The infrared spectra and theoretical calculations of frequencies of fac-tricarbonyl octahedral complexes of manganese(I)

The carbonyl stretching frequencies in the infrared spectra of 38 fac-tricarbonyl octahedral complexes of manganese(I) prepared in this laboratory were determined. These complexes may be grouped into three types: (a) neutral complexes of the structure (CO)(3)Mn(P-P)Z where P-P represents depe, dppe, or dppp, and Z represents various anionic functional groups bonded to the manganese; (b) ionic complexes of the structure [(CO)(3)Mn(P-P)Z](+)BF(4)(-) where Z represents various neutral molecules possessing one phosphorous, nitrogen, or oxygen atom coordinated to the manganese; (c) complexes of the structure (CO)(3)Mn(pn)Z where the chelating pn represents 1,1-diphenylphosphino-2,2-dimethylaminoethane, Ph(2)PCH(2)CH(2)NMe(2). All of these complexes show three carbonyl stretching modes (2A' + A"). The effects on the frequencies of these modes induced by both the various Z groups and the various ligands are discussed. Theoretical calculations (B3LYP/6-31G) with optimization of the full molecule make it possible to distinguish between the three stretching modes and to make unambiguous assignments of appropriate symmetry species to each.     

Ab initio investigation of the hydration of the tetrahedral perchlorate, perbromate, selenate, arsenate, and vanadate anions

The geometries, energies, and vibrational frequencies of various isomers of XO(4)(m-)(H2O)n, x = Cl, Br, Se, As, V; n = 0-6, m = 1-3 are calculated at various levels up to MP2/6-31+G*. These properties are studied as a function of increasing cluster size. The experimental and theoretical vibrational spectra are compared where available.     

HPLC retention behavior on hydride-based stationary phases

Two stationary phases attached to a silica hydride surface, cholesterol and bidentate C18, are investigated with a number of pharmaceutically related compounds in order to illustrate the various retention mechanisms that are possible for these bonded materials. The test solutes range from hydrophilic to hydrophobic based on log P (octanol/water partition coefficient) and pKa values. The mobile phases consist of acidified (formic and perchloric acid) water/methanol or water/ACN mixtures. Of particular interest are the high organic content mobile phase compositions where the retention would increase if the bonded material was operating in the aqueous normal phase (ANP) mode. Plots of retention factor (k) versus mobile phase composition are used to elucidate the retention mechanism. A number of examples are presented where solutes are retained based on RP, ANP, or dual retention mechanisms. The silica hydride-based stationary phases can also retain compounds in the organic normal phase.     

Filtration of deformable emulsion droplets

Oil-in-water (o/w) emulsions of different droplet size were filtered on membranes of various pore sizes to investigate the growth and behaviour of o/w filter cakes. The cake desorptivity S and the filter membrane resistance R were measured at various filtration pressures P. The variation of S with P shows that filter cake oil droplets of radius a are effectively rigid for P < gamma/a and fully deformable for P > gamma/a, where gamma is the oil-water interfacial tension. For the largest P, when S became P-independent, the filter cake remained water-permeable as expected from theory.     

Renal function study with 111In-DTPA--in comparison with 99mTc-DTPA

Technetium-99m-diethylene-triamine-penta-acetic acid (DTPA) and 111In-DTPA were injected simultaneously into 21 patients with various levels of renal function. Scintiphoto, camera data renograms and clearance values (plasma sampling) were obtained for each patient. The mixed isotope scintiphoto images were of intermediate quality and the images with 111In-DTPA were apparently inferior to those with 99mTc-DTPA. These equations were obtained: (1) y = 0.30 + 0.91 x (coefficient of correlation r = 0.98) where x is the value at T peak (time of maximum count on renogram) obtained with 99mTc-DTPA and where y is the value at T peak with 111In-DTPA. (2) y = -0.09 + 1.006 x (r = 0.99) where x is the value at T3/4 (time interval between the time of maximum count to the time of 3/4 of maximum count on renogram) and where y is the value at T3/4 obtained with 111In-DTPA. (3) y = -0.01 + 1.007 x (r = 0.98) where the x and y values were for the excretion ratios (counts at 20 min/maximum counts on renogram). (4) y = 0.81 + 0.98 x (r = 0.99) where x and y are the clearance values.     

The influence of solvent polarity on the tetrahedral-octahedral equilibrium of Co(II)complexes with 3,5-dimethylpyrazole

The configuration equilibrium:

(where DMPz = 3,5-dimethylpyrazole), has been studied spectrophotometrically in various non-aqueous polar solvents. The influence of solvent polarity on the K value has been investigated. Solvation studies have also been carried out on the tetrahedral species Co(SCN)₂(DMPz)₂, and the results are interpreted in terms of the polarity of the various solvents.     

Ab initio vibration—rotation coupling constants and the equilibrium geometries of NCCN and CNCN

The equilibrium geometries of NCCN and CNCN were calculated from experimental ground-state rotational constants and ab initio values for the vibration—rotation coupling constants. For NCCN, R_1e(NC) = 1.1578(5) Å and R_2e(CC) = 1.3839(5) Å were obtained, where estimated error bars are given in parentheses. The calculated equilibrium bond lengths of CNCN are R_1e(CN) = 1.1813(5) Å, R_2e(NC) = 1.3116(5) Å and R_3e(CN) = 1.1581(5) Å. Ground-state rotational and centrifugal distortion constants are predicted with high accuracy for various isotopomers of NCCN.     

Xerographic property of azo/TiOPc composites in double-layered photoreceptor

The xerographic property has been studied in the double-layered photoreceptor device where azo/TiOPc composite is used as the charge-generation material (CGM) and p-diethylaminobenzaldehyde--naphthalenylphenylhydrazone (DENPH) or p-dimethylaminobenzaldehyde diphenylhydrazone (DMDPH) is used as the charge-transportation material (CTM) under the exposure of various spectral regions. The results show that the azo/TiOPc composites exhibit high photosensitivity not only in the visible and near-infrared regions, but also in the entire spectral ranges, indicating the co-enhancement effect. The UV–VIS spectra suggest that the absorption spectra of the azo/TiOPc composites are broadened. The composite mechanism is investigated through X-ray diffraction and ESR.     

Efficient Synthesis of Homoallylic Alcohols/Amines from Allyltributylstannane and Carbonyl Compounds/Imines Using Iodine as Catalyst Under Acetic Acid–Water Medium

This paper describes a general method for the synthesis of homoallylic alcohols and amines by nucleophilic addition reaction of allyltributylstannane to carbonyl compounds and aldimines where iodine acts as a catalyst in H₂O/acetic acid (1:1) medium. Only 10 mol% of I₂ is required for various organic transformations. By using this process, various homoallylic alcohols and amines are produced in good to excellent yields.     

Adsorption of Toluene and Water over Cationic-Exchanged Y Zeolites: A DFT Exploration

In this study, density functional theory (DFT) calculations have been performed to investigate the adsorption mechanisms of toluene and water onto various cationic forms of Y zeolite (LiY, NaY, KY, CsY, CuY and AgY). Our computational investigation revealed that toluene is mainly adsorbed via π–interactions on alkalis exchanged Y zeolites, where the adsorbed toluene moiety interacts with a single cation for all cases with the exception of CsY, where two cations can simultaneously contribute to the adsorption of the toluene, hence leading to the highest interaction observed among the series. Furthermore, we find that the interaction energies of toluene increase while moving down in the alkaline series where interaction energies are 87.8, 105.5, 97.8, and 114.4 kJ/mol for LiY, NaY, KY and CsY, respectively. For zeolites based on transition metals (CuY and AgY), our calculations reveal a different adsorption mode where only one cation interacts with toluene through two carbon atoms of the aromatic ring with interaction energies of 147.0 and 131.5 kJ/mol for CuY and AgY, respectively. More importantly, we show that water presents no inhibitory effect on the adsorption of toluene, where interaction energies of this latter were 10 kJ/mol (LiY) to 47 kJ/mol (CsY) higher than those of water. Our results point out that LiY would be less efficient for the toluene/water separation while CuY, AgY and CsY would be the ideal candidates for this application.     

Adsorption of mixtures of nonionic sugar-based surfactants with other surfactants at solid/liquid interfaces I. Adsorption of n-dodecyl-beta-D-maltoside with anionic sodium dodecyl sulfate on alumina

Sugar-based surfactants can be synthesized from renewable materials and are environmentally benign. They have some unique solution and interfacial properties and have potential applications in a wide variety of processes, and there is a need for corresponding information on their behavior at various interfaces. In this study, co-adsorption of nonionic sugar-based n-dodecyl-beta-D-maltoside (DM) and anionic sodium dodecyl sulfate (SDS) on alumina was studied as a function of mixing ratios and solution pHs. It is found that at solid-liquid interface, depending on the solid type and the solution conditions, there are various interactions that dictate synergy or antagonism. At pH 6 where alumina is positively charged, marked synergistic effects between DM and SDS were observed, while at pH 11 where alumina is negatively charged, SDS shows antagonistic adsorption effects with DM. The ratios of surfactant components on solids change as a function of surfactant structure and concentrations as well, indicating various interactions at solid/liquid interface under different conditions that can be utilized for many industrial processes.     

VB/MM--the validity of the underlying approximations

Two recently developed methods, VB/MM and density embedded VB/MM (DE-VB/MM), are compared, and their respective approximations are examined. The two methods combine valence-bond (VB) calculations with molecular mechanics (MM) and aim to allow VB analysis of reactions in large biological environments. Furthermore, the two methods utilize two major approximations regarding both the overlap and the reduced resonance integral between the various VB configurations. The difference between the two methods, however, is that VB/MM employs these approximations for the overall interaction of the reacting fragments with their surrounding, whereas DE-VB/MM employs the approximations only with regards to the van der Waals (VdW) interactions whereas the electrostatic interactions are calculated rigorously at the quantum level. The approximations that lay the grounds for the two methods involve the assumption that the overlap between the VB configurations and the respective reduced resonance integral are both invariant to the environment. Similar approximations are utilized in several other VB-based QM/MM methods. However, although extensively used, these approximations were never rigorously proved. Here, we exploit the development of the DE-VB/MM method to numerically examine the approximations by calculating the accurate as well as the approximated values of overlap and reduced resonance integral for systems where the environment involves only electrostatic interactions. The quality of the approximations is examined together with their effect on the absolute energies, the wave function, and the overall energetics. Three test cases are chosen, the dissociation of CH 3F and LiF and the identity S N2 reaction. It is shown that the approximations are usually good with the exception of cases where extreme changes are expected in the wave function. Furthermore, the impact of the approximations on the overall wave function and the overall energetics is found to be quite small. It is concluded that VB/MM, where the approximations are used more extensively, can serve as the first method of choice.     

Classical and knudsen thermogravimetry to check states and displacements of water in food systems

Water states and displacements can be investigated with thermogravimetry (TG) either in its classical or in the Knudsen version (where standard pans are replaced with Knudsen cells). The case of wheat flour dough is considered in various steps of bread making, namely, mixing, proofing, baking, staling. The split of DTG signals into various components (gaussian functions) support the assumption that the overall dough water is partitioned into various fractions. Few comments are devoted to water displacements during freezing.This revised version was published online in November 2005 with corrections to the Cover Date.     

Determination of borate ion-pair stability constants by potentiometry and non-approximative linearization of titration data

Borate anions, B(OH)(-)(4), are known to associate with alkali and alkaline-earth metal cations in sea-water. The borate cation ion-pairs are of the general form MB(OH)((n-1)+)(4), where M(n+) is the cation. In this work, the cation borate stability constants (K*(MB)) have been evaluated for Na(+), Li(+), Mg(2+), Ca(2+) and Sr(2+) where K*(MB) = [MB(OH(4))((n-1)+)]/[M(n+)][B(OH)(-)(4)]. The K*(MB) values were obtained from values found for the stability constant of boric acid (K*(B)) in various electrolyte media at 25 degrees and an ionic strength of 0.7. Acid-base potentiometric titrations were performed in the electrolyte media with a standard Pt/H(2) electrode and a junctionless Ag/AgCl reference electrode to monitor the emf. A non-approximative equation was used to linearize the titration data. The values obtained were: K*(Lib) = 0.89 +/- 0.02, K*(NaB) = 0.44 +/- 0.01, K*(MgB) = 13.6 +/- 0.7, K*(CaB) = 11.4 +/- 0.15, K*(SrB) = 3.47 +/- 0.06. The values for K*(MB) correlate with the charge-density parameter z(2)/(r + 0.85), where r is the radius of the cation. The speciation of boron in sea-water was predicted from the K*(MB), data for the major cations present.     

Water dispersible hydroxyapatite nanoparticles functionalized by a family of aminoalkyl phosphates

A series of aminoalkyl phosphates (AAP-n, with carbon number n ranging from 2 to 6) are used as surface modifiers to prepare hydroxyapatite hydrocolloids. The resulting nanoparticles (Cn-HA) possess a coreshell structure where an ionized layer of calcium-(AAP-n) complex [⁺H₃N-(CH₂)_n-OPO₃Ca] encapsulates each hydroxyapatite core. Long-term colloidal stability is achieved due to the electrostatic repulsion among the suspending particles. The incorporation of AAP-n results in a preferential crystal growth along c-axis, showing an increasing aspect ratio of particles from C2-HA to C6-HA. Preliminary cell culture using osteoblast-like MG63 cells shows no cytotoxicity associated with the as-prepared Cn-HA particles. The functional amino groups around the nanoparticles could be used to graft various organic chains to prepare homogeneous HA/polymer composites as bone grafting materials.     

高价金属离子在结晶锑酸-磺胺偶氮氯膦浸渍板上的薄层色谱研究

本文报导了一种新的薄层色谱法,研究了稀土(Ⅲ)、钛(Ⅳ)、锆(Ⅳ)、铌(Ⅴ)和铀(Ⅳ)的TLC行为,有效地分离了一系列二元及三元混合物.方法简便、快速、直观.根据实验结果,推荐了镧系元素的原子序数(Z)、离子裸半径(r°)与R_f值的经验公式.计算了在各种展开剂中曲线的截距、斜率和线性相关系数(r).     

Stability and bioequivalence studies of two marketed formulations of coenzyme Q10 in beagle dogs.

Coenzyme Q10 (CoQ10), a highly lipophilic compound present in the inner mitochondrial membrane, is essential for production of cellular energy in the form of ATP. CoQ10 is used as an antioxidant and also in the treatment of various cardiovascular disorders. The relative bioavailabilities of powder filled capsule (I) and oil-based formulation (II) of CoQ10 were compared in beagle dogs in an open, randomized, multiple dose, cross-over design. Poor and slow absorption characteristics were observed for both the formulations. The AUC, Cmax, and Tmax for formulation I and II are comparable (p < 0.05) where the values for formulation I are 22.84 +/- 6.3 micrograms ml-1 h, 0.51 +/- 0.11 microgram/ml, and 6.1 +/- 2.0 h whereas the values for formulation II are 24.32 +/- 5.6 micrograms ml-1 h, 0.55 +/- 0.16 microgram/ml, and 6.6 +/- 2.3 h, respectively. Stability of CoQ10 at various temperature and humidity conditions and its photostability were studied. Various antioxidants were evaluated to determine the type and amount of antioxidant(s) required to improve the stability of CoQ10. Large extent of degradation was observed at 45 degrees C and 55 degrees C. The effect of humidity conditions on degradation was insignificant. Among the various antioxidants studied, mixture of ascorbic acid (5%) and EDTA (0.1%) offered better protection than phenolic antioxidants such as butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT), or propyl gallate (PG). Further, increasing concentrations of phenolic antioxidants (from 0.1 to 0.3%) accelerated the degradation.     

Ac voltammetric and square wave voltammetric study of the self-assembled monolayers of thiol-functionalized viologen derivative

Electroactive self-assembled monolayers (SAMs) containing viologeu group are formed through the adsorption of thiol-functionalized viologen compound CH3(CH2)9V2+(CH2)8SH,where V2+ is N,N'-diaIkylbipyridinium (i.e.a viologen group),onto gold electrodes from methanol/water solution and its electrochemical behavior is investigated by Ac voltammetry and square wave voltam-metry,which have the high sensitivity against background charging.The viologen SAM formed is a sub-monolayer and the normal potentials corresponding to the two successive one-electron transfer processes of the active centers (viologen) are-360 mV and-750 mV (vs.Ag/AgCl) in 0.1mol/L phosphate buffer solutions (pH 6.96) respectively,and the standard electron transfer rate constant is 9.0s-1 The electrochemical behavior of this SAM in various solutions has been preliminarily discussed.     

Modulation of aggregation behavior of amphiphilic drug AMT under the influence of polymer molecular weight and composition

The purpose of this study was to determine the aggregation behavior of amphiphilic drug amitriptyline hydrochloride (AMT) and to search for means which boost/suppress the aggregation behavior. Polyethylene glycols (PEGs) nonionic polymers (which are used as pharmaceutical excipients) of varying molecular weights from 400 to 35,000 were tested. To know their effect on the micellization and interfacial behavior of the drug, the critical micelle concentration (CMC) and critical aggregation concentration (CAC) were determined in presence of various polymers by tensiometric and conductivity methods. The CAC values were found to decrease while the CMC values increased with increase in the polymer concentration. The thermodynamic parameters were evaluated where ΔG°(mic) and ΔG°(agg) are found to be negative, confirming the feasibility of interaction between AMT and polymers.     

Solvatochromaticity and pH dependence of the electronic absorption spectra of some purines and pyrimidines and their metal complexes

The solvatochromic responses of uric acid (Ua), 6-amino-2-thiouracil (ATU) and a series of their complexes dissolved in ten solvents of different polarity have been measured. The solvent-dependent UV/Vis spectroscopic absorption maxima, λ(max), are assigned to the corresponding electronic transitions and analyzed using SPSS program, regression analysis and Kamlet and Taft methods. The observed solvatochromism is discussed using various solute-solvent interaction mechanisms. The electronic absorption spectra of ATU were investigated in aqueous buffer solutions of varying pH and utilized for the determination of dissociation constants. The ranges of pH, where individual ionic species are predominant have been determined.