Self-assembled macrocyclic tetranuclear molecular square [Ni(HL)]44+ and molecular rectangle [Cu2Cl2L]2 {H2L = bis[phenyl(2-pyridyl)methanone] thiocarbazone}

Article abstract of DOI:10.1039/a909604c

The conformationally rigid, nickel(n)-based cationic molecular square [Ni(HL)]44+ and copper(n)-based neutral molecular rectangle [CujCljLjj were achieved via self-assembly from novel rigid pentadentate N4S ligand bis[phenyl(2-pyridyl)methanone] thiocarbazone(H2L). Crystal structure analyses show that the tetranuclear nickel(n) cation [Ni(HL)]₄⁴⁺ is located at the inversion center with four nickel atoms in the corners of a square with edge length Ni ... Ni ca. 4.8 A, each metal center being octahedrally coordinated by sulfur atoms, pyridine nitrogen and carbazone nitrogen atoms from two perpendicular HL~ ligands. Relative to the square of metal cations the sulfur atoms are midway between the edges of the square, each being connected to two nickel atoms with the angles Ni-S-Ni ca. 163°. The tetranuclear copper(n) complex [Cu₂Cl₂L]₂ is also located in the inversion center with four copper atoms in the corners of a rectangle. Two edges of the rectangle are Cu-S-Cu bridges with edge length Cu ... Cu of 4.51 A, the other two edges are double Cu-Cl-Cu bridges with Cu ... Cu distance of 3.41 A. Each metal center is coordinated in a tetragonal-pyramid with the sulfur atom, pyridine nitrogen atom, carbazone nitrogen atom and one chlorine atom comprising the basal plane, whereas the other chlorine atom of the symmetry-related half of the molecule occupies the apical position. The crystal structure of the free ligand is also reported for comparison. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/a909604c

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Self-assembled macrocyclic tetranuclear molecular square
[Ni(HL)]44؉ and molecular rectangle [Cu2Cl2L]2
{H2L ؍ bis[phenyl(2-pyridyl)methanone] thiocarbazone}
He Cheng, Duan Chun-ying,* Fang Chen-jie, Liu Yong-jiang, Meng Qing-jin*
Coordination Chemistry Institute, The State Key Laboratory of Coordination Chemistry,
Nanjing University, Nanjing 210093, P. R. China. E-mail: duancy@nju.edu.cn
Received 6th December 1999, Accepted 25th January 2000
Published on the Web 13th March 2000
The conformationally rigid, nickel()-based cationic molecular square [Ni(HL)]44ϩ and copper()-based
neutral molecular rectangle [Cu2Cl2L]2 were achieved via self-assembly from novel rigid pentadentate N4S
ligand bis[phenyl(2-pyridyl)methanone] thiocarbazone (H2L). Crystal structure analyses show that the
tetranuclear nickel() cation [Ni(HL)]44ϩ is located at the inversion center with four nickel atoms in the corners
of a square with edge length Ni ؒ ؒ ؒ Ni ca. 4.8 Å, each metal center being octahedrally coordinated by sulfur
atoms, pyridine nitrogen and carbazone nitrogen atoms from two perpendicular HLϪ ligands. Relative to the
square of metal cations the sulfur atoms are midway between the edges of the square, each being connected to
two nickel atoms with the angles Ni–S–Ni ca. 163Њ. The tetranuclear copper() complex [Cu2Cl2L]2 is also located
in the inversion center with four copper atoms in the corners of a rectangle. Two edges of the rectangle are Cu–S–Cu
bridges with edge length Cu ؒ ؒ ؒ Cu of 4.51 Å, the other two edges are double Cu–Cl–Cu bridges with Cu ؒ ؒ ؒ Cu
distance of 3.41 Å. Each metal center is coordinated in a tetragonal-pyramid with the sulfur atom, pyridine
nitrogen atom, carbazone nitrogen atom and one chlorine atom comprising the basal plane, whereas the other
chlorine atom of the symmetry-related half of the molecule occupies the apical position. The crystal structure
of the free ligand is also reported for comparison.
The design and study of well-arranged metal-containing macro-
cycles is one of the major current research areas in modern
supramolecular chemistry.1 Such complexes are of interest not
only for their unusual structures and the simple synthetic
methods used to prepare them, but also for their special func-
tional properties such as luminescence,2 redox activity3 and
magnetism.4 Here we report a new conformationally rigid,
and a new conformationally rigid, copper-based neutral
molecular rectangle [Cu2LCl2]2 achieved via self-assembly from
bis[phenyl(2-pyridyl)methanone] thiocarbazone.
Incorporation of such a pentadentate ligand into a supra-
molecular macrocyclic square or rectangle via self-assembly is
attractive for several reasons. Since 1990, Fujita et al.5 and
Stang et al.6 have reported many different molecular square
complexes based on square planar coordinated metal centers,
4ϩ
nickel-based cationic molecular square [NiHL]4 (Scheme 1)
Scheme 1
DOI: 10.1039/a909604c
J. Chem. Soc., Dalton Trans., 2000, 1207–1212
This journal is © The Royal Society of Chemistry 2000
1207

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Table 1 Crystallographic data for compounds H2L, 1 and 2
these 90Њ bonding angles between ligands in transition metal
complexes provide an attractive feature for constructing macro-
cyclic structures,5–7 however, there are only a few examples of
self-assembled molecular squares based on an octahedral
geometry or tetragonal pyramidal geometry at the metal
center,2,8 this is especially rare for multidentate ligands.7,8 This
work introduced a newly designed, rigid pentadentate N4S
ligand for binding to an octahedrally coordinated first-row
transition metal, thereby offering the potential of broadening
the scope of further work in this area. Polydentate ligands
containing thiocarbazone and thiosemicarbazone groups are
known to form a variety of mononuclear, dinuclear and multi-
nuclear metal complexes,9 and a number of thiosemicarb-
azones, thiocarbazones and their metal complexes have been
found to be active in cell destruction, as well as in the inhibition
of DNA systems.10 The molecular square and rectangle
reported here can add a new dimension not only to supra-
molecular, but also to biomimetic chemistry.
H2L
1
2
Molecular
formula
M
Crystal system
Space group
a/Å
C25H20N6S
C108H102N24Ni4-
O5P4F24S4
2759.08
Monoclinic
C2/c
27.045(9)
16.385(7)
29.595(9)
12372(8)
4
C50H36Cl4Cu4-
N12S2
1264.98
Monoclinic
P21/n
12.142(3)
10.625(2)
19.535(6)
2520.1(11)
2
436.53
Monoclinic
P21/c
8.677(3)
21.385(9)
12.229(5)
2157(2)
4
b/Å
c/Å
V/Å3
Z
T/K
293(2)
0.176
4870
293(2)
0.815
8968
293(2)
2.010
3559
µ/mmϪ1
No. reflections
measured
No. unique
reflections
R1
3804 [R(int) =
0.05]
0.062
8081 [R(int) =
0.12]
0.079
3365 [R(int) =
0.10]
0.073
wR2
0.12
0.16
0.82
0.11
1.03
Goodness of fit 1.03
Experimental
General
(cmϪ1): 3052 (νC–H), 3020, 1493, 1463 (m), 1440, 1389 (νC
,
C
᎐
᎐
All chemicals were of reagent grade and used without further
purification. The IR spectra were recorded on a Nicolet 170SX
FT-IR spectrophotometer with KBr pellets in the 4000–400
cmϪ1 region. 1H-NMR spectra were recorded on Am5600
Bruker spectrometers at 298 K using TMS as the internal
standard. The magnetic measurements were carried out on a
powder sample with a CHAN 2000 Faraday-type magnet-
ometer in the temperature range 75–300 K. Electrospray mass
spectra were recorded on a LCQ system (Finnigan MAT, USA)
using methanol as the mobile phase.
1
νC–N), 1292 (νN–N), 1096 (νC S), 845, 758, 740 (δC–H). H NMR
᎐
᎐
(ppm) [(CD3)2SO]: 9.03 (2H, py), 7.97 (2H, py), 7.73 (2H, py),
7.48 (2H, py), 7.44 (4H, Ph), 7.30 (4H, Ph), 7.20 (2H, Ph).
Crystals suitable for crystal determination were obtained by
slowly evaporating DMF solution in air.
Crystallography
Parameters for data collection and refinement of compounds
H2L, 1 and 2 are summarized in Table 1, selected bond
lengths and angles in the three structures are listed in Table 2.
Intensities were collected on a Siemens P4 four circle diffrac-
tometer with graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å) using the ω Ϫ 2θ scan mode. The data were correc-
ted for Lorentz-polarization effects during data reduction
using XSCANS.11 The structures were solved by direct methods
and refined on F 2 using full-matrix least squares methods using
SHELXTL version 5.0.12 Anisotropic thermal parameters were
refined for the non-hydrogen atoms.
In complex 1, The PF6 anions and the ethanol solvent
molecules are considered disordered. One of the anions is D4
disordered, with a linear F(1)–P(1)–F(6) not disordered. The
other four fluorine atoms are disordered over two positions
F(2), F(3), F(4) and F(5), as well as F(2Ј), F(3Ј), F(4Ј) and
F(5Ј), these two atom positions refined to occupancies of
0.68(1) and 0.32(1), respectively. Another anion is disordered
over two positions, P(2), F(7) to F(12), and P(2Ј), F(7Ј) to
F(12Ј), these two positions refined to occupancies of 0.80(1)
and 0.20(1), respectively. The ethanol solvent molecules were
also disordered over two positions, C(51), C(52), O(1) and
C(51Ј), C(52Ј), O(1Ј). These two positions refined to occu-
pancies of 0.68(1) and 0.32(1), respectively. The structure
was refined with distance restraints of P–F = 1.57 0.01 Å,
F ؒ ؒ ؒ F = 2.20 0.02 Å, for the disordered anions. Thermal
parameters were also restrained as for the disordered atoms in
the anions and solvent molecules. One of the phenyl rings of
complex 3 is also disordered over two positions, C(21), C(22),
C(23), C(24), C(25) and C(21Ј), C(22Ј), C(23Ј), C(24Ј), C(25Ј).
These two positions refined to occupancies of 0.79(1) and
0.21(1), respectively.
Preparations
Bis[phenyl(2-pyridyl)methanone] thiocarbazone H2L. Thio-
carbonohydrazide (0.21 g, 2 mmol), 2-benzoylpyridine (0.80 g,
4.4 mmol) and five drops of 6 M HCl were mixed in methanol
(25 mL). The solution was refluxed for 3 hours, then evaporated
to a small volume (10 mL). After cooling to room temperature,
the yellow crystalline solid formed was isolated and dried under
vacuum to give the ligand H2L. Anal. Found: C, 68.2; H, 4.8;
N, 18.9; Calc. for C25H20N6S: C, 68.8; H, 4.6; N, 19.3%. IR
(cmϪ1): 3319, 3205 (νN–H), 3051 (νC–H), 2937, 1498, 1469, 1456,
1422 (νC C, νC–N), 1228 (νN–N), 1115 (νC S), 842, 796, 760, 735
᎐
᎐
᎐
᎐
(δC–H). 1H NMR (ppm) (CD3Cl): 8.92 (2H, py), 8.45 (2H, NH),
8.03 (2H, py), 7.86 (4H, py), 7.65 (2H, Ph), 7.45–7.53 (8H, Ph).
Crystals suitable for X-ray diffraction determination were
obtained by slowly evaporating a methanol solution in air.
[Ni(HL)]4[PF6]4ؒ4EtOHؒH2O 1. The thiocarbazone H2L
(0.22 g, 0.5 mmol) and NiCl2ؒ6H2O (0.12 g, 0.5 mmol) were
mixed in 15 mL methanol. After refluxing for one hour and
cooling to room temperature, KPF6 (0.18 g, 1.0 mmol) was
added and refluxing was resumed for over two hours. The
brown precipitate formed was isolated and recrystallized from
acetonitrile–ethanol (1:1) solution. Found: C, 46.4; H, 3.8;
N, 12.0; Calc. for C108H102N24S4Ni4P4F24O5: C, 47.0; H, 3.7; N,
12.2%. IR (cmϪ1): 3622, 3329 (νN–H), 3060 (νC–H), 2896, 1593,
1559, 1506, 1460, 1444 (νC C, νC–N), 1264 (νN–N), 1095 (νC S), 841
᎐
᎐
(s) (νP–F), 760 (m), 746 (m) (δC–H). Crystals suitable for᎐crystal
determination were obtained by slowly evaporating an
acetonitrile–ethanol (1:1) solution in air.
᎐
CCDC reference number 186/1823.
See http://www.rsc.org/suppdata/dt/a9/a909604c/ for crystal-
lographic files in .cif format.
[Cu2LCl2]2 2. The thiocarbazone (0.22 g, 0.5 mmol) and
CuCl2ؒ2H2O (0.17 g, 1 mmol) were mixed in 10 mL DMF. After
stirring for 3 h, the solution was evaporated in air, the dark
green crystalline solid formed was isolated, washed by diethyl
ether, and dried under vacuum. Found: C, 47.5; H, 3.2; N, 13.5;
Calc. for C50H36N12S2Cu4Cl4: C, 47.6; H, 2.8; N, 13.4%). IR
Results and discussion
The new Schiff base H2L was prepared by the reaction of thio-
carbonohydrazide with 2-benzoylpyridine. It can, in principle,
1208
J. Chem. Soc., Dalton Trans., 2000, 1207–1212

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Table 2 Selected bond lengths (Å) and angles (Њ)a
H2L
C(13)–N(3)
N(3)–N(2)
C(13)–S(1)
1.370(4)
1.362(4)
1.649(4)
C(13)–N(4)
N(4)–N(5)
1.347(4)
1.369(4)
Complex 2
Ni(1)–S(1)
Ni(1)–S(2)
Ni(1)–N(5)
Ni(1)–N(6)
Ni(1)–N(7)
Ni(1)–N(8)
S(1)–C(13)
C(13)–N(3)
C(13)–N(4)
N(2)–N(3)
N(4)–N(5)
2.388(3)
2.450(2)
2.001(7)
2.063(6)
2.057(6)
2.029(7)
1.713(9)
1.374(10)
1.349(10)
1.373(9)
1.373(9)
Ni(2)–S(1)
2.419(3)
2.451(2)
2.066(7)
2.020(7)
2.008(7)
2.108(6)
1.723(9)
1.341(9)
1.362(10)
1.314(8)
1.369(8)
Ni(2)–S(2A)
Ni(2)–N(1)
Ni(2)–N(2)
Ni(2)–N(11A)
Ni(2)–N(12A)
S(2)–C(38)
C(38)–N(9)
C(38)–N(10)
N(8)–N(9)
Fig. 1 Molecular structure and atom numbering of [(C6H5)(C5H4N)-
᎐
probability level.
C᎐NNH]2CS [H2L]. Thermal ellipsoids are drawn at the 50%
N(10)–N(11)
N(5)–Ni(1)–N(6)
N(5)–Ni(1)–N(7)
N(5)–Ni(1)–N(8)
N(5)–Ni(1)–S(1)
N(5)–Ni(1)–S(2)
N(6)–Ni(1)–N(7)
N(6)–Ni(1)–N(8)
N(6)–Ni(1)–S(1)
N(6)–Ni(1)–S(2)
N(7)–Ni(1)–N(8)
N(7)–Ni(1)–S(1)
N(7)–Ni(1)–S(2)
N(8)–Ni(1)–S(1)
N(8)–Ni(1)–S(2)
S(1)–Ni(1)–S(2)
Ni(1)–S(1)–Ni(2)
78.6(3)
100.7(2)
177.0(3)
82.1(2)
99.0(2)
93.9(3)
104.4(3)
160.7(2)
88.3(2)
79.2(2)
91.3(2)
160.2(2)
94.9(2)
81.3(2)
93.1(1)
159.4(1)
N(1)–Ni(2)–N(2)
N(1)–Ni(2)–N(11A)
N(1)–Ni(2)–N(12A)
N(1)–Ni(2)–S(1)
N(1)–Ni(2)–S(2A)
N(2)–Ni(2)–N(11A)
N(2)–Ni(2)–N(12A)
N(2)–Ni(2)–S(1)
N(2)–Ni(2)–S(2A)
N(11A)–Ni(2)–N(12A) 77.8(2)
N(11A)–Ni(2)–S(1)
N(11A)–Ni(2)–S(2A)
N(12A)–Ni(2)–S(1)
N(12A)–Ni(2)–S(2A)
S(1)–Ni(2)–S(2A)
78.3(3)
101.7(3)
94.6(2)
159.0(2)
92.4(2)
178.3(2)
103.9(2)
81.0(2)
98.0(2)
and II, the two benzene rings III and IV plus the thiocarbazone
moiety V. The mean deviations of sets of atoms from their
best planes and the dihedral angles between them are given in
Table 3. The non-planarity of the thiocarbazone moiety appar-
ently arises from steric strain and possibly intramolecular
hydrogen bonds.
The C–S bond distance (Table 2) of 1.649(4) Å agrees well
with those in related compounds, being intermediate between
99.1(2)
80.3(2)
87.0(2)
157.9(2)
93.9(1)
167.5(1)
1.82 Å for a C–S single bond and 1.56 Å for C᎐S double
᎐
bond.14 The corresponding C(13)–N(3) and C(13)–N(4)
[1.370(4), 1.347(4) Å] bond distances are indicative of some
double bond character, suggesting the extensive delocalization
of the whole thiocarbazone moiety. This suggestion is also
supported by the N–N bond distances and other C–N bond
distances. The H(3N) ؒ ؒ ؒ N(1) (2.42 Å) and H(4N) ؒ ؒ ؒ N(6)
(2.57 Å) distances are less than normal van der Waals con-
tacts,15 suggesting possible intramolecular hydrogen bonds,
the N–H ؒ ؒ ؒ N bond angles [124Њ and 118Њ about H(3N) and
H(4N), respectively] indicate that these hydrogen bonds are
very weak.
Ni(1)–S(2)–Ni(2A)
Complex 2
Cu(1)–S(1)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–Cl(1)
Cu(1)–Cl(2B)
C(13)–N(3)
N(2)–N(3)
S(1)–C(13)
2.270(2)
2.007(6)
1.947(6)
2.219(2)
2.724(2)
1.318(9)
1.359(8)
1.786(7)
Cu(2)–S(1)
Cu(2)–N(5)
Cu(2)–N(6)
Cu(2)–Cl(2)
Cu(2)–Cl(1B)
C(13)–N(4)
N(4)–N(5)
2.286(2)
1.950(6)
2.029(6)
2.250(2)
2.729(3)
1.347(9)
1.369(8)
Structure and magnetic properties of [Ni(HL)]4[PF6]4
Interaction of the NiCl2ؒ6H2O with H2L in boiling methanol
gave the tetranuclear metal macrocyclic cation [NiHL]4
via self-assembly as shown in Scheme 1. ESI-MS (electro-
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–Cl(1)
N(1)–Cu(1)–S(1)
N(1)–Cu(1)–Cl(2B)
N(2)–Cu(1)–S(1)
N(2)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(2B)
S(1)–Cu(1)–Cl(1)
S(1)–Cu(1)–Cl(2B)
Cl(1)–Cu(1)–Cl(2B)
82.2(3)
95.7(2)
161.2(2)
97.4(2)
84.0(2)
175.6(2)
90.2(2)
97.16(9)
95.34(8)
93.96(8)
N(5)–Cu(2)–N(6)
N(5)–Cu(2)–Cl(2)
N(5)–Cu(2)–S(1)
N(5)–Cu(2)–Cl(1B)
N(6)–Cu(2)–S(1)
N(6)–Cu(2)–Cl(2)
N(6)–Cu(2)–Cl(1B)
S(1)–Cu(2)–Cl(2)
S(1)–Cu(2)–Cl(1B)
Cl(2)–Cu(2)–Cl(1B)
Cu(2)–Cl(2)–Cu(1B)
81.1(2)
173.3(2)
83.0(2)
93.1(2)
160.2(2)
96.2(2)
4ϩ
spray ionization mass spectroscopy) exhibits three peaks
at 493.3, 659.1 and 987.4 which correspond to [Ni4(H4L4)]4ϩ
,
[Ni4(H3L4)]3ϩ and [Ni4(H2L4)]2ϩ, respectively, suggesting that
the tetranuclear square fragment is the most stable conform-
ation.
94.0(2)
98.35(9)
98.58(8)
93.14(8)
86.08(8)
As shown in Fig. 2, the tetranuclear cation is located at an
inversion center with four nickel() atoms at the corners of
a square with edge length Ni ؒ ؒ ؒ Ni ca. 4.8 Å [4.73 Å for
Ni(1) ؒ ؒ ؒ Ni(2) and 4.87 Å for Ni(1) ؒ ؒ ؒ Ni(2A) (Ϫx, 1 Ϫ y,
0.5 Ϫ z)]. Each metal center is octahedrally coordinated by the
sulfur atoms, the thiocarbazone nitrogen atoms and the pyri-
dine nitrogen atoms from the two different ligands. These two
ligands bond to nickel() in the mer configuration (with pairs
of sulfur atoms and pyridine nitrogen atoms each bearing a
cis-relationship, whereas the thiocarbazone nitrogen atoms are
trans to each other), as found in related octahedral coordinated
metal thiosemicarbazone complexes.16 The sulfur atoms lie at
the mid-points of the edges of square, each being connected to
two nickel atoms with bond angles of 159.4 and 167.5Њ for
Ni(1)–S(1)–Ni(2) and Ni(1)–S(2)–Ni(1A) respectively with an
average S–Ni–S bond angle ca. 93.5Њ. The C–S bond lengths
of 1.713(9) and 1.723(9) Å for C(13)–S(1) and C(38)–S(2)
respectively, are within the normal range of a C–S single bond,
indicating that the thiocarbazone moiety HLϪ adopts the thiol
tautomeric form acting as a mono-negative ligand. The C–N
and N–N bond distances in HLϪ are intermediate between
Cu(1)–Cl(1)–Cu(2B) 86.59(8)
Cu(1)–S(1)–Cu(2) 163.71(11)
a Symmetry code A: Ϫx, y, 0.5 Ϫ z; B: Ϫx, Ϫy, 1 Ϫ z.
exhibit thione–thiol tautomerism, since it contains a thioimide
–N–C᎐S functional group.13 The ν(S–H) band at 2570 cmϪ1 is
᎐
absent from the IR spectrum of the Schiff-base, but ν(N–H) at
ca. 3205 cmϪ1 is present, indicating that in the solid state the
ligand remains as the thione tautomer. The 1H NMR spectrum
does not show any peak at ca. 4.0 ppm attributable to the SH
proton, suggesting that the thiol tautomeric form is absent even
in solution.
Fig. 1 shows an ORTEP22 plot of the molecule with atom
numbering scheme. The thiocarbazone shows a Z-Z configur-
ation about both the C(6)–N(2) and C(19)–N(5) double bond,
with the two pyridine rings positioned on the opposite side.
Although non-planar as a whole, the molecule consists of five
planar fragments (see Table 3), namely the two pyridine rings I
J. Chem. Soc., Dalton Trans., 2000, 1207–1212
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Table 3 Least-squares planes, mean deviations of atoms from individual planes, and dihedral angles between pairs of planes
H2L
Dihedral angle/Њ
Mean
Plane
Atoms defining plane
deviation/Å
I
II
III
IV
I
C(1), C(2), C(3), C(4), C(5), N(1)
0.01
0.01
0.01
0.01
0.03
II
III
IV
V
C(14), C(15), C(16), C(17), C(18), N(6)
C(7), C(8), C(9), C(10), C(11), C(12)
C(20), C(21), C(22), C(23), C(24), C(25)
C(6), N(2), N(3), C(13), S(1), N(4), N(5), C(19)
68.6
67.8
39.8
59.5
96.7
79.4
75.0
28.7
21.6
22.4
Complex 1
Dihedral angle/Њ
Mean
deviation/Å
Plane
Atoms defining plane
I
II
III
I
C(1), C(2), C(3), C(4), C(5), N(1), C(6), N(2), Ni(2), N(3), C(13), S(1)
C(14), C(15), C(16), C(17), C(18), N(6), Ni(1), N(5), C(19), N(4), S(1), C(13)
C(26), C(27), C(28), C(29), C(30), N(7), Ni(1), N(8), C(31), N(9), C(38), S(2)
C(39), C(40), C(41), C(42), C(43), N(12), Ni(2A), N(11), C(44), N(10), S(2),
C(38)
0.08
0.10
0.02
0.09
II
IЈ
IIЈ
22.0
79.5
88.7
95.5
101
14.1
IIIA
Dihedral angle/Њ
Mean
deviation/Å
Plane
Atoms defining plane
III
IV
III
IV
IIIA
IVA
C(7), C(8), C(9), C(10), C(11), C(12)
0.03
0.10
C(20), C(21), C(22), C(23), C(24), C(25)
C(7A), C(8A), C(9A), C(10A), C(11A), C(12A)
C(20A), C(21A), C(22A), C(23A), C(24A), C(25A)
22.8
31.4
18.6
18.6
5.5
22.8
Dihedral angle/Њ
Mean
Plane
Atoms defining plane
deviation/Å
IIIЈ
IVЈ
IIIЈA
IIIЈ
IVЈ
IIIЈA
IVЈA
C(32), C(33), C(34), C(35), C(36), C(37)
C(45), C(46), C(47), C(48), C(49), C(50)
C(32A), C(33A), C(34A), C(35A), C(36A), C(37A)
C(45A), C(46A), C(47A), C(48A), C(49A), C(50A)
0.03
0.01
6.0
10.8
4.9
4.9
1.1
6.0
Complex 2
Dihedral angle/Њ
Mean
deviation/Å
Plane
Atoms defining plane
I
II
III
I
II
III
IV
C(1), C(2), C(3), C(4), C(5), N(1)
C(14), C(15), C(16), C(17), C(18), N(6)
C(7), C(8), C(9), C(10), C(11), C(12)
0.01
0.02
0.02
0.07
17.8
64.3
13.3
82.0
5.1
C(6), N(2), Cu(1), N(3), C(13), S(1), N(4), N(5), Cu(2), C(19)
77.4
formal single and double bonds, pointing to extensive
delocalization over the entire molecular skeleton. The thio-
carbazone hydrogen atoms of the mono-anions HLϪ could not
be located from the difference Fourier map, and are most likely
disordered over N(4) and N(5), N(9) and N(10) for the two
mono-negative ligands, respectively. Although non-planar as a
whole, the atoms in each of the mono-anions are divided into
two planar parts I and II, IЈ and IIЈ for the two mono-negative
ligands respectively, the benzene rings lie out of the planes
(Table 3). The mean deviation of each part is ca. 0.08 Å on
average, whereas, the dihedral angle between the two HLϪ lig-
ands coordinated to the same nickel atom is ca. 92Њ on average.
The closest intermolecular distance between two HLϪ ligands
coordinated to different nickel centers is 3.69 Å, indicating
weak π–π interactions.17
ingly these are stacked as shown in Fig. 3. The closest inter-
molecular distance between stacked pairs is 3.68 Å, and the
dihedral angle between the planes in different groups is ca. 90Њ
on average. Although these stacking interactions are weak
compared to the metal–nitrogen and metal–sulfur coordinating
bonds, it could be suggested that these kinds of interactions
were important in the molecular assembly of the tetranuclear
metal macrocyclic molecular square.
The temperature dependence of the molar magnetic sus-
ceptibility χm (4Ni) and the effective magnetic moment µeff (4Ni)
for a polycrystalline sample of the tetranuclear complex 1 in the
range of 75–300 K are displayed in Fig. 4. As the temperature
is lowered, χm increases from 5.7 × 10Ϫ3 cm3 molϪ1 at room
temperature and reaches a maximum of 9.3 × 10Ϫ3 cm3 molϪ1
.
The effective magnetic moment at room temperature of 3.69
µB, which is very low compared to that expected for four
independent nickel() ions, decreases with decreasing temper-
ature and reaches 2.37 µB. The shapes of both curves are
characteristic of strong antiferromagnetic coupling among the
nickel() ions.
It is interesting to note that the eight uncoordinated benzene
rings can also be divided into two groups (III, IV, IIIA, IVA and
IIIЈ, IVЈ, IIIЈA, IVЈA). Planes in the group defined as the planes
IIIЈ, IVЈ, IIIЈA, IVЈA are almost parallel to each other (dihedral
angles between pairs of planes ca. 5Њ on average) and surpris-
1210
J. Chem. Soc., Dalton Trans., 2000, 1207–1212

View Article Online
Fig. 2 Perspective view of the molecular skeleton of the square
macrocyclic [Ni(HL)]44ϩ in 1, showing the non-hydrogen atoms of 50%
probability thermal ellipsoids. The phenyl rings and hydrogen atoms are
omitted for clarity.
Fig. 4 Thermal dependence of the molar magnetic susceptibility
χm (a) and effective magnetic moment µeff (b) for the tetra nickel()
square.
Fig. 3 Molecular structure showing the potential π–π stacking inter-
actions between the phenyl rings. Hydrogen atoms are omitted for
clarity.
The structure of [Cu2LCl2]2
Interaction of CuCl2ؒ2H2O with H2L in DMF at ambient
temperature gave a tetranuclear neutral metal complex via
self-assembly as shown in Scheme 1. No obvious magnetic sus-
ceptibility χm was measured from 75–300 K, indicating the
strong antiferromagnetic coupling among the copper() ions.
As shown in Fig. 5, the neutral tetranuclear copper()
complex can be described as a centric symmetric dimer of
dicopper() moieties. The geometry of copper atoms is five-
coordinate (4 ϩ 1) square pyramidal with the pyridine nitrogen
atom, the thiocarbazone nitrogen atom, the sulfur atom and the
chlorine atom comprising the basal plane, whereas the apical
position is occupied by the chlorine atom from the symmetry
related (Ϫx, Ϫy, 1 Ϫ z) half of the dimeric molecule, as found
in the related thiosemicarbazone copper() N2S-tridentate thio-
semicarbazone complex.18 The basal plane shows a very slight
Fig. 5 Perspective view of the molecular skeleton of the rectangular
[Cu2LCl2]2 in 2, showing the non-hydrogen atoms of 50% probability
thermal ellipsoids. The minor parts of the disordered phenyl rings and
hydrogen atoms are omitted for clarity.
tetrahedral distortion, Cu(1) lies 0.16 Å out of the plane
towards the chlorine atom at the apical position of the pyramid
[while for Cu(2) the deviation is 0.18 Å]. The bond lengths
in the basal plane agree well with those generally found in
J. Chem. Soc., Dalton Trans., 2000, 1207–1212
1211

View Article Online
B. Olenyuk, D. C. Muddiman and R. D. Smith, Organometallics,
1997, 16, 3094.
copper() complexes containing thiosemicarbazone deriv-
atives.19 The Cu(1)–Cl(2B) apical bond length (2.72 Å) falls
within the range of other metal-chloride bridged systems.20 The
Cu ؒ ؒ ؒ Cu distances are 4.51 and 3.41 Å for the sulfur bridged
pairs and chlorine bridged pairs respectively. The sulfur atom is
coordinated to two Cu() ions with a Cu–S–Cu bond angle of
163.7(1)Њ. It is suggested that this shorter Cu ؒ ؒ ؒ Cu distance
and the larger Cu–S–Cu angle contribute to the strong
magnetic exchange between the copper() centers.
Except the two benzene rings and the apex coordinated chlor-
ine atoms, the atoms in one half of the dimeric molecule are
nearly coplanar, the mean deviation from the best plane being
0.08 Å. The C–S bond distance is 1.786(7) Å, this agrees well
with the normal range of a C–S single bond,21 indicating that
the thiocarbazone moiety adopts the thiol tautomeric form act-
ing as a negative ligand, the C–N and N–N bond distances are
intermediate between formal single and double bonds, pointing
to extensive electron delocalization over the entire molecular
skeleton. Although the loss of one or two protons from the
ligand might influence the skeleton of the molecule and espe-
cially the C–N and N–N distances, the extensive delocalization
over the whole molecule means that this difference is not too
significant to the crystal structure.
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Acknowledgements
The authors are grateful for funding from the National Natural
Science Foundation of China. We thank Dr Andrew Marr,
School of Chemistry, The University of Nottingham, for his
help with the English.
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