IR Study of ion-molecular interactions in a DMF-HCl system

The Multiple Attenuated Total Reflection (MATR) IR-spectra of HCl solutions in DMF (0–48.55% HCl) were recorded and analyzed in the range of 900–4000 cm^–1. Depending on the ratio of compounds, a variety of complexes (2 DMF) · HCl (1), DMF · HCl (2), DMF · (2 HCl) (3) are formed in the system. The concentrations of the complexes were measured. Complex2 possesses a quasi-ionic structure Me₂NHCO...H...Cl. The addition of a DMF molecule to complex2 with formation of complex1 does not result in destruction of the quasi-ionic structure of the DMF-HCl bond. In excess HCl, this structure is decomposed and the complex with the ion pair structure Me₂NHCOH⁺ (ClHCl)^– is formed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1577–1582, September, 1993.     

Synthesis of functionalized pyrimidine-4-thiones and derivatives of pyrido[2,3-d]pirimidine-5-one from monoacylketene aminals

Monoacylketene aminals containing an unsubstituted NH₂ group react as C-nucleophiles with benzoyl isothiocyanate to give the corresponding thioamides which undergo cyclization by sodium methoxide in methanol to afford 6-R-amino-5-acetyl-2-phenyl-3H-pyrimidine-4-thiones. A scheme for constructing the pyrido[2,3-d]pyrimidine system from keteneaminals is offered. The reaction of 6-R-amino-5-acetyl-2-phenyl-3H-pyrimidine-4-thiones with dimethylformamide dimethylacetal leads to 8-R-N-4-methylthio-8H-pyrido-[2,3-d]pyrimidine-5-ones. Cyclization of 5-acetyl-6-benzoylamino-4-methylthio-2-phenylpyrimidine by sodium methoxide yields N-unsubstituted 4-methylthio-8H-pyrido-[2,3-d]pyrimidine-5-one.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1932–1937, November, 1993     

Conductance of electrolytes in dipolar aprotic solvent mixtures. I. Conductance of lithium chloride in mixtures of methylethylketone and acetone with N,N-dimethylformamide at 25°C

The conductances of LiCl in acetone-N,N-dimethylformamide (AC-DMF) and methylethylketone-N,N-dimethylformamide (MEK-DMF) binary mixtures have been measured at 25°C. The data were fitted to the 1978 Fuoss equation to obtain ion association constants K_A and limiting molar conductances ₀. The Bjerrum ion association theory modified by Fernandez-Prini and Prue was also used for evaluation of K_A and a, the contact ion-pair distance. LiCl is more associated in AC-DMF mixtures than in the MEK-DMF system. Addition of DMF to either AC or MEK decreases K_A and ₀ as expected from the increase in the dielectric constant and the viscosity. The distance parameter a is almost constant and equal to 2.6 A in these mixed solvent systems. The Walden products pass through minima in both ketone-rich regions.     

Room temperature phosphorescence in the liquid state as a tool in analytical chemistry

A wide-ranging overview of room temperature phosphorescence in the liquid state (RTPL¹) is presented, with a focus on recent developments. RTPL techniques like micelle-stabilized (MS)-RTP, cyclodextrin-induced (CD)-RTP, and heavy atom-induced (HAI)-RTP are discussed. These techniques are mainly applied in the stand-alone format, but coupling with some separation techniques appears to be feasible. Applications of direct, sensitized and quenched phosphorescence are also discussed. As regards sensitized and quenched RTP, emphasis is on the coupling with liquid chromatography (LC) and capillary electrophoresis (CE), but stand-alone applications are also reported. Further, the application of RTPL in immunoassays and in RTP optosensing—the optical sensing of analytes based on RTP—is reviewed. Next to the application of RTPL in quantitative analysis, its use for the structural probing of protein conformations and for time-resolved microscopy of labelled biomolecules is discussed. Finally, an overview is presented of the various analytical techniques which are based on the closely related phenomenon of long-lived lanthanide luminescence. The paper closes with a short evaluation of the state-of-the-art in RTP and a discussion on future perspectives.     

Synthesis and properties of pyrimido[4,5-<Emphasis Type="Italic">a</Emphasis>]- and pyrido[4,3-<Emphasis Type="Italic">a</Emphasis>]carbazole derivatives

Methods for the synthesis of substituted pyrimido [4,5-a]- and pyrido[4,3-a]carbazoles were proposed. Condensation of 2-(dimethylaminomethylene)-6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one with guanidine and thiourea afforded 2-amino-8-methyl-6,11-dihydro-5H-pyrimido[4,5-a]carbazole and 8-methyl-3,5,6,11-tetrahydro-2H-pyrimido[4,5-a]carbazole-2-thione, respectively. The reaction of cyano(6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-ylidene)acetamide with dimethylformamide dimethyl acetal gave N-(dimethylamino-methylene)cyano(6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-ylidene)acetamide. Cyclization of the latter yielded 1-cyano-8-methyl-3,5,6,11-tetrahydro-2H-pyrido[4,3-a]carbazol-2-one.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2740–2744, December, 2004.     

Ion mobilities in DMF-water mixtures at 25°C

Densities and viscosities of mixtures of N,N-dimethylformamide (DMF) with water at 25°C have been determined. Limiting equivalent conductances of cesium chloride, potassium chloride, potassium bromide and potassium thiocyanate in these solvent mixtures at 25°C are presented together with corresponding values of ion association constants and distance of closest approach parameters. The transference number of the potassium ion has been determined in solvent mixtures ranging from 0 to 0.75 mol fraction in DMF in water at 25°C. The conductimetric Hittorf method has been used for both potassium bromide and potassium chloride in solutions of up to 0.496 mole fraction of DMF. For solutions of potassium thiocyanate in 0.5 and 0.75 mole fraction in DMF the cationic transference number has been determined using the moving boundary method. Stokes radii have been evaluated. Transport properties are examined in relation to-solvent properties such as composition, dielectric constant, excess volume of mixing and free volume.To whom correspondence should be addressed.     

Synthesis,spectroscopic study,X-ray diffraction,and comparative antimicrobial study of Schiff bases based on o-toluidine and their Co(II) complexes

Schiff bases are versatile compounds for the design of the ternary complex. An experiment has been made to synthesize two novel complexes of Co(II). Here, The primary ligand, L₁ was prepared by the condensation reaction of o-toluidine with 3-formyl chromone or o-toluidine with 3- methylquinolinecarbaldehyde and the secondary ligand which was 8-Hydroxyquinoline. These potent complexes were prepared by condensation of primary and secondary ligands with Cobalt salt. The reaction was performed through the conventional reflux method. The newly synthesized chromone and quinoline derived novel compounds are proposed to have significant antimicrobial activity against selective strains of bacteria and fungi. This can be great opportunity for researchers and the use of biological applications of the synthesized novel compounds can be a part of unique field of research for the future to be focus. Chromone derivative has great biological diversity in the medicinal and pharmaceutical fields. Along with these compounds, quinoline derivatives also have antibacterial, and antifungal activities. The synthesized ligand and complex were characterized by elemental analysis, molecular weight determination, magnetic moment measurement, melting point determination, spectral analysis (IR, UV–Vis, ¹H NMR, Mass, etc.), and X-ray diffraction. The synthesized complexes were paramagnetic and non-electrolytic in nature. The Uv–Vis, FTIR, NMR, and Mass spectra suggest the octahedral geometry of the complexes. The synthesized compounds were further evaluated for biological studies against selected bacterial and fungal strains. It has been observed that the antimicrobial activity of most of the complexes are better than that of ligands.     

Synthesis,pharmacological evaluation,and molecular modeling studies of novel isatin hybrids as potential anticancer agents

A novel series of isatin hybrids 5a-g was designed, synthesized, and characterized spectroscopically. The synthesized compounds were evaluated for their cytotoxic activity against the human breast cancer cell line (MCF-7) by in vitro MTT assay. Amongst the tested compounds, 5e compound bearing benzyl moiety at N₄ piperazine was found to be the most active with the promising IC₅₀ (12.47 µM). Moreover, the active compounds 5e and 5g were subjected to antitumor evaluation (in vivo) against Dalton’s ascitic lymphoma (DAL) cell line and the results suggested that the best active compound 5e can normalize the blood picture in comparison to the standard drug. An in silico molecular docking study using the crystal structure of Hsp90 protein described the role of significant protein–ligand interactions and revealed more insights into the binding mode. The drug-likeliness of the compounds was predicted based on Lipinski's rule of five and pharmacokinetic ADME parameters. Hence, the synthesized isatin hybrids could be novel starting point anticancer lead compounds demonstrating drug-like properties which can be explored further for anticancer drug discovery.