Novel diamides of 2,2′-dipyridyl-6,6′-dicarboxylic acid: Synthesis, coordination properties, and possibilities of use in electrochemical sensors and liquid extraction

Article abstract of DOI:10.1007/s11172-012-0124-4

The procedure was proposed for the synthesis of various dipyridyldiamides. Their various properties in the series of rare-earth elements were studied. The possibility to use the synthe-sized compounds in polymer membranes of electrochemical sensors for th

Full text of DOI:10.1007/s11172-012-0124-4

Russian Chemical Bulletin, International Edition, Vol. 61, No. 4, pp. 881—890, April, 2012
881
Novel diamides of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid:
synthesis, coordination properties, and possibilities of use
in electrochemical sensors and liquid extraction
D. O. Kirsanov,a N. E. Borisova,b M. D. Reshetova,b A. V. Ivanov,b L. A. Korotkov,b I. I. Eliseev,c
M. Yu. Alyapyshev,c I. G. Spiridonov,a A. V. Legin,a Yu. G. Vlasov,a and V. A. Babainc
aDepartment of Chemistry, Saint Petersburg State University,
Mendeleev Center, 7/9 Universitetskaya nab., 199034 Saint Petersburg, Russian Federation.
Fax: +7 (812) 328 2835. Eꢀmail: d.kirsanov@gmail.com
bDepartment of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie gory, 119899 Moscow, Russian Federation
cV. G. Khlopin Radium Institute,
28 2ꢀi Murinskii pr., 194223 Saint Petersburg, Russian Federation
The procedure was proposed for the synthesis of various dipyridyldiamides. Their various
properties in the series of rareꢀearth elements were studied. The possibility to use the syntheꢀ
sized compounds in polymer membranes of electrochemical sensors for the development of
novel types of sensors was shown. A comparison of the influence of the ligand structure on the
extraction and sensor characteristics was performed.
Key words: diamides of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid, chemical sensors, liquid
extraction.
The separation of actinides (americium, curium) from
the fission products , e.g., rareꢀearth elements from lanꢀ
thanum to terbium, is one of the most difficult chemical
problems in the fractionation processes of radioactive
waste. The known methods of separation by complexones
(TALSPEAK or SETFISC processes)1,2 do not provide
the complete separation of actinides from lanthanides; in
addition, solutions with a larger content of salts are used.
The most attractive candidates for separation are polyꢀ
dentate nitrogenꢀcontaining extracting agents.3,4 These
compounds are highly selective towards actinides as comꢀ
pared to lanthanides (in some cases, the separation coeffiꢀ
cients in the americium—europium pair exceed 100). Unꢀ
fortunately, the extracting agents proposed to date are not
often appropriate for technological use because of low solꢀ
ubility, low chemical stability, or the loss of the extraction
ability in an acidic medium.
membranes of potentiometric sensors, which makes it
possible to obtain ionꢀselective electrodes with a high senꢀ
sitivity to various metals.9
In this work, we describe the synthesis, coordination
properties, and use of novel derivatives of diamides of 2,2´ꢀdiꢀ
pyridylꢀ6,6´ꢀdicarboxylic acid of diverse structure in liquid
extraction and in polymer membranes for the developꢀ
ment of new electrochemical sensors.
Synthesis of the studied compounds
The synthesis of studied compounds 1—8 (Table 1)
can be divided into three stages: synthesis of the stating
acids, synthesis of various substituted amines, and acylaꢀ
tion of amines by diacids or their derivatives.
Therefore, search for novel, more efficient compounds
is being actively continued.5,6 One of the directions in this
search is the study of amides of heterocyclic acids, which
are attractive due to the relative simplicity of the syntheꢀ
sis. It has earlier been shown that diamides of 2,6ꢀpyrꢀ
idinedicarboxylic acid7 preferably extract americium with
an americium—europium separation coefficient of ~8.
Diamides of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid8 are
more selective to americium. In addition to good extracꢀ
tion properties, these compounds can be used in polymer
The synthesis of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid
from 2ꢀaminoꢀ6ꢀmethylpyridine has previously been deꢀ
scribed.9 Since the direct introduction of acceptor substitꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 0875—0885, April, 2012.
1066ꢀ5285/12/6104ꢀ0881 © 2012 Springer Science+Business Media, Inc.

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Kirsanov et al.
Table 1. Structures of compounds 1—8
ring can increase the acidity of the compounds in nitric
acid media used in extraction and, therefore, we do not
consider them in this work.
Product
Х
R
R´
A set of commercially available amines (dibutylamine,
dioctylamine, and Nꢀethylaniline) was used as an amine
The results obtained for Nꢀethylaniline diamide prompted
us to study analogous compounds substituted in the aroꢀ
matic ring. As these anilines, we synthesized mꢀ and
pꢀfluoroꢀNꢀethylanilines and pꢀhexylꢀNꢀethylaniline.
The available fluoroanilines were successfully alkylatꢀ
ed by triethyl orthoformate followed by the acidic hydrolꢀ
ysis of the formed formyl derivative (Scheme 2).
1
2
3
4
5
6
7
8
H
H
H
Br
H
H
H
Br
Ph
nꢀBu
nꢀOct
Et
nꢀBu
nꢀOct
Et
Et
Et
Ph
3ꢀFC6H4
4ꢀFC6H4
4ꢀ(nꢀC6H13)C6H4
4ꢀ(nꢀC6H13)C6H4
Et
Et
The selective nitration of 4ꢀhexylbenzene has been deꢀ
scribed10,11; however, the solidꢀphase catalysts used do
not allow one to prepare 4ꢀhexylbenzene in sufficient
amounts. It is impossible to nitrate hexylbenzene by stanꢀ
dard nitrating mixtures with high selectivity and, hence,
initially it was assumed to separate the formed mixture of
orthoꢀ and paraꢀisomers at the stage of acetanilides, using
the low solubility of 4ꢀhexylacetanilide in saturated hydroꢀ
carbons (Scheme 3).
uents into the pyridine ring is hindered, the synthesis of
4,4´ꢀdisubstituted 2,2´ꢀdipyridyls requires the preliminary
preparation of 2,2´ꢀdipyridyl diꢀN,N´ꢀoxides to facilitate
the electrophilic substitution in the pyridine ring. We proꢀ
posed synthetic Scheme 1 for the synthesis of 4,4´ꢀdibroꢀ
moꢀ6,6´ꢀdimethylꢀ2,2´ꢀdipyridyl (9).
Substituted 6,6´ꢀdimethylꢀ2,2´ꢀdipyridyl 9 was oxiꢀ
dized to 4,4´ꢀdibromoꢀ2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic
acid (13) by analogy to unsubstituted 6,6´ꢀdimethylꢀ2,2´ꢀ
dipyridyl, and target acid 13 was obtained in high yield.
The introduction of donor substituents into the pyridine
In addition to the necessity of isomer separation,
a serious drawback of this method is the formation of
a considerable amount of 2ꢀhexylaniline. The threeꢀstage
Scheme 1
Scheme 2

Novel diamides of dipiridyldicarboxylic acid
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
883
Scheme 3
method including the synthesis of 4ꢀhexylacetophenone
16, the Schmidt rearrangement, and the reduction of the
formed 4ꢀhexylacetanilide 17 with lithium alumohydride
is free of these disadvantages (Scheme 4).
The reaction of rareꢀearth element nitrates with the
amides (Scheme 6) was studied for model ligand 1 conꢀ
taining the phenyl and ethyl substituents at the nitrogen
atom of the amide group.
The complexes are formed by reflux of a mixture of the
ligand and corresponding inorganic salt for 6 h. The synꢀ
thesized REE complexes are poorly soluble in acetonitrile,
and the solubility decreases with an increase in the atomic
number of the element. The data of IR spectroscopy
show that the coordination of metal ions in the complexes
is the same: the metal is arranged in the compounds in
the pseudoꢀplane of the ligand formed by the nitrogen
atoms of the dipyridyl fragment and amide groups. The
oxygen atoms of the amide groups are involved in the
coordination of the metal ion along with the nitrogen
atoms of dipyridyl. This is indicated by the decrease in
the frequency of stretching vibrations of the amide I
band from 1639 cm–1 in free ligand 1 to 1610 cm–1 in
the complexes due to the formation of a fiveꢀmemꢀ
bered quasiꢀaromatic metallocycle, including, in addition
to the metal ion, the nitrogen atom of dipyridyl and
the oxygen atom of the amide group. The vibration freꢀ
quency of the amide group decreases due to some equalꢀ
ization of the bond lengths in this cycle. In addition, the
IR spectrum exhibits vibrations of the nitrate ion coorꢀ
dinated with the metal ion. The band of stretching N=O
vibrations of the NO3 anion is observed for all complexꢀ
es at 1464 and 1469 cm–1. According to the data of
MALDIꢀTOF mass spectrometry, the spectrum of each
complex contains only one peak corresponding to the fragꢀ
mentation cation formed upon the loss of one nitrate ion
by the complex.
Scheme 4
The total yield of the target compound obtained by this
scheme is 55%.
To synthesize the studied diamides, we tested various
procedures of amine acylation using 1ꢀhydroxybenzotriꢀ
azole or carbonyldiimidazole derivatives for activation.
However, the low conversion of the acids makes these
methods lowly efficient. The most successful method was
the application of acid dichlorides obtained by the interꢀ
action of the starting acids with thionyl chloride and used
without isolation (Scheme 5).
Scheme 5

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Kirsanov et al.
Table 2. Chemical shifts of the protons of ligand 1 and its complexes with lanthanum, europium, and lutetium
Compound
CH3
CH2
CH5´ꢀPy
CHPh
CH4´ꢀPy
CH3´ꢀPy
1
1.18 (t)
1.26 (t)
–0.27 (br.t)
1.29 (t)
3.93 (q)
4.09 (q)
2.34 (br.s)
4.10 (q)
7.03—7.32 (m)
7.74 (t)
7.80 (t)
5.29 (br.s)
7.90 (t)
7.57 (d)
8.19 (d)
3.64 (br.d)
8.30 (d)
1 La(NO3)3
1 Eu(NO3)3
1 Lu(NO3)3
6.99 (d)
3.42 (br.d)
6.85 (d)
7.31—7.53 (m)
7.39 (br.s)
7.38—7.45 (m)
7.48—7.58
Scheme 6
stituents at the amide nitrogen atom: 1 and 2. The extracꢀ
tion ability of the diamide towards actinides and lanꢀ
thanides was studied and the principal possibility of using
diamides of this type for the separation of Am from rareꢀ
earth elements (separation coefficient ~10) was shown.
However, the solubility of 1 and 2 was very low: 0.03 and
0.1 М, respectively, which did not allow one to attain high
values of distribution coefficients.9 It should be mentioned
that diamide 2 characterized by a higher solubility has
a lower extraction ability than 1. As for diamides of dipiꢀ
colinic acid, the effect of aryl strengthening is fulfilled for
diamides of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid. The diꢀ
amides bearing both aryl and alkyl substituents at the amide
nitrogen atom have a higher extraction ability that the
diamides with alkyl substituents only. A series of eight
diamides was synthesized in order to improve the extracꢀ
tion and physical properties of this class of extracting
agents. Taking into account the earlier obtained data,9 the
structure of the diamide in which one of the substituents at
the amide nitrogen atom is ethyl and another is substitutꢀ
ed phenyl was taken as a basis. The bromide substituent
was also introduced into the pyridine ring to determine the
influence of an acceptor in the pyridine ring on the extracꢀ
tion ability and sensitivity and selectivity of metal deterꢀ
mination in the membrane.
i. Ln(NO3)3•6H2O, CH3CN, .
The structures of the synthesized complexes were adꢀ
ditionally confirmed by the NMR spectral data. Accordꢀ
ing to the data of Н NMR spectra (Table 2), the comꢀ
1
plexes have a similar symmetric structure, due to which
the type and multiplicity of all main signals in their specꢀ
tra coincide. Compared to the spectra of ligand 1, a downꢀ
field shift of the protons of the pyridine ring and protons of
the phenyl ring of the amide substituent is observed. The
maximum shift is observed for the protons of the pyridine
ring in positions 3 and 4, which is associated with the
coordination of the metal ion to the nitrogen atom of the
pyridine rings. The shift of the proton in position 5 of the
pyridine ring is weak compared to other signals of the
pyridine ring because of the influence of the phenyl subꢀ
stituent in the amide group.
The data on the maximum solubility of diamides of
2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid in Fꢀ3 are listed in
Table 3. Compounds 3 and 5 are very poorly soluble, which
can be explained by steric hindrances. In the case of comꢀ
pound 3, the long alkyl substituents prevent the free spaꢀ
Table 3. Maximum solubility of the diamides
in metaꢀnitrobenzotrifluoride
Diamide
Maximum solubility/mol L–1
Study of the extraction ability
It is known that the extraction ability of the diamide
extracting agents depends, to a great extent, on two facꢀ
tors: the type of the solvent used12 and the structure of the
diamide itself.13 The polar fluorinated solvent was used:
metaꢀnitrobenzotrifluoride (Fꢀ3). Solvents of this type
make it possible to provide high distribution coefficients
for extracted metals. We have earlier studied two diamides
of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid differing by subꢀ
1
2
3
4
5
6
7
8
~0.03
~0.10
<0.01
~0.05
<0.01
>0.05
>0.05 (~0.1)
>0.05

Novel diamides of dipiridyldicarboxylic acid
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885
D
Electrochemical sensors based on dipyridyldiamides
Am
To study the sensitivity of the developed sensors, we
carried out potentiometric measurements with these senꢀ
sors in REE solutions: lanthanum, cerium, praseodymium,
neodymium, samarium, europium, gadolinium, and ytꢀ
terbium in an acidic medium at pH 2. The results are given
in Fig. 2. The sensors based on diamides 4, 7, and 8 have
no significant sensitivity to the cations studied. The senꢀ
sors based on compounds 1 and 6 is a series of REE soluꢀ
tions demonstrate the sensitivity close to the Nernst sensiꢀ
tivity (19.7 mV dec–1), and the sensitivity to heavy lanꢀ
thanides (gadolinium, ytterbium) is 5—10 mV dec–1 lowꢀ
er than that to lighter lanthanides. This fact agrees well
with the data obtained in liquid extraction,9 and the distriꢀ
bution coefficients for the REE of the beginning of the
series are about 300 and decrease to 50 with an increase in
the atomic number of the extracted metal.
It was shown that, similarly to the dependence obꢀ
served for extraction, the introduction of acceptor substitꢀ
uents (bromine) into the pyridine ring results in a sharp
decrease in the sensitivity towards lanthanides. The deꢀ
crease in the sensitivity of lanthanide determination for 7
does not correspond to the increase in the extraction abilꢀ
ity observed for extraction. Perhaps, the alkyl substituents
in the paraꢀposition of the phenyl rings in the composition
of the polymer sensor membrane favor the formation of
a more ordered structure.
1
0.1
Eu
0.01
1
2
4
6
7
8
Fig. 1. Distribution coefficients (D) of metals vs diamide strucꢀ
ture. Extraction from 5 М HNO3, 0.05 М diamide 2—8 in Fꢀ3
(0.03 М 1 in Fꢀ3) as an extracting agent.
tial rotation of the molecule about the С—С axis. In the case
of compound 5, the fluoride substituent in the metaꢀposiꢀ
tion sharply decreased the solubility of this compound.
The comparative data on the extraction of americium
and europium from a solution of 5 М nitric acid for diꢀ
amides of different structure are presented in Fig. 1. The
introduction of the additional substituent into the pyrꢀ
idine ring of the diamide decreases the extraction ability of
the diamide compared to the extracted metals, which is
clearly seen by the comparison of two pairs of diamides
1/4 and 7/8. The introduction of the long alkyl radical
into position 4 of aniline increases the distribution coefꢀ
ficients.
Thus, all studied compounds, regardless of the strucꢀ
ture, extract americium better than europium. The sepaꢀ
ration coefficients for the studied compounds reach values
of ~10, which allows one to use these extracting agents for
the selective extraction of actinides from acidic solutions.
The logarithms of selectivity coefficients of the sensors
towards REE cations are presented in Fig. 3. As a whole,
the developed sensors have a low selectivity in the series of
REE and possess a high cross sensitivity (especially 1 and 6),
/mV dec–1
La
Ce
Pr
Nd
Sm
Eu
Gd
Yb
15
10
5
0
1
2
6
7
4
8
Fig. 2. Electrode sensitivity () of the sensors to rareꢀearth metal cations in their aqueous solutions at fixed values of pH of the
medium (pH 2).

886
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
Kirsanov et al.
log(KLa/Ln
)
Ce
Pr
Nd
Sm
Eu
Gd
Yb
0.6
0.4
0.2
0
1
2
6
–0.2
Fig. 3. Logarithms of selectivity coefficients logKLa/Ln of the sensors to the REM cations in nitric acid solutions at pH = 2 and pLa = 3
estimated by the method of biionic potentials.
layer chromatography was carried out on Merck Silica gel
60 F256 and Merck Aluminium Oxide F256 neutral plates. Colꢀ
umn chromatography was carried out on silica gel (Merck,
70—230 mesh).
All solvents were purified by standard procedures prior
to used.
and the sensors based on 2 are predominantly more selecꢀ
tive towards lanthanum cations.
The pH dependence of the potential of the sensors was
studied in the range from 2 to 12 pH units. When pH of the
measured solution changed in the indicated range, the
potential of the first five types of the sensors decreased by
at most 200 mV on all the studied range, which indicates
an insignificant influence of the pH on the potential of the
sensors. The decrease started at the pH of the solution
higher than 6, whereas the potential remained almost unꢀ
changed under the conditions of lower pH. The decrease
in the potential of the sensor based on 8 in the pH range
from 2 to 6 was close to the decrease in the hydrogen
electrode potential, indicating the strong pH dependence
of this sensor.
Thus, we proposed the procedure for the synthesis of
diamides of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid with varꢀ
ious substituents on the amide nitrogen atoms. Using IR
and NMR spectroscopy, we studied the processes of comꢀ
plex formation of these compounds with lanthanides. It
was shown that the oxygen atoms of the amide groups
participate in coordination. The synthesized dipyridylꢀ
amides can successfully be used in liquid extraction for the
selective extraction of actinides from acidic solutions. The
incorporation of the synthesized ligands into the polymer
plasticized membranes makes it possible to obtain chemiꢀ
cal sensors with the expressed sensitivity to lanthanide
cations in acidic aqueous solutions.
6,6´ꢀDimethylꢀ2,2´ꢀdipyridyl diꢀN,N´ꢀoxide (10). A threeꢀ
necked 250ꢀmL flask equipped with a stirrer and a thermometer
was loaded with glacial acetic acid (70 mL, 1.2 mol) and 6,6´ꢀdiꢀ
methylꢀ2,2´ꢀdipyridyl (19.5 g, 0.106 mol), which dissolved within
10 min with vigorous stirring. The temperature of obtained soluꢀ
tion was brought to 70 С, a 50% solution of H2O2 (20 mL,
0.35 mol) was added, and the mixture was stirred for 7 h at
a specified temperature. The reaction mixture was cooled to
~20 C. After 12 h, 250 mL of water were poured in two manipuꢀ
lations (by portions of 150 and 100 mL), and the solvent was
evaporated on a waterꢀjet pump to 70—80 mL. Then a saturated
solution of potassium carbonate (100 g in 100 mL of water) was
poured to the obtained liquid. The floated insoluble substance
was filtered off and washed with small portions of chloroform.
A light yellow powder was obtained in a yield of 21.5 g (93.9%),
1
m.p. 181—182 С. Н NMR (CDCl3), : 2.58 (s, 6 Н); 7.24
(t, 2 Н, J = 7.74 Hz); 7.35 (d, 2 Н, J = 3.79 Hz); 7.37 (d, 2 Н,
J = 2.81 Hz). IR (KBr), /cm–1: 1470—1450.
6,6´ꢀDimethylꢀ4,4´ꢀdinitroꢀ2,2´ꢀdipyridyl diꢀN,N´ꢀoxide
(11). 6,6´ꢀDimethylꢀ2,2´ꢀdipyridyl diꢀNꢀoxide (7.50 g, 0.035 mol)
was introduced into a nitrating mixture obtained from conꢀ
centrated sulfuric (20 mL) and fuming nitric (27 mL) acids.
The obtained solution was stirred for 2 h at 90 С and poured
into ice (200 mL). The reaction mixture was neutralized to pH 6.
The precipitate was filtered off, washed with water and meꢀ
thylene dichloride, and dried in air. The target dinitro comꢀ
pound was obtained as a yellow powder with the temperature of
Experimental
1
decomposition >300 С in a yield of 7.74 g (78%). Н NMR
(DMSOꢀd6), : 2.53 (s, 6 Н); 8.52 (d, 2 Н, J = 3.4 Hz); 8.60 (d, 2 Н,
J = 3.4 Hz).
1
Н NMR spectra were recorded on a Bruker Avanceꢀ400
instrument in (CD3)2SO at ambient temperature. The chemiꢀ
cal shifts are presented in the  scale relative to SiMe4. Thin
4,4´ꢀDibromoꢀ6,6´ꢀdimethylꢀ2,2´ꢀdipyridyl diꢀN,N´ꢀoxide
(12). Compound 11 obtained at the previous stage (30 g, 0.098 mol)

Novel diamides of dipiridyldicarboxylic acid
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
887
was suspended in carbon tetrachloride (300 mL), acetyl bromide
(100 mL) was added, and the mixture was refluxed with stirring
for 4 h. After cooling, the precipitate was filtered off, washed
with a solution of soda and water, and dried in air. The target
dibromide was obtained as a white powder with the temperature
of decomposition >300 С in a yield of 22 g (59%). Н NMR
(DMSOꢀd6), : 2.51 (s, 6 Н); 7.84 (d, 2 Н, J = 1.7 Hz); 7.92
(d, 2 Н, J = 1.7 Hz).
4,4´ꢀDibromoꢀ6,6´ꢀdimethylꢀ2,2´ꢀdipyridyl (9). A mixture of
4,4´ꢀdibromoꢀ6,6´ꢀdimethylꢀ2,2´ꢀdipyridyl diꢀNꢀoxide (20 g,
0.053 mol) and phosphorus tribromide (20 mL) in methylene
dichloride (150 mL) was stirred at ambient temperature for 4 h
and left to stay for 16 h. The solution was poured into ice (300 mL)
and neutralized by the addition of soda until carbon dioxide
stopped evolving. The obtained solution was extracted with meꢀ
thylene dichloride (4×50 mL). The extract was dried over anhyꢀ
drous sodium sulfate. After the solvent was evaporated, the prodꢀ
uct was obtained in a yield of 14.8 g (81%), m.p. 158—160 С.
1Н NMR (CDCl3), : 2.41 (s, 6 Н); 8.48 (d, 2 Н, J = 1.7 Hz);
8.76 (d, 2 Н, J = 1.7 Hz).
4ꢀHexylacetanilide (17). 4ꢀHexylacetophenone (40.8 g,
0.2 mol) was dissolved in acetic acid (200 mL) containing conꢀ
centrated sulfuric acid (50 mL, 92 g) at 60—70 С. Sodium azide
(0.3 mol) was introduced by small portions with vigorous stirring
avoiding too intense dinitrogen evolution (the addition took about
2 h). Stirring was continued for 3 h more under the same condiꢀ
tions. Then the mixture was poured into ice (3 L) and left to
warm to ambient temperature. The precipitate was filtered off
and washed with water containing a small amount of soda to
remove adsorbed acids. A white powder with m.p. 92—92.5 С.
(Ref. 14: 91—92 С) was obtained in a yield of 37.23 g (71%).
1Н NMR (CDCl3), : 0.98 (t, 3 Н, J = 6.7 Hz); 1.29 (m, 6 Н);
1.58 (quint, 2 Н, J = 7.5 Hz); 2.30 (s, 3 Н); 2.55 (t, 2 Н, J = 7.7 Hz);
7.12 (d, 2 Н, J = 8.2 Hz), 7.30 (br.s, 1 Н); 7.39 (d, 2 H, J = 8.2 Hz).
13С NMR (CDCl3), : 14.06, 22.58, 24.51, 28.88, 31.43, 31.70,
35.34, 119.99, 128.81, 135.45, 139.10, 168.20.
4ꢀHexylꢀNꢀethylaniline (18). A solution of 4ꢀhexylacetanilide
(26.2 g, 0.119 mol) in anhydrous tetrahydrofuran (150 mL) was
added on cooling in a water bath and stirring to a suspension of
lithium alumohydride (5.24 g, 0.138 mol) in anhydrous tetraꢀ
hydrofuran (50 mL). After the end of dihydrogen evolution, the
reaction mixture was refluxed for 6 h and left to stay for 16 h.
The reaction mixture was decomposed by the consecutive addiꢀ
tion of water (5.24 mL), a 15% solution of sodium hydroxide
(5.24 mL), and water (3×5.24 mL) with stirring and cooling in
a water bath. The precipitate was filtered off and washed with
tetrahydrofuran (3×30 mL). The solution was dried over anhyꢀ
drous calcium dichloride. Tetrahydrofuran was evaporated, and
the obtained amine was distilled in vacuo collecting the fraction
with b.p. 139—140 С (3 Torr). The target compound was obꢀ
tained as a viscous yellow liquid* in a yield of 22.8 g (93%).
1Н NMR (CDCl3), : 0.87 (t, 3 Н, J = 3.9 Hz); 1.02 (t, 3 Н,
J = 6.9 Hz); 1.28 (m, 4 Н); 1.55 (m, 2 Н); 2.64 (m, 2 Н); 2.90
(t, 2 Н, J = 5.9 Hz); 3.46 (s, 1 H); 3.58 (q, 2 Н, J = 6.9 Hz); 6.38
(d, 2 Н, J = 4.8 Hz); 6.89 (d, 2 Н, J = 4.8 Hz).
Synthesis of diamides 1—8 (general procedure). The starting
acid was refluxed in thionyl chloride (5 mL of SOCl2 per 1 g of
the acid), adding dimethylformamide (0.5 mL) for 2.5 h. Thioꢀ
nyl chloride was removed by distillation, and the remained acid
chloride was dried in a vacuum of a waterꢀjet pump and disꢀ
solved in anhydrous tetrahydrofuran (10 g of THF per 1 g of the
starting acid). The obtained solution was added with stirring in
portions to a mixture of the starting amine taken in an amount of
2.1 equivalents to the acid and in the equal volume with the
amount of triethylamine in anhydrous tetrahydrofuran (10 mL
of THF per 1 g of the amine). After the end of addition, the
obtained mixture was protected from moisture with a calcium
dichloride tube, stirred for 4—5 h at 40—50 С, and left to stay
for 16 h. The equal volume of water was added to the reaction
mixture, and the organic layer was separated. The aqueous fracꢀ
tion was three times extracted with diethyl ether. The combined
organic fractions were washed with water and dried over anhyꢀ
1
4,4´ꢀDibromoꢀ2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid (13).
The starting 4,4´ꢀdibromoꢀ6,6´ꢀdimethylꢀ2,2´ꢀdipyridyl (5 g,
0.015 mol) was dissolved at 50 С in concentrated sulfuric acid
(70 mL), and chromium anhydride (7.5 g, 0.075 mol) was introꢀ
duced by portions, controlling the temperature increase not highꢀ
er than 75 С. The obtained solution was stirred for 2 h at 70 С
and poured into ice (300 mL). The precipitate formed was
filtered off, washed on the filter with water, ethanol, and diꢀ
ethyl ether, and dried in air. The target diacids was obtained
as a white powder in a yield of 4.8 g (80%), m.p. 274—275 С
1
(with decomp.). Н NMR (DMSOꢀd6), : 8.91 (br.s, 2 Н); 8.29
(br.s, 2 Н).
Synthesis of 3ꢀ and 4ꢀfluoroꢀNꢀethylanilines (14 and 15) from
substituted anilines was carried out by analogy to the procedure
for 4ꢀchloroꢀNꢀethylaniline.15 The total yields of the final prodꢀ
ucts were 43% for 3ꢀfluoroꢀNꢀethylaniline (14) and 52% for
4ꢀfluoroꢀNꢀethylaniline (15).
Compound 14, b.p. 130—134 С (25 Torr). 1Н NMR (CDCl3),
: 0.93 (t, 3 Н, J = 7.1 Hz); 2.74 (q, 2 Н, J = 7.1 Hz); 3.43 (br.s,
1 H); 6.11 (br.m, 2 Н), 6.27 (t, 1 Н, J = 8.1 Hz); 6.90 (m, 1 Н).
Compound 15, b.p. 112—114 С (25 Torr). 1Н NMR (CDCl3),
: 0.72 (t, 3 Н, J = 7.3 Hz); 2.52 (q, 2 Н, J = 7.3 Hz); 3.04 (br.s,
1 Н); 6.01 (m, 2 Н), 6.53 (t, 2 Н, J = 6.8 Hz).
4ꢀHexylacetophenone (16). Acetyl chloride (0.22 mol) was
added on cooling with ice and stirring to a suspension of AlCl3
(28 g, 0.23 mol) in CH2Cl2 (100 mL). The resulting solution
was stirred for 15 min. Hexylbenzene (32.4 g, 0.2 mol) was
added on cooling with ice and stirring. The obtained soluꢀ
tion was stirred for 2 h. After the end of stirring, the reacꢀ
tion mixture was poured into a mixture of concentrated hydroꢀ
chloric acid (200 mL) and ice (200 g). The organic fraction was
separated, and the aqueous fraction was extracted with methylꢀ
ene dichloride (2×50 mL). The combined organic extracts were
washed with water and dried over calcium dichloride. The
solvent was removed on a rotary evaporator. The residue was
distilled in vacuo, collecting the fraction with b.p. 130—132 С
(2 Torr). Target acetophenone was obtained in a yield of 33.86 g
* An increase in the amount of the used alumohydride and reꢀ
duced acetanilide does not increase the amount of isolated amine.
This is related, most likely, to the fact that an insoluble layer of
metallized amine and an amide layer poorly soluble in THF are
formed on the lithium alumohydride surface. Therefore, to obꢀ
tain larger amounts of Nꢀethylanilines, it is reasonable to carry
out several parallel reactions with the indicated loads and to
combine the obtained filtrates.
1
(83%). Н NMR (CDCl3), : 0.89 (t, 3 Н, J = 6.6 Hz); 1.37
(m, 4 Н); 1.66 (quint, 4 Н, J = 7.2 Hz); 2.52 (s, 3 Н); 2.81
(t, 2 Н, J = 7.7 Hz); 7.35 (d, 2 Н, J = 8.1 Hz) 7.95 (d, 2 Н,
J = 8.1 Hz).

888
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
Kirsanov et al.
drous sodium sulfate. After the solvents were evaporated, the
reaction mixture was treated depending on the amine used.
(1) Amides obtained from aliphatic diamines (dibutylamine,
dioctylamine) or 4ꢀhexylꢀNꢀethylaniline were treated with
hexane. The precipitate formed was filtered off, washed with
hexane. and dried in air.
acetonitrile (1 mL). The mother liquor was evaporated in vacuo
and an additional portion of the complex was filtered off.
N6,N6ꢀDiethylꢀN6´,N6´ꢀdiphenylꢀ[2,2´ꢀdipyridyl]ꢀ6,6´ꢀdiꢀ
carboxamidolanthanum(III) nitrate (1[La(NO3)3]). The yield was
70%. Found (%): C, 43.37; H, 3.43; N, 12.42. C28H26N7O11La.
Calculated (%): C, 43.37; H, 3.38; N, 12.64. IR (KBr), /cm–1
:
(2) Derivatives of Nꢀethylanilines were treated with a miniꢀ
mum amount of ethyl acetate. The precipitate formed was washed
cold ethyl acetate and dried in air.
The yields of the diamides were 65—80%. The spectral charꢀ
acteristics of the diamides are given in Table 4.
Synthesis of lanthanum, europium, and lutetium complexes with
diamide 1. A mixture of lanthanide nitrate hydrate (0.52 mmol)
and ligand 1 (0.52 mol) in anhydrous acetonitrile (80 mL) was
refluxed for 6 h. After cooling to ambient temperature, the preꢀ
cipitate of the complex was filtered off and washed with cold
1610.27, 1571.70, 1494.56, 1463.71, 1428.99, 1294.00. MS, m/z
1
(Irel (%)): 713 [La1(NO3)2]+ (100). H NMR (acetonitrileꢀd3),
: 1.26 (t, 3 H, J = 7.15 Hz); 2.27 (s, 1 H); 4.09 (d, 2 H, J = 7.21 Hz);
6.99 (d, 1 H, J = 7.95 Hz); 7.4 (m, 5 H); 7.80 (t, 1 H, J = 8.01 Hz);
8.19 (d, 1 H, J = 7.82 Hz). 13C NMR (acetonitrileꢀd3), : 11.91,
48.94, 125.77, 128.42, 128.92, 130.23, 131.22, 140.92, 141.88,
151.57, 154.65, 163.45.
N6,N6ꢀDiethylꢀN6´,N6´ꢀdiphenylꢀ[2,2´ꢀdipyridyl]ꢀ6,6´ꢀdiꢀ
carboxamidoeuropium(III) nitrate (1[Eu(NO3)3]). Found (%):
C, 42.81, 42.61; H, 3.30, 3.34; N, 12.27, 12.31. C28H26N7O11Eu.
Table 4. Spectral characteristics of 2,2´ꢀdipyridylꢀ6,6´ꢀdicarboxylic acid diamides 1—8
Diꢀ Yield
amide (%)
1Н NMR
IR, /cm–1
Found
Calculated
Empirical
formula
(%)
Aromatic region
Aliphatic region
(C=O) (C=N)
C
H
N
1
2
79 7.62 (t, 3 Н, J = 7.32); 4.02 (q, 2 Н, J = 6.97);
7.12 (br.m, 5 Н) 1.24 (t, 3 Н, J = 6.97)
80 7.60 (d, 1 Н, J = 7.82); 0.74 (t, 3 Н, J = 7.34);
7.89 (t, 1 Н, J = 7.70); 1.00 (t, 3 Н, J = 7.34);
1639
1640
1576
1571
75.01 6.12 12.58 C28H26N4O2
74.65 5.82 12.44
72.12 9.21 12.23 C28H42N4O2
72.07 9.07 12.01
8.42 (d, 1 Н, J = 7.82)
1.11 (qt, 2 Н, J = 7.34, J = 7.43);
1,44 (qt, 2 Н, J = 7.34, J = 7.43);
1.69 (m, 4 Н); 3.36 (t, 2 Н,
J = 7.34); 3.54 (t, 2 Н, J = 7.34)
0.83 (t, 3 Н, J = 7.25);
0.89 (m, 6 Н); 1.27 (m, 17 Н);
1.67 (tt, 2 Н, J = 7.48, J = 7.29);
1.72 (tt, 2 Н, J = 7.68, J = 6.76);
3.36 (t, 2 Н, J = 7.68);
3
4
68 7.57 (d, 1 Н); 7.85 (t,
1 Н); 8.40 (d, 1 Н)
1641
1642
1578
1574
76.54 10.52 8.26
76.47 10.79 8.11
C44H74N4O2
3.50 (t, 2 Н, J = 7.68)
65 7.97 (d, 1 Н, J = 3.02); 4.02 (q, 2 Н, J = 6.85);
7.41 (d, 1 Н, J = 3.02); 1.26 (t, 3 Н, J = 6.85)
7.26 (br.m, 2 Н); 7.14
54.99 4.15 9.52 C28H24Br2N4O2
55.28 3.98 9.21
(br.m, 1 Н); 7.06
(br.m, 2 Н)
5
6
7
8
78 7.67 (m, 3 Н); 7.12 (td, 4.01 (q, 2 Н, J = 7.09);
1 Н, J = 7.95, J = 6.60); 1.28 (t, 3 Н, J = 7.09)
6.89 (d, 1 Н, J = 9.78);
1643
1644
1641
1645
1578
1578
1570
1577
69.14 5.05 12.01 C28H24F2N4O2
69.12 4.97 11.52
6.87 (t, 2 Н, J = 6.60)
67 7.65 (m, 2 Н); 7.57
(br.t, 1 Н, J = 7.15);
7.04 (m, 2 Н); 6.87
(t, 2 Н, J = 7.15)
3.96 (q, 4 Н, J = 7.03);
1.25 (t, 3 Н, J = 7.03)
68.92 5.04 11.87 C28H24F2N4O2
69.12 4.97 11.52
72 7.61 (m, 3 Н); 6.98
(br.m, 4 Н)
3.99 (q, 2 Н, J = 7.05); 2.47
(t, 2 Н, J = 7.83); 1.47 (tt, 2 Н,
J = 6.93, J = 7.09); 1.27 (m, 9 Н);
0.97 (t, 3 Н, J = 6.97)
77.58 8.24 9.19
77.67 8.14 9.05
C40H50N4O2
73 7.73 (d, 1 Н, J = 1.84); 3.97 (q, 2 Н, J = 6.71);
7.35 (d, 1 Н, J = 1.84); 2.41 (t, 2 Н, J = 7.42);
6.94 and 7.02 (АА´ВВ´, 1.41 (tt, 2 Н, J = 6.36,
4 Н, J = 7.77, J = 7.42) J = 5.65); 1.21 (m, 9 Н);
0.84 (t, 3 Н, J = 6.36)
62.03 90.6 7.01 C40H48Br2N4O2
61.86 6.23 7.21

Novel diamides of dipiridyldicarboxylic acid
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 4, April, 2012
889
Calculated (%): C, 42.65; H, 3.32; N, 12.43. MS, m/z (Irel (%)):
727 [Eu1(NO3)2]+ (100), 812 [Eu1(NO3)(PhCHCHCO2H)]+
flat bottom. The beaker was closed with an objectꢀplate and left
to stay to the complete evaporation of THF (~48 h). Discs of
membranes 7 mm in diameter and a thickness of ~0.3 mm were
cut from the obtained films and glued into the body of the
PVC electrode. The glue was a solution of PVC in cyclohexanone.
Eighteen sensors were produced: the membrane of each type
was in three sensors.
Potentiometric measurements were carried out in nitric
acid solutions of REE cations at pH 2 in order to suppress
hydrolysis. The measurements were carried out in the galvanic
cell Cu | Ag | AgCl, KClsat | studied solution | membrane | 0.01 М
NaCl | AgCl | Ag | Cu.
EMF readings were detected on a multichannel electronic digꢀ
ital voltmeter with a high input resistance connected to a personal
computer for data collection and processing. An EVL 1 M 3.1
silver chloride electrode was used as a reference electrode. An
ESL 43ꢀ07 glass electrode was used for monitoring pH of soluꢀ
tions. The both electrodes were produced at the ZIP factory
(Gomel, Belarus). The sensitivity of the sensors was studied
by the calibration method over a series of standard solutions of
an individual ion in the concentration range from 10–7 to
10–3 mol L–1. The sensor sensitivity is determined by the anꢀ
gular coefficient (slope) of the linear region of the electrode
function calculated by least squares (the theoretical value is
19.7 mV dec–1 under normal conditions for threeꢀcharge ions).
The value of the standard electrode potential was obtained by
the extrapolation of the linear region of the calibration depenꢀ
dence to logC = 0. The method of biionic potentials was used to
study the membrane selectivity. The data presented on various
characteristics of the sensors are averaged over three values for
sensors of the same type.
1
(13), 449 [1 – H]+ (20). H NMR (acetonitrileꢀd3), : –0.27
(br.s, 3 H); 2.34 (br.s, 2 H); 3.42 (br.d, 1 H, J = 7.34 Hz);
3.64 (br.d, 1 H, J = 7.83 Hz); 5.29 (br.t, 1 H, J = 7.58 Hz); 7.39
(br.s, 5 H).
N6,N6ꢀDiethylꢀN6´,N6´ꢀdiphenylꢀ[2,2´ꢀdipyridyl]ꢀ6,6´ꢀdiꢀ
carboxamidolutetium(III) nitrate (1[Lu(NO3)3]). The yield was
78%. Found (%): С, 41.67; Н, 3.31; N, 12.15. C28H26N7O11Lu.
Calculated (%): С, 41.44; Н, 3.23; N, 12.08. IR (KBr),
/cm–1: 1612.28, 1583.35, 1571.78, 1510.06, 1494.64, 1463.78,
1452.21, 1307.56, 1297.92, 1290.21. MS, m/z (Irel (%)): 749
[Lu1(NO3)2]+ (100). 1H NMR (acetonitrileꢀd3), : 1.29 (t, 3 H,
J = 7.09 Hz); 4.10 (q, 2 H, J = 7.34 Hz); 6.85 (d, 1 H, J = 7.95 Hz);
7.4 (m, 2 H); 7.52 (m, 3 H); 7.90 (t, 1 H, J = 8.25 Hz); 8.30
(d, 1 H, J = 7.82 Hz). 13C NMR (acetonitrileꢀd3), : 11.81,
50.23, 126.14, 128.84, 130.98, 131.66, 141.46, 144.89, 149.80,
156.57, 173.78.
Study of the solubility and extraction properties of dipyridylꢀ
diamides. The solubility of diamides was measured by the conꢀ
secutive addition of the solvent until an exactly taken weighed
sample of diamide was completely dissolved. Initially the weighed
sample of diamide was taken in such a way that the solution of
a concentration of 0.5 М diamide in metaꢀnitrobenzotrifluoride
would be prepared. Dissolution was carried out at 20 1 C with
vigorous shaking for 1 h. If the taken weighed sample of diaꢀ
mide was not completely dissolved, an additional amount of
the solvent necessary for the preparation of a solution with
a concentration of 0.45 М diamide in Fꢀ3 was added. The proceꢀ
dure was repeated until the complete dissolution of diamide,
decreasing the diamide concentration in the subsequent solution
by 0.05 М.
Experiments on extraction were carried out in 5ꢀmL tubes.
An aqueous phase (1 mL) was introduced into the tube. Soluꢀ
tions of HNO3 of the required concentration (10–5 М Eu(NO3)3)
and the indicator amounts of 152Eu or 241Am were used as an
aqueous phase. Then the extracting agent (1 mL) was added to
the tube. The phases were vigorously stirred for 3 min at 20 2 С
and separated by centrifugation. Samples of the aqueous and
organic phases (0.4 mL) were taken for analysis. The distribution
coefficients of Am and Eu were determined radiometrically usꢀ
ing a DeskTop InSpector 1270 scintillation gamma spectrometer
based on a NaI detector (51×51 mm) with a well (Canberra).
The determination inaccuracy was less than 15%.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 09ꢀ03ꢀ00253_a),
St. Petersburg State University (Grant 12.37.85.2011), the
Ministry of Education and Science of the Russian Federaꢀ
tion, and the Federal Agency on Science and Innovations
(Program "Research and Elaboration on Priority Diꢀ
rections of the Development of Scientific Technologiꢀ
cal Complex of Russia for 2007—2012," State Contract
No. 16.516.11.6075).
References
Production of electrochemical sensors. Polymer sensor memꢀ
branes were produced from polyvinyl chloride (PVC) plasticized
with oꢀnitrophenyl octyl ether (NPOE). Chlorinated cobalt diꢀ
carbollide in the Н+ form (CCD, Katchem, Czechia), which is
applied in liquid extraction as a synergetic additive to polydenꢀ
tate neutral extracting agents for REE extraction, was used as
a cationꢀexchange additive. All components for membrane proꢀ
duction were from Fluka (Switzerland). The PVC content in
all membranes was 33 wt.%. The CCD content was 0.5%. The
ligand content was 50 mmol (kg of membrane)–1 (2.3—3.9 wt.%
depending in the molecular weight). The NPOE content was
varied depending in the composition in the range from 62.6 to
64.2 wt.%.
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Received December 6, 2011;
in revised form March 6, 2012