First X-ray structural characterisation of host-guest interactions in tetra-tetrazole macrocycles

Article abstract of DOI:10.1016/j.tet.2009.07.063

The syntheses of tetra-tetrazole macrocycles, containing two 1,3-bis(tetrazole)benzene units linked by a variety of n-alkyl (n=3, 5, 7 or 9 carbon atoms) chain lengths, are described. The crystal structures of two 1,3-bis(tetrazole)benzenes containing pen

Full text of DOI:10.1016/j.tet.2009.07.063

Tetrahedron 65 (2009) 7942–7947
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
First X-ray structural characterisation of host–guest interactions in tetra-tetrazole
macrocycles
,
d
Andrew D. Bond a, Adrienne Fleming b, Jackie Gaire b, Fintan Kelleher b, John McGinley c , Vickie McKee
*
a Department of Physics and Chemistry, University of Southern Denmark, DK-5230 Odense M, Denmark
b Molecular Design & Synthesis Group, Department of Science, Institute of Technology Tallaght, Dublin 24, Ireland
c Department of Chemistry, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
d Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The syntheses of tetra-tetrazole macrocycles, containing two 1,3-bis(tetrazole)benzene units linked by
a variety of n-alkyl (n¼3, 5, 7 or 9 carbon atoms) chain lengths, are described. The crystal structures of
two 1,3-bis(tetrazole)benzenes containing pendant bromoalkyl chains (n¼3 or 5) are reported. A tetra-
tetrazole macrocycle has also been structurally characterised and contains an unexpected ‘host–guest’
interaction through binding of a chloroform solvent molecule. The resulting deviation of the macrocycle
from planarity results from a combination of the ‘host–guest’ interaction and strong intermolecular
interactions between adjacent tetrazole and phenylene rings.
Received 20 April 2009
Received in revised form 23 June 2009
Accepted 23 July 2009
Available online 29 July 2009
Keywords:
Tetrazole
Macrocycles
Host–guest
Synthesis
Ó 2009 Elsevier Ltd. All rights reserved.
X-ray crystal structure
NMR
1. Introduction
find application, for example, as sensors or in molecular recogni-
tion. We have previously reported the addition of pendant short-
Macrocyclic and macroacyclic compounds have attracted much
attention over the past number of years due to their role in un-
derstanding molecular processes that occur, for example, in bio-
chemistry, catalysis and material science. The reviews by Vigato
et al. describe the recent publications relating to these com-
pounds.1–3 The basis for the design of dinucleating or poly-
nucleating ligands is the ability of ligands to bind different metal
ions. Numerous macrocyclic systems exist, which contain nitrogen
donor atoms, either as a pyridine, imidazole or pyrrole group, or as
an amine group.1–8 However, it is somewhat surprising the relative
paucity of macrocycles containing tetrazole groups,9 considering
that there are many articles and reviews on tetrazoles in the liter-
ature, including their use as the carboxylic acid bioisosteres in drug
discovery.10–12 The development of ‘click’ chemistry methodology,
as described by Sharpless et al.,13,14 has resulted in a recent increase
in tetrazole structures, which suggests that molecular recognition
studies of tetrazoles will become increasing important.15–21 Our
interest in tetrazoles concerns their use as precursors for the for-
mation of new functionalised polytetrazole macrocycles, which can
chain alkyl halides and vinyl arms to various bistetrazoles, as well
as the synthesis and structural characterisation of tetra-tetrazole
macrocycles from 1,2-, 1,3- and 1,4-dicyanobenzene derivatives,
using short four-carbon, medium six-carbon and long eight-carbon
alkyl linkers.22–25 This paper focuses on the synthesis and charac-
terisation of bistetrazoles, from 1,3-dicyanobenzene, having pen-
dant n-alkyl halide arms (where n¼3, 5, 7 or 9), and their resulting
tetra-tetrazole macrocycles (Scheme 1). The X-ray crystal struc-
tures of the 1,3-benzene derivatives with 3- and 5-carbon chain
linkers are described, as is the first example of a host–guest in-
teraction between a tetra-tetrazole macrocycle and a solvent
molecule.
2. Results and discussion
The reactions of 1,3-bis[tetrazol-5-yl]benzene (1) with tri-
ethylamine and 1,n-dibromoalkanes (n¼3, 5, 7 or 9) were carried out
in a manner similar to that previously reported.24 An excess of the
dibromoalkane and base was used in order to eliminate any mono-
alkyl halide by-products, which may have been formed. The sym-
metric 2-N,2-N0-bistetrazole was the major product in all cases. The
other products in the reactions were not isolated due to the small
* Corresponding author. Tel.: þ353 1 708 4615; fax: þ353 1 708 3815.
E-mail address: john.mcginley@nuim.ie (J. McGinley).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.063

A.D. Bond et al. / Tetrahedron 65 (2009) 7942–7947
7943
base. The tetra-tetrazole molecule synthesised from 1,3-[bis(2-(6-
bromohexyl)tetrazol-5-yl]benzene and 1,3-bis(tetrazol-5-yl)ben-
zene (1) resulted in a macrocycle containing an internal cavity size
of 10.8ꢀ9.4 Å. We have now reacted 1,3-[bis(2-(n-bromoalkyl)-
tetrazol-5-yl]benzene (n¼3, 5, 7 and 9) and 1,3-bis(tetrazol-
5-yl)benzene in a similar manner. The yields for the cyclisation
reactions were in the range 18–50%, with the highest yield
obtained for the macrocycle containing the short n-propyl chain.
As the chain length increased, the resulting yield decreased, as
expected, since the entropy of activation is responsible for the
difficulty in closing rings larger than six-membered.31 The cycli-
sation reaction, in all cases, formed predominantly the symmetric
product, where the alkyl chains are joined to the tetrazole moieties
at the 2-N position, with very little asymmetry being observed. In
the 1H NMR spectra of all the cyclisation products, the signal for the
CH2Br at w3.5 ppm disappeared, and the accompanying loss of the
CH2Br signal in the 13C NMR spectra confirmed that cyclisation had
occurred. The simplicity of all the spectra indicated in all cases that
only a symmetric cyclisation product was obtained, as additional
signals would have been expected if any asymmetric product had
been formed.
N
(i)
N
N
N
HN
N
N
N
N
N
N
N
H
1
N
N
N
N
2, n = 3
3, n = 5
4, n = 7
5, n = 9
n
n
Br
Br
N
N
N
(ii)
N
N
N
N
N
N
N
N
n
N
n
N
N
N
N
6, n = 3
7, n = 5
8, n = 7
9, n = 9
Scheme 1. Reaction conditions: i) 1,n-dibromoalkane (n¼3, 5, 7 or 9), triethylamine,
methanol,
, 24 h; ii) 1, potassium carbonate, dimethylformamide, 75ꢂ, 24 h.
D
2.1. X-ray crystal structures
quantities involved. The 1H and 13C NMR spectra of the unpurified
reaction materials showed that the symmetric 2-N,2-N0-biste-
trazole predominated over the asymmetric 1-N,2-N0-bistetrazole in
an 85:15 ratio. The mass balance of the reaction was the starting
bistetrazole (1), which accounted for approximately 60% in all
cases. Two trends were observed for all the 1,3-bistetrazoles with
pendant alkyl halide arms, namely an increase in Rf value as the
chain length increased and a decrease in melting point as the chain
length increased (see Fig. 1). We have noticed this decrease in
melting point for the bistetrazole compounds containing even
chain length pendant alkyl halide arms (ethyl–octyl), although the
even cases are slightly higher.26,27
Crystals of compounds 2 and 3, suitable for an X-ray diffraction
study, were obtained from chloroform solution and the structures
confirmed the presence of the pendant bromoalkyl groups at the
2-N,2-N0-positions for 2 and 3 (Figs. 2 and 3). We have previously
published the crystal structure of 1,3-bis[(2-bromoethyl)tetrazol-
5-yl]benzene (10),24 and a second polymorph of that compound
has also been published (denoted 10a).32
Figure 2. Molecular structure of 2 with displacement ellipsoids at the 50% probability
level for non-H atoms. The N3–C9 and N7–C12 bonds form an obtuse angle.
Figure 1. Graph showing increase in Rf value in 70:30 petroleum ether/ethyl acetate (A)
and decrease in melting point (-) with increasing alkyl chain length. Best-fit lines
through the two sets of points give: Rf¼(0.0495ꢀno. C atoms)þ0.2705; mp¼(ꢁ5.15ꢀno.
C atoms)þ77.9.
Butler et al. have described the synthesis of tetra-tetrazole
macrocycles, based on either 1,2- or 1,3-bis(tetrazol-5-yl)ben-
zenes, with alkyl chains having either six or eight-carbon chain
linkers.28–30 We have extended this class of compounds by pre-
paring macrocycles with four-carbon chain linkers, and also new
macrocycles based on 1,4-bis(tetrazol-5-yl)benzene,22 by reacting
1,x-[bis(2-(y-bromoalkyl)tetrazol-5-yl)]benzene (x¼2, 3 or 4; y¼4,
6 or 8; alkyl¼n-butyl, n-hexyl or n-octyl) with 1,n-bis(tetrazol-
5-yl)benzene (n¼2, 3 or 4) in dimethylformamide, using K2CO3 as
Figure 3. Molecular structure of 3 with displacement ellipsoids at the 50% probability
level for non-H atoms. A crystallographic twofold axis passes through atoms C1 and C4.
The N3–C9 and N7–C12 bonds form an acute angle.
In 2 and 3, the tetrazole rings are close to coplanar with the
benzene ring to which they are attached, and the bromoalkyl groups

7944
A.D. Bond et al. / Tetrahedron 65 (2009) 7942–7947
Figure 4. Projection of the crystal structure of 2 along the a axis, showing the layered structure with ‘Type II’ Br/Br contacts between layers. H atoms are omitted.
Figure 5. Projection of 3 along the c axis, showing the layered structure with ‘Type I’ Br/Br contacts between layers. H atoms are omitted.
project to either side of this plane. This feature of the molecular
conformation is similar to 10a, while the bromoalkyl groups project
to the same side of the molecular plane in the polymorph 10. In 3,10
and 10a, the substituted 2-N atoms point in the same direction so
that the two N–CH2 bond vectors form an acute angle (see Fig. 3).
The conformation of 2 is distinct in that one tetrazole ring is flipped
over with respect to the molecular plane so that the two N–CH2
bond vectors form an acute angle (see Fig. 2). In 3 and 10a, the
molecules lie on crystallographic twofold axes, while in 10 they
display approximate (non-crystallographic) mirror symmetry.
The structures of 2 and 3 contain similar 2-D layers (Figs. 4 and 5).
The central sections of the molecules approach each other in a side-
on manner, forming 1-D motifs along the b direction. Thus, the
length of the b axis is closely comparable in the two crystal struc-
tures. In both cases, the 1-D motifs are arranged in an anti-parallel
Crystals of 7 were obtained from chloroform solution, and the
crystal structure confirms the expected tetra-tetrazole macrocyclic
structure, with each tetrazole ring substituted at the 2-N position, as
suggested by 13C NMR spectroscopy. The structure also reveals an
manner, with adjacent molecules forming slipped
p-stacked
arrangements. The perpendicular distance between molecular
planes is 3.37(1) Å in 2 and 3.21(1) Å in 3, and the centroid–centroid
distances for interacting phenylene rings are 4.684 and 6.013 Å in 2,
and 5.409 and 6.104 Å in 3.
In 3, adjacent 2-D layers meet so as to bring the terminal CH2–Br
bonds into an offset co-linear alignment (Fig. 5), forming ‘Type I’
Br/Br interactions, as classified previously by Desiraju et al.33 The
intermolecular Br/Br distance is 3.489(2) Å, which is considerably
shorter than twice the bromine van der Waals radius (3.90 Å) and
within the range of those values previously reported, 3.415–
3.691 Å.23,34–36 In 2, the Br/Br interactions resemble side-on ‘Type
II’ interactions, with a shortest distance of 3.771(3) Å.
Figure 6. Molecular structure of 7 with displacement ellipsoids at the 50% probability
level for non-H atoms. The CHCl3 molecule is disordered about a crystallographic
twofold rotation axis; atoms with suffix A are generated by the symmetry operator
ꢁx, y, 1
⁄ -z. Dashed lines represent C–H/p interactions.
2

A.D. Bond et al. / Tetrahedron 65 (2009) 7942–7947
7945
University College Dublin using a Micromass/Waters Corp. Liquid
chromatography time-of-flight (LCT) mass spectrometer equipped
with an electrospray source. Microanalysis was carried out at the
Microanalytical Laboratory of University College, Dublin. Standard
Schlenk techniques were used throughout. Starting materials were
commercially obtained and used without further purification. The
synthesis of compound 1 has been described in the literature
previously.24
4.2. General syntheses of 1,n-bis(bromo-
alkyltetrazolyl)benzenes
Compound 1 (1.0 g, 0.47 mmol) was dissolved in methanol
(30 ml) and, to the stirred solution, was added triethylamine (3.0 ml,
2.8 mmol). The resulting solution was heated to reflux for 30 min,
and to the hot solution was added 1,n-dibromoalkane (1.4 mmol).
The reaction mixture was then heated to reflux for a further 24 h.
After cooling, the solvent was removed under reduced pressure to
afford an oil, which was thenpurified bycolumn chromatography on
silica gel (initiallyat the ratio of petroleum ether/ethyl acetate80:20,
followed by the ratio 60:40).
Figure 7. Partial packing diagram of 7 showing the bowl-shaped macrocycles stacked
in columns along the b axis. Both orientations of the disordered CHCl3 molecule are
shown. H atoms are omitted.
4.2.1. 1,3-Bis[(3-bromoproyl)tetrazol-5-yl]benzene (2-N,2-N0)
(2). White solid. Analysis: Found: C, 37.12; H, 3.58; N, 24.41. Calcd
for C14H16N8Br2: C, 36.86; H, 3.54; N, 24.57; yield: 0.32 g, 16%,
0.70 mmol; Rf 0.43 (70:30 petroleum ether/ethyl acetate); mp 62–
64 ꢂC; nmax (KBr) 3421, 2919, 2847, 1623, 1521, 1455, 1347, 1276,
unexpected ‘host–guest’ interaction between the macrocycle and
a molecule of chloroform solvent (Fig. 6). The molecule lies on
a crystallographic twofold rotation axis, and the CHCl3 molecule is
disordered equally over two orientations about this axis, forming
1194, 1086, 799, 743 cmꢁ1
; dH: 2.65 (m, 4H, CH2), 3.49 (t, 4H,
C–H/p interactions in which the H atom lies 2.50 Å above the mean
J¼6.8 Hz, CH2Br), 4.88 (t, 4H, J¼5.6 Hz, tetrazole N2–CH2), 7.64 (t,
1H, J¼7.9 Hz, Ar-H), 8.29 (dd, 2H, J¼7.6, 1.2 Hz, Ar-H), 8.92 (s, 1H, Ar-
H); dC: 29.0, 31.0 (CH2Br), 51.0 (tetrazole N2–CH2), 125.2, 128.0,
128.1, 129.0, 164.0 (2,5-tetrazole).
plane of the phenylene ring. The interaction and encapsulation of the
CHCl3 molecule is facilitated by a bowl-shaped conformation of
the tetra-tetrazole macrocycle, which is distinctly different from the
essentially flat structure that we have reported for a similar six-
carbon linked macrocycle for which no solvent is present.22 The
molecules of 7 are stacked in columns parallel to the b axis (see Fig. 7)
4.2.2. 1,3-Bis[(5-bromopentyl)tetrazol-5-yl]benzene (2-N,2-N0)
(3). White solid. Analysis: Found: C, 42.46; H, 4.77; N, 21.74. Calcd
for C18H24N8Br2: C, 42.40; H, 4.72; N, 21.88; yield: 0.32 g, 18%,
0.62 mmol; Rf 0.50 (70:30 petroleum ether/ethyl acetate); mp 51–
52 ꢂC; nmax (KBr) 3448, 2956, 2922, 2851, 1638, 1513, 1456, 1430,
with p–p stacking interactions between neighbouring tetrazole and
phenylene rings (centroid–centroid distance 3.694 Å). Similar in-
teractions have been observed in other tetrazole structures.22–25
1385, 1271, 1196, 1048, 904, 799, 740, 689, 638 cmꢁ1
; dH: 1.55 (m,
3. Conclusions
4H, CH2), 1.86 (m, 4H, CH2), 2.01 (m, 4H, CH2), 3.41 (t, 4H, J¼6.4 Hz,
CH2Br), 4.70 (t, 4H, J¼7.6 Hz, tetrazole N2–CH2), 7.63 (t, 1H,
J¼7.6 Hz, Ar-H), 8.24 (dd, 2H, J¼7.6, 1.2 Hz, Ar-H), 8.92 (s, 1H, Ar-H);
dC: 24.8, 28.3, 31.7, 32.9 (CH2Br), 52.8 (tetrazole N2–CH2), 125.0,
128.3, 128.5, 129.4, 164.0 (2,5-tetrazole).
In this paper, we have reported on the syntheses and character-
isation of bromoalkyl derivatives of 1,3-bis(tetrazole)benzene, where
the alkyl chain contains either 3, 5, 7 or 9 carbons atoms. In-
terestingly, the predominant compound formed in all these reactions
is the symmetric 2-N,2-N0-bistetrazole isomer, whereas the same
reactions carried out with even n-alkyl chains have previously yiel-
ded both symmetric 2-N,2-N0-bistetrazole and asymmetric 1-N,2-N0-
bistetrazole derivatives. Four new macrocycles containing four tet-
razole rings were synthesised and the X-ray crystal structure of 7
showed a bowl-shaped conformation with an interesting host–guest
interaction with an encapsulated solvent chloroform molecule.
4.2.3. 1,3-Bis[(7-bromoheptyl)tetrazol-5-yl]benzene (2-N,2-N0)
(4). White solid. Analysis: Found: C, 46.38; H, 5.69; N, 19.45. Calcd
for C22H32N8Br2: C, 46.49; H, 5.67; N, 19.72; yield: 0.32 g, 12%,
0.56 mmol; Rf 0.62 (70:30 petroleum ether/ethyl acetate); mp 41–
42 ꢂC; nmax (KBr) 3430, 3016, 2934, 2858, 1625, 1521, 1455, 1347,
1214, 1040, 932, 800, 753, 671 cmꢁ1
; dH: 1.55 (m, 12H, CH2), 1.88 (m,
4H, CH2), 2.09 (m, 4H, CH2), 3.38 (t, 4H, J¼5.9 Hz, CH2Br), 4.68 (t, 4H,
J¼5.9 Hz, tetrazole N2–CH2), 7.63 (t, 1H, J¼8.1 Hz, Ar-H), 8.27 (dd,
2H, J¼7.6, 1.2 Hz, Ar-H), 8.93 (s, 1H, Ar-H); dC: 26.1, 27.7, 29.1, 32.5,
33.7 (CH2Br), 53.1 (tetrazole N2–CH2), 125.1, 128.2, 128.4, 129.4,
164.0 (2,5-tetrazole).
4. Experimental
4.1. General
1H and 13C NMR (
d
ppm; J Hz) spectra were recorded on a JEOL
4.2.4. 1,3-Bis[(9-bromononyl)tetrazol-5-yl]benzene (2-N,2-N0)
(5). White solid. Analysis: Found: C, 50.18; H, 6.46; N, 16.91. Calcd
for C26H40N8Br2: C, 50.01; H, 6.46; N, 17.94; yield: 0.61 g, 21.3%,
0.98 mmol; Rf 0.72 (70:30 petroleum ether/ethyl acetate); mp 31–
33 ꢂC; nmax (KBr) 3442, 2919, 2849, 1654, 1526, 1455, 1347, 1256,
JNM-LA300 FT-NMR spectrometer using saturated CDCl3 solutions
with Me4Si reference, unless indicated otherwise, with resolutions
of 0.18 Hz and 0.01 ppm, respectively. Infrared spectra (cmꢁ1) were
recorded as KBr discs or liquid films between KBr plates using
a Nicolet Impact 410 FT-IR. Melting point analysis was carried out
using a Stewart Scientific SMP 1 melting point apparatus and is
uncorrected. Mass spectra were obtained from the CSCB Mass
Spectrometry Centre, School of Chemistry and Chemical Biology,
1191, 1082, 788, 742, 723, 683, 648 cmꢁ1
; dH: 1.37 (m, 20H, CH2),
1.84 (m, 4H, CH2), 2.08 (m, 4H, CH2), 3.39 (t, 4H, J¼6.3 Hz, CH2Br),
4.67 (t, 4H, J¼5.9 Hz, tetrazole N2–CH2), 7.63 (t, 1H, J¼7.9 Hz, Ar-H),
8.27 (dd, 2H, J¼7.6, 1.2 Hz, Ar-H), 8.94 (s, 1H, Ar-H); dC: 26.2, 28.1,

7946
A.D. Bond et al. / Tetrahedron 65 (2009) 7942–7947
28.5, 28.7, 29.1, 29.3, 32.2, 34.0 (CH2Br), 53.2 (tetrazole N2–CH2),
125.1, 128.2, 128.4, 129.4, 164.0 (2,5-tetrazole).
collected on a Bruker Nonius X8 APEXII diffractometer37 at 180(2) K
and 298(2) K, respectively, and data for 7 were collected at 150(2) K
on a Bruker APEXII diffractometer. In each case Mo Ka radiation
4.3. General syntheses of tetra-tetrazolophanes
(
l
¼0.71073 Å) was used, a multi-scan correction was applied38 and
the structure was refined against F2 using all data. All non-hydrogen
atoms were refined with anisotropic atomic displacement param-
eters and hydrogen atoms were placed at calculated positions and
refined using a riding model.
A mixture of 1 (240 mg, 1.1 mmol) and potassium carbonate
(1.5 g,11 mmol) in dimethylformamide (60 ml) was stirred for 1 h at
75 ꢂC under an nitrogen atmosphere, and then treated with the
appropriate 1,n-bis(bromoalkyltetrazolyl)benzene (2–5, 1.1 mmol)
and stirred at 75 ꢂC for 24 h. Insoluble salts, filtered from the cooled
mixture, were washed with ethyl acetate and the combined wash-
ings and mother-liquor were evaporated under reduced pressure.
The white residue, which remained was dissolved in chloroform and
chromatographed on silica gel using DCM/MeOH (99.5:0.5–99.0:1.0
v/v) as eluent to give the tetra-tetrazolophane macrocycle.
4.4.1. Compound 2. Crystal data: C14H16Br2N8, M¼456.17, triclinic,
a¼7.0009(4),
b¼7.1694(4),
c¼17.5789(10) Å,
a
¼100.518(2),
b
¼92.790(2),
g
¼92.019(2)ꢂ, U¼865.60(5) Å3, space group P-1, Z¼2,
m
¼4.697 mmꢁ1
,
rcalcd¼1.750 g cm–3
. 33,334 data (3891 unique,
Rint¼0.0285) were measured in the range 3.54<
q
<28.34ꢂ.
R1(I>2
s(I))¼0.0312 and wR2(all data)¼0.0863. Goodness of fit on
F2¼1.06. CCDC No. 725917.
4.3.1. Di-meta-benzenotetra(50,20-tetrazolo)[50-(2)-20-(3)]-cyclo-
phane (2-N,2-N0,2-N00,2-N000) (6). White solid. Analysis: Found: C,
51.83; H, 4.01; N, 44.17. Calcd for C22H20N16: C, 51.96; H, 3.96; N,
44.07; yield: 0.28 g, 50.0%, 0.55 mmol; Rf 0.14 (40:60 petroleum
ether/ethyl acetate); mp>300 ꢂC; nmax (KBr) 3439, 2927, 2852,1637,
4.4.2. Compound 3. Crystal data: C18H24Br2N8, M¼512.27, mono-
clinic, a¼34.3306(7), b¼7.0548(1), c¼9.0546(2) Å,
b
¼102.433(1)ꢂ,
U¼2141.55(7) Å3, space group
C
2/c, Z¼4,
m
¼3.806 mmꢁ1
,
rcalcd¼1.589 g cm–3. 8687 data (2034 unique, Rint¼0.0232) were
1515,1455,1432,1357,1214,1088,1047, 920, 786, 746, 691 cmꢁ1
;
dH:
measured in the range 3.65<
q
<25.73ꢂ. R1(I>2
s(I))¼0.0328 and
2.18 (m, 4H, CH2), 4.68 (t, 8H, J¼6.9 Hz, NCH2), 7.63 (t, 2H, J¼7.9 Hz,
Ar-H), 8.27 (d, 4H, J¼7.9 Hz, Ar-H), 8.72 (s, 2H, Ar-H); dC: 22.9, 29.0,
52.6 (tetrazole N2–CH2), 126.3, 128.0, 128.5, 129.6, 164.4 (2,5-tet-
razole); HRMS (ES) calcd [Mþ1] 509.502, found 509.504.
wR2(all data)¼0.0827. Goodness of fit on F2¼1.03. CCDC No. 725918.
4.4.3. Compound 7. Crystal data: C27H29Cl3N16, M¼684.01, mono-
clinic, a¼24.584(3), b¼6.5069(8), c¼22.926(3) Å,
b
¼119.469(2)ꢂ,
U¼3192.9(6) Å3, space group
C
2/c, Z¼4,
m
¼0.335 mmꢁ1
,
4.3.2. Di-meta-benzenotetra(50,20-tetrazolo)[50-(2)-20-(5)]-cyclo-
phane (2-N,2-N0,2-N00,2-N000) (7). White solid. Analysis: Found: C,
55.65; H, 5.09; N, 39.47. Calcd for C26H28N16: C, 55.31; H, 5.00; N,
39.69; yield: 0.25 g, 40.0%, 0.44 mmol; Rf 0.35 (40:60 petroleum
ether/ethyl acetate); mp>300 ꢂC; nmax (KBr) 3435, 2927, 2852,1647,
1523, 1455, 1432, 1390, 1357, 1214, 1088, 1047, 820, 786, 746,
rcalcd¼1.423 g cm–3. 13,630 data (3282 unique, Rint¼0.0472) were
measured in the range 1.90<
q
<26.45ꢂ. R1(I>2
s(I))¼0.0426 and
wR2(all data)¼0.1213. Goodness of fit on F2¼0.937. CCDC No. 725395.
5. Supplementary data
690 cmꢁ1
; dH: 1.25 (m, 4H, CH2), 2.23 (m, 8H, CH2), 4.69 (t, 8H,
Crystallographic data for 2, 3 and 7 have been deposited with the
Cambridge Crystallographic Data Centre, CCDC Nos. 725917, 725918
and 725395. Copies of this information may be obtained free of
charge from deposit@ccdc.cam.ac.uk or www:http://www.ccdc.
cam.ac.uk.
J¼6.8 Hz, NCH2), 7.61 (t, 2H, J¼7.9 Hz, Ar-H), 8.27 (d, 4H, J¼7.9 Hz,
Ar-H), 8.72 (s, 2H, Ar-H); dC: 22.9, 28.7, 29.7, 52.6 (tetrazole N2–
CH2), 125.8, 127.9, 128.4, 129.5, 164.6 (2,5-tetrazole); HRMS (ES)
calcd [Mþ1] 565.608, found 565.273.
4.3.3. Di-meta-benzenotetra(50,20-tetrazolo)[50-(2)-20-(7)]-cyclo-
phane (2-N,2-N0,2-N00,2-N000) (8). White solid. Analysis: Found: C,
58.35; H, 6.11; N, 35.88. Calcd for C30H36N16: C, 58.05; H, 5.85; N,
36.10; yield: 0.14 g, 20%, 0.23 mmol; Rf 0.49 (40:60 petroleum
ether/ethyl acetate); mp 258–260 ꢂC; nmax (KBr) 3423, 2922, 2853,
1648, 1523, 1452, 1430, 1384, 1357, 1214, 1088, 1045, 912, 781, 746,
Acknowledgements
We thank the Postgraduate R&D Skills programme (Technolog-
ical Sector Research, Strand I, Project Code CRS/01/TA02) for fi-
nancial assistance. A.D.B. is grateful to the Danish Natural Sciences
Research Council and the Carlsberg Foundation for provision of the
X-ray equipment.
692 cmꢁ1
; dH: 0.80 (m, 8H, CH2), 1.18 (m, 4H, CH2), 2.02 (m, 8H,
CH2), 4.59 (t, 8H, J¼6.6 Hz, NCH2), 7.51 (t, 2H, J¼7.9 Hz, Ar-H), 8.17
(d, 4H, J¼7.9 Hz, Ar-H), 8.77 (s, 2H, Ar-H); dC: 22.7, 26.0, 29.7, 53.1
(tetrazole N2–CH2), 125.7, 128.2, 128.4, 129.5, 164.5 (2,5-tetrazole);
HRMS (ES) calcd [Mþ1] 621.330, found 621.332.
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