Processable heat-resistant polymers—XVI: Polyamideimidesulphonamides

Polyamideimides having sulphonamide linkages were prepared by low temperature polycondensation of 2-sulphoxy-1,3-dioxoisoindoline-5-carboxylic acid with various diamines in the presence of thionyl chloride. The polymers were soluble in highly polar solvents. The solubility parameters of the polymers were calculated from Small's group contributions. Isothermogravimetric data indicated that the polymers were fairly thermostable.     

Size effect on different impurity levels in semiconductors — A comment

The results obtained for the strain energy corrections to O and Se donor ionization energies in GaP (at the P site) by Van Cong et al. in a recent communication [1] are shown to be fortuitous. It is pointed out that the results of Weinreich [2] are of the correct order unlike the results of Van Cong et al. which are too high in many cases and are not in agreement with experiment.     

Formation of borosilicate glasses from silicon alkoxides and metaborate esters in dry non-aqueous solvents

The reaction of metaborate esters (RO)₃B₃O₃ [R = Me, Et, ClCH₂CH₂–, Cl₃CCH₂–, ClCH₂CH₂CH₂–, (ClCH₂)₂CH–] with Si(OR)₄ (R = Me, Et), either neat or in dry propan-2-one or dry THF at room temperature, led to gels which when dried and heated in air for 20 mins at 600°C afforded borosilicate glasses in high ceramic yields. The dried gels and glasses were characterized by elemental analysis, TGA, IR, and powder XRD, and solid-state MAS ²⁹Si and ¹¹B NMR. The gelling reaction was investigated by solution ¹¹B and ²⁹Si NMR. These NMR studies indicated B–O–Si reaction intermediates and a mechanism involving alkoxy exchange and various condensation/elimination reactions of the borosilicate esters have been proposed.     

Spectrophotometric determination of mercury in environmental sample and fungicides based on its complex with o-carboxy phenyl diazoamino p-azobenzene

In the present method a new reagent o-carboxyphenyl diazoamino p-azobenzene has been synthesised for the determination of mercury spectrophotometrically. The method is based on the reaction of mercury with the reagent in alkaline medium where the reagent is in the aci-form. The purple violet coloured dye-mercury complex showed an absorption maxima at 540 nm. Beer's law is valid over the concentration range of mercury from 0.08 to 0.8 mug ml(-1) (0.08-0.8 ppm). The molar absorptivity and Sandell's sensitivity were found to be 2.22x10(5) mol(-1) cm(-1) and 0.0009 mug cm(-2), respectively. The method has been successfully applied to the determination of mercury in air, water, soil and fungicide samples.     

Thermal studies of 2-methyl-1, 2-propanediamine complexes of nickel(II) in the solid state

Summary The complexes, [NiL₂]Br₂ (L=2-methyl-1, 2-propanediamine), [NiL₂(H₂O)₂]SeO₄·2H₂O, [NiL₂]X₂·2H₂O (X=0.5SO₄ or 0.5SeO₄) and [NiL₂(NCS)₂] have been prepared and investigated thermally. Upon heating, [NiL₂]Br₂ exhibits reversible thermochromism from yellow to blue: [NiL₂]X₂·2H₂O (X=0.5SO₄ or 0.5SeO₄) undergoes dehydration accompanied with irreversible thermochromism from yellow to blue yielding [NiL₂X₂], whereas [NiL₂(H₂O)₂]SeO₄·2H₂O (blue) transforms irreversibly into [NiL₂SeO₄] (blue). [NiL₂]X₂ (X=0.5SO₄ or 0.5SeO₄), prepared from their corresponding diaquo complexes by the temperature arrest technique, shows irreversible thermochromism from yellow to blue without showing any peak in the d.t.a./d.s.c. curves. [NiL₂(NCS)₂] (blue) undergoes a thermally induced phase transition without any visual change. All the yellow species are square planar; the blue species are octahedral. These colour changes are due to configurational changes; the phase change in [NiL₂(NCS)₂] is probably due to conformational changes in the diamine chelate rings.     

Terminal and four-coordinate vanadium(IV) phosphinidene complexes. A pseudo Jahn-Teller effect of second order stabilizing the V-P multiple bond

Treatment of the four-coordinate vanadium neopentylidene (Nacnac)V=CHtBu(I) (Nacnac- = [Ar]NC(Me)CHC(Me)N[Ar], Ar = 2,6-iPr2C6H3) with a bulky primary lithium phosphide LiPHR (R = 2,4,6-iPr3C6H2, 2,4,6-tBu3C6H2) leads to alpha-hydrogen migration concomitant with the formation of a four-coordinate vanadium complex containing a terminal phosphinidene functionality (Nacnac)V=PR(CH2tBu). The crystal structures for the vanadium phosphinidene complexes prepared herein were determined by single-crystal X-ray diffraction methods. Solution EPR and magnetic measurements of the vanadium phosphinidenes are also in accordance with such systems containing a V(IV) metal center, and DFT calculations indicate the V=P bond to be stabilized through a pseudo Jahn-Teller effect of second order.     

Natural convection heat transfer and entropy generation in a porous rhombic enclosure: influence of non-uniform heating

Journal of Thermal Analysis and Calorimetry - In this paper, we present a numerical investigation of natural convection heat transfer and entropy generation for a rhombic enclosure with inclination...