The assembly of "s3N"-ligands decorated with an azo-dye as potential sensors for heavy metal ions

Article abstract of DOI:10.1039/c7dt00569e

An "S₃N-ligand azo-dye" conjugate has been synthesised with a view to the development of a sensor for heavy metal ions. Complexation of this system with Ag(i), Hg(ii) and Cu(ii) salts has been investigated and an X-ray structure has been obtained for a Hg(ii) complex. Complexation of the conjugated dye to these metals results in a bathochromic shift in the absorption maximum of the azo dye, an effect which is most pronounced for Cu(ii).

Full text of DOI:10.1039/c7dt00569e

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J.W. McDouall, C. Muryn, J. Raftery, I. Vitorica-Yrzebal and P. Quayle, Dalton Trans., 2017, DOI:
10.1039/C7DT00569E.
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ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
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The Assembly of “S3N” – Ligands Decorated with an Azo-Dye as
Potential Sensors for Heavy Metal Ions†
O. K. Rasheed,a J. J. W. McDouall, a C. A. Muryn,a J. Raftery,a I. J. Vitorica-Yrezabala and P. Quayle*a
Received 00th January 20xx,
Accepted 00th January 20xx
An “S3N-ligand azo-dye” conjugate has been synthesised with a view to the development of a sensor for heavy metal ions.
Complexation of this system with Ag(I), Hg(II) and Cu(II) salts has been investigated and an X-ray structure obtained for a
Hg(II) complex. Complexation of the conjugated dye to these metals results in a bathochromic shift in the absorption
maximum of the azo dye, an effect which is most pronounced for Cu(II).
DOI: 10.1039/x0xx00000x
www.rsc.org/
was confirmed spectroscopically and also by way of a single crystal
X-ray analysis.
Introduction
In recent years the synthesis and co-ordination chemistry of mixed-
donor ligand systems, especially those which contain both hard and
soft donor sets, has attracted considerable attention.1a-l Recently
we reported a general method for the synthesis of mixed hard-soft
donor macrocycles1m and their subsequent conjugation2a with a
representative dye with the ultimate aim of developing metal-
responsive sensors which are capable of active transport to specific
organelles in biological systems.2b,c As a continuation of these
studies we wished to develop a robust route to the synthesis of
macrocyclic pyridine-containg azo-dyes with a view to establishing
whether such systems would ligate soft metal ions with
a
concomitant change in their absorption spectra.3 This construct
would then be incorporated into a sensor for the detection of
specific metal ions of biological interest.4 Our initial studies
focussed on the synthesis of derivatives of 8, an “S3N” tetradentate
ligand5a which is known to bind to heavy metal ions.5 In practice we
elected to prepare 6 which was viewed as a key intermediate for
the synthesis of a variety of peripherally functionalised macrocyles
as exemplified by the dye-crown conjugate 13.
Scheme 1. Synthesis of S3N ligands
The X-ray structure of 6 (Figure 1) proved to be similar to that
previously reported5b for 8 in that torsion angles about the -S-C-C-S
moiety are all close to 180°, presumably in an order to maximise
lone pair-lone pair repulsion.8
Results and discussion
The synthesis of 6 was readily accomplished using the methodology
developed
by
Vögtle.5a
Reaction
of
4-bromo-2,6-
At this stage we wished to investigate an appropriate method
for the conjugation of a “reporter” dye unit with the pyridine ring of
the macrocycle, of which one of the plethora of palladium-catalysed
coupling reactions (e.g. Heck or Stille reaction) appeared to be most
convenient. After some investigation we concluded that the most
efficient approach to this coupling reaction, leading to 13, was via a
Suzuki reaction between an appropriate boronate ester such as 12
and the macrocycle 6 (Scheme 2). In the event the key boronate
esters 10 and 12 were found to be readily accesible9 from the
palladium catalysed coupling between either 3 and 11 with B2pin2, 9
(in 74% and 79% yield respectively).
bis(bromomethyl)pyridine6, which itself was readily accessible from
chelidamic acid,7 with commercially available 2,2-thiodiethanethiol
in the pressence of KOH as base, in a ternary solvent system
(aqueous ethanol-toluene), cleanly afforded the desired thia-crown
6, a colourless crystalline solid, in 48% yield. Macrocycle 8 was
similarly prepared, and in a marginally better yield of 59%, from the
di-bromide 7 as reported previously.5a The structure of the crown 6
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spectroscopy. The 1H NMR spectra of complexes 15
-17 in
DMSO-d6 (Figure 4) were characterised by a downfield shift of
the benzylic, methylene protons, H1, (ꢀδ ca. 0.3 ppm in each
case) when compared to the resonances of these hydrogens in
the free ligands, an observation which is in keeping with
literature precedent.5a In addition, complex formation also
resulted in the splitting of the H2,3-methylene protons,
originally observed as a broadened singlet at ca.
the free ligand, into two broadened multiplets which appeared
between δ 2.5-2.8 ppm, as illustrated in Figure 4
δ 2.5 ppm in
.
Figure 1: X-ray crystal structure of macrocycle 6 (Ellipsoids at 50% probability
level. Selected bond lengths and torsion angles are to be found in the ESI).
O
OCH3
Gratifyingly the Suzuki10 reactions between 6 and 12 and 3 with
10 also proceeded in acceptable yields, affording the desired
thiocrown-azo dye hybrid 13 and di-ester 14 in yields of 57% and
53% respectively. Both 13 and 14 were obtained as crystalline solids
whose structures were confirmed by way of single crystal X-ray
diffraction studies (Figure 2). The X-ray structure of 13 again
revealed that the macrocycle adopts a conformation in which the
torsion angles about the S-C-C-S- motif are close to 180°,
presumably in order to minimise lone pair-lone pair repulsions.8, 11a
All of ther sulfur atoms are exo-disposed11a,b with respect to the
macrocycle while the pyridine moiety is orientated such that the
nitrogen lone pair is axial with respect to the plane containing the
macrocyclic core.
Pd(dppf)Cl2, dry AcOK
N
O
O
B
OCH3
3
+
O
Dioxane, 80 °C
24 h; 87%
B
2
O
O
10
9
OCH3
O
B
O
Pd(dppf)Cl2, dry AcOK
Dioxane, 80 °C
N
+
9
N
N
N
12
H3CO
24 h; 94%
S
N
S
S
I
11
Pd(PPh3)4; Cs2CO3
N
N
6 + 12
13
Having developed a route to the requisite azo-dyes 13 and 14
we have briefly investigated their complexation with
representative, “soft” metal ions including silver (I), copper (II) and
mercury (II). The metal complexes of the macrocycles 6, 8 and di-
ester 14 were also investigated for comparison purposes. Hence,
reaction of each of the ligands 6, 8 and 13 with one molar
equivalent of silver nitrate in methanolic dichloromethane (1:1)
afforded the silver complexes 15-17. The formation of complexes
15-17 was inferred from analytical data and by 1H NMR
O
O
N
DMF,100 °C
24 h; 74%
H3CO
O
Pd(PPh3)4; Cs2CO3
3 + 10
O
N
N
DMF,100 °C
24 h; 74%
14
H3CO
Scheme
2.
Suzuki
reaction
leading
to
functionalised
azo-dyes.
Figure 2: X-ray crystal structures of ligand 13 and azo-dye 14 (Ellipsoids at 50% probability level. Selected bond lengths and torsion angles are to be found in the ESI).
2 | J. Name., 2012, 00, 1-3
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each case, occupied by a halide ligand (either Cl- or I-). The large
Hg2+ cation lies above the mean plane of the “S3N” cavity.
Overall charge neutrality in these complexes is now maintained
by the presence of halide-bridged dimer, [Hg2X6]2-, in which
mercury adopts highly distorted tetrahedral geometries (see ESI
for details). The X-ray structures of these complexes are similar
Y
N
+
-
Complex
Y
H
Br
Z
Mn
Ln
ꢀ
ꢀ
15
16
17
18
19
20
21
22
23
Ag(I)
Ag(I)
Ag(I)
NO3
NO3
ꢀ
Ln
Mn+
S
S
ꢀ
NO3
ꢀ
H
Br
Z
Cu(II) NO3
S
ꢀ
Cu(II) NO3
ꢀ
Cu(II) NO3
Hg(II) Clꢀ
Hg(II) Iꢀ
N
N
H
Br
Z
to that previously reported5d for
8
·2(HgCl2) except that, in the
-HgCl]+ and
Hg(II) Iꢀ
latter case, the structure is best represented as [
8
H3CO
Z
[HgCl3]- in which the counter anion adopts a trigonal planar co-
ordination geometry which is weakly bound to the macrocycle-
bound mercury centre. The binding of Hg2+ to the macrocyclic
Table 1. Complexes prepared in this study.
Ligation of 6, 8 and 13 to silver is also associated with
changes to the aromatic region of their 1H NMR spectra (Figure
1
core of 13 is also inferred from H NMR data where the benzylic
protons in the Hg2+ complex experience line broadening and a
slight downfield shift (ꢀδ of ca. 0.03 ppm) when compared to
the those in the free ligand.
1
). The changes noted in the H NMR spectrum of the azo-dye
4
13 upon complexation with Ag+ are also similar to those
1
observed when the H NMR spectrum of 13 was conducted in
the presence of TFA in CD2Cl2. This observation implies that, in
the case of 13 at least, the pyridine nitrogen is co-ordinated to
silver during complexation (Figure 3). Unfortunately, although
the available spectroscopic data is also indicative of an
association of the Ag+ ion with ligands 6, 8 we were not able to
grow crystals crystals of sufficient quality to obtain their X-ray
structures.
Reaction of Cu(II)nitrate trihydrate with ligand
6 afforded
the green-coloured complex 19 which yielded crystals of
crystallographic quality upon slow recrystallisation from
CH2Cl2-MeOH. The X-ray structure of 19 (Figure 3) showed the
copper to be in a distorted octahedral environment with the
three sulphur atoms of the ligand being equatorially disposed.
The remaining equatorial co-ordination site was occupied by a
η1-nitrato ligand while the remaining axial co-ordination sites
were occupied by the pyridyl nitrogen of the macrocycle and a
molecule of water.12 sulphur atoms of the ligand equatorially
disposed. Charge neutrality in this case is maintained by an
additional nitrate anion which does not appear to be bound
directly to the copper centre. The observed Cu(1)-N(1) bond
length of 1.978(3) Å was considerably shorter than those of
the Cu-S bonds (Cu-S(1), Cu(1)-S(3), Cu(1)-S(2) is 2.3736(9) Å,
2.4301(8) Å, 2.7304(10) Å) and the Cu(1)-O(2) bond with the
nitrate ligand (2.335(3) Å).
Figure 3: X-ray crystal structure of 19 (Ellipsoids at 50% probability level.
Selected bond lengths and torsion angles are to be found in the ESI).
Examination the X-ray structure of the macrocycle-dye
conjugate 13 also reveals that while the central aryl and
pyridine rings are almost co-planar (C(9)-C(10)-C(12)-C(17) = -
8.3(3)°; C(11)-C(10)-C(12)-C(13)
=
-9.3(3)°) there is
Similarly, complexation of
6, 8 and 13 with either Hg2Cl4 or
considerable deviation from co-planarity about the central
aromatic ring and the azo moiety (C(16)-C(15)-N(2)-N(3) =
162.9(2)°; C(14)-C(15)-N(2)-N(3) = -18.6(3)°). The azo-link is E-
Hg2I4 in MeOH-CH2Cl2 afforded the crystalline complexes 21
,
22 and 23 whose solid state structures were also determined
by single crystal X-ray crystallography (Figures 5 and 6). All
three of these complexes were found to contain mercury in
two very different co-ordination environments. In the case of
configured (C(15)-N(2)-N(3)-C(18) = 178.35(16)°).
21,
22 and 23, one of the Hg2+ cations is bound, in an
endocyclic manner, to the three sulphur atoms and the
pyridine nitrogen atom of the macrocyclic core; these endo-
bound Hg2+ centres adopt highly distorted square pyramidal
co-ordination geometries in each case (τ 0.05, 0.31 and 0.37
respectively).13 The remaining apical co-ordination site is, in
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Br
DMSO
1
N
1
N
Br
N
S
S
2
DMSO
S
S
2
H2
O
3
1
S
N
3
1
S
AgNO3
S
6
S
2
AgNO3
S
8
H2,3
S
2
3
S
H1
H2,3
3
H1
S
H2O
15
H2,3
16
H2,3
NMR of 15
NMR OF 16
NMR OF 6
H1
DMSO
H2
3.5
O
H1
H2,3
H2,3
NMR of 8
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.0
2.5
Chemical Shift (ppm)
Chemical Shift (ppm)
H2
O
H3CO
DMSO
H3CO
N
N
N
N
AgNO3
1
N
S
1
2
H1
N
S
S
3
2
S
H2,3
S
3
13
H2,3
S
17
NMR OF 17
NMR OF 13
H1
H2,3
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
Chemical Shift (ppm)
Figure
4:
1H NMR spectra of the free ligands
6
,
8
and 13 together and their spectra when determined in the presence of Ag+ and TFA.
Complex 21 Complex 22
Figure 5: X-ray crystal structure of complexes 21 and 22 (Ellipsoids at 50% probability level. Selected bond lengths and torsion angles are to be found in the ESI).
These values are somewhat attenuated (Figure 6) upon configured azo-moiety (C(15)-N(2)-N(3)-C(18)
= 177.7(8)°),
complexation with Hg2I4 (C(14)-C(15)-N(2)-N(3) = 154.4(9)° and observations which are similar to those reported for related
C(16)-C(15)-N(2)- N(3) = -27.2(13)° while maintaining an E- push-pull azo-dyes and their complexes.3c Complexation of
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ARTICLE
Hg2+ by 13 also induces a conformational change in the 1,4,7- in the Hg2+ complex, 23, the torsion angles for S(3)-C(9)-C(10)-
10-azacyclodocane core. For example, in the free ligand, 13 N(1) becomes -21.8(11)° and that for N(1)-C(3)-C(4)-S(1)
the torsion angles about S(1)-C(3)-C(4)-N(1) and N(1)-C(5)-C(6)- becomes -15.0(11)° respectively, an outcome which is similar
,
S(3) are 118.67(17)° and -98.68(18)° respectively. These to that reported for the complex of
parameters change dramatically upon complexation such that
8
with HgCl2.5d
Figure 6: X-ray structure of complex 23 (Ellipsoids at 50% probability level. Selected bond lengths and torsion angles are to be found in the ESI).
The UV-visible spectra of 17, 20 and 23 in ethanol, which factors responsible for the absorption spectra of 13, 20 and 23.
appear yellow-orange in colour, all display small bathochromic All calculations were performed using the Gaussian suite of
shifts3i when reacted with 1 equivalent of a selection of metal programs.16
salts (1 mg/50 mL of ethanol) [Ag complex: ʎmax = 364 nm(ε = In the optimised (gas phase) structure of 13 we find that the
4.5 x 105), Cu complex ʎmax = 372 nm(ε = 4.3 x 105) and Hg- two rings joined by the diazo unit are strongly coplanar with
complex is ʎmax = 364 nm(ε = 5.3 x 105)] with respect to the dihedral angle, C(16)-C(15)-N(2)-N(3) = -179.2°, in contrast to
uncomplexed ligand 13 [ʎmax 358 nm (ε = 4.0 x 105)]. A small the crystal structure (162.9°). For the two rings on the same
bathochromic shift is also observed when the UV spectrum of side of the diazo unit we find the computed dihedral angles to
13 is conducted in the presence of TFA, generating be larger, e.g. C(9)-C(10)-C(12)-C(17) = -35.5°, compared with
trifluoroacetate salt 24 (1 mg of 13/50 mL of ethanol; 0.01 mL the crystal structure (-8.3°). Other key angles are compared in
of TFA; ʎmax 363 nm (ε = 4.4 x 105)), Figure 7
.
Table 2
.
The computed absorption bands of 13
,
20 and 23
0.9
corresponding to the bands shown in figure 7 are listed in
Table 3 with the associated oscillator strength and the weights
of the principal excitations involved. The B3LYP functional used
in this work is known to underestimate the transition energies
associated with charge transfer bands. However our concern
here is for a relative comparison of the nature of the bands
and for this analysis the B3LYP functional is adequate. We find
that in 13, the band shown is not dominated by a HOMO →
LUMO transition but rather the HOMO-1 → LUMO transiꢀon.
The band corresponding to the HOMO → LUMO transiꢀon is
found 31 nm lower in wavelength with a relatively small
oscillator strength (0.075 versus 1.232). The relevant orbitals
are depicted in Figure 8(a) and show that the transition
corresponds to transfer of charge from the terminal, electron
rich, ring attached to the azo unit towards the electron
deficient, macrocycle, end. The orbitals on the azo moiety
Dye(13)
Ag(17)
Cu(20)
TFA(24)
Hg(23)
0.6
0.3
0
220
320
420
520
WAVELENGTH (nm)
Figure 7: UV studies of dye 13 and its complexes 17, 20, 23 and salt 24 in ethanol
change from bonding to antibonding in this transition. In 23
,
solution (1 mg/ 50 mL of ethanol at 20 °C).
λmax does correspond to the HOMO → LUMO transiꢀon and
shows a stronger charge transfer from the terminal, electron
rich, ring towards the pyridine ring which is bond to the metal,
DFT Calculations
We have undertaken DFT studies at the B3LYP14/Def2-TZVP15a
level in order to gain information as to the structure and
bonding of these ligands and complexes and also to probe the
see Figure 8(b). For 20, a similar picture emerges (Figure 8(c)
but the effect is less marked than in 23
)
.
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resolution mass spectra were measured on Kratos Concept IS
spectrometer. A Carlo Erba EA 1108 Elemental Analyzer was
used for determination of % levels of carbon, hydrogen and
Angles/°
13
23
20
31.9
32.0
ꢀ175.4
4.8
C(9)ꢀC(10)ꢀC(12)ꢀC(17)
C(11)ꢀC(10)ꢀC(12)ꢀC(13)
C(16)ꢀC(15)ꢀN(2)ꢀN(3)
C(14)ꢀC(15)ꢀN(2)ꢀN(3)
N(2)ꢀN(3)ꢀC(18)
ꢀ35.5
ꢀ35.6
ꢀ179.2
0.9
28.8
29.5
179.4
ꢀ0.9
nitrogen.
A Metrohm 686 Titroprocessor +665 Dosimat
Autotitor was used to measure chlorine content.
116.0
116.3
116.3
Synthesis of 1,4-Dihydro-4-oxo-2,6-pyridinedicarboxylic acid,
1 17
.
Table 2. Key angles in computed structures (B3LYP/Def2ꢀTZVP).
The first part of this preparation involved the synthesis of 4-
oxo-4H-pyran-2,6-dicarboxylic acid (chelidonic acid)14b
:
a
Molecule
13
λmax / nm
Oscillator
Strength
1.232
Principal Transitions
Weights of
Transitions
0.395
0.096
0.370
solution of sodium ethoxide was prepared by dissolving
sodium (2.4 g, 0.1 mol) in 36 mL of anhydrous ethanol. To this
mixture was added a mixture of dry acetone (4 mL, 0.05 mmol)
and diethyl oxalate (14.5 g, 0.11 mol). During the addition of
two mixtures a yellow precipitate formed. The reaction was
stirred for an hour at 60 °C to complete the reaction, then 20
mL of 37% of HCl and 10 mL of water was added and it was left
to stir for one day at 50 °C. Excess ethanol was removed under
reduced pressure, and then 30 mL of water and 5 mL of HCl
was added and was left to stir at ambient temperature for a
further period of 3 – 4 days. The crude product which had
been deposited was collected by filtration at the pump,
washed (water and then ice-cold acetone) to afford 4-oxo-4H-
pyran-2,6-dicarboxylic acid (chelidonic acid) as a brown-
coloured, amorphous, solid. Yield 11.54 g (42%); mp 247 – 248
°C (lit17b: 157 °C). 1H NMR: (methanol-d4, 300 MHz) δ ppm 7.01
(2H, s, ArH). 13C NMR: (methanol-d4, 75 MHz) δ ppm 119.96,
156.97, 162.44, 182.84. ṽmax (ATR): 1229, 1583, 1633, 1742,
378
HOMOꢀ1 → LUMO
HOMOꢀ2 → LUMO
HOMO → LUMO+3
(HOMO)α → (LUMO)α
23
20
353
347
0.599
0.416
0.364
Table 3. λmax absorption bands, oscillator strength and the weights of the
principal excitations (B3LYP/Def2ꢀTZVP).
(a)
13, HOMO-1
23, HOMO
13, LUMO
2560, 3078 cm-1 MS (ES+): m/z [M+H]+ 185; [M+Na]+ 207.
(b)
23, LUMO+3
.
Accurate Mass (ES+): [C7H4O6]+ requires 184.0008 found
184.0021.
Aqueous ammonia (80 mL of a 35% aqueous solution) was
added drop-wise to chelidonic acid (7.91 g, 42.9 mmol) at 0 °C.
Upon completion of the addition the reaction mixture was
stirred for two days at room temperature. Excess ammonia
was removed under reduced pressure and the solid was
brought to reflux with 80 mL of water and 1.6 g of charcoal for
5 minutes. The mixture was filtered through celite® and the
filtrate allowed to cool to ambient temperature. The filtrate
was then acidified to pH 1 by the careful addition of 37 %
aqueous HCl which resulted in the precipitation of the crude
product, a colourless crystalline solid. The title compound was
collected at the pump and washed with ice-cold water (3 x 30
mL) and dried in vacuo. Yield 5.53 g (70%); mp 254 - 255 °C,
lit.17: 248 °C). 1H NMR: (methanol-d4, 300 MHz) δ ppm 6.95
(2H, s, ArH). 13C NMR: (methanol-d4, 75 MHz) δ ppm 117.3,
145.3, 165.9, 184.4. ṽmax (ATR): 1336, 1392, 1460, 1609, 1710,
2498, 3120, 3446, 3605 cm-. MS (ES+): m/z [M+H]+ 183;
[M+Na]+ 205. Accurate Mass (ES+): [C7H6NO5]+ requires
184.0246; found 184.0241.
(c)
20, (HOMO)α
20, (LUMO+2)α
Figure 8. MO orbitals associated with λmax for 13, 20 and 23.
Experimental
General Experimental details
Synthetic procedures were carried out under an atmosphere
of nitrogen in dry solvents unless stated otherwise. All
reagents and solvents were reagent grade and were used
without further purification. Chromatographic purifications
were performed using silica gel SDS (particle size 0.04-0.06
mm). A Sanyo Gallenkamp melting point apparatus was used
for melting point determinations; these values are
uncorrected. Infrared spectra were measured using a Bruker
Alpha ATR FT-IR instument as evaporated films; absorption
peaks (ṽmax) are quoted in wave numbers (cm-1). Deuterated
chloroform (CDCl3) was used as solvent unless otherwise
stated to record Nuclear magnetic resonance (NMR) spectra.
1H NMR spectra were recorded on Bruker Advance Ultra shield
300 (300 MHz), Bruker Advance Ultrashield 500 (500 MHz).
Signal splitting patterns are described as singlet (s), doublet
(d), triplet (t), multiplet (m). Low resolution mass spectra were
measured on Micromass Trio 200 spectrometer. High
Synthesis of dimethyl 4-oxo-2,6-1,4-dihydropyridine-2,6-
dicarboxylate, 2.18
Thionyl chloride (22.3 mL, 306 mmol, 8 eq) was added
dropwise to methanol (70 mL) which was cooled to -10 °C.
Chelidamic acid (7 g, 38.2 mmol) was also added to the
mixture. The solution was left to stir for 24 hours at room
temperature and then heated at reflux for an additional 2
hours. The excess of thionyl chloride and the solvent was
6 | J. Name., 2012, 00, 1-3
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removed under reduce pressure to give the title compound as To a stirred solution of 4-bromo-2,6-bis(bromomethyl)pyridine
a colourless, crystalline solid. Yield 7.85 g (97%); mp 162 - 165 (0.791 g, 2.11 mmol), in toluene (25 mL) was added 2,2-
5
°C (lit.18: 169 – 170 °C). 1H NMR: (methanol-d4, 300 MHz) δ thiodiethanethiol (0.28 mL, 2.11 mmol), and a solution of KOH
ppm 3.99 (6H, s, CH3), 7.78 (2H, s, ArH). 13C NMR: (methanol- (0.24 g, 4.22 mmol) in ethanol/H2O 50:1 (25 mL). The bi-phasic
d4, 300 MHz) δ ppm 54.8, 117.7, 145.6, 161.6, 174.7. ṽmax reaction mixture was stirred at room temperature for 24 hours
(ATR): 1187, 1348, 1478, 1558, 1724, 3106 , 3307 cm-1. MS after which time the solvent was removed in vacuo. The
(ES+): m/z [M+H]+ 212; [M+Na]+ 234. Accurate Mass (ES+): residue was triturated with DCM (50 mL) and the organic
[C9H10NO5]+ requires 212.0552; found 212.0554.
Synthesis of dimethyl 4-bromopyridine-2,6-dicarboxylate, 3.19 in vacuo. Purification of the residue by column
mixture of dimethyl 4-oxo-2,6-1,4-dihydropyridine-2,6- chromatography (silica; DCM:Pet 1:1) afforded the title
dicarboxylate, (6.6 g, 31.4 mmol) and PBr5 (27.04 g, 62.8 compound as a crystalline solid. Yield 0.341 g (48%), mp 122-
extracts washed (6 x 30 mL), dried (MgSO4) and concentrated
A
2
1
mmol) were heated together at 90 °C for 3 hours. After this 123 °C. H NMR: (CDCl3, 400 MHz) δ/ppm 2.52 (8H, s, H), 3.79
time the reaction mixture was allowed to cool down to room (4H, s,), 7.49 (2H, s,) 13C NMR: (CDCl3, 100 MHz) δ ppm 30.1,
temperature and quenched by the careful addition of hot 31.0, 35.4, 125.7, 134.6, 158.7. ṽmax (ATR): 1187, 1348, 1478,
methanol (15 mL) which resulted in the precipitation of the 1558, 1724, 3106, 3307 cm-1 MS (ES+): m/z [M+H]+ 336
.
title compound. Collection of the precipitate at the pump and Accurate Mass (ES+): [C11H1479BrNS3]+ requires 335.9547;
drying in vacuo afforded the product, essentially pure by 1H found 335.9545. Microanalysis: C11H14BrNS3 requires: C, 39.28;
NMR, as a pale beige-coloured amorphous solid. Yield 7.62 g H, 4.2; N, 4.16 %; found: C, 39.16; H, 4.17; N, 3.82 %.
(88%); mp 153 - 156 °C; (lit19 155 – 156 °C). 1H NMR: Synthesis of 3,6,9-trithia-1(2,6)-pyridinacyclodecaphane, 8.5a
(methanol-d4, 300 MHz) δ/ppm 4.06 (6H, s, CH3), 8.49 (2H, s, To a stirred solution of 2,6-bis(bromomethyl)pyridine,
7 (0.56
ArH). 13C NMR: (methanol-d4, 75 MHz) δ/ppm 53.4, 131.3, g, 2.11 mmol) in toluene (25 mL) was added 2,2-
135.1, 149.1, 164.0. ṽmax (ATR): 1146, 1246, 1263, 1326, 1442, thiodiethanethiol (0.28 mL, 2.11 mmol), and KOH (0.24 g, 4.22
1714, 2951, 3077 cm-1. MS (ES+): m/z [M+H]+ 273.97. Accurate mmol) dissolved in ethanol/H2O 50:1 (25 mL). The bi-phasic
Mass: [C9H9N1O480Br1] requires; 273.9709; found 273.9708. reaction mixture was then stirred vigorously at room
Microanalysis: C9H8BrNO4 requires: C, 39.44; H, 2.94; N, 5.11; temperature for 24 hours. The solvent was then removed in
Br, 29.15 found: C, 39.07; H, 3.09; N, 5.12; Br, 29.07 %.
Synthesis of 4-bromo-2,6-pyridinedimethanol, 4.20
vacuo and the residue dissolved in DCM (100 mL). The organic
extracts were washed with water (6 x 50 mL), dried (MgSO4)
Bromo ester
4 (5.0 g, 18.2 mmol) was dissolved in anhydrous and concentrated in vacuo. The resulting residue was purified
EtOH (130 mL) and the mixture cooled to 0 °C. To this by column chromatography (silica; DCM:Pet; 1:1) affording the
suspension was added NaBH4 (3.33 g, 88 mmol) and the title compound as a colourless, crystalline solid. Yield 0.39 g
mixture stirred at 0 °C for one hour, at room temperature for (72%); mp 164-165 °C (lit.5a: 162-163 °C) of pure compound. 1H
another hour and at reflux temperature for 1 day. On cooling NMR (400 MHz, DMSO-d6) δ ppm 2.50 (s, 8H) 3.85 (s, 4H) 7.38
to ambient temperature acetone (85 mL) was added and the (d, J = 8 Hz, 2H) 7.84 (t, J = 7.5 Hz, 1H). 13C NMR (125 MHz,
mixture brought to reflux for one hour. The solvent was DMSO-d6) δ ppm 29.6, 30.5, 35.3, 122.5, 138.8, 157.5. ṽmax
removed in vacuo and the waxy residue was recrystallized (ATR): 2921, 1588, 1569, 1451, 1428, 1280, 1208, 1154 cm-1.
from water to afford the title compound as an amorphous, MS (ES+): m/z [M+H]+ 258.2 Accurate Mass (ES+): [C11H15NS3]+
colourless, solid. Yield 2.95 g (74%); mp 152 - 156 °C (lit.20: 158 requires: 257.0361; found: 257.0362.
1
– 160 °C). H NMR: (DMSO-d6, 500 MHz) δ ppm 4.53 (4H, s, Synthesis
of
dimethyl
4-(4,4,5,5-tetramethyl-1,3,2-
CH2), 7.52 (2H, s, ArH). 13C NMR: (methanol-d4, 75 MHz) δ ppm dioxaborolan-2-yl)pyridine-2,6-dicarboxylate, 10.22
63.61 (C4), 121.04 (C2), 133.20 (C1), 163.19 (C3). ṽmax (ATR): Compound 10 was prepared using an adaption of the
1305, 1361, 1403, 1566, 1566, 2763, 3093, 3344 cm-1. procedure reported by Maury et al.22 A mixture of dimethyl 4-
Microanalysis: C7H8BrNO2 requires: C, 38.56; H, 3.7; N, 6.42 %; bromopyridine-2,6-dicarboxylate,
3 (1.43 g, 5.25 mmol),
found: C, 38.39; H, 3.86; N, 6.13 %.
Synthesis of 4-bromo-2,6-bis(bromomethyl)pyridine, 5.21
bis(pinacolato)diboron (2.0 g, 8.0 mmol), Pd(dppf)Cl2 (0.08 g,
0.11 mmol) and dry potassium acetate (1.6 g, 16.0 mmol) in
Diol
4 (2.8 g, 13.1 mmol) and 33% HBr in acetic acid (50 mL) anhydrous 1,4-dioxane (25 mL) was heated at 80 °C for 24
were heated at 125 °C for 5 hours. The reaction mixture was hours. After cooling to room temperature, the reaction
then poured onto ice the pH adjusted to pH 4 – 5 by the mixture was poured into water and then extracted with DCM.
addition of 1 M NaOH. At this stage the title compound The organic layer was dried (MgSO4) and concentrated in
precipitated out of solution as a white powder which was vacuo. Purification of the residue by column chromatography
collected at the pump. Yield 3.9 g (89%); mp 127-129 °C (lit.21: (silica; hexane:DCM; 2:1) afforded the title compound as
1
125-126 °C). H NMR: (400 MHz, DMSO-d6) δ ppm 4.66 (4H, s, brown-coloured solid. Yield 1.4 g (87%), mp 116-117 ˚C. 1H
CH2) 7.81 (2 H, s, Ar-H). 13C NMR (125 MHz, DMSO-d6) δ ppm NMR (400 MHz, CDCl3) δ ppm 1.37 (12H, s), 4.02 (6H, s), 8.63
33.5, 125, 133.4, 158.6. ṽmax (ATR): 2971, 1563, 1452, 1355, (2H, s). 13C NMR (125 MHz, CDCl3) δ ppm 24.9, 53.1, 83.4, 85.1,
1283 cm-1. MS (ES+): m/z [M+H]+ 341.8; Accurate Mass: 133.1, 147.5, 165.1. ṽmax (ATR): 2975, 1710, 1436, 1401, 1339,
[C7H7N79Br3]+ requires: 341.8128; found: 341.8129.
1280 cm-1. MS (ES+): m/z [M + H]+ 322.
Synthesis of 13-bromo-3,6,9-trithia-15- Synthesis
of
(E)-1-(4-methoxyphenyl)-2-(4-(4,4,5,5-
azabicyclo[9.3.1]pentadeca-1(15),11,13-triene, 6.
tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)diazene, 12.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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Journal Name
A
mixture
of
(E)-1-(4-iodophenyl)-2-(4- J = 8.8, 2.2 Hz), 7.92 (2H, dd, J = 8.0, 1.7 Hz), 7.98 (2H, dd, J =
methoxyphenyl)diazene,23 11 (1.45 g, 5.25 mmol), 8.8, 2.5 Hz), 8.05 (2H, dd, J = 8.0, 1.5 Hz), 8.62 (2H, s). 13C NMR
bis(pinacolato)diboron (2.0 g, 8.0 mmol), Pd(dppf)Cl2 (0.08 g, (125 MHz, CDCl3) δ ppm 53.3, 55.6, 114.3, 123.5, 125.1, 125.6,
0.11 mmol) and dry potassium acetate (1.6 g, 16.0 mmol) in 127.9, 137.5, 147.0, 148.9, 150.3, 150.6, 162.6, 165.2. ṽmax
anhydrous 1,4-dioxane (25 mL) was heated at 80 °C for 24 (ATR): 2959, 1499, 1412, 1349, 1313, 1294, 1195 cm-1. MS (ES-
hours. After cooling to room temperature, the reaction ): m/z [M+H]+ 406.2. Accurate Mass: C22H20N3O5 requires
mixture was poured into water and then extracted with DCM 406.1411; found 406.1416.
(2 x 50 mL). The combined organic extracts were dried Metal complexation studies:
(MgSO4) and concentrated in vacuo affording the title Synthesis of silver(I) complex (15).5a,24
compound as dark red-coloured solid which was essentially A solution of silver nitrate (0.02 g, 0.1 mmol) in methanol (8
pure by 1H NMR analysis. Yield 1.6 g (94%); mp 154-155 ˚C. 1H mL) was added slowly, over a period of 20-25 minutes at room
NMR (400 MHz, CDCl3) δ ppm 1.29 (12H, s), 3.80 (3H, s), 6.93 temperature, to
a
solution of 3,6,9-trithia-1(2,6)-
(0.03 g, 0.1 mmol) in DCM (8 mL).
(2H, d, J = 9.5 Hz), 7.78 (2H, d, J = 9.0 Hz), 7.83 - 7.88 (4H, m). pyridinacyclodecaphane,
8
13C NMR (125 MHz, CDCl3) δ ppm 24.5, 55.2, 83.1, 83.6, 113.8, Slow evaporation of the reaction mixture at ambient
121.4, 124.5 (C3), 135.3, 146.7, 154.1, 161.9. ṽmax (ATR): 2993, temperature afforded the title compound as a colourless
1499, 1438, 1353, 1306, 1274, 1209, 1170 cm-1. MS (ES+): m/z powder. Yield 0.038 g (89%), mp 219-220 °C (lit.5a: 217-219 °C).
[M+H]+ 339.4. Accurate Mass: C19H23N2O3B requires 338.1790; 1H NMR (400 MHz, DMSO-d6) δ ppm 2.74 (4H, d, J = 4 Hz), 3.16
found 338.1795.
Synthesis of (E)-1-(4-((4-methoxyphenyl)diazenyl)phenyl)- 7.87 (1H, td, J = 8, 3.5 Hz). 13C NMR
3,6,9-trithia-1(2,6)-pyridinacyclodecaphane, 13. ppm 30.1, 31.3, 37.2, 124.4, 138.7, 156.1. ṽmax (ATR): 3055,
To
solution of (E)-1-(4-methoxyphenyl)-2-(4-(4,4,5,5- 2949, 1471, 1386, 1359, 1343 cm-1. MS (ES+): m/z [M+H]+
(4H, br. s.) 4.16 (4H, d, J = 3.0 Hz), 7.42 (2H, dd, J = 8, 3 Hz),
(125 MHz, DMSO-d6) δ
a
tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)diazene, 12 (0.603 428.4.
g, 1.8 mmol), Pd(PPh3)4 (205 mg, 0.18 mmol) in DMF (30 mL) Synthesis of silver(I) complex, 16.
was added Cs2CO3 (405 mg, 5.4 mmol) and 13-bromo-3,6,9- A solution of silver nitrate (0.008 g, 0.05 mmol) in methanol (4
trithia-15-azabicyclo[9.3.1]pentadeca-1(15),11,13-triene,
(0.608 g, 1.8 mmol). The reaction mixture was heated at 110 °C temperature, to
for 24 hours. After this time the reaction mixture was azabicyclo[9.3.1]pentadeca-1(15),11,13-triene,
6
mL) was added slowly, over a period of 20-25 minutes at room
solution of 13-bromo-3,6,9-trithia-15-
(0.017 g, 0.05
a
6
concentrated in vacuo and the residue triturated with ethyl mmol) in DCM (4 mL). Slow evaporation of the solution the
acetate (50 mL). The organic extract was washed (with brine title compound as a colourless powder. Yield 0.025 g (93%),
and then water), dried (MgSO4) and concentrated in vacuo. mp 211-213 °
C). 1H NMR (400 MHz, DMSO-d6) δ ppm 2.50 -
The residue was purified by column chromatography (silica; 2.51 (4H, m), 2.75-2.77 (4H, m), 4.17 (4H, s), 7.74 (2H s). 13C
hexane:DCM, 2:1) to afford the title compound as an orange- NMR (125 MHz, DMSO-d6) δ ppm 29.9, 31.0, 36.3, 126.8,
coloured, crystalline, solid. Yield 0.62 g (74%), mp 133-134 ˚C. 133.5, 157.5. ṽmax (ATR): 3043, 2960, 1560, 1481, 1356, 1319,
1H NMR (400 MHz, CD2Cl2)
δ
ppm 2.61 (8H, s), 3.91 (3H, s), 1303 cm-1. MS (ES-): m/z [M+H]- 504.8. Accurate Mass
3.94 (4H, s), 7.05 (2H, d, J = 8.8 Hz), 7.67 (2H, s), 7.86 (2H, d, J = [C11H14N2Ag1S3BrO3]- requires 503.8401 found 503.8400.
8.8 Hz), 7.96 (2 H, d, J = 9.0 Hz, Ar-H7), 8.01 (2 H, d, J = 9.0 Hz, Microanalysis: C11H14BrAgN2O3S3 requires: C, 26.0.; H, 2.7; N,
Ar-H6). 13C NMR (125 MHz, CD2Cl2) δ ppm 31.1, 31.8, 32.5, 5.5%; found: C, 25.8; H, 2.6; N, 5.6%.
55.7, 114.7, 123.6, 124.1, 125.6, 129.3, 135.3, 147.2, 154.5, Synthesis of silver(I) complex, 17.
155.2, 158.3, 163.1. ṽmax (ATR): 2962, 1581, 1453, 1420, 1393, A solution of silver nitrate (0.008 g, 0.05 mmol) in methanol (4
1248, 1193 cm-1 MS (ES-): m/z [M-H]– 466.7; [M + H]+ 468.2. mL) was added slowly, over a period of 20-25 minutes at room
.
Accurate Mass: C24H26N3O1S3 requires 468.1233 found temperature
to
methoxyphenyl)diazenyl)phenyl)-3,6,9-trithia-1(2,6)-
(E)-4-(4-((4- pyridinacyclodecaphane, 13 (0.023 g, 0.05 mmol) in DCM (4
mL). Slow evaporation of the solution afforded the title
14. To a solution of (E)-1-(4-methoxyphenyl)-2-(4-(4,4,5,5- complex as a red-coloured solid. Yield 0.098 g (90%), mp 260-
tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)diazene, 12 (0.603 263
C. 1H NMR (400 MHz, DMSO-d6) δ ppm 2.50-2.54 (4H, m),
a
solution
of
(E)-1-(4-((4-
468.1230.
Synthesis
of
dimethyl
methoxyphenyl)diazenyl)phenyl)pyridine-2,6-dicarboxylate
°
g, 1.8 mmol), Pd(PPh3)4 (205 mg, 0.18 mmol) in DMF (30 mL) 2.74 - 2.83 (4H, m), 3.87 (3H, s), 4.23 (4H, br. s.), 7.16 (2H, d, J
was added Cs2CO3 (405 mg, 5.4 mmol) and dimethyl 4- = 9 Hz), 7.91 (2H, s), 7.94 (2H, d, J = 8.8 Hz), 8.01 (2H, d, J = 9
bromopyridine-2,6-dicarboxylate,
3
(0.491 g, 1.8 mmol). The Hz), 8.08 (2H, d, J = 8.8 Hz). 13C NMR (125 MHz, DMSO-d6) δ
reaction mixture was heated at 110 °C for 24 hours. After this ppm 30.1, 31.2, 37.4, 55.8, 114.8, 121.8, 123.1, 125.0, 128.3,
the reaction mixture was reduced in vacuo and the residue 128.8, 131.5, 132.2, 137.8, 148.1, 156.9. ṽmax (ATR): 2974,
triturated with ethyl acetate. The organic extracts were 2928, 1597, 1549, 1445, 1378, 1308, 1254 cm-1. MS (ES+): [M]+
washed (brine and then water), dried (MgSO4) and reduced in 576.5.
vacuo. The residue was purified by column chromatography Synthesis of Cu(II) complex, 18.
(silica; hexane:DCM, 2:1) affording the title compound as A solution of copper nitrate pentahydrate (0.012 g, 0.05 mmol)
orange powder. Yield 0.54 g (74%), mp 141-142 ˚C. 1H NMR in methanol (4 mL) was added slowly, over a period of 20-25
(400 MHz, CDCl3) δ ppm 3.92 (3H, s), 4.08 (6H, s), 7.05 (2H, dd, minutes at room temperature, to a solution of 3,6,9-trithia-
8 | J. Name., 2012, 00, 1-3
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ARTICLE
1(2,6)-pyridinacyclodecaphane,
8 (0.013 g, 0.05 mmol) in DCM dissolved in DCM (4 mL) and mercury iodide (0.023 g, 0.05
(4 mL). Slow evaporation of the solution afforded the title mmol) was dissolved in methanol (4 mL) and this solution was
complex, as a dark green-coloured crystalline solid. Yield 0.021 added slowly over a period of 20-25 min at room temperature.
g (91%), mp 225-226 °C. ṽmax (ATR): 3028, 2995, 1434, 1418, Slow evaporation of the solvent afforded the title complex as a
1353, 1262 cm-1. MS (ES+): [M]+ 443.91. Microanalysis: yellow-coloured crystalline solid. Yield 0.065 g (95%), mp 226-
C11H17CuN3O7S3 requires: C, 28.5.; H, 3.7; N, 9.0, S 20.3 %; 228 °C. 1H NMR (400 MHz, CDCl3) δ ppm 2.61 - 2.68 (8H, m, Ar-
found: C, 28.7; H, 3.8; N, 9.0, S, 20.1%.
H13,14) 3.92 (3H, s, OCH3) 3.97 (4H, s), 7.05 (2H, dd, J=8.8, 2.2
Hz), 7.67 (2H, s), 7.98 (2H, dd, J = 8.8, 2.5 Hz), 8.01 (2 H, d, J =
Synthesis of Cu(II) complex, 19.
A solution of copper nitrate pentahydrate (0.012 g, 0.05 mmol) 8.8 Hz), 8.05 (2H, d, J = 8.8 Hz). 13C NMR (125 MHz, CDCl3) δ
in methanol (4 mL) was added slowly, over a period of 20-25 ppm 30.1, 31.1, 36.7, 55.6, 114.3, 120.0, 123.3, 125.0, 127.8,
minutes at room temperature to a solution of 13-Bromo-3,6,9- 133.1, 153.1, 162.4. ṽmax(ATR): 2945, 2914, 1596, 1578, 1481,
trithia-15-azabicyclo[9.3.1]pentadeca-1(15),11,13-triene
1367, 1317, 1248 cm-1. MS (ES+): [M]+ 669.9.
(0.017 g, 0.05 mmol) in DCM (4 mL). Slow evaporation of the Blank experiment with TFA (In situ Formation of
solution afforded the title compound as a dark-green coloured trifluoroacetate salt, 24. To a solution of 13 (20 mg) in CD2Cl2
1
crystalline solid. Yield 0.025 g (92%), mp 252-254 °C. ṽmax (ATR): (1 mL) was added 1 drop of TFA at ambient temperature. H
2977, 2951, 2932, 2163, 1585, 1286, 1228 cm-1. MS (ES+): NMR (400 MHz, CD2Cl2) δ ppm 2.56 - 2.62 (4H, m), 2.72 - 2.78
[M+H]+ 522.8. Microanalysis: C11H14BrCuN3O7S3.2H2O requires: (4H, m, Ar-H), 3.92 (3H, s), 4.30 (4H, s), 7.08 (2H, dd, J = 8.32,
C, 23.6; H, 3.2; Br, 14.3; N, 7.50%; found: C, 23.7; H, 3.4; N, Br 2.0 Hz,), 7.97 - 8.01 (4H, m), 8.10 (2H, dd, J = 8.3, 1.7), 8.14
14.1; N, 7.3%.
(2H, s). 13C NMR (125 MHz, CD2Cl2) δ ppm 31.7, 32.4, 33.1,
56.6, 115.3, 124.1, 124.6, 126.2, 129.8, 135.8, 147.8, 155.0,
Synthesis of Cu(II) complex, 20.
A solution of copper pentahydrate (0.012 g, 0.05 mmol) was in 155.7, 158.4, 164.0.
methanol (4 mL) was added slowly, over a period of 20-25
minutes at room temperature, to a solution of (E)-1-(4-((4-
Conclusions
methoxyphenyl)diazenyl)phenyl)-3,6,9-trithia-1(2,6)-
pyridinacyclodecaphane, 13 (0.023 g, 0.05 mmol) in DCM (4
mL) and copper nitrate (0.012 g, 0.05 mmol) was dissolved in
methanol (4 mL). Slow evaporation of the solvent afforded the
title complex as red-coloured powder. Yield 0.028 g (96%), mp
284-287 °C. ṽmax (ATR): 2960, 2926, 1598, 1583, 1498, 1397,
1280, 1247 cm-1. MS (ES+): [M]+ 530.1.
In summary, we have synthesised and fully characterised a
new azo dye-macrocycle conjugate, 13, which incorporates an
“S3N” macrocycle as a metal binding site. Complexation of 6, 8
and 13 to Ag(I), Hg(II) and Cu(II) affords well defined
complexes of which have been fully characterised.
Complexation of transition metals to ligand 13 results in a
small bathochromic shift its UV spectrum, which is most
pronounced in the case of Cu(II) (ꢀλ = 14 nm): similar
bathochromic shifts have been reported upon complexation of
Synthesis of Hg(II) complex. 21.5a,5d 3,6,9-Trithia-1(2,6)-
pyridinacyclodecaphane (0.013 g, 0.05 mmol) was dissolved in
DCM (4 mL) and HgCl2 (0.025 g, 0.05 mmol) was dissolved in
methanol (4 mL) and this solution was added slowly over a
period of 20-25 min at room temperature. Slow evaporation of
the solution afforded the title complex as a colourless,
crystalline solid. Yield 0.038 g (95%), mp 221-223 °C (Lit.19:
quinolone-functionaliszed azo dyes.3i
In contrast, DFT
calculations indicate that ligation of metals by the ligand 13
should result in a hypsochromic shift in λmax in the UV-visible
spectrum, and that such changes are metal-dependent.
Studies are now underway in order to define second
generation systems which incorporate other, more responsive,
reporter functionality for biomedical studies.25
1
199-201°C). H NMR (400 MHz, CD2Cl2) δ ppm 2.44 - 2.58 (8H,
m), 3.85 (4H, s), 7.37 (2H, d, J = 7.5 Hz), 7.75 (1H, t, J = 7.6 Hz).
13C NMR (125 MHz, CD2Cl2) δ ppm 30.5, 31.5, 36.7, 122.7,
139.2, 158.1. ṽmax (ATR): 3105, 2989, 1461, 1383, 1371, 1339
cm-1.
Synthesis of Hg(II) complex, 22.
Acknowledgements
Mercury(II) iodide (0.023 g, 0.05 mmol) was dissolved in
methanol (4 mL) and this solution was added slowly, over a
period of 20-25 minutes at room temperature, to a solution of
13-bromo-3,6,9-trithia-15-azabicyclo[9.3.1]pentadeca-
The UoM thanks the Engineering and Physical Sciences Research
Council (grant number EP/K039547/1) for the provision of Bruker
NMR spectrometers and an Agilent SuperNova X-ray
diffractometer. O. K. R. thanks the University of Manchester for
support. We thank Mr. Iman Rajabi for preliminary experiments.
1(15),11,13-triene,
6 (0.017 g, 0.05 mmol) in DCM (4 mL). Slow
evaporation of the solvent afforded the title compound as a
colourless crystalline solid. Yield 0.058 g (84%), mp 216-218 °C.
1H NMR (400 MHz, CD2Cl2) δ ppm 2.54 (8H, br. s), 3.81 (4H, s),
7.54 (2H, s). 13C NMR (125 MHz, CD2Cl2) δ ppm 30.5, 31.5, 36.3,
125.9, 135.4, 159.7. ṽmax (ATR): 3038, 2887, 1564, 1555, 1394,
1376, 1250 cm-1. MS (ES+): [M]+ 536.9.
Notes and references
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(E)-1-(4-((4-methoxyphenyl)diazenyl)phenyl)-3,6,9-trithia-
1(2,6)-pyridinacyclodecaphane (0.023 g, 0.05 mmol) was
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