Crystal Structure of Tetraphenylarsonium Diisothiocyanatodichlorocobaltate(II)

Abstract  

Tetraphenylarsonium diisothiocyanatodichlorocobaltate(II) was synthesized by metathetic pathway. It crystallizes in the monoclinic space group C 2/c with unit cell parameters, a = 13.510(4) ?, b = 15.873(5) ?, c = 22.809(7) ?, β = 105.743(6)°, V = 1,618(5) ?³ and Z = 4. X-ray crystal structure analysis reveals that the asymmetric unit contains one {(C₆H₅)₄As}⁺ cation and one half {Co(NCS)₂Cl₂}²⁻ anion, the latter lying on a crystallographic twofold axis. While each {Co(NCS)₂Cl₂}²⁻ anion exhibits hydrogen bonding interactions with eight arsonium cations; CH···π interactions between phenyl rings of arsonium cations is restricted to two such centers in the crystal structure.     

Heat capacities of tetraphenyl phosphonium chloride in methanol; ethanol; acetonitrile and water

Measurement of heat capacities Cp at 308.65, 311.65 and 314.65 K have been made for solutions of tetraphenyl phosphonium chloride (TPPC) with methanol, ethanol, acetonitrile and water for dilute solutions (up to 0.1 M) by means of a microcalorimeter (Setaram C-80, model from France). The experimental values of heat capacity for the various solutions have been used to calculate the values of partial molar heat capacities Cp_2,m of the salt in different solutions. The results are studied in relation to the special features of solvations in solutions of the TPPC.     

Confinement-driven weakening of the rotator phase transitions in an alkane through a possible tricritical point

We report calorimetric and X-ray measurements in the R1, R2, and R5 rotator phases of a long chain alkane (n-tetracosane) in bulk and confined to porous matrices (PTFE and Anopore) of two different length scales. Probing the order within and normal to the layers, in the Anopore case having a mesoscopic length scale (200 nm), drastic weakening of the R2-R1 and R1-R5 transitions is seen. The effect on the latter is to such an extent that it results in the first observation of a confinement-driven second order transition in these systems. A significant reduction of the temperature range of the R1 phase is also seen in the Anopore case, a feature argued to cause the change in the order of the transition. Comparisons are also made on the recent prediction of such a point in a Landau model. These findings, while paving a new means of realizing a tricritical point, will lead to better understanding of finite size effects in alkanes.     

Protecting‐Group‐Free Total Synthesis of Isoquinoline Alkaloids by Nickel‐Catalyzed Annulation of o‐Halobenzaldimine with an Alkyne as the Key Step

An efficient short total synthesis of benzo[c]phenanthridine alkaloids including oxyavicine, oxynitidine, and oxysanguinarine is described. Thus, N‐methyl‐o‐bromobenzaldimines 1 b – d undergo regioselective cyclization with 4‐(benzo[d][1,3]dioxol‐5‐yl)but‐3‐yn‐1‐ol ( 2 b ) in the presence of [Ni(cod)₂] (cod=1,5‐cyclooctadiene). In situ oxidation of the resultant isoquinolinium salts gives isoquinolinone derivatives 5 b – d with benzo[d][1,3]dioxol‐5‐yl substitution at the C₃ atom and a (CH₂)₂OH group at the C₄ atom. Later, oxidation of the alcohol group in 5 b – d to the aldehyde moiety followed by acid‐catalyzed cyclization and dehydration completes the total syntheses to give oxyavicine, oxynitidine, and oxysanguinarine in 67, 65, and 60 % yields, respectively. The synthesis requires four steps from o‐bromobenzaldehyde derivatives. Transformations of these alkaloids to the other alkaloids in this family are also discussed herein.     

Experimental and theoretical investigations of adsorption of fexofenadine at mild steel/hydrochloric acid interface as corrosion inhibitor

The present study examines the effect of fexofenadine, an antihistamine drug, on corrosion inhibition of mild steel in molar hydrochloric acid solution using different techniques under the influence of various experimental conditions. Results revealed that fexofenadine is an effective inhibitor and percent inhibition efficiency increased with its concentration; reaching a maximum value of 97% at a concentration of 3.0 × 10⁻⁴ M. Fourier-transform infrared spectroscopy (FTIR) observations of steel surface confirmed the protective role of the studied drug. Polarization studies showed that fexofenadine is a mixed-type inhibitor. The adsorption of the inhibitor on mild steel surface obeyed the Langmuir adsorption isotherm with free energy of adsorption (∆G°_ads) of −40 kJ mol⁻¹. Energy gaps for the interactions between mild steel surface and fexofenadine molecule were found to be close to each other showing that fexofenadine has the capacity to behave as both electron donor and electron acceptor. The results obtained from the different corrosion evaluation techniques are in good agreement.     

Complete <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR signal assignments and chemical shift calculations of four 1,2,4-oxadiazole-based light-emitting liquid crystals

In this article, we describe the complete ¹H and ¹³C NMR signal assignments of four 1,2,4-oxadiazoles possessing light-emitting liquid crystal properties. These results were obtained by using one- and two-dimensional NMR techniques as well as GIAO (PCM) calculations at B3LYP/6-311++G(d,p) level for compounds 1 and 2a–d. The computed values are in good agreement with the ones obtained experimentally. In addition, some previously unexplained thermotropic features of compounds 2a–d could be clarified with the help of the geometry optimization calculations carried out by us.     

Pd-NHC catalyzed cyclopentannulation of diazabicyclic alkenes with ortho-aryl halides

Pd-NHC catalyzed cyclopentannulation of diazabicyclic alkenes with ortho- functionalized aryl halides is described. In all the reactions, a single diastereomer of the cyclopentannulated product is observed, and this reaction is very efficient under microwave irradiation.     

Laser interaction with low-density carbon foam

Experiments were performed with a 15 J/500 ps Nd:glass laser (λ = 1064 nm) focussed to an intensity >10¹⁴ W/cm². X-ray emissions from carbon foam and 5% Pt-doped carbon foam of density 150–300 mg/cc were compared with that of the solid carbon targets. The thickness of the carbon foam was 15 µm on a graphite substrate. X-ray emission was measured using semiconductor X-ray diodes covered with various filters having transmissions in different X-ray spectral ranges. It covered X-ray spectrum of 0.8–8.5 keV range. The X-ray emission in the soft X-ray region was observed to increase to about 1.8 times and 2.3 times in carbon foam and Pt-doped foam, respectively with respect to solid carbon. In hard X-rays, there was no measurable difference amongst the carbon foam, Pt-doped carbon foam and solid carbon. Scanning electron microscope (SEM) analysis demonstrates that foam targets smoothens the crater formed by the laser irradiation.