Enhancement of second harmonic generation efficiency: Growth and characterization of magnesium(II)-doped tetrakis(thiourea)nickel(II) chloride crystals

The influence of magnesium doping on the properties of tetrakis(thiourea)nickel(II) chloride crystals has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the alkaline earth metal are observed by scanning electron microscopy. The incorporation of Mg(II) into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The crystal is further characterized by Kurtz powder technique and dielectric studies.     

Preparation and properties of some cardopolyamides

Several polyamides that contained cardo units were prepared. Thus 9,9-bis(4-aminophenyl)fluorene and 9,9-bis(4-aminophenyl)anthrone were condensed with 2,5-dimethyl-1,4-benzenediacetyl chloride, 2,4-dimethyl-1,4-benzendiacetyl chloride, and 2,5-dimethoxy-1,4-benzediacetyl chloride. Lowtemperature solution polycondensation in dimethyl acetamide (DMAc) was used throughout. The polymers were obtained in 80–90% yield and possessed intrinisic viscosities in the range of 0.6–1.2. The polymers were characterized by infrared (IR) spectra and elemental analysis. The solubility, crystallinity, and thermal stability of the polyamides were also determined.     

Redox polymerization-kinetics of the reaction inititated by the system CH2(CH)2?MN(III) in aqueous H2SO4 and the system CH2(CN)2?MN(OAC)3 in DMF and acetic acid

Polymerization of acrylonitrile and methyl methacrylate by the redox systems propanedinitrile-Mn(III) in aqueous sulfuric acid and propanedinitrile-Mn(OAc)₃ in DMF and glacial acetic acid was investigated in the temperature range 20–40°C. The kinetics are consistent with the formation of an intermediate complex whose irreversible decomposition yields the initiating radical. With both monomers mutual termination predominates. The main difference between aqueous H₂SO₄ and acetic acid compared with DMF lies in the ease of oxidation of the primary radicals by the oxidant. Rate and equilibrium parameters were estimated and their significance discussed.     

Synthesis and characterization of poly benzoylpropionamides

Linear polyamides having viscosities in the range of 0.12–0.41 dl/g have been prepared from bisbenzoyl propionic acids and aromatic diamines by low temperature solution polycondensation in 80–85% yield. Their solubility characteristics were studied in various solvents e.g. DMF, DMAC, HMPT, H₂SO₄. These polyamides are amorphous in nature; their densities range from 1.2 to 1.8 g/cm³. Their thermal properties were examined by TGA and DTA. The two stage decomposition phenomenon observed in TGA is in agreement with the DTA results. The integral procedural decomposition temperatures were calculated and found to exceed 250 in almost all cases.     

Synthesis of diatropic highly benzannelated annulenes.

The first examples of annelated cis-dihydropyrenes, 16, 18, 19, together with a number of highly annelated trans-dihydropyrenes, 2 - 4 and, 17, are described. All are diatropic and indicate that higher annelation does not remove the delocalisation in a macrocyclic ring.     

Synthesis and properties of polyester based polyurethanes

Hydroxyl terminated polyesters were prepared by a melt condensation technique using adipic acid and various diols. They were characterised by hydroxyl number, acid number and intrinsic viscosities in benzene. The polyesters were reacted with excess tolylene diisocyanate to yield isocyanate terminated prepolymers and subsequently cured with diols and diamines. These polymers were characterised by i.r. spectra, viscosity measurements and thermogravimetric analysis. The glass transition temperature of the polymers were found to be in the region ?25 to ?55. The influences of prepolymers and curing reagents are discussed with respect to the low temperature flexibility and thermal stability of the polyurethanes.     

Synthesis of beta-lactones: a highly active and selective catalyst for epoxide carbonylation

A new highly active and selective catalyst for the synthesis of beta-lactones from CO and epoxides is reported. The catalyst, [(N,N'-bis(3,5-di-tert-butylsalicylidene) phenylenediamino)Al(THF)2][Co(CO)4] ([(salph)Al(THF)2][Co(CO)4]) is easily prepared from the corresponding (salph)AlCl and NaCo(CO)4. At 50 degrees C and 880 psi of CO, the catalyst (1 mol %) carbonylates epoxides such as propylene oxide, 1-butene oxide, epichlorohydrin, and isobutylene oxide to the lactones beta-butyrolactone, beta-valerolactone, gamma-chloro-beta-butyrolactone, and beta-methyl-beta-butyrolactone in high yield. (R)-Propylene oxide was carbonylated to (R)-beta-butyrolactone with retention of stereochemistry.     

Interstrand and intrastrand DNA-DNA cross-linking by 1,2,3,4-diepoxybutane: role of stereochemistry

1,2,3,4-Diepoxybutane (DEB) is a bifunctional electrophile capable of forming DNA-DNA and DNA-protein cross-links. DNA alkylation by DEB produces N7-(2'-hydroxy-3',4'-epoxybut-1'-yl)-guanine monoadducts, which can then form 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) lesions. All three optical isomers of DEB are produced metabolically from 1,3-butadiene, but S,S-DEB is the most cytotoxic and genotoxic. In the present work, interstrand and intrastrand DNA-DNA cross-linking by individual DEB stereoisomers was investigated by PAGE, mass spectrometry, and stable isotope labeling. S,S-, R,R-, and meso-diepoxides were synthesized from l-dimethyl-2,3-O-isopropylidene-tartrate, d-dimethyl-2,3-O-isopropylidene-tartrate, and meso-erythritol, respectively. Total numbers of bis-N7G-BD lesions (intrastrand and interstrand) in calf thymus DNA treated separately with S,S-, R,R-, or meso-DEB (0.01-0.5 mM) were similar as determined by capillary HPLC-ESI(+)-MS/MS of DNA hydrolysates. However, denaturing PAGE has revealed that S,S-DEB produced the highest number of interchain cross-links in 5'-GGC-3'/3'-CCG-5' sequences. Intrastrand adduct formation by DEB was investigated by a novel methodology based on stable isotope labeling HPLC-ESI(+)-MS/MS. Meso DEB treatment of DNA duplexes containing 5'-[1,7, NH(2)-(15)N(3),2-(13)C-G]GC-3'/3'-CCG-5' and 5'-GGC-3'/3'-CC[(15)N(3),2-(13)C-G]-5' trinucleotides gave rise to comparable numbers of 1,2-intrastrand and 1,3-interstrand bis-N7G-BD cross-links, while S,S DEB produced few intrastrand lesions. R,R-DEB treated DNA contained mostly 1,3-interstrand bis-N7G-BD, along with smaller amounts of 1,2-interstrand and 1,2-intrastrand adducts. The effects of DEB stereochemistry on its ability to form DNA-DNA cross-links may be rationalized by the spatial relationships between the epoxy alcohol side chains in stereoisomeric N7-(2'-hydroxy-3',4'-epoxybut-1'-yl)-guanine adducts and their DNA environment. Different cross-linking specificities of DEB stereoisomers provide a likely structural basis for their distinct biological activities.