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1.
Yasuyuki Takeda Yusuke Mochizuki Yasumasa Matsuzaki Shoichi Katsuta 《Journal of inclusion phenomena and macrocyclic chemistry》2000,37(1-4):179-195
Formation constants of 1 : 1 19-crown-6(19C6) complexes with alkali metal ions weredetermined conductometrically at 25 °Cin acetonitrile(AN), propylene carbonate (PC), methanol, DMF, andDMSO. 19C6 always forms the most stable complex withK+. The selectivity order of 19C6 forheavy alkali metal ions isK+ > Rb+ > Cs+.The selectivity for Na+ varies withthe solvent; that for Li+ is the second lowest(AN, DMSO) or the lowest (PC). Transfer activity coefficients(SH
2 O) of19C6 from water to the nonaqueous solvents (S) weremeasured at 25 °C. The contributions of a methylenegroup and an ether oxygen atom to thelog SH
2 Ovalue of a crown ether wereobtained. The SH
2 Ovalues of the 19C6–alkali metal ion complexes(SH
2 O (ML+)) werecalculated, M+ and L denoting an alkali metal ionand a crown ether, respectively. For AN, PC, andCH3OH, although the M+ ion is more stronglysolvated by water than by AN, PC, or CH3OH, thelog SH
2 O (ML+) islarger than the correspondinglog SH
2 O (L)expect for the case of M+ = Li+.The higher lipophilicity of the19C6 complex ion is attributed to an enforcement ofthe hydrogen-bonded structure of water for the complexion caused by the greatly decreased hydrogen bondingbetween ether oxygen atoms and water uponcomplexation. For DMF and DMSO, thelog SH
2 O (ML+) is also greater thanthe correspondinglog SH
2 O (L).It was concluded from thisfinding that the unexpectedly lowest stability of the19C6 complex ion in water is due to the hydrogenbonding between 19C6 and water. The stabilities and thelog SH
2 Oof 19C6–alkali metal ion complexes were compared with those of 18C6complexes. 相似文献
2.
Yasuyuki Takeda Tokutarō Kimura 《Journal of inclusion phenomena and macrocyclic chemistry》1991,11(2):159-170
Stability constants of 1 : 1 16-crown-5 (16C5)-metal ion complexes were determined in water at 25°C by conductometry and potentiometry with ion-selective electrodes. The selectivity sequences of 16C5 in water for univalent and bivalent metal ions are Ag+ > Na+ Tl+ > K+ and Sr2+ > Ba2+ Pb2+, respectively. The stability of a given 16C5-metal ion complex in water is much lower than might be expected on the basis of the solvation power (i.e. relative solubility of the metal ion) of water for the metal ion. The same tendency is observed for the cases of 15-crown-5 (15C5) -metal ion complexes. Transfer activity coefficients () of 15C5 and 16C5 for tetradecane (TD)/water, TD/methanol, TD/acetonitrile, and propylene carbonate/water systems were determined at 25°C. From these data, contributions of a methylene group and an ether oxygen atom to the log value of a crown ether were then obtained. The values from water to acetonitrile, propylene carbonate, and methanol of 15C5- and 16C5-univalent metal ion complexes
were calculated, s, M+, and L being a solvent, a univalent metal ion, and a crown ether, respectively. The log
value is greater than the corresponding log
value. The log
values are negative. This indicates that, although the M- ions are more soluble in water than in the nonaqueous solvents, when the crown ether forms a complex with the M+ ion, the complex becomes more soluble in the nonaqueous solvents than in water, compared with the free crown ether. It was concluded from this finding that the unexpectedly low stability of the crown ether-M+ complex in water is attributed to strong hydrogen bonding between ether oxygen atoms of the free crown ether and water. 相似文献
3.
《Journal of Coordination Chemistry》2012,65(4):459-468
Stability constants (KML) of 1 : 1 benzo-15-crown-5 (B15C5) complexes with alkali metal ions were conductometrically measured in water at 25°C. Transfer activity coefficients of B15C5 and 15-crown-5 (15C5) from water to polar nonaqueous solvents were determined at 25°C. By using these data and the literature values, transfer activity coefficients of the B15C5 and 15C5 complexes with alkali metal ions from water to the polar nonaqueous solvents were calculated to study the solute-solvent interaction of the crown ether complexes. The stability of the B15C5 complex is lower in water than in any other nonaqueous solvent. The KML value for B15C5 is always smaller than the corresponding K ML value for 15C5. The interaction of the B15C5 or the 15C5 complex with the solvents depends on the alkali metal ion in the crown cavity. All the B15C5 and 15C5 complexes undergo hydrophobic hydration, which is particularly stronger for the B15C5 complexes with Na+ and K+. The unexpectedly lowest stability of the B15C5- or the 15C5-alkali metal ion complex in water among all the solvents is caused by the hydrogen bonding between ether oxygen atoms of uncomplexed B15C5 or 15C5 and water. 相似文献
4.
Zahra Monsef Gholamhossein Rounaghi Ali Sarafraz 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(3-4):321-325
The complexation of Tl+, Pb2+and Cd2+ cations by macrocyclic ligands, aza-18-crown-6 (L1) and dibenzopyridino-18-crown-6 (L2) was studied in some binary mixtures of methanol (MeOH), n-propanol (n-PrOH), nitromethane (NM) and acetonitrile (AN) with dimethylformamide (DMF) at 22 °C using DC (direct current) and differential pulse polarographic techniques (DPP). The stoichiometry and stability constants of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the ligand concentration. In all of the solvent systems, the stability of the resulting 1:1 complexes was found to be L1 > L2. The selectivity order of the L2 ligand for the cations was found to be Pb2+ > Tl+ > Cd2+ and the selectivity of the L1 ligand for Pb2+ ion was greater than that of Tl+ ion. The results show that the stability of the complexes depends on the nature and composition of the mixed solvents. There is an inverse relationship between the stability constants of the complexes and the amount of dimethylformamide in the mixed solvent systems. 相似文献
5.
Kumiko Ohtsu Kazuhiko Ozutsumi 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(3-4):217-224
Heats of solution of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) in acetonitrile, 1,2-dichloroethane, N,N-dimethylformamide, dimethyl sulfoxide, nitromethane, propylene carbonate, pyridine and water were measured at 25 °C and the enthalpies of the transfer of 18-crown-6 from waterto the aprotic solvents were derived. The thermodynamic quantities, G1°, H1° and T S1°, for the formation of the[M(18-crown-6)]+ (M+ = Na+, K+, Rb+, Cs+, NH4
+) complexeswere determined by titration calorimetry in dimethyl sulfoxide containing0.1 mol dm-3 (C2H5)4NClO4 as a constant ionic medium at 25 °C. These thermodynamic quantities suggest that the complexationof 18-crown-6 with the alkali-metal ions mainly reflects the different solvationof 18-crown-6 and also the different degree of solvent structure. 相似文献
6.
Luca Prodi Marco Montalti Jerald S. Bradshaw Reed M. Izatt Paul B. Savage 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):123-127
Luminescent properties of 5-chloro-8-hydroxyquinoline (CHQ) free and appended tothe amines in diaza-18-crown-6 (A218C6) were determined. These propertieswere compared to those of bivalent alkaline earth and post-transition metal ioncomplexes of the appended macrocycle (CHQ-A218C6). The luminescent properties were foundto be pH dependent. In the pH range 3 to 7, CHQ-A218C6 forms luminescent complexes withonly Zn2+ and Cd2+. At higher pH values, luminescent complexes wereformed with Mg2+, Ca2+, Sr2+, and Ba2+. No luminescent complex was formed by Hg2+ over the pH range studied. This lariat macrocycle could findapplication as a chemosensor for several of the metal ions studied. 相似文献
7.
Yasuyuki Takeda Aiko Yasui Shoichi Katsuta 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(3-4):157-164
The constants for overall extraction into various diluents of low dielectric constants (Kex) and aqueous ion-pair formation (KMLA) of dibenzo-18-crown-6 (DB18C6)–sodium and potassium perchlorate 1:1:1 complexes (MLA) were determined at 25°C. The Kex value was analyzed by the four underlying equilibrium constants. The KMLA values were determined by applying our established method to this DB18C6/alkali metal perchlorate extraction system. The KM(DB18C6)A value of the perchlorate is much greater for K+ than for Na+, and is much smaller than that of the picrate. The KMLA value makes a negative contribution to the extractability of DB18C6 for MClO4, whereas the value of the MLA distribution-constant does a major one. The partition behavior of M(DB18C6)ClO4 obeys the regular solution theory. However, the M(DB18C6)ClO4 complexes in the diluent of high dipole moment somewhat undergo the dipole–dipole interaction. DB18C6 always shows high extraction selectivity for KClO4 over NaClO4, which is governed largely by the much greater KMLA value for K+ than for Na+. The K+ extraction-selectivity of DB18C6 over Na+ for perchlorate ions is comparable to that for picrate ions. By comparing this perchlorate system with the picrate one, the anion effects on the extraction-efficiency and -selectivity of DB18C6 for Na+ and K+ was discussed in terms of the fundamental equilibrium constants. 相似文献
8.
H
0 and S
0 values of the complex formation in water of benzo-18-crown-6 (B18C6) with K+, Tl+, and Pb2+ were determined and compared with those of 18-crown-6. The H0 values of B18C6 are negative. The stability in water of the B18C6-metal ion complex at 25°C is governed largely by the magnitude of the H
0 value. The B18C6-metal ion complex is less stable in water than the corresponding 18C6-metal ion complex. This is due largely to a less favorable enthalpic contribution of the B18C6-metal ion complex compared with the corresponding 18C6-metal ion complex. The two aromatic ether oxygen atoms of B18C6 are responsible for the larger H
0 value of the B18C6-metal ion complex compared with the corresponding 18C6-metal ion complex. 相似文献
9.
Mojtaba Shamsipur Javad Zolgharnein 《Journal of inclusion phenomena and macrocyclic chemistry》2001,40(1-2):41-44
The complexation of dibenzopyridino-18-crown-6 with some transition and heavy metal ions in methanol solution at various temperatures was studied by a competitive potentiometric method using a Ag+/Agelectrode system. The stoichiometry and stability of the resulting complexes were computed by the MINIQUAD program. The stability of the resulting complexes varied in the order Ag+ > Pb2+ > Tl+ > Cu2+ > Cd2+ > Zn2+. The enthalpy and entropy of the resulting 1:1 complexeswere evaluated from the temperature dependence of the stability constants.The complexes of all cations were enthalpy-stabilized but entropy-destabilized,except for Ag+ and Pb2+ ions,which were also entropy-stabilized. 相似文献
10.
Yasuyuki Takeda Yusuke Mochizuki Munehiro Tanaka Yoshihiro Kudo Shoichi Katsuta Mikio Ouchi 《Journal of inclusion phenomena and macrocyclic chemistry》1999,33(2):217-231
Formation constants (ML) of 1 : 1 19-crown-6 (19C6) complexes with mono- (M+) and bivalent metal ions (M2+) were determined in water at 25 °C by conductometry. The KML value of 19C6 for M+ and M2+ decreases in the order Rb+ K+ > Tl+ > Na+ = Ag+ > Li+ Cs+ and Pb2+ > Ba2+ > Sr2+ > Cd2+ > Ca2+, respectively. The selectivity for the neighboring alkali metal ions in the periodic table is lower for 19C6 than for 18-crown-6 (18C6) except for the case of Rb+ and Cs+. The same is true for the alkaline earth metal ions. Generally, the KML values of 19C6 with M2+ are greater than those with M+. For Na+ and the ions which are smaller in size than Na+ (Li+, Ca2+, Cd2+), the KML value is larger for 19C6 than for 18C6, but the contrary holds for all the other ions of larger sizes than Na+. The limiting ionic molar conductivity (°) of the 19C6–K+ complex in water at 25 °C was determined to be 43. Although 19C6 is larger than 18C6, the 19C6–K+ complex is much more mobile in water than the 18C6–K+ complex. 相似文献
11.
Osmotic vapor pressure measurements have been carried out for three ternary systems, H2O + 0.2 m 18-crown-6 + LiCl, H2O + 0.2 m 18-crown-6 + NaCl and H2O + 0.2 m 18-crown-6 + KCl at 298.15 K using vapor pressure osmometry. Water activities for each ternary system were measured and used to calculate the activity coefficients of 18-crown-6 (18C6) and its salts following the methodology developed by Robinson and Stokes for isopiestic measurements. In the concentration range studied, it was found that (in NaCl and KCl solutions) there is considerable lowering of activity coefficients of one component in the presence of other solutes that has been attributed to the formation of the complexed 18C6:Na+ (or 18C6:K+) species in solution. The Gibbs energies of transfer of alkali chlorides from water to aqueous 18C6 solutions and that of 18C6 from water to aqueous electrolyte solutions have been calculated. These were further used to evaluate the pair and triplet interaction parameters. The calculation of thermodynamic equilibrium constants using the pair interaction parameter, g
NE (i.e., the nonelectrolyte–electrolyte pair interaction) for the studied complexation of cations yields values which are in good agreement with those reported in literature obtained by using ion-selective potentiometry and calorimetry. The results are discussed in terms of water structural effects, complex formation, and hydrophobic interactions. 相似文献
12.
Gholamhossein Rounaghi Ali Sarafraz Yazdi Zahra Monsef 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(3-4):231-237
The complexes of Tl+, Pb2+ and Cd2+ cations with the macrocyclic ligand, dicyclohexano-18-crown-6\linebreak(DC18C6) were studied in water/methanol (H2+O/MeOH), water/1-propanol (H2+O/1-PrOH), water/acetonitrile (H2+O/AN), water/dimethylformamide (H2+O/DMF), dimethylformamide/acetonitrile (DMF/AN), dimethylformamide/methanol (DMF/MeOH), dimethylformamide/1-propanol (DMF/1-PrOH) and dimethylformamide/nitromethane (DMF/NM) mixed solvents at 22 °C using differential pulse polarography (DPP), square wave polarography and conductometry. In general, the stability of the complexes was found to decrease with increasing concentration of water in aqueous/non-aqueous mixed solvents with an inverse relationship between the stability constants of the complexes and the concentration of DMF in non-aqueous mixed solvents. The results show that the change in stability of DC18C6.Tl+, vs the composition of solvent in DMF/AN and DMF/NM mixed solvents is apparently different from that in DMF/MeOH and DMF/1-PrOH mixed solvents. While the variation of stability constants of the DC18C6.Tl+ and DC18C6.Pb2+ complexes vs the composition of H2+O/AN mixed solvents is monotonic, an anomalous behavior was observed for variations of log Kf vs the composition of H2+O/1-PrOH and H2+O/MeOH mixed solvents. The selectivity order of the DC18C6 ligand for the cations was found to be Pb2+ > Tl+ > Cd2+. 相似文献
13.
A conductance study of the interaction between cobalt, nickel, copper, zinc, cadmium, and lead ions with 1,10-diaza-18-crown-6 in different acetonitrile-dimethylsulfoxide mixtures has been carried out at various temperatures. The formation constants of the resulting 11 complexes were determined from the molar conductance-mole ratio data and found to vary in the order Zn2+2+2+2+2+2+. The enthalpy and entropy of complexation reactions were determined from the temperature dependence of the formation constants. A linear relationship is observed between the log Kf of different complexes and mole fraction of acetonitrile in the solvent mixtures. The TS vs. H plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence of an enthalpy-entropy compensation in the complexation reactions. 相似文献
14.
Mehdi Taghdiri Mohammad Kazem Rofouei Mojtaba Shamsipur 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):181-186
The complexation reactions between dibenzo-24-crown-8 (DB24C8) and K+, Rb+, Cs+ and Tl+ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation
constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data
at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in the
order Tl+ > K+ > Rb+ > Cs+. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation
constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent
mixture. The TΔS° vs. ΔH° plot of all thermodynamic data obtained shows a fairly good linear correlation indicating the existence
of enthalpy–entropy compensation in the complexation reactions. 相似文献
15.
Yasuyuki Takeda Kunio Hashimoto Daisuke Yoshiyama Shoichi Katsuta 《Journal of inclusion phenomena and macrocyclic chemistry》2002,42(3-4):323-331
To quantitatively elucidate the effects of the benzo group on the extraction-selectively and -ability of benzo-15-crown-5 (B15C5)for alkali metal ions, the constants of the overall extraction (Kex), thedistribution for various diluents having low dielectric constants (KD,MLA), and the aqueousion-pair formation (KMLA) of B15C5-alkali metal (Li, Na, K) picrate 1:1:1 complexes (MLA) weredetermined at 25 °C. The partition constants of B15C5were also measured at 25 °C. The log KMLA values for Li+, Na+, and K+ are -0.32 ± 0.22, 2.66 ± 0.19, and 0.71 ± 0.47, respectively. In going from 15-crown-5 (15C5) to B15C5, the benzo group considerably decreasesthe KMLA value for the same alkali metal ion. The distributionbehavior of B15C5 and its 1:1:1 complexes with the alkali metal picrates closely obeys regularsolution theory, omitting chloroform. Molar volumes and solubility parameters of B15C5and the 1:1:1 complexes were determined. For every diluent, the Kex valuefor B15C5 increases in the order Li+ < K+ < Na+. KD,MLA makes anunfavorable contribution to the Na+ extraction-selectivity of B15C5 because of the smallest molar volume of the Na(B15C5)A complex. The Na+ extraction-selectivity of B15C5 is determined completely by much the highest KNa(B15C5)A value.The extraction-ability and -selectivity of B15C5 for the alkali metal picrates are compared with those of 15C5on the basis of the underlying equilibrium constants. 相似文献