Chromogenic derivatives of new bis(phenylhydrazono-1 H-tetrazol-5-yl- acetonitriles)-synthesis and properties

Article abstract of DOI:10.1080/10610278.2012.701303

Derivatives of bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) with oxygen and sulphur atoms in the structure of aliphatic chains were successfully synthesised. The correlation between the ligand structure and its complexation properties was investiga

Full text of DOI:10.1080/10610278.2012.701303

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Supramolecular Chemistry
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Chromogenic derivatives of new
bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) –
synthesis and properties
A. Pazik a & A. Skwierawska a
a Department of Chemical Technology, Gdansk University of Technology, Narutowicza Street
11/12, 80-233, Gdansk, Poland
Version of record first published: 09 Jul 2012.
To cite this article: A. Pazik & A. Skwierawska (2012): Chromogenic derivatives of new bis(phenylhydrazono-1H-tetrazol-5-yl-
acetonitriles) – synthesis and properties, Supramolecular Chemistry, 24:10, 726-737
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Supramolecular Chemistry
Vol. 24, No. 10, October 2012, 726–737
Chromogenic derivatives of new bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) – synthesis
and properties
A. Pazik* and A. Skwierawska
Department of Chemical Technology, Gdansk University of Technology, Narutowicza Street 11/12, 80-233 Gdansk, Poland
(Received 6 May 2012; final version received 1 June 2012)
Derivatives of bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) with oxygen and sulphur atoms in the structure of
aliphatic chains were successfully synthesised. The correlation between the ligand structure and its complexation properties
was investigated by absorption spectroscopy. The formation of complexes of presented compounds with metal cations
(Cu2þ, Ni2þ, Zn2þ, Co2þ, Fe2þ and Pb2þ) was studied. Ligands 5–8 were additionally applied as ion carriers in ion-selective
membrane electrodes. Membranes of ion-selective electrodes doped with these ligands are selective to Cu2þ and Pb2þ
cations.
Keywords: UV–vis spectroscopy; chromoionophores; membrane electrodes; bis-tetrazole; synthesis
(CH2)m
N
N
Introduction
N
N
N
N
N
In recent years, the development of supramolecular
chemistry in a range of molecular receptors has been
related to the high demand for new, miniature tools,
biosensors and molecular devices. Different methods of
synthesis of molecular receptors allow obtaining highly
important receptors. According to Pearson Hard-Soft
Acid-Base (HSAB) theory, hard electron donor atoms like
oxygen atoms attract preferentially electron acceptors
such as alkali or alkaline earth cations (1–3). Spherical
shapes of cations greatly facilitate design of appropriate
host molecules (4, 5). Tetrazoles due to their structure and
similarity to the carboxylic acids can bind metal ions
forming complexes with different molar ratios. They are
used to design new bioreceptors, drugs (6–8) and
coordination polymers (9). Tetrazoles are also used as
materials for photography (10), in data recording systems,
as ligands for analytical reagents and in explosives (11).
In biological systems, the tetrazole NZH group occurs
mainly in the neutral or anionic form.
N
N
N
N
H
H
N
X
N
N
N
X
N
N
N
(CH2)m
N
N
X=Cl, Me; m=3, 4, 6
This macrocycle is the first example of compound, in
which tetrazole and hydrazone residues were involved in
complexation of metal cations. The literature data on this
type of compounds are quite poor and do not concern
complexation and ions transport through membranes or
equilibrium studies in solution. Furthermore, according to
recent research, some phenylhydrazono-1H-tetrazol-5-yl-
acetonitrile derivatives with different substituents in the
phenyl ring have antimicrobial activities; particularly they
show greater activities against Gram-positive than Gram-
negative bacteria (17).
In our research, we focus on the synthesis of new
ionophores for the selective recognition of transition and
heavy metal ions. We herein report the synthesis of
bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) che-
lating reagents (Figure 1). The binding ability of compounds
5–8 with metal ions has been studied using UV–vis
spectroscopy. Ligands with different cavity size and
heteroatoms in the linkage are described and their selectivity
for the metal ions was compared. UV–vis spectroscopic
studies show that all compounds are able to complex Cu2þ
ions only with one exception, i.e. compound 5, which forms
also complexes with Zn2þ and Ni2þ cations. In addition, all
Recently, the synthesis of tetrazoles has gained
significant interest. The most direct synthetic procedure
of 1,5-substituted tetrazoles is cycloaddition of nitriles and
azides catalysed by, for example, Brønsted and Lewis acids
(e.g. ZnCl2 and ZnBr2) (12) in water. New reports describe
also use of heterogeneous catalyst (13), nanoparticles
(14) and CoY zeolite (15) and microwave irradiation.
The first macrocyclic molecule containing tetrazole residue
was synthesised in 1992 by Butler (16). Its structure is
presented below.
*Corresponding author. Email: mikaga20@wp.pl
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2012.701303
http://www.tandfonline.com

Supramolecular Chemistry
727
ammonium chloride in N,N-dimethylformamide (DMF).
After reaction in order to release the anionic tetrazolate
salt mixture is treated with concentrated sulphuric acid.
The reaction proceeds via a traditional [2 þ 3] mechan-
ism. The mechanism of the addition of azide ion to nitrile
involves the activation of nitrile by protonation, proceed-
ing through a previously unsuspected imidoyl azide
intermediate. Interestingly, only two tetrazole rings can be
introduced into the systems in one reaction step.
Compounds 5–8 were obtained in good yield (52–
88%) and purified by crystallisation from water. The
compounds are brown (5 and 7) and yellow (6 and 8)
solids. The progress of diazo salt coupling reaction was
monitored by 1H NMR spectroscopy. The 1H NMR spectra
confirmed formation of hydrazones NZH signals at
10.53 ppm (Figure 3, e.g. 3) and the cyclisation reaction
with the wide signal at 4.9 ppm characteristic for tetrazole
NZH band. IR spectra show two typical CuN bands at ca.
2233 and 2200 cm21. After formation of tetrazole ring,
one of the CuN bands (2233 cm21) disappears (Figure 4);
furthermore, it shows characteristic tetrazole ring defor-
mation vibrations that reflect presence of different groups
(e.g. CZN, NZH and NZN bands). Surprisingly, tetrazole
ligands 5–8 with hydrazone bonds and their spectroscopic
properties have never been studied. Accordingly, we have
prepared a series of bis-ligands differing in length and
Figure 1. Chemical structures of ligands studied.
compounds have been studied as ion carriers in ion-selective
membrane electrodes. Selectivity of these membranes
towards various cations and anions was determined.
Results and discussion
Synthesis
The synthetic approach to new bis(phenylhydrazono-1
H-tetrazol-5-yl-acetonitriles) 5–8 is shown in Figure 2.
1,1-Dicyanohydrazone derivatives 1–4 were obtained
according to the well-known method from malononitrile
with diazo salts, which were synthesised from appropriate
diamines. The final step of reaction was formation of
tetrazole ring in reaction of nitriles with sodium azide and
Figure 2. Synthesis of bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) derivatives 5–8. Reagents and conditions: (i) NaNO2/HCl,
0–58C, C3H2N2, EtONa/EtOH; (ii) NaN3, NH4Cl, DMF, 1208C, 24 h.

728
A. Pazik and A. Skwierawska
Figure 3. 1H NMR (500 MHz, CDCl3) of 1,8-bis[2-(phenylhydrazonodi-acetonitriles) phenoxy]-3,6-dioxaoctane (3).
heteroatoms of linkage. We assume that even small
structural changes can modify their complexing properties.
complexes and coordination polymers with high thermal
stability.
The UV–vis absorption maxima (lmax) and molar
extinction coefficients of ligands 5–8 are summarised in
Table 1. In methanol solution, ligands 5–7 show absorption
bands in the range 200–450 nm with a maximum at about
361–370 nm. Introduction of sulphur atoms into ligand 8
structure caused major changes in values of molar
extinction coefficients comparing with compound 6.
Ligands 5–8 represent an interesting chelating system.
The frame is based on dibenzo-substituted mixed-donor
Spectrophotometric studies of metal cation complexation
Design of potential sensing material for transition and
heavy metal cations is nowadays very important from
medical/clinical point of view because they accumulate in
the human body and cause numerous diseases. Tetrazoles,
due to their similarity to carboxylic acids (pKa values)
and p-acceptor properties, are able to form metal
Figure 4. IR spectra of 1,1-dicyanohydrazone derivative 1 and bis-tetrazole derivative 5 in KBr.

Supramolecular Chemistry
729
absorbance spectra were observed. Absorption spectra of
ligands 5–8 upon addition of 10-fold excess of transition
metal and lead chlorides are shown in Figure 5. Probably,
ligands 5 and 6 show the best adjustment to transition metal
cations. The most significant changes for compound 5
Table 1. The absorption maxima (lmax) and corresponding
extinction coefficients of new bis-tetrazole 5–8 in MeOH at
298 K.
Compounds
lmax (nm)
1 (M21 cm21
)
5
6
7
8
361
362
363
370
166,000
74,600
66,200
219,000
in absorption spectra were observed in the presence of Cu2þ
,
Zn2þ, Co2þ and Ni2þ chlorides. Bis-tetrazole 6 exhibits
increase of maxima upon addition of Fe2þ chloride;
however, the last ions do not influence absorbance of other
ligands. It is worth to note that only ligands 6 and 8 show
positive response to Pb2þ chloride. Furthermore, spectro-
scopic titration of compound 6 with Pb2þ shows continuous
increase of the main band that makes determination of
complexation constant impossible (Figure 6). Introduction
of two sulphur atoms makes the ligands more sensitive to
Ni2þ and Co2þ ions. All ligands show response to Cu2þ ions
and form complexes with it of diversified stoichiometry.
UV–vis titrations were carried out to estimate the
stability constant values of the respective complexes with
Cu2þ, Ni2þ and Zn2þ ions. Changes in UV–vis absorption
structure incorporating oxygen, sulphur and nitrogen atoms.
Aliphatic chain with heteroatoms is the most flexible part of
the molecule which allows to adjust the host to the guest
molecules. Conjugated phenylhydrazono-acetonitriles form
chromogenic but more rigid system which required accurate
guest. In the preliminary studies, spectroscopic titration of
compounds 5–8 with Liþ, Naþ, Kþ, Mg2þ, Ca2þ, Co2þ
,
Cu2þ, Ni2þ, Pb2þ, Fe2þ and Zn2þ chlorides in methanol
solution was carried out. In case of chlorides of metals of the
first and second groups of the periodic table, any changes in
Figure 5. Absorption spectra of bis(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles) in the presence of 10-fold excess of metal
chlorides in methanol. (a) 5 (c ¼ 1026 M); (b) 6 (c ¼ 5 £ 1026 M); (c) 7 (c ¼ 1025 M); (d) 8 (c ¼ 3 £ 1026 M).

730
A. Pazik and A. Skwierawska
Figure 6. UV–vis titration of compound 6 (c ¼ 1025 mol dm23
)
with Pb(ClO4)2 (c ¼ 0–3.5 £ 1025 M) in methanol solution.
spectra of compounds 6 and 7 under various concen-
trations of Cu2þ perchlorate in methanol are shown in
Figures 7 and 8. A molar ratio plot revealed that under
titration experiments complexes of 1:4 and 1:2 stoichi-
ometry for ligands 6 and 7 were found, respectively.
The association constants were determined to be
4.43 £ 107 M21 for 6 Cu2þ and 2.6 £ 107 M21 for 7
Cu2þ complexes (Figure 9). As the concentration of Cu2þ
increased, the absorption maximum of the free ligands 6
and 7 at 362 and 363 nm is shifted to 382 and 378 nm,
respectively. In contrast, control compound 3 with 1,1-
dicyanohydrazones units showed also batochromic shift
that relies on spectral band shift from 371 nm to longer
wavelength 381 nm (see titration of compound 3 in
Figure 10). The stoichiometry of complex with Cu2þ was
1:1.3, and the value of Ka was determined to be
4.2 £ 107 M21. Comparing the results with those obtained
for compound 7, the stability constant value for Cu2þ
complex is higher than for its tetrazole analogue.
Figure 7. (a) Changes in UV–vis absorption spectrum of ligand
6 (c ¼ 5 £ 1026 M) upon increasing concentration of Cu(ClO4)2
(c ¼ 0–0.47 £ 1024 M) in methanol solution. (b) Titration plot
to determine the stability constant of the complex between 6 and
Cu2þ(1:4) at 400 nm.
In addition, the formation of the new wide band at 264 nm
was also observed in spectrum of 5 with Ni2þ ions.
Different patterns of spectroscopic changes in absorp-
tion spectra may suggest that the length of the polyether
linker is essential in the complexation properties. The
smaller is the cavity size, the better is the selectivity
towards transition metal cations. Modifications in the
polyether chain with the sulphur atom do not improve
selectivity of compound. Moreover, we supposed that the
cation is implemented inside the ligand cavity between
hydrazone bonds and tetrazole rings. However, different
patterns of spectroscopic changes in absorption spectra
(increase without batochromic shift) in case of Pb2þ ions
and our earlier studies may confirm that only tetrazole
rings are involved in complexation.
Furthermore, the results from UV–vis titration of
ligands 5 and 8 upon titration with various concentrations
of Cu2þ in methanol are presented in Figure 9. For UV–vis
titration ligand 8, the absorption maximum at 370 nm
is shifted to 382 nm, whereas in case of ligand 5 the band
at 361 nm is shifted to 379 nm with one isosbestic point
at 322 nm. The increase of the main band and major
concentration of the salt makes determination of complexa-
tion constant impossible for these compounds.
We observed the same problem with stability constants
under UV–vis absorption spectra for 5 and 6 with Ni2þ
and Zn2þ ions (Figure 11). The absorption spectra of
5 with Ni2þ and Zn2þ with various concentrations of the
ions show batochromic shift; absorption band at 361 nm is
shifted to 386 and 375 nm, respectively. In case of
spectroscopic titration of 5 with Zn(ClO4)2, the formation
of a new band at 271 nm was observed (Figure 12).
To prove our hypothesis on complexation properties,
additional experiments were carried out using IR spec-
troscopy. An IR spectrum of ligand 7 in the presence of Cu2þ
chloride was recorded within the range of 3500–500 cm21
.
The initial stage of the process was to prepare a sample for

Supramolecular Chemistry
731
Figure 9. UV–vis titration of compound (a) 8 (c ¼ 3 £ 1026
mol dm23) with Cu(ClO4)2 (c ¼ 0–2.5 £ 1025 M); (b) 5
(c ¼ 1026 mol dm23) with Cu(ClO4)2 (c ¼ 0–0.52 £ 1025 M) in
methanol solution.
Figure 8. (a) Changes in UV–vis absorption spectrum of ligand
7 (c ¼ 1025 mol dm23) with Cu(ClO4)2 (c ¼ 0–0.44 £ 1024 M)
in methanol solution. (b) Titration plot to determine the stability
constant of the complex between 7 and Cu2þ(1:2) at 400 nm.
750 cm21 and the appearance of new signal at 680 cm21
.
testing. By using a molar excess of salt, we took 7 and CuCl2
separately and dissolved then in small amount of chloroform
and methanol, respectively; then the solutions were
combined, stirred and the solvents were evaporated to
dryness. The residue was dried in vacuum and protected
from moisture. The obtained solid and dry KBr was used
in the preparation of tablets for IR spectroscopy. Results of
our experiments are presented in Figure 13. A reference
spectrum was taken from pure ligand 7 in KBr. The changes
in ligand 7 spectrum upon complexation are significant.
Complexation can be observed in the loss of stretching
vibration at 1552cm—1, and the new signals can be found
below 1453cm21. The band is characteristic of bond
stretching vibration for coordinated tetrazole rings and can
be assigned to CvN vibrations.
It was noteworthy that after Cu2þ ions complexation by 7,
new strong absorptions bands at 3350 and 3440cm21 were
observed. The symmetry of complex and 1:2 stoichiometry
is observed in IR spectroscopy in the two large signals
deriving from two tetrazole NZH stretching vibration and
NZH hydrazone bonds. No changes in the intensities of
absorption characteristic for nitrile groups CuN suggest
that it is not engaged in the complex.
Molecular simulation
To understand the structure of 7 and the nature of bonding
interaction with the cations, ground-state optimisation was
carried out using Gaussian 03 software with B3LYP and
6-31 þ þ G(dp) basis set at the density functional theory
level. The optimised global minima of receptor 7 show that
the NZH hydrazone moieties are not in the same plane
(Figure 14). The optimised structure of 7 shows that
After complexation, up-shift of 55cm21 can be observed
in the enhanced band at 1239cm21, which is also due to
stretching vibration of the tetrazole rings. Deformation of
the substituted hydrazone bonds in the phenyl ring and its
complexation properties can be seen in the absorption at
˚
distances N1· · ·H1 and N2· · ·H2 are 1.063 A, the same

732
A. Pazik and A. Skwierawska
Figure 11. UV–vis titration of compound (a)
5
(c ¼ 1026 mol dm23) with Ni (ClO4)2 (c ¼ 0–0.44 £ 1024 M);
(b) 6 (c ¼ 5 £ 1026 mol dm23) with Ni (ClO4)2 (c ¼ 0–
0.41 £ 1024 M) in methanol solution.
Figure 10. (a) UV–vis titration of compound
3
(c ¼ 1025 mol dm23) with Cu(ClO4)2 (c ¼ 0–0.37 £ 1024 M)
in methanol solution. (b) Titration plot of the complex between 3
and Cu2þ(1:1.3) at 347 nm.
potassium tetrakis(4-chlorophenyl) borate (KTpClPB),
65.7% (w/w) 2-nitrophenyl octyl ether (o-NPOE) and
32.9% (w/w) poly(vinyl chloride) (PVC). Membrane
components, total 182.5 mg, were dissolved in 1.5 ml of
value. In the presence of Cu2þ ions, ligand 7 rearranges
itself from a flexible conformer to a more rigged system
presented in Figure 15 and forms 1:2 complexes with Cu2þ
ion. The structure of 7 Cu2þ complex shows that two Cu2þ
ions are nitrogen bonded within distances
2þ
N1· · ·Cu2þ ¼ 2.0309 A (N2· · ·Cu ¼ 2.0395 A) and
˚
˚
2þ
N3· · ·Cu2þ ¼ 2.036 A (N4· · ·Cu ¼ 2.026 A). However,
the Pb2þ ion can fit between tetrazole rings and forms 1:1
complex (Figure 16) with a small change in the structure of
the conformer. The optimised structure of complexes
shows that in both cases cations are differently located in
the cavity which is formed between hydrazone bonds and
tetrazole rings, which confirm our earlier hypothesis
(Table 2).
˚
˚
Membrane electrodes and potentiometric measurements
Properties of compounds 5–8 as ion carriers have been
tested using membrane electrodes. The examined mem-
branes consisted of 1.1% (w/w) ionophore, 0.3% (w/w)
Figure 12. Absorption spectra recorded in methanol solution
containing ligand 5 (c ¼ 1026 M) with Zn(ClO4)2 (c ¼ 0–0.43 £
1024 M).

Supramolecular Chemistry
733
Figure 13. IR spectra of free ligand 7 and its complex with Cu2þ chloride recorded in KBr.
freshly distilled tetrahydrofuran (THF). The potentio-
metric selectivity coefficients were determined by the
separate solution method (SSM) according to the
procedure described by Bakker et al. (18) and were
calculated using the EMF values for the highest measured
ion activities that belong to the linear response range for a
given ion.
cations. For all membranes, the electrode slopes for
Pb2þ have been close to the Nernstian value:
28.2 mV dec21 (compound 5), 29.0 mV dec21 (compound
6), 26.4 mV dec21 (compound 7) and 27.8 mV dec21 for
compound 8. Spectroscopic studies revealed that ligands 6
and 7 form complexes with copper(II) perchlorate in
methanol solution. Usually compounds which form stable
complexes with the cation are weak ionophores for that
discriminated one in the ion-selective membrane. Con-
ducted measurements showed worse electrode slopes for
Cu2þ than for Pb2þ: 22.4 mV dec21 (compound 5),
22.2 mV dec21 (compound 6), 28.2 mV dec21 (compound
In preliminary experiments, we investigated the
potentiometric response towards various cations, starting
from the most discriminated. The solution of Co2þ, Zn2þ
,
Ni2þ, Fe2þ, Cu2þ and Pb2þ chlorides was examined
(cM ¼ 1025–1022 M). The ion-selective membrane elec-
trodes doped with compounds 5–8 were selective for Pb2þ
Figure 14. Optimised geometry of 7.
Figure 15. Optimised geometry of 7 Cu2þ complex.

734
A. Pazik and A. Skwierawska
Table 2. Some theoretical parameters of receptor 7 and after
complexation.
Substrates
7 Cu2þ
7 Pb2þ
N1· · ·X
N2· · ·X
N5· · ·X
N6· · ·X
H1· · ·X
H2· · ·X
H5· · ·X
H6· · ·X
N3· · ·X
N4· · ·X
2.0309
2.0395
2.036
2.026
1.467
1.644
2.503
1.637
2.896
2.874
5.004
5.680
2.733
2.744
5.147
4.458
2.178
2.187
4.290
5.229
Figure 16. Optimised geometry of 7 Pb2þ complex.
A comparison of the selectivities of membranes based
on bis-(phenylhydrazono-1H-tetrazol-5-yl-acetonitriles)
derivatives 5–8 with different lengths of polyether chains
indicates that all compounds are lead selective. Moreover,
it can be seen from Table 3 that the incorporation of
sulphur atoms improves lead selectivity. Membranes
doped with compound 8 show higher affinity towards
Pb2þ (log KPb,Cu ¼ 22.0) than membranes with com-
pound 6 (log KPb,Cu ¼ 21.65). Membrane doped with
compounds 5 and 7 is less selective with respect to
Cu2þ. The temporal changes in potentiometric response of
7) and 25.1 mV dec21 for compound 8. In addition, it was
found that the examined electrodes responded towards
other ions (Zn2þ, Ni2þ and Fe2þ) only in the 1024 to
1022 M concentration range, with slopes being nearer to
Nerstian values (22–25 mV dec21). Because of the high
detection limit of electrodes, they were excluded from
further studies and only the characteristics of electrodes
based on compounds 5–8 towards Pb2þ and Cu2þ are
presented in Figure 17.
Figure 17. Potentiometric response of membrane ion-selective electrode for Pb2þ and Cu2þ ions: (a) compound 5; (b) compound 6;
(c) compound 7; (d) compound 8.

Supramolecular Chemistry
735
sulphate, phosphate and acetate have also been studied.
Unfortunately, the examined electrodes did not respond to
the Nernstian slope for those anions.
Table 3. Selectivity coefficients for various interfering ions.
Interfering ion
5
6
7
8
Zn2þ
Ni2þ
Co2þ
Cu2þ
Fe2þ
22.038
21.629
21.906
20.71
23.179
22.72
22.00
21.65
0.14
23.068
22.62
22.382
20.61
20.168
22.067
21.69
20.219
22.05
0.287
Conclusion
20.811
A series of new bis-tetrazole compounds 5–8 containing
aliphatic chains with oxygen and sulphur atoms and with
hydrazone bonds have been obtained. The bis(phenylhy-
drazono-1H-tetrazol-5-yl-acetonitriles) were synthesised
by cycloaddition using 1,1-dicyanohydrazone derivatives
with sodium azide and ammonium chloride. The spectro-
scopic properties of the resulting bis-tetrazoles have been
studied by UV–vis spectroscopy. UV–vis measurements
showed very similar chromogenic abilities for all ligands
towards Cu2þ ions. Furthermore, the compound with shorter
polyether linkers (5 and 6) showed stronger association
constants towards Ni2þ and Zn2þ ions than 7. The obtained
compounds were used as ionophores in ion-selective
electrodes. It was found that they are Pb2þ-selective
ionophores.
electrodes towards Pb2þ and Cu2þ ions presented in
Figure 17 illustrate that electrodes start to show Nerstian
response towards metal cation at relatively low
concentrations.
For further selectivity studies, the potentiometric
measurements were carried out at different pH values
(pH 4–6). Nitrate solution of Cu2þ and Pb2þ was adjusted
with HNO3 to balance the level of pH. The selectivity
coefficients for Pb2þ and Cu2þ in case of ligands 5–8 depend
on pH values. Only at pH 5, the electrode responded towards
Pb2þ and values of slopes were nearer to the Nernstian value:
27.4 mV dec21 (compound5), 29.5 mV dec21 (compound6),
26.6 mV dec21 (compound 7) and 28.5 mV dec21 for
compound 8 (see Figure 18).
Experimental section
The selectivity of electrodes towards various anions,
such as bromide, iodide, chloride, fluoride, nitrate,
General methods
All materials and solvents were of analytical reagent grade.
Thin layer chromatography was done on aluminium plates
1
covered with silica gel 60 F254 (Merck), Germany. H
NMR spectra were taken on Varian, USA instrument at 200
and/or 500 MHz. IR spectra were recorded on Genesis II
FT-IR (Mattson), USA instrument. UV–vis measurements
were carried out with the use of UNICAM UV, England
300 Series spectrophotometer. Elemental analyses were
done on EAGER 200 apparatus. The melting points are
uncorrected. High-molecular weight PVC, KTpClPB, o-
NPOE and THF were purchased from Fluka, Poland. All
aqueous solutions were prepared from salts of analytical
grade using deionised water. All measurements were
carried out at room temperature. Gaussian 03 software was
used for all theoretical calculations (19).
Procedure for synthesis of 1,1-dicyanohydrazones
derivatives (1–4)
Concentrated hydrochloric acid (8.5 ml) was added to a
suspension of respective diamine (7.5 mmol) in water
(20 ml). An ice-cooled solution of sodium nitrite (1.035 g,
0.015 mol) in water (2 ml) was treated with cooled
suspension of hydrochloride and was stirred at 58C for
30 min. The mixture was added quickly to a solution of
malononitrile (0.99 g, 0.015 mol) in a mixture of ethanol
(20 ml) and water (25 ml) containing sodium acetate
(13.95 g, 0.17 mol). The yellow precipitate was filtered off
and purified by recrystallisation using distilled water.
Figure 18. Potential response of membrane ion-selective
electrode for Pb2þ cation at pH 5: (a) compounds 5 and 7; (b)
compounds 6 and 8.

736
A. Pazik and A. Skwierawska
4.4 mmol) in dry DMF (5 ml) was stirred and heated
1,2-Bis[2-(phenylhydrazonodi-
acetonitriles)phenoxy]ethane (1)
at 1208C for 24 h. It was subsequently cooled to room
temperature, the insoluble salts were filtered and the
solvent was evaporated under reduced pressure. The
resulting solution was poured into 50 ml of water and then
was brought to pH 2 using concentrated hydrochloric acid
to give a crude product that was purified by recrystallisa-
tion using distilled water.
Yellow solid; mp 121–1238C; 85% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 4.56 (s, 4H, CH2O), 6.96–7.10
(m, 4H, HAr), 7.21–7.25 (m, 2H, HAr), 7.39–7.44 (m, 2H,
HAr), 10.58 (s, 2H, NH) ppm. IR (KBr): 3270, 3083, 2944,
2227, 2205, 1609, 1596, 1534, 1499, 1448, 1274, 1219,
1162, 1111, 1073, 1051, 929, 747, 658, 577 and 469 cm21
.
Anal. calcd for C20H14N8O2: C 60.30, H 3.53, N 28.13.
Found: C 60.39, H 3.62, N 28.22.
1,2-Bis[2-(phenylhydrazono-1H-tetrazol-5-yl-
acetonitriles)-phenoxy]ethane (5)
Brown solid; mp 203–2078C; 52% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 4.62 (s, 4H, CH2O), 5.08–5.2
(m, 2H, NH), 6.97–7.04 (m, 4H, HAr), 7.23–7.27 (m, 2H,
HAr), 7.38–7.43 (m, 2H, HAr), 12.73 (s, 2H, NH) ppm. IR
(KBr): 3500, 3380, 3265, 3050, 2939, 2221, 1611, 1600,
1522, 1489, 1444, 1274, 1219, 1162, 1110, 1108, 1080,
1045, 980, 774, 650, 550 and 440 cm21. Anal. calcd for
C20H16N14O2: C 49.59, H 3.33, N 40.48. Found: C 49.65,
H 3.39, N 40.33.
1,5-Bis[2-(phenylhydrazonodi-acetonitriles)phenoxy]-3-
oxa-pentane (2)
Yellow solid; mp 134–1378C; 55% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 4.07–4.10 (m, 4H, CH2O),
4.25–4.29 (m, 4H, CH2O), 6.89–6.99 (m, 6H, HAr), 7.37–
7.40 (m, 2H, HAr), 10.61 (s, 2H, NH) ppm. IR (KBr): 3283,
3070, 2936, 2876, 2229, 2211, 1598, 1510, 1480, 1360,
1270, 2257, 1130, 1105, 1042, 915, 753, 651, 604, 571 and
467 cm21. Anal. calcd for C22H18N8O3: C 59.72, H 4.11,
N 25.33. Found: C 59.80, H 4.22, N 25.39.
1,5-Bis[2-(phenylhydrazono-1H-tetrazol-5-yl-
acetonitriles)-phenoxy]-3-oxapentane (6)
1,8-Bis[2-(phenylhydrazonodi-acetonitriles)phenoxy]-3,
6-dioxaoctane (3)
Yellow solid; mp 177–1808C; 83% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 4.05–4.08 (m, 4H, CH2O),
4.24–4.28 (m, 4H, CH2O), 4.98–5.12 (m, 2H, NH), 6.93–
7.0 (m, 6H, HAr), 7.46–7.5 (m, 2H, HAr), 12.84 (s, 2H,
NH) ppm. IR (KBr): 3423, 3296, 3084, 2939, 2865, 2222,
1600, 1550, 1480, 1378, 1268, 1247, 1108, 1100, 1036,
910, 750, 659, 646, 577 and 464 cm21. Anal. calcd for
C22H20N14O3: C 50.00, H 3.81, N 37.10. Found: C 50.09,
H 3.88, N 37.28.
Yellow solid; mp 80–828C; 90% yield. 1H NMR
(500 MHz, CDCl3): d ¼ 3.77 (s, 4H, CH2O), 3.87 (t,
J ¼ 4.30 Hz, 4H, CH2O), 4.24 (t, J ¼ 4.38 Hz, 4H, CH2O),
6.96 (d, J ¼ 8.3 Hz, 2H, HAr), 7.04 (t, J ¼ 7.8 Hz, 2H,
HAr), 7.18 (t, J ¼ 7.8 Hz, 2H, HAr), 7.48 (d, J ¼ 7.8 Hz,
2H, HAr), 10.53 (s, 2H, NH) ppm. IR (KBr): 3490, 3250,
2900, 2233, 2200, 1637, 1615, 1597, 1550, 1490, 1351,
1290, 1228, 1161, 1114, 1060, 950, 930, 748, 677, 603,
574 and 472 cm21. Anal. calcd for C24H22N8O4: C 59.25,
H 4.55, N 23.02. Found: C 59.31, H 4.64, N 23.11.
1,8-Bis[2-(phenylhydrazono-1H-tetrazol-5-yl-
acetonitriles)-phenoxy]-3,6-dioxaoctane (7)
1,5-Bis[2-(phenylhydrazonodi-
acetonitriles)phenyl(thio)]-3-oxapentane (4)
Brown solid; mp 132–1358C; 70% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 3.70 (s, 4H, CH2O), 3.85 (s,
4H, CH2O), 4.18 (s, 4H, CH2O), 4.90–5.15 (m, 2H, NH),
6.89–7.04 (m, 5H, HAr), 7.51–7.54 (m, 3H, HAr), 12.84 (s,
2H, NH). IR (KBr): 3532, 3450, 3200, 2956, 2221, 1645,
1608, 1600, 1549, 1456, 1440, 1389, 1277, 1237, 1181,
1110, 1108, 1060, 967, 783, 667, 578 and 460 cm21. Anal.
calcd for C24H24N14O4: C 50.35, H 4.23, N 34.25. Found:
C 50.41, H 4.30, N 34.29.
Yellow solid; mp 129–1308C; 72% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 3.02–3.06 (m, 4H, CH2S),
3.41–3.47 (m, CH2O), 7.22–7.25 (m, 2H, HAr), 7.36–7.42
(m, 4H, HAr), 7.53–7.57 (m, 2H, HAr), 10.77 (s, 2H, NH)
ppm. IR (KBr): 3188, 2923, 2225, 2209, 1580, 1520, 1420,
1314, 1276, 1232, 1191, 1075, 1039, 871, 798, 760, 667,
605, 579, 541, 465 and 414 cm21. Anal. calcd for
C22H18N8OS2: C 55.68, H 3.82, N 23.60, S 13.52. Found:
C 55.74, H 3.89, N 23.71, S 13.49.
1,5-Bis[2-(phenylhydrazono-1H-tetrazol-5-yl-
acetonitriles)-phenyl(thio)]-3-oxapentane (8)
Yellow solid; mp 108–1108C; 88% yield. 1H NMR
(200 MHz, d-DMSO): d ¼ 3.04 (t, J ¼ 6.22 Hz, 4H,
CH2S), 3.47 (t, J ¼ 6.21 Hz, 4H, CH2O), 3.88–4.01
Procedure for synthesis of bis(phenylhydrazono-1H-
tetrazol-5-yl-acetonitriles) (5–8)
A mixture of 1,1-dicyanohydrazone (1 mmol), sodium
azide (0.28 g, 4.4 mmol) and ammonium chloride (0.23 g,

Supramolecular Chemistry
Acknowledgement
737
(m, 2H, NH), 7.24 (d, J ¼ 7.53 Hz, 2H, HAr), 7.38–7.47
(m, 4H, HAr), 7.55 (d, J ¼ 7.61 Hz, 2H, HAr), 12.05 (s, 2H,
NH) ppm. IR (KBr): 3407, 3220, 3155, 2923, 2225, 2209,
1600, 1540, 1520, 1440, 1307, 1268, 1222, 1191, 1080,
1045, 870, 788, 755, 667, 579, 543, 457 and 410 cm21
Financial support of this work from Gdansk University of
Technology, Grant Nos BW 014694/038 and BW 014694/039, is
kindly acknowledged.
.
Anal. calcd for C22H20N14OS2: C 47.13, H 3.60, N 34.98,
S 11.44. Found: C 47.22, H 3.64, N 34.85, S 11.49.
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Spectrophotometric studies of metal cation complexation
All reagents and solvents were of the highest commercial
quality and were used without further purification.
Zn(ClO4)2·6H2O, Cu(ClO4)2·6H2O, Ni(ClO4)2·6H2O,
Pb(ClO4)2·6H2O, CoCl2, CuCl2, NiCl2, ZnCl2, Cl2-
Fe·4H2O and PbCl2 were purchased from Aldrich and
dried under vacuum. UV–vis titration was carried out by
addition of metal ion to the bis(phenylhydrazono-1H-
tetrazol-5-yl-acetonitriles) solution. Titrations were car-
ried out in 1-cm path length quartz cuvette keeping the
volume of the ligand solution constant (2 ml). Titration
step 0.01 ml.