Neutral acyclic analogues of crown-ethers and cryptands and their complex-forming properties

Abstract

The origins of the dielectric anomalies associated with the Jahn-Teller phase transitions in DyV0, and DyAsO, are examined in detail. The lowest, nearly degenerate, Dy electronic levels couple strongly to distortions that carry an electric dipole moment parallel to the tetragonal axis. The electric susceptibility as a function of temperature, xc, accordingly shows Curie-like behaviour above TD and a prominent cusp at the phase transition. In the perpendicular direction the electric dipole moments are negligible, and xo, xb have a temperature dependence similar to that of the order parameter. In sensitive experiments x. and x b are observed to differ in magnitude and temperature dependence, suggesting a non-linear dependence on order parameter. Analysis shows that the principal contribution to xa, x b comes from matrix elements of the electric dipole operator between the ground doublets and excited crystal-field levels. These Van Vleck contributions lead to a temperature dependence both linear and quadratic in the order parameter in good agreement with experimental results. IntroductionD y V 0 4 and DyAsO, undergo cooperative Jahn-Teller phase transitions near 14 K from tetragonal (Dii) to orthorhombic (Dii) symmetry (Elliott et af 1972, Gehring and Gehring 1975, Kasten 1980, Page et af 1984. The order parameter is a B,, bulk strain, and has been measured directly by x-ray diffraction (Gobel and Will 1972a, b).The lowest Dy electronic levels are two Kramers doublets which are nearly degenerate above TD. These levels have finite couplings to distortions transforming according to the B1, B2 and E representations of the D2,, Dy site symmetry. It is of interest to note that the distortion which actually occurs, BZ, transforms like z , and that the E distortion transforms like x , y . This implies that the Dy electronic levels couple to electric fields E, and E,, E,. and hence that electric susceptibility measurements parallel and perpendicular to the tetragonal axis ( z I/ c) can provide information on the interactions and the phase transition.Measurements of xc on D y V 0 4 and DyAs04 (Unoki and Sakudo 1977, Harley and Taylor 1978, Page et a1 1979, 1984 showed a prominent dielectric anomaly indicating antiferroelectric (zone-centre) ordering at TD. On the other hand, electric susceptibility measurements perpendicular to the tetragonal axis showed negligible basal plane electric dipole moments. xu and X b were found to change substantially below T,, with Ax,, and AXb apparently proportional to the order parameter. In a recent detailed investigation (Page ef a1 1984, hereafter referred to as PTS), it was found that AX,, and AXb differed 0022-3719/85/173285 + 12 $02.25

Synthesis and Ionophoric Properties of α,ω-Diphosphorylated Aza Podands: II. Kabachnik-Fields Reaction as a Method for Design of α,ω-Diphosphorylated Aza Podands and Their Use for Determination of Metal Ions

“…According to published data, the most sensitive to alkali and alkaline-earth metal cations among neutral carriers used in ion-selective electrodes are oligoethers with the low-polarity amido and amino terminal groups [3,4], as well as natural antibiotics, such as nigericin, monensin, and valinomicin [13]. One of the most important factors controlling the selectivity of ion-selective electrodes is compliance of the structure of the carrier to coordination demands of the ion.…”

“…Podands with donor terminal groups hold much promise in this respect [2]. Of them the most extensively studied are oligoethers with amino and amido terminal groups [3], that have found wide application as components of ion-selective electrodes for metal cations [4,5]. Considerable recent attention has been attracted to podands with phosphine oxide and phosphonate terminal groups, as potent complex-forming agents for alkali metal cations and effective neutral carriers and extractants for rare-earth metals [439].…”

Ionic optodes: role in fiber optic chemical sensor technology

“…However, in the past few years, bulk sensors 30 have been developed for sensing ionic species with a method similar to that used with ionselective electrodes. These optical sensors use the ionophores 31,57,58 designed for electrodes to transport ions from the aqueous phase into a plasticized 59 polymer matrix that contains the transducer dye. The dye is not covalently bound but maintained in the matrix because of its insolubility in water.…”

“In Silico” Design of New Uranyl Extractants Based on Phosphoryl-Containing Podands: QSPR Studies, Generation and Screening of Virtual Combinatorial Library, and Experimental Tests

“…10 Variation of the length of the spacers, of molecular topology, and of the substituents at the phosphorus atoms may lead to desirable complexation [11][12][13] or extraction [14][15][16][17] properties of podands for selected metal cations. In particular, these molecules extract the uranyl cation forming 1:1 complexes 15 whose structures were not studied so far.…”