Complexation and structural studies of a sulfonamide aza-15-crown-5 derivative

Article abstract of DOI:10.1016/j.inoche.2010.02.011

An aza-15-crown-5 derivative, N-[4-(phenyldiazo)benzenesulfonyl]-aza-15-crown-5, 1 was synthesised from commercially available starting materials in 55% yield. Compound 1, which contains a sulfonamide link between the crown ether macroring and the azobenz

Full text of DOI:10.1016/j.inoche.2010.02.011

Inorganic Chemistry Communications 13 (2010) 593–598
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Complexation and structural studies of a sulfonamide aza-15-crown-5 derivative
⁎
⁎
Marie Ioannidis, Alexander S. Gentleman, Lam Ho, Stephen F. Lincoln , Christopher J. Sumby
School of Chemistry and Physics, The University of Adelaide, Adelaide, SA 5005, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
An aza-15-crown-5 derivative, N-[4-(phenyldiazo)benzenesulfonyl]-aza-15-crown-5, 1 was synthesised from
commercially available starting materials in 55% yield. Compound 1, which contains a sulfonamide link
between the crown ether macroring and the azobenzene, readily binds alkali metals in buffered ethanol–water
(75:25 v/v, pH 6.66). Titration data for both sodium and potassium were readily fitted to a 1:1 metal ion/ligand
binding model to obtain stability constants (log K) of 4.7 0.4 and 4.8 0.2 dm3 mol−1, respectively. We also
investigated the structures of 1 and the sodium perchlorate salt of 1, [Na(1)(H2O)]2(ClO4)2, which were
determined by X-ray crystallography. [Na(1)(H2O)]2(ClO4)2 is a dimer in the solid state whereby a
sulfonamide oxygen atom from one of the [Na(1)(H2O)] cations provides solvation of the adjacent macroring
bound sodium cation. In the crystal structure, binding of a water molecule to the sodium cation is supported by
hydrogen bonding to the sulfonamide oxygen, which represents a supramolecular lariat ether-like interaction.
© 2010 Elsevier B.V. All rights reserved.
Received 9 January 2010
Accepted 18 February 2010
Available online 17 March 2010
Keywords:
Host–guest chemistry
Supramolecular chemistry
Azacrown ether
Lariat ether
Alkali metals
Studies into the host–guest chemistry of crown ether systems have
been a longstanding and very fruitful area of research [1]. For
example, aza-15-crown-5 has been incorporated into a large range of
colorimetric and fluorometric sensors for alkali and alkali earth
cations [2]. The ionophore aza-15-crown-5 has been shown to readily
and effectively bind alkali and alkali earth cations [1,2]. Ionophores of
this type, possessing aromatic groups appended to the nitrogen of the
azacrown ether have also been the focus of studies into cation⋯π
interactions in solution and the solid state [3]. These studies have
illustrated the importance of cation⋯π interactions in cation receptor
design and biology [3]. Covalently attaching further ether oxygen
donors to the nitrogen of the aza-15-crown-5 ether macroring also
improves the binding ability of this ionophore for alkali cations [1].
This class of compounds, called lariat ethers, were first reported by
Gokel [4,5] and consist of azacrown derivatives containing a flexible
arm of electron donor groups appended on the nitrogen atom of the
crown. The binding data for 15-membered ring lariat ethers contain-
ing between zero and eight additional oxygen atoms in the side arm
were obtained in methanol solutions for sodium cations. The lariat
ether containing a total of six oxygen donors binds sodium with the
highest binding constant [4,5].
complexes of azacrown ethers [6f]. As part of our recent studies on
new sensors for metal ions, we investigated the synthesis and
properties of N-[4-(phenyldiazo)benzenesulfonyl]-aza-15-crown-5,
1. Compound 1 attracted our attention because of the one-step
synthetic approach to prepare the compound and the presence of a
sulfonamide link between the azacrown ether binding unit and the
azobenzene group. As far as we are aware, there are no examples of
sulfonamide linked systems of this type in the literature. Herein, we
describe the synthesis and photophysical properties of 1, binding
constants for Na+ and K+, and crystal structures of 1 and its sodium
complex.
Compound 1 was synthesised from commercially available 4-
phenyldiazobenzenesulfonyl chloride and aza-15-crown-5 in 55%
yield (Scheme 1, see Supplementary material). The crown derivative
was isolated as a 95:5 mixture of E/Z isomers and characterised by 1H
and 13C NMR spectroscopy, mass spectrometry and absorption
spectroscopy. Heating the sample at 40 °C in the dark for 24 h
ensured complete conversion to the E-isomer, which simplified
characterisation by NMR spectroscopy. The electrospray mass
spectrum of 1 indicated the ability of 1 to readily bind alkali cations,
with a peak at m/z 486 corresponding to [Na(1)]+. The visible
absorption spectrum for 1 was measured in buffered ethanol–water
We have an established interest in investigating novel biomedical
and environmental sensors, for example the Zn2+ selective fluor-
ophores Zinquin-A and Zinquin-E [6a–e] and fluorescent alkali metal
(75:25 v/v, pH 6.66), with constant ionic strength (I=0.1 mol dm−3
,
NEt4ClO4). Compound 1 gives bright orange coloured solutions and
displays a broad absorption in the visible range with a maximum of
439 nm. Compound 1 is very weakly fluorescent (excitation 439 nm,
emission at 505 nm), consistent with related flexible azobenzene
derivatives [7].
Further confirmation of the structure of compound 1 was obtained
by X-ray crystallography. Crystals of 1 were obtained by slow
evaporation of an ethanol solution of 1 and crystallised in the
⁎
Corresponding authors. Lincoln is to be contacted at Tel.: +61 8 8303 5559; fax:
+61 8 8303 4358. Sumby, Tel.: +61 8 8303 7406; fax: +61 8 8303 4358.
E-mail addresses: stephen.lincoln@adelaide.edu.au (S.F. Lincoln),
christopher.sumby@adelaide.edu.au (C.J. Sumby).
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.02.011

594
M. Ioannidis et al. / Inorganic Chemistry Communications 13 (2010) 593–598
Scheme 1. Synthesis of 1.
monoclinic space group P21/n with one complete molecule in the
asymmetric unit [8]. The crystal structure confirms the structure
proposed on the basis of NMR spectroscopy, mass spectrometry and
CHN combustion analysis. Several features of the structure are worthy
of further discussion (Fig. 1). The E-isomer is a thermodynamically
more stable isomer and the major isomer isolated from the reaction
was assigned as this structure. This was confirmed by the crystal
structure which shows the E-isomer.
Within compound 1 the diazo moiety is not completely planar;
the torsion angles involving N9–N8–C5–C4 and C15–C10–N9–N8 are
23.0(1) and 28.3(1)°, respectively. Consequently, the twist between
the two phenyl rings in the azo moiety is 51.3(1)°. The sulfonamide
nitrogen atom (N18) is approximately perpendicular to the central
phenyl ring, with an angle of 107.5(1)° which is close to the expected
tetrahedral arrangement. The crown is then extended close to the
plane of the azo region of the molecule due to the flexible nature of
the moiety. The outcome is that the molecule is almost flat in the
solid state, which optimises the crystal packing.
Several groups have previously studied the incorporation of an
amide into an aza-15-crown-5 and the effect this has on the
structure of the macrocycle by X-ray crystallography [9]. Amide
groups were shown to rigidify the crown ether and diminish the
donor ability of the nitrogen. In the amide-containing aza-15-
crown-5 compounds the amide nitrogen is nearly planar. In the case
of 1 the nitrogen atom of the sulfonamide crown is similarly close to
a trigonal planar geometry with angles of 117.6(2) (C32–N18–C19),
118.1(2) (C32–N18–S1) and 116.3(2)° (C19–N18–S1). As the crystal
structure of 1 demonstrates, in the crystal form observed here, the
cavity of the crown moiety does not contain any solvent or guests
molecules. To get around this, the crown forms two weak
intramolecular hydrogen bonds (Fig. 1) which further stabilize the
conformation observed. The distances between the hydrogen and
the oxygen atoms are 2.84 Å (O21) and 2.98 Å (O24), while the
distances between the carbon and oxygen atoms are 3.44(1) Å and
3.89(1) Å, which lie in the range expected for weak hydrogen
bonding interactions. Crystal packing of 1 was completed by further
weak intermolecular hydrogen bonding interactions of the crown
moiety with other molecules of compound 1.
constants for complexes of 1 with sodium and potassium were
determined by monitoring changes in absorption of 1 at 439 nm upon
titrating 1 with standardized MClO4 [10] solutions (M=Na, K) in
buffered ethanol–water (75:25 v/v, pH 6.66). The titration data for
both sodium and potassium was readily fitted to a 1:1 metal ion/
ligand binding model (see Supplementary materials) to obtain
stability constants (log K) of 4.7 0.4 and 4.8 0.2 dm3 mol−1
,
respectively (Table 1). In the titration, a linear response was observed
upon addition of the metal ion, up to a sharp end point where the
concentration of the M+ is equal to that of the ligand, after which no
further change in absorbance was observed. This indicates that nearly
stoichiometric complexation occurs upon addition of one equivalent
of M+, and that the resulting 1:1 complexes are stable.
The measured stability constants obtained for 1 with sodium
and potassium were higher than anticipated, particularly as the
aza-15-crown-5 macroring possesses only four oxygen donors and
an electron deficient sulfonamide nitrogen, and the measurements
were carried out in a coordinatively competitive solvent mixture
(Table 1). The values obtained for 1 contrast markedly with those
reported for the parent aza-15-crown-5, [4] which binds sodium
and potassium in methanol much less efficiently than 15-crown-5
or N-methylaza-15-crown-5 [4]. As shown in Table 1, the binding
constants obtained for 1 are more consistent with values obtained
for sodium and potassium binding by lariat ethers rather than parent
1-aza-15-crown-5 derivatives such as N-methylaza-15-crown-5 [4].
This led us to further investigate the binding of 1 and alkali cations.
Based on chemical models of compound 1 bound to a sodium cation
and the crystal structure of 1 we wondered if the oxygen atom(s) of the
sulfonamide derivative were also involved in binding to the alkali
metal. The trigonal planar sulfonamide nitrogen atom would allow the
oxygen atoms of the sulfonamide to protrude slightly over the cavity of
the crown that could allow these donors to form electrostatic
interactions with an alkali metal atom (Fig. 2a). A further possibility
was the interaction of the azo-dye moiety of 1 with the alkali metal, a
cation⋯π-interaction (Fig. 2b), although this would only occur for the
less stable Z-isomer of the sulfonamide.
The known binding preferences of the aza-15-crown-5 moiety [1]
led us to investigate the binding of 1 with alkali metal cations. Binding
Table 1
Binding constants for 1-aza-15-crown-5 derivatives and lariat ether analogues.
Crown ether derivative
Cation Log K
(dm3 mol−1
T
(°C)
Solvent
Reference
)
15-crown-5
Na+
K+
3.32 0.12
3.5 0.2
1.70
2.72
3.39
4.97
4.23
4.54
4.42
25
25
25
25
25
25
25
25
25
25
MeOH
MeOH
MeOH
MeOH
[11,12]
[12]
[4]
[1]
[4]
[6]
[6]
[4]
[1]
Aza-15-crown-5
Na+
K+
N-Methylaza-15-crown-5 Na+
N-[2-(10-Ethyl-9-anthryl) Na+
ethyl]aza-15-crown-5
N-(3,6-dioxaheptyl)-
aza-15-crown-5
1
MeOH
CH3CN
CH3CN
MeOH
MeOH
75:25
K+
Na+
K+
Na+
4.7 0.4
This work
EtOH/water
75:25
EtOH/water
Fig. 1. A perspective view of 1 with selected atom labeling. The weak CH⋯O hydrogen
bonds are shown by dashed bonds and the disorder of the azo moiety (a second E form)
is not shown.
K+
4.8 0.2
25
This work

M. Ioannidis et al. / Inorganic Chemistry Communications 13 (2010) 593–598
595
Fig. 2. Representations of two potential modes of binding for 1 with Na+: (a) with an additional contact with one or two sulfonamide oxygen atoms and (b) a cation⋯π-interaction.
NMR spectra of 1 and 1 with added sodium perchlorate in
methanol-d4 (Fig. 3b and a, respectively) revealed limited changes
due to binding of sodium. The most significant changes in chemical
shift are observed for the hydrogen atoms of the azacrown, while little
or no change was observed for the protons of the azobenzene moiety of
1. This suggests that a cation⋯π interaction does not play a significant
role in binding the sodium cation, particularly in polar solvents.
Neither of the possibilities outlined in Fig. 2 were shown to occur
in the solid state. In the crystal structure of the sodium complex of 1
a dimeric structure [Na(1)(H2O)]2(ClO4)2 was obtained whereby a
water molecule bound to the sodium is hydrogen-bonded to a
sulfonamide oxygen atom of 1. Crystals of 1 bound to sodium were
obtained by slowly evaporating an ethanol–water 75:25 v/v solu-
tion of 1 and sodium perchlorate (1:2 excess of sodium). The
structure of [Na(1)(H2O)]2(ClO4)2 crystallises in the monoclinic
space group P21/n with the sodium cation sitting in the crown cavity
of a molecule of 1 and also bound to a water molecule (disordered
over two sites) [13]. The asymmetric unit is completed by a non-
coordinated perchlorate counterion. The dimeric cationic unit in the
crystal structure [Na(1)(H2O)]2 (Fig. 4) sits on a centre of inversion.
The seven coordinate sodium cation sits approximately 1.12 Å
above the centroid of the donors of the crown ether moiety. There are
four typical Na–O bond lengths and, as expected, a much longer bond
to the sulfonamide nitrogen atom with a bond length of 2.9672(15) Å.
The sulfonamide nitrogen atom of 1 in [Na(1)(H2O)]2(ClO4)2 has a
geometry that is a closer to tetrahedral, with bond angles of 113.9(1)
(C32–N18–C19), 114.6(1) (C32–N18–S1) and 114.6(1)°(C19–N18–S1).
A coordinated water molecule and the sulfonamide oxygen atom of
another molecule of 1 complete the coordination of the sodium. In the
crystal structure, the sodium complex forms a dimeric cationic structure
[Na(1)(H2O)]2 in which one of the sulfonamide oxygen atoms coor-
dinates to the sodium cation with a bond distance of 2.4209(13) Å. A
very similar arrangement was observed for a sodium iodide salt of
amide derivative of monoaza-18-crown-6 [9]. The azobenzene groups
are located on opposite sides of the [Na(1)(H2O)]2 assembly and, within
the extended structure, lie over the crown moiety of other dimeric
dications. As noted, the coordinated water molecule in the structure is
hydrogen-bonded to the sulfonamide oxygen atom (an O33–H33B⋯O16
distance of 2.27 Å and an O33⋯O16 distance of 3.00 Å). This arrange-
ment represents what we have likened to a supramolecular lariat ether-
like interaction (Fig. 5), where instead of having a covalently tethered
ether oxygen in a lariat ether type structure, a hydrogen-bonded water
molecule provides additional oxygen donors.
The unexpected arrangement observed in the crystal structure of
[Na(1)(H2O)]2(ClO4)2 led us to further consider the behavior of 1 and
alkali metal cations. The Gaussian '03 suite of programs [14,15] was
Fig. 3. 1H NMR spectra in methanol-d4 of (a) the sodium complex of 1, [Na(1)]+, and (b) 1.

596
M. Ioannidis et al. / Inorganic Chemistry Communications 13 (2010) 593–598
Fig. 4. A perspective view of the cationic moiety ([Na(1)(H2O)]2) in the crystal structure of [Na(1)(H2O)]2(ClO4)2. The disorder of the coordinated water molecule is not shown.
Selected bond lengths: Na1 O34 2.284(6), Na1 O33 2.3015(18), Na1 O17B 2.4209(13), Na1 O21 2.4365(14), Na1 O30 2.4415(13), Na1 O24 2.4457(15), Na1 O27 2.4822(15), and Na1
N18 2.9672(15).
used to investigate the relative energies of various conformations for
the sodium crown-ether assembly. Two starting configurations were
considered for compound [Na(1)]+. The first configuration represents
a proposed cation⋯π-interaction between the sodium cation and the
azobenzene functional group (Z-isomer of the sulfonamide). The
second configuration considered has the azobenzene functional group
directed away from the macroring to represent the potential
interaction of the sodium cation with the two sulfonamide oxygen
atoms (E-Isomer). Both configurations were optimised at the HF and
B3LYP level to determine which method would be most suitable to
perform further computational investigations on the compound.
Fig. 6 shows the structures of the two minima obtained from the
HF and B3LYP calculations (Structures 1a and 1b, respectively). Both
methods show that the E-isomer (Structure 1a) is the more
energetically favourable configuration (energy differences between
the optimised structures: ΔEHF =0.36 eV, ΔEB3LYP =0.25 eV). This is
consistent with the preferred conformation of 1 in solution and in the
solid state, as well as the NMR data, which indicates that a cation⋯π
interaction does not play a role in the binding of the sodium cation in
polar solvents. In addition to this, the azobenzene functional group in
structure 1a appears to pivot slightly around the sulfonamide bond so
that one of the oxygen atoms interacts with the sodium cation. This is
not surprising as sodium is highly oxophilic, making the interaction
between the sulfonamide oxygen atom and the sodium cation more
favourable than the cation⋯π interaction.
functional group possessing the ability to pivot around this bond to
afford the two possible configurations mentioned earlier. From the
B3LYP structure, the bond length was determined to be 1.903 Å and in
the HF structure, the bond length was determined to be 1.754 Å. In the
crystal structure, the bond length was 1.644(1) Å. As clearly observed,
the bond length determined using the HF method compares better
with the crystal structure bond length than that determined using the
B3LYP method. Therefore, the HF method was deemed more suitable
than the B3LYP method to perform additional calculations with.
As the crystal structure of {[Na(1)(H2O)]2}2+ reveals, additional
oxygen donors can bind to the sodium cation. Therefore, two water
molecules were made to interact with structure 1a in order to
demonstrate that they can easily be accommodated around the sodium
cation. Fig. 7 shows the structure of the sodium aza-15-crown-5
derivative with two water molecules bound around the sodium cation
optimised at the HF/6–31 g level. As observed in Fig. 7, both water
molecules can bind quite easily to the sodium cation via their oxygen
atoms (Na–OW =2.385 Å, Na–OW′=2.386 Å). In addition to this,
hydrogen bonds are also formed between the hydrogen atoms on the
water molecules and the two sulfonamide oxygen atoms (O–HW
=
1.892 Å, O′–HW′=1.900 Å). As a consequence of these interactions, the
twisting of the azobenzene functional group around the sulfonamide
bond, as observed in structure 1a, has been inhibited as the water
molecules have competitively bound to the sodium cation. All bond
distances mentioned previously, as well as other Na–O and Na–N bond
distances, are similar to those observed in the crystal structure for the
coordinated water molecule.
To determine which method was more reliable to perform
additional calculations on compound [Na(1)]+, the lengths of the
sulfonamide bond calculated from the HF and B3LYP methods were
compared to the value obtained from the crystal structure. This bond
length was chosen as the deciding factor due to the azobenzene
Herein we have reported the synthesis of an aza-15-crown-5
derivative, N-[4-(phenyldiazo)benzenesulfonyl]-aza-15-crown-5, 1
containing a sulfonamide link between the crown ether macroring
and the azobenzene. Compound 1 was synthesised from commercially
available starting materials in 55% yield and, as expected, readily
binds alkali metals in buffered ethanol–water (75:25 v/v, pH 6.66).
Visible absorption titration data for both sodium and potassium was
fitted to a 1:1 metal ion/ligand binding model to obtain stability
constants (log K) of 4.7 0.4 and 4.8 0.2 dm3 mol−1, respectively.
We have described the structures of 1 and the sodium perchlorate
salt of 1, [Na(1)(H2O)]2(ClO4)2, in the solid state. [Na(1)(H2O)]2(ClO4)2
is a dimer in the solid state whereby a sulfonamide oxygen atom from
one of the [Na(1)(H2O)] cations provides solvation of the adjacent
macroring bound seven coordinate sodium cation. In the crystal
structure of [Na(1)(H2O)]2(ClO4)2, binding of a water molecule to the
sodium cation is supported by hydrogen bonding to the sulfonamide
oxygen, which represents a supramolecular lariat ether-like interaction.
While the solvation of the crown ether bound sodium cation in the
solution is not known, a calculated structure was examined, which
Fig. 5. A view of the crystal structure showing hydrogen bonding of the sulfonamide
oxygen to a water molecule that is also bound to the sodium.

M. Ioannidis et al. / Inorganic Chemistry Communications 13 (2010) 593–598
597
Fig. 6. The structures of the minima obtained for the two isomers of [Na(1)]+ from the HF and B3LYP calculations (Structures 1a and 1b, respectively).
Fig. 7. A calculated structure demonstrating that the supramolecular ‘lariat ether’ interaction is possible for [Na(1)(H2O)2]+
.
illustrates that two water molecules bound to the sodium cation can
Appendix A. Supplementary data
form hydrogen bonds with the oxygen atoms of the sulfonamide group.
An alternative binding mode was also observed in silico whereby the
sulfonamide group pivots around the N–S bond to allow one of the
oxygen atoms of the sulfonamide group to form a bond to the oxophilic
sodium cation.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.inoche.2010.02.011.
References
[1] (a) C.J. Pedersen, Angew. Chem. Int. Ed. Engl. 27 (1988) 1021;
(b) J.W. Steed, Coord. Chem. Rev. 215 (2001) 171;
Acknowledgements
(c) G. Gokel (Ed.), Crown Ethers and Cryptands, The Royal Society of Chemistry,
Cambridge, UK, 1991.
[2] (a) A.P. de Silva, D.B. Fox, A.J.M. Huxley, T.S. Moody, Coord. Chem. Rev. 205
(2000) 41;
The authors thank the University of Adelaide for funding and the
Australian Research Council for an Australian Post-Doctoral Fellowship
to C.J.S (DP0773011). The University of Otago, Dunedin, New Zealand
(Prof. Lyall Hanton) and the Rigaku Corporation, Tokyo, Japan (Drs
Masataka Maeyama, Kazuaki Aburaya and Kimiko Hasegawa) are
acknowledged for providing access to facilities for X-ray crystallogra-
phy. A data collection for compound [Na(1)(H2O)]2(ClO4)2 was
undertaken on the PX1 beamline at the Australian Synchrotron, Victoria,
Australia and the Australian Synchrotron is thanked for funding travel
and accessto the PX1beamline(AS091). The views expressed herein are
those of the authors and are not necessarily those of the owner or
operator of the Australian Synchrotron.
(b) B. Valeur, I. Leray, Coord. Chem. Rev. 205 (2000) 3;
(c) J.F. Callan, A.P. de Silva, D.C. Magri, Tetrahedron 61 (2005) 8551;
(d) D.W. Domaille, E.L. Que, C.J. Chang, Nat. Chem. Biol. 4 (2008) 168;
(e) M.S.T. Gonçalves, Chem. Rev. 109 (2009) 190.
[3] G.W. Gokel, L.J. Barbour, R. Ferdani, J. Hu, Acc. Chem. Res. 35 (2002) 878.
[4] (a) R.A. Schultz, D.M. Dishong, G.W. Gokel, J. Am. Chem. Soc. 104 (1982) 625;
(b) R.A. Schultz, B.D. White, D.M. Dishong, K.A. Arnold, G.W. Gokel, J. Am. Chem.
Soc. 107 (1985) 6659.
[5] (a) F.R. Fronczek, V.J. Gatto, C. Minganti, R.A. Schultz, R.D. Gandour, G.W. Gokel,
J. Am. Chem. Soc. 106 (1984) 7244;
(b) R.D. Gandour, F.R. Fronczek, V.J. Gatto, C. Minganti, R.A. Schultz, B.D. White, K.A.
Arnold, D. Mazzocchi, S.R. Miller, G.W. Gokel, J. Am. Chem. Soc. 108 (1986)4078.
[6] (a) P. Coyle, P.D. Zalewski, J.C. Philcox, I.J. Forbes, A.D. Ward, S.F. Lincoln, I.
Mahadevan, A.M. Roe, Biochem. J. 303 (1994) 781;

598
M. Ioannidis et al. / Inorganic Chemistry Communications 13 (2010) 593–598
(b) P.D. Zalewski, S.H. Millard, I.J. Forbes, O. Kapaniris, A. Slavotinek, W.H. Betts,
[11] J.D. Lamb, R.M. Izatt, C.S. Swain, J.J. Christensen, J. Am. Chem. Soc. 102 (1980) 475.
[12] F. Arnaud-Neu, R. Delgado, S. Chaves, Pure Appl. Chem. 75 (2003) 71.
[13] Selected details of data collection and structure refinement for compound
[Na(1)(H2O)]2(ClO4)2: Formula C22H31ClN3NaO11S, monoclinic, space group P21/n,
Mr 604.00, orange rod, 0.30×0.10×0.10 mm, a=10.202(3), b=25.310(7),
A.D. Ward, S.F. Lincoln, I. Mahadevan, J. Histochem. Cytochem. 42 (1994)
877;
(c) K.M. Hendrickson, T. Rodopoulos, P.-A. Pittet, I. Mahadevan, S.F. Lincoln, D.A.
Ward, T. Kurucsev, P.A. Duckworth, I.J. Forbes, P.D. Zalewski, W.H. Betts, J. Chem.
Soc. Dalton Trans. (1997) 3879;
(d) M.C. Kimber, I.B. Mahadevan, S.F. Lincoln, A.D. Ward, E.R.T. Tiekink, J. Org.
Chem. 65 (2000) 8204;
(e) K.M. Hendrickson, J.P. Geue, O. Wyness, S.F. Lincoln, A.D. Ward, J. Am. Chem.
Soc. 125 (2003) 3889;
c=10.439(3) Å, β=96.411(4), V=2678.7(12) Å3, Z=4, Dcalcd=1.498 g cm-3
,
μ=0.301 cm-1, 2θ=55° data collected 20598, unique data 6089 (Rint=0.031), obs.
data [IN2σ(I)] 5048, no. parameters 353, no. restraints 2, R1 0.0355 (obs. data), wR2
0.0846 (all data), GOF 1.045. The coordinated water molecule in the structure was
modeled as being disordered over two sites (O33, 80%; O34, 20%).
(f) J.P. Geue, N.J. Head, A.D. Ward, S.F. Lincoln, Dalton Trans. (2003) 521.
[7] S.J. Isak, E.M. Eyring, J.D. Spikes, P.A. Meekins, J. Photochem. Photobiol. A: Chem
134 (2000) 77.
[14] Geometry optimisations and harmonic vibrational frequency calculations were
performed using the ab-initio Hartree–Fock (HF) method and the B3LYP density
functional in the Gaussian '03 suite of programs.[16] The harmonic vibrational
frequency calculations were performed to ensure that the optimised structures
were indeed true minima (0 imaginary frequencies). All atoms were treated with
the split-valence double-zeta 6–31 g Pople-type basis set. Calculations involving
the addition of diffuse and polarisation functions to this basis set were also
performed on the E and Z-Isomers of compound [Na(1)]+, but were found to yield
very similar results to the 6–31 g basis set. Due to this and the large increase in
calculation time upon the addition of these functions to the basis set, further
calculations were performed with the standard 6–31 g basis set.
[15] M.J. Frisch, G.W.T., H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A.
Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, H.N.G.A. Petersson,
M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C.
Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi,
C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J.
Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K.
Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul,
S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,
R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, et al., Gaussian 03, Gaussian, Inc, Pittsburgh PA, 2003.
[8] Selected details of data collection and structure refinement for compound 1:
Formula C22H29N3O6S, monoclinic, space group P21/n, Mr 463.54, orange rod,
0.88×0.16×0.16 mm, a=10.916(2), b=9.564(1), c=22.350(3) Å, β=101.314(6),
V=2288.1(5) Å3, Z=4, Dcalcd=1.346 g cm-3, μ=0.185 cm-1, θ range=2.86–27.00°
data collected 22268, unique data 4970 (Rint =0.032), obs. data [IN2σ(I)] 4425, no.
parameters 308, no. restraints 2, R1 0.0460 (obs. data), wR2 0.1097 (all data), GOF
1.047. The azo moiety of the structure is disordered with another E form of the
structure present in the crystal (major component 68%; minor component 32%). The
two restraints are used to maintain appropriate distances for the minor disorder
component.
[9] (a) C.F. Martens, A.P.H.J. Schenning, M.C. Feiters, R.J.M. Nolte, G. Beurskens, P.T.
Beurskens, Inorg. Chim. Acta 190 (1991) 163;
(b) C.F. Martens, A.P.H.J. Schenning, M.C. Feiters, G. Beurskens, J.M.M. Smits, P.T.
Beurskens, W.J.J. Smeets, A.L. Spek, R.J.M. Nolte, Supramol. Chem. 8 (1996) 31;
(c) K. Kirschke, H. Baumann, B. Costisella, M. Ramm, Liebigs Ann. Chem. (1994)877;
(d) V.W.-W. Yam, K.M.-C. Wong, V.W.-M. Lee, K.K.-W. Lo, K.-K. Cheung,
Organometallics 14 (1995) 4034;
(e) E.S. Meadows, L.J. Barbour, R. Ferdani, G.W. Gokel, J. Supramol. Chem. 1
(2001) 111.
[10] Caution! Whilst no problems were encountered in the course of this work,
perchlorate salts are strong oxidising agents and are potentially explosive and
should be handled on a small scale with appropriate care.