The reaction mechanisms for the reactions of cobaltacyclopentadiene with isocyanate and isothiocyanate exclusively in singlet or triplet states, or involving transition between states, were studied by means of hybrid density functional theory (B3LYP) calculations. The results clearly showed that a two-state mechanism involving both singlet and triplet states is more favorable than the corresponding singlestate mechanism for all the reactions. We also found that the reactions of isocyanate and isothiocyanate to give pyridin-2(1H)-one and pyridine-2(1H)-thione complexes, respectively, are more favorable than those that give 2H-pyran-2-imine and 2H-thiopyran-2-imine complexes. This is mainly due to the greater stabilities of pyridin-2(1H)-one and pyridine-2(1H)-thione compared with 2H-pyran-2-imine and 2H-thiopyran-2-imine. A change in spin state plays a crucial role in the two-state mechanism; first, the C]N bond of the isocyanate or isothiocyanate inserts into the CoeCa bond of cobaltacyclopentadiene in the singlet state to give azacobaltacycloheptadienone or azacobaltacycloheptadienethione intermediates, and subsequent reductive elimination in the triplet state gives the pyridin-2(1H)-one or pyridine-2(1H)-thione complex, respectively.

A new homologous series of thermally stable thermotropic liquid crystalline poly(arylidene-ether)s based on 4-tertiary-butyl-cyclohexanone moiety was synthesised by solution polycondensation of 4,4 -diformyl- α , ω -diphenoxyalkanes, I a–f ,or4,4 -diformyl-2,2 -dimethoxy- α , ω -diphenoxyalkanes, II a–f , with the 4-tertiary-butyl-cyclohexanone monomer. A model compound III was synthesised from the monomer with benzaldehyde and characterised by elemental and spectral analyses. The inherent viscosities of the resulting polymers were in the range of 0.18–0.92 dL/g. The mesomorphic properties of these polymers were studied as a function of the diphenoxyalkane space length. Their thermotropic liquid crystalline properties were examined by differential scanning calorimetry (DSC) and optical polarising microscopy and demonstrated that the resulting polymers form nematic mesophases over wide temperature ranges. The thermal properties of those polymers were evaluated by thermogravimetric analysis and DSC measurements and correlated to their structural units. X-ray analysis showed that polymers having some degree of crystallinity in the region 2 θ = 5–60 ◦ . In addition, the morphological properties of selected examples were tested by scanning electron microscopy.

A new homologous series of thermally stable thermotropic liquid crystalline poly(arylidene-ether)s based on 4-tertiary-butyl-cyclohexanone moiety was synthesised by solution polycondensation of 4,4 -diformyl- α , ω -diphenoxyalkanes, I a–f ,or4,4 -diformyl-2,2 -dimethoxy- α , ω -diphenoxyalkanes, II a–f , with the 4-tertiary-butyl-cyclohexanone monomer. A model compound III was synthesised from the monomer with benzaldehyde and characterised by elemental and spectral analyses. The inherent viscosities of the resulting polymers were in the range of 0.18–0.92 dL/g. The mesomorphic properties of these polymers were studied as a function of the diphenoxyalkane space length. Their thermotropic liquid crystalline properties were examined by differential scanning calorimetry (DSC) and optical polarising microscopy and demonstrated that the resulting polymers form nematic mesophases over wide temperature ranges. The thermal properties of those polymers were evaluated by thermogravimetric analysis and DSC measurements and correlated to their structural units. X-ray analysis showed that polymers having some degree of crystallinity in the region 2 θ = 5–60 ◦ . In addition, the morphological properties of selected examples were tested by scanning electron microscopy.

Abstract Out of 210 actinomycetes isolates belonged to the genus Streptomyces recovered from rhizospheric soil of Triticum vulgaris, Zea mays and Vicia faba cultivated in Assuit and New Valley Governorates of Egypt, ten isolates were capable of producing high amounts of L-glutaminase enzyme. The most potent L-glutaminase producer isolate was Streptomyces sp. ASU319 recovered from rhizosphere of Triticum vulgaris. The higher producer actinomycete isolate was identified by sequencing of 16S rRNA as Streptomyces variabilis ASU319 and was deposited in the GenBank nucleotide sequence database under accession number KC145278. Factors affecting L-glutaminase production by the Streptomyces variabilis ASU319(KC145278) were examined and the results revealed that the maximum L-glutaminase value was obtained when the isolate cultivated in the production broth medium supplemented by glutamine 8 mg/ml, adjusted at pH 4 and incubated at 35 °C. These results suggest that L-glutaminase-producing Streptomyces variabilis ASU319 could be used as a plant growth promoting rhizobacteria by increasing the ammonia content in the rhizosphere soil across degradation of the agricultural wastes. Also this isolate can be used in both pharmaceutical and food industrial application for L-glutaminase production on commercial scale.