Complexation with diol host compounds. Part 14. Inclusion compounds of 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl with acetonitrile,cyclohexanone, di-n-propylamine and dimethylformamide

Abstract

The structures of the inclusion compounds of 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl (H) with acetonitrile (1) (1:1), cyclohexanone (2) (1:2), di-n-propylamine (3) (1:1) and dimethylformamide (4) (1:2) are reported. Crystal data: (1) monoclinic, P2₁/c with a=10.500(3), b=15.598(3), c=18.344(3) Å, β=96.66(2)°, Z=4, D _C=1.24 g cm^?3. (2) monoclinic, P2₁/c with a=13.980(3), b=11.768(5), c=23.49(1) Å, β=98.77(3)°, Z=4, D_c =1.24 g cm^?3. (3) monoclinic, C2/c with a=29.57(1), b=13.485(4), c=18.17(1) Å, β=107.94(4)°, Z=8, D _C=1.16 g cm^?3. (4) monoclinic, C2/c with a=30.123(9), b=13.391(6), c=19.177(6) Å, β=111.23(4)°, Z=8, D _C=1.22 g cm^?3. Final R values for the four structures were 0.065, 0.120, 0.084 and 0.107 for 2937, 2830, 2071 and 3769 reflections, respectively. The host conformation is quite rigid and does not appear to be influenced by the shape and size of the guests studied. The host is held in a spiral conformation by means of an intramolecular hydrogen bond. In addition, host-guest hydrogen bonds are observed in all structures. Thermal analysis was used to evaluate the strength of binding of the guest molecules and confirmed that (1) is the most stable of the four compounds studied.     

Electrochemical Modification of Gold Electrodes with Azobenzene Derivatives by Diazonium Reduction

An electrochemical study of Au electrodes electrografted with azobenzene (AB), Fast Garnet GBC (GBC) and Fast Black K (FBK) diazonium compounds is presented. Electrochemical quartz crystal microbalance, ellipsometry and atomic force microscopy investigations reveal the formation of multilayer films. The elemental composition of the aryl layers is examined by X‐ray photoelectron spectroscopy. The electrochemical measurements reveal a quasi‐reversible voltammogram of the Fe(CN)₆^3?/4? redox couple on bare Au and a sigmoidal shape for the GBC‐ and FBK‐modified Au electrodes, thus demonstrating that electron transfer is blocked due to the surface modification. The electrografted AB layer results in strongest inhibition of the Fe(CN)₆^3?/4? response compared with other aryl layers. The same tendencies are observed for oxygen reduction; however, the blocking effect is not as strong as in the Fe(CN)₆^3?/4? redox system. The electrochemical impedance spectroscopy measurements allowed the calculation of low charge‐transfer rates to the Fe(CN)₆^3? probe for the GBC‐ and FBK‐modified Au electrodes in relation to bare Au. From these measurements it can be concluded that the FBK film is less compact or presents more pinholes than the electrografted GBC layer.     

Electrostatic conveyer for excitons

We report on the study of indirect excitons in moving lattices-conveyers created by a set of ac voltages applied to the electrodes on the sample surface. The wavelength of this moving lattice is set by the electrode periodicity, the amplitude is controlled by the applied voltage, and the velocity is controlled by the ac frequency. We found the dynamical localization-delocalization transition for excitons in the conveyers and determined its dependence on exciton density and conveyer amplitude and velocity.     

Integral closures and weight functions over finite fields

Curves and surfaces of type I are generalized to integral towers of rank r. Weight functions with values in N^r and the corresponding weighted total-degree monomial orderings lift naturally from one domain R_j−1 in the tower to the next, R_j, the integral closure of R_j−1[x_j]/φ(x_j). The qth power algorithm is reworked in this more general setting to produce this integral closure over finite fields, though the application is primarily that of calculating the normalizations of curves related to one-point AG codes arising from towers of function fields. Every attempt has been made to couch all the theory in terms of multivariate polynomial rings and ideals instead of the terminology from algebraic geometry or function field theory, and to avoid the use of any type of series expansion.     

k-alternating knots

A projection of a knot is k-alternating if its overcrossings and undercrossings alternate in groups of k as one reads around the projection (an obvious generalization of the notion of an alternating projection). We prove that every knot admits a 2-alternating projection, which partitions nontrivial knots into two classes: alternating and 2-alternating.     

Substitution derivatives of the heteronuclear cluster RuOs3(μ-H)2(CO)13: Monosubstituted group 15 derivatives

Tertiary group 15 ligand monosubstituted derivatives of the heteronuclear cluster RuOs₃(μ-H)₂(CO)₁₃ have been prepared and their solid state and solution structures examined. A number of isomeric structural types have been identified in solution, and these appear to be correlated to disorder in the solid state. Hydride fluxionality and restricted rotation about the metal-phosphorus bond have also been observed.     

Some arithmetical questions in the theory of the base

Sunto. Vengon studiate, dal punto di vista aritmetico, alcune varietà algebriche possedenti trasformazioni birazionali in sè      

On the Cutoff Wavelength of Rectangular-Shaped Microshield Line by Edge Element Method

In this paper, the cutoff characteristic of rectangular-shaped microshield transmission line has been analysed by edge element method. Dependence of cutoff wavelengths on the thickness of metallic signal strip, dielectric constant of dielectric substrate and the width of the rectangular-shaped ground conductor are presented in tabular form. Numerical results in this paper have important values in design of rectangular-shaped microshield lines in microwave and millimeter wave integrated circuits.     

Effectiveness of a Mathematics Methods Course in Reducing Math Anxiety of Preservice Elementary Teachers

In an attempt to find ways of reducing the mathematical anxiety of preservice elementary teachers, three cases were investigated. The first was a section of mathematics for elementary teachers taught in a very traditional manner, and the second was the same course taught in a manner consistent with the recent recommendations of the National Council of Teachers of Mathematics. The third case included two sections of a methods course which covered the same mathematical content, as well as addressing how it should be taught to children. The Mathematics Anxiety Rating Scale for Adults was administered before and after the courses. No significant reduction of anxiety was measured in either mathematics section, but both sections of the methods course showed a significant reduction.