Isothiocyanate Ion Research Articles

Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes

Protein-protein and protein-salt interactions have been obtained for ovalbumin in solutions of ammonium sulfate and for lysozyme in solutions of ammonium sulfate, sodium chloride, potassium isothiocyanate, and potassium chloride. The two-body interactions between ovalbumin molecules in concentrated ammonium-sulfate solutions can be described by the DLVO potentials plus a potential that accounts for the decrease in free volume available to the protein due to the presence of the salt ions. The interaction between ovalbumin and ammonium sulfate is unfavorable, reflecting the kosmotropic nature of sulfate anions. Lysozyme-lysozyme interactions cannot be described by the above potentials because anion binding to lysozyme alters these interactions. Lysozyme-isothiocyanate complexes are strongly attractive due to electrostatic interactions resulting from bridging by the isothiocyanate ion. Lysozyme-lysozyme interactions in sulfate solutions are more repulsive than expected, possibly resulting from a larger excluded volume of a lysozyme-sulfate bound complex or perhaps, hydration forces between the lysozyme-sulfate complexes.

Polyamine Macrocycles Incorporating a Phenanthroline Unit: Their Synthesis, Basicity, and Cu(II) Coordination

Synthesis and characterization of the two new polyamine macrocycles 2,5,8,11,14-pentaaza[15]-16,29-phenanthrolinophane (L1) and 8-methyl-8-aza-1(1,4),11(1,4)-dipiperazina[15]-16,29-phenanthrolinophane (L2) are reported. Both ligands incorporate a 2,9-phenanthroline unit as integral part of their cyclic structure. L1 contains a pentaamine chain linking the 2,9-phenanthroline positions. L2 contains two piperazine rings within the macrocyclic framework. The basicity constants and the formation constants of their complexes with Cu(II) have been determined by potentiometric measurements in aqueous solution (298.1 K, I = 0.1 mol dm-3). Both L1 and L2 form mono- and binuclear complexes in aqueous solution. In the [CuL1]2+ and [CuL2]2+ complexes, the metal ion is coordinated by the aromatic nitrogens and one or two nitrogens adjacent to the phenanthroline moiety. The remaining polyamine chain is not coordinated. These results are confirmed by the crystal structure of [H2L2Cu(NCS)2](ClO4)2·3H2O (space group P1̄, a = 9.770(10) Å, b = 12.027(5) Å, c = 18.006(7) Å, α = 106.87(3)°, β = 90.22(8)°, γ = 104.48(8)°, V = 1954(2) Å3, Z = 2, R = 0.0971, wR2 = 0.2553). The metal ion is five-coordinated by the phenanthroline nitrogens, by one adjacent amine nitrogen, and by two isothiocyanate ions. The noncoordinated polyamine chain can bind a second Cu(II) ion in aqueous solution, giving binuclear [Cu2L]4+ complexes (L = L1 or L2). In the case of L2, the formation of the binuclear complex leads to piperazine inversion from the chair to the boat conformation, as shown by the crystal structure of [Cu2L2(μ-OH)(H2O)(ClO4)](ClO4)2·2H2O (space group P21/a, a = 19.573(2) Å, b = 9.320(10) Å, c = 21.552(2) Å, β = 108.556(9)°, V = 3727(4) Å3, Z = 4, R = 0.0835, wR2 = 0.2759). This structure displays a piperazine ring unusually bridging two metal cations.

Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes.

Protein-protein and protein-salt interactions have been obtained for ovalbumin in solutions of ammonium sulfate and for lysozyme in solutions of ammonium sulfate, sodium chloride, potassium isothiocyanate, and potassium chloride. The two-body interactions between ovalbumin molecules in concentrated ammonium-sulfate solutions can be described by the DLVO potentials plus a potential that accounts for the decrease in free volume available to the protein due to the presence of the salt ions. The interaction between ovalbumin and ammonium sulfate is unfavorable, reflecting the kosmotropic nature of sulfate anions. Lysozyme-lysozyme interactions cannot be described by the above potentials because anion binding to lysozyme alters these interactions. Lysozyme-isothiocyanate complexes are strongly attractive due to electrostatic interactions resulting from bridging by the isothiocyanate ion. Lysozyme-lysozyme interactions in sulfate solutions are more repulsive than expected, possibly resulting from a larger excluded volume of a lysozyme-sulfate bound complex or perhaps, hydration forces between the lysozyme-sulfate complexes.

Multinuclear Magnetic Resonance Study of Zinc(II) and Cadmium(II) Complexing with Isothiocyanate

A study of zinc(II) and cadmium(II) complexes with isothiocyanate ion has been completed, using a low-temperature, multinuclear magnetic resonance technique that permits the observation of separate resonance signals for bound and free ligand, and Cd(II) metal ion. The Zn2+–NCS− complexes were studied by 1H, 13C, and 15N NMR spectroscopy. In the 1H spectra, the intensity of the coordinated water signal, corresponding to a Zn(II) hydration number of six in the absence of NCS−, decreases dramatically as this anion is added, indicating the complexing process involves more than a simple 1:1 ligand replacement. The 13C and 15N NMR spectra reveal signals for four species, most reasonably assigned to a series of tetrahedrally coordinated Zn2+–NCS− complexes. In the Cd2+–NCS− solution spectra, the 13C and 15N signals for four complexes also are observed and they are three line patterns, corresponding to a doublet from 113Cd J-coupling, and a dominant central peak, resulting from bonding to magnetically inactive Cd isotopes. The 113Cd spectra, showing signals for four complexes, correlate well in all respects with the 13C and 15N results, including coupling in specific cases. The spectral results for both metal ions reflect binding at the nitrogen atom of NCS−, with the complexes changing from an octahedral to a tetrahedral configuration when doing so. Confirming evidence for these conclusions also was provided by several infrared measurements of these metal–ion systems.

A direct hydrogen-1, carbon-13, and nitrogen-15 NMR study of lutetium(III)-isothiocyanate complexation in aqueous solvent mixtures

A direct, low-temperature hydrogen-1, carbon-13, and nitrogen-15 nuclear magnetic resonance study of lutetium(III)-isothiocyanate complex formation in aqueous solvent mixtures has been completed. At −100°C to −120°C in water-acetone-Freon mixtures, ligand exchange is slowed sufficiently to permit the observation of separate1H,13C, and15N NMR signals for coordinated and free water and isothiocyanate ions. In the13C and15N spectra of NCS−, resonance signals for five complexes are observed over the range of concentrations studied. The13C chemical shifts of complexed NCS− varied from −0.5 ppm to −3 ppm from that of free anion. For the same complexes, the15N chemical shifts from free anion were about −11 ppm to −15 ppm. The magnitude and sign of the15N chemical shifts identified the nitrogen atom as the binding site in NCS−. The concentration dependence of the13C and15N signal areas, and estimates of the fraction of anion bound at each NCS−:Lu3+ mole ratio, were consistent with the formation of [(H2O)5Lu(NCS)]2+ through [(H2O)Lu(NCS)5]2−. Although proton and/or ligand exchange and the resulting bulk-coordinated signal overlap prevented accurate hydration number measurements, a good qualitative correlation of the water1H NMR spectral results with those of13C and15N was possible.

Multinuclear magnetic resonance study of aluminum(III)‐isothiocyanate complexes in water‐acetone mixtures

AbstractA multinuclear magnetic resonance (NMR) study of the complexes of aluminum(III) with isothiocyanate ion in water‐acetone mixtures has been completed. At temperatures low enough to slow proton and ligand exchange, separate resonance signals are observed for coordinated and bulk H2O (1H) and NCS− (13C, 15N), and Al3+ (27Al) in each complex. The 1H NMR spectra reveal six sets of signals for the complexes, [Al(H2O)6]3+ through [Al(H2O)(NCS)5]2−, including isomers for three of the species. Signal area measurements show a decrease in the Al3+ hydration number with increasing NCS− concentration, as this anion replaces water in the solvation shell. In the 27Al NMR spectra of these systems, signals for seven complexes, [Al(H2O)6]3+ through [Al(NCS)6]3−, are observed, with chemical shifts increasing by about 6 ppm with each additional NCS−. Although broadened somewhat by the Al(III) quadrupole, the 13C and 15N NMR spectra also reveal coordinated NCS− signals for these complexes, including 27AlN13CS J‐coupling in [Al(NCS)6]3−. Area evaluations of the 15N NMR signals provide an excellent complement to the 1H hydration number data. These NMR results demonstrate that a multinuclear approach to the study of solution complexes can provide detailed structural information about the species being formed.

Synthesis, Magnetic, Spectral and Thermal Studies of Some Lanthanide Nitrate and Isothiocyanate Complexes with 4[N-(4-Dimethylaminobenzylidine)amino] Antipyrine

Abstract A new series of complexes of lanthanide(III) nitrate and isothiocynates with 4[N-(4-dimethylaminobenzylidene)amino]-antipyrine (DABAAP) having the general formula [Ln(DABAAP)2(NO3)3] (where Ln = La, Pr, Nd, Sm, Gd, Tb or Dy) and [Ln (DABAAP)n(NCS)3] (n=2, Ln = La or Pr; n = 3, Ln = Nd, Sm, Gd, Tb, or Dy) have been synthesized and their i.r. and electronic spectra obtained. In these complexes DABAAP acts as a bidentate ligand coordinating through the carbonyl oxygen and azomethine nitrogen atoms. The nitrate ion acts as a bidentate ligand and the isothiocyanate ion is N-coordinating with the lanthanide ion. The probable coordination number of the Ln3+ ion varies among seven, nine and ten. The thermal stability of the complexes have also been studied through t.g. analyses.

A Hydrogen-1, Nitrogen-15, and Yttrium-89 NMR-Study of Yttrium(III)-Isothiocyanate Complexes in Aqueous Solvent Mixtures

Abstract A direct, low-temperature hydrogen-1, nitrogen-15, and yttrium-89 NMR study of inner-shell complex formation between yttrium(III) and isothiocyanate ion in aqueous solvent mixtures has been completed. At −105 to −115°C in water-acetone-Freon 12 mixtures, ligand exchange is slow enough to permit the observation of separate 15 N NMR signals for the mono-, di-, and triisothiocyanato complexes of Y(III), displaced upheld by 14 to 17 ppm from the free anion signal. Coordination to 89 Y is strong enough to produce observable J coupling of about 14 Hz in the 15 N signals. This coupling and an analysis of the magnitude and sign of the 15 N chemical shifts indicate binding occurs at the anion nitrogen atom. Area integrations of these signals indicated an overall total of 2 mol of SCN − complexed per mole of Y(III), with the diisothiocyanate complex dominating even at the highest anion concentrations studied. The 1 H spectra of these solutions revealed multiple coordinated water signals, the areas of which led to Y(III) hydration numbers of six in the absence of SCN − to about four at the highest concentrations of this anion. The 89 Y NMR spectra of these systems also revealed a maximum of three complexes, with signals appearing upheld from that of the free metal ion by 3 to 15 ppm. Preliminary 15 N NMR results are presented for the isothiocyanate complexes of lanthanum(III), lutetium(III), aluminum(III), magnesium(II), and paramagnetic samarium(III).

A direct nitrogen-15 NMR study of praseodymium(III)-nitrate complex formation in aqueous solvent mixtures

A direct, low-temperature nitrogen-15(15N) NMR technique has been applied to the study of inner-shell complex formation between praseodymium(III) and nitrate ion in aqueous solvent mixtures. In water-acetone mixtures at −95°C, ligand exchange is slow enough to permit the observation of15N NMR signals for uncomplexed and coordinated nitrate ion, but satisfactory resolution is obtained only by the addition of Freon-12 to these systems for study at −110 to −115°C. Four coordinated nitrate signals are generally observed and a very small signal for an additional complex, or an isomer of one of the others, appears at the highest nitrate concentrations. Signals for the mono-and dinitrato complexes are unambiguously identified, but with the exception of the trinitrato complex, several possibilities exist for the remaining peaks. To overcome excessive viscosity signal broadening, measurements in methanol and ethanol are possible only with praseodymium trifluoromethanesulfonate (triflate). Coordinated nitrate signals in aqueous and anhydrous methanol are observed only for the mono-and dinitrato species, and signal areas indicate a maximum of two moles of nitrate per Pr(III) are complexed. A third signal is evident in the ethanol solution spectra, and the presence of this higher complex was confirmed by area measurement of the fraction of bound nitrate. The extent of complex formation in these solvent systems is attributed to differences in the dielectric constant. A comparison of the complexing tendencies of Pr(III) to other ions studied by this NMR method suggests the possibility of a coordination number change across the lanthanide series. Preliminary15N NMR results for metal-ion complexes with the isothiocyanate ion are presented.

Synthesis, properties and crystal structure of bis(metiamide)bis(isothiocyanato)nickel(II)

The crystal structure of Ni(metiamide) 2(NCS) 2 was determined by X-ray diffraction methods. Unlike cimetidine, which is a tridentate ligand, metiamide (C 9H 16N 4S 2): N-Methyl-N-[2-{(5-methylimidazol-4-yl)methylthio}ethyl]thiourea (which also possesses three potential donor sites) is bidentate, coordinated to the nickel atom through N(imidazole) and S(thioether) atoms. The S(thiourea) atom does not take part in the coordination; instead, the isothiocyanate ion is coordinated through nitrogen to the metal atom. The nickel atom lies on a centre of symmetry in an elongated octahedral environment: the nitrogen atoms occupy equatorial positions (NiN = 2.04 and 2.06 Å) and S(thioether) atoms occupy apical positions (NiS = 2.58 Å). Individual molecules are linked together by a unique S ⋯ HN hydrogen bond involving the uncoordinated S(thiourea) atom. IR, electronic reflectance and magnetic data are consistent with the structural results.

X-Ray Structures of Molybdenum(V) Tetraphenylporphyrins, MoO(tpp)NCS·CH2Cl2 and MoO(tpp)F

Abstract The molecular structures of the title complexes have been determined by a single-crystal X-ray diffraction method. The crystals of MoO(tpp)NCS·CH2Cl2 (tpp= 5,10,15,20-tetraphenylporphyrinato) and MoO(tpp)F are triclinic and tetragonal respectively. An isothiocyanate ion is coordinated to the central molybdenum atom at an angle of 145° with the Mo–N(NCS) bond through the nitrogen atom. In both complexes, the molybdenum atoms are displaced toward oxo ligands from the 4N plane composed of pyrrole nitrogens.

Synthesis, properties and crystal and molecular structure of isothiocyanato [ N, N-bis(2-hydroxyethyl)glycinato] copper(II) monohydrate

The crystal and molecular structure of the title copper(II) complex was determined by the X-ray diffraction method. The crystal is monoclinic with the space group Cc, Z=4, a= 14.567(2), b= 6.970(1), c = 11.051(2) ) Å, β = 93.67(1)°. Full matrix least-squares refinements have led to a final R value of 0.057 for 1080 reflections. The copper atom is ligated by one carboxylato oxygen atom, two hydroxyl oxygen atoms and one nitrogen atom of the ligand, and one nitrogen atom and one sulfur atom of the isothiocyanate ion. The copper atom is at the center of the typical tetragonal-bipyramidal geometry. One hydroxyl oxygen atom and sulfur atom are at the apical positions and their bond lengths to the copper atom are longer than usual. The other four atoms form a square around the copper atom. The complex forms a one-dimensional polymer chain through the isothiocyanate ion.

The Syntheses, Crystal and Molecular Structures, and Their Thermal Properties of Tetramethylammonium [Octakis(isothiocyanato)lanthanoidates(III)]·benzene (1/2), [(CH3)4N]5[M(NCS)8]·2C6H6 (M=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy)

Abstract The titled series of isomorphous complexes, the first octakis(isothiocyanato) complexes of lanthanoids, were obtained. Their crystals are tetragonal, space group P4nc, Z=2. The cell dimensions of the praseodymium complex, for example, are a=15.871(7), c=11.543(6) Å, U=2908(3) Å3, and Dm=1.29(3), Dx=1.29 g cm−3, μ(MoKα)=11.60 cm−1, with a final R value of 0.069. The metal atom is octa-coordinated by eight isothiocyanate ions in an intermediate geometry between cube and square-antiprism. The benzene included in the praseodymium complex crystals was retained up to 174°C (DTA), and was not removed even after being heated for 12 h at 110°C. In cases of the other isomorphous members, the benzene was removed at lower temperatures, respectively. The isomorphous fluorobenzene adduct was obtained only for the lanthanum complex.

Syntheses, and Crystal and Molecular Structures of Tetraethylammonium [Hexakis(isothiocyanato)lanthanoidates(III)] Including Aromatic Hydrocarbon or Halohydrocarbon: [(C2H5)4N]3[M(NCS)6]·G (M=Er, or Yb; G=Benzene, Fluorobenzene, Toluene, or Chlorobenzene)

Abstract The title new complexes were synthesized and their crystal and molecular structures were determined by the single-crystal X-ray diffraction method. The crystal form of [(C2H5)4N]3[Yb(NCS)6]·(C6H6), for example, is monoclinic, space group P21⁄c, a=19.458(12), b=14.046(6), c=18.288(7) Å, β=91.28(4)°, Z=4, and the final R value obtained was 0.064. The other seven crystals are isomorphous with each other. The central metal atom is in an octahedral hexa-coordination geometry: six nitrogen atoms of isothiocyanate ions are ligated to each metal atom. Each solvent molecule is arranged betweeen each pair of neighboring metal atoms along the [1 \bar1 0] axis in each crystal. The cations are arranged approximately between each pair of metal atoms along the [0 1 1], [0 \bar1 1], and [1 1 0] axes, respectively. They were stable for more than a few weeks at room temperature; however, when heated at about 80–90 °C, their guest molecules were lost.

Crystal structure of barium isothiocyanato(ethylenediaminetetraacetato)cobaltate(III)

Ba[Coedta(NCS)].4H20 has been studied by x-ray diffraction [diffractometer, %MoK~, 2312 reflections, heavy-atom method, anisotropic-isotropic (H) method of least squares (MLS), R = 0.054]. The crystals are monoclinic: a = 11.648, b = 12.670, c = 13.058 ~, ~ = 91.4 ~ ,dcalc = 2.119 g/cm 3, Z = 4, space group P21/n. The coordination polyhedron of Co(III) is a distorted octahedron formed by a deprotonated quinquedentate edta 4ligand (2N + 30) and an isothiocyanate ion (N); one of the acetate groups remains free. The conformation of the complex is E, G/R ++ E, -/R. The Ba 2+ ion is surrounded by five 0 atoms of the edta ligand, three O atoms of water molecules, and an S atom, forming a highly distorted singly-capped square antiprism; the distances are Ba-Oedta 2.642-2.882, Be-OH20 2.790-2.925, Ba-S 3.616 ~. Other distances are

Vibrational study of ionic association in aprotic solvents. 6. Dimerization of lithium, sodium, and potassium isothiocyanate ion pairs in tetrahydrofuran and in 1,3-dioxolane

Vibrational study of ionic association in aprotic solvents. 6. Dimerization of lithium, sodium, and potassium isothiocyanate ion pairs in tetrahydrofuran and in 1,3-dioxolane

Optically active co-ordination compounds. Part XXV. Some reactions of isothiocyanate ion co-ordinated to cobalt(III)

(–)-[Co(en)2(NCS)2]+ has been converted into (–)-[Co(en)2(NH3)2]3+ and also to L-(–)-[Co(en)2(CN)2]+, and all three shown to have the same absolute configuration as that of the cyano-complex. The adducts of (–)-[Co(en)2(NCS)2]+ which form with mercury(II) ion, and the protonated complex which forms in concentrated sulphuric acid have been studied, and their possible structures are discussed in terms of the changes in optical activity brought about in addition complex formation.