Cobalt, nickel, copper and cadmium coordination polymers containing the bis(1,2,4-triazolyl)methane ligand

Article abstract of DOI:10.1016/j.ica.2011.03.037

Co(II), Ni(II), Cu(II) and Cd(II) coordination polymers containing the flexible ditopic bis(1,2,4-triazol-1-yl)methane ligand (Btm) have been prepared by reaction of equimolar quantities of the corresponding cobalt, nickel, copper and cadmium salts in EtOH solution. Structure solution and refinement of polycrystalline materials were performed by powder diffraction technique (XRPD), using conventional laboratory data. The results show that architecturally different coordination polymers were obtained depending on the counter-ion employed. The XRPD results show also that non-covalent interactions are driving forces for the occurrence of different structures.

Full text of DOI:10.1016/j.ica.2011.03.037

Inorganica Chimica Acta 373 (2011) 32–39
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Cobalt, nickel, copper and cadmium coordination polymers containing
the bis(1,2,4-triazolyl)methane ligand
a
b
b
c,
⇑
Fabio Marchetti , Norberto Masciocchi , Alessandro Figini Albisetti , Claudio Pettinari
,
c
Riccardo Pettinari
a
Scuola di Science e Tecnologie, Università degli Studi di Camerino, via S. Agostino 1, I-62032 Camerino, MC, Italy
Dipartimento di Scienze Chimiche e Ambientali, Università dell’Insubria, via Valleggio 11, 22100 Como, Italy
Scuola del Farmaco e dei Prodotti della Salute, Università degli Studi di Camerino, via S. Agostino 1, I-62032 Camerino, MC, Italy
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Co(II), Ni(II), Cu(II) and Cd(II) coordination polymers containing the flexible ditopic bis(1,2,4-triazol-1-
yl)methane ligand (Btm) have been prepared by reaction of equimolar quantities of the corresponding
cobalt, nickel, copper and cadmium salts in EtOH solution. Structure solution and refinement of polycrys-
talline materials were performed by powder diffraction technique (XRPD), using conventional laboratory
data. The results show that architecturally different coordination polymers were obtained depending on
the counter-ion employed. The XRPD results show also that non-covalent interactions are driving forces
for the occurrence of different structures.
Received 19 January 2011
Received in revised form 5 March 2011
Accepted 12 March 2011
Available online 24 March 2011
Keywords:
Coordination polymers
XRPD
Ó 2011 Elsevier B.V. All rights reserved.
Bis(triazol-1-yl)methane
Copper, cobalt, nickel complexes
1
. Introduction
Porous coordination polymers (PCPs) have recently attracted
methylene groups, longer alkyl chain or ether-like oxygen atoms)
may generate the so called third generation PCP [1], which are
more prone to modify their structures in a reversible way, possibly
answering to external stimuli such as pressure, light, sorption of
molecules or ions and so on [7,8].
the interest of many scientists, for their scientific and industrial as-
pects, mostly regarding their application to gas storage and gas
separation and to size-selective catalytic reactions, their function-
ality being granted by the regularity of their pore shape and size
Poly(triazolyl)-alkane and -borate ligands, with their diverse
bonding centers, give rise to an interesting coordination chemistry
and supramolecular architecture possibilities in the solid state
with the formation of, e.g., incorporated two-dimensional water
layers and linkage isomerism [9]. An increasing interest has been
devoted to the controlled synthesis of inorganic materials with in-
ner cavities for the catalysis of organic reactions [10,11] or with
collective magnetic phenomena for the design of molecular-based
ferromagnets [12]. The coordination chemistry of bis(triazol-
yl)alkanes is notably underdeveloped, perhaps because of the
ready formation of polymeric insoluble species [13,14]. These in-
clude some diorganotin(IV) coordination polymers, in which
bis(triazolyl)alkanes act as a bridging, instead of chelating, ligands
[15], a few silver species also containing ancillary ligands such as
[
1–4].
There are at least two different synthetic approaches to obtain
PCPs, i.e., the reaction of potentially polynucleating ligands with
metal ions having more than one vacant site, or the supramolecu-
lar (self)assembly of oligometallic coordination clusters (mostly
di-, tri- or tetranuclear), known as Secondary Building Units (SBUs),
generating, in both cases, mono-, bi- or tridimensional CPs [5].
Even though serendipity still plays a relevant role in the generating
of porosity in CPs, it is unquestionable that the use of suitable,
accurately designed, polynucleating ligands can contribute to re-
duce the intrinsic uncertainty of these processes. In rationally
choosing the ligands, two different and somewhat contrasting
‘
‘philosophies’’ can be pursued. If rigid ligands are employed, their
stiffness can lead to the formation of rigid SBUs, whose
self)assembly may generate porous frameworks with permanent
ER
3
[16,17] and transition metal coordination polymers, such as
Cd(NO [18].
[(bis(triazolyl)methane)
2
3 2 n
) ]
(
As an extension of our previous work in the coordination chem-
istry of polydentate ligands possessing multiple donor sites, we
have undertaken a systematic study of the reactions between
cobalt, copper, nickel and cadmium acceptors with the bis(1,2,4-
triazolyl)alkane ligand (Btm). In this paper we describe the synthe-
sis of new coordination polymers from Btm with Cu, Co, Ni and Cd
holes or channels [6]; at variance, ligands possessing a more or
less relevant flexibility (such as those containing ‘‘saturated’’
⇑
Corresponding author. Tel.: +39 0737 402234; fax: +39 0737 637345.
E-mail address: claudio.pettinari@unicam.it (C. Pettinari).
0
020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.03.037

F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
33
divalent cations, their spectroscopic properties, and, for the sam-
ples occurring as polycrystalline materials, the results of X-ray
Powder Diffraction (XRPD) studies.
4.12; N, 39.98%. IR (cmꢁ1): 3400br, 3321m
3001w, 1755w (NO ), 1626m (NH
C@C); 1326br, 1270br, 1201s, 1129s, 1019m, 951m, 900m, 875m,
09m (NH ), 780m, 734s (NO ), 670s. eff (295 K): 1.72
m
(NH
3
), 3115w,
m
3
m
3
), 1527w, 1505w m(C@N,
8
m
3
m
3
l
B
l .
2
. Experimental
2
(
(
.2.2.4. {[(Btm)
20 mL) containing Ni(NO
0.150 g, 1.0 mmol) was stirred for 24 h at room temperature.
2
Ni(H
2
O)
2
](NO
3
)
2
}
n
ꢂ2nH
2
O (4). An ethanol solution
O (0.291 g, 1.0 mmol) and Btm
)
3 2
ꢂ6H
2
2.1. Materials and methods
The resulting blue precipitate was isolated by filtration and dried
in vacuo. The residue obtained was washed with 5 mL of ethanol
and shown to be compound 4 (0.249 g, 0.45 mmol, yield 90%).
All chemicals and reagents were of reagent grade quality and
were used as received without further purification. All solvents
were distilled prior to use. Toluene and light petroleum (40–
Mp 350 °C (dec). Anal. Calc. for C10
N, 35.33. Found: C, 21.90; H, 3.55; N, 34.90%. IR (cm ): 3400br,
20 14
H N O10Ni: C, 21.64; H, 3.63;
6
0 °C) were dried by refluxing over freshly cut sodium. Methanol
was dried over CaO. Dichloromethane was freshly distilled from
CaH . Other solvents were dried and purified by standard proce-
dures. The samples were dried in vacuo to constant weight
20 °C, ꢀ0.1 Torr). Elemental analyses were carried out in-house
with a Fisons Instruments 1108 CHNSO-elemental analyzer. IR
ꢁ1
3
1
9
124m, 3057w, 1750w, 1643w
388sh, 1364sh, 1305s, 1289s, 1216m, 1175w, 1132m, 1040w,
90w, 893w, 826w, 782m, 738m (NO ), 670s. eff (295 K): 3.13
3
m(NO ), 1532m m(C@N, C@C);
2
m
3
l
(
B
l .
ꢁ1
spectra from 4000 to 370 cm were recorded with a Perkin–Elmer
Spectrum One FT-IR instrument. The solid samples were analyzed
on the single reflection ATR accessories. The solid has been placed
on the crystal area, the pressure arm being positioned over the
crystal/sample area. Melting points are uncorrected and were ta-
ken on an SMP3 Stuart scientific instrument and on a capillary
apparatus. The magnetic susceptibilities were measured at room
temperature (20–28 °C) by the Gouy method with a Sherwood Sci-
2
.2.2.5. [(Btm)Co(CH
Co(CH COO)
ꢂ4H
.0 mmol) was stirred for 24 h at room temperature. A violet pre-
3
COO)
2 n
] (5). An ethanol solution (20 mL) of
3
2
2
O (0.249 g, 1.0 mmol) and Btm (0.150 g,
1
cipitate formed which was filtered off and dried in vacuo. The res-
idue obtained was washed with 5 mL of ethanol and shown to be
compound 5 (0.291 g, 0.89 mmol, yield 89%). Mp 270 °C (dec). Anal.
9 12 6 4
Calc. for C H N O Co: C, 33.04; H, 3.70; N, 25.69. Found: C, 33.20;
H, 3.67; N, 25.06%. IR: 3400br, 3123m, 3035m, 2997w, 1555s,
entific magnetic balance MSB-Auto, using HgCo(NCS)
4
as calibrant
1
9
545s, 1408d, 1342m, 1277m 1203w, 1128m, 1025m, 987w,
58w, 885br, 780m, 734m, 667s. eff (295 K): 4.56
and corrected for diamagnetism with the appropriate Pascal con-
l
B
l .
stants. The magnetic moments (in
B
l ) were calculated from the
corr
1=2
equation
leff = 2.828 ðXm TÞ
.
3 2 n
2.2.2.6. [(Btm)Cu(CH COO) ] (6). An ethanol solution (20 mL) con-
taining Cu(CH
3
COO)
2
ꢂH O (0.199 g, 1.0 mmol) and Btm (0.150 g,
2
2
2
.2. Syntheses
1
.0 mmol) was stirred for 24 h at room temperature. The resulting
blue precipitate was isolated by filtration and dried in vacuo. The
residue obtained was washed with 5 mL of ethanol and shown to
be compound 6 (0.291 g, 0.88 mmol, yield 88%). Mp 200 °C (dec.).
.2.1. Synthesis of the ligand
The ligand Btm has been prepared by the literature methods
19], and has been recrystallized from hot chloroform.
[
9 12 6 4
Anal. Calc. for C H N O Cu: C, 32.58; H, 3.65; N, 25.33. Found: C,
ꢁ1
32.27; H, 3.58; N, 25.11%. IR (cm ): 3105m, 3014w, 1572s,
1522s, 1449m, 1418m, 1392s, 1347m, 1280m, 1196s, 1111s,
1035m, 1001m, 965m, 937m, 783m, 735m, 684s, 670s.
2
2
.2.2. Synthesis of the complexes
.2.2.1. {[(Btm) Co(H O) ](NO
2
2
2
3
)
2
}
n
ꢂ2nH
O (0.291 g, 1.0 mmol) and Btm
0.150 g, 1.0 mmol) was stirred for 24 h at room temperature.
2
O (1). An ethanol solution
l
eff
(
20 mL) containing Co(NO
3
)
2
ꢂ6H
2
(
B
295 K): 2.05 l .
(
The resulting orange precipitate was isolated by filtration and
dried in vacuo. The residue obtained was washed with 5 mL of eth-
anol and shown to be compound 1 (0.249 g, 0.45 mmol, yield 90%).
2
CdCl
.2.2.7. [(Btm)CdCl
2 n
] (7). An ethanol solution (20 mL) containing
2
(0.244 g, 1.3 mmol) and Btm (0.200 g, 1.3 mmol) was stirred
for 12 h at room temperature. The resulting colourless precipitate
was filtered off, washed with ethanol and dried in vacuo and
shown to be compound 7 (0.366 g, 1.1 mmol, yield 85%). Mp
2
2
3
1
1
Mp 270 °C (dec.). Anal. Calc. for C10
N, 35.31. Found: C, 21.56; H, 3.53; N, 35.22%. IR (cm ): 3400br,
H20CoN14O10: C, 21.63; H, 3.63;
ꢁ1
3
1
1
250br, 3127m, 3039m, 3001w, 1754w
526m (C@N, C@C); 1450w, 1416s, 1360m, 1321s, 1284s,
225m, 1207m, 1130m, 995m, 971m, 909m, 825m, 780m, 739s
(NO ), 671s. eff (295 K): 4.55
3
m(NO ), 1686wbr, 1630br,
80 °C (dec.). Anal. Calc. for C
5 6
H Cl
2
N
6
Cd: C, 25.20; H, 1.81; N,
m
ꢁ1
5.20. Found: C, 25.11; H, 1.73; N, 25.06%. IR (cm ): 3158w,
116w, 3090w, 3013w, 2970w, 1533m, 1521m, 1471w, 1452w,
373m, 1333w, 1300s, 1208s, 1148s, 1141s, 1133s, 1074w,
033m, 1025s, 989w, 981w, 964m, 888m, 872w, 776m, 738s, 670s.
m
3
l
B
l .
2 3 2 n
2.2.2.2. [(Btm) Co(NO ) ] (2). When stored in a heater for 30 min
at 150 °C, compound 1 turns its colour from orange to pink and
shows to be compound 2. Mp 270 °C (dec.). Anal. Calc. for
2.3. X-ray powder diffraction structural analysis
C
2
1
1
8
10 12 14 6
H N O Co: C, 24.86; H, 2.50; N, 40.58. Found: C, 24.80; H,
The samples were deposited in the hollow of an aluminum
ꢁ1
.42; N, 39.78%. IR (cm ): 3122w, 3046w, 1772w, 1763br,
759w (NO ), 1528m (C@N, C@C), 1435m, 1420m, 1320s,
301s, 1288s, 1275s, 1206m, 1127s, 1034m, 1012w, 987m, 960w,
87m, 821w, 773m, 742m, 724m (NO ), 670s. eff (295 K): 4.89
holder equipped with a quartz monocrystal zero background plate.
Diffraction data (Cu K , k = 1.5418 Å) were collected on a h:h verti-
m
3
m
a
cal scan Bruker AXS D8 diffractometer, equipped with parallel (Sol-
ler) slits, a secondary beam curved graphite monochromator, a
Na(Tl)I scintillation detector, and pulse height amplifier discrimi-
nation. The generator was operated at 40 kV and 40 mA. Slits used:
divergence 0.5°, antiscatter 0.5° and receiving 0.2 mm. Nominal
m
3
l
B
l .
2.2.2.3. {[(Btm)
2
Co(NH
3
)
2
](NO
3
)
2
}
n
ꢂ2nH
2
O (3). When exposed to a
stream of NH
3
resulting from an ammonia-water solution (30%
1 6
resolution for the present setup is 0.08° 2h (Cu Ka ) for the LaB
by mass), compound 1 turns its colour from orange to brown and
shows to be compound 3. Mp 130 °C (dec.). Anal. Calc. for
C H22CoN16O : C, 21.71; H, 4.01; N, 40.50. Found: C, 21.80; H,
10 8
peak at ca. 21.3° (2h). All scans were performed in the range
5ꢁ105° (2h). Unfortunately, only compounds 1, 4, 6 and 7 showed
high polycrystallinity, while the remaining ones showed only a few

3
4
F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
Table 1
Crystal data and refinement details for the compounds 1, 4, 6 and 7.
Empirical formula
1
C
4
C
6
C
7
C
a
14NiO12a
10
H
24CoN14
O
12
10
H
24
N
9
H
12CuN
6
O
4
5 6 2 6
H CdCl N
Formula weight (g mol 1
Crystal system
SPGR (Z)
a (Å)
b (Å)
c (Å)
ꢁ
)
591.32
monoclinic
591.08
monoclinic
P2 /n, 2
10.5488(7)
13.8940(9)
8.1732(5)
90
84.429(4)
90
1192.2(1)
1.646
331.78
333.46
triclinic
P 1ꢀ , 2
monoclinic
C2/c, 4
13.7657(4)
11.5787(4)
9.4557(2)
90
63.180(2)
90
1345.0(1)
1.638
1
P2 /n, 2
1
10.5938(4)
13.9695(5)
8.1775(3)
90
107.569(3)
90
7.2249(2)
9.8088(3)
7.9834(2)
111.807(2)
98.963(2)
84.426(2)
518.74(3)
2.134
a
(°)
b (°)
(°)
c
3
V (Å )
q
1203.8(1)
1.631
calcd (g cm 3
ꢁ
)
F(0 0 0)
610
63.9
612
19.7
680
25.4
320
214.5
) (cm 1
ꢁ
)
l(Cu K
a
Diffractometer
T (K)
Bruker D8
298(2)
5ꢁ105
39.5
Bruker D8
298(2)
5ꢁ105
24.5
Bruker D8
298(2)
5ꢁ105
43.4
Bruker D8
298(2)
9ꢁ105
41.7
2h range (°)
Indexing Goodness-of-fit (GOF)
N
N
data
5001
1393
0.102, 0.130
0.061
1.46
5001
1380
0.097, 0.124
0.045
2.21
5001
775
0.041, 0.056
0.043
2.14
4801
1190
0.109, 0.143
0.042
1.56
obs
, Rwpb
R
R
v
p
b
Bragg
2
(a)
3
V/Z (Å )
301
298
336
259
a
In this table, the formulation of the crystal data of 1 and 4 includes a slightly different number (than that proposed in the main text) of (uncoordinated) occluded water
molecules, since their site occupancy factors, from powder diffraction data alone, could be reliably estimated. Indeed, it is well known that porous metal–organic networks,
such as those found in 1 and 4, may host a variable number of guest molecules, depending on the environmental conditions.
P
P
P
P
P
P
P
b
2
2
1/2
2
2
R
p
=
i
|yi,o ꢁ yi,c|/
i
|yi,o|; Rwp = [
i
w
i
(yi,o ꢁ yi,c) /
i
w
i
(yi,o) ] ; R
B
=
n
|In,o ꢁ In,c|/
n
I
n,o
;
v
=
i
w
i
(yi,o ꢁ yi,c) /(Nobs ꢁ Npar), where yi,o and yi,c are the observed and
calculated profile intensities, respectively, while In,o and In,c the observed and calculated intensities. The summations run over i data points or n independent reflections.
Statistical weights w
i
are normally taken as 1/yi,o
.
broad peaks or haloes in their diffraction traces, thus manifesting a
nearly amorphous character; even if different synthetic attempts
were tried, no (poly)crystalline materials were recovered, and
therefore, their structural properties remain unknown.
pertinent, water oxygen atoms). Only for 7, a preferred orientation
correction was applied, in the March–Dollase formulation [21,22]
(g010 = 0.89) The background was modeled by a Chebyshev polyno-
mial function, and thermal effect simulated by using a single iso-
2
Standard peak search methods and indexing of the first lines
tropic parameter for the metals, augmented by 2.0 Å for lighter
(
2h < 30°) by TOPAS-R [20] allowed determination of the lattice
atoms. Table 1 contains the relevant crystallographic data and
structure refinement details. The final Rietveld refinements plots
are supplied in Figs. 1–4.
parameters (see Table 1) for compounds 1, 4, 6 and 7. Successful
Le Bail refinements confirmed the absence of spurious peaks; sys-
tematic absences, density and geometrical considerations indi-
ꢀ
cated space groups, P2
1
/n, P2
1
/n, C2/c and P1 for 1, 4, 6 and 7,
respectively. Successful structure solutions and refinements con-
firmed these cell and space group choices. The structural models
employed in the final whole-pattern Rietveld-like refinement were
determined ab-initio by the simulated annealing technique imple-
mented in TOPAS-R using a ‘flexible’ rigid body for the Btm ligand
3. Results and discussion
3.1. Synthesis and spectroscopy
The reaction of Btm with Co(NO
Cd(O CCH O Cu(O CCH ꢂH O and CdCl
ꢂ4H
immediately compounds 1 and 4–7 (Chart 1) in high yields.
3
) ꢂ6H
2
2
O, Ni(NO
3
)
2
ꢂ6H
2
O,
(
the free conformational parameters were the torsional angles
2
3
)
2
2
2
3
)
2
2
2
in ethanol yields
about the two NꢁCH bonds) and rigid counterions (and, where
2
4.500
4.000
3.500
3.000
2.500
2.000
1.500
1.000
[Co(Btm)2(H2O)2]n·2NO3·2H2O 100.00 %
500
0
-
500
-
1.000
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
800
700
600
500
400
300
200
100
0
[
Co(Btm)2(H2O)2]n·2NO3·2H2O 100.00 %
-
-
100
200
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
Fig. 1. Rietveld refinement plot of the {[(Btm)
region at a magnified scale. For correct the number of water atoms detected in the crystal phase, see footnote ‘a’ in Table 1.
2
Co(H
2
O)
2
](NO
3
)
2
}
n
ꢂ4nH
2
O species, with peak markers and difference plot at the bottom. The lower trace shows the high angle

F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
35
8.000
7.000
6.000
5.000
4.000
3.000
2.000
1.000
0
[Ni(Btm)2(H2O)2]n·2NO3·2H2O 100.00 %
-
-
-
1.000
2.000
3.000
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
1.400
1.200
1.000
[
Ni(Btm)2(H2O)2]n·2NO3·2H2O 100.00 %
800
600
400
200
0
-
200
400
-
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
Fig. 2. Rietveld refinement plot of the {[(Btm)
region at a magnified scale.
2
2
Ni(H O)
2
](NO
)
3 2
}
n
ꢂ4nH
2
O species, with peak markers and difference plot at the bottom. The lower trace shows the high angle
7.000
6.000
5.000
4.000
3.000
2.000
1.000
0
[CdCl2(Btm)]n 100.00 %
-
-
1.000
2.000
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
1.600
1.400
1.200
1.000
[
CdCl2(Btm)]n 100.00 %
800
600
400
200
0
-
200
400
-
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
Fig. 3. Rietveld refinement plot of the [(Btm)
2
Cd(Cl)
2
]
n
species, with peak markers and difference plot at the bottom. The lower trace shows the high angle region at a
magnified scale.
45.000
40.000
35.000
30.000
25.000
20.000
15.000
10.000
[Cu(CH3COO)2(Btm)]n 100.00 %
5.000
0
-
5.000
-
10.000
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
9.000
8.000
7.000
6.000
5.000
4.000
3.000
2.000
1.000
0
[Cu(CH3COO)2(Btm)]n 100.00 %
-
1.000
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
3 2 n
Fig. 4. Rietveld refinement plot of the [(Btm)Cu(CH COO) ] species, with peak markers and difference plot at the bottom. The lower trace shows the high angle region at a
magnified scale.
They are high melting solids, insoluble in most common organic
solvents and poorly soluble in DMSO. The composition of 1 and 4–7
is independent on the ligand to metal ratio employed, but appears
to depend on the counter-ion nature: the nitrate salts in fact

3
6
F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
NO -
2n+
3
N
N
N
N
N
N
N
N
N
OH2
M
N
N
N
O
M
O
N
N
N
N
N
N
O
N
N
O
N
N
N
N
OH2
N
N
N
N
N
N
N
N
NO -
3
N
N
N
N
n
n
1
, M = Co
, M = Ni
5, M = Co
6, M = Cu
4
Cl
Cl
Cl
N
N
N
N
N
Cd
N
N
N
N
N
Cl
Cl
Cd
N
N
N
N
N
N
N
N
Cl
Cl
N
Cd
Cl
N
N
N
N
N
N
N
n
7
Chart 1.
always afford derivatives with a 2:1 ligand to metal ratio (1 and 4),
whereas with acetate and chloride as counter-ions 1:1 species are
formed. The precipitates can contain variable amounts of lattice
water that can be easily removed by heating the powders under
vacuum (see also footnote ‘a’ in Table 1). As an example, by heating
of the water molecules in the cobalt coordination environment
(Chart 2). Exposition of 3 to aqueous vapour (70 °C) re-generates
1 in a very short time, upon releasing of the NH molecules, that
3
were easily identified. Warming 3 at 150 °C also gave 2. On the
other hand when 2 is exposed to both aqueous and ammonia va-
pour, no transformation into 1 and 3 occurred.
under vacuum the pale-rose {[(Btm)
the anhydrous pink [(Btm) Co(NO
with gaseous NH gives the pale-brown {[(Btm)
2
Co(H
], 2, is formed. Reaction of 1
Co(NH ]-
2
O)
2
](NO
3
)
2
}
n
ꢂ2nH
2
O, 1,
2
3
)
2
The IR spectra of the ligand Btm and its derivatives exhibit weak
ꢁ1
3
2
3
)
2
vibrations at ca. 3000 cm due to C–H stretching of the heterocy-
(
3
NO )
2
}
n 2
.2nH O, 3, where ammonia molecules have taken the place
clic rings and other intense absorptions between 1700 and
NO3-
2n+
N
NO2
N
N
N
N
N
N
N
N
N
N
OH2
Co
N
N
N
N
N
N
O
N
N
N
N
N
N
heating
N
N
Co
O
N
-2nH O
N
N
2
N
N
N
N
OH2
N
N
N
N
N
N
N
N
O N
2
N
N
N
NO3-
N
N
+
N
N
N
n
n
1
2
NH3
NO3-
NH3
2n+
N
N
N
N
N
N
N
N
N
N
N
N
N
Co
N
N
N
N
NH3
N
N
N
N
N
NO3-
N
N
n
3
Chart 2.

F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
37
ꢁ
1
1
500 cm , typical of ring breathing [23,24]. In the IR spectrum of 1
molecules or decomposition of the species from 250 °C. No chem-
ical decomposition was observed between 100 and 200 °C.
Compounds 1 and 4 lose both uncoordinated and coordinated
water molecule from 30 to 125 °C (exp. 12.9%, Calc. 13.0% for 1;
exp. 12.9%, Calc. 13.0% for 4). The Co(II) acetate complex 5 after los-
ing the uncoordinated water molecules up to 90 °C (exp. 10.0%,
Calc. 10.0%) starts to decompose after 200 °C, likely firstly releasing
the Btm ligand molecule that was detected sublimated on the fur-
nace cap. Finally, compound 6 is stable until 200 °C when it imme-
diately decomposes releasing the Btm ligand molecule (exp 45.1%,
Calc. 45.2%) and giving back the pure anhydrous copper(II) acetate.
Compound 2 is stable until 250 °C. From this temperature its
TGA curve resembles that of of 1. Compound 3 lose the not-coordi-
nated water molecules from 80 to 100 °C, then both coordinated
ammonia molecules are lost in the range 110–200 °C. After
250 °C the TGA profile of 3 resembles that of 1 and 2.
ꢁ1
we observed the presence of two bands at 1754 and at 739 cm
with no fine splitting, thus indicative of ionic NO3 [25–27]. By
contrast, in the IR spectrum of 2 two bands have been observed
at 1759 and 1772 cm and also two bands at 724 and 742 cm
in accordance with coordinated NO groups, likely monodentate
25–27]. It is interesting to note also that in the IR spectrum of 3,
containing two ammonia molecules in the cobalt environment
the nitrate absorptions have been found at the same values of 1,
in accordance with ionic NO
[(Btm) Ni(H O) ](NO ꢂ2nH O, 4 is analogous to that of 1 sug-
gesting a similar ionic structure in the solid state.
,
ꢁ
ꢁ1
ꢁ1
,
3
[
3
groups. The IR spectrum of
{
2
2
2
3
)
2
}
n
2
The
D
m
criterion (difference between the asymmetric and sym-
metric
[
6 (Dm
[
mCOO stretching) suggests that the acetate groups in
ꢁ1
(Btm)Co(CH
= 180 cm ) behave as unsymmetrical chelating ligands
28,29].
The magnetic susceptibility measurements have been carried
3 2 n 3 2 n
COO) ] 5 (Dm = 147 cm ) and [(Btm)Cu(CH COO) ]
ꢁ1
3.3. Crystallographic studies
out at room temperature and values of magnetic dipole moments
obtained are in the range expected for paramagnetic high-spin co-
Compounds 1 and 4 are isomorphous species crystallizing in the
7
5
2
balt ðd ; t e Þ [30–33] in the case of compounds 1 and 2, high-spin
2
g
g
monoclinic space group P2 /n, with the metal ions lying on inver-
1
8
6
2
g
9
nickel ðd ; t e Þ (compound 4) [30–33] and typical of d copper
2
g
sion centers, bound to four nitrogen atoms and two water mole-
cules in trans-pseudooctahedral MN O (M = Co, Ni) complexes.
4 2
complexes with one unpaired electron in the case of compound
. Whereas, the very low value of derivative 3 (1.72 ) is in accor-
dance with a low spin d system ðt e Þ [30–33] containing a single
6
l
B
Relevant geometrical parameters can be found in the caption of
Fig. 5. The presence of two Btm ligands per metal atom generates
two-dimensional layers with pseudosquare meshes (MꢂꢂꢂM = 9.90
and 9.85 Å, for M = Co and Ni, respectively), hosting, in the
large cavities, nitrate counterions and water molecules (located
by our XRPD analysis). Their distribution is indeed well defined
by a complex network of H-bond interactions, involving also the
water molecules coordinated to the metals. Both Btm ligands show
7
6
1
g g
2
unpaired electron. In other words, substitution of water molecules
in the cobalt environment by stronger -donor ligands such as
r
ammonia causes a larger ligand field splitting and a consequent
high-to-low spin transition [32,33].
3
.2. TG measurements
a C
2
-type conformation. Worthy of note, the shorter MꢂꢂꢂM and
MꢂꢂꢂN distances observed for the nickel species confirm the accu-
racy of our XRPD study, capable of rescuing subtle structural ef-
fects, such as the smaller octahedral radius of Ni(II) (0.83 Å)
versus hs-Co(II) (0.885 Å). Compounds structurally related
In order to examine the thermal stability of these polymeric
compounds, thermal gravimetric analyses (TGA) were carried
out. The TGA curve of 1, 4 and 5 shows release of the included
water molecules up to 100 °C, followed by release of ligand
to 1 and 4 are: {[(Bim)
2
Co(H O)
2 2
](salicylate)
2
}
n 2
ꢂ4nH O (where
Fig. 5. A portion of the 1D chain of the {[(Btm)
carbon = black. Hydrogen atoms are omitted for clarity. Relevant bond distances (Å) and angles (°): Co–N 2.11(1)–2.20(1); Co–O 2.21(1); N–Co–N 89(1)–91(1); N–Co–O
6.3(4)–93.7(4). For the isomorphous Ni(II) compound, species 4: Ni–N 2.04(1)–2.15(1); Ni–O 2.24(1); N–Ni–N 88(1)–92(1); N–Ni–O 86.0(4)–94.0(4). (For interpretation of
the references to colour in this figure legend, the reader is referred to the web version of this article.)
2
2
Co(H O)
2
](NO
3 2
) }
n 2
ꢂ4nH O polymer, viewed down [0 0 1]. Vertical axis is a. Cobalt = yellow; oxygen = red; nitrogen = blue;
8

3
8
F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
Bim = bis(imidazol-1-yl)methane) [34], {[(Bim)
phthalate) O and {[(Bim) Ni(H O) ](isophthalate)
ꢂ4nH
35]; {[(Bim) Mn(H O) ]Cl O [36]; {[(Bim) M(H O)
ꢂ2nH
rate) O (where M = Mn and Ni) [37] and {[(Bim)
ꢂ6nH
O) ]Cl O [38]. This chemical versatility
ꢂn(CH
2
Co(H
2
O)
2
](tere-
ꢂ5nH
](fuma-
Cu-
speaks for a crystal morphology largely dominated by the [0 1 0]
termination or cleavage planes, which does not find an easy struc-
tural correlation with the observed anisotropic packing of the crys-
tals of 7.
2
}
n
2
2
2
2
}
2 n
2
O
[
2
2
2
2
}
n
2
2
2
2
2
}
n
2
2
(
H
2
2
2
}
n
3
)
2
COꢂ0.5nH
2
In the recent literature, a few analogous polymers of L
(L = Btm or Bim) formulation appeared: [(Btm) Cd(NO
[(Bim) CdBr and [(Bim) Cd(CH CO [39]. While the nitrate
and acetate species are 1D polymers with Btm- or Bim-bridged dis-
tances of 9.39 and 9.40 Å, respectively (with ligands of C symme-
2
CdX
2
and their structural differences, then, suggest that predictive ste-
reochemical rules are far to be understood and that the occurrence
2
3 2 n
) ]
[18],
2
2
]
n
2
3
2 2 n
) ]
2 2 2
of ‘‘virtual’’ crystal voids in [(Bim) M(H O) ] polymers for may be
compatible with a number of fillers, such as different combinations
of counterions and solvent molecules.
s
try), the bromine derivative shows a 3D framework (with CdꢂꢂꢂCd
Compound 7 crystallizes in the centrosymmetric space group
P1, with one crystallographically independent Cd(II) ion, two chlo-
interactions of 9.15 Å), and, consistently, is not isomorphous to
ꢀ
[(Btm)
ent conformations: C
2
Cd(Cl)
2
]
n
; indeed, the two ligands show remarkably differ-
in 7 and C in [(Bim) CdBr [39].
ride anions and a full Btm molecule, all ligands acting as bridging
2
s
2
2 n
]
moieties. Infinite chains on CdCl
2
formulation run along the a
Compound 6 crystallizes in the monoclinic C2/c space group
with one Cu(II) ions lying on an inversion centre, one crystallo-
graphically independent (chelating) acetate group and one Btm li-
gand bisected by a twofold axis aligned with b. Each metal atom
direction, with alternating CdꢂꢂꢂCd interatomic distances of 3.85
and 3.97 Å and CdꢂꢂꢂCdꢂꢂꢂCd angles of ca. 134°. Each Cd(II) ion pos-
sesses
CdN Cl
a
pseudooctahedral coordination geometry, with cis-
2
4
stereochemistry, two Cd–N bond distances of 2.33(3) Å
2 4
possesses a pseudooctahedral trans-CuN O stereochemistry, with
and a N–Cd–N angle of 92.9(9)°. The refined conformation of the
Btm ligands is of the C type. The relative disposition of the bridg-
Cu–N distances of 2.058(3) Å, and short (1.93(1) Å) and long
(2.61(1) Å) Cu–O values, making the alternative description of
the local metal coordination as being nearly square planar also rea-
sonable. As found in species 1 and 4, also in this case the conforma-
2
ing ligands (with Btm-bridged CdꢂꢂꢂCd interactions of 8.71 Å, nearly
aligned with [1 2 0]) generates two-dimensional sheets (shown in
Fig. 6), stacked in the c direction by weak(er) van der Waals inter-
actions, among which some of the CHꢂꢂꢂCl type. Worthy of note, the
preferred orientation parameter refined from our Rietveld analysis
tion of the Btm ligand is C
2
. Btm-bridged CuꢂꢂꢂCu vectors (with
metal atoms ca. 9.95 Å apart) speak for a slightly more stretched
geometry than in 7, within 1D chains elongating along the [1 0 1]
2 2 n
Fig. 6. A portion of the 2D layer of the [(Btm) Cd(Cl) ] polymer, drawn down [0 0 1]. Horizontal axis is a. Cadmium = yellow; chlorine = green; nitrogen = blue;
carbon = black. Hydrogen atoms are omitted for clarity. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this
article.)
Fig. 7. A portion of the 1D chain of the [(Btm)Cu(CH
3 2 n
COO) ] polymer, stretching along [1 0 1]. Vertical axis is b. Copper = yellow; oxygen = red; nitrogen = blue;
carbon = black; hydrogen = white. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

F. Marchetti et al. / Inorganica Chimica Acta 373 (2011) 32–39
39
direction (as shown in Fig. 7), and mutually interacting mostly
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Appendix A. Supplementary material
CCDC 808483–808486 contain the supplementary crystallo-
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