Synthesis, crystal structure, and properties of two zinc(II) complexes with 2-propyl-4,5-imidazoledicarboxylic acid

Article abstract of DOI:10.1080/15533174.2011.611849

A tetradentate 2-propyl-4,5-imidazoledicarboxylic acid [H3pimdc] reacts with zinc sulfate in the ethanol aqueous solution and zinc acetate in the N,N-dimethylformamide (DMF) aqueous solution to give two complexes [Zn(H ₂pimdc)₂(H₂O)₂]·4H ₂O and [Zn(H₂pimdc)₂(H₂O) ₂]·2DMF. The complexes were characterized by X-ray single crystal analysis, thermal analysis, and IR spectrum. Because of the different coordination of water, complex 1 forms a fishing net-like latticed topology geometry via hydrogen bonds and π-π stacking interaction, but complex 2 forms a layer-like topology geometry via hydrogen bonds and π-π stacking interaction. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2011.611849

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Synthesis, Crystal Structure, and Properties
of Two Zinc(II) Complexes With 2-propyl-4,5-
imidazoledicarboxylic Acid
Zhirong Luo a b , Jichang Zhuang a , Qiaolan Wu a , Xianhong Yin a , Xiaoxia Zheng a & Huan
Wei a
a College of Chemistry and Ecological Engineering Guangxi University for Nationalities ,
Nanning , P. R. China
b Department of Chemistry and Life sciences , Baise University , Guangxi Baise , P. R. China
Accepted author version posted online: 14 Mar 2012.Published online: 01 May 2012.
To cite this article: Zhirong Luo , Jichang Zhuang , Qiaolan Wu , Xianhong Yin , Xiaoxia Zheng & Huan Wei (2012) Synthesis,
Crystal Structure, and Properties of Two Zinc(II) Complexes With 2-propyl-4,5-imidazoledicarboxylic Acid, Synthesis and
Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:4, 455-462, DOI: 10.1080/15533174.2011.611849
To link to this article: http://dx.doi.org/10.1080/15533174.2011.611849
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:455–462, 2012
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.611849
Synthesis, Crystal Structure, and Properties of Two Zinc(II)
Complexes With 2-propyl-4,5-imidazoledicarboxylic Acid
Zhirong Luo,1,2 Jichang Zhuang,1 Qiaolan Wu,1 Xianhong Yin,1 Xiaoxia Zheng,1
and Huan Wei1
1College of Chemistry and Ecological Engineering Guangxi University for Nationalities,
Nanning, P. R. China
2Department of Chemistry and Life sciences, Baise University, Guangxi Baise, P. R. China
EXPERIMENTAL
A
tetradentate 2-propyl-4,5-imidazoledicarboxylic acid Materials and Measurements
[H3pimdc] reacts with zinc sulfate in the ethanol aqueous solution
and zinc acetate in the N,N-dimethylformamide (DMF) aqueous
solution to give two complexes [Zn(H2pimdc)2(H2O)2]·4H2O
and [Zn(H2pimdc)2(H2O)2]·2DMF. The complexes were charac-
terized by X-ray single crystal analysis, thermal analysis, and
IR spectrum. Because of the different coordination of water,
complex 1 forms a fishing net–like latticed topology geometry
via hydrogen bonds and π-π stacking interaction, but complex 2
forms a layer-like topology geometry via hydrogen bonds and π-π
stacking interaction.
All chemicals were obtained from commercial sources and
used as received. Solvents were purified. The 2-propyl-4,5-
imidazoledicarboxylic acid [H3pimdc] was prepared according
to the previously described methods.[11] Infrared spectrum was
recorded in KBr pellets using a Nicolet 520 FT-IR spectropho-
tometer from 4000 to 400 cm−1. Elemental analyses (C, H, N)
were determined with a Perkin-Elmer 2400 II fully automatic
instrument. Perkin-Elmer Diamond TG/DTA thermal analyzer
was used to record simultaneous TG and DTG curves in the static
air atmosphere at a heating rate of 10 K·min−1/15 K·min−1 in
the temperature range 25–1000◦C using platinum crucibles.
Keywords butterfly, 2-propyl-4, 5-imidazoledicarboxylic acid, π-π
stacking, solvent system, thermogravimetric analysis
Preparation of [Zn(H2pimca)2(H2O)2]·4H2O(1)
H3pimdc (0.1982 g, 1 mmol) was dissolved in 20 mL dis-
tilled water at room temperature. ZnCl2 (0.0682 g, 0.5 mmol)
was dissolved in 20 mL ethanol, mixed up in the two solutions,
and heated to 70◦C for 8 h. Then the filtered solutions was
evaporated at room temperature for five days, and highly pure
and well-shaped red block crystals were obtained and washed
with distilled water (yield: 81.3%). Elemental Anal. Calcd.
(%) for C32H60ZnN8O28: C 35.91, H 5.65, N 10.47. Found
(%): C 35.89, H 5.67, N 10.45. IR spectrum (cm−1): 3445(s),
3216(s), 1715(vs), 1596(vs), 1538(vs), 1491(vs), 1396(s),
1277(s), 1229(m), 1127(m), 1089(w), 1057(m), 1028(m),
956(m), 870(m), 774(m), 662(m), 517(m).
INTRODUCTION
Metal complexes containing imidazoledicarboxylate ligands
have been widely investigated due to their versatile structures
and wide applications,[1–3] and have attracted much attention
for their flexible tailoring, various topologies and promising
applications in gas storage, catalysis, optoelectronics, sensors,
magnetism, luminescence, and porous materials.[4–9] Recently,
Dong-Sheng Li et al. reported a novel 2D coordination polymer
with 2-propyl-4,5-imidazoledicarboxylate and 1,3-bis(4-
pyridyl)propane(bpp), [Cd2(Hpimdc)2(bpp) (H2O)]n.[10] In this
article, two mononuclear zinc(II) complexes are prepared and
characterized. It is very interesting that they form two different
coordination conditions and topology structures in the different
solutions.
Preparation of [Zn(H2pimca)2(H2O)2]·2DMF (2)
H3pimdc (0.1982 g, 1 mmol) was dissolved in 20 mL distilled
water at room temperature. Zn(CH3COO)2·2H2O (0.1098 g, 0.5
mmol) was dissolved in 20 ml N,N-dimethylformamide(DMF),
mixed up in the two solutions, and refluxed for 8 h. Then
Received 11 December 2010; accepted 5 August 2011.
The authors thank the National Natural Science Foundation of the filtered solutions was evaporated at room temperature for
China (20761002), P. R. China, and the Natural Science Foundation of
15 days, and highly pure and well-shaped red block crystals
Guangxi (0832080), P. R. China, and the Innovation Project of Guangxi
were obtained, and washed with distilled water (yield: 78%).
University for Nationalities (gxun-chx2010083).
Elemental Anal. Calcd. (%) for C22H36ZnN6O12: C 41.58,
Address correspondence to Xianhong Yin, College of Chemistry
H 5.65, N 13.09. Found (%): C 41.56, H 5.68, N 13.07.
IR spectrum (cm−1): 3505(m), 3157(m), 1714(m), 1652(vs),
and Ecological Engineering Guangxi University for Nationalities, Nan-
ning 530006, P. R. China. E-mail: yxhphd@163.com
455

456
Z. LUO ET AL.
TABLE 1
Crystal data and structure refinements for 1 and 2
1
2
Empirical formula
C16H30ZnN4O14 C22 H36 Zn N6
O12
Formula weight
Temperature (K)
Crystal system
Space group
567.81
296 (2)
Triclinic
P-1
641.94
296 (2)
Triclinic
P-1
Unit cell dimensions (Å)
a
b
c
α
10.511 (4)
10.590 (4)
11.324 (4)
81.713 (5)
83.040 (4)
86.874 (4)
1237.3 (8), 2
1.524
7.3558 (16)
9.323 (2)
11.219 (3)
76.364 (3)
87.672 (2)
68.891 (2)
696.7 (3), 1
1.530
β
γ
Volume (Å3), Z
Calculated density
(g·cm−3
)
Absorption coefficient
1.066
0.954
(mm−1
)
Crystal size (mm)
0.42 × 0.39
× 0.36
592
0.42 × 0.39
× 0.37
F(000)
336
θ range for data collection 1.83–25.01
2.41–25.01
(◦)
FIG. 1. ORTEP view of coordination environments of the complex 1 with
Data/restraints/parameters 4318 / 15/ 326 2427 / 0 / 190
thermal ellipsoid at 30% probability (color figure available online).
Goodness-of-fit on F 2
Final Ra indices
[I > 2σ(I)]
1.058
1.175
R1 = 0.0597,
R1 = 0.0352,
wR2 = 0.1795 wR2 = 0.0971
collection and refinement for complexes are listed in Table 1.
Selected bond lengths and angles are given in Table 2. Crys-
tallographic data for complexes were deposited with the Cam-
bridge Crystallographic Data Centre (CCDC 783609 and CCDC
769657).
R indices (all data)
R1 = 0.0711,
R1 = 0.0364,
wR2 = 0.1886 wR2 = 0.0984
2
2 2
aR1
=
ꢀꢁF0|-|Fcꢁ/ꢀ|F0|. bωR2
=
[ꢀ[ω(F0 - Fc ) ]/
2 2
ꢀ[ω(F0 ) ]]1/2
RESULTS AND DISCUSSION
1578(vs), 1544(vs), 1489(vs), 1393(s), 1277(m), 1117(m),
1057(m), 975(m), 864(m), 783(m), 678(s), 508(w), 455(w).
Synthesis
H3pimdc contains six donor atoms that can coordinate to
the metal atoms. They have some different coordination modes
in the different coordination conditions. Nowdays, we syn-
thesized two novel complexes, [Zn(H2pimdc)2·6H2O]2 and
[Zn(H2pimdc)2·2DMF·2H2O], by selecting the ethanol aqueous
solution and DMF aqueous solution, respectively. The O-atoms
of waters attack the Zn(II) cation to form different crystal struc-
tures because of the different solvent system (see Figure 1 and
Figure 4). Therefore, the solvent used in the synthesis is very
important.[13] Eddaoudi et al. used 4,5-imidazole dicarboxylic
acid (H3ImDC) and In(NO3)3 to create an unusually robust an-
ionic framework (termed rho-ZMOF) that can be formulated as
[In48(HImDC)96].[14] They have selected the mixture solvent of
DMF/acetonitrile/methanol (V1:V2:V3 = 1:1:10).
DATA COLLECTION, STRUCTURAL DETERMINATION
AND REFINEMENT
A high-quality crystal of complex was selected and mounted
on the top of a glass fiber. The data were collected on a Bruker
SMART APEX CCD diffractometer at 296(2) K. Graphite-
monochromatized Mo-Kα radiation (λ = 0.71073 Å) and the
ω scan technique were used to collect the data sets. Absorp-
tion corrections were applied using SADABS.[12] The crys-
tal structure was solved with direct methods and refined with
a full-matrix least-squares technique using SHELXTL pack-
age.[12] Anisotropic thermal parameters were applied to all non-
hydrogen atoms. Hydrogen atoms were generated geometri-
cally. The crystallographic data as well as details of the data

SYNTHESIS, CRYSTAL STRUCTURE, AND PROPERTIES
457
FIG. 2. The packing diagram of the complex 1 with wires or sticks (color figure available online).
IR Spectrum
Structure Description of the Complex
Complexes 1 and 2 show very similar infrared spectra in
the range of 400–4000 cm−1. The strong and broad absorption
bands in the range 3400–3600 cm−1 in 1 and 2 indicate the
presence of the –OH. The strong absorption bands of the –NH
in 1 and 2 occur in the 3100–3400 cm−1 range. For 1, the ab-
sorption bands at 1715(1596), 1491(1396) cm−1 correspond to
νas(OCO), νs(OCO), respectively. For 2, the very strong absorp-
tion bands at 1714(1652) cm−1 can be assigned to νas(OCO) and
the bands at 1489(1393) cm−1 can be attributed to νs(OCO). The
differences between νas(OCO) and νs(OCO) for 1 are 224(200)
cm−1 and for 2 are 215(259) cm−1, indicative of carboxylate
in unidentate coordination,[15] consistent with the crystal struc-
tures.
The zinc(II) in compounds 1 and 2 are coordinated by two
waters and two [H2pimdc]−. H3pimdc is a tetradentate ligand
including two carboxyl groups and two N-atoms. We report
two complexes that the N,O-chelate form two five-membered
chelate rings, but the N-atom of N-H and the carboxyl group
adjacent to the N-atom of N-H do not take part in coordination
with zinc(II).
The molecular structure of 1 is depicted in Figure 1. We find
that there is a disordered propyl group (the C7 is disordered
over two distinct sites with occupancy factors of 0.497 and
0.503, respectively, and the C8 is disordered over two distinct
sites with occupancy factors of 0.497 and 0.503, respectively)
in the molecular structure. The selected molecular geometry

458
Z. LUO ET AL.
FIG. 3. The π. . . π stacking interactions of the complex 1 (color figure avail- FIG. 4. ORTEP view of coordination environments of the complex 2 with
able online). thermal ellipsoid at 30% probability (color figure available online).
parameters are listed in Table 2 and hydrogen bond geometry The molecular structure of 2 has two symmetrical coordination
are listed in Table 3. The geometry around this zinc(II) can be waters, a interstitial N,N-dimethylformamide and two imida-
described as a distorted octahedral environment that the two zoledicarboxylate ligands (see Figure 4). Two N-atoms and four
N-atoms are ipsilateral in the distorted octahedron. The Zn(1)- O-atoms take part in coordination with Zn(II) and form octahe-
L (L = O, N) distances are shown in the Table 2. The Zn-O dron geometry, the Zn(1)-L (L = O, N) distances are shown in
bond distances are in the range of 2.040(5) to 2.183(4) Å. The the Table 2, and its structure is shown in Figure 4. Complex 2
Zn-N bond distances are 2.113(5) Å and 2.157(5) Å, respec- forms a stratiform coordination polymer via hydrogen bonding
tively. Analysis of the crystal packing of 1 reveals the existence (Figure 5; from c-axis to observe it) between the O5 atom and
of multiple intermolecular O–H. . .O hydrogen bonds between the O4 atom, the two O5-atoms and the two O4-atoms form a
mononuclear subunits and nomadic water molecules (Figure 2) parallelogram geometry among complex 2 molecules (Figure
forming a windowlike latticed structure (from b-axis to observe 6; from c-axis to observe it). There are three kinds of hydrogen
it). See the crystal structure at b-axis, we find it likes a but- bonds in the solid state structure of 2, the first is the N,N-
terfly (Figure 3). In the Figure 3, the two imidazole rings are dimethylformamide that exists in the molecules via hydrogen
also assembled in the (010) direction by π-π stacking inter- bonding between the N1-atom and the O6-atom, the second is
action between one molecule and the other molecule defined between O3. . .H and O2 from the carbonyl group in the same
by atoms N1/C2/C3/N2/C1 (plane-plane distance 2.447(10) Å, H3pimdc, the last originates from O4 unit from the carbonyl
dihedral angle 0◦). There is one more π-π stacking interac- group of one [Zn(H2pimca)2]·DMF·2H2O and O5. . .H of one
tion between one molecule and the other molecule defined by coordinated water molecule from neighboring [Zn(H2pimc-
atoms N3/C9/N4/C10/C11 (plane-plane distance 3.288(8) Å, a)2]·DMF·2H2O group, their distance parameters are shown in
dihedral angle 0◦). These chains of complex 1 join each other the Table 3. Seeing the crystal structure at c-axis, there are a
by intermolecular interactions, hydrogen bonds, and π. . .π lot of π. . .π stacking interaction between one imidazole ring
stack interactions, forming a three-dimensional solid-state and the other imidazole ring in complex 2 except for hydrogen
structure.
bonding (Figure 7), the plane distance and dihedral angle are
The molecular structure of 2 is depicted in Figure 4. The 3.438(10) Å and 0◦ between one plane (N1/C4/C3/N2/C5) and
selected molecular geometry parameters are listed in Table 2 the other plane (N1/C4/C3/N2/C5), respectively. Complex 2
and hydrogen bond geometry parameters are listed in Table 3.
forms a stratiform coordination polymer via π. . .π stacking
Complex 2 has the same metal centre as complex 1 (zinc(II) interaction, too. These chains of complex 2 join each other
ion), but the coordination environment of Zn(II) is different. by intermolecular interactions, hydrogen bonds, and π. . .π

SYNTHESIS, CRYSTAL STRUCTURE, AND PROPERTIES
459
FIG. 5. The packing diagram of the complex 2 with wires or sticks (color figure available online).
stack interactions, forming a three-dimensional solid-state stage takes place in the 37.9–110.5◦C range corresponding to re-
structure.
lease of four free waters molecules and a coordinated water from
[Zn(H2pimca)2(H2O)2]·4H2O with weight losses of 15.1% (cal-
culated 15.86%). The second stage occurs in the 147.6–180.2◦C
range with mass loss of 2.0% (calculated 3.17%) that correlate
with elimination of a coordinated water for complex 1. The
third stage occurs in the 230.9–320.0◦C range with mass loss
Thermogravimetric Analysis
The TG-DTG curves of complex 1 with a heating rate of
10◦C·min−1 are shown in Figure 7. The DTG indicates that
complex 1 undergoes decomposition in five stages. The first
FIG. 6. A view of the crystal packing of 2 showing the O H. . .O hydrogen bonds. Displacement ellipsoids are drawn at the 30% probability level and the
hydrogen bonds are indicated by dashed lines (color figure available online).

460
Z. LUO ET AL.
TABLE 2
Selected bond lengths (Å) and angles (◦) for 1 and 2
1
Zn(1)-O(9)
Zn(1)-O(10)
Zn(1)-O(5)
Zn(1)-O(1)
Zn(1)-N(2)
Zn(1)-N(4)
O(9)-Zn(1)-O(10)
N(4)-Zn(1)-N(2)
O(5)-Zn(1)-N(2)
O(9)-Zn(1)-O(1)
O(10)-Zn(1)-O(1)
2.040 (5)
2.112 (5)
2.157 (4)
2.183 (4)
2.157 (5)
2.113 (5)
89.0 (2)
96.70 (18)
96.59 (17)
91.92 (19)
91.29 (19)
O(9)-Zn(1)-N(4)
O(10)-Zn(1)-N(4)
O(9)-Zn(1)-O(5)
O(10)-Zn(1)-O(5)
N(4)-Zn(1)-O(5)
O(9)-Zn(1)-N(2)
O(10)-Zn(1)-N(2)
N(4)-Zn(1)-O(1)
O(5)-Zn(1)-O(1)
N(2)-Zn(1)-O(1)
167.33 (18)
86.80 (19)
90.47 (19)
94.83 (19)
78.00 (16)
89.77 (19)
168.52 (19)
100.10 (17)
173.47 (15)
77.34 (16)
2
Zn(1)-N(2)
Zn(1)-N(2)#1
Zn(1)-O(5)
Zn(1)-O(5)#1
Zn(1)-O(1)
Zn(1)-O(1)#1
N(2)#1-Zn(1)-N(2)
N(2)#1-Zn(1)-O(5)
N(2)-Zn(1)-O(5)
N(2)#1-Zn(1)-O(5)#1
N(2)-Zn(1)-O(5)#1
2.0691 (16)
2.0691 (16)
2.1605 (15)
2.1605 (15)
2.2079 (15)
2.2079 (15)
180.000 (1)
92.12 (6)
O(5)-Zn(1)-O(5)#1
N(2)#1-Zn(1)-O(1)
N(2)-Zn(1)-O(1)
180.0
101.33 (6)
78.67 (6)
91.07 (6)
88.93 (6)
78.67 (6)
101.33 (6)
88.93 (6)
91.07 (6)
180.000 (1)
O(5)-Zn(1)-O(1)
O(5)#1-Zn(1)-O(1)
N(2)#1-Zn(1)-O(1)#1
N(2)-Zn(1)-O(1)#1
O(5)-Zn(1)-O(1)#1
O(5)#1-Zn(1)-O(1)#1
O(1)-Zn(1)-O(1)#1
87.88 (6)
87.88 (6)
92.12 (6)
Symmetry transformations used to generate equivalent atoms: #1 −x+1,−y+2,−z+1
TABLE 3
Hydrogen-bonding geometries for 1 and 2
D–H. . .A
Symmetry code
D–H(Å)
H. . .A(Å)
D. . .A(Å)
D–H. . .A(◦)
Compound 1
N(1)-H(1). . .O(14)
O(7)-H(7). . .O(6)
0.86
0.82
0.82
0.85
0.85
0.86
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
1.90
1.70
1.65
1.81
1.84
1.89
2.25
2.01
1.98
2.65
2.03
1.89
2.04
1.98
2.08
1.82
1.89
2.733 (8)
2.519 (6)
2.468 (7)
2.646 (10)
2.689 (10)
2.744 (8)
3.095 (8)
2.851 (8)
2.825 (6)
3.228 (7)
2.878 (7)
2.744 (9)
2.877 (7)
2.823 (6)
2.926 (6)
2.667 (7)
2.740 (6)
161.9
178.5
175.6
166.0
179.8
171.6
171.4
171.9
172.9
126.4
173.0
179.5
167.0
173.3
173.7
177.2
177.2
O(3)-H(3A). . .O(2)
O(11)-H(11B). . .O(12)
O(12)-H(12B). . .O(14)
N(3)-H(3). . .O(11)
O(14)-H(14F). . .O(8)
O(14)-H(14E). . .O(13)
O(13)-H(13B). . .O(6)
O(13)-H(13A). . .O(2)
O(13)-H(13A). . .O(1)
O(12)-H(12A). . .O(5)
O(11)-H(11A). . .O(3)
O(10)-H(10B). . .O(8)
O(10)-H(10A). . .O(4)
O(9)-H(9B). . .O(13)
O(9)-H(9A). . .O(4)
Compound 2
−x+1,−y+1,−z+1
−x+1,−y+1,−z+1
x,y,z+1
x-1,y,z
−x+1,−y,−z+1
−x+1,−y,−z+1
−x+1,−y+1,−z+2
x,y+1,z
−x,−y+1,−z+1
x-1,y,z
x,y-1,z
−x+1,−y,−z+2
O(3)-H(3). . .O(2)
0.82
0.85
0.85
0.86
1.66
1.95
2.11
1.84
2.480 (2)
2.798 (2)
2.959 (2)
2.679 (2)
176.1
175.3
175.5
166.0
O(5)-H(5C). . .O(4)
O(5)-H(5D). . .O(4)
N(1)-H(1). . .O(6)
x,y-1,z
−x,−y+3,−z+1
−x,−y+3,−z+1

SYNTHESIS, CRYSTAL STRUCTURE, AND PROPERTIES
461
FIG. 7. The π. . . π stacking interactions of the complex 2 (color figure available online).
of 34.9% (calculated 34.72%) that correlates with elimination group for complex 2 with mass loss of 17.66% (the actual value:
of a [H2pimdc]− group for complex 1. The fourth stage takes 17.16%). Finally, the remained compound becomes ZnC2O4 at
place in the 320.0–722◦C range corresponding to release of 715◦C.
C6H10N2 from complex 1 with weight losses of 20.0% (calcu-
lated 19.4%), and become ZnC2O4 at 722◦C. The fifth stage
takes place in the 722–913.5◦C range corresponding to release
of a C2O3 group from complex 1 with weight losses of 12.9%
(calculated 12.68%). Finally, the remained compound becomes
ZnO at 913.5◦C.
CONCLUSION
By the reaction of 2-propyl-4,5-imidazoledicarboxylate
ligand with metal ions in the different solvent system, two
crystal products have been successfully prepared. The X-ray de-
terminations show that they are novel imidazoledicarboxylate-
containing complexes. The thermogravimetric analysis of both
complexes indicate that the temperature range of the thermal
decomposition behaviors is very different. That is to say,
their different properties show that their crystal structures are
different.
The TG-DTG curves of complex 2 with a heating rate
of 10◦C ·min−1 are shown in Figure 7. The DTG indi-
cates that complex 2 undergoes decomposition in three stages.
The first stage takes place in the 81.2–208.0◦C range corre-
sponding to release of two DMF molecules and two coor-
dinated water molecules from [Zn(H2pimca)2(H2O)2]·2DMF
with weight losses of 27.0% (calculated 28.38%). The sec-
ond stage occurs in the 238.2–313.7◦C range with mass loss
of 30.66% (calculated 30.71%) that correlate with elimination
of a [H2pimdc]− group for complex 2. The third stage occurs in
the 313.7–715.0◦C range corresponding to loss of a C6H10N2
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FIG. 8. The TG-DTG curves of the complexes 1–2.

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