Synthesis, crystal structures and magnetic properties of five new metal(II) compounds constructed with isomers of aminobenzonitrile and dicyanamide ligands

Article abstract of DOI:10.1016/j.poly.2006.08.008

Five new compounds formulated as [Ni^II(dca)₂(para-ABN)₂(H₂O)₂] (1), [Cu^II(dca)₂(para-ABN)₂(H₂O) ₂] (2), [Cu^II(dca)₂(para-AB

Full text of DOI:10.1016/j.poly.2006.08.008

Polyhedron 26 (2007) 123–132
www.elsevier.com/locate/poly
Synthesis, crystal structures and magnetic properties of five
new metal(II) compounds constructed with isomers of
aminobenzonitrile and dicyanamide ligands
a
b
c
d,
*
Moumita Biswas , Georgina M. Rosair , Guillaume Pilet , M. Salah El Fallah
,
d
a,
*
Joan Ribas , Samiran Mitra
a
Department of Chemistry, Jadavpur University, Kolkata 700 032, West Bengal, India
b
Department of Chemistry, Heriot-Watt University, Edinburgh EH14 4AS, UK
Groupe de Cristallographie et Inge´nierie Mole´culaire, Laboratoire des Multimate´riaux et Interfaces – UMR 5615 CNRS-Universite´ Claude
c
ˆ
Bernard Lyon 1, Bat. Jules Raulin 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
´
d
` `
Department de Quı´mica Inorganica, Universitat de Barcelona, Martı i Franques, 1-11, 08028 Barcelona, Spain
Received 25 May 2006; accepted 2 August 2006
Available online 18 August 2006
Abstract
Five new compounds formulated as [NiII(dca)2(para-ABN)2(H2O)2] (1), [CuII(dca)2(para-ABN)2(H2O)2] (2), [CuII(dca)2-
(para-ABN)2]n, (3), [CuII(dca)2(ortho-ABN)2]n, (4) and [CdII(dca)2(meta-ABN)2]n (5), where dca = dicyanamide and ABN = amino-
benzonitrile, have been synthesized and characterized by single crystal X-ray diffraction studies and low temperature (300–2 K)
magnetic measurements. The structural analyses revealed that 1 and 2 are isomorphous where dca and para-ABN both act as monod-
entate ligands. 3 consists of infinite double stranded chains of Cu(II) ions connected through the para-ABN bridges whereas 4 and 5
consist of infinite double stranded chains of Cu(II) and Cd(II) respectively, connected through l1,5-dca bridges. The compounds extend
their geometries to three-dimensional for 1–3 and 5 and two-dimensional for 4 through hydrogen bonding interactions. All the metal ions
Ni2+, Cu2+ and Cd2+ are located on inversion centres and have distorted octahedral coordination geometries. The variable temperature
magnetic susceptibility measurements show that the global feature of the vMT versus T curves for 3 and 4 is characteristic of very weak
antiferromagnetic interactions and between 300 and 2 K the best fit parameters were determined as J = ꢀ2.35 and ꢀ5.1 cmꢀ1
,
respectively.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Metal (nickel, copper, cadmium); Bridging ligands (dca, ABN); Supramolecular structures; Magnetic properties; First Cu–ABN compounds
1. Introduction
their tunability and potential applications [4–6]. There is
also an aesthetic perspective; chemists are attracted by the
particular beauty and the intriguing diversity of the struc-
tures, which can be obtained by assembling metal ions
and various multifunctional ligands. The coordination
geometry of the metal ion is crucial in the self-assembling
process [7–11]. Solvent molecules and counter ions will also
influence the final supramolecular architectures. These can
affect the size, shape and hydrophilic character of voids in
zeolitic structures and hydrogen-bonded networks as well
as the overall stability of the supramolecular systems
[5,7,12,13]. Our study describes two types of ligands namely
The bulk properties of a molecular material depend crit-
ically on its crystal structure and intermolecular interac-
tions. Recently, enormous interests have been shown in
coordination polymers, zeolitic structures, hydrogen-
bonded networks and potentially important magnetic mate-
rials [1–3]. The main attractions for extended structures are
*
Corresponding authors. Fax: +91 33 24146414 (S. Mitra).
E-mail addresses: salah.elfallah@qi.ub.es (M.S. El Fallah), smitra_2002
@yahoo.com (S. Mitra).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.08.008

124
M. Biswas et al. / Polyhedron 26 (2007) 123–132
dicyanamide (dca) and aminobenzonitrile (ABN) isomers
for coordination with M(II) ions (M = Ni, Cu and Cd) in
order to construct new and varied metal frameworks. The
coordination polymers are formed when divalent first-row
transition metals are linked with the generally bidentate
(monodentate and tridentate coordination is also possible)
dicyanamide (dca, NðCNÞ2ꢀ) ligand. This ligand has signif-
icant current interest for their structural diversities and
potentially interesting magnetic properties [14]. Amino-
benzonitrile isomers can coordinate to a metal centre
through either the amine or nitrile nitrogen. Accordingly,
we have obtained five different structures where the above
two ligands show different bonding modes to metal(II) ions.
In this paper, we report five compounds with the follow-
ing formula [NiII(dca)2(para-ABN)2(H2O)2] (1), [CuII-
(dca)2(para-ABN)2(H2O)2] (2), [CuII(dca)2(para-ABN)2]n,
(3), [CuII(dca)2(ortho-ABN)2]n, (4) and [CdII(dca)2(meta-
ABN)2]n (5) using dicyanamido (dca) and three isomers
of aminobenzonitrile (ABN) ligands. A CSD search
[15,16] yielded only ten complex compounds with
aminobenzonitriles. The present work contains the first
coordination polymers of Cu(II) with ABN ligands. Two
monomeric isomorphous compounds 1 and 2 and three
polymeric frameworks 3–5 have been characterized. All
except 4 (2D hydrogen bonding network) have an extensive
3D hydrogen bonding network.
for X-ray diffraction were formed after 10 days. They were
filtered off, washed with a small amount of water and dried
in air. Elemental analysis: Calc. for CuC18H16N10O2: C
46.16, H 3.42, N 29.92%. Found: for 2 C 46.14, H 3.41,
N 29.94%. Infrared spectrum: [N(CN)]ꢀ, msym(C„N)
2195, masym(C„N) 2227, msym(C–N) 915 and masym(C–N)
1345; ABN, m(N–H) 3443 cmꢀ1
.
2.1.3. Synthesis of [Cu(dca)2(para-ABN)2]n (3)
para-Aminobenzonitrile (0.0590 g, 0.5 mmol) was dis-
solved in 5 mL of methanol. The resultant solution was
added to 5 mL of a methanolic solution of CuðNO3Þ2ꢁ
3H2O (0.1208 g, 0.5 mmol). The mixture was heated under
reflux for half an hour at 45–50 ꢁC after which it was cooled
and to it 3 mL aqueous solution of NaN(CN)2 (0.0445 g,
0.5 mmol) was added and the resultant solution was stirred
for 1 h at room temperature. It was filtered off and the fil-
trate was kept at room temperature. Green cubic crystals
suitable for X-ray diffraction study were obtained after
two weeks. They were filtered off, washed with a small
amount of water and dried in air. Yield 68% Elemental
analysis: Calc. for CuC18H12N10: C 50.01, H 2.78, N
32.41%. Found: for 3: C 50.02, H 2.77, N 32.39%. Infrared
spectrum: [N(CN)]ꢀ, msym(C„N) 2190, masym(C„N) 2235,
m
sym(C–N) 935 and masym(C–N) 1357; ABN, m(N–H)
3440 cmꢀ1
.
2. Experimental
2.1.4. Synthesis of [Cu(dca)2(ortho-ABN)2]n (4)
This compound was synthesized as for 3 but from
CuðNO3Þ2 ꢁ 3H2O (0.1208 g, 0.5 mmol) and ortho-amin-
obenzonitrile (0.0590 g, 0.5 mmol). Green cubic crystals
suitable for X-ray diffraction study were obtained from
the mother liquor by slow evaporation at room tempera-
ture after 7 days. They were filtered off, washed with a
small amount of water and dried in air. Yield 65%. Elemen-
tal analysis: Calc. for CuC18H12N10: C 50.01, H 2.78, N
32.41%. Found: for 4: C 50.03, H 2.79, N 32.38%. Infrared
spectrum: [N(CN)]ꢀ, msym(C„N) 2186, masym(C„N) 2230,
All reagents were of commercial grade and were used as
received. Na[N(CN)2]2, was purchased from the Aldrich
Company.
2.1. Preparations
2.1.1. Synthesis of [Ni(dca)2(para-ABN)2(H2O)2] (1)
para-Aminobenzonitrile (0.0590 g, 0.5 mmol) was dis-
solved in 3 mL of methanol. The resultant solution was
added to 3 mL of a methanolic solution of NiðNO3Þ2ꢁ
6H2O (0.1454 g, 0.5 mmol). It was stirred for 1 h at room
temperature. Then the mixture was placed in an ice-bath
and the temperature maintained at 0 ꢁC. Next, 5 mL aque-
ous solution of NaN(CN)2 (0.0445 g, 0.5 mmol) was added
to the mixture. Green cubic crystals suitable for X-ray dif-
fraction study were obtained from the mother liquor by
slow evaporation at room temperature after 10 days. They
were filtered off, washed with a small amount of water and
dried in air. Elemental analysis: Calc. for NiC18H16N10O2:
C 46.64, H 3.45, N 30.23%. Found: for 1 C 46.63, H 3.44,
N 30.25%. Infrared spectrum: [N(CN)]ꢀ, msym(C„N) 2195,
m
sym(C–N) 900 and masym(C–N) 1371; ABN, m(N–H)
3440 cmꢀ1
.
2.1.5. Synthesis of [Cd(dca)2(meta-ABN)2]n (5)
This compound was synthesized as for 3 but from
CdðNO3Þ2 ꢁ 4H2O (0.1542 g, 0.5 mmol) and meta-amin-
obenzonitrile (0.0590 g, 0.5 mmol). Colourless crystals
were formed after 3–4 weeks. They were filtered off, washed
with small amount of water and dried in air. Yield 66%.
Elemental analysis: Calc. for CdC18H12N10: C 44.93, H
2.50, N 29.12%. Found: for 5: C 44.90, H 2.49, N
29.14%. Infrared spectrum: [N(CN)]ꢀ, msym(C„N) 2185,
m
asym(C„N) 2237, msym(C–N) 922 and masym(C–N) 1370;
m
asym(C„N) 2230, msym(C–N) 905 and masym(C–N) 1355;
ABN, m(N–H) 3444 cmꢀ1
.
ABN, m(N–H) 3440 cmꢀ1
.
2.1.2. Synthesis of [Cu(dca)2(para-ABN)2(H2O)2] (2)
The preparation of 2 was the same as stated for com-
pound 1, using CuðNO3Þ2 ꢁ 3H2O (0.1208 g, 0.5 mmol)
instead of NiðNO3Þ2 ꢁ 6H2O. Dark green crystals suitable
2.2. Physical measurements
The elemental analyses (C, H, N) were carried out with a
Perkin Elmer 2400 II elemental analyser. For each sample

M. Biswas et al. / Polyhedron 26 (2007) 123–132
125
the analyses were carried out in duplicate. The FT-IR spec-
3. Results and discussion
tra were recorded on Perkin Elmer RX I FT-IR spectro-
photometer from KBr pellets in range 4000–400 cmꢀ1. It
is important for the characteristic bands of the dca ligand
and amino group.
Magnetic susceptibility measurements for 3 and 4 were
carried out on polycrystalline samples, with a Quantum
Design SQUID MPMS-XL susceptometer apparatus
working in the range 2–300 K under a magnetic field of
approximately 500 G (2–30 K) and 10000 G (35–300 K).
Diamagnetic corrections were estimated from Pascal
tables.
In the five compounds, both dca and ABN ligands show
varied bonding modes, i.e. (i) dca acts as bridging ligand
for 4 and 5, (ii) para-ABN acts as bridging ligand for
3 and (iii) both the dca and para-ABN ligands act as
monodentate ligands for 1 and 2. ortho- and meta-ABN
act as monodentate ligands in 4 and 5, respectively. These
resulted in four generally different structural frameworks.
The formation of compounds 2 and 3 was highly depen-
dent on the reaction conditions. In both cases the starting
materials were used in the same ratio, Cu(NO3)2:dca:
para-ABN of 1:1:1, but the different synthetic methods
employed yielded two new compounds. In the synthesis
of 3 when an aqueous solution of NaN(CN)2 was added
to a methanolic solution of Cu(NO3)2 and para-amino-
benzonitrile, a deep-green precipitate was formed within
a few minutes, during the stirring. On filtration a green
coloured solution was obtained which on keeping yielded
3. The deep-green precipitate was characterized by IR
and X-ray powder diffraction study and the found results
were identical with those of 2. From this it was concluded
that 3 was the major and thermodynamically controlled
product, whereas 2 was the minor and kinetically con-
trolled product in the preparative process of 3. The low
temperature preparative process produced 2 exclusively.
2.3. Crystal data collection and refinement
Single crystal diffraction data for 1–3 and 5 were col-
lected on a Bruker Nonius X8 Apex 2 CCD diffractometer
at 100 K, cooled by an Oxford Cryosystems Cryostream.
The crystals were covered in Paratone-N oil and mounted
in cryoloops. The structures were solved and refined using
the SHELXTL [17] suite of programs. Amine and water H
atoms were located in the difference Fourier map and iso-
tropic displacement parameters were freely refined for 1
and 5, and riding for 3 and 2. The data for 4 were collected
on a Nonius KappaCCD diffractometer; [18] the lattice
constants were refined by least-square refinement using
2005 reflections (2.1ꢁ < h < 27.8ꢁ). No absorption correc-
tion was applied to the data sets. The structure was solved
by direct methods [19] and refined [20] against F using
reflections with [I/r(I) > 3]. All non-hydrogen atoms were
successfully refined with anisotropic displacement factors.
Further experimental details for all the compounds are
summarized in Table 1.
3.1. Crystal structure analyses
Crystal structure analyses show that 1 and 2 are
monomeric compounds and form two-dimensional
hydrogen bonded sheets through the interaction of the
para-ABN and dicyanamide ligands which further extend
Table 1
Experimental parameters for the crystal structure analyses
Compound
1
2
3
4
5
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
NiC18H16N10O2
463.12
100(2)
CuC18H16N10O2
467.95
100(2)
CuC18H12N10
431.92
100(2)
CuC18H24N20
431.91
293
CdC18H12N10
480.78
100(2)
monoclinic
P21/n
7.7055(15)
8.7676(17)
13.806(3)
90
90.262(4)
90
932.7(3)
2
1.712
1.199
triclinic
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
ꢀ
P1
P1
P1
P1
˚
a (A)
7.1952(6)
7.6033(7)
9.8968(9)
104.674(3)
92.945(3)
101.929(3)
509.37(8)
1
7.2159(19)
7.600(2)
9.897(3)
104.713(7)
92.879(7)
102.055(7)
510.3(2)
1
7.2105(8)
7.9475(9)
9.4240(10)
99.740(4)
110.095(4)
109.258(4)
453.83(9)
1
7.1128(2)
7.1730(4)
9.8358(6)
89.511(3)
85.069(3)
71.300(3)
473.48(4)
1
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Dc (Mg mꢀ3
)
1.510
0.991
1.523
1.109
1.580
1.232
1.515
1.181
l (mmꢀ1
)
Reflections collected
Independent reflections [Rint
Data/restraints/parameters
R1 [I > 2r(I)]
10555
6903
14525
3405
23446
]
3613 [0.0213]
3613/0/158
0.0242
3509 [0.0222]
3509/2/154
0.0394
3278 [0.0324]
3278/0/139
0.0332
2214 [0.0270]
1289/0/133
0.0411
2987 [0.0363]
2987/0/141
0.0266
R1 (all data)
0.0258
0.0450
0.0408
0.0940
0.0363
wR2 [I > 2r(I)]
0.0741
0.1142
0.0864
0.0476
0.0712
wR2 (all data)
0.0749
0.1168
0.0885
0.0886
0.0727

126
M. Biswas et al. / Polyhedron 26 (2007) 123–132
the structures to three dimensions through weak p–p
interactions from the aromatic group of para-ABN ligands.
3–5 revealed that one-dimensional double stranded poly-
meric chains were formed. These infinite chains were
further connected via hydrogen bonding interactions to
extend the network into 3D in 3 and 5 and 2D in 4
Self-association has taken place in a variety of ways.
Firstly intermolecular interactions have been propagated
solely through ligand OHꢁ ꢁ ꢁN and NHꢁ ꢁ ꢁN hydrogen
bonds (in 1 and 2), secondly through two trans-coordinated
dca ligands and two cis amine bonded para-ABN ligands
(in 3) and thirdly by trans-coordinated amine groups of
two ABN and two cis dca ligands (in 4 and 5). Selected
bond lengths and angles for 1–5 are given in Tables 2–6,
respectively. The compounds have an extensive 3D (1–3
and 5) or 2D (4) hydrogen bonding networks; these details
are summarized in Table 7.
(H2O)2] entities. Both para-ABN and dicyanamide act as
terminal ligands (Figs. 1 and 2). The para-ABN ligand is
coordinated to the metal ion through the amine nitrogen
˚
atom. The Ni–N bond lengths are Ni–N(dca) = 2.0351 A
˚
and Ni–N(para-ABN) = 2.1513 A. The two Ni–O (aqua)
˚
distances are 2.0700 A. The nickel(II) ion exhibits a trans
distorted octahedral stereochemistry. The C–N–C angle
of the dicyanamide is 120.91ꢁ. The most intriguing features
of the crystal structure of the compound arise from interac-
tions at the supramolecular level. The para-ABN ligand
acts as both a hydrogen donor (through the amine group)
and a hydrogen acceptor (through the nitrile group) while
the dicyanamide ligand acts as a hydrogen acceptor and the
aqueous ligand acts as a hydrogen donor. The hydrogen
bonding network for both 1 and 2 consists of layers. Each
layer consists of interlocked parallelograms. One set of
parallel sides is doubly-bridging para-ABN and the other
doubly-bridging dca. In the latter, the bridge is formed
between dca and para-ABN rather than with the metal
ion. This supramolecular architecture is shown in Fig. 3.
The interlayer interactions are of a weak p–p nature
The structures of [Ni(dca)2(para-ABN)2(H2O)2] (1) and
[Cu(dca)2(para-ABN)2(H2O)2] (2) are virtually identical
and are exemplified by 1. The crystal structure of 1 consists
of centrosymmetric, mononuclear [Ni(dca)2(para-ABN)2-
Table 2
˚
Selected interatomic distances (A) and angles (ꢁ) for 1
Ni(1)–N(11)
Ni(1)–N(1)
N(1)–H(11N)
O(1)–H(11W)
C(8)–N(9)
2.0351(8)
2.1513(8)
0.898(15)
0.787(19)
1.1484(14)
1.3097(12)
1.3084(13)
Ni(1)–O(1)
N(1)–C(2)
N(1)–H(12N)
O(1)–H(12W)
C(11)–N(11)
C(12)–N(13)
2.0700(7)
1.4169(11)
0.881(16)
0.757(19)
1.1549(12)
1.1576(13)
C(11)–N(12)
C(12)–N(12)
N(11)–Ni(1)–O(1)
O(1)–Ni(1)–O(1)#1
O(1)–Ni(1)–N(1)
N(11)–Ni(1)–N(1)#1
C(2)–N(1)–H(11N)
C(2)–N(1)–H(12N)
H(11N)–N(1)–H(12N)
Ni(1)–O(1)–H(12W)
C(12)–N(12)–C(11)
89.14(3)
180.0
N(11)–Ni(1)–O(1)#1
N(11)–Ni(1)–N(1)
O(1)#1–Ni(1)–N(1)
C(2)–N(1)–Ni(1)
Ni(1)–N(1)–H(11N)
Ni(1)–N(1)–H(12N)
Ni(1)–O(1)–H(11W)
H(11W)–O(1)–H(12W)
90.86(3)
85.00(3)
88.03(3)
117.58(6)
102.7(10)
104.9(11)
110.6(12)
104.6(18)
91.97(3)
95.00(3)
111.2(9)
108.1(10)
112.3(15)
118.5(14)
120.73(9)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx, ꢀy + 2, ꢀz + 2.
Table 3
˚
Selected interatomic distances (A) and angles (ꢁ) for 2
Cu(1)–N(11)
Cu(1)–N(1)
N(1)–H(11N)
O(1)–H(11W)
C(8)–N(9)
2.0318(15)
2.1481(14)
0.80(2)
0.730(16)
1.147(2)
1.307(2)
1.158(2)
Cu(1)–O(1)
N(1)–C(2)
N(1)–H(12N)
O(1)–H(12W)
N(11)–C(12)
N(12)–C(13)
2.0748(12)
1.416(2)
0.84(2)
0.709(16)
1.154(2)
1.307(2)
C(12)–N(12)
C(13)–N(13)
N(11)#1–Cu(1)–O(1)
O(1)–Cu(1)–O(1)#1
N(11)–Cu(1)–N(1)
O(1)#1–Cu(1)–N(1)
Cu(1)–N(1)–H(11N)
Cu(1)–O(1)–H(11W)
H(11W)–O(1)–H(12W)
C(12)–N(12)–C(13)
90.97(5)
180.0
N(11)–Cu(1)–O(1)
N(11)#1–Cu(1)–N(1)
O(1)–Cu(1)–N(1)
C(2)–N(1)–Cu(1)
Cu(1)–N(1)–H(12N)
Cu(1)–O(1)–H(12W)
N(9)–C(8)–C(5)
89.03(5)
94.84(5)
92.09(5)
117.86(10)
106.2(16)
121(2)
85.16(6)
87.91(5)
103.8(17)
107.1(19)
107(3)
177.68(19)
120.91(14)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx + 2, ꢀy + 1, ꢀz + 1.

M. Biswas et al. / Polyhedron 26 (2007) 123–132
127
Table 4
Selected interatomic distances (A) and angles (ꢁ) for 3
˚
Cu(1)–N(1)
Cu(1)–N(9)
N(1)–H(12N)
C(2)–C(7)
C(3)–H(3)
C(4)–H(4)
2.0550(12)
2.497
0.798(19)
1.3955(19)
0.9500
0.9500
1.4453(18)
0.780(18)
Cu(1)–N(11)
N(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
1.9763(12)
1.4284(16)
1.3951(18)
1.3884(18)
1.402(2)
1.3932(19)
1.3893(18)
C(5)–C(8)
N(1)–H(11N)
N(11)–Cu(1)–N(11)#1
N(11)#1–Cu(1)–N(1)#1
N(11)#1–Cu(1)–N(1)
C(2)–N(1)–Cu(1)
Cu(1)–N(1)–H(11N)
Cu(1)–N(1)–H(12N)
C(3)–C(2)–C(7)
180.00(9)
89.22(5)
90.78(5)
114.34(8)
104.9(13)
103.0(13)
120.33(12)
120.29(12)
119.9
N(11)–Cu(1)–N(1)#1
N(11)–Cu(1)–N(1)
N(1)#1–Cu(1)–N(1)
C(2)–N(1)–H(11N)
C(2)–N(1)–H(12N)
H(11N)–N(1)–H(12N)
C(3)–C(2)–N(1)
90.78(5)
89.22(5)
180.00(6)
111.2(13)
114.9(13)
107.5(18)
119.25(12)
120.15(12)
118.35(12)
C(7)–C(2)–N(1)
C(4)–C(3)–H(3)
C(4)–C(3)–C(2)
C(11)–N(12)–C(12)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx, ꢀy, ꢀz.
Table 5
Table 6
˚
˚
Selected interatomic distances (A) and angles (ꢁ) for 4
Selected interatomic distances (A) and angles (ꢁ) for 5
Cu(1)–N(1)
Cu(1)–N(11)
C(12)–C(13)
C(14)–C(15)
C(16)–C(17)
C(17)–C(18)
N(1)–C(2)
1.965(3)
2.564(3)
1.390(5)
1.384(7)
1.400(6)
1.437(5)
1.141(4)
1.291(4)
Cu(1)–N(5)
N(11)–C(12)
C(13)–C(14)
C(15)–C(16)
C(17)–C(12)
C(18)–N(19)
C(2)–N(3)
1.989(3)
1.396(5)
1.386(6)
1.361(6)
1.401(5)
1.147(5)
1.299(4)
1.149(4)
Cd(1)–N(2)
Cd(1)–N(1)
N(1)–H(1N)
N(11)–C(12)
N(13)–C(20)#2
C(20)–N(13)#3
2.3259(15) Cd(1)–N(11)
2.3737(15) N(1)–C(1)
2.3326(15)
1.423(2)
0.87(2)
1.312(2)
1.149(2)
0.99(2)
N(1)–H(2N)
C(12)–N(13)
N(2)–C(20)
1.162(2)
1.302(2)
1.301(2)
N(2)–Cd(1)–N(11)
N(2)–Cd(1)–N(1)#1
N(2)–Cd(1)–N(1)
N(1)#1–Cd(1)–N(1) 180.00(6)
C(1)–N(1)–H(1N)
C(1)–N(1)–H(2N)
95.16(5)
87.32(5)
92.68(5)
N(2)#1–Cd(1)–N(11)
N(11)–Cd(1)–N(1)#1
N(11)–Cd(1)–N(1)
C(1)–N(1)–Cd(1)
84.84(5)
93.11(5)
86.89(5)
116.11(10)
105.4(13)
109.3(16)
179.07(19)
N(3)–C(4)
C(4)–N(5)
N(1)–Cu(1)–N(1)
N(1)–Cu(1)–N(5)
N(1)–Cu(1)–N(11)
N(5)–Cu(1)–N(11)
N(11)–Cu(1)–N(11)
179.994
N(1)–Cu(1)–N(5)
N(5)–Cu(1)–N(5)
N(1)–Cu(1)–N(11)
N(5)–Cu(1)–N(11)
91.4(1)
179.994
90.6(1)
87.0(1)
88.6(1)
89.4(1)
93.0(1)
179.996
108.2(13)
109.0(14)
Cd(1)–N(1)–H(1N)
Cd(1)–N(1)–H(2N)
N(7)–C(7)–C(5)
H(1N)–N(1)–H(2N) 108.7(19)
C(12)–N(11)–Cd(1) 155.06(14)
C(20)#2–N(13)–C(12) 120.04(15)
C(20)–N(2)–Cd(1)
152.80(13)
between the para-ABN aromatic rings which results in the
third dimensions and in 1 and 2 the centroid–centroid dis-
tances are 3.8159(7) and 3.8141(15) A, respectively.
Symmetry transformations used to generate equivalent atoms: #1 ꢀx + 1,
ꢀy + 1, ꢀz; #2 x + 1, y, z; #3 x ꢀ 1, y, z.
˚
Table 7
Hydrogen-bonding parameters
Compound
D–Hꢁ ꢁ ꢁA
d(D–H)
d(Hꢁ ꢁ ꢁA)
d(Dꢁ ꢁ ꢁA)
(D–Hꢁ ꢁ ꢁA)
1
N(1)–H(11N)ꢁ ꢁ ꢁN(13)#5
O(1)–H(11W)ꢁ ꢁ ꢁN(13)#5
N(1)–H(12N)ꢁ ꢁ ꢁN(12)#6
O(1)–H(12W)ꢁ ꢁ ꢁN(9)#7
0.898(15)
0.787(19)
0.881(16)
0.757(19)
2.182(15)
2.067(19)
2.307(17)
2.116(19)
3.0539(12)
2.8332(12)
3.1772(13)
2.8652(12)
163.8(13)
164.4(17)
169.7(15)
170.7(18)
2
N(1)–H(11N)ꢁ ꢁ ꢁN(13)#8
N(1)–H(12N)ꢁ ꢁ ꢁN(12)#9
O(1)–H(11W)ꢁ ꢁ ꢁN(13)#10
O(1)–H(12W)ꢁ ꢁ ꢁN(9)#4
0.80(2)
0.84(2)
0.730(16)
0.709(16)
2.28(2)
2.36(2)
2.112(17)
2.170(17)
3.064(2)
3.185(2)
2.832(2)
2.862(2)
164(2)
170(2)
169(3)
166(3)
3
N(1)–H(11N)ꢁ ꢁ ꢁN(12)#1
0.780(18)
0.798(19)
2.319(19)
2.198(19)
3.0984(17)
2.9905(17)
176.7(17)
171.8(17)
N(1)–H(12N)ꢁ ꢁ ꢁN(13)#2
4
5
N(11)–H(5)ꢁ ꢁ ꢁN(19)
0.91
2.42
3.257(5)
154
N(1)–H(1N)ꢁ ꢁ ꢁN(13)#3
0.99(2)
0.87(2)
2.81(2)
2.32(2)
3.471(2)
3.121(2)
125.0(16)
153(2)
N(1)–H(2N)ꢁ ꢁ ꢁN(7)#4
Symmetry operator codes :#1 ꢀx + 1, ꢀy, ꢀz; #2 x ꢀ 1, y ꢀ 1, z; #3 ꢀx + 3/2, y + 1/2, ꢀz + 1/2; #4 ꢀx + 1/2, y + 1/2, ꢀz + 1/2; #5 ꢀx + 1, ꢀy + 3,
ꢀz + 2; #6 ꢀx, ꢀy + 3, ꢀz + 2; #7 ꢀx, ꢀy + 1, ꢀz + 1; #8 ꢀx + 3, ꢀy + 2, ꢀz + 1; #9 ꢀx + 2, ꢀy + 2, ꢀz + 1; #10 ꢀx + 2, ꢀy, ꢀz.

128
M. Biswas et al. / Polyhedron 26 (2007) 123–132
Fig. 3. Packing diagram of 1 with hydrogen bonding shown as a dotted
line.
C3
C2
C4
N11#1
C8
C5
N9
N1
Fig. 1. Ortep view of 1 with the atom numbering scheme.
C6
Cu1
C7
N1#1
Fig. 4 shows a perspective view of 3 which is found to be
N11
C11
a [Cu(dca)2(para-ABN)2] asymmetric unit. This unit con-
tains two terminal dicyanamido ligands and four bridging
para-ABN ligands which adopt a distorted octahedral
coordination sphere. The terminal dca ligands coordinate
through the nitrile N(11) atoms, occupying the axial posi-
C12
N13
N12
Fig. 4. Ortep view of 3 showing the atom numbering scheme.
˚
tions with Cu(1)–N(11) 1.9763(12) A, while the equatorial
plane contains four nitrogen atoms from bridging para-
ABN ligands which coordinate through the two amino
N(1) atoms and two nitrile N(9) atoms [Cu(1)–N(1)
(para-ABN)2] monomer units are linked through bridging
para-ABN ligands to make a double stranded polymeric
chain (Fig. 5). The coordination polymer runs parallel to
˚
2.0550(12) and Cu(1)–N(9) 2.497 A]. The [Cu(dca)2-
Fig. 2. Ortep view of 2 with the atom numbering scheme.

M. Biswas et al. / Polyhedron 26 (2007) 123–132
129
Fig. 7. View of the propagation of 4.
Fig. 5. Packing diagram of 3 omitting the H-bonding for clarity.
ion coordination sphere is formed by two dca ligands
bridging the pairs of Cu atoms while the amino groups
from ortho-ABN ligands coordinate in the axial positions
(Fig. 7). The metal–metal distance between adjacent Cu
the crystallographic a-axis (Fig. 5), which is also observed
for compounds 4 and 5. The metal–metal distance between
adjacent Cu centres within one polymer strand is equal to
˚
centres within one polymer strand is equal to 7.113 A,
while the closest Cuꢁ ꢁ ꢁCu distance between two neighbour-
˚
9.7020 A, while the closest Cuꢁ ꢁ ꢁCu distance between two
˚
ing strands is 7.173 A. The NHꢁ ꢁ ꢁN hydrogen bond
˚
neighbouring strands is 8.795 A.
between two neighbouring polymer strands extend the
structure of 4 into two-dimensions with the amine group
from the ortho-ABN ligand acting as a hydrogen donor
and nitrile group from the same ligand of another strand
acting as a hydrogen acceptor (Fig. 7).
Compound 3 shows a rarely observed characteristic,
namely doubly bridging of the para-ABN ligand which
binds via both the amine and nitrile nitrogen atoms. Dicya-
namide can also be considered as a doubly bridging ligand
but the bridge is made by a NHꢁ ꢁ ꢁN hydrogen bond to a
para-ABN amine, which extends the geometry into three
dimensions (Supporting information 1). The cobalt and
nickel thiocyanate complexes [11] also have double bridg-
ing ABN ligands and the SCN ligands remain terminally
bound but are involved in NHꢁ ꢁ ꢁS hydrogen bonds.
The structure of 5 (Fig. 8) is very similar to that of 4 and
it is worthwhile to note that the metal–metal distance
between adjacent Cd centres within the polymer strand is
˚
7.705 A, whilst the closest Cdꢁ ꢁ ꢁCd distance between two
˚
neighbouring strands is 8.768 A. The non-bridging meta-
ABN ligands are bound to Cd with the amine group. They
are orientated anti to each other with the torsion angle
C(7A)–N(7A)–N(7)–C(7) being 180ꢁ as the Cd atom lies
on an inversion centre.
In 4 (Fig. 6) the dca ligands form bridges and the ortho-
ABN ligands are terminal in contrast to the coordination
mode of dca and para-ABN ligands in 3. The copper(II)
The polymers strands of 3 and 5 are interconnected in
three dimensions by an extensive network of NHꢁ ꢁ ꢁN
hydrogen bonds. In 3 the amine group from the para-
ABN ligand acts as the hydrogen donor and both nitrile
and amide nitrogen atoms from dicyanamide ligands of
another strand act as hydrogen acceptors (Fig. 5). While
in 5 the amine group from meta-ABN acts as the hydrogen
donor and the nitrogen atoms of the nitrile group from
C15
C14
C16
C13
C12
C18
N19
C17
N11
Cu1
N3
C4
C2
N1
N5
N5#2
N11#1
N1#1
Fig. 8. Ortep view of 5 with the atom numbering scheme.
Fig. 6. Ortep view of 4 with the atom numbering scheme.

130
M. Biswas et al. / Polyhedron 26 (2007) 123–132
0.4
1.0
0.8
0.6
0.4
0.2
0.0
0.3
)
-1
)
Km·ol
3
0.2
0.1
0.0
N
M(
T(cm
M
χ
0
15000
30000
H (G)
45000
60000
0
50
100
150
T ( K)
200
250
300
Fig. 10. Plot of vMT vs. T and M(Nb) vs. H(G) (inset) for 3.
0.4
1.2
1.0
)
0.3
-1
0.8
0.6
0.4
0.2
0.0
Fig. 9. Packing diagram of 5 with hydrogen bonding shown as a dotted
line.
mlo
)
N
·K
0.2
0.1
0.0
3
M(
T(cm
both meta-ABN and dicyanamide ligands of another
strand act as hydrogen acceptors (Fig. 9). Although 4
and 5 show very similar connectivity, 4 has a hydrogen
bonding network which extends into two dimensions and
5 extends into three dimensions. The position of the nitrile
group of the ABN ligands for 4 and 5 is different i.e. ortho-
ABN and meta-ABN respectively, so the meta-ABN isomer
may be more able to form hydrogen-bonds compared to
the ortho-ABN isomer, possibly for steric reasons.
M
χ
0
15000
30000
H (G)
45000
60000
0
50
100
150
T (K)
200
250
300
Fig. 11. Plot of vMT vs. T and M(Nb) vs. H(G) (inset) for 4.
3.2. Magnetochemistry
the magnetic behaviour of 3 we assume a negligible contri-
bution from the interactions through the hydrogen bond-
ing. The system may be treated in a simplified form as a
uniform chain of Cu(II) atoms. Thus, only one coupling
parameter (J) must be considered to interpret a possible
magnetic interaction. The experimental magnetic data have
been fitted using the equation, derived from the Bonner–
Variable temperature magnetic susceptibility measure-
ments have been performed for 3 and 4. The global feature
of the vMT versus T curves in both compounds is charac-
teristic of very weak antiferromagnetic interactions (Figs.
10 and 11). For 3 the value of vMT at 300 K is 0.384 cm3
K molꢀ1 which is as expected for one uncoupled copper(II)
ion (0.37 cm3 K molꢀ1 per Cu(II) with g = 2.0). With
decreasing temperature, the vMT value remains almost con-
stant until ca. 70 K and then it decreases sharply, giving the
minimum value of 0.170 cm3 K molꢀ1 at 2 K. The drop in
vMT at low temperatures indicates the presence of a very
weak antiferromagnetic coupling between the copper(II)
ions.
Fisher [21] calculation based on the isotropic Heisenberg
P
Hamiltonian: H = ꢀJ (SiSi+1). The best fit parameters
from 300 down to 2 K are found as J = ꢀ2.35 cmꢀ1 and
g = 2.03 with an error R = 3.2 · 10ꢀ5
, where R =
P
P
[(vMT)exp ꢀ (vMT)calc]2/ [(vMT)exp]2. The very low
value of the superexchange parameter can be understood
˚
considering the large Cuꢁ ꢁ ꢁCu distance (9.702 A). The
As is shown in Fig. 5, the structure of 3 consists of cop-
per entities linked by two para-ABN ligands, which also
acts as hydrogen donors via the amine groups, and both
nitrile and amide nitrogen atoms of dicyanamide act as
hydrogen acceptors to give a 3D compound. To interpret
weak antiferromagnetic interaction was confirmed by mag-
netization measurements at 2 K up to an external field of
5 T. At higher field, the magnetization in M/Nb units indi-
cates a value of 0.54; (a quasi half saturated S = 1/2
system) (inset Fig. 10). Comparison of the overall shape

M. Biswas et al. / Polyhedron 26 (2007) 123–132
131
of the plot with the Brillouin plot (dashed plot) for one iso-
lated ion with S = 1/2 system and g = 2 indicates slower
magnetization which is consistent with a weak antiferro-
magnetic interaction.
Cheshire, UK and grants given by the Ministerio de Edu-
´
´
y Ciencia (Programa Ramon y Cajal) and
cacion
BQU2003/00539.
For 4 the value of vMT at 300 K is 0.409 cm3 molꢀ1K
which is as expected for one uncoupled copper(II) ion
(0.413 cm3 molꢀ1 K per one CuII with g = 2.1). The vMT
values are constant over the temperature range, decreasing
to 0.0644 cm3 molꢀ1 K, at very low temperatures (2 K).
The vM curve starts at 1.36 · 10ꢀ3 cm3 molꢀ1 at room tem-
perature and increases in a uniform way to 0.0322
cm3 molꢀ1 at 2 K. The weak antiferromagnetic interaction
was confirmed by magnetization measurements at 2 K up
to an external field of 5 T. At higher field, the magnetiza-
tion in M/Nb units indicates a 0.2945 value for 4 (inset
Fig. 11). Comparison of the overall shape of the plot with
the Brillouin plot for one fully isolated ion with S = 1/2
system with g = 2.1 (dash curve) indicates very slow mag-
netization which consistent with a weak antiferromagnetic
interaction.
Taking into account the structure of 4 (Fig. 7), which
consists of copper ions linked by double l1,5-dicyanamide
groups in a 1D system, only one coupling parameter (J)
was considered to interpret possible magnetic interactions
in this compound (the interaction through the hydrogen
bonding has not been considered). The experimental mag-
netic data have been fitted using the equation which was
Appendix A. Supplementary data
Crystallographic data have been deposited at the
Cambridge Crystallographic Data Centre with deposition
numbers 602010–602014. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 IEZ, UK; fax:
+44 1223 336 033; or e-mail deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.poly.
2006.08.008.
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