1–D Framework l-arginine zinc(II) units bridged by oxalate: synthesis,structure, properties,and theoretical studies

We synthesized a l-arginine containing Zn²⁺ complex and oxalate ions. {[Zn₂(l-Arg)₂(ox)₂]·8H₂O}_n (1) (l-Arg =l-arginine, ox = oxalate) crystallize in the monoclinic space group P2₁ with a = 8.979(2), b = 9.840(2) (Å), c = 18.509(3) (Å), β = 95.58(3) (Å), V = 1627.6(6) ų, and Z = 2. The zinc centers are six-coordinate via one l-arginine zwitterion and two bridging oxalates. The binuclear [Zn₂(l-Arg)₂(ox)₂] units are linked via oxalate and form 1-D “stair-like” linear chains. The complex was characterized using FT-IR, FT-Raman, UV–vis spectroscopy, and thermal analysis techniques, as well as DFT methods. Electronic bands above 31,000 cm^?1 originate in ^1,3A_u (n→π*) transitions within oxalate ions. Theoretical studies were performed for the model compound {[Zn(l-Arg)(Hox)₂]·4H₂O} using the fragment of the crystallographic structure of 1. The interaction energy (ΔE) values for l-arginine and two oxalate ions are comparable at -145 kcal mol^?1. Natural bond orbital (NBO) analysis of the electronic structure and bonding is also discussed.     

Monte Carlo study of star-branched polymers on the tetrahedral lattice. I. Conformation of the macromolecule

The star-branched polymers on the tetrahedral lattice are studied by means of the Monte Carlo method. The influence of solvent quality on the dimensions of the coil is described for both linear and branched polymer systems of different functionality. It has been observed that the ratios of gyration radii 〈S²〉_b/〈S²〉_l are greater than those predicted theoretically for the random-flight model. The fourth reduced moment of S² distribution and the mean-square separation of the branch ends from the center of gravity have been also computed. The changes in segment arrangement in the coil with increasing number of branches have been observed.     

Synthesis,Characterization and Crystal Structure of a Ternary Cu(II) Complex with 1,10-Phenanthroline and l-Leucinate

The complex [Cu(l-Leu)(phen)(H₂O)]NO₃ has been synthesized and characterized by elemental analysis, molar conductivity, spectroscopic and X-ray diffraction methods, where phen = 1,10-phenanthroline and l-Leu = l-leucinate. The complex crystallizes in the triclinic space group Pī with two molecules in a unit cell of dimensions a = 7.288(4) Å, b = 11.588(7) Å, c = 12.349(3) Å, α = 86.388(10)^o, β = 76.175(11)°, γ = 72.132(3)°, V = 963.8(10) ų, Z = 2, D _c = 1.564 g/cm³, μ = 1.177 mm^?1, F(000) = 470, R ₁ = 0.0611, and wR ₂ = 0.0711. The copper(II) is ligated in a distorted square-pyramidal geometry by the two nitrogen atoms of phen and the amino nitrogen atom and one carboxylate oxygen atom from each independent l-Leu moiety in the basal plane, and one water oxygen at the apical position. A supramolecular configuration is formed from strong phen-phen stacking interactions between neighboring [Cu(l-leu)(phen)(H₂O)]⁺cations in the crystal.     

Configurational-conformational statistics of stereoirregular polystyrene

The dependence of the configurational-conformational characteristics, such as the mean-square end-to-end distance, the mean-square radius of gyration, and the temperature coefficient of the stereoirregular polystyrene chains on the fraction of meso dyads, P_m was investigated, using the periodic condition method. The calculation shows that polystyrene has the most compact chain when P_m = 0.7, and the temperature coefficient of the characteristic ratio of the mean-square end-to-end distance reaches the minimum, −0.89 × 10⁻³ K⁻¹, at P_m = 0.5. The theoretical result of the mean-square radius of gyration for atactic polystyrene, 〈S²〉^1/2 = 0.2245 M^0.5106 shows good agreement with the experimental measurement in both bulk amorphous state and θ-solvent.     

Isothiocyanate controlled architecture,spectroscopic, and magnetic behavior of copper(II) l–arginine complexes

Abstract

We synthesized an l–arginine complex with the formula [Cu(l–Arg)₂(NCS)]·(NCS)·H₂O (1) (l–Arg = l–arginine). Two cis-chelated l–arginine zwitterions form the basal plane, while the weakly N-bonded isothiocyanate is located at the apex of the distorted square pyramidal structure (τ?=?0.143). The non-coordinated NCS^? anions held layers together in a 3-D supramolecular network. The crystal structure, spectroscopic (FT–IR, Raman, NIR–Vis–UV, EPR) and magnetic properties of 1 have been compared with [Cu(l–Arg)(NCS)₂] (2). For 1, two absorptions are observed for ν(C?=?N) stretching vibrations, corresponding to NCS^? ions N-bonded to the central Cu(II) (2077?cm^?1) and in the lattice (2057?cm^?1). In 2 a single band is observed at 2102?cm^?1, indicating equivalent NCS^? ions in the structure. The EPR spectra of complexes show anisotropic signal with g_⊥ and g_|| 2.062, 2.235 (1), and 2.08, 2.225 (2) characteristic for cis-N₂O₂ and N₃O donor sets in the xy plane, respectively. The unpaired electron mainly occupies the d_x2–y2 orbital, also confirmed by the single envelope of d–d bands at ca. 16,000?cm^?1 for 1 and 16,500?cm^?1 for 2. The magnetic properties ofcompounds are characteristic of a very weak antiferromagnetic interaction with J?=??0.055?cm^?1 and J?=??0.096?cm^?1 for 1 and 2, respectively.     

On the Sanibel coefficients in the expansion of spin-projected slater determinants

Every Slater determinant D may be uniquely analyzed in terms of spin components D_l = O_lD which are pure spin eigenfunctions, so that S²D_l = l(l+1)D. Every component D_l = O_lD may in turn be written as a sum of symmetric combinations of Slater determinants, T_k = [α^μ?kβ^k‖α^kβ^ν?k], and the coefficients c in the expansion O_lD = ∑_k c T_k are known as the “Sanibel coefficients.” By using the relation S²D_l = l(l+1)D, a recursion formula for the coefficients c is derived, which is then explicitly solved in the special case when S_z has the pure quantum number m = 0.     

Thermochemical Studies for Determination of the Standard Molar Enthalpies of Formation of Alkyl-Substituted Furans and Some Ethers

The standard molar enthalpies of vaporization _l ^g H _m ^º of 2,5-dimethylfuran, 2-tert-butylfuran, 2,5-di-tert-butylfuran, cyclopentenyl methyl ether, cyclohexenyl methyl ether, and tert-amyl methyl ether were obtained from the temperature variation of the vapor pressure measured in a flow system. The standard (p° = 0.1 MPa) molar enthalpies of formation _f H _m ^º (1) at the temperature T = 298.15 K were measured using combustion calorimetry for 2,5-dimethylfuran, 2-tert-butylfuran, and 2,5-di-tert-butylfuran. From the derived standard molar enthalpies of formation for gaseous compounds, ring correction terms and non-nearest neighbor interactions useful in the application of the Benson group additivity scheme were calculated.     

Synthesis and characterization of cyclic P3HT as a donor polymer for organic solar cells

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled M_n was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with M_n ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10^?4 cm² V^?1 s^?1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10^?4 cm² V^?1 s^?1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). The l‐P3HT:PC₇₁BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC₇₁BM. In addition, an amount of collected electrons in c‐P3HT:PC₇₁BM was greater than that in l‐P3HT:PC₇₁BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 266–271     

Nonorthogonal radial orbitals for the configuration lnl

The theory of treating the configuration n₀ln₁l^Nn₂l by means of nonorthogonal radial orbitals is described. The expressions for the matrix elements of the nonrelativistic Hamiltonian are deduced. A table that enables one to obtain these expressions in terms of radial integrals for l = 0 and 1 are given. Numerical calculations are performed for the configuration 1s²2s²2p3p using generalized hydrogen-like radial orbitals. The numerical values of the inter-term energy differences are given and discussed.     

Energy balance in networks simply elongated at constant temperature

Summary Mechanical and thermal energy exchange in isothermal simple elongation experiments on various rubbers observed by Godovsky can fully be described by means of implicit relations which are defining the thermo-elastic properties of van der Waals networks up to highest elongations. Global and local properties in the molecular networks are shown to be uniquely related thus manifesting indirectly the existence of a Gibbs-function.Symbols f force per unit unstrained area - f _s,f _e entropy- or enthalpy component of the deformational stress - N density of crosslinks - k Boltzmann's constant - T absolute temperature - L ₀ fiducial length - < ²> actual mean-square end-to-end distance - < ₀> mean-square end-to-end distance of the equivalent free chains - () deformation function - D=/ derivative of() - strain parameter - _m maximum strain - a ₁,a ₂ interaction — van der Waals parameters - linear coefficient of thermal expansion - linear coefficient of compressibility - V ₀ volume in the unstrained state of the rubber - h _K ⁽ⁱ⁾ ,s _K ⁽ⁱ⁾ specific enthalpy and entropy of the internal freedom (K)     

Unperturbed chain dimensions of isotactic polypropylene in theta solvents

The unperturbed mean-square end-to-end distance 〈R₀²〉 and its temperature variation d In 〈R₀²〉/dT for isotactic polypropylene have been estimated from intrinsic viscosity data in three theta solvents, i.e., diphenyl, diphenyl ether, and dibenzyl ether, measured at their θ temperatures as determined by precipitation temperature measurements. The characteristic ratios, 〈R₀²〉/nl², where n is the number of bonds of length l in the main chain, evaluated by assuming Φ = 2.87 × 10²¹, are 5.80 in diphenyl (at θ = 125.1°C.), 5.41 in diphenyl ether (at θ = 142.8°C.), and 4.56 in dibenzyl ether (at θ = 183.2°C.). These values lead to the temperature coefficient d In 〈R₀²〉/dT = ?4.09 × 10^?3 deg.^?1 Results are compared with the data previously reported on polyethylene.     

Clathrate formation in binary aqueous systems with CH2Cl2, CHCl3 and CCl4 at high pressures

P,T,X phase diagrams of the CH₂Cl₂-H₂O, the CHCl₃-H₂O and the CCl₄-H₂) systems have been studied by DTA in the pressure range 10^–3 to 5.0 kbar. Under pressure the cubic structure II (CS-II) hydrates forming in all the systems are replaced by hydrates with the composition M·7.3 H₂O whose stoichiometry and positive dT/dP values of melting lead us to believe that they are CS-I hydrates.In the CH₂Cl₂ and CHCl₃ systems the nonvariant point coordinates of the hydrate transformationQ ₂ ^h (l₁h17h7l₂, where l₁ and l₂ are liquid phases abundant in water and hydrate former, respectively, h₁₇ and h₇ are hydrates with hydrate numbers 17 and 7, respectively) areP = 0.6 kbar, T = –1.5°C andP =2.65 kbar,T = –10.5°C, respectively. In the CCl₄ system the 4-phaseQ ₃ ^h point (l₁h₁₇h₇s, where s is crystalline CCl₄) has coordinatesP = 0.75 kbar and T = 0.4°C.The main obstacle of the present study, the very slow achievement of equilibrium, has been eliminated by adding small amounts (0.25% by mass) of surfactants followed by ultrasonic mixing. We have shown that this accelerates the achievement of equilibrium without changing its position.     

Study on synthesis of lanthanide chelates of (l)-α-trifluoromethyl-polyfluoroalkyl-β-diketone and their application as chiral shift reagents

The lanthanide chelates of (l)-2, 2-dimethyl-6-trifluoromethyl-7-oxa-6, 8, 8, 9, 9, 10, 10, 10-octafluoro-3, 5-decanedione, Ln [(l)-CF₃CF₂CF₂OCF (CF₃) COCHCOC (CH₃)₃]₃ (l-3a, Ln=Eu; 3b, Ln=Pr), are useful as ¹H NMR shift reagents for direct determination of enantiomeric composition of enantiomorphous alcohols, ketones and amines. With these substrates, l-3a induces shift difference similar to that induced by Eu(facam)₃ and Eu(hfbc)₃. However, due to the higher solubility of the chelates l-3a and l-3b in nonpolar organic solvent such as CHCl₃, CCl₄ and only one ¹H signal from l-3a and l-3b is observed, their application as the new chiral shift reagents seems promising. The spectral nonequivalence is also observed for dimethylsulfoxide in the presence of l-3a.     

Macrodistribution of Anodic Dissolution Rate at a Rotating Disk Electrode with Partially Insulated Surface

Macrodistribution of etching rates of a macroscopically nonuniform, partially dipped, rotating disk electrode of low-carbon steel in 1 M NaCl at pH 1 with photoresist insulation and the density of active rectangular holes being 1.6 holes/mm² is studied at dimensionless etching rates i ⁰ _avg /i _l = 0.2–1.1, where i ⁰ _avg is the average current density per active surface and i _l the limiting anodic current density determined by the ionic transport rate. The distribution of the average etching rates in the normal direction is determined by the primary current distribution and is insensitive towards the type of the dissolution rate distribution in a cavity.     

Non-linear transformations of factors in the generalized standard addition method

Summary Experimental designs and non-linearly transformed factors (concentrations of analytes) have been applied in the Generalized Standard Addition Method (GSAM). The relationship betweenN measured analytical signals,R ⁽¹⁾,...,R su(n), and concentrations of standard additions, c1,..., cn, ofn analytes has been approximated by the following polynomial models:The regression coefficientsB in models (1) are calculated from thesimple formulae^{1, 3, 4}.Functionsf _i ^(l) (e.g. linear, parabolic, exponential, hyperbolic or logarithmic) are selected on the basis of the experimentally determined relationshipsR ^(l) (l=1, ...,N) vs.c _i (i=1, ...,n). An example concerns the flame emission photometric determination of Na and Ca. 2² factorial and uncomplete second-degree modelsR ^(l) have been applied expressed by linear and hyperbolic functionsf _i ^(l). The results of determination of Na by GSAM reveal significant improvement of accuracy as compared with the conventional single-component standard addition method.

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Nicht-lineare Transformation von Faktoren bei der verallgemeinerten Standardadditio nsmethode

Zusammenfassung Statistische Versuchsplanung und nicht-linear transformierte Faktoren (Konzentrationen der zu bestimmenden Substanzen) wurden für die verallgemeinerte Standardadditionsmethode eingesetzt. Die Bezeichnung zwischen N gemessenen analytischen Signalen,R ⁽¹⁾,...,R ^(N) und den Konzentrationen der Standardadditionszugaben C_i,..., C ^N , vonn zu bestimmenden Substanzen wurde durch Polynome des folgenden Typs approximiert: (wobei ). Die Funktionenf _i ^(l) (z. B. lineare, parabolische, exponentielle, hyperbolische oder logarithmische) werden auf Basis experimentell bestimmter Abhängigkeiten festgelegtR ^(l) (l=1,...,N) gegen C _i (l=1,...,N). Als Beispiel wird die Flammenemissionsbestimmung von Na und Ca herangezogen. Dabei wurden ein 2² faktorieller Versuchsplan und ein unvollständiges Polynom der Ordnung 2R ^(l) mit linearen und hyperbolischen Funktionenf _i ^(l) angesetzt. Die Resultate der Na-Be-stimmung zeigen durch die Verwendung der verallgemeinerten Standard-addition signifikante Verbesserungen der Resultate gegenüber der Einkomponenten-Standardaddition.

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The author thanks Doc. dr. hab. A. Parczewski for his helpful discussion and editorial comments during the preparation of this paper.     

N-salicylidene- L -glutamatocopper(II) complexes and their antimicrobial effects

Reaction of an ethanolic solution of N-salicylidene- l -glutamatodiaquacopper(II) monohydrate with pyridine, 2-methylpyridine, 4-methylpyridine, 2-aminopyridine, 2,6-diaminopyridine, quinoline, 2-methylquinoline, 4-methylquinoline or 3-methylisoquinoline resulted in solid products containing complexes of the type Cu(sal- l -glu)L with distorted square-pyramidal coordination geometry. The products were characterized by elemental analysis, electronic spectroscopy and magnetic susceptibility measurements. Antimicrobial effects were tested on various strains of bacteria, yeasts and filamentous fungi. To compare the influence of individual ligands (neutral as well as anionic) on their biological activity, copper(II) complexes containing water and a Schiff base derived from salicyldehyde and methyl- and ethyl-esters of l -glutamic acid [Cu(sal-5-Me- l -glu)(H₂O)₂ and Cu(sal-5-Et-l-glu)(H₂O)₂] were also prepared and studied. Bioactivities of complexes tested were found to decrease in the sequence bacteria > filamentous fungi > yeasts.     

Small-angle X-ray study of air-dried elastoidin using three- and one- dimensional correlation functions obtained from slit-smeared intensity

In the present paper an isotropic sample of air-dried elastoidin has been studied considering it to be a non-ideal two-phase densely packed system after the theories by Vonk [1]. The relevant important physical parameters obtained for the sample areE, the width of the transition layer,D, the average periodicity transverse to the layers, S/V, the specific inner surface ₁ and ₂, the volume fraction of two phases, i. e. matter and void,l ₁ andl ₂ the transversal lengths,l _r, the range of inhomogeneity,l _c, the length of coherence and 2E/D, the volume fraction of the transition layer. The values ofE obtained by two approches as given by Vonk [1] and Ruland [2] show but a small difference indicating the correctness of the analysis.     

Die Hydrolyse des Ga3+-Ions; potentiometrische Untersuchungen in 3m NaClO4 bei 60°C

The hydrolysis of the ion Ga³⁺ has been investigated at 60°C by potentiometric titrations in a sodium perchlorate medium of the constant ionic strength 3 m. Solutions of various total gallium concentrations B were alkalified by means of a coulometric technique. The concentrations h of the free hydrogen ions were measured with the aid of a glass electrode. From the experimental data, Z, the average number of OH bound per Ga was calculated. The mathematical analysis of the curves Z(logh)_B is consistent with the following formulation of the hydrolysis reactions with log*β_l = log k₀ k^l = ?1,7 ? 11,55 l.     

Efficient Microbial Conversion of l-Tyrosine to l-DOPA by Brevundimonas sp. SGJ

l-DOPA (3,4-dihydroxyphenyl-l-alanine), the most widely used drug for the treatment of Parkinson??s disease, was produced in buffer using biomass of Brevundimonas sp. SGJ. The effects of enhancers, such as carrageenan, diatomaceous earth, and activated charcoal, on the l-DOPA production were evaluated to obtain the maximum yield. The optimal process conditions found were pH?8, 2?g?l^?1 cell mass, 2?g?l^?1 l-tyrosine, 0.04?g?l^?1 CuSO₄, 0.02?g?l^?1 l-ascorbic acid, 0.5?g?l^?1 carrageenan, and 40?°C temperature. In addition, repeated use of cells resulted in the highest yield of 3.81?g?l^?1 (95.2%) of l-DOPA with utilization of 4?g?l^?1 l-tyrosine, and the highest tyrosinase activity (9,201?U?mg^?1) was observed at 18?h of incubation. Furthermore, the produced l-DOPA was confirmed by high-performance thin-layer chromatography, high-performance liquid chromatography, and gas chromatography?Cmass spectroscopy. Kinetic studies showed significant values of Y _p/s, Q _s, and q _s after optimization of the process. Thus, Brevundimonas sp. SGJ could be an eventual new source for large-scale production of l-DOPA.