Nanoscale organization of ionic liquids and their interaction with peptides probed by C NMR spectroscopy

An NMR study of 10 l-alanine- and l-valine-containing peptides was carried out in the native [C₂MIM][Cl], [C₄MIM][Cl], [C₆MIM][Cl], [C₄MIM][BF₄], [C₄MIM][PF₆], and [C₄Py][BF₄] ionic liquid media. A unique high sensitivity of the ionic liquid system to the nature of peptide and ability to tune solvent–solute interactions were observed in contrast to regular organic solvents. The l-valine peptides can be selectively dissolved in [C₄MIM][Cl] and [C₆MIM][Cl], whereas their solubility in [C₂MIM][Cl] and other ionic liquids was dramatically lower. In spite of structural similarity between the amino acids, a distinct behavior was observed for the l-alanine peptides. Solvent–solute interactions with an ionic liquid impose significant changes, and NMR spectroscopy is a useful probe for the molecular-level and nanoscale organization of the studied systems. An even/odd effect of the number of amino acids in the peptide on molecular interactions in ionic liquids was observed. Enhancement of chemical properties of peptides in ionic liquids and application of ionic liquids in the separation of peptides are the areas of practical interest in the studied systems.     

Reactions of organic halides with a trigonal pyramidal nickel(0) complex

The nickel(0) comlex [Ni(np₃)], np₃  tris(2-diphenylphinoethyl)amine, which has a trigonal pyramidal geometry in the solid state, readily reacts in solution with organic halides (CH₃I, C₂H₅Cl, C₃H₇Cl, C₆H₅Cl, C₆H₅Br, C₆H₅I and C₆H₅CH₂Cl) to give nickel(I) species with formula [NiX(np3)], (X  Cl, Br, I). Benezene, biphenyl, o-, m-, p-chlorobiphenyl are the other products from the reaction between the title complex and chlorobenzene.     

Beyond a solvent: the roles of 1-butyl-3-methylimidazolium chloride in the acid-catalysis for cellulose depolymerisation

In this report, 1-butyl-3-methylimidazolium chloride ([C₄C₁im]Cl) is demonstrated to enhance the kinetics of acid-catalysed hydrolysis of 1,4-β-glucans in binary solvent mixtures. [C₄C₁im]Cl plays other roles in the reaction beyond acting as a solvent for cellulose, as currently accepted. In fact, the presence of the IL increases the Hammett acidity of the catalyst dissolved in the reaction medium. The kinetic data from cellobiose and cellulose hydrolysis directly correlate with the acid strength found for p-toluenesulfonic acid in the different reaction media studied here. The current report identifies neglected, but yet very important phenomena occurring in cellulose depolymerisation.     

Insertion reactions of isocyanides with platinumcarbon σ-bonded complexes

[Pt(C₁₀H₁₂OCH₃)(PPh₃)Cl] reacts readily with isocyanides by displacement of the coordinated olefinic end of the organic moiety followed by insertion of the isocyanide into the metalcarbon σ-bond. The reaction between the methoxydienyl complex [Pt(C₁₀H₁₂OCH₃)Cl]₂ and cyclohexyl isocyanide involves chloride bridge-splitting to give [Pt(C₁₀H₁₂OCH₃)(C₆H₁₁NC)Cl], followed by olefin displacement and finally isocyanide insertion. The imino derivative produced in this latter reaction has a trans-isocyanide configuration.The chemical properties of these new isocyanide complexes are discussed in terms of relative trans influences, coordinating abilities, and electrophilic characters in comparison with the CO analogues.     

Molecular structure and conformational composition of gaseous 1,1-dichloro-2-bromomethyl-cyclopropane and 1,1-dichloro-2-cyanomethyl-cyclopropane as determined by electron diffraction

The molecular structure of the title compounds have been investigated by gas-phase electron diffraction. Both molecules exist as about equal amounts of the two gauche conformers. There is no evidence for the presence of a syn conformer, but small amounts of this form cannot be excluded. Some of the important distance (r_a) and angle (∠_α) parameters for 1,1-dichloro-2-bromomethyl-cyclopropane are: r(CH) = 1.095(19) Å, r(C₁C₂) = 1.476(11) Å, r(C₂C₃) = 1.517(31) Å, r(CCH₂Br) = 1.543(32) Å, r(CCl) = 1.752(6) Å, r(CBr) = 1.950(13) Å, ∠CCBr = 110.5(1.9)°, ∠ClCCl = 111.9(6)°, ∠CCC = 117.5(1.3)°, σ₁ (CC torsion angle between CBr and the three-membered ring for gauche-1) = 116.2(5.6)°, σ₂ = −132.7(7.6). For 1,1-dichloro-2-cyanomethyl-cyclopropane the parameter values are: r(CH) = 1.101(16) Å, r(C₁C₂) = 1.498(9) Å, r(C₂C₃) = 1.544(21) Å, r(C₂C₄) = 1.497(33) Å, r(CCN) = 1.466(26) Å, r(CN) = 1.165(8) Å, r(CCl) = 1.754(5) Å, ∠CCCN = 113.7(2.0)°, ∠CCC = 122.8(1.6)°, ClCCl = 112.5(4)°, σ₁ = 113(13)°, σ₂ = −124(10)°.     

The microwave spectrum of the unsymmetrical conformation of 1-chloro-2-methyl propane

The microwave spectrum of 1-chloro-2-methyl propane has been recorded and lines assigned to ³⁵Cl and ³⁷Cl species in the unsymmetrical conformation. The rotational and distortion constants in MHz are: C₄H₉³⁵Cl, A = 7527.05, B = 2146.21, C = 1793.59, Δ_JK = 4.15 × 10^?3, δ_j = ?8.0 × 10^?5; C₄H₉³⁷Cl, A = 7524.40. B = 2091.73, C = 1755.54, Δ_JK = 2.5 × 10^?3, δ_j = 2.0 × 10^?4.     

High-field solid-state <Superscript>35</Superscript>Cl NMR in selenium(IV) and tellurium(IV) hexachlorides

We report solid-state ³⁵Cl NMR spectra in three hexachlorides, (NH₄)₂SeCl₆, (NH₄)₂TeCl₆ and Rb₂TeCl₆. The C_Q(³⁵Cl) quadrupole coupling constants in the three compounds were found to be 41.4±0.1 MHz, 30.3±0.1 MHz and 30.3±0.1 MHz, respectively, some of the largest C_Q(³⁵Cl) quadrupole coupling constants ever measured in polycrystalline powdered solids directly via ³⁵Cl NMR spectroscopy. The ³⁵Cl EFG tensors are axial in all three cases reflecting the C_4v point group symmetry of the chlorine sites. ³⁵Cl NMR experiments in these compounds were only made possible by employing the WURST-QCPMG pulse sequence in the ultrahigh magnetic field of 21.1 T. ³⁵Cl NMR results agree with the earlier reported ³⁵Cl NQR values and with the complementary plane-wave DFT calculations. The origin of the very large C_Q(³⁵Cl) quadrupole coupling constants in these and other main-group chlorides lies in the covalent-type chlorine bonding. The ionic bonding in the ionic chlorides results in significantly reduced C_Q(³⁵Cl) values as illustrated with triphenyltellurium chloride Ph₃TeCl. The high sensitivity of ³⁵Cl NMR to the chlorine coordination environment is demonstrated using tetrachlorohydroxotellurate hydrate K[TeCl₄(OH)]?0.5H₂O as an example. ¹²⁵Te MAS NMR experiments were performed for tellurium compounds to support ³⁵Cl NMR findings.     

Microwave spectrum and structure of equatorial chlorocyclohexane

The microwave rotational spectra of C₆H₁₁³⁵Cl and C₆H₁₁³⁷Cl have been measured. The rotational constants A, B and C and quadrupole coupling constants were determined. Some structural information was obtained.     

Fastener effect on magnetic properties of chain compounds of dinuclear ruthenium carboxylates

Chlorido-bridged chain complexes of dinuclear ruthenium benzoate analogues, [Ru₂{3,4,5-(C _m H_2m+1O)₃C₆H₂CO₂}₄Cl] _n (mCl) (m = 3, 5–7, 9, 11, 13, 15, 17), were synthesised and the crystal structure of 3Cl · 2nH₂O was revealed. The magnetic measurements for a series of the complexes mCl (m = 2–18) revealed that all the complexes show an antiferromagnetic interaction between the dinuclear unit, with a fastener effect giving the stronger interaction as the alkyl-chain length m increases.     

Studying the adsorption and activation of benzene and chlorobenzene on Ni(12%)/Al2O3 by means of gas chromatography and quantum chemistry

In studying the surface and adsorption properties of Al₂O₃ and Ni(12%)/Al₂O₃ with respect to C₆H₆ and C₆H₅Cl, it is found that adsorbate-adsorbent interaction is stronger than adsorbate-adsorbate interaction. It is shown that the calculated isosteric heats of adsorption vary in a range of 61 to 45 kJ/mol depending on adsorption magnitude; for Ni(12%)/γ-Al₂O₃, as in the case of γ-Al₂O₃, the heat of adsorption of chlorobenzene is higher at low degrees of filling than that of benzene. According to density functional theory quantum-chemical calculations of the structures of complexes (NinC₆H₅Cl) ^z and (Ni _n C₆H₆) ^z (n = 1, 4; z = ?1, 0, +1), a nickel atom can penetrate into C₆H₅Cl along the C-Cl bond. It is concluded that a negative charge on nickel contributes to the efficient activation of the C-Cl bond and to an increase in the rate of desorption of benzene, a key step in the hydrodechlorination of chlorobenzene.     

Microwave spectrum of dichloroborane (BHCl2)

The microwave spectrum of dichloroborane has been observed and the rotational constants of four isotopic species are determined as follows: A = 46911.09(7), B = 3185.937(10) and C = 2980.425(14) MHz for the normal species, A = 46747.14(8), B = 3099.543(14) and C = 2904.037(14)MHz for BHCl³⁷Cl, A = 49302.05(24), B = 3185.536(32) and C = 2989.368(51) MHz for ¹⁰BHCl₂ and A = 35153.18(9), B = 3186.026(15) and C = 2918.233(11) MHz for BDCl₂. The following complete r_s structure was determined: r_s(BH) = 1.184(2) Å, r_s(BCl) = 1.735(2) Å and ∠ ClBCl = 120.4(2)°. The hyperfine structure due to the two chlorine and one boron nuclei has been analysed.     

Bis(indenyl)titanium(IV) and zirconium(IV) complexes of monofunctional bidentate salicylidimines

Dichlorobis(indenyl)-titanium(IV) and -zirconium(IV), (C₉H₇)₂TiCl₂ and (C₉H₇)₂ZrCl₂, react with bidentate Schiff bases such as salicylidene aniline, salicylidene-o-toluidine, salicylidene-m-toluidine and salicylidene-p-toluidine in a 1:1 molar ratio in refluxing tetrahydrofuran in the presence of triethylamine to yield complexes of the type (C₉H₇)₂Ti(SB)Cl and (C₉H₇)₂Zr(SB)Cl, respectively where SB is the anion of the corresponding Schiff base, SBH. The new derivatives have been characterised on the basis of their elemental analyses, conductance measurements and spectral (IR, ¹H NMR and electronic) studies.     

Arylmercury(II) compounds involving intramolecular coordination via 2-Me2NCH2- and chiral (S)-2-Me2NCHMe-ring substituents

Arylmercury compounds of the type Ar₂Hg and ArHgX (X = Cl, OAc) have been synthesized and characterized by ¹H and ¹³C NMR spectroscopy; the Ar group was either 2-Me₂NCH₂C₆H₄ or (S)-2-Me₂NCH(Me)C₆H₄, both of which contain N-donor ligands. The observation of anisochronous NMe resonances in (S)-2-Me₂NCH(Me)C₆H₄HgX (X = Cl, OAc) at low temperature indicates that in solution the mercury centre is three-coordinate as a result of stable intramolecular HgN coordination     

The interaction of an osmium-carbon triple bond with copper(I), silver(I) and gold(I) to give mixed dimetallocyclopropene species and the structures of Os(AgCl) (CR) Cl(CO) (PPh3)2

The osmium carbyne complex, Os(CR)Cl(CO)(PPh₃)₂, (R  p-tolyl) reacts with Group I halides to form the mixed dimetallocyclopropene species, $\text{Os(Cul)(C}$R)Cl(CO)(PPh₃)₂, $\text{Os(AgCl)(C}$R)Cl(CO)(PPh₃)₂, $\text{Os(AuCl)(C}$R)Cl(CO)(PPh₃)₂, and [$\text{Os[Ag(OClO}{}_3\text{)](C}$R)Cl(CO)(MeCN)(PPh₃)₂] ClO₄ X-ray crystal structure determination of $\text{Os(AgCl)(C}$R)Cl(CO)(PPh₃)₂ confirms the presence of a three-membered ring and the structure can be viewed as the “acetylene-like” interaction of an osmium—carbon triple bond with AgCl. In acid solution AgCl is precipitated and an alkylidene complex results from proton addition to the carbyne ligand.     

Reactions of methyltris(triarylphosphine)cobalt : II. Rearrangement of triarylphosphine and oxidative additions of aryl halides

Solutions of [(C₆H₅)₃P]₃CoCH₃ (I) in C₆H₅Cl yield biphenyl, triphenylphosphine, methyldiphenylphosphine and diphenylphosphine. In 4-ClC₆H₄CH₃, 4-methylbiphenyl and 4,4′-bitolyl form as well. Solutions of I in C₆H₆, C₆D₆, C₆H₅CH₃, C₆H₅Br yield only triphenylphosphine and biphenyl, while in 4-FC₆H₄I 4,4′-difluorobiphenyl is formed but no biphenyl. The cobalt compound is recovered as (Ph₃P)_nCoX or as CoX₂ (XCl, Br, I, n = 3 or 2) from reactions with arylhalides. The results are rationalized in terms of the very strong tendency for I to undergo oxidative addition reactions.     

Reassignment of the infrared spectra of SnPh3Cl. An infrared method to characterize SnPh3Cl 1—1 adducts

The stretching vibrations of the SnC₃Cl group in the infrared spectrum of SnPh₃Cl have been reassigned on the basis of an SnC₃ group belonging to the C_3ν point group which is replaced by D_3h in SnPh₃Cl₂TMN (TMN = tetramethylammonium). The important shift (108 cm⁻¹) of ν_sSnC₃ from SnPh₃Cl to SnPh₃Cl₂ TMN is due to a “C_3ν point group inversion” (ν_sSnC₃ is higher in frequency than ν_asSnC₃ in the i.r. spectrum of SnPh₃Cl).     

Optically active pseudoctahedral rhodium(III), iridium(III), and ruthenium(II) complexes with α-amino acidato ligands. Crystal structures of RIrSCSN- and SIrSCSN-[(C5Me5)Ir(pro)Cl] · 12H2O (Hpro = l-proline)

The synthesis and characterization of optically active amino acidato complexes of the types [(C₅Me₅)M(aa)Cl], [(p-cymene)Ru(aa)Cl], [(C₅Me₅)M(aa)(PPh₃)]BF₄, and [(p-cymene)Ru(aa)(PPh₃)]BF₄ (M = Rh, Ir; Haa = l-alanine, l-proline), in which the metal is a chiral centre, are reported. The cationic species were prepared via the solvato-complexes [(C₅Me₅)M(aa)(MeOH)]⁺ and [(p-cymene)Ru(aa)(MeOH)]⁺, which epimerize rapidly on the ¹H NMR time scale. The crystal structure of the complex [(C₅Me₅)Ir(pro)Cl] is reported; the asymmetric unit contains two independent molecules differing in the configuration at the metal.     

Perhalophenyl complexes of palladium(II) containing keto-stabilized phosphorus ylides of the type Ph2P(CH2)nPPh2CHC(O)R

From suitable perhalophenyl derivatives of palladium(II), viz.: Pd(C₆F₅)₂-(SC₄H₈)₂, [Pd(μ-X′) (C₆X₅)₂]₂(NBu₄)₂, [Pd(μ-Cl)(C₆X₅)(SC₄H₈)]₂ (X = F, Cl, X′ = Cl, Br), new complexes of various types have been prepared, viz.: trans-Pd(C₆F₅)₂(Y)₂, Pd(C₆X₅)₂(Y), PdCl(C₆X₅)(Y) (X = F, Cl). The neutral ligand Y is a keto-stabilized phosphorus ylide of the type Ph₂P(CH₂)_nPPh₂CHC(O)R (n = 1, R = CH₃, C₆H₅; n = 2, R = C₆H₅) acting in a terminal monodentate P-donor or a bidentate chelate P,C-donor mode. The reaction of PdCl(C₆F₅)(Y) complexes with HCl leads to the corresponding PdCl₂(C₆F₅)(YH) complexes in which the phosphonium cation [YH]⁺ behaves as monodentate P-donor at its phosphinic end.IR and ³¹P NMR spectroscopy were used to decide the coordination mode of the ligands and, in some cases, to reveal the presence of two isomers.     

Ionic Liquid-Induced Structural and Activity Changes in Hen Egg White Lysozyme

Lysozyme crystals in the presence of 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim]BF₄), 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl), 1-butyl-3-methylimidazolium bromide([C₄mim]Br), and 1,3-dimethylimidazolium iodine([dmim]I) were prepared, and the influence of ionic liquids (ILs) on the structure and activity change of lysozyme was investigated. Fourier transform infrared spectroscopy revealed the major secondary structures of α-helix and β-sheet for lysozyme. It was interesting to note that increases of the band near 2,935 and 1,656 cm^?1 from Raman spectroscopy are attributed to the unfolding of lysozyme molecules. A shift in amide III from 1,230 to 1,270 cm^?1 in adding [dmim]I occurs, indicating a transformation from β-sheet to random coil. With regard to adding [C₄mim]BF₄, [C₄mim]Cl, and [C₄mim]Br, α-helix and β-sheet are the predominant structures for lysozyme. The activity study showed that the ILs used brought a positive effect. Especially, [dmim]I leads to a drastic increase in relative activity, and its value reaches 50 %.     

Solubility in the water-Catamine AB-(alkali metal or ammonium chloride) systems

Solubility in ternary aqueous stratifying systems containing Catamine AB (alkylbenzyldimethylammonium chloride [C _n H_{2n + 1}N⁺(CH₃)₂CH₂C₆H₅] · Cl, a cationic surfactant, where n = 10–18) and LiCl, NaCl, KCl, and NH₄Cl inorganic salts was studied for the first time at 25°C. The boundaries of two-phase liquid equilibrium fields were determined. The studied stratifying systems were proposed for use in the liquid extraction of metal ions.