Volume and compressibility changes on mixing solutions of alkali halides/sodium acetate with sodium salt of butyric acid at 298.15 K: Understanding like charge ionic (anion–anion) interactions in water

Anion⋯anion (MX3−)2 dimers (M = Zn, Cd, Hg; X = Cl, Br, I) in different environments

“…2 In comparison to cation-cation contacts, less data is available concerning the analogous anion-anion complexes. Such anion-anion interactions have been observed recently by Ganatra et al 10 in ionic liquids composed of mixtures of alkali halides/sodium acetate with sodium salt of butyric acid. The presence of anion-anion interactions was rationalized therein as the hydrophobic interaction between non-polar moieties (of high polarizability) which constitute the anions.…”

“…The presence of anion-anion interactions was rationalized therein as the hydrophobic interaction between non-polar moieties (of high polarizability) which constitute the anions. 10 Theoretical simulations of Miranda and co-workers treated the anionanion interactions between aspartate dimers. 11 Complexes studied there had positive interaction energies in the gas phase but these quantities turned negative in aqueous solution due to hydration of the monomers which considerably reduced the anion-anion repulsion.…”

Experimental and theoretical evidence of attractive interactions between dianions: [PdCl4]2−⋯[PdCl4]2−

“…Although π-hole bonds between anions have not been observed previously for the Pd family, we were encouraged in this idea by earlier observations in ionic liquids 24 or between anions in aspartate dimers. 25 More closely related are anion–anion complexes 26–33 that involve the Zn family, alkaline earth metals, and triel, pnicogen, and aerogen atoms.…”