Conductometric and UV–Visible Spectroscopic Studies on Association in Dilute Aqueous Solutions of Dq2Fe(CN)6

Abstract

Electrical conductivities and electronic absorption spectra of Dq 2 Fe(CN) 6 (where Dq 2? is diquat, the N,N 0 -ethylene-2,2 0 -bipyridine cation) were measured in dilute solutions in water. Experimental data were interpreted in terms of a molecular model which includes the presence of 1:1 and 2:1 associates. Initially, electrical conductivities and absorption spectra were treated using the Quint-Viallard conductivity equations and modified Hemmes algorithm in a limited concentration range, when only minor 2:1 complex formation is expected. The thermodynamic association constant of the 1:1 complex (K 1 = 17,800 ± 1800 dm 3 Ámol -1 ) and the corresponding contact distance (r min = 5.31 ± 0.07 Å ) were evaluated from the spectral data. Analysis of the conductivity data resulted in K 1 = 16,500 ± 1500 dm 3 Ámol -1 (r min = 5.38 ± 0.07 Å ). Both contact distances were found to agree with the FeÁÁÁN distances in crystalline DqH 2 Fe(CN) 6 Á4H 2 O and Dq 2 Fe(CN) 6 Á6H 2 O. This agreement allowed us to use the same r min value to estimate the association constant of the 2:1 complex in accordance to the Fuoss-Krauss theory. Both K 1 and K 2 were used to calculate electrical conductivities and optical absorbancies in the concentration range up to 5 mmolÁdm -3 . Satisfactory agreement was achieved between calculated and experimental data.

Supramolecular networks derived from hexacyanoferrates and nitrogen heterocyclic cations

“…[22] There are three more such anions in crystal lattices with organic non-protonated cations. [31,32] At this point we can say that a few factors that govern the resulting solid state formulations between cyanoferrates and protonated nitrogen heterocycles are emerging from the present study. i) In all cases were the planar cations maintain their planarity (1, 4, 7, 8) they are parallel to each other in the crystal, forming occasionally stacking interactions.…”

Physicochemical Particular Qualities of the Crystallization Process of Inorganic Heat-Storage Materials’ Melts

“…A rising of temperature leads to an increase in the number of interactions between water molecules and a decrease in the proportion of tetrahedrally coordinated solvent molecules. The process of ion association in systems is enhanced on heating [24]. It is also known that the first sphere of metal and anion ions is completely filled with water molecules in the equilibrium high-water crystalline hydrates.…”