Self-assembly of chelating, bridging N, N, N donor ligands and Cu(I), Cu(II), Cd(II), Hg(II): Molecular box versus coordination polymer

Article abstract of DOI:10.1016/j.poly.2014.12.036

Three flexible chelating and bridging ligands, (E)-N-(pyridin-2-ylmethylene)-1-(pyridin-3-yl)methanamine (L₁), 1-(pyridine-2-yl)-N-(pyridin-3-ylmethyl)methanamine (L₁′), (E)-N-(pyridin-2-ylmethylene)-1-(pyridin-4-yl)methanamine (L

Full text of DOI:10.1016/j.poly.2014.12.036

Accepted Manuscript
Self-assembly of chelating, bridging N, N, N donor ligands and Cu(I), Cu(II),
Cd(II), Hg(II): molecular box versus coordination polymer
Robabehsadat Tabatabaei, Saeed Dehghanpour, Jim Simpson, Janusz
Lipkowski
PII:
S0277-5387(15)00003-0
DOI:
http://dx.doi.org/10.1016/j.poly.2014.12.036
POLY 11124
Reference:
Polyhedron
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Accepted Date:
8 July 2014
27 December 2014
Please cite this article as: R. Tabatabaei, S. Dehghanpour, J. Simpson, J. Lipkowski, Self-assembly of chelating,
bridging N, N, N donor ligands and Cu(I), Cu(II), Cd(II), Hg(II): molecular box versus coordination polymer,
Polyhedron (2014), doi: http://dx.doi.org/10.1016/j.poly.2014.12.036
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Self-assembly of chelating, bridging N, N, N donor ligands and
Cu(I), Cu(II), Cd(II), Hg(II): molecular box versus coordination
polymer
Robabehsadat Tabatabaeia, Saeed Dehghanpoura,*, Jim Simpsonb,*, Janusz Lipkowskic
a Department of Chemistry, Alzahra University, P.O.Box 1993891176, Tehran, Iran.
b Department of Chemistry, University of Otago, PO BOX 56, Dunedin 9054, New Zealand.
c Cardinal Wyszynski University in Warsaw, School of Sciences, Wojcickiego 1/3, 01-938
Warsaw, Poland.
Corresponding Author. Tel.: +98 021 88041344: Fax: +98 021 88041344.
E-mail: Dehganpour_farasha@yahoo.com
1

Abstract
Three flexible chelating and bridging ligands, (E)-N-(pyridin-2-ylmethylene)-1-(pyridin-3-
yl)methanamine (L1), 1-(pyridine-2-yl)-N-(pyridin-3-ylmethyl)methanamine (L1′), (E)-N-
(pyridin-2-ylmethylene)-1-(pyridin-4-yl)methanamine (L2), have been synthesized. The
reaction of these ligands with various metal salts yielded a series of compounds, namely
[Cu2(L1)(PPh3)2I2]2 (1), [Cu2(L2)(PPh3)2I2]n (2), [CuL1(NO3)2]2 (3), [ZnL1(NO3)2]2 (4),
[CdL1(NO3)2]2 [(5), [CdL1′(NO3)2]2 (6) and [HgL1Cl2]n (7). The compounds were
characterized by elemental analysis, spectroscopic methods (IR, UV/Vis) and X-ray
crystallography. X-ray structural analysis of compound 1 reveals the formation of a
centrosymmetric tetranuclear compound. The repeat unit of coordination polymer 2
comprises a Cu2I2 unit with a triphenyl phosphane substituent on Cu1 linked to an adjacent
Cu2I2 unit by the ligand L2 that acts as a bridge. Compounds 3, 4, 5 and 6 exhibit a common
metallo-cyclophane [M2(L)2(NO3)4] skeleton. Two M2+ cations are linked by two L1 ligands
and these ligands chelate to each metal atom through the imine nitrogen (or amine nitrogen)
atoms and the nitrogen atom of the 2-pyridyl ring, and bind to the other metal atom of the
pair via the nitrogen atoms of the 3-pyridyl rings. Structural studies of 7 revealed the
formation of a coordination polymer in which the polymer chain propagates in helical spirals
along a two-fold screw axis parallel to b. The metal coordination geometries and coordination
of the nitrato anions to the metals are noted and discussed.
Keywords: Diimine ligands, flexible chelating and bridging ligands, molecular box,
coordination polymer, X-ray structure analyses, spectroscopy.
2

1. Introduction
Recently, the use of multifunctional N-donor bridging ligands for the construction of
metallosupramolecular arrays has been investigated. Extensive studies have been carried out
using rigid and flexible bridging ligands and a variety of one-, two- and three-dimensional
structures, discrete macrocycles, such as grids, boxes, cylinders, molecular polyhedra and
helices have been obtained [1-6]. Several factors, such as the nature of the coordination sites,
geometrical disposition of donor sites, template molecules, the effect of counterions and the
presence of non-covalent interactions, play important roles in the development of the final
structures. Extensive studies have been carried out using rigid bridging ligands such as 4,4′-
bipyridines, Schiff-bases, 2,4,6-tri(4-pyridyl)-1,3,5-triazine, etc. and a variety of polymeric
networks with beautiful topologies have been obtained. A metallo-cyclophane or ‘‘molecular-
box” has been formed upon coordination of such ligands to the Cu(II) ion [7]. Helical and
triple-helical conformations have also been observed for Re(I), Cu(I) and Zn(II) ions, often
showing unusual structural and chemical properties [8-10]. Sun and co-workers reported
some coordination polymers constructed from reduced bis-Schiff base ligands, namely 1,2-
bis(4-pyridylmethylamino)-ethane, 1,2-bis(3-pyridylmethylamino)ethane and N,N′-bis(3-
pyridylmethyl)-1,4-benzenedimethylamine [11-14]. Lee and co-workers have prepared
coordination polymers from 4-(4-aminophenoxy)-N-(pyridin-3-ylmethylene)aniline, 4-(4-
aminophenoxy)-N-(pyridin-4-ylmethylene)aniline,
N,N′-4,4′-oxybis(N-(pyridin-3-
ylmethylene)aniline) and N,N′-4,4′-oxybis(N-(pyridin-4-ylmethylene)aniline) [15-20].
However, the use of unsymmetrical chelating and bridging ligands for the construction of
discrete macrocycles and/or coordination polymers is less common [21-23]. Recently, we
have prepared 3-(2'-pyridylmethyleneamino)pyridine and explored its coordination behaviour
and the formation of novel homo and heterometallic coordination polymers [21]. Herein, we
3

report the design and preparation of (E)-N-(pyridin-2-ylmethylene)-1-(pyridin-3-
′
yl)methanamine (L1), 1-(pyridine-2-yl)-N-(pyridin-3-ylmethyl)methanamine (L1 ), and (E)-N-
(pyridin-2-ylmethylene)-1-(pyridin-4-yl)methanamine (L2) (Scheme 1), with the aim to
construct discrete macrocycles and coordination polymers with Cu(I), Cu(II), Zn(II), Cd(II)
and Hg(II). The compounds have been characterized by IR spectroscopy, elemental analysis,
single crystal X-ray diffraction and thermogravimetric analysis.
2. Experimental Section
2.1. General
All reagents were analytical grade commercial products and were purchased from Sigma
Aldrich and used without further purification. Infrared (IR) samples were prepared as KBr
pellets and their spectra obtained in the range 400-4000 cm-1 on a Bruker Tensor 27
spectrophotometer. Electronic absorption spectra were recorded on a Perkin Elmer Lambda
35 double beam spectrophotometer. Emission spectra of the solid samples were obtained
using a Varian Cary Eclipse fluorescence spectrophotometer at room temperature. Elemental
analyses were performed using a Heraeus CHN-O-RAPID elemental analyzer. NMR spectra
were obtained on a BRUKER AVANCE DRX500 (500 MHz) spectrometer. Emission spectra
were obtained using a Varian Cary Eclipse fluorescence spectrophotometer at room
temperature.
2.2. Syntheses
2.2.1. (E)-N-(pyridin-2-ylmethylene)-1-(pyridine-3-yl)methanamine (L1)
(E)-N-(pyridin-2-ylmethylene)-1-(pyridine-3-yl)methanamine (L1) was prepared by slightly
modifying a known literature procedure [24,25]. To a solution of pyridine-2-carbaldehyde
4

(1.07 g, 10 mmol) in 25 mL CH2Cl2 was added a solution of 3-aminomethylpyridine (1.08 g,
10 mmol) in 25 mL ethanol and then anhydrous MgSO4 (2.5 g) was added to the mixture.
The resulting mixture was heated at reflux for 2 h, then stirred for another 3 h, and filtered.
The solvent was removed in vacuo and the ligand, (E)-N-(pyridin-2-ylmethylene)-1-
(pyridine-3-yl)methanamine (L1), was obtained as a pale yellow oil. Yield: 81%. Anal. Calc.
1
for C12H11N3: C 73.07, H 5.62, N 21.30. Found C 73.17, H 5.58, N 21.25%. H NMR (δ,
CDCl3): 8.65 (d, 1H, JHH = 7.9 Hz), 8.54 (s, 1H, HC=N), 8.53 (b, 2H), 8.04 (d, 1H, JHH = 8.4
Hz), 7.75 (m, 2H), 7.31 (m, 2H), 4.86 (s, 2H, =NCH2-3Py). IR (KBr/ν, cm-1): 3055, 1709,
1646 (C=Nim), 1585, 1471, 1428, 1368, 1317, 1294, 1225, 1186, 1149, 1125, 1102, 1044,
1027, 994, 865, 827, 777, 743, 713, 666, 640, 617, 504. UV-Vis, λ, nm (log ε) (DMSO): 270
(4.48).
2.2.2. 1-(pyridine-2-yl)-N-(pyridin-3-ylmethyl)methanamine (L1′)
To a solution of (E)-N-(pyridin-2-ylmethylene)-1-(pyridine-3-yl)methanamine (L1) (197 mg,
1 mmol) in methanol (10 ml) was added sodium borohydride (189 mg, 5 mmol) in small
portions with stirring at room temperature. The resulting mixture was stirred at room
temperature for 24 h. Then 50 mL of saturated NaCl solution was added and refluxed for 5
hours. The suspension was filtered and the product extracted with dichloromethane. The
solvents were removed in vacuo and the product obtained as a pale yellow oil. Yield: 73%.
1
Anal. Calc. for C12H13N3: C 72.33, H 6.58, N 21.09. Found C 72.29, H 6.61, N 21.10%. H
NMR (δ, DMSO): 8.56 (s, 1H), 8.5 (m, 2H), 7.77 (m, 2H, H4), 7.23-7.49 (m, 3H), 4.85 (b,
1H, NH), 3.82 (s, 2H, 2pyCH2N) 3.73 (s, 2H, 3pyCH2N). IR (KBr/ν, cm-1): 3285 (N–H),
3053, 2992, 1590 (C=Npy), 1474, 1429, 1362, 1222, 1188, 1120, 1047, 1028, 994, 841, 789,
760, 714, 628. UV-Vis, λ, nm (log ε) (DMSO): 265 (4.46).
5

2.2.3. (E)-1-(pyridin-3-yl)-N-(pyridine-4-ylmethylene)methanamine (L2)
(E)-1-(pyridin-3-yl)-N-(pyridine-4-ylmethylene)methanamine (L2), was synthesized by a
procedure similar to that used for L1, but using pyridine-4-carbaldehyde (1.07 g, 10 mmol)
and 3-aminomethylpyridine (1.08 g, 10 mmol). Yield: 83%. Anal. Calc. for C12H11N3: C
73.07, H 5.62, N 21.30. Found C 73.14, H 5.60, N 21.26%. 1H NMR (δ, CDCl3): 8.68 (d, 2H,
JHH = 8.6 Hz), 8.53 (s, 1H, HC=N), 8.41 (m, 2H), 7.85 (m, 2H), 7.31 (m, 2H), 4.85 (s, 2H,
=NCH2-3Py). IR (KBr/ν, cm-1): 3031, 2998, 1708, 1645 (C=Nim), 1597, 1558, 1478, 1422,
1382, 1349, 1322, 1234, 1187, 1125, 1103, 1059, 1025, 994, 872, 814, 713, 642, 614, 519.
UV-Vis, λ, nm (log ε) (DMSO): 265 (4.77).
2.2.4. [Cu2(L1)(PPh3)2I2]2 (1)
To a solution of CuI (19 mg, 0.1 mmol) in 5 mL acetonitrile was added dropwise
triphenylphosphine (26 mg, 0.1 mmol) in 4 ml acetonitrile under a nitrogen atmosphere. The
mixture was stirred for 30 min and then L1 (19.7 mg, 0.1 mmol) in 5 ml acetonitrile was
added and stirred for an additional 10 min. The volume of the solvent was reduced under
vacuum to about 1 mL. Diffusion of diethyl ether vapor into the concentrated solution gave
red crystals. The crystals were filtered off and washed with a mixture of diethyl ether-
acetonitrile (9:1 v/v), and dried in vacuo. Yield: 76%. Anal. Calc. for C96H82Cu4I4N6P4: C
1
52.28, H 3.75, N 3.81. Found C 52.19, H 3.84, N 3.87%. H-NMR (δ, DMSO): 8.85 (s, 1H,
HC=N), 8.38 (m, 1H), 8.15 (m, 1H), 8.08 (m, 1H), 7.64 (m, 5H), 7.37 (m, 30H, phenyl ring),
4.98 (s, 2H, =NCH2-3Py). IR (KBr/ν, cm-1): 3047, 1621 (C=Nim), 1584, 1476, 1432, 1383,
1351, 1297, 1261, 1221, 1183, 1154, 1125, 1093, 1069, 1027, 995, 969, 921, 848, 793, 774,
744, 696, 666, 519, 498. UV-Vis, λ, nm (log ε) (DMSO): 264 (4.43), 281 (3.95), 384 (1.45),
485 (1.21).
6

2.2.5. [Cu2(L2)(PPh3)2I2]n (2)
This compound was synthesized by a procedure similar to that for 1, but using L2 (19.7 mg,
0.1 mmol). Yellow single crystals suitable for X-ray diffraction were obtained by slow
evaporation from the filtrate over several days. Yield: 69%. Anal. Calc. for C48H41Cu2I2N3P2:
C 52.28, H 3.75, N 3.81. Found C 52.35, H 3.81, N 3.76%. 1H-NMR (δ, DMSO): 8.65 (s, 1H,
HC=N), 7.93 (m, 3H), 7.45 (m, 5H), 7.39 (m, 30H, phenyl ring), 4.98 (s, 2H, =NCH2-3Py).
IR (KBr/ν, cm-1): 3047, 1602 (C=Nim), 1477, 1430, 1382, 1307, 1234, 1185, 1156, 1125,
1093, 1064, 1026, 998, 876, 820, 791, 745, 696, 618, 517, 432. UV-Vis, λ, nm (log ε)
(DMSO): 267 (4.56), 288 (3.91), 303 (2.12).
2.2.6. [CuL1(NO3)2]2 (3)
At room temperature, a solution of Cu(NO3)2.3H2O (24.1 mg, 0.1 mmol) in 2 mL methanol
was carefully layered onto the top of a solution of L1 (19.7 mg, 0.1 mmol) in 2 mL
dichloromethane. After two weeks, the resulting blue needle-like crystals were filtered, and
air-dried to give [CuL1(NO3)2]2. Yield: 58%. Anal. Calc. for C24H22Cu2N10O12: C 37.46, H
2.88, N 18.20. Found C 37.39, H 2.90, N, 18.26%. IR (KBr/ν, cm-1): 3047, 2924, 1642
(C=Nim), 1598, 1438 (NO3), 1382, 1282 (NO3), 1229, 1193, 1106, 1024, 818, 791, 730, 701,
655, 505, 421. UV-Vis, λ, nm (log ε) (DMSO): 268 (4.21), 280 (4.53), 483 (1.51).
2.2.7. [ZnL1(NO3)2]2 (4)
At room temperature, a solution of Zn(NO3)2.6H2O (29.7 mg, 0.1 mmol) in 4 mL methanol
was carefully layered onto the top of a solution of L1 (19.7 mg, 0.1 mmol) in 2 mL
dichloromethane. After two weeks, the resulting colorless crystals were filtered, and air-dried
to give [ZnL1(NO3)2]2. Yield: 45%. Anal. Calc. for C24H22N10O12Zn2: C 37.28, H 2.87, N
1
18.11. Found C 37.34, H 2.84, N 18.16%. H NMR (δ, DMSO): 8.80 (s, 1H, HC=N), 8.54
7

(m, 1H), 8.34 (m, 2H), 8.11 (m, 1H), 7.92 (m, 2H), 7.37 (m, 2H), 4.85 (s, 2H, =NCH2-3Py).
IR (KBr/ν, cm-1): 3098, 2950, 1648 (C=Nim), 1595, 1462 (NO3), 1380, 1293 (NO3), 1225,
1192, 1124, 1102, 1056, 1026, 886, 816, 788, 738, 700, 648, 501. UV-Vis, λ, nm (log ε)
(DMSO): 265 (4.11), 271 (2.17).
2.2.8. [CdL1(NO3)2]2 (5)
At room temperature, a solution of Cd(NO3)2.4H2O (30.8 mg, 0.1 mmol) in 4 mL methanol
was layered onto the top of a solution of L1 (19.7 mg, 0.1 mmol) in 2 mL dichloromethane.
After three weeks, the resulting yellow crystals were filtered and air-dried to give
[CdL1(NO3)2]2. Yield: 42%. Anal. Calc. for C24H22Cd2N10O12: C 33.24, H 2.56, N 16.15.
1
Found C 33.29, H 2.59, N 16.09%. H NMR (δ, DMSO): 8.75 (s, 1H, HC=N), 8.57 (m, 1H),
8.46 (m, 2H), 8.17 (m, 1H), 8.02 (m, 1H), 7.68 (m, 2H), 7.30 (m, 1H), 4.87 (s, 2H, =NCH2-
3Py). IR (KBr/ν, cm-1): 3047, 2921, 1648 (C=Nim), 1583, 1458 (NO3), 1384, 1291 (NO3),
1221, 1192, 1125, 1100, 1053, 1025, 877, 818, 791, 735, 702, 647, 500. UV-Vis, λ, nm (log
ε) (DMSO): 264 (4.23), 281 (3.95).
2.2.9. [Cd(L1′)(NO3)2]2 (6)
A mixture of Cd(NO3)2.4H2O (30.8 mg, 0.1 mmol), ligand L1′ (19.7 mg, 0.1 mmol), methanol
(10 ml) and benzene (3 ml) was heated in a vial at 70 °C for 3 days and then cooled to room
temperature. The crystalline product that formed was collected by filtration, washed with
methanol and air-dried to give colorless crystals of [Cd(L1′)(NO3)2]2. Yield: 41%. Anal. Calc.
for C24H26Cd2N10O12: C 33.08, H 3.01, N 16.07. Found C 32.99, H 3.06, N 16.12%. 1H NMR
(δ, DMSO): 8.53 (m, 3H), 7.97 (m, 1H), 7.81 (d, 1H, J = 9 Hz), 7.38-7.55 (m, 3H), 4.53 (b,
1H, NH), 3.82 (s, 2H, 2pyCH2N), 3.80 (s, 2H, 3pyCH2N). IR (KBr/ν, cm-1): 3256 (N–H),
2922, 1605 (C=Npy), 1457 (NO3), 1389, 1287 (NO3), 1216, 1182, 1119, 1058, 1023, 930,
8

807, 771, 735 (m), 705, 651, 510. UV-Vis, λ, nm (log ε) (DMSO): 262 (4.19), 271 (3.98).
2.2.10. HgL1Cl2]n (7)
To a solution of anhydrous HgCl2 (27.1 mg, 0.1 mmol) in 10 ml acetonitrile was added a
solution of L1 (19.7 mg, 0.1 mmol) in 4 ml N,N-dimethylformamide (DMF). On slow
evaporation of the solution, yellow crystals were obtained, which were collected by filtration,
and air-dried to give [HgL1Cl2]n. Yield: 41%. Anal. Calc. for C12H11Cl2HgN3: C 30.75, H
1
2.37, N 8.96. Found C 30.69, H 2.41, N, 8.91%. H NMR (δ, DMSO): 8.86 (s, 1H, HC=N),
8.73 (s, 1H), 8.53 (m, 2H), 8.1 (m, 1H), 7.77 (m, 2H), 7.39 (m, 2H), 4.97 (s, 2H, =NCH2-
3Py). IR, (KBr/ν, cm-1): 3055, 2909, 1653 (C=Nim), 1586, 1475 (NO3), 1435, 1388, 1297
(NO3), 1257, 1219, 1188, 1122, 1101, 1047, 1006, 984, 961, 871, 832, 795, 774, 705, 672,
643, 625, 493. UV-Vis, λ, nm (log ε) (DMSO): 261 (4.21), 282 (3.91).
2.3. X-ray analyses
The X-ray measurements of single crystals of 1 and 3 were carried out on a Bruker-Nonius
Kappa-CCD diffractometer equipped with a graphite monochromator and a low temperature
device (Oxford Cryosystems) at the Institute of Physical Chemistry, Polish Academy of
Sciences, Warsaw, Poland. Data for 2, 4, 5, 6 and 7 were collected on a similar system at the
University of Otago, New Zealand. MoKα radiation (λ = 0.71073 Å) was used for all of the
collections, which were controlled by APEX2 [26], with data for 1 and 3 collected at 100(2)
K, while those for 2 and 4-7 were collected at 90(2) K. The collected data were corrected for
Lorentz and polarization effects using SAINT [27] and numerical absorption corrections were
applied using SADABS [24]. The structures were solved by direct methods (SHELXS-97
[27] for 1-6, and SIR92 [28] for 7) and refined using full-matrix least-squares procedures
(SHELXL-97 [27]). With the exception of 1, all non-hydrogen atoms were refined
9

anisotropically. In 1 there is a solvating acetonitrile molecule which is orientationally
disordered over two positions, with the terminal carbon (methyl group) placed in one position
and the C-N part adopting two orientations. The non-hydrogen atoms of this solvent were
refined isotropically. With the exception of 1 and 6, all hydrogen atoms were placed in
calculated positions, and their thermal parameters were refined isotropically. In 1, hydrogen
atoms of the acetonitrile molecule were not included in the refinement as they are bonded to a
carbon atom having two different orientations (this leads to a small disagreement between the
chemical formula and the content of the unit cell, as seen in the CIF file). The N—H
hydrogen atom for 6 was located in a difference Fourier map and its coordinates were refined
with Ueq = 1.2 Ueq(N). Compound 2 is disordered such that the pyridyl rings have two
distinct orientations and pivot on the well-defined imino group. The asymmetric unit thus
comprises one complete ligand at half occupancy, the Cu(I) cation, an iodide anion and a
PPh3 ligand. For compound 5, three low angle reflections with Fo << Fc were omitted from
the final stages of the refinement. Details of the X-ray measurements, crystal data and bond
lengths and angles for all of the complexes are given in Tables 1-3.
3. Results and discussion
3.1. Synthesis and spectral properties
Two potential linking ligands L1 and L2 (Scheme 1) were prepared by a simple and
straightforward Schiff-base condensation of pyridine-2-carbaldehyde and pyridine-3-
carbaldehyde with 3-aminomethylpyridine. L1 was reduced with sodium borohydride to give
[(3-py)–CH2–NH–CH2–(2-py)] (L1′). Because of the possible rotations about the NH–CH2
single bond, the ligand L1′ is expected to be considerably more flexible than L1 or L2.
[Cu2(L1)(PPh3)2I2]2, (1) and [Cu2(L2)(PPh3)2I2]n, (2) were prepared by the reaction of the
10

ligands (L1 and L2) with PPh3 and copper(I) iodide. [CuL1(NO3)2]2, (3) was prepared by the
reaction of L1 with Cu(NO3)2.3H2O. [ZnL1(NO3)2]2, (4) and [CdL1(NO3)2]2, (5) were
prepared by layering a methanol solution containing M(NO3)2 on top of a dichloromethane
solution containing the corresponding ligand L1. [HgL1Cl2]n, (7) was obtained upon slow
evaporation of a solution containing of HgCl2 and L1 at room temperature. Solvothermal
treatment of cadmium(II) nitrate with the ligand L1′ in methanol–benzene at 70 °C produced
[Cd(L1′)(NO3)2]2, (6). These complexes are insoluble in chloroform, methanol, ethanol and
acetone, and are stable under ambient conditions.
The IR spectra of the free ligands (L1 and L2) exhibit ν(C=N) at 1646 and 1645 cm-1,
respectively. In complexes 1-5 and 7, ν(C=N) appears at 1602-1653 cm-1. The IR spectra of
complexes 3-7 show strong absorption bands for the coordinated stretching vibrations of the
nitrate group at about 1290 and 1490 cm-1 [6]. The band at 3298 cm−1 for L1′ can be assigned
to the N—H stretching vibration. The corresponding N—H deformation vibrations in L1′
appear at 1362 cm−1 [29,30].
1
The H NMR spectra and peak assignments are presented in the experimental section. These
peaks are assigned based on the splitting of the resonance signals, spin coupling constants
and literature data, [21,31] and are clearly in accordance with the molecular structures
determined by X-ray crystal structure analysis. The spectra of the ligands are clearly divided
into two parts; the downfield part is due to the pyridine and imine protons while the upfield
1
signals represent the -NCH2- proton resonances. The H NMR spectra of L1 and L2 show a
singlet at ca. 4.8 ppm due to the -NCH2- protons, whilst the aromatic H-atoms and imine
protons appear at 7.75-8.63 ppm. The imine protons appear as a singlet at 8.54 and 8.53 ppm
for L1 and L2, respectively. In L1′, however, the methylene protons are not equivalent and
appear as two singlets while the aromatic H-atoms and imine protons appear at 7.23-8.56
ppm. The 1H NMR spectra of complexes 1 and 2 show typical patterns for the ligands L1 (in
11

1) and L2 (in 2) together with the PPh3 protons. Inevitably, the aromatic protons of the
coordinated PPh3 ligands overlap to some extent with those of the pyridyl protons of the
ligands. Aside from the aromatic protons, which appear at 7.37–8.38 ppm, the imine protons
appear as singlets at about 8.80 ppm. A singlet at 4.98 ppm is assigned to the =NCH2-
1
protons. The H resonances of the coordinated ligands are commonly observed in 4, 5 and 7.
The imine protons appear as a singlet at about 8.74 ppm. The down-field shift of the iminic
protons in the complexes relative to those of the free ligands can be attributed to the
deshielding effect resulting from the metal coordination [32,33].
The electronic absorption spectra of the ligands L1, L1′ and L2 and the corresponding
complexes 1-7 are presented in experimental section. Since no d-d transitions are expected
for a d10 complex (1 and 2), the UV/VIS bands are assigned to MLCT or intraligand
transitions [34,35]. The absorption spectrum of 1 features a band with a true maximum at 485
nm, whereas 2 shows a clear shoulder at 303 nm. The visible range of the spectra is
dominated by metal-ligand charge transfer (MLCT) transitions, which are characteristic
features of copper(I) complexes when bonded to a conjugated organic chromophore [36].
Additional absorption bands are also observed in the spectra of 1 and 2 in the UV region. The
intensities of these bands are consistent with their assignment to ligand-centered π→π*
or/and charge-transfer transitions. The UV-Vis spectrum of the copper(II) compound 3
exhibits d–d transitions. In complex 3, a higher energy transition was observed at 483 nm due
to d–d transitions [37-40]. Strong bands at about 268 and 280 nm are assigned to a ligand
centered π→π* transition and/or charge transfer transitions. The absorption spectra of the
zinc, cadmium and mercury compounds show intense absorptions in the UV region. These
broad bands are attributed to intraligand (π→π*) and/or charge transfer transitions (MLCT).
The free ligands show a fluorescent feature with an emission around 455 nm (458 nm for L1,
449 nm for L1′ and 460 nm for L2) upon excitation at 270 nm in DMSO at room temperature.
12

Complex 1 displays a strong emission with a maximum intensity at 538 nm, while a weak
band is observed at 541 nm for complex 2. These fluorescent emissions can be assigned to a
metal-to-ligand charge transfer (MLCT) or halide-to-ligand charge transfer (XLCT) [41,42].
The zinc and cadmium compounds (4, 5 and 6) display a strong emission with maximum
intensities at about 460 nm (459 nm for 4, 463 nm for 5 and 455 nm for 6). This fluorescent
emission can be assigned to the intraligand transition of the ligand, modified by metal
coordination, because a similar emission is observed at 458 and 449 nm for the free ligands
L1 and L1′, respectively. Compared to the free ligand, the coordination compounds show a
significant enhancement of the fluorescence intensity, probably because the chelating and
bridging coordination effectively increase the rigidity of the ligands and reduce the loss of
energy by radiationless decay. Compounds 3 and 7 are non-emissive at room temperature.
3.2. Crystal structures
Selected bond lengths and angles for compounds 1–7 are given in Tables 2 and 3.
3.2.1. Structure of [Cu2(L1)(PPh3)2I2]2 (1)
X-ray structural analysis of compound 1 reveals the formation of a centrosymmetric
tetranuclear compound (Fig. 1). This compound contains four copper atoms, four iodide
anions (two terminal and two bridging), four triphenylphosphine ligands and two L1 ligands.
The coordination environment around Cu1 in 1 is pseudotetrahedral, τ4 = 0.92 for Cu1 [43]
with a large angular distortion arising from the low N19—Cu1—I1 angle (100.28(7)°). The
other five angles around the Cu1 center all lie within 5° of those of a regular tetrahedron;
however, the N19—Cu1—P1 angle (116.92(7) °) has opened up due to the steric influence of
the bulky di-imine and PPh3 ligands. The Cu1—N19 bond distance (2.063(2) Å) is similar to
13

those found in other Cu(I) pseudotetrahedral complexes [44-46]. Although a tetrahedral
geometry is to be expected for a four-coordinated Cu(I) center, the geometry about Cu2 in 1
is distorted by the restricted bite of the chelating ligand. The N1—Cu—N41 angle is 80.67(9)
°. The N41—Cu2—P2 and N1—Cu2—I2 angles are 121.30(7) and 119.94(6) °, respectively,
being somewhat larger than the ideal tetrahedral angle such that for Cu2 τ4 = 0.84 and its
coordination geometry tends towards a see-saw description [43]. The Cu—P distances are
2.230(8) and 2.196(7) Å, being in the same range as those in other tetrahedral copper
complexes [44-48]. The Cu—I bond lengths (with the I- anions fulfilling both terminal and
bridging ligand roles) of 2.587(4), 2.674(4) and 2.639(4) Å agree well with the same
distances in other tetrahedral copper complexes with iodido ligands [44-48]. In 1, L adopts
the chelating mode to one Cu(I) ion and also it adopts a bridging mode and connects two
Cu(I) ions. The dihedral angle between the pyridyl rings of each L ligand is 46.76(9) °. The
value for the N1—C43—C42—N41 torsion angle is -8.873(4) °, and a comparison with the
dihedral angle between the chelate ring and pyridine group (6.418(12) °) indicates that these
are roughly coplanar. However, the terminal pyridine ring is tilted out-of-plane with respect
to the metal chelate plane, with a calculated dihedral angle of 54.54(11) ° between the two
planes.
3.2.2. Structure of [Cu2(L2)(PPh3)2I2]n (2)
The repeat unit of this coordination polymer comprises a Cu2I2 unit with a
triphenylphosphine substituent on Cu1, and it is linked to an adjacent Cu2I2 unit by the ligand
L2, which acts as a bridge (Fig. 2). The almost square and strictly planar Cu2I2 unit is
generated by inversion symmetry, with Cu1—I1 bond distances of 2.6713(3) and 2.6586 (4)
Å and a Cu1—Cu1ii (ii = -x+1, -y+1, -z+1) separation of 2.9549(6) Å. This motif is not
unusual in Cu—I coordination chemistry, with 332 instances reported in the Cambridge
14

Structural Database[49]. A small number of representative complexes containing Cu2I2 units
with one or more pyridine based ligands on each Cu atom were found [48,50-52]. However
refining the search to include a P and pyridine based ligand on each of the Cu atoms
produced only three hits, [53-55] underlining the novelty of 1 and 2.
The Cu—I (2.6712(3) and 2.6590(3) Å) and Cu—Cu (2.9554(5) Å) distances, Table 2,
compare reasonably with those for 1, and are also similar to the mean values [Cu—I, 2.66(9)
Å and Cu—Cu, 2.9(3) Å] found for the 332 equivalent, planar Cu2I2 units in the Cambridge
database, despite the fact that this compound, with a bridging bidentate dipyridyl ligand, is
totally novel. In addition to the two bridging iodide ligands, each Cu(I) atom is coordinated to
a triphenylphosphine ligand and one N atom of the bidentate ((E)-1-(pyridin-3-yl)-N-
(pyridine-4-ylmethylene)methanamine L2 ligand, Fig. 2. Because of the positional disorder
involving this ligand, each Cu atom binds a nitrogen atom of both the 3- and 4 pyridyl
substituents of the ligand with equal occupancy. A Cu atom of an adjacent Cu2I2 unit
similarly binds to one or other of the pyridyl N atoms, again with equal occupancy,
propagating a one dimensional polymer system, Fig. 3.
The coordination geometry about the Cu atoms is again slightly distorted tetrahedral, with τ4
= 0.91, suggesting only a slight departure from Td symmetry [43]. The coordination sphere of
each Cu atom comprises two iodide ligands, forming the centrosymmetric Cu2I2 unit, one
triphenylphosphine ligand and one or other of the N atoms of the asymmetrical (E)-pyridin-3-
yl-N-(pyridin-4-ylmethylene)methanamine ligand. The L—Cu—L angles are in the range
100.56(6) to 112.662(10)°, Table 2. The bridging L2 ligands link adjacent Cu2I2(PPh3)3 units
into infinite one dimensional chains that run parallel to (110). In the crystal lattice, these
chains are further joined by weak C—H…I contacts, generating parallel columns along the
crystallographic b axis.
15

3.2.3. Structures of [ML1(NO3)2]2 [M = Cu(3), Zn(4), Cd(5)] and [Cd L1′(NO3)2]2 (6).
The structures of compounds 3-6, shown in Figs. 4 and 6, are sufficiently similar to be
discussed together. Each molecule of 3-5 lies about an inversion center and comprises two
M2+ cations linked by two L1 ligands that chelate to each metal atom through the imine N4
atom and the N3 atom of the 2-pyridyl ring, forming 5-membered chelate rings. Each ligand
binds to the other metal atom of the pair via the N5 atom of the 3-pyridyl ring. For 6 the
coordination environment is similar, except that N4 is now an amine N atom and the C=N
bond of L1 is reduced. In the L1 complexes, this coordination generates a molecular box
bounded by the Cu1—N4 bonds on one side and the two strictly parallel 3-pyridyl rings on
the other. In the case of 3, the approximate dimensions of this cavity are 5.3 x 3.1 Å, Fig.
5(a). An alternate view shows a smaller cavity, approximately 3.1 x 2.9 Å, which is bounded
by the two 3-pyridyl rings and the planes of the 2-pyridyl rings Fig. 5(b). These ring planes
for 3 are almost orthogonal, with a dihedral angle of 89.1(7)° between them. Similar cavities
are formed by the Zn and Cd analogues with the dimensions of the major cavities being 5.9 x
3.3 Å for 4, 5.8 x 3.4 Å for 5 and 4.9 x 2.9 Å for 6. The dihedral angles between the 2-pyridyl
and 3-pyridyl ring planes are 80.40(7)° for 4 and 75.21(6)° for 5. In contrast, the greater
flexibility engendered by the saturated C8—N4 linkage in L1′ widens the larger cavity to
approximately 7.4 x 2.87 Å and reduces the angle between the 2- and 3-pyridyl rings to
72.89(9)°.
The coordination of the nitrato anions to the metals in 3-6 varies in an interesting fashion as
the metal changes. According to the criteria for the assignment for nitrate binding modes
introduced by Kleywegt et al. [56], there are three common types of nitrate binding in
coordination complexes, monodentate, where only one O atom is clearly bound to the metal,
bidentate where two oxygens bind and the M—O distances are reasonably similar and finally
anisobidentate where, again, both oxygens bind but one M—O bond is significantly longer
16

than the other.
The criteria used to determine the mode of coordination are determined by differences in the
M—O and M--N bond distances and M—N—O angles [54], detailed in Fig. 7 and Table 4.
All three coordination modes are seen in these complexes, with the tendency for bidentate
coordination increasing with the radius of the metal. The binding of one of the nitrate anions
N2O4O5(O6) in 3 is anisobidentate, with the Cu1—O4 bond length being 2.1062(13) Å and
Cu1—O5 being 2.6619(15), while the N1O1O2(O3) anion is clearly unidentate. This has an
interesting impact on the coordination geometry of the Cu(II) cation. The primary
coordination sphere, discounting the longer Cu1—O5 bond, involves the two pyridyl N3 and
N5 atoms, the azomethine N4 atom and the O1 and O4 atoms of the two nitrate anions Fig.
8(a). This generates a five-coordinate, highly distorted trigonal bipyramidal geometry. The
distortion lies towards a square pyramidal structure, with the trigonality index τ5 = 0.51 (τ5 is
the parameter describing the degree of trigonal distortion and is defined as τ = (θ1-θ2)/60,
where θ1 and θ2 are the two largest ligand–metal–ligand angles; τ5 = 0 for an ideal square-
pyramid (SP) and τ5 = 1 for an ideal trigonal bipyramid (TBP) [57]). However, there is the
additional Cu1—O5 contact at 2.6619(15) Å. The O5 atom essentially caps the trigonal
bipyramid, bisecting the O4—Cu1—N4 angle in an asymmetric fashion and creating a
hugely distorted octahedral coordination environment. The Cu1--O2 contact at 2.8844(18) Å
is too long to be considered a sensible bonding distance. The coordination numbers for the
remaining L1 derivatives are somewhat more clear cut, with complex 4 having a six-
coordinate Zn atom in a severely distorted octahedral geometry, Fig. 8(b), with one
monodentate and one bidentate nitrato ligand. The larger Cd atom in 5 binds both nitrato
ligands in a bidentate fashion, leading to seven coordination and a highly distorted pentagonal
bipyramidal geometry, Fig. 8(c). Seven coordination persists for 6, but in this case the
coordination geometry is best described as a distorted capped octahedron, Fig. 8(d). An
17

alternative treatment of the metal coordination geometry when bidentate nitrate ligands are
involved has been proposed by Hanton et al. [58-60]. They argue that the small bite angle of
the bidentate nitrato ligand suggests that it can be considered to occupy just a single
coordination site. The bite angles observed here for all of the bidentate nitrato ligands are
certainly low, ranging from 51.10(4) to 56.23(5)° across the four molecules. Hence if we use
the N atoms of the bidentate chelate nitrato ligands as a proxy for the locus of the single
nitrato coordination site, the coordination geometries for complexes 4 and 5 tend more
towards trigonal bipyramidal, Fig. 9, with trigonality indices, τ5 = 0.71 for 4 and τ5 = 0.65 for
'
5 [57]. In contrast, complex 6, involving the more flexible L1 ligand, tends slightly towards
square planar with τ5 = 0.46 [57]. Furthermore, applying the same procedure to 3 reinforces
the concept of distortion towards a trigonal bipyramidal geometry with a much increased
trigonality index, τ5 = 0.72 [57]. For 3, the Cu—N bond lengths range between 1.9742(14)
and 2.0447(14) Å (Table 2) and the Cu—O bond lengths for the nitrate ions range from
2.1062(13) to 2.1743(12) Å, consistent with the corresponding bond lengths found in similar
structures [21,30,61-65]. The most closely related complexes to the Zn and Cd derivatives 4
and 5 involve the (E)-pyridin-2-yl-N-(pyridin-2-ylmethylene)methanamine and (E)-N-(1-
(pyridin-2-yl)ethylidene)pyridin-2-amine ligands, each with two 2-pyridyl rings and
-
interestingly NO3 anions as the other ligands [66]. In these complexes it was found that the
M—Nimine distance was distinctly shorter than the M—Npy distances (M= Zn, Cd) a trend that
is clearly absent in the structures of 4 and 5. It is likely, therefore, that the M—N distances
are determined by steric rather than electronic effects.
Only a single copper coordination complex of L1′ appears in the CSD, in which the metal is
chelated by one pyridyl N atom and the amine N atom, with the second pyridyl N atom being
protonated [67]. In contrast, structures of more than 200 complexes of the corresponding
symmetrical bis(pyridin-2-ylmethyl)amine appear in the database, with Cd(II) derivatives
18

well represented [68-70]. However, only one of these structures also featured nitrato ligands
[68] and no inversion dimers similar to 6 have been reported. Nonetheless the Cd—N
distances observed here are not unusual.
3.2.4. Structure of [HgL1Cl 2]n (7)
The structure of the mercury complex with L1, 7, departs markedly from those displayed by
its lighter congeners from Group 12. Certainly the metal is chelated by the 2-pyridyl N atom
and the imine N atom, but there the similarity ends as the N5 atom of the 3-pyridyl ring binds
to an adjacent Hg1 centre to propagate a coordination polymer. The Hg1 atom is in a
distorted square pyramidal coordination environment, Fig. 10, composed of two monodentate
chlorido anions, the 2-pyridyl N3 atom and the imine N4 atom, that chelates the Hg1 centre
forming a 5-membered ring. The coordination sphere is completed by the 3-pyridyl N5 atom
of an adjacent L1 ligand in the polymer chain and the proposed coordination environment is
supported by a trigonality index τ5 = 0.27 [57]. The Hg atom lies 0.776(7) Å above the best
fit N3Cl mean plane and the 2- and 3-pyridyl rings are inclined to one another at 78.8(7)°.
Chelation of an HgCl2 unit by a N-(pyridin-2-ylmethylene)methanamine fragment is not
uncommon, with 16 examples in the CSD, see for example [71-75]. The mean Hg1—N3
[2.37(8) Å] and Hg—N4 [2.45(7) Å] distances across these examples are the complete
reverse of the order found in 7, Hg1—N3 2.514(15) Å, Hg1—N4 2.345(16) Å, although the
Hg—Cl distances observed here are unremarkable. An explanation for this reversal is not
immediately obvious, particularly as the bite angle N3—Hg1—N4 of the chelate, 68.7(5)°, is
closely comparable to those found in the related structures. However, it is interesting that for
the closely comparable coordination polymer catena-poly[[dichloridomercury(II)]-µ-{N-[(E)-
pyridin-2-ylmethylidene-κN]-pyridin-3-amine-κ2N1:N3}] [75], the equivalent distances are
Hg1—N2 2.406(5) Å and Hg1—N4 2.535(6) Å; clearly the greater flexibility imparted to the
19

ligand system by the additional CH2 group in 7 has a significant effect on the Hg—N
distances in the chelate ring. The polymer chain propagates in helical spirals along a two-fold
screw axis parallel to b, Fig. 11. In the crystal, intermolecular C—H…Cl hydrogen bonds
link adjacent polymer chains, forming parallel rows along b.
4. Conclusions
We have presented the syntheses of some molecular boxes and coordination polymers by
employing three flexible N-bridging ligands (L1, L1′ and L2). From the reaction of different
metal nitrate salts, M(NO3)2 (M=Cu(II), Zn(II) and Cd(II)), with L1 and L1′, similar structures
(molecular boxes) were obtained in these cases, although the metal centers have different
geometries in these structures. When HgCl2 reacts with L1, a coordination polymer was
obtained. The metal atoms in the compounds 3-7 are present in highly distorted trigonal
bipyramidal, distorted octahedral, highly distorted pentagonal bipyramidal, distorted capped
octahedral and distorted square pyramidal environments, respectively. Dihedral angles
between the terminal pyridyl rings of L in the compounds 3-7 vary considerably from a
maximum of 89.13 ° for 3, to 80.41 and 72.89 ° for 6, with the other compounds having
intermediate values. Hence, these flexible ligands (L1 and L1′) possibly modulate their
conformations in order to meet the coordination needs of the metal polyhedra and no clear
correlation is observed between the structures of the compounds (box or chain) and the
coordination environment of the metal or the conformation of the ligands. A careful analysis
of structures 3 (4, 5 and 6) and 7 (through overlaying the metal atoms and the chelate ring
systems in both molecules) clearly shows that the positioning of the chlorido ligands in the
Hg complex (7) forces the N5 atom bound to the Hg atom into an orientation such that an
inversion dimer simply cannot form, (Fig. 12). A coordination polymer, however, is a viable
20

alternative. In contrast, the bulky nitrato ligands in 3, 4, 5 and 6 cannot adopt similar
orientations, but are ideally situated to allow the formation of inversion dimers.
Acknowledgments
Financial support from Alzahra University is gratefully acknowledged. We also thank the
University of Otago for the purchase of the diffractometer used for the data collection of 2
and 4-7, and Professor G.B. Jameson, Massey University, New Zealand for guidance over the
disorder in the structure of compound 2.
Supplementary material
CCDC 1000162-1000168 contain the supplementary crystallographic data for compounds 1-
7, respectively. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version.
References
[1] J.-M. Lehn, Angew. Chem. Int. Ed. 52 (2013) 2–17.
[2] E.A. Wilson, N.A. Vermeulen, P.R. McGonigal, A.-J. Avestro, A.A. Sarjeant, C.L. Stern,
J.F. Stoddart, Chem. Commun., 50 (2014) 9665-9668.
[3] J.-F. Ayme, J.E. Beves, C.J. Campbell, D.A. Leigh, Chem. Soc. Rev., 42 (2013) 1700-
1712.
[4] J.M. Lehn, Supramolecular Chemistry, Concepts and Perspectives, Wiley Online Library,
1995.
[5] J.E. Beves, C.J. Campbell, D.A. Leigh, R.G. Pritchard, Angew. Chem. Int. Ed., 52 (2013)
1 – 5.
[6] J.-F. Ayme, J.E. Beves, C.J. Campbell, D.A. Leigh, Angew. Chem., 126 (2014) 7957-
21

7961.
[7] J. Keegan, P.E. Kruger, M. Nieuwenhuyzen, N. Martin, Cryst. Growth Des., 2 (2002)
329-332.
[8] V.J. Catalano, A.L. Moore, Inorg. Chem., 44 (2005) 6558-6566.
[9] H. Cheng, D. Chun-ying, F. Chen-jie, M. Qing-jin, J. Chem. Soc., Dalton Trans., (2000)
2419-2424.
[10] M.J. Hannon, C.L. Painting, N.W. Alcock, Chem. Commun., (1999) 2023-2024.
[11] B.L. Fei, W.Y. Sun, K.-B. Yu, W.X. Tang, J. Chem. Soc., Dalton Trans., (2000) 805-
811.
[12] W.Y. Sun, B.L. Fei, T.A. Okamura, W.X. Tang, N. Ueyama, Eur. J. Inorg. Chem.,
(2001) 1855-1861.
[13] Y. Wang, X.M. Ouyang, T.A. Okamura, W.Y. Sun, N. Ueyama, Inorg. Chim. Acta, 353
(2003) 68-74.
[14] H.F. Zhu, L.Y. Kong, T.A. Okamura, J. Fan, W.Y. Sun, N. Ueyama, Eur. J. Inorg.
Chem., (2004) 1465-1473.
[15] B.Y. Cho, D. Min, S.W. Lee, Cryst. Growth Des., 6 (2006) 342-347.
[16] H.S. Huh, D. Min, Y.K. Lee, S.W. Lee, Bull. Korean Chem. Soc., 23 (2002) 619-622.
[17] S.W. Lee, H.J. Kim, Y.K. Lee, K. Park, J.H. Son, Y.U. Kwon, Inorg. Chim. Acta, 353
(2003) 151-158.
[18] D. Min, S. Soo Yoon, J. Hwa Lee, M. Suh, S.W. Lee, Inorg. Chem. Commun., 4 (2001)
297-300.
[19] D. Min, S. Soo Yoon, S.W. Lee, Inorg. Chem. Commun., 5 (2002) 143-146.
[20] D. Min, S.S. Yoon, D.-Y. Jung, C.Y. Lee, Y. Kim, W.S. Han, S.W. Lee, Inorg. Chim.
Acta, 324 (2001) 293-299.
[21] S. Dehghanpour, A. Mahmoudi, L. Najafi, M. Khalafbeigi, K. Jahani, Polyhedron, 53
22

(2013) 91-97.
[22] G. Saha, K.K. Sarkar, T.K. Mondal, C. Sinha, Inorg. Chim. Acta, 387 (2012) 240-247.
[23] Z.Y. Zhang, Z.P. Deng, X.F. Zhang, L.H. Huo, H. Zhao, S. Gao, CrystEngComm, 16
(2014) 359-368.
[24] S.K. Padhi, V. Manivannan, Inorg. Chem., 45 (2006) 7994-7996.
[25] S.K. Padhi, V. Manivannan, Polyhedron, 26 (2007) 1619-1624
[26] G.M. Sheldrick, SHELXS 97, Program for the solution of crystal structure, University of
Göttingen, Germany, (1997).
[27] G.M. Sheldrick, SHELX-97, Program for crystal structure refinement, University of
Göttingen, Göttingen, Germany (1997).
[28] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G. Polidori, M.
Camalli, J. Appl. Crystallogr., 27 (1994) 435-436
[29] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds,,
Wiley, 1997.
[30] T.X. Neenan, W.L. Driessen, J.G. Haasnoot, J. Reedijk, Inorg. Chim. Acta, 247 (1996)
43-49.
[31] R. Montalvo-González, A. Ariza-Castolo, J. Mol. Struct., 655 (2003) 375-389.
[32] W. Massa, S. Dehghanpour, K. Jahani, Inorg. Chim. Acta, 362 (2009) 2872-2878.
[33] M. Ruthkosky, F.N. Castellano, G.J. Meyer, Inorg. Chem., 35 (1996) 6406-6412.
[34] A.A. Del Paggio, D.R. McMillin, Inorg. Chem., 22 (1983) 691-692.
[35] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, 1984.
[36] S. Sakaki, H. Mizutani, Y. Kase, Inorg. Chem., 31 (1992) 4575-4581.
[37] B. Hathaway, J. Chem. Soc., Dalton Trans., (1972) 1196-1199.
[38] S.S. Massoud, F.A. Mautner, Inorg. Chem. Commun., 7 (2004) 559-562.
[39] G.A. McLachlan, G.D. Fallon, R.L. Martin, L. Spiccia, Inorg. Chem., 34 (1995) 254-
23

261.
[40] U. Mukhopadhyay, I. Bernal, S.S. Massoud, F.A. Mautner, Inorg. Chim. Acta, 357
(2004) 3673-3682.
[41] F.A. Mautner, M.A. Goher, Polyhedron, 18 (1998) 553-559.
[42] M. Vitale, P.C. Ford, Coord. Chem. Rev., 219 (2001) 3-16.
[43] L. Yang, D.R. Powell, R.P. Houser, Dalton Trans., (2007) 955-964.
[44] E.C. Alyea, G. Ferguson, M.C. Jennings, Z. Xu, Polyhedron, 9 (1990) 739-741.
[45] S. Dehghanpour, A.H. Mahmoudkhani, M. Amirnasr, Struct. Chem., 17 (2006) 255-262.
[46] G. Kickelbick, M. Amirnasr, A.D. Khalaji, S. Dehghanpour, Aust. J. Chem., 56 (2003)
323-328.
[47] S. Chowdhury, G.K. Patra, M.G. Drew, N. Chattopadhyay, D. Datta, J. Chem. Soc.,
Dalton Trans., (2000) 235-237.
[48] H. Oshio, T. Watanabe, A. Ohto, T. Ito, H. Masuda, Inorg. Chem., 35 (1996) 472-479.
[49] F.H. Allen, Acta Crystallogr. Section B: Struct. Sci., 58 (2002) 380-388.
[50] S.M. Fang, Q. Zhang, M. Hu, B. Xiao, L.M. Zhou, G.H. Sun, L.J. Gao, M. Du, C.S. Liu,
CrystEngComm, 12 (2010) 2203-2212.
[51] P.C. Healy, J.D. Kildea, B.W. Skelton, A.H. White, Aust. J. Chem., 42 (1989) 115-136.
[52] D. Zhang, L. Ding, W. Xu, X. Jin, D. Zhu, Chem. Lett. , (2001) 242–243.
[53] G.A. Bowmaker, J.V. Hanna, R.D. Hart, P.C. Healy, A.H. White, J.Chem. Soc., Dalton
Trans., (1994) 2621-2629.
[54] L.M. Engelhardt, P.C. Healy, J.D. Kildea, A.H. White, Aust. J. Chem., 42 (1989) 913-
922.
[55] K. Tang, T. Xia, X. Jin, Y. Tang, Acta Sci. Nat. Univ. Pek., 31 (1995) 695-702.
[56] G.J. Kleywegt, W.G. Wiesmeijer, G.J. Van Driel, W.L. Driessen, J. Reedijk, J.H.
Noordik, J. Chem. Soc., Dalton Trans., (1985) 2177-2184.
24

[57] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc., Dalton
Trans., (1984) 1349-1356.
[58] C.A. Black, L.R. Hanton, M.D. Spicer, Inorg. Chem., 46 (2007) 3669-3679.
[59] D.B. Cordes, A.S. Bailey, P.L. Caradoc-Davies, D.H. Gregory, L.R. Hanton, K. Lee,
M.D. Spicer, Inorg. Chem., 44 (2005) 2544-2552.
[60] D.B. Cordes, L.R. Hanton, Inorg. Chem. Commun., 8 (2005) 967-970.
[61] Z. Atherton, D.M.L. Goodgame, S. Menzer, D.J. Williams, Polyhedron, 18 (1998) 273-
279.
[62] D.M. Ciurtin, Y.-B. Dong, M.D. Smith, T. Barclay, H.-C. zur Loye, Inorg. Chem., 40
(2001) 2825-2834.
[63] Y.-B. Dong, M.D. Smith, H.C. zur Loye, Inorg. Chem., 39 (2000) 4927-4935.
[64] Z. Wang, R.G. Xiong, E. Naggar, B.M. Foxman, W. Lin, Inorg. Chim. Acta, 288 (1999)
215-219.
[65] M.B. Zaman, M.D. Smith, D.M. Ciurtin, H.C. zur Loye, Inorg. Chem., 41 (2002) 4895-
4903.
[66] S.K. Padhi, R. Sahu, V. Manivannan, Polyhedron, 27 (2008) 805-811.
[67] M. Soibinet, I. Déchamps-Olivier, A. Mohamadou, M. Aplincourt, Inorg. Chem.
Commun., 7 (2004) 405-409.
[68] G.H. Eom, J.H. Kim, Y.D. Jo, E.Y. Kim, J.M. Bae, C. Kim, S.-J. Kim, Y. Kim, Inorg.
Chim. Acta, 387 (2012) 106-116
[69] J. Glerup, P.A. Goodson, D.J. Hodgson, K. Michelsen, K.M. Nielsen, H. Weihe, Inorg.
Chem., 31 (1992) 4611-4616.
[70] M.C. Suen, J.C. Wang, J. Coord. Chem., 60 (2007) 257-268.
[71] D.C. Bebout, S.W. Stokes, R.J. Butcher, Inorg. Chem., 38 (1999) 1126-1133.
[72] N.M. Fallah, M.R.T.B. Olyai, H.R. Khavasi, Z. Kristallogr. NCS, 225 (2010) 717-718.
25

[73] Y.I. Kim, H.J. Seo, J.H. Kim, Y.S. Lee, S.K. Kang, Acta Crystallogr. Section E: Struct.
Rep. Online, 66 (2010) m124-m124.
[74] A. Mahmoudi, S. Dehghanpour, M. Khalaj, S. Pakravan, Acta Crystallogr. Section E:
Struct. Rep. Online, 65 (2009) m889-m889
[75] A. Mahmoudi, S. Dehghanpour, L. Najafi, M. Khalafbeigi, Acta Crystallogr. Section E:
Struct. Rep. Online, 68 (2012) m1244-m1244
26

N
N
N
L1
N
N
N
L'1
N
H
L2
N
N
Scheme 1 Chemical formulae of the ligands: (E)-N-(pyridin-2-ylmethylene)-1-(pyridin-3-
yl)methanamine (L1), 1-(pyridine-2-yl)-N-(pyridin-3-ylmethyl)methanamine (L1´) and (E)-N-
(pyridin-2-ylmethylene)-1-(pyridin-4-yl)methanamine (L2).
27

Table 1
Crystal data and structure refinement of 1-7.
1
2
3
4
5
6
7
Empirical
formula
Formula weight
T (K)
C100H88Cu4I4
N8P4
2287.46
C48H39Cu2I2N3P
2
C24H22Cu2N10O1
2
C24H22N10O12Zn C24H22Cd2N10O1 C24H26Cd2N10O1 C12H11Cl2HgN
2
2
2
3
1100.64
90(2)
769.62
100(2)
773.26
867.32
871.35
468.73
100(2)
93(2)
93(2)
93(2)
94(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
0.71073
triclinic
P-1
0.71073
triclinic
P-1
0.71073
monoclinic
C2/c
0.71073
monoclinic
P21/n
7.5968(14)
13.996(3)
13.796(2)
90.00
102.327(7)
90.00
1433.0(4)
2
0.71073
monoclinic
P21/n
7.8884(4)
14.0615(7)
13.9354(7)
90.00
102.859(2)
90.00
1506.99(13)
2
0.71073
triclinic
P-1
0.71073
monoclinic
P21/n
7.5999(8)
13.0542(12)
13.5600(13)
90.00
91.705(5)
90.00
1344.7(2)
4
8.2060(2)
17.0610(5)
18.8760(5)
115.0740(7)
101.0770(10)
92.0410(11)
2328.60(11)
1
9.6457(7)
10.5521(7)
12.0381(8)
103.642(3)
108.924(3)
90.019(3)
1122.40(13)
1
20.1660(3)
13.1830(3)
14.8650(4)
90.0000(12)
132.3600(10)
90.0000(9)
2920.11(11)
4
7.1808(16)
7.589(2)
14.824(3)
100.571(14)
97.240(13)
109.181(13)
734.8(3)
1
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (A3)
Z
-3
Dcalc (g cm )
µ (mm )
1.631
2.347
1.628
2.430
1.751
1.539
1.792
1.758
1.911
1.491
1.969
1.530
2.315
11.827
-1
F (000)
1132
1.050
542
1.050
1560
1.050
784
1.093
856
1.129
432
1.083
872
1.136
Goodness-of-fit
Final R indices
[I >2σ(I)]
R indices (all
data)
R1=0.0388,
wR2=0.0838
R1=0.0461,
wR2=0.0873
1.538 and -
1.340
R1=0.0423,
wR2= 0.0969
R1=0.0588,
wR2= 0.1033
3.274 and -
3.303
R1=0.0351,
wR2=0.0794
R1=0.0428,
wR2=0.0827
0.667 and -
0.483
R1=0.0294,
wR2=0.0657
R1=0.0385,
wR2= 0.0705
0.375 and -
0.358
R1=0.0258,
wR2=0.0681
R1=0.0349,
wR2= 0.0717
0.733 and -
0.637
R1=0.0269,
wR2=0.0602
R1=0.0321,
wR2=0.0625
0.913 and -
0.735
R1=0.0653,
wR2= 0.1786
R1=0.0729,
wR2= 0.1823
4.960 and -
3.191
Largest
difference peak
and hole (e Å-3)
28

Table 2
Selected bond distances (Å) and angles (˚) for 1–4.
1
2
3
4
Cu1–I1
Cu1– I1i
Cu1–N19
Cu1–P1
Cu1–Cu1
Cu2–N41
Cu2–N1
Cu2–P2
Cu2–I2
2.674(4)
2.639(4)
2.063(2)
2.230(8)
3.002(7)
2.061(2)
2.097(2)
2.196(7)
2.587(4)
Cu1—I1
Cu1—I1ii
Cu1—N1A
Cu1—N1Biii
Cu1—P1
Cu1—Cu1ii
2.6712(3)
2.6590(3)
2.052(3)
2.066(3)
2.2234(5)
2.9554(5)
Cu1–N5iv
Cu1–N3
Cu1–N4
Cu1–O4
Cu1–O1
Cu1–O5
1.9742(14)
1.9777(15)
2.0447(14)
2.1062(13)
2.1743(12)
2.6619(15)
Zn1—N3
Zn1—N4
Zn1—N5
Zn1—O1
Zn1—O4
Zn1—O5
2.1259(17)
2.1460(17)
2.0870(17)
2.0899(15)
2.1251(15)
2.4156(17)
N19–Cu1–P1
N19–Cu1–I1i
N19–Cu1–I1
P1–Cu1–I1i
P1–Cu1–I1
N41–Cu2–N1
N41–Cu2–P2
N1–Cu2–P2
N41–Cu2–I2
N1–Cu2–I2
P2–Cu2–I2
116.92(7) I1–Cu1–I1ii
106.91(7) P1–Cu1–I1
100.28(7) P1–Cu1–I1ii
108.50(2) P1–Cu1–N1A
112.73(2) P1–Cu1–N1Biii
80.67(9)
121.30(7)
115.28(7)
106.18(7)
119.94(6)
112.653(8)
111.676(13)
112.193(13)
117.66(13)
113.53(14)
N3-Cu1-N4 80.78(6)
N3-Cu1-N5 75.06(6)
N4-Cu1-N5 95.63(6)
O1-Cu1-N3 89.54(5)
O1-Cu1-N4 132.97(5)
O1-Cu1-N5 94.13(5)
O4-Cu1-N3 91.18(6)
O4-Cu1-N4 145.51(5)
O4-Cu1-N5 90.89(5)
N4-Zn1-N5
N3–Zn1–N4 77.05(7)
93.67(6)
O1-Zn1-N3
O1-Zn1-N4
O1-Zn1-N5
O4-Zn1-N3
O4-Zn1-N4
O4-Zn1-N5
O5-Zn1-N3
O5-Zn1-N4
O5-Zn1-N5
92.36(6)
127.95(6)
91.85(6)
89.89(6)
147.28(6)
56.23(5)
90.06(6)
93.44(6)
92.51(6)
110.70(2)
29