New carborane-containing acids and amines

Alkylation of nido-carborane methyl sulfide derivative [9-MeS-7,8-C₂B₉H₁₁]^– was used to synthesize a series of new carborane-containing acids 9-HOOC(CH₂) _n (Me)S-7,8-C₂B₉H₁₁ (n = 1—4) and amines 9-H₂N(CH₂) _n (Me)S-7,8-C₂B₉H₁₁ (n = 2, 3). The compounds obtained can be used for the development of BNCT agents.     

Synthesis and structure of Pt(II) acetamidate complexes containing <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethyl-substituted ethylenediamine and trimethylenediamine

Reactions of acetamide with platinum(II) diamines [Pt(N,N-DimeEn)Cl₂], [Pt(Tm)Cl₂], and [Pt(N,N-DimeTm)Cl₂] (N,N-DimeEn = (CH₃)₂N(CH₂)₂NH₂, Tm = NH₂(CH₂)₃NH₂, N,N-DimeTm = (CH₃)₂N(CH₂)₃NH₂) with preliminary precipitation of chlorine ions by silver salts gave binuclear Pt(II) acetamidates [Pt₂(CH₃)₂N(CH₂)₂NH₂)₂(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (I), [Pt₂(NH₂(CH₂)₃NH₂)₂)(μ-NHCOCH₃)₂](NO₃)₂ · H₂O (II), and [Pt₂(CH₃)₂N(CH₂)₃NH₂)₂(μ-NHCOCH₃)₂](HSO₄)₂ (III), whose crystal structures were determined. Crystals of I are monoclinic: a = 14.459(2) Å, b = 17.197(3) Å, c = 9.822(2) Å, β = 105.923(10)°, V = 3348.6(8) ų, space group P2(1)/c, Z = 4, R _hkl = 0.0419 for 6663 reflections. Complex I is a binuclear acetamidate with bridging (NHCOCH₃)^? ligands, one of which is bound to two Pt atoms through the N and O atoms, and the other ligand is bound only through the N atom. The Pt-Pt distance is 2.987(1) Å. Crystals of II are monoclinic: a = 10.213(7) Å, b = 13.373(9) Å, c = 16.533(11) Å, β = 97.971(9)°, V = 2236(3) ų, space group P2(1)/n, Z = 4, R _hkl = 0.557 for 6462 reflections. The Pt-Pt distance is 3.057(1) Å. Crystals of III are monoclinic: a = 10.557(12) Å, b = 18.531(2) Å, c = 14.4744(17) Å, β = 108.705(2)°, V = 2682(5) ų, space group P2(1)/n, Z = 4, R _hkl = 0.569 for 8506 reflections. The Pt-Pt distance is 3.202(1) Å. Complexes II and III are binuclear acetamidates, in which two chelating Pt(Tm) or Pt(N,N-DimeTm) moieties are coordinated through the N and O atoms of (NHCOCH₃)^? cis-bridges.     

Thermodynamic and kinetic stability of cerium(IV) complexes with a series of aminopolyacetic acids

The compositions, stability constants, and rate constants of intramolecular redox decomposition of cerium(IV) complexes with anions of aminoacetic (H₂NCH₂COOH), iminodiacetic [HN(CH₂COOH)₂], nitrilotriacetic [N(CH₂COOH)₃], ethylenediaminetetraacetic [(CH₂COOH)₂N(CH₂)₂N(CH₂COOH)₂], and hexamethylenediaminetetraacetic [(CH₂COOH)₂N(CH₂)₆N(CH2COOH)₂] acids were determined by potentiometric, spectrophotometric, and kinetic methods at pH in the range 1.3?2.0 in perchlorate and nitrate media at an ionic strength I = 0.1 and a temperature of 298.15 K. Direct linear correlation between the logarithms of the stability constants of the complexes, log β₁₀₁, and logarithms of the cumulative protonation constants, log В _m+k (k = 1–2), of aminopolyacetic acid anions L ^m–, and inverse linear correlation between log β₁₀₁ and logarithms of the rate constants of intramolecular redox decomposition of the complexonates [CeL]^4–m (m = 1–4), log k _n=1, were found.     

Synthesis and properties of 5-substituted 1-dinitromethyl-3-nitro-1 <Emphasis Type="Italic">H</Emphasis>-1,2,4-triazoles

Denitration of 5-R-substituted 3-nitro-1-trinitromethyl-1H-1,2,4-triazoles (R = CH₃, Cl, Br, N₃, NH₂) by the action of potassium iodide or hydroxylamine, followed by treatment with sulfuric acid, gave the corresponding 1-dinitromethyl derivatives which were shown to be very strong CH acids (pK _a ?0.55 to ?1.62).     

The inductive effect of a radical center and transferability of the properties of functional groups in <Emphasis Type="Italic">n</Emphasis>-alkyl radicals

Electron density distribution in n-alkyl radicals (from ethyl to n-octyl) was studied by the B3LYP/6-311++G(3df,3pd) DFT method. The theory of atoms in molecules was used to show that the inductive effect of a free valence extends to two neighboring CH₂ groups. The electronegativities χ(C^?H₂) > χ(CH₃) > χ(CH₂) of groups and χ(C^?) > χ(H) > χ(C) atoms were qualitatively determined. The group method for calculating the enthalpies of formation of n-alkyl radicals Δ_f H°(n-C _n H_{2n+ 1}, n > 5) was substantiated.     

Special Features of the Interaction between Asymmetric Dimethylhydrazine and Thiocontaining Schungite

The interaction between asymmetric dimethylhydrazine and thiocontaining mineral schungite-III has been studied. Chromatography–mass spectrometry has been used to identify alkyl polysulfides as the products of desorption of asymmetric dimethylhydrazine from schungite surface. The interaction of asymmetric dimethylhydrazine with crystalline sulfur has been investigated in a model system. Dimethyl polysulfides, CH₃S_nCH₃; (dimethylamino)methyl polysulfides, (CH₃)₂NS_nCH₃; and bis(dimethylamino) polysulfides, (CH₃)₂NS_nN(CH₃)₂, with 2 ≤ n ≤ 4 have been detected. Gas-chromatographic retention indices have been determined for the products of the interaction of asymmetric dimethylhydrazine with sulfur and the schungite material.     

Reactions of (triethylstannylthioalkyl)trialkoxysilanes and (triethylstannylthioalkyl)trialkoxysilatranes with methyl iodide

Reactions of (triethylstannylthioalkyl)trimethoxysilanes Et₃SnS(CH₂)_nSi(OMe)₃ (n = 1, 2) and (triethylstannylthioalkyl)trialkoxysilatranes Et₃Sn(CH₂) _n Sa [hereinafter Sa = Si(OCH₂CH₂)₃N is silatranyl group] with methyl iodide are studied for the first time. The results of the investigation of the reaction of 1-(2-alkylthioethyl)silatranes RSCH₂CH₂Sa (R = Me, Et) with methyl iodide are also discussed.     

Theoretical studies of the structures and properties of (Br<Subscript>2</Subscript>InN<Subscript>3</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 1–6) clusters

In an attempt to find single-source precursors, a series of small clusters of inorganic azides of indium (Br₂InN₃) _n (n = 1–6) were studied using the dispersion correction density functional theory (wB97XD). The obtained (Br₂InN₃) _n (n = 2–6) clusters have the core structures of 2n-membered ring with alternating indium and α-nitrogen atoms. The influences of cluster size (oligomerization degree n) on the structures, energies, IR spectra, and thermodynamic properties of clusters were discussed. The computed binding energies indicate the stability: 3A > 3B, 4B > 4C > 4A > 4D, 5E > 5D > 5B = 5C > 5A and 6I > 6C > 6D > 6G ≥ 6H > 6F > 6E > 6B > 6A. It is also found that (Br₂InN₃)₂ and (Br₂InN₃)₄ clusters possess higher stability than their neighbor sizes judged by the calculated second-order difference of energies (Δ₂ E). Meanwhile, thermodynamic properties for (Br₂InN₃) _n (n = 1–6) clusters increase with the increasing temperature and oligomerization degree n, and the oligomerizations are thermodynamically favorable at temperatures up to 800 K.     

Determination of the molecular masses of tetrafluoroethylene telomers by gel-permeation chromatography

Gel-permeation chromatography has been employed to study the molecular-mass distribution of tetrafluoroethylene telomers prepared through γ irradiation of 0.05–0.56 mol/l monomer solutions in acetone. The molecular-mass-retention-volume V _R calibration dependence has been plotted from chromatograms of perfluoroenanthic and perfluoropelargonic acids (F(CF₂-CF₂) _n COOH; n = 3 or 4, respectively). The measured V _R-log n curve is located parallel to that plotted earlier for oligo(oxyethylene glycol)s (OH-(CH₂-CH₂O) _n -OH) and is shifted along the volume axis. The shift value is determined by the ratio between logarithmic volumes of chain units of these oligomers. The shift agrees with the assumption that the retention volumes of oligomers with the same spatial chain structure are proportional to the logarithm of the ratio between their van der Waals volumes. This assumption is supported by the quantum-chemical calculation of the molecular volumes of oligomers composed of (CH₂-CH₂) _n , (CH₂-CH₂O) _n , and (CF₂-CF₂) _n fragments. As the concentration of tetrafluoroethylene in the initial solution is increased, the average length of (CF₂-CF₂) _n chains increases from \(\bar n\) ≈ 3 to \(\bar n\) ≥ 8. The maximum values of n = 12–15 are determined by the solubility limit of telomers in THF.     

Kinetics of Isothermal Pyrolysis of Iodomethanes in the Gas Phase

The limiting step of the isothermal pyrolysis of gaseous iodomethane (CH₃I → 3/4CH₄ + 1/2I₂ + 1/(4n)C _n ) and diiodomethane (CH₂I₂ → 1/2CH₄ + I₂ + 1/(2n)C _n ) are the reactions 2CHI → C₂ + 2HI and 2CI₂ → C₂ + 2I₂, respectively. The rate constants of these reactions were determined.     

An efficient multigram-scale synthesis of 4-(ω-chloroalkoxy)phenols

Efficient multigram two-step syntheses of 4-(2-chloroethoxy)phenol and 4-(3-chloropropoxy)phenol in >70% yields starting from 4-hydroxybenzaldehyde and reagents with general formula Cl(CH₂) _n X (X = Cl, n = 2; X = OTs, n = 3) are proposed. 4-(2-Chloroethoxy)phenol can also be conveniently prepared from 4-methoxyphenol and 1,2-dichloroethane. The compounds thus obtained can be used in carbohydrate chemistry to synthesize glycosides bearing "universal" 4-(ω-chloroalkoxy)phenyl aglycons.     

Synthesis and crystal structure of the equimolar complex of copper(I) cyanide with 3,3′-[ethane-1,2-diylbis(oxy)]dipropanenitrile

Complex [Cu(CN)(NC(CH₂)₂O(CH₂)₂O(CH₂)₂CN))] is obtained by the heating of copper(I) cyanide with 3,3′-[ethane-1,2-diylbis(oxy)]dipropanenitrile (DPN) followed by slow cooling. The X-ray diffraction analysis shows that the crystals are monoclinic, space group C2/c, a = 12.183(2), b = 10.667(2), c = 8.4700(13) Å, β = 92.444(10)°, V = 1099.7(3) ų, Z = 4. The structure is built of infinite zigzag fragments [Cu(CN)(DPN)] _n . The tetrahedral environment of the copper atom includes two cyano groups of the ligand and two cyano groups of the inorganic fragment.     

Hydrogen-Bonding Interaction in a Complex of Amino Acid with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide Studied by DFT Calculations

Theoretical studies on hydrogen-bonded complexes between amino acids (glycine, alanine and leucine) and N,N-dimethylformamide (DMF) in gas phase have been carried out using density functional theory (DFT) and ab initio calculations at the B3LYP/6-311++G** and MP2/6-311++G** theory levels. The structures, binding energy, stretching frequency and bond characteristics of the mentioned complexes were calculated. The NH₂ and COOH groups of amino acids form different types of hydrogen bonds with the DMF molecule, as well as alkyl side chains. High binding energy suggests multiple hydrogen bonds present in one complex. The nearly linear OH???O and NH???O contacts are stronger than a conventional hydrogen bond interaction with their H???O separation between 1.74 and 2.14 Å. The weaker CH???O H-bond is also discussed as being a crucial interaction in biological systems involving amino acids. The formation of this interaction results in a blue shift in the CH stretching frequency.     

New coordination modes of iminodiacetamide type ligands in palladium(II) complexes: crystallographic and DFT studies

The reactions of N-alkyliminodiacetamide derivatives, namely N-ethyliminodiacetamide (CH₃CH₂N(CH₂CONH₂)₂; Etimda) and N-isopropyliminodiacetamide (CH₃)₂CHN(CH₂CONH₂)₂; i-Primda), with sodium tetrachloropalladate(II) in aqueous solutions were investigated. Three new palladium(II) complexes, [Pd(Etimda_?H)₂]?2H₂O (1), [Pd(i-Primda_?H)₂]?2H₂O (2) and [PdCl₂(i-Primda)] (3), were obtained and characterized by X-ray structural analysis, infrared spectroscopy and thermal analysis (TGA). The square planar coordination environments around the palladium(II) ions in complexes 1 and 2 consist of two N,N′-bidentate N-alkyliminodiacetamidato ligands, with imino N atoms in trans-position. The complex 3 also exhibits a square planar coordination environment around Pd(II), but with two chloride ions and one neutral N-isopropyliminodiacetamide ligand bound in an N,O′-bidentate coordination mode. The described coordination modes, as well as the presence of deprotonated amide groups in ligands in 1 and 2, are found for the first time in palladium(II) complexes with iminodiacetamide type ligands. The molecular geometries and infrared spectra of these three complexes were also modelled using DFT calculations, at the BP86-D3/def2-TZVPP/PCM level of theory. The RMSD values suggest a good agreement of the calculated and experimental geometries. A QTAIM analysis suggests a qualitative correlation between bond lengths and energy densities, also supported by an NBO analysis. The dimer interaction energy between complex units was estimated at about ?15 kcal/mol for all complexes.     

α- and β-diphenylphosphorylated secondary alkanols: I. general method of synthesis and extraction properties towards <Emphasis Type="Italic">f</Emphasis>-elements

A simple and effective general method of synthesis of α- and β-diphenylphosphorylated secondary alkanols by the reduction of the corresponding phosphorylalkanones with NaBH4 was developed. The extraction properties of the resulting phosphorylalkanols Ph₂P(O)(CR₂)_nCH₂CH(OH)Me (n = 0, 1; R = H, Me) were studied in the recovery of f-elements (La^III, Nd^III, Ho^III, Yb^III, U^VI, Th^IV) from nitric acid solutions into chloroform and compared with those of both related phosphorylketones and known extractants (n-BuO)₃PO, (n-C₈H₁₇)₃PO, and Ph₂P(O)CH₂C(O)N(n-Bu)₂.     

Synthesis and crystal structure of <Emphasis Type="Italic">N,N</Emphasis>-dimethylbiguanidinium hexafluorosilicate

The complex [(CH₃)₂NC(NH₂)NHC(NH₂)NH₂]SiF₆ (I) was synthesized and its structure was determined by X-ray crystallography. The crystals are monoclinic: a = 7.4346(10) Å, b = 12.7628(10) Å, c = 11.0828(10) Å, β 104.080(10)°, V = 1020.01(18) ų, ρ_calc = 1.780 g/cm³, μ(MoK _α) = 0.302 mm^?1, Z = 4, space group P2₁/c. The crystals of I are composed of SiF ₆ ^2? anions (Si-F, 1.657(2)–1.699(2) Å) and N,N-dimethylbiguanidinium (H₂L²⁺) cations combined in a framework by interionic H-bonds NH···F. In the cations, protonation sites are the terminal imide groups.     

<Emphasis Type="Italic">N</Emphasis>-allyl and <Emphasis Type="Italic">N</Emphasis>-propargyl trifluoromethanesulfonimides. Theoretical analysis

Tautomers of N-allyl- and N-propargyl-substituted trifluoromethanesulfonimides (CF₃SO₂)₂NR (R = CH₂CH=CH₂, Z/E-CH=CHMe, CH₂C≡CH, CH=CH=CH₂, C≡CCH₂) were calculated by the DFT (B3LYP, wB97XD, PBE1PBE), MP2, and CBS-QB3 methods. The results were compared with the theoretical data for the corresponding amines and amides NHRR¹ (R¹ = H, CF₃SO₂). It was shown that there is no conjugation between the nitrogen atom and C=C bond and that conjugation exists with the C≡C bond with electron density displacement toward the nitrogen atom. The calculations of anions derived from N-allyl- and N-propargyl-trifluoromethanesulfonimides revealed the possibility of their rearrangement with elimination of trifluoromethanesulfinate anion and formation of its H-complex with N-(prop-2-en-1-ylidene)trifluoromethanesulfonamide or N-(prop-2-yn-1-ylidene)trifluoromethanesulfonamide.     

Effect of mixed thiols on the adsorption,capacitive and hybridization performance of DNA self-assembled monolayers on gold

In this article, we investigated the effect of mixed thiols (HS(CH₂)₅CH₃, HS(CH₂)₆OH and HS(CH₂)₂NH₂) on the adsorption, capacitive and hybridization performance of thiol-modified probe DNA self-assembled monolayers on gold by chronocoulometry (CC) and cyclic voltammetry (CV). Co-assembly of HS(CH₂)₅CH₃ with probe DNA availed DNA surface adsorption on gold more than HS(CH₂)₆OH and HS(CH₂)₂NH₂. With the increase of the assembly concentration ratio of probe DNA and mixed thiols (C _DNA/C _thiols), DNA surface coverage (Γ _m) was almost constant for DNA/HS(CH₂)₅CH₃ mixed SAMs and increased gradually for DNA/HS(CH₂)₆OH or DNA/HS(CH₂)₂NH₂ mixed SAMs. Interfacial capacitance (C _d) value of DNA/thiol-mixed SAMs on gold mainly depended on the capacitance of thiols SAMs. DNA hybridization almost did not change the capacitance value of DNA/thiol-mixed SAMs on gold. Hybridization experiments indicated that the maximal DNA hybridization density (H _D) was 1.2 × 10^?11 and 1.1 × 10^?11 mol cm^?2 with HS(CH₂)₅CH₃ or HS(CH₂)₆OH as mixed thiols respectively, much bigger than that with short-chain thiols (HS(CH₂)₂NH₂). The size fitting coefficient d _c/d _t values for the optimal hybridization of DNA/HS(CH₂)₅CH₃ and DNA/HS(CH₂)₆OH mixed SAMs were 0.70 and 0.93, respectively. This indicated that probe DNA with much bigger Γ _m should be co-assembled with HS(CH₂)₅CH₃ on gold to obtain the biggest H _D than with HS(CH₂)₆OH. These conclusions provided the important reference for optimally designing DNA sensor.     

Synthesis of Polyfluorinated Ethers

Procedures for preparing polyfluorinated ethers H(CF₂CF₂) _n CH₂OR by alkylation of the corresponding telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1–3) with alkyl halides and alkyl tosylates were examined.     

Study of fluoroalkylsilanes,a new class of amphiphilic oligomers: Determination of end groups and chain length

Radiation-initiated polymerization of tetrafluoroethylene (TFE) in the liquid alkylsilanes Si(CH₃)₄ (I), C₂H₅Si(CH₃)₃ (II), and ClSi(CH₃)₃ (III) produces fluoroalkylsilane oligomers with the general formula R(C₂F₄) _n X, where X = H or Cl in I, II, and III and R is one of the radicals generated by the abstraction of H from the methyl and ethyl groups in I and II or Cl detachment from III. The nature of R has been determined using an NMR technique, and the molecular mass distribution (MMD) has been found from abundances in anion progressions in mass spectra and from DTG and GPC data. At initial TFE concentrations (C ₀) changed from 0.4, 1, and 0.13 to 1, 2.7, and 0.7 mol/L in I, II and III, respectively, the average chain length 〈n〉 increases from 4–5 to 10–12 and the MMD changes from the unimodal to the bimodal pattern in which the proportion of oligomers with n < 6 decreases with increasing C ₀. As 〈n〉 increases and the MMD changes, the homogeneous solution becomes colloidal and then turns into a gel. The colloidal particles are largely composed of long oligomers, and the number of solvent molecules per C₂F₄ unit decreases with an increase in C ₀ and is 4–7 in the gel.