Propylene solubility is almost 2-fold higher in 1:1 poly(2-ethyl-2-oxazoline) (POZ):AgBF4 or poly(vinyl pyrrolidone) (PVP):AgBF4 than in 1:1 POZ:AgCF3SO3 or 1:1 PVP:AgCF3SO3, according to our previous work. It is confirmed in this paper that the CC stretching band of propylene coordinated with silver cations in 1:1 PVP:AgBF4 is about 2-fold more intense than that in 1:1 PVP:AgCF3SO3. This difference in solubility is investigated here in terms of the differences in the interactions of silver cations with the different anions of the dissolved salts and hence with the carbonyl oxygen atoms of POZ. The strength of interaction between silver cations and carbonyl oxygen, as characterized by the band shift of the complexed CO bands, arises in the order AgBF4 > AgCF3SO3 > AgNO3, whereas the interaction between the cation and anion, as determined by Raman spectroscopy of ion pairing behavior, shows the order AgBF4 < AgCF3SO3 < AgNO3. In addition, these measured differences between the ionic interactions are in agreement with theoretical ab initio calculations of the complexation and bond dissociation energies. It is concluded that AgBF4 polymer electrolytes, with their strong silver cation/carbonyl oxygen and weak silver cation/anion interactions, exhibit more favorable silver cation complexation of propylene molecules, resulting in higher propylene solubility. Interestingly, we also found that when propylene is introduced into silver polymer electrolytes propylene molecules compete with carbonyl oxygen for coordination with silver cations.

Mechanisms of the gas-phase acyl group transfers, Cl- + R(XY)Cl, involving various acyl functional groups, >XY with X = C, S, or P and Y = O or S, are investigated theoretically at the MP2/6-31+G* and B3LYP/6-31+G* levels (additionally with extended basis sets of B3LYP/6-311+G(3df,2p)), and the effects of solvent (ε = 78.5) are calculated with the SCIPCM model at the isodensity level of 0.0004 au. The tetrahedral adducts formed in the carbonyl (RCO) and thiocarbonyl (RCS) group transfers are either transition states (double-well PES) or intermediates (single- or triple-well PES) depending on R, a stronger electron acceptor R favoring the intermediate. However, all of the sulfonyl (RSO2) and phosphoryl ((RO)2PO) transfers proceed with trigonal bipyramid (TBP)-type transition states, in contrast to the stepwise mechanism through TBP-type intermediates for the sulfinyl (RSO) (and sulfonyl transfers between F-) transfers. The most important factor determining whether an adduct in an acyl-group-transfer reaction is the transition state or intermediate is the energy gap between the and orbitals. The possibility of reacting through an intermediate is greater for lower and higher levels. The backside σ-attack pathway is favored over the π-attack pathway only when a low-lying orbital, preferably below the level, is available. In general, the results are in good agreement with those of experiments. The solvent effect elevates the barrier height almost uniformly so that the relative orders of gas-phase activation barriers between different R groups are maintained in solution.

The coordination behavior of silver ions dissolved in a polymer solvent is investigated to elucidate the facilitated transport phenomena in solid-state membranes. Silver polymer electrolyte membranes were prepared by dissolving AgCF3SO3 in poly(2-ethyl-2-oxazoline) (POZ) or poly(N-vinylpyrrolidone) (PVP). The permeance and solubility of propylene in the silver polymer electrolyte increased slowly with silver ion concentration up to the silver mole fraction of 0.25 ([CO]:[Ag] = 3:1), after which the permeance and solubility of propylene abruptly increased. Other properties such as the Bragg d spacing, glass transition temperature (T g), and propane permeance also showed marked changes at a silver mole fraction of 0.25. The existence of this threshold concentration is attributed to the following observations:  (1) the most favorable coordination number for silver ions in polymer electrolytes under a propylene environment is 3, and (2) the coordination bond strength between silver ion and carbonyl oxygen is marginally stronger than that between silver ion and olefin molecule. As a result, it is proposed that silver ions can act as olefin carriers only when they have vacant coordination sites, i.e., only when the coordination number of silver ion for carbonyl oxygens is less than 3. Therefore, the silver ion coordination number is shown to have a strong bearing both on the activity of the silver ion as an olefin carrier and on the structure of polymer electrolytes.