6 Y. Inoue, T. Hakushi, Y. Liu and L. H. Tong, J. Org. Chem., 1993,
58, 5411.
7 H.-J. Buschmann, Inorg. Chim. Acta, 1986, 125, 31.
8 F. Arnaud-Neu, E. M. Collins, M. Deasy, G. Ferguson, S. J. Harris,
B. Kaitner, A. J. Lough, M. A. McKervey, E. Marques, B. L. Ruhl,
M. J. Schwing-Weill and E. M. Seward, J. Am. Chem. Soc., 1989,
111, 8681.
9 Y. Kudo, T. Miyakawa, Y. Takeda, H. Matsuda and K. Hiratani,
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10 V. I. Evreinov, Z. N. Vostroknutova, V. E. Baulin, Z. V. Safronova
and E. N. Tsvetkov, Zh. Neorg. Khim. (Russ.), 1993, 38, 1519.
11 V. P. Solov’ev, V. E. Baulin, N. N. Strakhova and L. V. Govorkova,
Russ. Chem. Bull., 1994, 43, 1493.
12 V. E. Baulin, V. K. Syundyukova and E. N. Tsvetkov, Zh. Obshch.
Khim. (Russ.), 1989, 59, 67.
13 V. E. Baulin, V. K. Syundyukova and E. N. Tsvetkov, Zh. Obshch.
Khim. (Russ.), 1989, 59, 62.
14 A. N. Bovin, A. N. Degtyarev and E. N. Tsvetkov, Zh. Obshch.
Khim. (Russ.), 1987, 57, 1506.
(Fig. 4). Cryptand 2.2.1 (with also seven donor atoms) forms in
acetonitrile very stable complexes with small alkali cations, but
it does not prefer Liϩ (log β = 10.3) over Naϩ (log β > 11.3).70 In
the same solvent, the Liϩ complex of the cryptand 2.1.1 (log
β > 10) is slightly more stable than the Naϩ complex (log
β > 9).71 tert-Butylcalix[4]arenetetraacetate forming 1:1 com-
plexes with alkali cations in MeCN,8 prefers Liϩ (log β = 6.4)
over Naϩ (log β = 5.8), but it does not display a Liϩ/Naϩ select-
ivity [Sel(Liϩ) = 0.80] as high as do P4 and P5 podands.
Small crown ethers2–6,71 and acyclic ionophores with a qui-
nolyl group9 display a high binding affinity toward Liϩ in some
organic solvents and in biphasic water/organic solvent systems,
but they were not studied in acetonitrile and cannot be com-
pared to podands P1–P6, as far as their Liϩ/Naϩ selectivities is
concerned.
Among podands studied so far in acetonitrile (P1–P6 and
I–VII11), P4 and P5 molecules display the highest Liϩ/Naϩ
selectivity.
15 V. E. Baulin, V. I. Evreinov, Z. N. Vostroknutova, N. A.
Bondarenko, V. K. Syundyukova and E. N. Tsvetkov, Russ. Chem.
Bull., 1992, 41, 914.
16 A. N. Bovin, V. I. Evreinov, Z. N. Vostroknutova and E. N.
Tsvetkov, Russ. Chem. Bull., 1989, 38, 2398.
17 A. N. Bovin, A. N. Degtyarev and E. N. Tsvetkov, Zh. Obshch.
Khim. (Russ.), 1987, 57, 82.
Conclusions
This work is devoted to the synthesis, experimental and theor-
etical studies on new ionophores: four tri-podands, one bi-
podand and one mono-podand containing phosphine oxide
terminal groups. Using a calorimetric titration technique we
have determined their stability constants, enthalpies and
entropies of complexation with lithium, sodium and potassium
thiocyanates in acetonitrile at 298 K. It has been found that
in solution, tri-podands form a variety of complexes [(Mϩ)3L,
(Mϩ)2L, MϩL and MϩL2], whereas bi- and mono-podands form
only MϩL complexes with Liϩ and Naϩ, and MϩL and MϩL2
with Kϩ. The formation of poly-nuclear (Mϩ)nL complexes of
tri-podands in solution has been confirmed by electro-spray
mass spectrometry measurements.
It has been shown that the complexation selectivity of
podands varies as a function of their concentration because
of formation of the complexes of different stoichiometries.
At small concentrations of the ligand, the tri-podand P1 with
᎐CH2᎐P(O)Ph2 terminal groups prefers Naϩ, whereas the other
ionophores selectively bind Liϩ. Tri-podand P4 and bi-podand
P5 with R = ᎐C6H4᎐CH2᎐P(O)Ph2 terminal groups display in
acetonitrile the highest Liϩ/Naϩ selectivity compared to any
other podand studied so far. The remarkable complexation selec-
tivities of tri-podands P1 for Naϩ and P4 for Liϩ, surprisingly,
are mostly related to the formation of poly-nuclear (Mϩ)nL
18 A. N. Bovin, V. I. Evreinov, Z. V. Safronova and E. N. Tsvetkov,
Russ. Chem. Bull., 1993, 42, 912.
19 S. G. Dmitrienko, I. V. Pletnev, V. E. Baulin and E. N. Tsvetkov,
J. Anal. Chem. (Russ.), 1994, 49, 724.
20 V. I. Evreinov, Z. N. Vostroknutova, N. A. Bondarenko, V. K.
Syundyukova and E. N. Tsvetkov, Zh. Obshch. Khim. (Russ.), 1989,
59, 73.
21 V. I. Evreinov, Z. N. Vostroknutova, V. E. Baulin, V. K.
Syundyukova and E. N. Tsvetkov, Zh. Obshch. Khim. (Russ.), 1989,
59, 67.
22 V. I. Evreinov, Z. N. Vostroknutova, A. N. Bovin, A. N. Degtyarev
and E. N. Tsvetkov, Izv. Akad. Nauk SSSR, Ser. Khim. (Russ.), 1989,
60.
23 V. I. Evreinov, V. E. Baulin, Z. N. Vostroknutova, N. A.
Bondarenko, V. K. Syundyukova and E. N. Tsvetkov, Russ. Chem.
Bull., 1989, 38, 1828.
24 V. I. Evreinov, E. N. Tsvetkov, V. K. Syundyukova, Z. N.
Vostroknutova, V. E. Baulin and N. A. Bondarenko, Zh. Obshch.
Khim. (Russ.), 1989, 59, 67.
25 V. I. Evreinov, V. E. Baulin, Z. N. Vostroknutova, V. K.
Syundyukova and E. N. Tsvetkov, Zh. Obshch. Khim. (Russ.), 1989,
59, 73.
26 V. I. Evreinov, V. E. Baulin, Z. N. Vostroknutova and E. N.
Tsvetkov, Russ. Chem. Bull., 1993, 42, 472.
27 V. I. Evreinov, V. E. Baulin, Z. N. Vostroknutova, Z. V. Safronov,
N. A. Bondarenko and E. N. Tsvetkov, Zh. Obshch. Khim. (Russ.),
1995, 65, 223.
28 T. E. Kron, E. I. Sinyavskaya and E. N. Tsvetkov, Russ. Chem. Bull.,
1986, 35, 2241.
29 T. E. Kron and E. N. Tsvetkov, Russ. Chem. Rev., 1990, 59, 283.
30 V. I. Evreinov, V. E. Baulin, Z. N. Vosroknutova, N. A. Bondarenko,
T. K. Syundyukova and E. N. Tsvetkov, Izv. Akad. Nauk SSSR, Ser.
Khim. (Russ.), 1989, 1990.
31 V. I. Evreinov, V. E. Baulin, Z. N. Vostroknutova, Z. V. Sofronova,
I. B. Krachakova, V. K. Syundyukova and E. N. Tsvetkov, Izv. Akad.
Nauk SSSR, Ser. Khim. (Russ.), 1991, 575.
32 V. P. Solov’ev, L. V. Govorkova, O. A. Raevsky, V. E. Baulin, V. K.
Syundyukova and E. N. Tsvetkov, Izv. Akad. Nauk SSSR, Ser.
Khim. (Russ.), 1989, 814.
33 V. P. Solov’ev, L. V. Govorkova, O. A. Raevsky, V. E. Baulin, V. K.
Syundyukova and E. N. Tsvetkov, Izv. Akad. Nauk SSSR, Ser.
Khim. (Russ.), 1991, 575.
34 V. E. Baulin, V. P. Solov’ev, N. N. Strakhova, V. P. Kazachenko and
V. O. Zavelskii, Koord. Khim., Russ., 1996, 22, 253.
35 A. Y. Tsivadze, A. V. Levkin, S. V. Bondareva, V. E. Baulin and E. N.
Tsvetkov, Russ. J. Inorg. Chem., 1991, 36, 1378.
complexes where the P᎐O groups act separately, rather than to
᎐
1:1 complexes with strong cooperativity of binding sites.
Structural studies in the solid and liquid phases (X-ray crys-
tallography and molecular dynamics simulations) highlight the
role of P᎐O containing terminal groups in the cation binding in
᎐
1:1 complexes.
Acknowledgements
This work has been supported by the INTAS-94-3249 grant and
by the International Science Foundation (grant No. MTH000).
We thank Professors D. Feil and R. P. Ozerov for their help with
structural refinements and discussion of the results, and IDRIS
for computer facilities.
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