Synthesis and X-ray structures of cadmium-containing dinuclear double helicates derived from ligands containing N-oxide units

Article abstract of DOI:10.1039/b711039a

The syntheses of two novel polydentate pyridyl-thiazolyl ligands which contain an N-oxide unit on the central pyridyl ring are reported. Reaction of either of these ligands with Cd(ClO₄)₂·6H ₂O results in the formation of a dinuclear double helicate. The solid state structures of these transition metal helicates demonstrate the ability of the N-oxide unit to partition the ligands into two separate binding domains. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/b711039a

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/njc | New Journal of Chemistry
Synthesis and X-ray structures of cadmium-containing dinuclear double
helicates derived from ligands containing N-oxide units
Georgios Bokolinis,a T. Riis-Johannessen,wb John C. Jefferyb and Craig R. Rice*a
Received (in Durham, UK) 18th July 2007, Accepted 30th August 2007
First published as an Advance Article on the web 7th September 2007
DOI: 10.1039/b711039a
The syntheses of two novel polydentate pyridyl-thiazolyl ligands which contain an N-oxide unit
on the central pyridyl ring are reported. Reaction of either of these ligands with Cd(ClO4)2 ꢀ 6H2O
results in the formation of a dinuclear double helicate. The solid state structures of these
transition metal helicates demonstrate the ability of the N-oxide unit to partition the ligands into
two separate binding domains.
this compound with either chloroacetone or 2-(a-bromo-
acetyl)pyridine gave ligands L1 and L2, respectively.
1. Introduction
Although the ligand L1 is insoluble in common organic
solvents, reaction with Cd(ClO4)2 ꢀ 6H2O in MeCN produced a
clear pale yellow solution which gave ions in the ESI-MS at
m/z 966 and 1409, corresponding to {[Cd2(L1)](ClO4)3}+ and
{[Cd2(L1)2](ClO4)3}+, indicating the formation of a dinuclear
double-stranded helicate. The solid-state structure was con-
firmed from X-ray crystallographic analysis. In the complex
cation, two Cd2+ ions are coordinated by two bridging ligands
in a double helicate arrangement (Fig. 1 and 2). Both ligands
are partitioned into two tridentate binding domains, with the
N-oxide acting as a bridging bidentate donor to both cad-
mium(II) ions. The NCCN torsion angles between the terminal
pyridyl-thiazole domain and central pyridine N-oxide, range
from 39(1)–43(1)1. As a consequence of the bridging oxygen
atoms in the {Cd(m-O2)Cd}4+ core, the metal–metal distance
(i.e. the effective helical pitch length) is quite short (4.027(1) A)
when compared to other cadmium-containing helicates.14,15
The Cd–O(N-oxide) distances range from 2.327(3)–2.355(3) A,
whilst those to the N-donors lie in the range 2.256(4)–2.537(4)
A (Table 1). Each of the two cadmium centres is further
coordinated by one oxygen atom of a bridging perchlorate
anion. By interacting with the Cd(II) ion in the neighbouring
cation, these interstitial perchlorates link adjacent helicates
end-on throughout the lattice. The infinite columns propagate
along the crystallographic c-axis, but unlike previously ob-
served packing motifs,16 the helicate units alternate between
having P- and M-screw senses.
Formation of transition metal helicates from the self-assembly
of organic ligands and transition metal ions has received
considerable attention in recent years.1–6 One of the main
considerations for the successful self-assembly of these species
is the inherent information held within the ligand strand. If the
ligand is sufficiently instructed or ‘‘pre-programmed’’ it will
partition into different binding domains and coordinate two or
more metal ions, thus preventing the formation of mono-
nuclear complexes. We have previously shown how ligands
that contain a mixture of pyridyl and thiazolyl N-donor
groups form a variety of helical complexes whose geometries
are determined, in part, by the natural break of the ligands
into distinct binding domains imposed by the presence of the
thiazole units in the oligopyridyl chain.7
In this paper, we describe the use of pyridyl N-oxides to
partition ligands into different binding domains. To the best of
our knowledge, this is the first example of the use of N-oxide
ligands for the formation of transition metal helicates,
although the formation of mononuclear complexes from N-
oxides of 2,20:60,200-terpyridine and 2,20:60,200:600,2000-quater-
pyridine have been reported.8,9
2. Results and discussion
Both ligands L1 and L2 were synthesized as shown in Scheme
1. The starting material in both cases was 2,20:60,200-terpyridine
tris-N-oxide, which was converted to the 6,600-dicyano deriva-
tive by reaction of trimethylsilyl cyanide and benzoyl chloride
in refluxing CH2Cl2. Further reaction with hydrogen sulfide
gas gave the 6,600-dithioamide in excellent yield. Reaction of
In a similar manner to L1, in its non-complexed form L2 is
insoluble in common organic solvents. However, reaction with
Cd(ClO4)2 ꢀ 6H2O in MeNO2 produces a clear pale yellow
solution, the ESI-MS of which shows ions at m/z 1662, 1352
and
{[Cd(L2)2](ClO4)}+ and {[Cd(L2)](ClO4)}+ species, respec-
tively. The formation of dinuclear double helicate
782,
corresponding
to
{[Cd2(L2)2](ClO4)3}+,
a Department of Chemical and Biological Sciences, University of
Huddersfield, Huddersfield, UK HD1 3DH. E-mail:
c.r.rice@hud.ac.uk; Fax: (+44)1484 472182;
Tel: (+44)1484 473759
a
[Cd2(L2)2]4+ in the solid-state was confirmed from single
crystal X-ray diffraction studies (Fig. 3). The structure shows
two distorted octahedral cadmium cations coordinated by two
ligands. Each of the ligands coordinate via the central N-oxide
and the two terminal bidentate pyridyl-thiazole domains. The
b School of Chemistry, University of Bristol, Cantocks Close, Bristol,
UK BS8 1TS
w Current address: Section de Chimie et Biochimie, Universite
de Geneve, Sciences II, 30 quai Ernest-Ansermet, 1211 Geneve 4,
Switzerland.
´
ꢁc
This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
New J. Chem., 2008, 32, 115–119 | 115

View Article Online
Scheme 1 Synthesis of ligands L1 and L2.
N-oxide again acts as a bridging bidentate donor coordinating
both cadmium cations, with Cd–O bond lengths ranging
from 2.373(3)–2.395(3) A (Table 2). The Cd–N distances
involving the terminal pyridyl-thiazole domains range from
2.299(4) to 2.593(4) A (Fig. 4). However, the pyridyl units
adjacent to the central N-oxide of the terpyridyl domain have
Cd–N distances between 2.732(3)–2.772(3) A; interactions
which are rather too long to be considered bonding. These
units may thus be considered as non-bonding or hypodentate.
Again the ‘‘twist’’ caused by partitioning of the ligand strands
about the central pyridine N-oxide evokes NCCN torsion
angles in the range 32(1)–38(1)1. The pitch length of this
helicate (4.347(1) A) is slightly longer than that of
[Cd2(L1)2]4+ but is still quite short when compared to other
cadmium-containing helicates.14,15
Comparison of these complexes with others derived from
similar ligands and Cd(II) demonstrate that the N-oxide unit is
instrumental in partitioning of the ligand. For example, reac-
tion of a ligand strand identical to L2 (but which does not have
a central N-oxide unit) results in the formation of a trinuclear
double helicate.14 In this case, the ligand partitions into three
different binding domains consisting of two terminal pyridyl-
thiazole bidentate units and a central terdentate terpyridyl
unit. Thus, the three Cd(II) ions occupy two different coordi-
nation environments, with the unique central cadmium ion
coordinated by two terpyridyl units (one from each ligand)
Fig. 2 Structure of the complex cation [Cd2(L1)2(ClO4)2]2+ showing
the {Cd(m-O2)Cd} core.
Fig. 1 Structure of the complex cation [Cd2(L1)2(ClO4)2]2+
.
ꢁc
This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2007
116 | New J. Chem., 2008, 32, 115–119

View Article Online
Table 1 Selected bond distances (A) and angles (1) for [Cd2(L1)2]-
(ClO4)4 ꢀ CH3CO2CH2CH3
Table 2 Selected bond distances (A) and angles (1) for [Cd2(L2)2]-
(ClO4)4 ꢀ 3CH3NO2
Cd(1)–N(61)
Cd(1)–N(11)
Cd(1)–O(81)
Cd(1)–O(31)
Cd(1)–N(71)
Cd(1)–N(21)
Cd(1)–O(1B)
2.256(4)
2.277(4)
2.335(3)
2.355(3)
2.452(4)
2.456(4)
2.644(4)
Cd(2)–N(51)
Cd(2)–N(101)
Cd(2)–O(31)
Cd(2)–O(81)
Cd(2)–N(41)
Cd(2)–N(91)
Cd(2)–O(1C)
2.297(5)
2.300(4)
2.327(3)
2.332(3)
2.480(4)
2.537(4)
2.713(4)
Cd(1)–N(91)
Cd(1)–N(21)
Cd(1)–O(111)
Cd(1)–O(41)
Cd(1)–N(11)
Cd(1)–N(81)
2.299(4) Cd(2)–N(61)
2.315(4) Cd(2)–N(131)
2.373(3) Cd(2)–O(41)
2.377(3) Cd(2)–O(111)
2.558(4) Cd(2)–N(141)
2.593(4) Cd(2)–N(71)
2.326(3)
2.331(4)
2.388(3)
2.395(3)
2.478(4)
2.580(4)
N(91)–Cd(1)–N(21)
N(91)–Cd(1)–O(111)
N(21)–Cd(1)–O(111)
N(91)–Cd(1)–O(41)
N(21)–Cd(1)–O(41)
O(111)–Cd(1)–O(41)
N(91)–Cd(1)–N(11)
N(21)–Cd(1)–N(11)
O(111)–Cd(1)–N(11)
O(41)–Cd(1)–N(11)
N(91)–Cd(1)–N(81)
N(21)–Cd(1)–N(81)
O(111)–Cd(1)–N(81)
O(41)–Cd(1)–N(81)
N(11)–Cd(1)–N(81)
153.1(2) N(61)–Cd(2)–N(131)
116.4(1) N(61)–Cd(2)–O(41)
88.4(1) N(131)–Cd(2)–O(41)
87.4(1) N(61)–Cd(2)–O(111)
114.7(1) N(131)–Cd(2)–O(111)
62.6(1) O(41)–Cd(2)–O(111)
99.6(1) N(61)–Cd(2)–N(141)
67.9(1) N(131)–Cd(2)–N(141)
91.3(1) O(41)–Cd(2)–N(141)
153.1(1) O(111)–Cd(2)–N(141)
67.4(1) N(61)–Cd(2)–N(71)
93.3(1) N(131)–Cd(2)–N(71)
159.0(1) O(41)–Cd(2)–N(71)
98.0(1) O(111)–Cd(2)–N(71)
108.7(1) N(141)–Cd(2)–N(71)
153.2(1)
117.1(1)
87.6(1)
88.1(1)
114.1(1)
62.1(1)
98.5(1)
68.4(1)
92.6(1)
153.9(1)
66.8(1)
95.2(1)
156.0(1)
95.3(1)
110.6(1)
N(61)–Cd(1)–N(11)
N(61)–Cd(1)–O(81)
N(11)–Cd(1)–O(81)
N(61)–Cd(1)–O(31)
N(11)–Cd(1)–O(31)
O(81)–Cd(1)–O(31)
N(61)–Cd(1)–N(71)
N(11)–Cd(1)–N(71)
O(81)–Cd(1)–N(71)
O(31)–Cd(1)–N(71)
N(61)–Cd(1)–N(21)
N(11)–Cd(1)–N(21)
O(81)–Cd(1)–N(21)
O(31)–Cd(1)–N(21)
N(71)–Cd(1)–N(21)
N(61)–Cd(1)–O(1B)
N(11)–Cd(1)–O(1B)
O(81)–Cd(1)–O(1B)
O(31)–Cd(1)–O(1B)
N(71)–Cd(1)–O(1B)
N(21)–Cd(1)–O(1B)
145.7(1)
126.0(1)
85.8(1)
88.0(1)
122.6(1)
60.8(1)
72.7(1)
116.4(1)
66.7(1)
92.8(1)
111.9(1)
72.5(1)
95.6(1)
66.7(1)
158.3(1)
76.1(1)
69.8(1)
143.0(1)
156.1(1)
99.2(1)
102.5(1)
N(51)–Cd(2)–N(101)
N(51)–Cd(2)–O(31)
N(101)–Cd(2)–O(31)
N(51)–Cd(2)–O(81)
N(101)–Cd(2)–O(81)
O(31)–Cd(2)–O(81)
N(51)–Cd(2)–N(41)
N(101)–Cd(2)–N(41)
O(31)–Cd(2)–N(41)
O(81)–Cd(2)–N(41)
N(51)–Cd(2)–N(91)
N(101)–Cd(2)–N(91)
O(31)–Cd(2)–N(91)
O(81)–Cd(2)–N(91)
N(41)–Cd(2)–N(91)
O(1C)–Cd(2)–N(101)
O(1C)–Cd(2)–N(51)
O(1C)–Cd(2)–N(44)
O(1C)–Cd(2)–N(91)
O(1C)–Cd(2)–O(31)
O(1C)–Cd(2)–O(81)
146.9(2)
122.3(2)
89.1(1)
86.7(1)
120.9(1)
61.2(1)
72.6(2)
116.9(1)
66.6(1)
97.5(1)
111.0(1)
70.8(1)
97.5(1)
64.9(1)
161.1(1)
78.0(1)
73.2(1)
77.4(1)
121.4(1)
130.7(1)
159.9(1)
with L2, the N-oxide ring of the central terpyridyl unit will prevent
the ligand from efficiently coordinating to one metal ion.
3. Experimental
3.1 General details
and the two identical terminal cadmium ions coordinated by a
bidentate pyridyl-thiazole unit. In the case of L2, the central
terpyridyl unit cannot act as a terdentate unit due to the
N-oxide, which effectively separates the ligand into two dis-
tinct binding domains.
All reagents and starting materials were purchased from
Aldrich and/or Lancaster and were used without further
1
purification. H NMR spectra were obtained on a Bruker 400
MHz NMR instrument and mass spectrometry was performed
on a Micromass Quattro VG quadrupole and a Bruker Micro-
TOF LC mass spectrometer. 2,20,60,200-terpyridine-1,10,100-triox-
ide was prepared via oxidation with H2O2 in acetic acid.10
Cadmium complexes of the non-functionalised analogue of
L1 (i.e. the same potentially pentadentate ligand but without
the N-oxide unit) have not been reported to date. However,
studies carried out on a similar potentially pentadentate
pyridyl-thiazole ligand, containing a pyridyl–thiazole–pyri-
dyl–thiazole–pyridyl chain, showed the formation of a mono-
nuclear complex in which the cadmium ion is coordinated by a
near-planar pentadentate ‘‘equatorial’’ ligand.15 Although it can-
not be assumed that the non-functionalised analogue of L1 would
act in a similar fashion, it may be reasonable to expect that, as
3.2 Synthesis
3.2.1 Synthesis of 2,20,60,200-terpyridine-6,600-dicarbonitrile-
10-oxide. To a suspension of 2,20,60,200-terpyridine-1,10,100-tri-
oxide (0.4 g, 1.4 mmol) in dichloromethane (30 cm3), benzoyl
Fig. 4 Structure of the complex cation [Cd2(L2)2]4+ showing the
{Cd(m-O2)Cd} core.
Fig. 3 Structure of the complex cation [Cd2(L2)2]4+
.
ꢁc
This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
New J. Chem., 2008, 32, 115–119 | 117

View Article Online
chloride (0.66 g, 4.7 mmol) and trimethylsilyl cyanide (0.78 g,
7.9 mmol) were added and the solution refluxed for 20 h. The
resulting white solid was isolated via filtration giving the 6,600-
solution gave [Cd2(L1)2](ClO4)4 as colourless crystals. Yield:
0.0079 g, 47%. ESI-MS: m/z 1409 {[Cd2(L1)2](ClO4)3}+. Ele-
mental analysis calculated for C46H34N10Cd2Cl4O18S4: C,
36.6; H, 2.3; N, 9.3%. Found: C, 36.4; H, 2.5; N, 8.8%.
1
dicyano derivative. Yield: 0.41 g, 96%. H NMR [400 MHz,
(CD3)2SO, 70 1C]: d (ppm) 8.79 (2H, d, J = 7.47; py), 8.19
(2H, dd, J = 8.00, 8.00; py), 8.09 (4H, d, J = 7.90; py), 7.66
(1H, t, J = 7.96 Hz; py). ESI-MS: m/z 300.1 [M + H+].
3.2.6 Preparation of [Cd2(L2)2](ClO4)4. To a suspension of
L2 (0.010 g, 0.018 mmol) in nitromethane (2 cm3),
Cd(ClO4)2 ꢀ 6H2O (0.0075 g, 0.018 mmol) was added and the
solution was stirred until dissolution was complete. Filtration
followed by slow diffusion of diethyl ether into the solution
gave [Cd2(L2)2](ClO4)4 as colourless crystals. Yield: 0.008 g,
51%. ESI-MS: m/z 1662 {[Cd2(L2)2](ClO4)3}+. Elemental
analysis calculated for C62H38N14Cd2Cl4O18S4 ꢀ MeNO2: C,
41.5; H, 2.3; N, 11.5%. Found: C, 41.9; H, 2.3; N, 11.1%.
3.2.2 Synthesis of 6,600-dithioamide-2,20,60,200-terpyridine-
10-oxide.
2,20,60,200-Terpyridine-6,600-dicarbonitrile-10-oxide
(0.41 g, 1.4 mmol) was dissolved in a mixture of DMF (20
cm3) and triethylamine (2 cm3), and H2S gas was slowly
bubbled through this solution and a brown/beige precipitate
was formed. The solution was filtered and concentrated.
Addition of ethanol (5 cm3) gave a yellow precipitate which
was isolated by filtration giving 6,600-dithioamide-2,20,60,200-
3.3 Crystallographyz
1
terpyridine-10-oxide as a yellow solid. Yield: 0.35 g, 70%. H
Diffraction intensity data were collected on a Bruker SMART
CCD area-detector diffractometer with Mo-Ka radiation (l =
0.71073 A). Intensities were integrated11 from several series of
exposures, each exposure covering 0.31 in o, and the total data
set being a sphere. Absorption corrections were applied based
on multiple and symmetry-equivalent measurements.12 The
structure was solved by direct methods and refined by least
squares on weighted F2 values for all reflections.13
NMR [400 MHz, (CD3)2SO, 70 1C]: d (ppm) 10.31 (2H, s;
–NH2), 10.05 (2H, s; –NH2), 8.83 (2H, d, J = 8.00; py), 8.56
(2H, d, J = 7.89; py), 8.47 (2H, d, J = 7.97; py), 8.11 (2H, dd,
J = 7.99, 7.99; py), 7.62 (1H, t, J = 8.00 Hz; py). ESI-MS: m/z
390.1 [M + Na+].
3.2.3 Synthesis of L1. The 6,600-dithioamide-2,20,60,200-ter-
pyridine-10-oxide (0.1 g, 0.27 mmol) and chloroacetone (0.05
g, 0.54 mmol) were heated to 80 1C in anhydrous DMF (25
cm3) for 2 h and a brown precipitate was formed. The
precipitate was collected by filtration and washed with ether
(2 cm3) to give the ligand L1 as its hydrochloride salt. The free
base was prepared by suspending the L1 ꢀ HCl in concentrated
ammonia (0.88 sg, 20 cm3) and leaving the mixture for 12 h.
The suspension was filtered and the solid was washed with
ethanol (2 cm3) and diethyl ether (2 cm3) to give the ligand L1
.
3.3.1 Crystal
data
for
[Cd2(L1)2](ClO4)4 CH3-
CO2CH2CH3. C50H42Cd2Cl4N10O20S4, M = 1597.78, mono-
clinic, space group P2(1)/c, a = 23.568(4), b = 12.894(2), c =
21.345(4) A, b = 110.065(4)1, V = 6093(2) A3, Z = 4, Dcalc
=
1.742 Mg mꢂ3, F(000) = 3200, m = 1.093 mmꢂ1, crystal
dimensions 0.4 ꢃ 0.3 ꢃ 0.2 mm, T = 173(2) K. A total of
64 281 reflections were measured in the range 1.83 r y r
27.521 (hkl range indices ꢂ30 r h r 30, ꢂ16 r k r 16, ꢂ27
r l r 27), 13 984 independent reflections (Rint = 0.0539). The
structure was refined to F2 to wR2 = 0.1615, R1 = 0.0548
[8783 reflections with I 4 2s(I)] and GOF = 0.992 on F2 for
812 refined parameters, largest difference peak and hole 1.603
1
as a beige solid. Yield: 0.073 g, 62%. L1 ꢀ HCl: H NMR [400
MHz, (CD3)2SO, 70 1C]: d (ppm) 8.68 (2H, d, J = 7.72; py),
8.18 (4H, d, J = 7.30; py), 8.09 (2H, dd, J = 7.89, 7.89; py),
7.70 (1H, t, J = 7.90 Hz; py), 7.42 (2H, s; th), 2.51 (6H, s;
–CH3). ESI-MS: m/z 443.1 [M+].
and ꢂ1.600 eAꢂ3
.
3.3.2 Crystal data for [Cd2(L2)2](ClO4)4 3CH3NO2.
.
3.2.4 Synthesis of L2. The 6,600-dithioamide-2,20,60,200-ter-
pyridine-10-oxide (0.050 g, 0.14 mmol) and 2-(a-bromoacetyl)-
pyridine (0.051 g, 0.25 mmol) were heated to 80 1C in DMF
(20 cm3) for 2 h and a brown precipitate was formed. The
precipitate was collected by filtration and washed with ethanol
(3 cm3) and diethyl ether (3 cm3) to give the ligand L2 as its
hydrobromide salt. The free base was prepared by suspending
the L2 ꢀ HBr in concentrated ammonia (0.88 sg, 20 cm3) and
leaving the mixture for 12 h. The suspension was filtered and
the solid was washed with ethanol (2 cm3) and diethyl ether (2
cm3) to give the ligand L2 as a brown solid. Yield: 0.039 g,
49%. L2 ꢀ HBr: 1H NMR [400 MHz, (CD3)2SO, 70 1C]: d
(ppm) 8.75 (2H, py), 8.69 (2H, py), 8.48 (2H, s; th), 8.37 (2H,
py), 8.28 (2H, py), 8.24 (2H, py), 8.18 (2H, py), 8.02 (2H, py),
7.75 (1H, py), 7.45 (2H, py). ESI-MS: m/z 569.1 [M+].
C65H47Cd2Cl4N17O24S4, M = 1945.04, triclinic, space group
ꢀ
P1, a = 11.4892(8), b = 13.6419(9), c = 23.7577(16) A, a =
93.2420(10), b = 99.9830(10), g = 97.9550(10)1, V =
3619.6(4) A3, Z = 2, Dcalc = 1.785 Mg mꢂ3, F(000) =
1952, m = 0.944 mmꢂ1, crystal dimensions 0.4 ꢃ 0.2 ꢃ 0.2
mm, T = 173(2) K. A total of 27 891 reflections were
measured in the range 1.51 r y r 27.621 (hkl range indices
ꢂ14 r h r 14, ꢂ17 r k r 14, ꢂ30 r l r 30), 15 653
independent reflections (Rint = 0.0411). The structure was refined
to F2 to wR2 = 0.0927, R1 = 0.0439 [9053 reflections with I 4
2s(I)] and GOF = 0.906 on F2 for 1111 refined parameters,
largest difference peak and hole 1.902 and ꢂ1.011 eAꢂ3
.
4. Conclusions
The syntheses of two symmetric polydentate pyridyl-thiazolyl
3.2.5 Preparation of [Cd2(L1)2](ClO4)4. To a suspension of
L1 (0.005 g, 0.011 mmol) in acetonitrile (2 cm3),
Cd(ClO4)2 ꢀ 6H2O (0.0046 mg, 0.011 mmol) was added and
the solution was stirred until dissolution was complete. Filtra-
tion followed by slow diffusion of diethyl ether into the
ligands, whose central unit comprises a pyridine N-oxide
z CCDC 654463, [Cd2(L1)2]4+, and 654464, [Cd2(L2)2]4+. For crystal-
lographic data in CIF or other electronic format, see DOI: 10.1039/
b711039a
ꢁc
This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2007
118 | New J. Chem., 2008, 32, 115–119

View Article Online
moiety, have been described. Reaction of either of these
ligands with Cd(ClO4)2 ꢀ 6H2O results in the formation of a
dinuclear double-stranded helicate complex. Comparison of
these complexes with those formed from analogous and/or
related non-functionalised ligands, demonstrates how N-oxide
functionalisation of the central pyridine ring induces the
ligand to partition into two discreet binding domains.
D. Ward, New J. Chem., 2005, 29, 904; (b) Q. Z. Sun, Y. Bai, G. J.
He, C. Y. Duan, Z. H. Lin and Q. J. Meng, Chem. Commun., 2006,
2777; (c) M. Cantuel, F. Gumy, J. C. G. Bunzli and C. Piguet,
Dalton Trans., 2006, 2647; (d) M. Hutin, R. Frantz and J. R.
Nitschke, Chem.–Eur. J., 2006, 12, 4077.
7 (a) C. R. Rice, S. Worl, J. C. Jeffery, R. L. Paul and M. D. Ward,
¨
¨
Chem. Commun., 2000, 1529; (b) C. R. Rice, S. Worl, J. C. Jeffery,
R. L. Paul and M. D. Ward, J. Chem. Soc., Dalton Trans., 2001,
550; (c) C. R. Rice, C. J. Baylies, J. C. Jeffery, R. L. Paul and M. D.
Ward, Inorg. Chim. Acta, 2001, 324, 331.
8 A. J. Amoroso, M. W. Burrows, T. Gelbrich, R. Haigh and M. B.
Hursthouse, J. Chem. Soc., Dalton Trans., 2002, 2415.
Acknowledgements
9 A. J. Amoroso, M. W. Burrows, A. A. Dickinson, C. Jones, D. J.
Willock and W.-T. Wong, J. Chem. Soc., Dalton Trans., 2001, 255.
10 R. P. Thummel and Y. Jahng, J. Org. Chem., 1985, 50, 3635.
11 SAINT integration software, Siemens Analytical X-ray Instruments
Inc., Madison, WI, 1994.
12 G. M. Sheldrick, SADABS, Program for absorption correction with
the Siemens SMART system, Institute for Inorganic Chemistry,
University of Gottingen, Germany, 1996.
¨
13 SHELXTL program system version 5.1, Bruker Analytical X-ray
Instruments Inc., Madison, WI, 1998.
14 Previous cadmium-containing helicates derived from pyridyl-thia-
zole ligands have pitch lengths ranging from 4.259–4.632 A; C. R.
Rice, C. J. Baylies, H. J. Clayton, J. C. Jeffery, R. L. Paul and M.
D. Ward, Inorg. Chim. Acta, 2003, 351, 207.
This work was supported by both EPSRC and the University
of Huddersfield.
References
1 (a) J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995;
(b) J. W. Steed and J. L. Atwood, Supramolecular Chemistry, John
Wiley and Sons, Chichester, 2000.
2 M. J. Hannon and L. J. Childs, Supramol. Chem., 2004, 16, 7.
3 (a) M. Albrecht, Chem. Rev., 2001, 101, 3547; (b) M. Albrecht,
Chem. Soc. Rev., 1998, 27, 281.
4 C. Piguet, G. Bernardinelli and G. Hopfgartner, Chem. Rev., 1997,
97, 2005.
5 E. C. Constable, Polynuclear Transition Metal Helicates, in Com-
prehensive Supramolecular Chemistry, ed. J.-P. Sauvage, Elsevier,
Oxford, 1996, vol. 9, p. 213.
6 For recent examples of metallo-helicates, see: (a) S. P. Argent, H.
Adams, L. P. Harding, T. Riis-Johannessen, J. C. Jeffery and M.
15 C. R. Rice, C. J. Baylies, L. P. Harding, J. C. Jeffery, R. L. Paul
and M. D. Ward, Polyhedron, 2003, 22, 755.
16 J. C. Jeffery, T. Riis-Johannessen, C. J. Anderson, C. J. Adams, A.
Robinson, S. P. Argent, M. D. Ward and C. R. Rice, Inorg. Chem.,
2007, 46, 2417.
ꢁc
This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
New J. Chem., 2008, 32, 115–119 | 119