Aqueous Solutions Of KSCN Research Articles

Molecular and Supramolecular Structures of Cd(II) Complexes with Hydralazine-Based Ligands; A New Example for Cyclization of Hydrazonophthalazine to Triazolophthalazine

Molecular and supramolecular structures of two polymeric and one trinuclear Cd(II) complex with hydralazine-type ligands were presented. Self-assembly of E-1-(2-(thiophen-2-ylmethylene)hydrazinyl)phthalazine (HL) and CdCl2 gave the 1D coordination polymer [Cd(H2L)Cl3]n*H2O, 1, in which the Cd(II) ion is hexa-coordinated with one cationic monodentate ligand (H2L+) and five chloride ions, two of them acting as connectors between Cd(II) centers, leading to the formation of a 1D coordination polymer along the a-direction. Using DFT calculations, the cationic ligand (H2L+) could be described as a protonated HL with an extra proton at the hydrazone moiety. Repeating the same reaction by heating under reflux conditions in the presence of 1 mL saturated aqueous KSCN solution, the ligand HL underwent cyclization to the corresponding [1,2,4]triazolo[3,4-a]phthalazine-3(2H)-thione (TPT) followed by the formation of [Cd(TPT)(SCN)2]n*H2O, 2, a 1D coordination polymer. In this complex, the Cd(II) is coordinated with one NS-donor TPT bidentate chelate and two bridged μ(1,3)-thiocyanate ions connecting the Cd(II) centers forming the 1D polymer array along the b-direction. Heating E-2-(1-(2-(phthalazin-1-yl)hydrazono)ethyl)phenol HLOH with CdCl2 under reflux condition gave the trinuclear complex [Cd3(Hydralazine)2(H2O)2Cl6], 3, indicating the hydrolysis of the hydrazonophthalazine ligand HLOH during the course of the reaction. Due to symmetry considerations, there are only two different Cd(II) centers having CdN2Cl3O and CdN2Cl4 coordination environments. Hirshfeld topology analysis was used to analyze the solid-state supramolecular structure of the studied complexes.

Ion Pair Structures in Aqueous KSCN Solution: Classical and Quantum Mechanical/Molecular Mechanical Molecular Dynamics Simulation Study#

Ion pair formation and dissociation are fundamental processes in electrolyte solutions so that understanding thermodynamic stabilities and dynamic aspects of ion pairs is of great importance. The structures of various ion pair states are here studied by carrying out classical and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations of aqueous KSCN solutions. A few different solvent potential models are considered and the resulting ion pair structures are directly compared. In particular, when KSCN is treated quantum mechanically and effective fragment potential (EFP) model for water is used, we found two stable forms of ion pairs that can be considered as contact ion pair (CIP) and solvent separated ion pair (SSIP), where the interionic distances between K+ and SCN − are found to be 4.0 and 5.5 Å, respectively. QM/EFP‐MD further indicates that the nitrogen side of SCN − is preferentially interacting with K+ in CIP. However, the corresponding CIP appears at 3.0 Å interionic distance in fully classical MD simulation at a higher KSCN concentration. Nonetheless, both QM/EFP and classical MD simulation results show that the CIP state appears to be more stable than SSIP. From the site‐site radial distribution functions (RDF) calculated from the QM/MM and classical MD trajectories, detailed ion pair structures and surrounding solvent configurations are further elucidated.

A novel technique to semi-quantitatively study the stability of emulsions and the kinetics of the coalescence under different dynamic conditions

The kinetics of coalescence is studied experimentally using a new technique for tracking the process in the bulk phase. For this aim, aqueous solutions of KSCN (colorless) and FeCl3 (light yellow) are used to make individual W/O emulsions. Any coalescence occurred between drops containing KSCN solution and those containing FeCl3 solution would combine these solutions. This leads to a reddish brown solution due to the formation of iron(III)thiocyanate. The intensity change of this red color with time represents the dynamics of coalescence occurring between drops of different emulsified aqueous droplets. The detector response to any changes in the system is recorded as a function of time. In this study, the effects of different parameters such as the concentration of Span 80 used as emulsifier in individual emulsions, the mixing rate of the emulsion, and the kinetics of coalescence are investigated semi-quantitatively.

Spectroscopic investigation on intermolecular and intramolecular motions of concentrated aqueous KSCN solution

Both intermolecular and intramolecular motions of concentrated aqueous KSCN solution were investigated by means of femtosecond optical heterodyne-detected Raman induced Kerr effect spectroscopy (OHD-RIKES) and Raman spectroscopy. We found that all concentrated aqueous KSCN solutions present significantly large anisotropic hyperpolarizabilities in their femtosecond OHD-RIKES measurements, which is attributed to a 45cm−1 librational motion of SCN−. We also found that the weakening of the 170cm−1 stretching motion of water intermolecular hydrogen bond (HB) by 0.10m (molality) KSCN is equivalent to that by 4.00m KBr in aqueous solution, which implies SCN− strongly distort the HB network of water. Besides, we found that the rotational relaxation time constant of SCN− increases with the increase of KSCN concentration in aqueous solution, which is correlated with the corresponding viscosity of respective aqueous KSCN solution.

Solvation of KSCN in Water

The results of a neutron diffraction experiment performed on aqueous solutions of KSCN are analyzed and discussed in comparison with similar data for KCl and KOH solutions. The effect of the different ions on the structure of water and the differences and similarities among the ion solvation shells are discussed in detail. In particular it is shown that the effect of KSCN on the structure of water is visible as a shift and a broadening of the second peak of the oxygen-oxygen radial distribution function, which corresponds to a lower number of interstitial water molecules, compared to pure water. The hydration shell of the cation is similar to that found in the case of KCl solutions, and more interestingly the hydration shell of SCN- is asymmetric, with water molecules H-bonded to the N site and weakly correlated to the S site. These results provide a reasonable microscopic description of the mechanism for the high efficiency of thiocyanate in crystallizing basic proteins.

Network and thermodynamic properties of hydrogels of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine

Samples of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine] (PSPV) have been synthesized to high conversion by free radical polymerization in aqueous solution of the zwitterionic monomer SPV with several concentrations of the crosslinker N, N′-methylene-bis-acrylamide (MBA). Hydrogels obtained by swelling them in water and aqueous KSCN solution were examined by gravimetric and dimensional analysis, and by compression–strain measurements. The derived effective crosslinking density ν e was only ca. 11% of the theoretical value, indicating low efficiency of chemical crosslinking by MBA. At 298 K increasing content of MBA produces increases in the values of ν e, elastic moduli and polymer–water interaction parameter χ. At a fixed MBA content, increasing temperature led to decreases in the values of ν e, elastic moduli and χ, but an increase in water content of hydrogel. For swelling in aq. KSCN solution the mechanical properties are insensitive to content of salt. Experimental and theoretical analysis afforded values of the water/polymer, salt/water and salt/polymer interaction parameters. Where appropriate the findings are compared with those reported for a different zwitterionic hydrogel and a neutral non-zwitterionic hydrogel.

Observations on the swelling characteristics of the zwitterionic hydrogel of poly(1-3-sulfopropyl)-2-vinyl-pyridinium-betaine hydrogel

Samples of poly[1-(3-sulfopropyl)-2-vinyl-pyridinium-betaine] (PSPV) have been synthesized to high conversion by free radical polymerization in aqueous solution of the zwitterionic monomer SPV with several concentrations of the crosslinker N, N′-methylene-bis-acrylamide (MBA). The densities of the resultant xerogels increased regularly with the content of MBA. Hydrogels obtained by swelling them in water and aqueous KSCN solution were examined by gravimetric and dimensional analysis. The water contents increased with decreasing content of MBA, the value of 92.7 wt% at the lowest MBA content being higher than that for other zwitterionic hydrogels. Enhanced swelling occurred in 1 M aq. KSCN at each MBA content, the total swelling being 98.1 wt% at the lowest crosslinker content. Swelling increased with increasing temperature. An approximate procedure to formulating swelling equilibrium in term of the volume fraction of water in hydrogel, in conjunction with the van’t Hoff equation, yields a small positive value for the enthalpy of swelling. This is compared with values derived similarly for other hydrogels.

Pulse Radiolysis of Aqueous Thiocyanate Solution

The pulse radiolysis of N(2)O saturated aqueous solutions of KSCN was studied under neutral pH conditions. The observed optical absorption spectrum of the SCN(*) radical in solution is more complex than previously reported, but it is in good agreement with that measured in the gas phase. Kinetic traces at 330 and 472 nm corresponding to SCN(*) and (SCN)(2)(*-), respectively, were fit using a Monte Carlo simulation kinetic model. The rate coefficient for the oxidation of SCN(-) ions by OH radicals, an important reaction used in competition kinetics measurements, was found to be (1.4 +/- 0.1) x 10(10) M(-1) s(-1), about 30% higher than the normally accepted value. A detailed discussion of the reaction mechanism is presented.

Behaviour of crosslinked and linear poly[1-(3-sulphopropyl)-2-vinyl-pyridinium-betaine] in aqueous salt solutions

Linear and crosslinked poly[1-(3-sulphopropyl)-2-vinyl-pyridinium-betaine] (PSPV) samples have been prepared by free radical polymerization of the zwitterionic monomer (SPV) in the absence and presence, respectively, of N,N′-methylene-bisacrylamide (MBA). The crosslinked xerogel was swollen to equilibrium at ambient temperature in water and in aqueous solutions of KSCN, KBr and KCl having concentrations ([salt]) extending up to 2 mol dm−3. In aqueous salt the degree of swelling exceeded the value in pure water (0.70), the enhancement in swelling being most marked at low values of [salt]. The content of water within hydrogel increased with salt concentration in swelling medium for low values of [salt] but thereafter fell with further increase in [salt]. In contrast, the salt content within swollen hydrogel displayed a continuous increase with increasing [salt]. The partition coefficient expressing concentration of salt in hydrogel relative to that in swelling medium increased sharply with [salt] at low values, but levelled out to values of 0.8–1.2 at higher values of [salt]. The difference in behaviour among the three salts was not dramatic, but indicated that the affinity of salt for the polymer lay generally in the order KSCN>KBr>KCl. This affinity was confirmed by conductometric determinations of the coefficient of selective adsorption of salt to polymer in solutions of linear PSPV. © 1999 Society of Chemical Industry

Behaviour of crosslinked and linear poly[1‐(3‐sulphopropyl)‐2‐vinyl‐pyridinium‐betaine] in aqueous salt solutions

Linear and crosslinked poly[1-(3-sulphopropyl)-2-vinyl-pyridinium-betaine] (PSPV) samples have been prepared by free radical polymerization of the zwitterionic monomer (SPV) in the absence and presence, respectively, of N,N′-methylene-bisacrylamide (MBA). The crosslinked xerogel was swollen to equilibrium at ambient temperature in water and in aqueous solutions of KSCN, KBr and KCl having concentrations ([salt]) extending up to 2 mol dm−3. In aqueous salt the degree of swelling exceeded the value in pure water (0.70), the enhancement in swelling being most marked at low values of [salt]. The content of water within hydrogel increased with salt concentration in swelling medium for low values of [salt] but thereafter fell with further increase in [salt]. In contrast, the salt content within swollen hydrogel displayed a continuous increase with increasing [salt]. The partition coefficient expressing concentration of salt in hydrogel relative to that in swelling medium increased sharply with [salt] at low values, but levelled out to values of 0.8–1.2 at higher values of [salt]. The difference in behaviour among the three salts was not dramatic, but indicated that the affinity of salt for the polymer lay generally in the order KSCN>KBr>KCl. This affinity was confirmed by conductometric determinations of the coefficient of selective adsorption of salt to polymer in solutions of linear PSPV. © 1999 Society of Chemical Industry

Effect of the TiO2 Surface on the Reactivity of Photocatalytically Generated (SCN)2•- and I2•-

The radical ions (SCN)2•- and I2•- were produced by photocatalytic flash excitation (355 nm) of oxygenated TiO2 sols suspended in 1.00 M aqueous solutions of KSCN or KI. To determine the effect of surface heterogeneity of the photocatalyst on the secondary reactions of these transients, these radical ions were reacted with a series of electron donors. The resulting heterogeneous rate constants are compared to those known for the same reactions in homogeneous solution, where (SCN)2•- and I2•- were generated by pulse radiolysis. Relative to the solution phase, the reaction between (SCN)2•- and ascorbic acid on a TiO2 sol was accelerated by approximately a factor of 40, that between (SCN)2•- and hydroquinone was essentially unchanged, and that between (SCN)2•- and cysteine was slowed by approximately an order of magnitude. The dismutation of (SCN)2•- on TiO2 was accelerated by a factor of 3. The reaction of I2•- with cysteine on a TiO2 sol was approximately 25 times slower than that in solution, and its dism...

Copper(II) thiocyanide complexes extractable with [dibenzo-18-crown-6-K] + in chloroform

CuII can be extracted from aqueous KSCN solutions using 2,3,11,12-dibenzo-1,7,10,13,16-hexaoxacyclooctadiene (di-benzo-18-crown-6) in CHCl3. Raman and i.r. spectroscopies establish that the species present in the organic phase after extraction corresponds to [Cu2OH(SCN)5]-[dibenzo-18-crown-6-K +]2, where the CuII thiocyanide complex and the K+ crown complex are ionically associated.

Vibrational dephasing in aqueous KSCN solution. A memory function and stretched exponential study

Raman spectra of 5.0 and 8.4 M aqueous KSCN solutions were recorded. The spectra were analyzed by memory-function and stretched-exponential modeling procedures. The two procedures modeled the vibrational autocorrelation functions within experimental error. The success of the stretched exponential model was found to be its very good fit to the memory functions.

On the vibrational T2 processes in partially ordered systems

The stretched (‘‘extended’’ or ‘‘fractional’’) exponential, exp{−(t/T)α}, where 0<α≤1 and T (ps) a time constant, is introduced as a modulation function for a vibrational T2 process in order to describe the non-Markovian dynamics of the bath of amorphous systems in the picosecond domain. The theory simulates well published dephasing data of probe oscillators in concentrated aqueous solutions of KSCN, molten mixtures of Li and Rb nitrates, and of polycrystalline and smectic phases of the liquid crystal 4-n-octyloxy-4′-cyanobiphenyl. The temperature and phase dependence of dispersion parameter α follows an accepted model of constrained-sequential relaxation with a scale-invariant (‘‘fractal’’) distribution of relaxation times.

Dynamics of SCN-ions in molten thiocyanates and aqueous solutions by Raman spectroscopy

The Raman spectra of the v 1(CN) stretching mode of SCN- ions have been measured in molten thiocyanates, KSCN and NaSCN, at temperatures 450-600K. The vibrational and the rotational correlation functions are calculated, and the dynamics of SCN- ions in the molten state are compared with those in aqueous solutions of KSCN, NaSCN, and LiSCN at concentrations 1–10 mol dm-3 and at temperatures 303–353 K. The observed vibrational correlation functions are analysed by the stochastic line shape theory of Kubo, in which homogeneous and inhomogeneous broadening are treated simultaneously. Both broadening contributions to the isotropic spectra are extracted. The homogeneous broadening is found to increase with increasing temperature in both melts and aqueous solutions; the inhomogeneous broadening remains constant in molten KSCN while it decreases in aqueous solutions. As the result, the isotropic Raman bandwidth is considered to increase with temperature in the molten state and to decrease in aqueous solutions. Rotational correlation functions of SCN- ions in these molten salts show the behaviour of the short time inertial rotation (t ⪅ 0·15 ps, jump angle 20°), which is a little slower than the free rotation of a single ion. The long time exponential decay of the rotational correlation functions reflects the ultimate diffusional behaviour of the ionic reorientation. The rotational relaxation rate increases with increasing temperature in both melts and aqueous solutions. The vibrational dephasing rate decreases and the rotational relaxation rate increases as the cation size increases in melts. In aqueous solutions, the vibrational dephasing rate follows the same cation dependence as that in melts, while the rotational relaxation rate decreases as the cation size increases. This seems to be a consequence of the specific local structures in aqueous electrolyte solutions.

Molecular characterization of gelatin by light scattering

AbstractIn aqueous KSCN solutions the salt is preferentially desorbed from the domain of gelatin molecules, similarly to synthetic polyelectrolytes. Light‐scattering measurements in gelatin solutions in 0,5 M KSCN and in a single solvent (formamide) show that both solvents are suited for the molecular characterization of gelatin at room temperature. Neglecting the effect of selective sorption in salt solutions does not cause any considerable error in the molar mass determination of gelatin.

Geometrische Isomerie bei bindungsisomeren Hexakis(thiocyanatoisothiocyanato)osmaten(III) / Geometrie Isomerism of Bond Isomerie Hexakis(thiocyanatoisothiocyanato)osmates (III)

Abstract From the system of isomeric complex ions [Os(NCS)n(SCN)6-n]3-, 9 of 10 possible species, n = 1-6, are isolated, including for n = 2, 3, 4 the first representatives of pure geometric bond isomers. By reaction of K2[OsCl6] with aqueous KSCN solution at reflux temperature, trans(mer)-complexes, and on treatment at 60 °C exclusively cis(fac)- complexes are formed. By ion exchange chromatography on diethylaminoethyl-cellulose columns, from mixtures of pairs of geometric isomers the pure trans(mer)-compounds are enriched in front, the cis(fac)-species at the end of the zones. Characterization and assignment of the configuration of the geometric isomers is based upon the reproducible differences in the IR and Raman spectra.