A Construction of Totally Reflexive Modules

We construct infinite families of pairwise non-isomorphic indecomposable totally reflexive modules of high multiplicity. Under suitable conditions on the totally reflexive modules M and N, we find infinitely many non-isomorphic indecomposable modules arising as extensions of M by N. The construction uses the bimodule structure of \({Ext^{1}_{R}}((M,N)\) over the endomorphism rings of N and M. Our results compare with a recent theorem of Celikbas, Gheibi and Takahashi, and broaden the scope of that theorem.     

Potentiometric study of binary complexes of methyl 2-pyridyl ketone oxime, phenyl 2-pyridyl ketone oxime and diacetyl monooxime with some transition and heavy metal ions in aqueous solution

The complexation reaction between some oximes including methyl-2-pyridylketone oxime (MPKO), phenyl-2-pyridylketone oxime (PPKO) and diacetyl monooxime (DMO) with some transition and heavy metal ions Co2+, Ni2+, Zn2+, Pb2+, Fe2+, Fe3+, Cr3+ and La3+ has been studied potentiometrically in aqueous solution at 25+/-0.1 degrees C and ionic strength (mu) of 0.1M supported by KCl. The overall stability constants logbeta's of respective species were obtained by computer refinement of pH-volume data using BEST program. The best model among the several proposed models was selected according to the lowest sigma(fit) value. The main species in binary systems are ML, ML2, MLH, MLH2, ML2H, ML2H2, MOHL, M(OH)2L, M(OH)L2 and M(OH)2L2 (L = MPKO or PPKO or DMO).     

Diastereoselective functionalizations of enecarbamates derived from pipecolic acid towards 5-guanidinopipecolates as arginine mimetics

Various substituents could be diastereoselectively introduced into the 5-position of pipecolic acid via electrophilic or free-radical-initiated addition to the carbon-carbon double bond of endocyclic enecarbamates derived from pipecolic acid. This study allowed the diastereoselective synthesis of both cis- and trans-5-guanidino pipecolates, which were designed as constrained arginine mimetics and whose potential inhibition of nitric oxide synthase (NOS) was evaluated with three NOS isoforms.     

Single source heterobimetallic precursors for the deposition of Cu-Ti mixed metal oxide thin films

Heterobimetallic molecular precursors [Ti(4)(dmae)(6)(mu-OH)(mu-O)(6)Cu(6)(benzoate)(9)] (1) and [Ti(4)(dmae)(6)(mu-OH)(mu-O)(6)Cu(6)(2-methylbenzoate)(9)] (2) were prepared by the interaction of Ti(dmae)(4) [dmae=N,N-dimethylaminoethanolate] with Cu(benzoate)(2).2H(2)O for (2) and Cu(2-methylbenzoate)(2).2H(2)O for (2), respectively, in dry toluene, for selective deposition of Cu/Ti oxide thin films for possible technological applications. Both the complexes were characterized by melting point, elemental analysis, FT-IR, thermal analysis and single crystal X-ray analysis. Complex (1) crystallizes in the triclinic space group P-1 and complex (2) in the rhombohedral space group R-3. The TGA analysis proves that complexes (1) and (2) undergo facile thermal decomposition at 550 degrees C to form copper titanium mixed metal oxides. The SEM/EDX and XRD analyses suggest the formation of carbonaceous impurity free good quality thin films of crystalline mixtures of beta-Cu(3)TiO(4) and TiO(2) for both (1) and (2), with average grain sizes of 0.29 and 0.74 microm, respectively. Formation of two different homogeneously dispersed oxide phases is also supported by electrical impedance measurements.     

Two new bioactive oleanane triterpene glycosides from Terminalia arjuna

Two new oleanane-type triterpene glycosides designated as Termiarjunoside I and Termiarjunoside II were isolated from stem bark of Terminalia arjuna (Combretaceae) and characterized as olean-1alpha,3beta,9alpha,22alpha-tetraol-12-en-28-oic acid-3beta-D-glucopyranoside (1) and olean-3alpha,5alpha,25-triol-12-en-23,28-dioic acid-3alpha-D-glucopyranoside (2) based on chemical and spectral data evidences. Both compounds 1 and 2 potently suppressed the release of nitric oxide and superoxide from macrophages and also inhibited aggregation of platelets.     

N‐(X‐Chlorophenyl)‐4‐hydroxy‐2‐methyl‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide (with X = 2 and 4)

The structures of N‐(2‐chlorophenyl)‐4‐hydroxy‐2‐methyl‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide and N‐(4‐chlorophenyl)‐4‐hydroxy‐2‐methyl‐2H‐1,2‐benzothiazine‐3‐carboxamide 1,1‐dioxide, both C₁₆H₁₃ClN₂O₄S, are stabilized by extensive intramolecular hydrogen bonds. The 4‐chloro derivative forms dimeric pairs of molecules lying about inversion centres as a result of intermolecular N—H...O hydrogen bonds, forming 14‐membered rings representing an R₂²(14) motif; the 2‐chloro derivative is devoid of any such intermolecular hydrogen bonds. The heterocyclic thiazine rings in both structures adopt half‐chair conformations.     

Synthesis,spectroscopic and structural characterization of diphenyltin(IV) complexes of acetone Schiff bases of S-alkyldithiocarbazates

New diphenyltin(IV) complexes of empirical formula, [Sn(C₆H₅)₂(NS)Cl] (NS = anionic forms of the acetone Schiff bases of S-methyl or S-benzyldithiocarbazate) have been prepared and characterized by IR, NMR and Mössbauer spectroscopic techniques. The crystal and molecular structures of the acetone Schiff bases of S-methyldithiocarbazate (Hacsme) and S-benzyldithiocarbazate (Hacsbz) and their tin(IV) complexes have been determined by X-ray diffraction. In the solid state, both the Schiff bases exist in their thioketo tautomeric forms with the azomethine nitrogen atom trans to the thione sulfur atom but in the tin(IV) complexes they are present in their deprotonated ene-thiolate forms being coordinated to the tin atom as bidentate chelating agents via the azomethine nitrogen and thiolate sulfur atoms. The tin atom adopts a five-coordinate, approximately trigonal bipyramidal geometry, with the thiolate sulfur atom of the Schiff base and the two phenyl groups occupying the equatorial positions. The azomethine nitrogen atom and the chlorine ligand occupy axial positions. The distortion from a regular trigonal bipyramidal or a square-pyramidal geometry is attributed to the restricted bite sizes of the five-membered chelate rings.     

Synthesis,single crystal structure determination,and solution behavior of an 8-hydroxyquinoline derivative of niobium(V) ethoxide

An 8-hydroxyquinoline derivative of niobium(V) ethoxide was synthesized and characterized by elemental analysis, mass spectrometry, infrared, electronic, and ¹H, ¹³C, and ⁹³NMR spectroscopies. Tetraethoxy(8-quinolinato)niobium(V), as shown by the single crystal structure determination, exists as an octahedral compound in the solid state in which the 8-quinolinato group chelates to the metal atom. In solution, this group partially becomes unidentate; the six-coordinate species is in equilibrium with the five-coordinate species, as shown by ⁹³Nb and variable-temperature ¹H NMR spectroscopy.     

A three-component novel synthesis of 1-carbamato-alkyl-2-naphthol derivatives

A new one-pot, efficient three-component condensation of benzaldehydes, 2-naphthol, and carbamates in the presence of silica supported sodium hydrogen sulfate as an effective heterogeneous catalyst for the synthesis of novel 1-carbamato-alkyl-2-naphthol derivatives under solvent-free conditions is described. The present methodology offers several advantages, such as high yields, short reaction times, and very easy workup.