Showing papers on "15-Crown-5 published in 1978"
TL;DR: In this article, the interaction of several sulfur derivatives of crown-3, crown-4 and crown-6 was studied by a calorimetric titration procedure, showing that the partial substitution of sulfur for oxygen in the crown-5 and Crown-6 ligands results in little change in the affinity of the ligand for Tl + and Pb 2+, but greatly increased affinity for Ag + and Hg 2+.
62 citations
TL;DR: There appears to be no cumulative effect of daily ingestion of small amounts of the compounds over a 2-week period, and a general trend of increasing toxicity with increasing ring size and water solubility.
47 citations
TL;DR: In this article, the 1:1 and 4:3 complexes with 2 have been synthesized and characterized and all the isolated complexes are solvent free, and the spectroscopic properties (IR. and electronic spectra, fluorescence lifetimes) of the complexes and the low magnetic moments of the Ln(III) ions in the complexes with Ln = Ce-Eu are indicative of a strong interaction between the lanthanoid ions and the crown ethers 1 and 2.
Abstract: Complexes of lanthanoid trinitrates Ln(NO3)3 with 15-crown-5 ether 1 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and with 18-crown-6 ether 2 (Ln = La, Ce, Pr, Nd) having a 1:1 stoichiometry as well as 4:3 complexes with 2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. All the isolated complexes are solvent free. At 170–220° the 1:1 complexes of 2 are quantitatively transformed into 4:3 complexes. X-Ray powder diagrams of the neodymium complexes with 2 indicate that both the 1:1 and 4:3 complexes are genuine compounds. All the 1:1 complexes show a characteristic IR. absorption band at 875–880 cm−1 absent from both the spectra of the free ligands and of the 4:3 complexes.
The spectroscopic properties (IR. and electronic spectra, fluorescence lifetimes) of the complexes and the low magnetic moments of the Ln(III) ions in the complexes with Ln = Ce-Eu are indicative of a strong interaction between the lanthanoid ions and the crown ethers 1 and 2.
44 citations
40 citations
TL;DR: Raman spectra of liquid or crystalline alkali metal complexes (1:1) of 18crown-6 and 15crown -5 are characterized by a polarized band of high intensity near 865-870 cm−1 as discussed by the authors.
Abstract: Raman spectra of liquid or crystalline alkali metal complexes (1:1) of 18-crown-6 and 15-crown-5 are characterized by a polarized band of high intensity near 865–870 cm−1. Raman spectra indicate the “freezing in” of conformations of crown ethers to a highly symmetric ones on complex formation.
32 citations
TL;DR: The crystal structures of the three title complexes of "benzo-15-crown-5" with Mg[NCS]2, Ca[NCCS]2·MeOH, and Ca[ NCS] 2·H2O have been determined by direct methods from diffractometer data collected with molybdenum radiation as discussed by the authors.
Abstract: The crystal structures of the three title complexes of ‘benzo-15-crown-5’ with Mg[NCS]2, Ca[NCS]2·MeOH, and Ca[NCS]2·H2O have been determined by direct methods from diffractometer data collected with molybdenum radiation. The magnesium complex crystallises in the orthorhombic space group Pbca with cell dimensions a= 16.399(3), b= 25.784(5), c= 9.230(3)A, and z= 8. The structure has been refined to R 0.064 for 1 022 observations. The co-ordination of the cation is a pentagonal bipyramid with the nitrogen atoms of the anions in axial positions. The methanol complex with calcium isothiocyanate crystallises in the triclinic space group P, with cell dimensions a= 8.665(2), b= 11.155(2), c= 11.942(3)Aα= 95.49(1),β= 102.21 (2). γ= 102.47(2)°, and Z= 2. The final R factor is 0.081 for 4 244 observations. The calcium ion has irregular eight-co-ordination which includes the five ether oxygens, the two isothiocyanate nitrogens, and the oxygen atom of the methanol molecule. The analogous water complex crystallises in the monoclinic space group P21/c with cell dimensions a= 11.248(5), b= 12.929(7), c= 17.100(7)A, β= 123.15(2)°, and Z= 4. The final R factor is 0.048 for 704 observations. The co-ordination of the cation is identical with that of the methanol complex with the water oxygen replacing the methanol oxygen atom. The same conformation for the crown ether is found in both the calcium complexes, indicating that intramolecular, not intermolecular or packing, forces decide the conformation.
27 citations
TL;DR: In this article, the rates of complexation-decomplexation of the 15crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) and 18crown -6 (1.4, 7, 10,13,16-hexaoxacyCLooctadecANE) complexes of the aqueous cations Sr(2+), Ba(2+, Pb(2+) and Hg(2)+ have been determined from ultrasonic absorption measurements covering the 15-205 MHz frequency range
Abstract: : The rates of complexation-decomplexation of the 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) complexes of the aqueous cations Sr(2+), Ba(2+), Pb(2+), and Hg(2+) have been determined from ultrasonic absorption measurements covering the 15-205 MHz frequency range at 25 degree. As in the case of previously reported studies of complexation of monovalent cations by these crown ethers, the data have been fitted to a two-step mechanism. Diffusion has been ruled out as the rate limiting step in the complexation. Loss of coordinated water from the ions is proposed as the rate determining step. (Author)
20 citations
TL;DR: In this article, a TANOL derivative of benzo-15crown-5 was synthesized, and the complex formation between the spin labeled crown ether and the alkali metal isocyanate was studied by ESR technique.
Abstract: A TANOL derivative of benzo-15-crown-5 shown in the Fig. 1, was synthesized, and the complex formation between the spin labeled crown ether and the alkali metal isocyanate was studied by ESR technique. The potassium complex revealed a strong spin–spin interaction due to formation of the sandwiched dimer and the structure was investigated on the basis of the ESR parameters of the triplet cluster.
15 citations
1 citations