The molecular structure and conformation of trichloronitromethane as determined by gas-phase electron diffraction and theoretical calculations

The molecular structure of trichloronitromethane has been studied in the gas phase using electron diffraction data. The molecules are found to undergo low barrier rotation about the CN bond with a planar CNO₂ moiety in agreement with HF/MP2/B3LYP/6-311G(d,p) calculations. The experimental data are consistent with a dynamic model using a potential function for the torsion of V = (V₆/2)(1 − cos 6τ). The major geometrical parameters (r_g and ) for the eclipsed form, obtained from least squares analysis of the data are as follows: r(NO₃) = r(NO₄) = 1.213(2) Å, r(CN) = 1.592(6) Å, r(CCl)_av = 1.749(1) Å, Cl₅CN/Cl₆CN = 109. 6°/106.3°(2), O₃NC/O₄NC = 117. 6°/114.1°(4), τCl₅C₁N₂O₃ = 0.0°, and V₆ = 0.20(25) kcal/mol.     

Excited state dipole moments of N,N-dimethylaniline from thermochromic effect on electronic absorption and fluorescence spectra

The effect of temperature on absorption and fluorescence spectra of N,N-dimethylaniline (DMA) in ethyl acetate has been studied for temperature ranging from 293 to 388 K. The permittivity ε and refractive index n of the solvent decrease with temperature increase and the absorption and fluorescence bands are blue shifted (so-called “thermochromic shift”). Based on this phenomenon, the dipole moment μ_e in the excited singlet state and the Onsager interaction radius a for DMA were determined using the Bilot and Kawski theory [L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621; 18a (1963) 10, 256].

For the known dipole moment in the ground state μ_g = 1.61 D and for /a³ = 0.54 ( is the polarizability of the solute) the average value of μ_e = 3.55 D and a = 3.1 Å were determined. The obtained values for DMA are compared with the experimental values determined by other authors.     

Structure analysis and the standard molar enthalpy of formation of a coordination polymer [Co(TO)2Cl2]n (TO = 1,2,4-triazole-5-one)

A coordination polymer was synthesized by the reaction of CoCl₂ with 1,2,4-triazole-5-one (TO) and charaterized by means of IR and TG–DTG. Single-crystal structure analysis showed that the complex crystallized in the monoclinic space group C2/c: a = 23.105(9) Å, b = 3.5683(2) Å, c = 13.589(6) Å,  = 90°, β = 124.038(4)°, γ = 90°, V = 928.4(7) Å³, Z = 4. The standard molar enthalpy of formation of the complex was determined to be (−1034.28 ± 0.95) kJ mol⁻¹.     

Synthesis and crystal structure of two novel nickel (imidazole) complexes having hydrogen-bonded networks

Two nickel (imidazole) complexes, Ni(im)₆Cl₂·4H₂O (1) and Ni(im)₆(NO₃)₂ (2) (im=imidazole) have been synthesized and characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. 1 crystallizes in the triclinic space group P-1 with a=8.800(6) Å, b=9.081(6) Å, c=10.565(7) Å, =75.058(9)°, β=83.143(8)°, γ=61.722(8)°, V=718.3(8) Å³, Z=1 and R₁ (wR₂)=0.0469 (0.1497). 2 crystallizes in the trigonal space group R-3 with a=12.370(6) Å, b=12.370(6) Å, c=14.782(14) Å, =90.00°, β=90.00°, γ=120.00°, V=1959(2) Å³, Z=3 and R₁ (wR₂)=0.0358 (0.0955). 1 and 2 exhibit different supramolecular network due to their different counter anions and different hydrogen bonding connection. In compound 1, [Ni(im)₆]²⁺ cation and counter anions Cl⁻ alternatively array in an ABAB fashion via N–HCl hydrogen bonding. In compound 2, the plane of each NO₃²⁻ is almost parallel and each NO₃²⁻ connect three different [Ni(im)₆]²⁺ cations via N–HO hydrogen bonding.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Influence of electronic and steric effects on stability constants and electrochemical reversibility of divalent ion complexes with glycine and sarcosine. A glass electrode potentiometric, sampled direct current polarographic, virtual potentiometric, and molecular modelling study

Cd^II complexes with glycine (gly) and sarcosine (sar) were studied by glass electrode potentiometry, direct current polarography, virtual potentiometry, and molecular modelling. The electrochemically reversible Cd^II–glycine–OH labile system was best described by a model consisting of M(HL), ML, ML₂, ML₃, ML(OH) and ML₂(OH) (M = Cd^II, L = gly) with the overall stability constants, as log β, determined to be 10.30 ± 0.05, 4.21 ± 0.03, 7.30 ± 0.05, 9.84 ± 0.04, 8.9 ± 0.1, and 10.75 ± 0.10, respectively. In case of the electrochemically quasi-reversible Cd^II–sarcosine–OH labile system, only ML, ML₂ and ML₃ (M = Cd^II, L = sar) were found and their stability constants, as log β, were determined to be 3.80 ± 0.03, 6.91 ± 0.07, and 8.9 ± 0.4, respectively. Stability constants for the ML complexes, the prime focus of this work, were thus established with an uncertainty smaller than 0.05 log units. The observed departure from electrochemical reversibility for the Cd–sarcosine–OH system was attributed mainly to the decrease in the transfer coefficient . The MM2 force field, supplemented by additional parameters, reproduced the reported crystal structures of diaqua-bis(glycinato-O,N)nickel(II) and fac-tri(glycinato)-nickelate(II) very well. These parameters were used to predict structures of all possible isomers of (i) [Ni(H₂O)₄(gly)]⁺ and [Ni(H₂O)₄(sar)]⁺; and (ii) [Ni(H₂O)₃(IDA)] and [Ni(H₂O)₃(MIDA)] (IDA = iminodiacetic acid, MIDA = N-methyl iminodiacetic acid) by molecular mechanics/simulated annealing methods. The change in strain energy, ΔU_str, that accompanies the substitution of one ligand by another (ML + L′ → ML′ + L), was computed and a strain energy ΔU_str = +0.28 kcal mol⁻¹ for the reaction [Ni(H₂O)₄(gly)]⁺ + sar → [Ni(H₂O)₄(sar)]⁺ + gly was found. This predicts the monoglycine complex to be marginally more stable. By contrast, for the reaction [Ni(H₂O)₃IDA] + MIDA → [Ni(H₂O)₃MIDA] + IDA, ΔU_str = −0.64 kcal mol⁻¹, and the monoMIDA complex is predicted to be more stable. This correlates well with (i) stability constants for Cd–gly and Cd–sar reported here; and (ii) known stability constants of ML complex for glycine, sarcosine, IDA, and MIDA.     

Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignments for 2-chloroethyl silane

The infrared (3500–30 cm⁻¹) spectra of gaseous and solid and the Raman (3500–10 cm⁻¹) spectra of liquid with quantitative depolarization ratios and solid 2-chloroethyl silane, ClCH₂CH₂SiH₃, have been recorded. Similar data have been recorded for the Si–d₃ isotopomer. These data indicate that two conformers, trans and gauche, are present in the fluid states but only one conformer, trans, is present in the solid. The mid-infrared spectra of the sample dissolved in liquified xenon as a function of temperature (−55 to −100°C) has been recorded. The enthalpy difference between the conformers has been determined to be 181±12 cm⁻¹ (2.17±0.14 kJ/mol) with the trans rotamer the more stable form. From the isolated Si–H frequencies from the Si–d₂ isotopomer the r_o Si–H distances of 1.484 and 1.483 Å for the trans and 1.481 for the gauche conformers have been obtained. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311+G** from which structural parameters and conformational stabilities have been determined. With all the basis sets the trans form is predicted to be the more stable conformer which is consistent with the experimental results. These results are compared to the corresponding quantities for the carbon analogue.     

Kinetic investigation of electronic energy transfer processes following the pulsed dye-laser generation of excited atomic barium, Ba[6s6p(P1)], in the presence of atomic strontium

The collisional behaviour of Ba[6s5d(³D_J)], 1.151 eV above the 6s²(¹S₀) electronic ground state, in the presence of atomic strontium, has been investigated in the ‘long-time domain' (ca. 100 μs–1 ms) following the pulsed dye-laser excitation of barium vapour at elevated temperature at λ = 553.5 nm (Ba[6s6p(¹P₁)] ← Ba[6s²(¹S₀)]. Ba(³D_J) is subsequently produced from the short-lived ¹P₁ state (τ_e = 8.37 ± 0.38 ns) by a number of radiative and collisional processes. It may then be monitored in the ‘long-time domain' by atomic spectroscopic marker methods involving either collisional activation of Ba(³D_J) by Ba(¹S₀) and He buffer gas to yield Ba[6s6p(³P_J)] with subsequent emission from the ³P₁ state (τ_e = 1.2 ± 0.1 μs): Ba[6s6p(³P₁)] → Ba[6s²(¹S₀)] + hv (λ = 791.1 nm). Alternatively, emission from Ba(¹P₁) may be monitored at long times following the generation of this short-lived state by energy pooling following self-annihilation of Ba(³D_J) + Ba(³D_J) from Ba[6s6p(¹P₁)] → Ba[6s²(¹S₀)] + hv (λ = 553.5 nm). The generation of Ba(³D_J) in the presence of atomic strontium yields emission in the long-time domain from Sr[5s5p(³P₁)] (τ_e = 19.6 μs): Sr[5s5p(³P₁)] → Sr[5s²(¹S₀)]  + hv (λ = 689.3 nm). Whilst the decay profiles at short times are complex in form, at long times all these atomic profiles show first-order kinetic removal with the decay coefficients for λ = 791.1 nm, 689.3 nm and 553.5 nm emissions in the ratio 1 : 2 : 2, consistent with overall third-order activation of the form: Ba(³D_J) + Ba(³D_J) + Sr(¹S₀) → Sr(³P_J) + 2Ba(¹S₀). The mechanism is modelled in detail, including measurement of integrated emission intensities, yielding kinetic data for fundamental collisional processes. The overall rate constant for the third-order collisional activation of Sr[5s5p(³P_J])from 2Ba[6s5d(³D_J)] + Sr[5s²(¹S₀)] takes the upper limit of 5.8 × 10⁻²⁷ cm⁶ atom⁻² s⁻¹ (T = 900 K). The rate constant for the two body collisional quenching of Ba[6s5d(³D_J)] by ground state atomic strontium, Sr[5s²(¹S₀)], is found to be (2.0 ± 0.1) × 10⁻¹² cm³ atom⁻¹ s⁻¹ (T = 900 K).     

A photoacoustic calorimetric characterization of the reaction enthalpy and volume for the preparation of a reactive intermediate from CpMn(CO)3

Photoacoustic calorimetry (PAC) allows measurement of the energetics of reactive intermediates. Here, we report the examination of the metal carbonyl η⁵-CpMn(CO)₃ (Cp, cyclopentadiene) via time-independent PAC, in a homologous series of solvents. The measured heat releases allow one to determine simultaneously the enthalpy and volume change resulting from the photodissociation of CpMn(CO)₃. While the photoacoustic signal results from both of these processes, it has often been assumed that the volume change contribution to the observed photoacoustic signal is negligible for small molecules undergoing photodissociation. The current study tests the assumption of a negligible reaction volume by using a more complete treatment. The reaction of an equimolar number of photons and CpMn(CO)₃ molecules, the subsequent photodissociation of the Mn–CO bond, and the ligation of a solvent molecule in an alkane solvent yields ΔH_obs = 32.7 ± 0.7 kcal/mol and ΔV_chem = 11.0 ± 1.3 mL/mol, both of which are independent of the quantum yield of photodissociation. A detailed analysis of the quantum yield is included (using both previously reported measurements, and new data from this work), from which we determine Φ_diss = 0.635. This quantum yield allows us to determine ΔH_rxn = 51.6 kcal/mol and ΔV_rxn = 17.3 mL/mol. These results demonstrate that if the contribution of the reaction volume change to the photoacoustic signal is ignored, the reaction enthalpy derived would underestimate the true value by 7%. We also estimate the BDE{Cp(CO)₂Mn–CO} to be 59.4 kcal/mol.     

The lipid-mediated hypothesis of fumonisin B1 toxicodynamics tested in model membranes

The disruption of lipidic metabolism was considered a good candidate to explain FB1 toxicity mechanism. In the present work we investigated molecular organizational changes induced by FB1–biomembrane interaction possibly involved in mycotoxic effects.

FB1 was self-aggregated with a critical micellar concentration of 1.97 mM. FB1 (0–81.4 μM), decreased in a dose-dependent manner, the fluorescence anisotropy of TMA-DPH (from 0.349 ± 0.003 to 0.1720 ± 0.0035) in dpPC bilayers, whilst no differences were registered with DPH. At 5.6 μM in the subphase, FB1 increased the lateral surface pressure (π) of a Langmuir film to an extent that depended on the monolayer composition (Δπ_{dpPC:DOTAP 3:1} > Δπ_dpPC:dpPA3:1 > Δπ_dpPC), the molecular packing (Δπ decreased linearly as a function of the initial π) and the subphase pH (Δπ_{pH 2.6} > Δπ_{pH 7.4} and maximal π allowing the drug penetration π_cut-off was 34.3 and 27.7 mN/m at pH 2.63 and 7.4, respectively). FB1 increased the surface potential of dpPC and dpPC:DOTAP monolayers and decreased that of dpPC:dpPA. This suggested that FB1 acquired different orientations and/or foldings depending on the surface electrostatics and the toxin charge state. Moreover, FB1–lipid interactions were transduced into long-range effects at the mesoscopic level affecting the lipidic self-separated lateral domains shape and density.     

Comparative characteristics of texture and properties of hybrid organic–inorganic adsorbents functionalized by amine and thiol groups

The structure and texture characteristics of the hybrid organic–inorganic adsorbents, which were obtained by using of two-component systems of “structure-forming agent/trifunctional silane”, are compared as follows: the first component is Si(OC₂H₅)₄ or (C₂H₅O)₃Si–A–Si(OC₂H₅)₃, where A = –(CH₂)₂– or –C₆H₄–; the second one is alkoxysilane with amine (–NH₂, NH, –NH(CH₂)₂NH₂) and thiol (–SH) groups. The adsorbents, derived from TEOS, have more accessible functional groups (2.6–4.2 mmol/g) than xerogels, which are based on bis(triethoxysilanes) (1.0–2.6 mmol/g). On another hand xerogels derived from bis(triethoxysilanes) have a more extended porous structure (S_sp =516–968 m²/g, V_s = 0.418–1.490 cm³/g, d = 2.5–15.0 nm) than those that are based on TEOS (S_sp = 4–631 m²/g, V_s = 0.005–1.382 cm³/g, d = 2.3–17.7 nm). The geometric dimensions of functional groups have a more essential effect on the parameters of porous structure in the case of TEOS-derived xerogels. Using solid-state NMR spectroscopy, it has been shown that in synthesis of xerogels with the use of TEOS, the molecular frame of globules is formed by structural units Qⁿ (n = 2,3,4), and the functional groups exist as structural units of Tⁿ (n = 2,3). The xerogels obtained with using bis(triethoxysilanes) consist only of structural units of Tⁿ-type (n = 1,2,3).     

Synthesis of a novel copper(II) complex and its crystal structure

One novel chiral copper(II) complex was successfully synthesized from the reaction of chiral 1,3-thiazolidine-2-thione ligand with CuCl₂ in dichloromethane in the presence of Et₃N and DMAP at room temperature. Its unique crystal structure was unambiguously disclosed by X-ray analysis. The crystal is tetragonal, space group I4(1), space group a=15.0875(11), b=15.0875(11), c=19.362(3) Å, =90, β=90, γ=90°, V=4407.4(8) ų, Z=8, ρ_calc=1.639 mg cm⁻³.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_{g(S---C2) = 1.719(2) Å}, r_{g(C2=C3) = 1.370(3) Å}, r_{g(C3---C6) = 1.497(6) Å}, r_{g(C2---H) = 1.101(5) Å}, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) - r(S=C₅) and r(C₂=C₃)-r(C₄ =C₅) were fixed at the 3–21G* value of 0.002 Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene

has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_g(S---C₂) = 1.719(2) Å, r_g(C₂=C₃) = 1.370(3) Å, r_g(C₃---C₆) = 1.497(6) Å, r_g(C₂---H) = 1.101(5) Å, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) − r(S---C₅) and r(C₂=C₃) − r(C₄=C₅) were fixed at the 3–21G* value of 0.002Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Density functional theory investigations on the conformational stability and vibrational spectra of the model compound of vitamin K

Becke 3-Lee–Yang–Parr density functional theory (DFT/B3LYP) using 6-31G(d) and 6-311G(d) basis sets and the scaled quantum mechanics (SQM) force field method are used to study molecular conformations and vibrational spectra of a model compound of vitamin K (VK). In this molecule, there are six conformers on the torsional potential energy map of the dihedral angles C₈C₁₄C₁₅C₁₆ () and C₇C₈C₁₄C₁₅ (β). It is shown that the VK_1 conformer ( = 237.7° and β = 274.2°) is the most stable form. For this lowest energy conformer, the harmonic force fields calculated by B3LYP/6-311G(d) and B3LYP/6-31G(d) methods are scaled with one scale factor of 0.9623 and a set of different scale factors transferred from the previous studies for the other similar molecules, respectively. The vibrational frequencies, IR intensities, and Raman activities are obtained for the lowest energy conformer. On the basis of B3LYP calculations, the normal mode analysis is performed to assign the vibrational fundamental frequencies according to the potential energy distributions. The computational frequencies are in good agreement with the observed results.     

Cation–anion interactions in triphenyl telluronium salts. The crystal structures of (Ph3Te)2[MCl6] (M=Pt, Ir), (Ph3Te)[AuCl4], and (Ph3Te)(NO3)·HNO3

Triphenyltelluronium hexachloroplatinate (1), hexachloroiridate (2), tetrachloroaurate (3), and tetrachloroplatinate (4) were prepared from Ph₃TeCl and potassium salts of the corresponding anions. Upon recrystallization of 4 from concentrated nitric acid, K₂[PtCl₆] and (Ph₃Te)(NO₃)·HNO₃ (5) were obtained. The crystal structures of 1–3 and 5 are reported. Compounds 1 and 2 are isostructural. They are triclinic, P , Z=2 (the asymmetric unit contains two formula units). Compound 1: a=10.7535(2), b=17.2060(1), c=21.4700(3) Å, =78.9731(7), β=77.8650(4), γ=78.8369(4)°. Compound 2: a=10.7484(2), b=17.1955(2), c=21.4744(2) Å, =78.834(1), β=77.649(1), γ=78.781(1)°. Compound 3 is monoclinic, P2₁/c, Z=4, a=8.432(2), b=14.037(3), c=17.306(3) Å, β=93.70(3)°. Compound 5 is monoclinic. P2₁/n, Z=4, a=9.572(2), b=14.050(3), c=13.556(3) Å, β=90.76(3)°. The primary bonding in the Ph₃Te⁺ cation in each salt is a trigonal AX₃E pyramid with Te---C bond lengths in the range 2.095(8)–2.14(2) Å and the bond angles 94.1(6)–100.9(5)°. The weak TeCl (1–3) and TeO (5) secondary interactions expand the coordination sphere. In 1 and 2 the cation shows a trigonal bipyramidal AX₃YE coordination with one primary Te---C bond and the shortest secondary TeCl contact in axial positions and the two other Te---C bonds and the lone-pair in equatorial positions. The cation in 3 shows a distorted octahedral AX₃Y₃E environment and that in 5 is a more complex AX₃Y₃Y′₂ arrangement. In both latter salts the structure is a complicated three-dimensional network of cations and anions.     

Three interpenetrated frameworks constructed by long flexible N,N′-bipyridyl and dicarboxylate ligands

Three interpenetrated polymeric networks, {[Co(bpp)(OH-BDC)] · H₂O}_n (1) [Ni(bpp)_1.5(H₂O)(OH-BDC)]_n (2) and {[Cd(bpp)(H₂O)(OH-BDC)] · 2H₂O}_n (3), have been prepared by hydrothermal reactions of 1,3-bis(4-pyridyl)propane (bpp), 5-hydroxyisophthalic acid (OH-H₂BDC), with Co(NO₃)₂ · 6H₂O, Ni(NO₃)₂ · 6H₂O and Cd(NO₃)₂ · 4H₂O, respectively. Single-crystal X-ray diffraction analyses reveal that the three compounds all exhibit interpenetrated but entirely different structures. Compound 1 is a fourfold interpenetrated adamantanoid structure with water molecules as space fillers, in which bpp adopts a TG conformation (T = trans, G = gauche). Compound 2 is an interdigitated structure from the interpenetrated long arms of one-dimensional molecular ladders, while bpp in 2 adopts both TT and TG conformations. Compound 3 is a twofold interpenetrated three-dimensional network from a one-dimensional metal-carboxylate chain bridged by TG conformational bpp. The hydrogen bonding interactions in 1–3 further stabilize the whole structural frameworks and play critical roles in their constructions.     

Anomalous electric birefringence behavior of sonicated DNA fragments as observed in reversing-pulse transients and steady-state sign reversal: a multicomponent approach

Anomalous electric birefringence signals of a sonicated and column-fractionated medium-size calf thymus DNA sample (bp  =  570) in Na⁺ solutions were measured at 7 °C. The reversing-pulse electric birefringence (RPEB) signal pattern was theoretically calculated in the low electric field region for two axially symmetric models coexisting in equilibrium in solution. The RPEB theory is based on the electric dipole moment due to ion-fluctuation along the longitudinal direction and the electric polarizability anisotropy (Δ′), together with various electric and optical parameters assigned to the models. An analytical method was developed for the steady-state birefringence of the two-component system in a wide range of electric fields. The NaDNA samples exhibit complex RPEB patterns mixed with negative- and positive-going profiles. An experimental RPEB signal of NaDNA at an absorbance (A₂₆₀) of 8 was fitted to theoretical curve at weak electric fields. The anomalous RPEB signal was attributed to the component 2, which shows a dip in the buildup and another in the reverse processes with a positive sign and a larger relaxation time. For the component 1, a normal DNA profile with negative sign is associated with a narrow dip in the reverse and a faster relaxation time in the decay signal. The field-strength dependence of observed steady-state birefringence δ(∞) could be fitted for NaDNA at A₂₆₀  =  8 by the SUSID orientation function with saturated ionic and electronic moments. An apparent positive maximum and the sign reversal in δ(∞) at weak electric fields is an interplay between the positive component 2 with positive optical factor Δg and negative Δ′ and the negative component 1 with negative Δg and positive Δ′. Possible conformation of two DNA components involved in solution was estimated.     

Hydrothermal synthesis and intercalation behavior of a layered titanium phosphate Ti2(H2PO4)(HPO4)(PO4)2 · 0.5C6N2H16, with an extended γ-phase intercalated into organic amine

With a hydrothermal technique, a layered titanium phosphate with the formula Ti₂(H₂PO₄)(HPO₄)(PO₄)₂ · 0.5C₆N₂H₁₆ (denoted TP-J2) has been prepared by treating the Ti/H₃PO₄/H₂O/1-methylpiperazine system directly. The as-synthesized products were characterized by powder X-ray diffraction, CP-MAS solid-state ³¹P NMR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA). The structure was solved by single-crystal X-ray diffraction analysis and it presents an extended γ-phase intercalated with organic amine. Crystal data: triclinic, , a = 8.106 (2) Å, b = 8.197 (2) Å, c = 11.658 (2) Å.  = 78.32 (3)°, β = 80.85 (3)°, γ = 77.90 (3)°, Z = 2. Additionally, the intercalation behavior of TP-J2 with n-alkyl monoamine (n = 2, 3, 4, 6, 8, 10 and 12) was investigated. Owing to the strong brønsted base, N,N′-dimethylpiperazine, resides in the interlayer, it presented unusual features of TP-J2 in contrast with that of γ-Tip.     

The system CePO4–K3PO4

The phase diagram of the system CePO₄–K₃PO₄ has been determined based on investigations by differential thermal analysis, X-ray powder diffraction, IR spectroscopy and optical microscopy. The system contains only one intermediate compound K₃Ce(PO₄)₂, which melts incongruently at (1500±20)°C. This compound is stable down to room temperature and exhibits a polymorphic transition at 1180°C. It was confirmed that the low-temperature form β-K₃Ce(PO₄)₂ crystallizes in a monoclinic system, space group P2₁/m with unit cell parameters a=9.579 (5), b=5.634 (6), c=7.468 (5) Å; =γ=90°, β=90.81 (3)°; V=403.083 Å³.