Comparative Study Of Complexes Research Articles

Comparative study of complexation between cyclodextrins and xylazine using 1H NMR and molecular modelling methods

Structure determination of the inclusion complexes of Xylazine (XYL) as the guest molecule with α-, HP-β- and γ-cyclodextrins (CDs) as host molecules was taken up, along with structural comparison between the inclusion complexes formed in each case. On the basis of our previous studies, a method comprising of experimental studies integrated with computational approach including molecular mechanics (MM) studies and molecular dynamics (MD) studies, was employed which provided exact structure of the inclusion complexes. 2D ROESY interactions were studied in each case, which confirmed formation of the inclusion complexes and showed parts of the guest encapsulated in the cavity. Only aromatic protons of XYL displayed interactions, which signified inclusion of the aromatic ring in the cavity in all the complexes. Considering the ROESY contacts, MM studies were performed for both the wide as well as narrow ends of the cavity for the three inclusion complexes. Further, to complement these structures, MD studies were performed for the inclusion complexes formed in each case. Several MD simulations were performed with different relative positions of the host and guest that determined structures of the ensembles consistent with the ROESY studies. This study has demonstrated the application of this method in the accurate structure establishment of the inclusion complexes.

An explorative investigation of functional differences in plantar center of pressure of four foot types using sample entropy method

In the study of biomechanics of different foot types, temporal or spatial parameters derived from plantar pressure are often used. However, there is no comparative study of complexity and regularity of the center of pressure (CoP) during the stance phase among pes valgus, pes cavus, hallux valgus and normal foot. We aim to analyze whether CoP sample entropy characteristics differ among these four foot types. In our experiment participated 40 subjects with normal feet, 40 with pes cavus, 19 with pes valgus and 36 with hallux valgus. A Footscan® system was used to collect CoP data. We used sample entropy to quantify several parameters of the investigated four foot types. These are the displacement in medial–lateral (M/L) and anterior–posterior (A/P) directions, as well as the vertical ground reaction force of CoP during the stance phase. To fully examine the potential of the sample entropy method for quantification of CoP components, we provide results for two cases: calculating the sample entropy of normalized CoP components, as well as calculating it using the raw data of CoP components. We also explored what are the optimal values of parameters m (the matching length) and r (the tolerance range) when calculating the sample entropy of CoP data obtained during the stance phases. According to statistical results, some factors significantly influenced the sample entropy of CoP components. The sample entropies of non-normalized A/P values for the left foot, as well as for the right foot, were different between the normal foot and pes valgus, and between the normal foot and hallux valgus. The sample entropy of normalized M/L displacement of the right foot was different between the normal foot and pes cavus. The measured variable for A/P and M/L displacements could serve for the study of foot function.

Platonism

This paper explores the reception of Gellner’s historical sociology among students of pre-modern societies and the Greco-Roman world in particular and asks how his thought is still relevant to the field. This involves discussion of recent trends in world history as well as new comparative work on ancient state and elite formation. A main contention of the paper is that Gellner’s sociological reading of Plato and his politics may be one of the most interesting modern interpretations of the ancient Greek thinker on offer and one which can serve as a fruitful framework for the comparative study of complex, pre-industrial societies.

Comparative Study of Complexity, Entropy and Correlations of Natural Written Texts Produced by Human Brain and DNA “Texts” that Create Human Being

Every sample of a DNA sequence, despite being created in the process of evolution, can be mathematically considered as an example selected from an ensemble of realizations of a random discrete process with complex statistical structure. This point of view allow us, digressing from biological properties of DNAs, to explore their statistical characteristics with the help of standard mathematical methods: calculate their correlators, the moments of different order, the entropy, etc. For better clearness one can compare the calculated characteristics with other similar random correlated sequences. Here we compare the complexity (expressed in terms of the correlation and entropy) of DNAs and literary texts, keeping in mind the nearly philosophical question: what is, from the mathematical point of view, more complex organized object.

Comparative Study of Complexity in Streetscape Composition

Comparative Study of Complexity in Streetscape Composition

Comparative Study of Complexity in Algerian and Japanese Street Nightscapes(Summaries of the 16^<th> Annual Meeting)

Comparative Study of Complexity in Algerian and Japanese Street Nightscapes(Summaries of the 16^<th> Annual Meeting)

Spectroscopic and electrochemical properties of cyclopalladated complexes derived from 2,3-diphenylpyrazine

A comparative study of complexes [Pd(dphpz)(N∧N)]PF6 [dphpz− is the deprotonated form of 2,3-diphenylpyrazine; (N∧N) is ethylenediamine (En), 2,2′-bipyridine (bpy), o-phenanthroline (phen), dipyrido[a,c]phenazine (dppz), 6,7-dicyanopyrido[f,h]quinoxaline (dicnq)] was made, using 1H NMR, electronic absorption, and emission spectroscopy, and also cyclic voltammetry. Steric interaction of the dphpz− phenyl rings leads to significant proton shielding in the carbanionic moiety of the cyclometallated ligand. Introduction of heterocyclic diimines instead of ethylenediamine decreases the desheilding of the dphpz− protons adjacent to the coordination center. Irrespective of the nature of the N∧N ligands, the cyclopalladated complexes are characterized by specific parameters of photo-and electrostimulated electron transfer processes involving the Pd(dphpz) orbitals, namely, by the long-wave absorption band with λmax 395±6 nm and e (2.2±1.2) × 103 1 mol−1 cm−1, the vibrationally structured low-temperature (77 K) luminescence resulting from the spinforbidden optical transfer from the excited to the ground state of the complex (energy E 00 19.27±0.07 kK, lifetime τ 160±30 μs), and the one-electron electroreduction wave with E 1−(2.0±0.1)V. For the [Pd(dphpz)·(N∧N)]+ complexes containing diazine derivatives of phenanthroline (dppz, dicnq), the degradation of the photoexcitation energy from two electronically excited states can occur as isolated process with successive transfer of electrons to the π orbitals localized on the remote moieties: [Pd(dphpz)] and diazine fragments of the N∧N ligands.

Comparative study of complex N- and O-bearing molecules in hot molecular cores

We have observed several emission lines of two Nitrogen-bearing (C2H5CN and C2H3CN) and two Oxygen-bearing (CH3OCH3 and HCOOCH3) molecules towards a sample of well-known hot molecular cores (HMCs) in order to check whether the chemical differentiation seen in the Orion-HMC and W3(H_2O) between O- and N-bearing molecules is a general property of HMCs. With the IRAM-30m telescope we have observed 12 HMCs in 21 bands, centered at frequencies from 86250 to 258280 MHz. The rotational temperatures obtained range from ~100 to ~150 K in these HMCs. Single Gaussian fits performed to unblended lines show a marginal difference in the line peak velocities of the C2H5CN and CH3OCH3 lines, indicating a possible spatial separation between the region traced by the two molecules. On the other hand, neither the linewidths nor the rotational temperatures and column densities confirm such a result. By comparing the abundance ratio of the pair C2H5CN/C2H3CN with the predictions of theoretical models, we derive that the age of our cores ranges between 3.7 and 5.9x10^{4} yrs. The abundances of C2H5CN and C2H3CN are strongly correlated, as expected from theory which predicts that C2H3CN is formed through gas phase reactions involving C2H5CN. A correlation is also found between the abundances of C2H3CN and CH3OCH3, and C2H5CN and CH3OCH3. In all tracers the fractional abundances increase with the H_2 column density while they are not correlated with the gas temperature.

Amino-substituted gem-diphosphonic acids: structures of complexes with divalent metal cations in aqueous solutions

A comparative study of complexation of acids R2N(CH2)nCR"(PO3H2)2 (R = H or Me; R" = OH or H; n = 1 or 2) with the Ca2+, Mg2+, Zn2+, and Cu2+ cations in aqueous solutions was carried out by vibrational (IR and Raman) and electronic spectroscopy using the data of ESR spectroscopy and conformational analysis (molecular mechanics). The MOPCPO chelate ring is formed in all ML and MHL complexes. The involvement of the N atom in coordination was found only in the Cu2+ complexes and is determined by the structure of the ligand. The relationship between the stability constants and the structures of the complexes in aqueous solutions is analyzed.

Three-dimensional delocalization in tris(1,2-dithiolenes)

Tungsten tris(1,2-dithiolene) complexes [W(S 2 C 2 R 1 R 6 )(S 2 C 2 R 2 R 5 )(S 2 C 2 R 3 R 4 )] (R 4,5,6 = H or Ph; R 1,2,3 = para-substituted Ph), have been found to exhibit properties ( 1 H NMR, UV/VIS, IR spectral) closely related to each other through Hammett constant σ p + , indicating extensive delocalization and conjugation. A comparative study of complexes containing differently substituted dithiolenic rings showed that the electron delocalization is not confined within each dithiolenic ring separately, but involves all of them, i.e. it is three dimensional. This is further supported by a NMR and/or UV/VIS study of the effect of water and acid on the dimethylamine derivative. The oxidation number was assigned by recording the NMR spectra of the metal nuclei; the metals have effectively been stripped of their valence electrons; which are placed on the ligands. The non-planar ‘aromaticity' of the dithiolenes differs from the familiar flat organic aromaticity since it involves mixing of σ and π bonding.

Kinetics of substitution reactions of Fe II-phosphine complexes with Cl −, Br − and SCN − in acetonitrile. A comparative study of complexes containing bidentate and tripodal phosphines

The kinetics of formation of FeLX + complexes from FeLan 2 2+ and X − [L  P(CH 2CH 2PPh 2) 3, N(CH 2CH 2PPh 2) 3, (Ph 2PCH 2CH 2PPh 2) 2; X  Cl, Br, SCN; an = acetonitrile] has been studied in acetonitrile at 25.0°C and Et 4NBF 4 (0.05 mol dm −3). All the reactions seem to go through initial substitution of one coordinated acetonitrile by X − to form FeLX +, although in some cases the reaction continues to the formation of FeLX 2. The values obtained for the rate constants corresponding to the first substitution process do not show large differences and indicate that the three FeL(an) 2 2+ complexes have a very similar behaviour, except that the N(CH 2CH 2PPh 2) 3 complex is intrinsically more labile towards substitution of coordinated acetonitrile. The stability quotients for the formation of FeLX + complexes have been also determined and they suggest some degree of steric selectivity in the reactions of [FeP(CH 2CH 2PPh 2) 3(an) 2] 2+ with X −.