy may become successful in
creating complexes with switchable cis–trans capability.
The phenomena of molecular and conformational isomer-
ism controlled by weak intermolecular interactions is fre-
quently encountered in molecular crystals [27, 40–45, 47,
48, 85–93] and may be utilized in the design of stimuli-
responsive materials [17].
Ni [ Co [ Cd [ Zn
The sequence is well defined and beyond experimental
errors (Table 2). The stabilities of M(DBM)2 clearly follow
the same trend (Table 2). The trend is defined by the rel-
ative strength of metal–ligand bonds and often seen in
other series of coordination compounds [79–83]; in many
such studies the thermal stability of coordination solids
correlates with the strength of the metal–ligand bonds
determined spectroscopically; although, the structural
similarity of the compounds was not always confirmed.
The onset temperatures of thermal dissociation of the host
complexes [M(DBM)2Q2] approximately define the limits of
thermal stability for the corresponding inclusion compounds
these complexes may form. The Co-, Cd-, and Zn-complexes
start to dissociate at 150, 124, and 96 °C, respectively
(Table 2). The dissociation of [M(DBM)2Q2]*Q inclusions
occurs at much lower temperature (89, 103, and 66 °C) and
so does not have to be affected by the stability of the host. It is
clear that the relative stability among the inclusion com-
pounds differs from that for host complexes. In particular, the
Cd-inclusion is the most stable. The released guest is the
same in the [M(DBM)2Q2]*Q series and therefore, as elab-
orated above, the stability difference should be a result of
host–guest interactions.
The trans complexes of Zn and Cd, as well as inclusion
compounds they form, compare to those of Co and Ni not
only structurally but also in terms of their bulk properties
such as thermal stability and dissociation. The differences
observed are rather quantitative than fundamental and
reasonable correlations can be observed throughout each of
the series. In overall, this study provides better under-
standing of the factors that on molecular level control the
formation and properties of inclusion materials.
Acknowledgements This study was financially supported by the
University of Guelph through a start-up grant and by the Natural
Sciences and Engineering Research Council through a Discovery
Grant and Research Tools and Equipment Grant. We thank G. D.
Enright and K. A. Udachin (Materials Structure and Function group at
SIMS NRC), and S. F. Kycia and A. Gomez (Department of Physics
at University of Guelph) for help with XRD measurements. We also
thank D. Ben-Israel (University of Guelph) for TG of metal DBMs.
The crystal structure analysis (at -100 °C) shows that
the cavity in Cd-inclusion is larger than in Co- and Zn-
compounds and only in the Cd-inclusion the guest in the
cavity is disordered over two positions. The unit cell
dimensions at room temperature (Table 2) suggest that the
tendency remains upon heating. Due to this disordering, the
dissociation reaction entropy change is lower in case of Cd-
inclusion (the guest in its cavities has already some dis-
order before entering gas phase) and the dissociation
temperature defined by T = DH/DS is higher. This way, the
disordering of guest extends the temperature limit of
existence of [Cd(DBM)2Q2]*Q inclusion. Similar phe-
nomenon was previously observed for inclusions that
experience polymorphous transitions due to order–disorder
change in the guest subsystem: the conversion into more
disordered phase reduces the temperature-caused growth of
guest vapor pressure over the clathrate thus making it
possible for the inclusion compound to exist at higher
temperatures [34, 84].
References
1. MacNicol DD, Toda F, Bishop R. Solid-state supramolecular
chemistry: crystal engineering. In: Atwood JL, Davies JED,
¨
MacNicol DD, Vogtle F, editors. Comprehensive supramolecular
chemistry, vol. 6. Oxford: Pergamon; 1996.
2. Dyadin YA, Terekhova IS, Rodionova TV, Soldatov DV. Half-
century history of clathrate chemistry. J Struct Chem. 1999;40:
645–53.
3. Soldatov DV, Terekhova IS. Supramolecular chemistry and
crystal engineering. J Struct Chem. 2005;46:S1–8.
4. Enright GD, Udachin KA, Moudrakovski IL, Ripmeester JA.
Thermally programmable gas storage and release in single
123

808
E. B. Okeke, D. V. Soldatov
crystals of an organic van der Waals host. J Am Chem Soc.
2003;125:9896–7.
5. Rudkevich DM. Progress in supramolecular chemistry of gases.
Eur J Org Chem. 2007;3255–70.
6. Madene A, Jacquot M, Scher J, Desobry S. Flavour encapsulation
and controlled release—a review. Int J Food Sci Technol. 2006;
41:1–21.
26. Soldatov DV, Ripmeester JA. Novel 4-vinylpyridine-extended
metal-dibenzoylmethanate host frameworks: Structure, polymor-
phism, and inclusion properties. Chem Eur J. 2001;7:2979–94.
27. Soldatov DV, Enright GD, Ratcliffe CI, Henegouwen AT,
Ripmeester JA. Inclusion potential, polymorphism, and molecular
isomerism of metal dibenzoylmethanates coordinated with
2-methylpyridine. Chem Mater. 2001;13:4322–34.
7. Toda F. Solid state organic chemistry: efficient reactions,
remarkable yields, and stereoselectivity. Acc Chem Res. 1995;28:
480–6.
28. Soldatov DV, Enright GD, Ripmeester JA. Inclusion ability of
4-phenylpyridine-extended nickel(II) dibenzoylmethanate, a new
metal-complex host. Chem Mater. 2002;14:348–56.
8. Bishop R. Designing new lattice inclusion hosts. Chem Soc Rev.
1996;25:311–9.
9. Nassimbeni LR. Physicochemical aspects of host–guest com-
pounds. Acc Chem Res. 2003;36:631–7.
29. Soldatov DV, Enright GD, Zanina AS, Sokolov IE. Stabilization
of guest-free forms of metal dibenzoylmethanate host type
through self-inclusion of a ligand fragment into the intramolec-
ular pocket. J Supramol Chem. 2002;2:441–8.
10. Seeber G, Tiedemann BEF, Raymond KN. Supramolecular chi-
rality in coordination chemistry. Top Curr Chem. 2006;265:
147–83.
11. Uemura T, Horike S, Kitagawa S. Polymerization in coordination
nanospaces. Chem Asian J. 2006;1:36–44.
12. Dickert FL, Haunschild A. Sensor materials for solvent vapor
detection—donor–acceptor and host–guest interactions. Adv
Mater. 1993;5:887–95.
13. Ziganshin MA, Yakimov AV, Konovalov AI, Antipin IS,
Gorbatchuk VV. Effect of the size of calixarene macrocycle on
the thermodynamic parameters of formation of inclusion com-
pounds in guest vapor–solid host systems. Russ Chem Bull.
2004;53: 1536–43.
14. Davis ME, Brewster ME. Cyclodextrin-based pharmaceuticals:
past, present and future. Nat Rev Drug Discov. 2004;3:1023–35.
15. Zhou H, Groves JT. Host–guest interactions of cyclodextrins and
metalloporphyrins: supramolecular building blocks toward artifi-
cial heme proteins. J Porphyrins Phthalocyanines. 2004;8:125–40.
16. Soldatov DV. Soft supramolecular materials. J Inclu Phenom.
2004;48:3–9.
17. Soldatov DV. Stimuli-responsive supramolecular solids: func-
tional porous and inclusion materials. In: Urban MW, editor.
Stimuli-responsive polymeric films and coatings. ACS Sympo-
sium Series, vol. 912. Washington: ACS; 2005. p. 214–31.
30. Soldatov DV, Ripmeester JA. Ladder-and-platform metal-organic
hosts: molecular and crystal structure of polymeric and dimeric
host complexes incorporating nickel(II) dibenzoylmethanate units
connected with 4,40-bipyridyl. Mendeleev Commun 2004;101–3.
31. Soldatov DV, Ukraintseva EA, Logvinenko VA. Structure and
stability of a clathrate of bis(dibenzoylmethanato)-dipyridine-
nickel(II) with acetone (1:2). J Struct Chem. 2007;48:938–48.
32. Ukraintseva EA, Soldatov DV. Vapour pressure of guest and
thermodynamic stability of inclusion compounds [Ni(DBM)2-
Py2]*2G (DBM = dibenzoylmethanate anion, G = pyridine,
tetrahydrofuran and chloroform). J Inclu Phenom, 2010 (in press).
33. Soldatov DV, Logvinenko VA, Dyadin YA, Lipkowski J,
Suwinska K. [MPy4(NCO)2]*2Py clathrates (M = M(II) = Mn,
Fe, Co, Ni, Cu, Zn, Cd; Py = pyridine). J Struct Chem. 1999;40:
757–71.
34. Soldatov DV, Ukraintseva EA, Logvinenko VA, Dyadin YA,
Grachev EV, Manakov AY. Thermodynamic dissociation con-
stants for [MPy4(NO3)2]*2Py clathrates (M = Mn, Co, Ni, Cu).
Supramol Chem. 2000;12:237–46.
35. Ukraintseva EA, Soldatov DV, Dyadin YA, Galkin PS, Mikheev
AN. Vapor pressures of the pyridine guest and the thermodynamic
parameters of dissociation of [MPy4(NCO)2]*2Py inclusion com-
pounds (M = Mn, Fe, Co, and Ni). Russ J Phys Chem. 2003;
77:1759–62.
ˇ
ˇ
ˇˇ ´
ˇ
´
´ ´
18. Friscic T, Mestrovic E, Samec DS, Kaitner B, Fabian L. One-pot
mechanosynthesis with three levels of molecular self-assembly:
coordination bonds, hydrogen bonds and host-guest inclusion.
Chem Eur J. 2009;15:12644–52.
36. Ukraintseva EA, Soldatov DV, Dyadin YA. Thermodynamic
stability of the [M(pyridine)4X2]*2G clathrates as a function of
the host components (M, X) and included guest (G). J Inclu
Phenom. 2004;48:19–23.
ˇ
ˇ
´
ˇ
19. Soldatov DV. Soft organic and metal-organic frameworks with
porous architecture: from wheel-and-axle to ladder-and-platform
design of host molecules. J Chem Crystallogr. 2006;36:747–68.
37. Mestrovic E, Halasz I, Bucar D-K, Zgela M. Bis(dimethyl sulf-
oxide-jO)bis(1-phenylbutane-1,3-dionato-j2O, O’)nickel(II). Acta
Crystallogr. 2004;E60:m367–9.
ˇ
´
´
ˇ
´
ˇ
20. Jona E, Simon P, Jorık V, Koman M. A thermochemical inves-
tigation of guest-host interactions in labile Werner clathrates of
the [Ni(4-EtPy)4(NCS)2]*G type (G = methyl derivatives of
benzene). Thermochim Acta. 1997;290:219–25.
38. Mestrovic E, Bucar D-K. Bis(adamantylamine-jN)bis(1-phen-
ylbutane-1,3-dionato-j2O, O’)nickel(II). Acta Crystallogr. 2005;E61:
m522–4.
ˇ
´
39. Halasz I, Horvat M, Biljan T, Mestrovic E. Structural, spectro-
scopic and thermal characterisation of bis(dibenzoylmethanato)
Cd(II) adducts with dimethylsulfoxide and water. J Chem Crys-
tallogr. 2008;38:793–800.
21. Logvinenko VA, Soldatov DV. Processes of thermal dissociation
of clathrates on the base of coordination compounds. J Therm
Anal Calorim. 1999;56:485–92.
22. Nassimbeni LR. Useful techniques in host-guest chemistry.
Supramol Chem. 2000;12:161–7.
23. Logvinenko V, Drebushchak V, Pinakov D, Chekhova G. Ther-
modynamic and kinetic stability of inclusion compounds under
heating. J Therm Anal Calorim. 2007;90:23–30.
40. Adams RP, Allen HC Jr, Rychlewska U, Hodgson DJ. The EPR
spectrum of Mn(II) doped into cis-diaquobis(1,1,1,5,5,5-hexa-
fluoroacetylacetonato)zinc(II) and trans-diaquobis(1,1,1,5,5,5-
hexafluoroacetylacetonato)zinc(II) and the crystal structure of the
host crystals. Inorg Chim Acta. 1986;119:67–74.
24. Soldatov DV, Enright GD, Ripmeester JA. Modified metal dib-
enzoylmethanates and their clathrates. Part I. Clathration ability
of dipyridinebis(dibenzoylmethanato)nickel(II), a novel metal-
complex host. Supramol Chem. 1999;11:35–47.
25. Soldatov DV, Ripmeester JA. 4-Vinylpyridine-modified nickel and
cobalt dibenzoylmethanates as new hosts: Inclusions with carbon
tetrachloride and chlorobenzene. Supramol Chem. 2001;12:
357–68.
41. Luneau D, Rey P, Laugier J, Belorizky E, Cogne A. Ferromag-
netic behavior of nickel(II)–imino nitroxide derivatives. Inorg
Chem. 1992;31:3578–84.
42. Romero RR, Cervantes-Lee F, Porter LC. Structure of cis-
diaquabis(hexafluoroacetylacetonato)nickel(II)]. Acta Crystal-
logr. 1992;C48:993–5.
43. Adams H, Bailey NA, Fenton DE, Khalil RA. Cis- and trans-
derived chain stacking in bis(hexafluoroacetylacetonato)metal(II)
123

Coordination and Inclusion Compounds
809
tetramethylpyrazine complexes. Inorg Chim Acta. 1993;209:
55–60.
59. Soldatov DV, Dyadin YA, Lipkowski J, Ogienko AG. Clath-
rates of the [Cu(pyridine)4(NO3)2]. Mendeleev Commum. 1997;
11–3.
`
44. Gulino A, Dapporto P, Rossi P, Fragala I. A novel self-generating
liquid MOCVD precursor for Co3O4 thin films. Chem Mater.
2003;15:3748–52.
45. Petrukhina MA, Henck C, Li B, Block E, Jin J, Zhang S-Z, et al.
Spirocyclic sulfur and selenium ligands as molecular rigid rods in
coordination of transition metal centers. Inorg Chem. 2005;44:
77–84.
60. Soldatov DV, Suwinska K, Lipkowski J, Ogienko AG. X-Ray
structural analysis of the dinitratotetrapyridinecopper(II) complex
and its clathrates with tetrahydrofuran and chloroform. J Struct
Chem. 1999;40:781–9.
ˇ
ˇ´
´
61. Miklovic J, Krutosıkova A, Baran P. Two furopyridine com-
plexes of nickel(II) isothiocyanate. Acta Crystallogr. 2004;C60:
m227–30.
`
46. Gulino A, Castelli F, Dapporto P, Rossi P, Fragala I. Synthesis
ˇ
ˇ
ˇ´
´
ˇ
´
and characterization of thin films of cadmium oxide. Chem
Mater. 2002;14:704–9.
62. Baran P, Boca M, Boca R, Krutosıkova A, Miklovic J, Pelikan J,
et al. Structural characterization, spectral and magnetic properties
of isothiocyanate nickel(II) complexes with furopyridine deriva-
tives. Polyhedron. 2005;24:1510–6.
47. Gao H-L, Cheng C, Ding B, Shi W, Song H-B, Cheng P, et al.
Hydrothermal synthesis of a series of novel cis- and trans-pydc
complexes with three-dimensional supramolecular architectures
(pydc = pyridine-2,5-dicarboxylic acid). J Mol Struct. 2005;738:
105–11.
48. Qian H, Huang W. Synthesis and structural characterization of cis-
and trans-bis(4,40-dimethyl-2,20-bipyridine)cadmium(II) nitrates
prepared in a one-pot reaction. Transit Met Chem. 2006;31:
347–52.
49. Soldatov DV, Henegouwen AT, Enright GD, Ratcliffe CI,
Ripmeester JA. Nickel(II) and zinc(II) dibenzoylmethanates:
molecular and crystal structure, polymorphism, and guest- or
temperature-induced oligomerization. Inorg Chem. 2001;40:
1626–36.
50. Soldatov DV, Lipkowski J. Structure reinterpretation and deter-
mination of the clathrate nature of the compounds of the general
formula MX2*6Py. J Struct Chem. 1995;36:979–82.
ˇ
ˇ´
´
63. Mojumdar SC, Miklovic J, Krutosıkova A, Valigura D, Stewart
JM. Furopyridines and furopyridine-Ni(II) complexes, synthesis,
thermal and spectral characterization. J Therm Anal Calorim.
2005;81:211–5.
64. Soldatov DV, Trushin PA, Logvinenko VA, Grachev EV.
Clathrate forming ability of some [MgA4X2] complexes where
A = 4-methylpyridine or pyridine and X = halogen or NCS.
J Struct Chem. 1993;34:232–8.
65. Dunstan PO. Thermochemistry of adducts of nickel(II) acetyl-
acetonate chelate with heterocyclic bases. Thermochim Acta.
1998;317:165–74.
66. Dunstan PO. Thermochemistry of adducts of manganese(II) and
copper(II) pentane-2,4-dionate with heterocyclic amines.
Thermochim Acta. 2000;356:19–25.
67. Dunstan PO. Thermochemistry of adducts of some bivalent
transition metal bromides with quinoline. Thermochim Acta.
2008;468:21–6.
68. Lajdova L’, Jona E, Snircova S, Miklovic J, Segl’a P, Pajtasova
M, et al. Thermal properties of solid complexes with biologically
important heterocyclic ligands. J Therm Anal Calorim. 2009;96:
59–62.
69. Hart HJ, Smith NO. Thermodynamics and structure of the p-xylene
and p-dichlorobenzene clathrates of tetra-(4-methylpyridine)-
nickel(II) thiocyanate. J Am Chem Soc. 1962;84:1816–9.
70. Casellato F, Casu B. Thermal decomposition of clathrates formed
between c-picoline-type Werner complexes and aromatic com-
51. Soldatov DV, Lipkowski J. X-Ray diffraction study of a clathrate
with quinoline-containing Werner complex ([NiQ4(NCS)2]*2Q).
J Struct Chem. 1997;38:811–8.
ˇ
´
´
´
ˇ
´ˇ
´
52. Rochon FD, Andruh M, Melanson R. Three-dimensional H-
bonded supramolecular complexes. Synthesis and crystal struc-
tures of [Mn(l-bpe)(H2O)4](ClO4)2*4(bpe)*2H2O and [Mn
(l-bpe)(bpe)2(H2O)2](ClO4)2*bpe*H2O, where M = Zn, Ni and
bpe = 1, 2-bis(4-pyridyl)ethane. Can J Chem. 1998;76:1564–70.
53. Tong M-L, Cai J-W, Yu X-L, Chen X-M, Ng SW, Mak TCW.
Linear metal(II)-4,40-bipyridine (4,4’-bpy) chains organized into
two-dimensional rhombic networks by hydrogen bonding. Crystal
structures of [Co(4,4’-bpy)(H2O)4](ClO4)2*(4,40-bpy)2*2H2O and
[Zn(4,40-bpy)(H2O)3(ClO4)](ClO4)*(4,40-bpy)1.5*H2O. Aust J Chem.
1998;51:637–41.
54. Karunakaran C, Thomas KRJ, Shunmugasundaram A, Murugesan
R. Synthesis, structure and spectroscopy of clathrate inclusion
compounds of cobalt(II), cadmium(II) and zinc(II) trans-4-sty-
rylpyridine nitrates as host with trans-4-styrylpyridine as guest
(2:1). J Inclu Phenom. 2000;38:233–49.
55. Komarov VY, Ukraintseva EA, Soldatov DV, Enright GD,
Galkin PS, Luboradzki R, et al. Crystal structure and thermody-
namic stability of the [Hg(Pyridine)4(NO3)2]*2(Pyridine) inclu-
sion compound. J Inclu Phenom. 2004;50:227–33.
56. Izarova NV, Sokolov MN, Rothenberger A, Ponikiewski L,
Fenske D, Fedin VP. Synthesis and crystal structure of a new
metal-organic coordination polymer [Fe(4,40-bpy)3(H2O)2](PF6)2
*2(4,40-bpy)*5H2O with nanosized channels clathrate large
organic molecules. C R Chimie. 2005;8:1005–10.
¨
pounds. Erdol Kohle Erdgas Petrochem. 1969;22:71–7.
71. Lipkowski J, Starzewski P, Zielenkiewicz W. Thermochemical
studies of the clathration of aromatic guest compounds by the
host–Ni(NCS)2(4-methylpyridine)4 complex. Thermochim Acta.
1981;49:269–79.
´
´ ´
´
´
72. Kunsagi-Mate A, Szabo K, Lemli B, Bitter I, Nagy G, Kollar L.
Host-guest interaction between water-soluble calix[6]arene
hexasulfonate and p-nitrophenol. Thermochim Acta. 2005;425:
121–6.
´
´ ´
´
´
73. Kunsagi-Mate S, Szabo K, Lemli B, Bitter I, Nagy G, Kollar L.
Unexpected effect of charge density of the aromatic guests on the
stability of calix[6]arene-phenol host-guest complexes. J Phys
Chem A. 2005;109:5237–42.
74. Zielenkiewicz W, Marcinowicz A, Cherenok S, Kalchenko VI,
´
Poznanski J. Phosphorylated calixarenes as receptors of L-amino
acids and dipeptides: calorimetric determination of Gibbs energy,
enthalpy and entropy of complexation. Supramol Chem. 2006;18:
167–76.
57. De Lill DT, Gunning NS, Cahill CL. Toward templated metal-
organic frameworks: synthesis, structures, thermal properties, and
luminescence of three novel lanthanide-adipate frameworks.
Inorg Chem. 2005;44:258–66.
58. Jiang J-J, Liu Y-R, Yang R, Pan M, Cao R, Su C-Y. The interplay
of coordinative and hydrogen-bonding in directing the [M(4,40-
bpy)2(H2O)2] square-grid networks: formation of 3D porous
framework [Cd(4,40-bpy)2(H2O)2](ClO4)2(4,40-bpy)(CH3OH)2.
CrystEngComm. 2008;10:1147–53.
75. Carumanee S, Titwan A, Sirithunyalug J, Weiss-Greiler P,
Wolschann P, Viernstein H, et al. Thermodynamics of the
encapsulation by cyclodextrins. Chem Technol Biotechnol. 2006;81:
523–9.
76. Al Omari MM, Zughul MB, Davies JED, Badwan AA. Ther-
modynamic enthalpy-entropy compensation effects observed in
the complexation of basic drug substrates with b-cyclodextrin.
J Inclu Phenom. 2007;57:379–84.
123

810
E. B. Okeke, D. V. Soldatov
´
´
77. Kozbiał M, Poznanski J. Experimental evidence of chiral crown
ether complexation with aromatic amino acids. J Phys Org Chem.
2007;20:506–13.
86. Ribas J, Monfort M, Resino I, Ghosh BK, Solans X, Font-Bardia
M. Mononuclear bis-chelate and tris-chelate complexes of nick-
el(II) with selenocyanate. Molecular structure of [Ni(en)3]
cis-[Ni(en)2(NCSe)2]2X2 (X = PF–6, ClO4– and SeCN–) and trans-
[Ni(en)2(NCSe)2]. Polyhedron. 1998;17:1735–9.
87. Soldatov DV, Ripmeester JA, Shergina SI, Sokolov IE, Zanina
AS, Gromilov SA, et al. a- and b-Bis(1,1,1-trifluoro-5,5-dime-
thyl-5-methoxyacetylacetonato)copper(II): transforming the
dense polymorph into a versatile new microporous framework.
J Am Chem Soc. 1999;121:4179–88.
78. De Macedo JL, Ghesti GF, Dias JA, Dias SCL. Liquid phase
calorimetry and adsorption analyses of zeolite beta acidity. Phys
Chem Chem Phys. 2008;10:1584–92.
79. Abate L, Gandolfo C. Thermal behavior of solid complexes of
phenoxyalkanoic acids and divalent metals. IV. Study on cad-
mium and mercury(II) phenoxyacetates. J Therm Anal Calorim.
1996;46:5–14.
´
80. Czakis-Sulikowska D, Radwanska-Doczekalska J, Markiewicz
88. Laskar IR, Maji TK, Chaudhuri S, Ghosh A, Chaudhuri NR.
Synthesis and characterization of cis and trans isomers of
[NiL2(NCS)2] [L = 1-(2-aminoethyl)pyrrolidine]: X-ray single-
crystal structures. Polyhedron. 2000;19:1803–7.
M, Pietrzak M. Thermal characterization of new complexes of
Zn(II) and Cd(II) with some bipyridine isomers and propionates.
J Therm Anal Calorim. 2008;93:789–94.
˘
¨
81. Kose DA, Necefoglu H. Synthesis and characterization of
bis(nicotinamide) m-hydroxybenzoate complexes of Co(II),
Ni(II), Cu(II) and Zn(II). J Therm Anal Calorim. 2008;93:
509–14.
89. Sousa EHS, Oliveira CP, Vasconcellos LCG, Lopes LGF,
´
Diogenes ICN, Carvalho IMM, et al. Thermal isomerization of
cis-[Fe(cyclam)Cl2]Cl*H2O complex in the solid state. Thermo-
chim Acta. 2001;376:141–5.
´
_
82. Kostin GA, Borodin AO, Shubin YV, Kurat’eva NV, Emelyanov
90. Rybak WK, Skarzynska A, Szterenberg L, Ciunik Z, Głowiak T.
Oxo-entity-controlled diastereomer peculiarity of rhenium(V)
complexes ReOX2(P*O)py [X = Cl, Br, I; P*O = (OCMe2
CMe2O)POCMe2CMe2O(-1); py = pyridine]: synthesis and
molecular and crystal structural characterization. Eur. J. Inorg.
Chem. 2005;4964–75.
VA, Plyusnin PE, et al. Heterometallic complexes of Co2?, Ni2?
,
and Zn2? with the [RuNO(NO2)4OH]2- anion and pyridine:
synthesis, crystal structure, and thermolysis. Russ J Coord Chem.
2009;35:57–64.
83. Souaya ER, Ismail EH, Mohamed AA, Milad NE. Preparation,
characterization and thermal studies of some transition metal
ternary complexes. J Therm Anal Calorim. 2009;95:253–8.
84. Ukraintseva EA, Kislykh NV, Dyadin YA, Soldatov DV, Log-
vinenko VA. Clathrate formation in the [M(4-MePy)2(NCS)2]—
4-MePy systems, where M—transition metal(II); 4-MePy—
4-methylpyridine. IV. Vapour pressure of 4-methylpyridine over
the clathrates [Ni(4-MePy)4(NCS)2]*(4-MePy) and [Zn(4-MePy)4
(NCS)2]*(4-MePy). Sib Khim Zh. Issue 2;1993;50-7.
91. Baidina IA, Krisyuk VV, Peresypkina EV, Stabnikov PA.
Phenomenon of trans–cis isomerization of copper(II) b-diketo-
nate on co-crystallization with lead(II) hexafluoroacetylacetonate.
J Struct Chem. 2008;49:489–93.
92. Stabnikov PA, Zharkova GI, Smolentsev AI, Ukraintseva EA,
Soldatov DV. Crystal structure and thermodynamic stability of an
acetone solvate of bis(trifluoroacetylacetonato)copper(II). J Struct
Chem. 2008;49:1084–9.
85. Nassimbeni LR, Niven ML, Zemke KJ. Structures of diisothio-
cyanatotetrakis(1-phenyl-1-ethylamine)nickel(II): enclathration
of organic guests with host isomerization. Acta Crystallogr. 1986;
B42:453–61.
93. Bagryanskaya IY, Bartashevich EV, Nikulov DK, Gatilov YV,
Zibarev AV. Intermolecular interactions and structural dichotomy
in 1,3,2,4-benzodithiadiazine crystals. J Struct Chem. 2009;50:
127–36.
123