Sulfite Ligands Research Articles

PH Driven Hydrothermal Syntheses of Neodymium Sulfites and Mixed Sulfate-Sulfites

A family of four new neodymium(III) compounds containing either sulfite or a mixture of hydrogen-sulfate and sulfite ligands has been hydrothermally synthesized. The low solubility of lanthanide sulfite compounds has, in the past, made the isolation of single-crystalline products difficult. To obtain these phases, sodium sulfite (Na2SO3) and sodium bisulfite (NaHSO3) were employed as both anion sources and pH regulators. The in situ oxidation of sulfite to sulfate was controlled by dictating the pH of the starting solutions with these ligands. Sulfites were found to form at a neutral pH, whereas, when the pH was increased, the oxidation of sulfite to sulfate was observed in the crystalline products. The products discussed herein reveal the pH controlled process of in situ oxidation in these hydrothermal reactions.

Porous capsules with a large number of active sites: nucleation/growth under confined conditions.

This work deals with the generation of large numbers of active sites and with ensuing nucleation/ growth processes on the inside wall of the cavity of porous nanocapsules of the type (pentagon)12(linker)30≡{(Mo(VI))Mo(VI)5}12{Mo(V)2(ligand)}30. A first example refers to sulfur dioxide capture through displacement of acetate ligands, while the grafted sulfite ligands are able to trap {MoO3H}(+) units thereby forming unusual {(O2SO)3MoO3H}(5-) assemblies. A second example relates to the generation of open coordination sites through release of carbon dioxide upon mild acidification of a carbonate-type capsule. When the reaction is performed in the presence of heptamolybdate ions, MoO4(2-) ions enter the cavity where they bind to the inside wall while forming new types of polyoxomolybdate architectures, thereby extending the molybdenum oxide skeleton of the capsule. Parallels can be drawn with Mo-storage proteins and supported MoO3 catalysts, making the results relevant to molybdenum biochemistry and to catalysis.

On equilibria with participation of gold(I) complexes in sulfite-thiocarbamide media

The constants of protonation and sulfite ligand substitution by thiocarbamide for Au(SO3) 2 3− complex were determined. Mixed forms Autu(SO3)− and probably binuclear complex [Au2tu2SO3] were shown to occur in noticeable concentrations in sulfite-thiocarbamide media in addition to Autu 2 + and Au(SO3) 2 3− complex forms.

(Invited) Surface Modification of Wide Band-Gaped Anode of Dye-Sensitized Solar Cells by Ionic Liquid Molecules

Dye-sensitized solar cells have attracted worldwide attention due to its unique properties such as cost effective, temperature insensitive, and with high quantum efficiency under low illuminations. Among all studies, the topic of replacement of commonly used liquid electrolyte solution to reduce solution leakage becomes one of the emerging research focuses. The replacement of solvent of electrolyte solution by ionic liquid is one of the approaches. The reduced leakage by these approaches is expected to realize yet at the expense of reduced solar cell efficiency, due to lowered charge transfer rates in the electrolyte solutions. However, we found that the partial replacement of commonly used electrolyte solution by imidazolium salt solution enhances the solar cell efficiency instead.In this study, we report that the surface treatment of the wide band-gaped anode of titanium oxide by ionic liquid molecules accounts for at least part of the solar cell efficiency enhancement. We found that the imidazole-derived molecules act as barrier for electron-hole premature recombination between photoelectrons transported on the conduction band of anode and the holes in the electrolyte on the anode/electrolyte interface. The significant efficiency enhancement is not necessarily due to increased dye adsorption on anodes, because we can manage a reduced dye adsorption condition while the solar cell still provides enhanced efficiency.The ligand of imidazolium salts plays a very crucial role on the effectiveness of imidazole-derived molecules on the enhancement of solar cell efficiency. The presence of sulfite ligand secures the molecule adhesion on titanium oxide through the sulfite ligand itself.We would like to present the parameters of treatment of such sequence of imidazole and dye adsorption, the use of solvent, dip duration time, and solution concentration. From the interrogation of the experiment results, we can confirm the exact role of imidazole-derived molecules on the enhancement of the solar cell efficiency.

Pulsed electron paramagnetic resonance spectroscopy of (33)S-labeled molybdenum cofactor in catalytically active bioengineered sulfite oxidase.

Molybdenum enzymes contain at least one pyranopterin dithiolate (molybdopterin, MPT) moiety that coordinates Mo through two dithiolate (dithiolene) sulfur atoms. For sulfite oxidase (SO), hyperfine interactions (hfi) and nuclear quadrupole interactions (nqi) of magnetic nuclei (I ≠ 0) near the Mo(V) (d(1)) center have been measured using high-resolution pulsed electron paramagnetic resonance (EPR) methods and interpreted with the help of density functional theory (DFT) calculations. These have provided important insights about the active site structure and the reaction mechanism of the enzyme. However, it has not been possible to use EPR to probe the dithiolene sulfurs directly since naturally abundant (32)S has no nuclear spin (I = 0). Here we describe direct incorporation of (33)S (I = 3/2), the only stable magnetic sulfur isotope, into MPT using controlled in vitro synthesis with purified proteins. The electron spin echo envelope modulation (ESEEM) spectra from (33)S-labeled MPT in this catalytically active SO variant are dominated by the "interdoublet" transition arising from the strong nuclear quadrupole interaction, as also occurs for the (33)S-labeled exchangeable equatorial sulfite ligand [ Klein, E. L., et al. Inorg. Chem. 2012 , 51 , 1408 - 1418 ]. The estimated experimental hfi and nqi parameters for (33)S (aiso = 3 MHz and e(2)Qq/h = 25 MHz) are in good agreement with those predicted by DFT. In addition, the DFT calculations show that the two (33)S atoms are indistinguishable by EPR and reveal a strong intermixing between their out-of-plane pz orbitals and the dxy orbital of Mo(V).

Identity of the Exchangeable Sulfur-Containing Ligand at the Mo(V) Center of R160Q Human Sulfite Oxidase

In our previous study of the fatal R160Q mutant of human sulfite oxidase (hSO) at low pH (Astashkin et al. J. Am. Chem. Soc.2008, 130, 8471-8480), a new Mo(V) species, denoted "species 1", was observed at low pH values. Species 1 was ascribed to a six-coordinate Mo(V) center with an exchangeable terminal oxo ligand and an equatorial sulfate group on the basis of pulsed EPR spectroscopy and (33)S and (17)O labeling. Here we report new results for species 1 of R160Q, based on substitution of the sulfur-containing ligand by a phosphate group, pulsed EPR spectroscopy in K(a)- and W-bands, and extensive density functional theory (DFT) calculations applied to large, more realistic molecular models of the enzyme active site. The combined results unambiguously show that species 1 has an equatorial sulfite as the only exchangeable ligand. The two types of (17)O signals that are observed arise from the coordinated and remote oxygen atoms of the sulfite ligand. A typical five-coordinate Mo(V) site is compatible with the observed and calculated EPR parameters.

Cadmium sulfite hexahydrate revisited

The present structural revision of the title compound, tetra­cadmium tetra­sulfite hexa­hydrate, [Cd4(SO3)4(H2O)5]·H2O, is a low-temperature upgrade (T = 100 K and R = 0.017) of the original room-temperature structure reported by Kiers & Vos [Cryst. Struct. Commun. (1978). 7, 399–403; T = 293 K and R = 0.080). The compound is a three-dimensional polymer with four independent cadmium centres, four sulfite anions and six water mol­ecules, five of them coordinated to two cadmium centres and the remaining one an unbound solvent mol­ecule which completes the asymmetric unit. There are two types of cadmium environment: CdO8 (through four chelating sulfite ligands) and CdO6 (by way of six monocoordinated ligands). The former groups form planar arrays [parallel to (001) and separated by half a unit cell translation along c], made up of chains running along [110] and [10], respectively. These chains are, in turn, inter­connected both in an intra­planar as well as in an inter­planar fashion by the latter CdO6 polyhedra into a tight three-dimensional framework. There is, in addition, an extensive network of hydrogen bonds, in which all 12 water H atoms act as donors and eight O atoms from all four sulfite groups and two water mol­ecules act as acceptors.

Catalyzed Autoxidation of Hydrogensulfite by Cobalt(II) (2,3,9,10-tetramethyl-1,4,8,11-tetraaza-cyclotetradeca-1,3,8,10-tetraene) (H 2 O) 2 2+

The catalytic autoxidation of hydrogensulfite (hydrogentrioxosulfate(1-)) in the presence of Co(tim)(H 2 O) 2 2+ (tim=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) was studied. Dioxygen reacts with excess sulfite in the presence of Co(tim)(H 2 O) 2 2+ in a complex process (a minimum of five kinetic steps can be identified) to produce Co(tim)(SO 3 ) x (3 m 2 x )+ ( x =1 or 2) ( u max at 350 nm) and sulfate. Seventy turnovers over 4 h were attained in a system where dioxygen and sulfite were supplied constantly. The Co(III) product formed reacts only slowly with dioxygen to produce sulfate. A mechanistic analysis of the results implies the involvement of a Co(tim)-dioxygen adduct, stabilized by an axial sulfite ligand.

Sulfite Stabilization and Reduction of the Aqueous Mercuric Ion: Kinetic Determination of Sequential Formation Constants

The aqueous sulfite ion reacts with Hg2+(aq) to form 1:1 and 2:1 coordination complexes. The Hg(SO3)22- complex is redox stable. However, dissociation of a sulfite ligand forms redox-unstable HgSO3. Under conditions where Hg(SO3)22- predominates, the rate of reduction of the mercuric ion to Hg0 by coordinated sulfite depends inversely on the concentration of uncoordinated sulfite, while it is unaffected by the amount of sulfite liberated by dissociation. Analysis of the kinetics yields the sequential sulfite binding constants K1 = 2.1 × 1013 and K2 = 1.0 × 1010 at μ = 0.10 M. These values lead to the prediction that HgSO3 is more abundant in clouds than is Hg(SO3)22- under virtually all atmospheric conditions. The product of the redox reaction appears to be a strongly bound Hg0·SO2 complex, which is at least 3 orders of magnitude more soluble than uncomplexed Hg0(aq). This finding may have important implications for the partitioning of atmospheric mercury from the gas phase into atmospheric water droplets...

Kinetics and mechanism of formation, acid catalysed aquation, reversible anation and photochemical reaction of trans-(aqua)(sulfito-S )[N,N′-ethylenebis(salicylidiniminato)]cobaltate(III) in aqueous media †

The reaction of trans-[Co(salen)(OH2)OH] with SO2 yields trans-[Co(salen)(OH2)(SO3-S)]− (S-bonded isomer) for which the rate and activation parameters at 25 °C (I = 0.3 mol dm−3) are kSO2 = (5.9 ± 0.1) × 1010 dm3 mol−1 s−1, ΔH‡ = 66 ± 4 kJ mol−1 and ΔS‡ = 183 ± 14 J K−1 mol−1. One possibility for the SIV substitution is that Co–S bond formation is concerted with Co–O bond breaking. An alternative mechanism, involving a fast equilibrium between SO2 and trans-[Co(salen)(OH2)OH] forming an O-bonded sulfito species which then undergoes sulfite ligand linkage isomerisation, is also possible. An estimated value of the isomerisation rate constant for the trans-[Co(salen)(OH2)(OSO2H)] at 25 °C is ca. 106 s−1. The trans-[Co(salen)(OH2)(SO3-S)]− (pK = 10.1 ± 0.1 at 25 °C, I = 0.3 mol dm−3) undergoes acid catalysed aquation to yield the parent diaqua complex and SIV with kH = 29.5 ± 1.1 dm3 mol−1 s−1, ΔH‡ = 72 ± 3 kJ mol−1, ΔS‡ = 24 ± 9 J K−1 mol−1 at 25 °C (I = 0.3 mol dm−3). Steady state photolysis (254 nm) of trans-[Co(salen)(OH2)(SO3-S)]− resulted in the reduction of CoIII. The redox rate constant and ϕ(Co2+) decreased with increasing pH. Attempts to detect an O-bonded sulfito complex as a transient in the conventional flash photolysis of this aqua-sulfito complex proved unsuccessful. The aqua ligand replacement reactions of trans-[Co(salen)(OH2/OH)(OH2)]+/0 with imidazole and that of the corresponding aqua-sulfito complex with N3−, NCS−, imidazole, and SIV in a large excess of the entering ligands have been studied at 25 °C. A comparison of the rate constants with the analogous data for trans-[Co(AA)2(OH2)(SO3-S)]+ (AA = 1,2-diaminoethane; 1,3-diaminopropane) clearly shows that the kinetic trans-effect of the S-bonded sulfite is substantially attenuated in trans-[Co(salen)(OH2)(SO3-S)]−.

Vibrational spectra of ammine–sulfito complexes of rhodium

Ambient and low temperature vibrational spectra of the known complex trans-Na[Rh(SO3)2(NH3)4]·2H2O (1) and the newly prepared fac-Na3[Rh(SO3)3(NH3)3]·2H2O (2) (both also in the deuterated form (1D) and (2D)) were measured and discussed. In both cases the spectra clearly show the effects of the real crystallographic symmetry of the complex entities.In accordance with the results of X-ray structure analyses of 1 and 2 the spectra reveal S-coordination of the sulfite ligands and consequently their trans-influence on the Rh–N bonds, also in terms of both valence vibration v(RhN4) and v(RhN3), respectively, and force constants f(Rh–N) derived from them.

Supramolecular interactions between Co(CN)5(SO3)4− and polyammonium macrocyclic receptors

The acid–base properties as well as the photochemical reactivity of the co-ordination compound K4[Co(CN)5(SO3)] in the presence of three polyammonium macrocyclic receptors were studied in aqueous solution. The pKa of the free complex (3.9) (sulfite deprotonation) changed to pKa <0.5 upon complexation with the receptors. The quantum yield for sulfite photoaquation of the free complex in the basic form (Φ = 0.85 ± 0.09) decreased to 0.05 ± 0.01, 0.12 ± 0.03 and 0.45 ± 0.09 in the presence of [24]aneN8H88+, [30]aneN10H1010+ and [32]aneN8H88+, respectively. For the acidic form of the free complex (Φ = 0.40 ± 0.05) the quantum yield was not affected by supercomplexation with [32]aneN8H88+. For the adducts formed from the other two macrocyclic receptors it was not possible to evaluate the quantum yields of the acidic forms, because protonation was not complete even at very high proton concentrations. The results were interpreted in terms of second-sphere interactions involving hydrogen bonding between the complex and the macrocycles. In the case of [32]aneN8H88+, the experimental results are compatible with a structure in which the cyanides are involved in hydrogen bonding but the sulfite ligand is not. In the two other supercomplexes the sulfite ligand seems to be involved in hydrogen bonding.

Simple structural differentiation of (μ-S,O) bridged sulfito complexes by vibrational spectrometry

Vibrational spectra of the newly prepared complexes [enM(SO 3) 2Men]·3H 2O (M = Pt ( 1) and Pd ( 2), en = 1,2-diaminoethane) indicate that in 1 the sulfite ligands link the two metal centers by two parallel μ-S,O bridges, whereas in 2 antiparallel bridges are realized, in accordance with the results of X-ray structure analyses for 1 and 2. Furthermore, the spectra allow a clear differentiation of the mononuclear educts K 2[M(SO 3) 2en]·2H 2O (M = Pt ( 3) and Pd ( 4)) with S-coordinated sulfite ligands and the binuclear products 1 and 2.

Vibrational spectra of new heteroleptic sulfito complexes of rhodium and iridium

Vibrational spectra of the known complex trans-Na[Rh(SO 3) 2(NH 3) 4]· nH 2O ( 1) and the newly prepared heteroleptic complexes cis-Na[Rh(SO 3) 2(NH 3) 4]·3H 2O ( 2; also in deuterated form ( 2D)), (NH 4) 5[IrCl 2(SO 3) 3(NH 3)]·2H 2O ( 3), and Na 3[IrCl 2(SO 3) 2(OH 2) 2]·7H 2O ( 4) were measured and discussed. In the case of complexes 1 and 2 the spectra allow clear distinction between the cis and trans forms. In accordance with the results of X-ray structure analyses of 2, 3, and 4 the spectral features reveal S-coordination of the sulfite ligands and consequently their trans influence, also in terms of force constants.

The Crystal Structure of Diammonium trans-Tetraammindisulfitonithenate(II)Tetrahydrate,trans-(NH4)2[Ru(SO3)2(NH3)4]·4H2O,and the Tuning of the trans-Influence of the Sulfite Ligand

Abstract trans-(NH4)2[Ru(SO3)2(NH3)4]·4H2O(1) (monoclinic, P21/n; a = 629.8(3), b = 1000.6(2), c = 1345.7(5) pm, β = 112.25(4)°, Z = 2; R = 0.021; Rw = 0.017) is obtained as pale greenish-yellow crystals by reaction of trans-[Ru(SO3H)2(NH3)4] (2) with aqueous ammonia, and crystallization at +5 °C. The compound, when isolated, is stable at room temperature for only a few days even under inert gas, but persists under the mother liquor. In the centrosymmetric anion trans-[Ru(SO3)2(NH3)4]2- the bonds Ru-S = 230.5(1) pm are significantly longer than in the neutral complex 2 (227.6(1) pm), whereas the Ru-N bonds are the same in both com­plexes within experimental error (averages 214.1 and 214.0 pm). Hence, the mutual trans-influence of the sulfite ligands is weakened on protonation; the bonding of the co-ligands in cis-position is not affected. The internal structure of the sulfite ligand in 1 with long S-O bonds (average 151.2(5) pm) and small angles O-S-O (average 106.1(6)°) and the weakened Ru-S bond are a good match. The structure of 1 is held together by a complex network of hydrogen bonds, in which all potential hydrogen-bond donors (OH2, NH4 +, NH3) and acceptors (H2O ,SO3) are involved. The structural findings are reflected in the vibrational spectra.

Die Kristallstruktur von Gadolinium (III)-sulfit Trihydrat Gd2(S03)3∙ 3H2O / Crystal Structure of Gadolinium(III)-sulfite Trihydrate Gd2(SO3)3 ∙3H2O

Abstract Gd2(SO3)3 • 3 H20 is obtained by passing gaseous SO2 through a suspension of Gd2O3 in H2O at room temperature until a clear solution is formed. Single crystals are obtained by heating to 70(2) °C for 6 days. The compound crystallizes in the triclinic space group P 1 with a = 6.499(6), b = 6.621(3), c = 6.954(3) Å, α = 110.71(5), β = 90.54(3), γ = 106.05(1)° and Z = 1. The two crystallographically different gadolinium atoms are both coordinated by eight oxygen atoms forming distorted square antiprisms. Gd(l) is coordinated by six O atoms of sulfite ligands and two O atoms of water, while Gd(2) is surrounded by seven O atoms of SO3 and one of H2O. Gd-O-bond lengths vary between 2.31(3) and 2.50(3) Å.

Vibrational and multinuclear NMR spectra of anionic mercuriomethanes [CH 4-n(HgX) n] n-

Vibrational spectra of solid sodium sulfitomercuriomethanates Na n[CH 4−n(HgSO 3) n]·nH 2O (2 ≤ and ≤ 4) exhibit high frequencies of the valence vibrations ν as(SO 3) > ν s(SO 3) (average 1057 cm −1) with big differences ν as - ν s (mean 104 cm −1), and ν(HgS) vibrations in the 200 to 230 cm −1 range, thus indicating S-coordinated sulfite ligands. Force field calculations for the ion [C(HgSO 3) 4] 4− yield high force constants K(S−O) = 605 N/m, K(Hg−S) = 258 N/m, and even K(C-Hg) = 181 N/m.- For thiosulfatomercuriomethanates [CH 4−n(HgS 2O 3] n− (1 ≤ n ≤ 4) in aqueous solutions Raman spectra suggest S-coordination with high ν as(SO 3) and ν s(SO 3) (average 1130 cm −1), and low ν(S-S) (∼420 cm −1) frequencies, and strong ν(Hg-S) bands (∼250 cm −1). From 1H, 13C and 199Hg NMR data is concluded that the CHg bond strengths in the series decrease on a lower level than in other mercuriomethanes.- On the whole, the electronic properties of the peripheral ligands X in the mercuriomethanes CH 4−n(HgX) n seem to be more important for the CHg bond strengths than the total charge.

Tuning of the trans-influence in sulfito-complexes of platinum(II)

Tuning-up of the trans-influence of sulfite in amminesulfitoplatinates(II) [Pt (SO 3) n (NH 3) 4−n] (2n-2) (0 ≤ n ≤ 4) with growing n and increasing charge is demonstrated by decreasing ν (Pt-N) and ν (Pt-S) frequencies of bonds trans to sulfite. As a consequence, the force constants f (Pt-N) and f (Pt-S) drop in the series from 254 to 223, and from 111 to 88 N m −1, respectively. Similar considerations reveal a decrease of the trans-influence on O-protonation of all S-coordinated sulfite ligands in [PtCl 2(SO 3) 2H] 3− and [Pt(SO 3) 4] 6−, with an increase of both f (Pt-Cl) and f (Pt-S) values. The findings are rationalized by modifications of the σ-donor and π-acceptor properties of the sulfite ligand.

Structural and kinetic trans effects in cobalt(III) complexes with cobalt-sulfur bonds. The crystal structure of trans-Bis(ethylenediamine)imidazolesulfitocobalt(III) perchlorate dihydrate

The crystal structure of the title compound, [Co(C2N2H8)2(C3N2H4)(SO3)] ClO4,2H2O has been determined by X-ray diffraction, using diffractometer data, at 295 K, and refined by full-matrix least squares to a residual of 0.071 for 3425 ?observed? reflections. Crystals are orthorhombic, Pcmn, a 15.822(9), b 11.924(6), c 9.261(2) Ǻ, Z 4. The imidazole and sulfite ligands are trans in the cation, which has m symmetry (Co-S 2.223(2); Co-N 2.008(4) Ǻ). &lt;Co-N(en)&gt; is 1.964Ǻ. The apparent thermal motion of the sulfite about the Co-S axis is very high. The internal internuclear distances are compared to the data reported for series of similar complexes in which trans effects are observed.