Thermodynamics for the Formation of Double‐Stranded DNA–Single‐Walled Carbon Nanotube Hybrids

For the first time, the thermodynamics are described for the formation of double‐stranded DNA (ds‐DNA)–single‐walled carbon nanotube (SWNT) hybrids. This treatment is applied to the exchange reaction of sodium cholate (SC) molecules on SWNTs and the ds‐DNAs d(A)₂₀–d(T)₂₀ and nuclear factor (NF)‐κB decoy. UV/Vis/near‐IR spectroscopy with temperature variations was used for analyzing the exchange reaction on the SWNTs with four different chiralities: (n,m)=(8,3), (6,5), (7,5), and (8,6). Single‐stranded DNAs (ss‐DNAs), including d(A)₂₀ and d(T)₂₀, are also used for comparison. The d(A)₂₀–d(T)₂₀ shows a drastic change in its thermodynamic parameters around the melting temperature (T_m) of the DNA oligomer. No such T_m dependency was measured, owing to high T_m in the NF‐κB decoy DNA and no T_m in the ss‐DNA.     

Modular Analysis of the Crystal Structures of Sulfides and Sulfo Salts with Occupied Tetrahedra of Two Orientations

As a result of modular analysis, relationships between the crystal structures of sulfides and sulfo salts _O[T_m, T_n ]S_1-x (x = 0, 1/4) formed by close packing of sulfur atoms have been established. Four basic types of structure corresponding to the construction module of Laves polyhedra (framework, layer, chain, discrete polyhedron) have been revealed. Formation of superspacings ka, where a is the parameter of the commensurate crystal lattices of sphalerite and sulvanite, is analyzed.     

Evaluating substrate specificity of glutathione peroxidase mimic by molecular dynamics simulations and kinetics

The substrate specificities of glutathione peroxidase (GPX) mimic, 6,6′-ditellurobis(6-deoxy-β-cyclodextrin) (6-TeCD), for three hydroperoxides (ROOH), H₂O₂, tert-butyl hydroperoxide (t-BuOOH) and cumene hydroperoxide (CuOOH), are investigated through molecular dynamics (MD) simulations. The most stable conformations and the total interaction energies of complex of 6-TeCD with ROOH are used to evaluate the substrate specificity of 6-TeCD. The steady-state kinetics of 6-TeCD is studied and the Michaelis-Menten constant (K _m) and second-order rate constant k _max/K _ROOH show that 6-TeCD displays different affinity and specificity to ROOH. These results of experiments are well consistent with ones obtained by MD simulations, indicating that MD simulations could be applied to evaluation substrate specificity of small-molecule enzyme mimics.     

Synthesis of alkoxysilanes as starting substances for preparation of new materials by the sol-gel procedure. Silanes with urea functional group

New bis(triethoxysilanes) containing a urea functional group >NC(O)N< and having the composition (C₂H₅O)₃Si(CH₂)₃NHC(O)NRR [R = R = n-C₃H₇; R = H, R = (CH₂)₃Si(CH₃)(OC₂H₅)₂] and [(C₂H₅O)₃Si(CH₂)₃NHC(O)NH]₂(C_nA_m)_x (A = H, x = 2, 4, 12, n = 1, m = 2; A = H, CH₃, x = 1, n = 6, m = 4; A = H, x = 1, n = 10, m = 6) were prepared in high yields and with satisfactory purity by reactions of primary amines (or diamines) with 3-(triethoxysilyl)propyl isocyanate.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1782–1788.Original Russian Text Copyright © 2004 by Melnik, Lyashenko, Zub, Chuiko, Cauzzi, Predieri.This revised version was published online in April 2005 with a corrected cover date.     

Fullerides: heterometallic superconductors with composition M<Subscript>2</Subscript>M′C<Subscript>60</Subscript> (M = K,Rb; M′ = Yb,Lu, Sc)

One- or two-step reactions of potassium and rubidium fullerides with composition M_k C₆₀ (M = K, Rb; k = 3—6) and K₆C₆₀ + m K mixtures (m = 1, 3) with anhydrous salts MCl₃ (M = La, Pr, Nd, Sm, Gd, Tb, Yb, Lu, Y, Sc) and YbI₂ in a toluene—THF medium afforded heterometallic fullerides M_3–nM_nC₆₀ (n = 1—3). Among these compounds, substituted fullerides with composition M₂MC₆₀ (M = Yb, Lu, Sc) display superconducting properties with critical temperatures of 14—20 K.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1623–1628, August, 2004.     

Electronic structure of DNA dimer units,d(AG) · d, (CT), d(TG) · d(CA), · d(GT), and d(GA), in A and B conformations by DV–Xα cluster calculations

The electronic structure of d(AG) · d(CT), d(TG) · d(CA), d(AC) · d(GT), and d(TC) · d(GA), which are stacked base pairs in the DNA double helix, are elucidated for A and B conformations in detail by DV -X α cluster calculations. By using the S?_r values of the O2 (and O3) of each phosphate in the clusters together with those calculated in previous articles, it becomes possible to treat chemical reactivities of phosphates as recognition sites for all DNA fragments. Contour maps of the wave function of the HOMO and LUMO for bases differ subtly among the clusters and show the various fields around the P ion induced by the respective stacking constructed from four kinds of bases. © 1994 John Wiley & Sons, Inc.     

Preparation of a zwitterionic trichloroplatinum(II) complex with an alkylbipyridinum ligand and its reaction in dmso-<Emphasis Type="BoldItalic">d</Emphasis><Subscript>6</Subscript> solution

A zwitterionic trichloroplatinum(II) complex PtCl₃(4,4′-bpy-N-ⁿBu) (1) was prepared by an aqueous reaction of [4,4′-bpy-N-ⁿBu]Cl with K₂PtCl₄, and was characterized by ¹H-n.m.r. and IR spectroscopy as well as elemental analysis. Dissolving (1) into dmso-d ₆ at 25 °C yields a mixture of the complexes, cis-PtCl₂(4,4′-bpy-N-ⁿBu)(dmso-d ₆) (2-cis), trans-PtCl₂(4,4′-bpy-N-ⁿBu)(dmso-d ₆) (2-trans), [4,4′-bpy-N-ⁿBu]Cl and PtCl₂(dmso-d ₆)₂. Ratio of the products in the dmso-d ₆ solution changed depending on the temperature and the total concentration of the complexes. These compounds are in equilibrium via isomerization reaction between (2-cis) and (2-trans) and via displacement reaction of the alkylbipyridinium ligand of (2-cis) and (2-trans) with dmso-d ₆ to form [4,4′-bpy-N-ⁿBu]Cl and PtCl₂(dmso-d ₆)₂.     

Anomeric DNA: Functionalization of α-d Anomers of 7-Deaza-2′-deoxyadenosine and 2′-Deoxyuridine with Clickable Side Chains and Click Adducts in Homochiral and Heterochiral Double Helices

Anomeric base pairs in heterochiral DNA with strands in the α-d and β-d configurations and homochiral DNA with both strands in α-d configuration were functionalized. The α-d anomers of 2′-deoxyuridine and 7-deaza-2′-deoxyadenosine were synthesized and functionalized with clickable octadiynyl side chains. Nucleosides were protected and converted to phosphoramidites. Solid-phase synthesis furnished 12-mer oligonucleotides, which were hybridized. Pyrene click adducts display fluorescence, a few of them with excimer emission. T_m values and thermodynamic data revealed the following order of duplex stability α/α-d ≫β/β-d ≥α/β-d . CD spectra disclosed that conformational changes occur during hybridization. Functionalized DNAs were modeled and energy minimized. Clickable side chains and bulky click adducts are well accommodated in the grooves of anomeric DNA. The investigation shows for the first time that anomeric DNAs can be functionalized in the same way as canonical DNA for potential applications in nucleic acid chemistry, chemical biology, and DNA material science.     

Phosphane Copper(I) Dicarboxylates: Synthesis and Their Potential Use as Precursors for the Spin‐coating Process in the Deposition of Copper

Dicopper dicarboxylates [(R₃P)_mCuXCu(PR₃)_m] ( 5a , X = O₂CCO₂, R = Ph, m = 2; 5b , X = O₂CCO₂, R = nBu, m = 3) were prepared by treatment of [Cu₂O] ( 1a ) with HO₂CCO₂H ( 2a ) in presence of PR₃ ( 4a , R = Ph; 4b , R = nBu). A further synthesis approach to mono‐ and dicopper dicarboxylates is given using an electrolysis cell equipped with Cu electrodes and charged with acids H₂X and phosphanes R₃P. Without addition of a base mononuclear [(nBu₃P)_mCuXH] ( 6a , m = 3, XH = O₂CCO₂H, 6b , m = 3, XH = O₂CCH₂CO₂H, 6c , m = 3, XH = O₂CCH₂CH₂CO₂H, 6d , m = 2, XH = O₂C‐2‐C₅H₄N‐6‐CO₂H) was formed, whereas in presence of NEt₃ ( 3 ), the dicopper systems [(R₃P)_mCuXCu(PR₃)_m] ( 5a , X = O₂CCO₂, R = Ph, m = 2; 5b , X = O₂CCO₂, R = nBu, m = 3; 5c , X = O₂CCH₂CO₂, R = nBu, m = 3; 5d , X = O₂CCH₂CH₂CO₂, R = nBu, m = 3; 5e , X = O₂C‐2‐C₅H₄N‐6‐CO₂, R = nBu, m = 3) were produced. When 6a reacted with [(tmeda)Zn(nBu)₂] ( 7 ), trimetallic [(tmeda)Zn((nBu₃P)₃CuO₂CCO₂)₂] ( 8 ) was accessible. In this heterobimetallic complex the Zn(tmeda) unit spans two CuO₂CCO₂ entities. The molecular structures of 5a , 6a and 6d in the solid state were determined by single X‐ray structure analysis. Complexes 5a and 6a are monomers, whereas 6d creates in the solid state a linear open chain coordination polymer by hydrogen bridge formation. Characteristic for 6d is the somewhat distorted trigonal bipyrimidal arrangement around the copper atom with the nBu₃P ligands in axial and the C₅H₃NCO₂H oxygen and nitrogen atoms in equatorial positions. In 5a the oxalate connectivity binds in a μ‐1,2,3,4 fashion being part of a planar Cu₂(oxalate) core. TG studies of several mono‐ and dicopper dicarboxylates were carried out. Release of the PR₃ ligands is recognized and the remaining Cu‐(di)carboxylate unit decomposes to afford elemental copper and CO₂. The deposition of copper onto pieces of PVD‐Cu oxidized silicon wafers by applying the spin‐coating process and using 5c and 5d as precursors is discussed.     

Synthesis and physico-chemical and biological studies on ruthenium (III) complexes with Schiff bases derived from aminocarboxylic acids

Summary Ruthenium(III) complexes of types [Ru(L)₃], [Ru(L)Cl(H₂O)₂], [Ru(L)Cl₂]_n, [Ru(L)Cl(H₂O)]_n(LH =Schiff bases derived from anthranilic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; LH₂=Schiff bases derived from anthranilic acid and salicylaldehyde oro-hydroxyacetophenone; LH=Schiff bases derived fromp-aminobenzoic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; LH₂=Schiff bases derived fromp-aminobenzoic acid and salicylaldehyde oro-hydroxyacetophenone) have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moment and spectral (electronic, i.r. and¹H n.m.r.) data. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of crystal field theory and various parameters have been evaluated. On the basis of the electronic spectra, an octahedral geometry has been established for all these complexes except [Ru(L)Cl₂]_n. The complexes [Ru(L)Cl₂]_n are pentacoordinate and a trigonal-bipyramidal environment, D_3h, is suggested for the ruthenium(III) ion. The thermal behaviour of these complexes has also been studied by t.g., d.t.g and d.s.c techniques. Heats of reaction for the decomposition steps were calculated from the d.s.c. curves. The antifungal and antiviral activities of the complexes with Schiff bases derived from anthranilic acid were also investigated.     

Quaternary onium chlorometallates as hydrosilylation catalysts

Sixteen triethylbenzylammonium chlorometallates [Et₃ NCH ₂Ph][MCI_n]^m? (M= transition metal, m= 1–3, n= 3–6) and nine anchored ionic metal complexes [?–CH₂PBu₃][MCI_n]^m? derived from ‘polymer-bound tributylmethylphosphonium chloride’ have been prepared. All the complexes were studied as catalysts in the hydrosilylation of phenylacetylene with triethylsilane. The homogeneous Rh^III, Pt^IV, Ir^III, Cu^II, Zn^II, Fe^III and anchored Pt^IV, Rh^III, Os^IV complexes were found to be active in this reaction. The regio- and stereoselectivity of the following catalyst types is determined by the metal atom involved, being a weak function of the chemical environment; neutral chloride (MCl_n–m); acid (H₂MCl₆); salt containing the lipophilic organic cation ([Et₃NCH₂Ph][MCl_n]^m?); polymer-supported metallate anion ([?–CH₂PBu₃] [MCl_n]^m?).     

Density functional study on highly energetic organic azides with empirical formula Cn(N3)m

The structural, electronic, and thermodynamical properties of C_n(N₃)_m (n = 1–7) (m = 4, 6) organic azides have been investigated using Density Functional Calculations. The ground state structures of organic azides were compared with C_nH_m (n = 1–7) (m = 4, 6) cumulenes which shows their higher relative stability. The stability and reactivity of organic azides were analyzed by calculating the HOMO-LUMO gap, binding energies, and harmonic frequencies of the azides. The binding energy and formation energy of C_n(N₃)_m (n = 1–7) (m = 4, 6) organic azides suggest their energetic stability. The structural analysis of the azide group in C_n(N₃)_m (n = 1–7) (m = 4, 6) organic azide shows a tendency to stabilize at a maximum separation between functional azide groups. Ionization potential, electron affinities, and global hardness have been computed for C_n(N₃)_m (n = 1–7) (m = 4, 6) organic azides and the odd–even alternation rule was observed. The molecular dynamic simulation performed at 300 K for 1 fs confirms organic azide's structural stability at room temperature, except for C₄(N₃)₄, and the members of their family can be synthesized.     

Synthesis and crystal structures of silver(I) and copper(II) complexes with <Emphasis Type="Italic">p</Emphasis>-xylylene-bridged bipyrazolyl ligands

Two semi-rigid bipyrazolyl ligands, namely 2,3,5,6-tetramethyl-1,4-bis[(3′,5′-dimethyl-1H -pyrazol-4′-yl)methylene]benzene (H₂L) and 2,3,5,6-tetramethyl-1,4-bis[(3′,5′-diphenyl-1H -pyrazol-4′-yl)methylene]benzene (H₂L′), and their Ag(I) and Cu(II) complexes have been prepared and structurally characterized by means of X-ray analysis. In the structures of the metal complexes, namely [Ag₂(H₂L)₂](BF₄)₂·2H₂O (1), [Ag(H₂L)(NO₃)]_n (2), [Cu₂(H₂L)₄(SO₄)₂]·11H₂O (3), and {[Ag(H₂L′)]BF₄}_n (4), the bipyrazoles act as bridging ligands to connect two metal atoms. Complexes 2 and 4 exhibit 1-D polymeric structures, while 1 and 3 are discrete molecules with a rectangular dimer or tetragonal prismatic shapes, respectively. Two different conformations, namely cis and trans, have been observed for these bipyrazolyl ligands.     

The synthesis, characterization and antimicrobial activity of N,N′-bis(2-thiophenecarboxamido)-1,3-diaminopropane and N,N′-bis (2-furancarboxamido)-1,3-diaminopropane and their Cu(II), Zn(II), Co(III) complexes

Metal complexes derived from amides; N,N′-bis(2-thiophenecarboxamido)-1,3-diamino propane (1) and N,N′-bis(2-furancarboxamido)-1,3-diaminopropane (2) were characterized by elemental analysis, spectral (NMR, FT-IR, LC-MS) methods, magnetic moment, molar conductance, and TGA/DTA studies. The complexes were dimeric and have the general formula [ML.Cl_m.(H₂O)_n]2Cl₂ where M=Cu(II), Zn(II), Co(III); m = 1, 2; n = 0, 1. The antimicrobial activities of the amides and their complexes were studied against the bacteria; Escherichia coli (ATCC 11230), Yersinia enterocolitica (ATCC 1501), Bacillus magaterium (RSKK 5117), Bacillus cereus (RSKK 863), Bacillus subtilis (RSKK 863) and yeast; Candida albicans (ATCC 10239).     

Ditolyldithiophosphato derivatives of phosphorus(III) and phosphorus(V)

O,O′-Ditolylphosphorodithioates of phosphorus(III), [(o-, m-, or p-CH₃C₆H₄O)₂PS₂] _n PCl_3−n , and phosphorus(V), [(o-, m-, or p-CH₃C₆H₄O)₂-PS₂] _n POCl_3−n , (n = 1, 2, and 3) were isolated as colorless viscous liquids by the reaction of PCl₃ and POCl₃ with sodium ditolylphosphorodithioate, (o-, m-, or p-CH₃C₆H₄O)₂PS₂Na, in 1:1, 1:2, and 1:3 molar ratios in toluene. These compounds were characterized by elemental analyses, molecular weight measurements, IR, and NMR (¹H, ³¹P, and ¹³C) spectroscopic studies, which indicated a less common monodentate linkage of dithiophosphate moieties in both phosphorus(III) and phosphorus(V) derivatives leading to a tetrahedral geometry around the phosphorus atom.     

Synthesis and study of organosilicon hydroxymethylated phenols

A series of (hydroxymethyl)hydroxyphenyldimethylsiloxanes of linear and branched structures were synthesized by the reaction with formaldehyde in aqueous alkaline medium of organosilicon phenols of general formula R′[Si(CH₃)₂O] _n [Si(CH₃)RO] _m SiMe₂R′, where R′ was 4-hydroxy-3-methoxyphenylpropyl, R was methyl or 4-hydroxy-3-methoxyphenylpropyl. The structure and composition of the siloxanes were confirmed by elemental analysis, NMR and IR spectroscopy. The homocondensation of (hydroxymethyl)hydroxyphenyldimethylsiloxanes at the hydroxymethyl groups was investigated. A possibility of reaction of (hydroxymethyl) hydroxyphenyldimethylsiloxanes with phenol-formaldehyde resin to form copolymers was demonstrated.     

Liquid crystalline behaviour of mixtures of structurally dissimilar mesogens in binary systems

We have studied four binary systems comprising four ester components, viz. 4-nitrophenyl-4′-n-alkoxybenzoates (wheren-alkoxy isn-butoxy, C₄,n-hexyloxy, C₆,n-octyloxy, C₈ andn-decyloxy, C₁₀) and one azo component, 4-n-decyloxy phenylazo-4′-isoamyloxy benzene. A variety of mesomorphic properties are observed in these mixtures. The properties of these systems are discussed on the basis of phase diagrams.     

Influence of methyl‐modified silyl groups on the properties of polymers and Si/B/N/C ceramics derived from N‐silylated borazine derivatives

Thermal silazane cleavage of dichloroboryldisilylamines (SiCl_mMe_3?m)N(SiMe₃)(BCl₂) (1: m = 1; 2: m = 2) at 196 °C leads to the borazine derivates [(SiCl_mMe_3?m)NB(Cl_nMe_1?n)]₃ (3: m = 1, n = 0.185; 4: m = 2, n = 0.111) characterized by NMR and IR spectroscopy and mass spectrometry. Single‐crystal X‐ray diffraction structure analyses reveal (BN)₃ units with unusual twisted boat conformations in both compounds. Additionally, more detailed studies are done to clear up the function of the by‐products (SiCl_mMe_3?m)N(SiClMe₂)(BClMe) formed during the cyclization step leading to asymmetrically boron substituted borazine derivatives. The single‐source precursors 3 and 4 were cross‐linked with methylamine producing polymers 3P and 4P, which were transformed into black amorphous materials with ceramic yields of 20.8 % and 50.3 %, respectively. Ceramic 4C (Si_1.00B_0.98 N_2.55 C_1.37O_0.05) was further investigated by ¹¹B and ²⁹Si magic angle spinning (MAS) NMR spectroscopy. A combined study of high‐temperature TG analyses and X‐ray powder diffraction analyses confirms the thermal stability of 4C up to 1670 °C. Copyright © 2012 John Wiley & Sons, Ltd.     

Polymerization of cyclic esters of phosphoric acid. VI. Poly(alkyl ethylene phosphates). Polymerization of 2-alkoxy-2-oxo-1,3,2-dioxaphospholans and structure of polymers

Five-membered cyclic esters of phosphoric acid of the general formula: ? CH₂CH(R)OP(O)-(OR′)O? polymerize readily to solid, soluble polymers of high molecular weight without any rearrangement known for various tri- and pentavalent organophosphorus monomers. ¹H-, ¹³C-, and ³¹P-NMR spectra of polymers confirmed their linear structure: where R is H, with R′ = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇; n-C₄H₉, CCl₃CH₂, or C₆H₅, or R is CH₂Cl and R′ is C₂H₅. The use of n-C₄H₉Li, (C₅H₅)₂Mg, or (i-C₄H₉)₃Al as initiators leads to polymers with M _n = 10⁴–10⁵.     

Assembled synthesis of luminescent mono/double‐layered 2D and 3D Zn (II)‐based coordination polymers tuned by flexible bis (pyridyl)propane‐1,2‐diamines and diverse organic dicarboxylates

Six mono/double‐layered 2D and three 3D coordination polymers were synthesized by a self‐assembly reaction of Zn (II) salts, organic dicarboxylic acids and L1/L2 ligands. These polymeric formulas are named as [Zn(L1)(C₄H₂O₄)_0.5 (H₂O)]_n·0.5n(C₄H₂O₄)·2nH₂O ( 1 ), [Zn₂(L2)(C₄H₂O₄)₂]_n·2nH₂O ( 2 ), [Zn(L1)(m‐BDC)]_n ( 3 ), [Zn₂(L2)(m‐BDC)₂]_n·2nH₂O ( 4 ), [Zn₃(L1)₂(p‐BDC)₃(H₂O)₄]_n·2nH₂O ( 5 ), [Zn₂(OH)(L2) (p‐BDC)_1.5]_n ( 6 ), [Zn₂(L1)(p‐BDC)₂]_n·5nH₂O ( 7 ), [Zn₂(L2)(p‐BDC)₂]_n·3nH₂O ( 8 ) and [Zn₂(L1)(C₄H₄O₄)_1.5(H₂O)]_n·n(ClO₄)·nH₂O ( 9 ) [L1 = N,N′‐bis (pyridin‐4‐ylmethyl)propane‐1,2‐diamine, L2 = N,N′‐bis (pyridin‐3‐ylmethyl)propane‐1,2‐ diamine, m‐BDC^2? = m‐benzene dicarboxylate, p‐BDC^2? = p‐benzene dicarboxylate]. Meanwhile, these polymers have been characterized by elemental analysis, infrared, thermogravimetry (TG), photoluminescence, powder and single‐crystal X‐ray diffraction. Polymers 1–6 present mono‐ and double (4,4)‐layer motifs accomplished by L1/L2 ligands with diverse conformations and organic dicarboxylates, and the layer thickness locates in the range of 5.8–15.0 Å. In three 3D polymers, the L1 and L2 molecules adopt the same cis‐conformations and join adjacent Zn (II) cations together with p‐BDC^2? or succinate, giving rise to different binodal (4,4)‐c nets with (4.5².8³)(4.5³.7²) ( 7 ), pts ( 8 ) topology and twofold interpenetrated binodal (5,5)‐c nets with (3².4⁴.5².6²)(3.4³.5².6⁴) ( 9 ). Therefore, the diverse conformations of the two bis (pyridyl)‐propane‐1,2‐diamines and the feature of different organic dicarboxylate can effectively influence the architectures of these polymers. Powder X‐ray diffraction patterns demonstrate that these bulk solid polymers are pure phase. TG analyses indicate that these polymers have certain thermal stability. Luminescent investigation reveals that the emission maximum of these polymers varies from 402 to 449 nm in the solid state at room temperature. Moreover, 1 , 3 and 5–8 show average luminescence lifetimes from 8.81 to 16.30 ns.