Cation concentration and local ligand field of polyether–salt complexes

Abstract

Theoretical approaches to quantitative structureactivity relationship (QSAR) analysis of M1muscarinic receptor ligand complexes AIP Conf.Direct structural characterization of charge localization in metal to ligand charge transfer complexes AIP Conf. Proc. 172, 688 (1988); 10.1063/1.37523Multiphoton ioniztion of metal βdiketonates and metal tetraphenylporphyrin complexes: Ligand dissociation vs. molecular ionization AIP Conf.Picturing the ion-chain local configuration of polyether-salt materials as forming oxygen-lined helical turns, with the cation located within the polymer cavity, the local environment of each cation is described in terms of a first coordination shell, characterized by the cation and by its nearest oxygen ligands. The interaction energy between nearest shells, ⑀, for the eutectic concentration of europium-based poly͑ethylene oxide͒, PEO, electrolytes, is calculated by two separate processes: One relating the empirical value of the nearest-ligands local-field energy with the variation of Eu 3ϩ concentration, n, and the other involving a two-electron polarization potential. This last procedure, besides determining the minimum intershells distance for the eutectic phase, permits the number of Eu 3ϩ -nearest oxygens to be fixed. The value obtained by the first procedure was ⑀ϭ554.2 cm Ϫ1 ; while by the second, were ⑀ϭ520.3 cm Ϫ1 , for 10 nearest oxygens, and ⑀ϭ572.4 cm Ϫ1 , for 11 oxygens, for a mean radius of the first coordination shell Rϭ2.4 Å and a minimum distance between nearest shells R 0 ϭ5.3 Å. This model of chains of interacting coordination shells is extended to other polyether-salt complexes modified by mono and divalent cations. The corresponding two-electron interaction potential is calculated for a few monovalent-based crystalline PEO, complexes, while for noncrystalline divalent electrolytes only an upper limit is estimated.

White light emission ofEu3+-based hybrid xerogels

“…We notice that the increase of the tendency of the first ligands to bond covalently to the metal ion in POE-and POP-based electrolytes with 100уnу20 may be induced by an increase in the number of Eu 3ϩ first ligands or in their effective charge. This is entirely compatible with the results found for the coordination number in POE-and POP-based electrolytes which point out a number of first neighbors around 10-11 for nϭ12, 23 whereas in the ureasil hybrids this number is observed for samples with much lower salt concentration, n у60. On the other hand, the hypothesis of a lower average cation first ligands distance, which, as we have mentioned in Sec.…”

“…60 In this context, we note that the predicted 5 D 0 → 7 F 0 energy shift derived from Eq. ͑2͒ for POE 12 EuBr 3 , in which the coordination number was estimated based on two independent methods as 10-11 ether oxygens, 23 agrees, also, very well with the experimental values. The observed result is Ϫ105.8 cm Ϫ1 and the predicted one is Ϫ105.6 cm Ϫ1 , for ten nearest ligands.…”

“…6,[8][9][10][11][12]22,24 In particular, for POE electrolytes incorporating EuBr 3 the observed emission energies have previously been used for determining the average Eu 3ϩ nearest ligands distance, 16,19 the associated local symmetry group, 15,19 and the number of nearest oxygens. 23 Moreover, for these europium-based polymer electrolytes a structural model of chains of interacting coordination shells ͑characterized by the luminescent center and by its nearest ligands oxygens͒ was derived, allowing the determination of the interaction energy between adjacent coordination shells. 23 The narrow room-temperature luminescence characteristic of this encapsulation of lanthanide centers into the oxygenlined helical turns of POE combined with the advantages of processable ionically plastic films of variable thickness and large surface areas, opens up new areas of possible technological applications for these materials.…”

“…23 Moreover, for these europium-based polymer electrolytes a structural model of chains of interacting coordination shells ͑characterized by the luminescent center and by its nearest ligands oxygens͒ was derived, allowing the determination of the interaction energy between adjacent coordination shells. 23 The narrow room-temperature luminescence characteristic of this encapsulation of lanthanide centers into the oxygenlined helical turns of POE combined with the advantages of processable ionically plastic films of variable thickness and large surface areas, opens up new areas of possible technological applications for these materials. 25 On the other hand, the synthesis of these lanthanide-based polymer electrolytes is in accordance with the new trends in the field of luminescent materials where ligands protecting organic cage-type hosts kinetically inerts, e.g., macrocyclic ligands such as, for instance, cyclams, crown ethers, and cryptands, are used as efficient lanthanide coordinated sites.…”

“…Both vibrational and electronic spectroscopic techniques are relevant tools for gaining some insight about the structural molecular characteristics of those amorphous regions. These techniques have been frequently used in various polymer-salt complexes to investigate several aspects of their molecular characteristics, such as, for instance, the conformation of the polymer chains, [5][6][7] the anionic and cationic environments, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] the vibrational modes of polymer-cation coordination, [9][10][11]24 and ether oxygen-metal ion stretching motions. 10,11,22 In the case of polymer electrolytes incorporating lan-thanide salts, since the first initial reports indicating that trivalent cations were also soluble in POE and poly͑oxypro-pylene͒, POP, 13,14 several papers have been published during this decade showing that the ion-polymer chain interactions can be investigated using the cation emission features, [14][15][16][17][18][19][20][21][22][23][24] and the active vibrational modes of the anions.…”