Triple-decker sandwich compounds bearing compact triallyl tripods for molecular information storage applications

The design of redox-active molecules that afford multistate operation and high charge density is essential for molecular information storage applications. Triple-decker sandwich compounds composed of two lanthanide metal ions and three porphyrinic ligands exhibit a large number of oxidation states within a relatively narrow electrochemical window. High charge density requires a small footprint upon tethering triple deckers to an electroactive surface. All triple deckers examined to date for information storage have been tethered via the terminal ligand and have exhibited large footprints (approximately 670 A2). Five new homonuclear (Eu or Ce) triple deckers have been prepared (via statistical or rational methods) to examine the effect of tether attachment site on molecular footprint. Three triple deckers are tethered via the terminal ligand (porphyrin) or central ligand (porphyrin or imidazophthalocyanine), whereas two triple deckers each bear two tethers, one at each terminal ligand. The tether is a compact triallyl tripod. Monolayers of the triple deckers on Si(100) were examined by electrochemical and FTIR techniques. Each triple decker exhibited the expected four resolved voltammetric waves, owing to formation of the mono-, di-, tri-, and tetracations. The electrochemical studies of surface coverage (gamma, obtained by integrating the voltammetric waves) reveal that coverages approaching 10(-10) mol cm(-2), corresponding to a molecular footprint of approximately 170 A2, are readily achieved for all five of the triple deckers. The surface coverage observed for the tripodal functionalized triple deckers is approximately 4-fold higher than that obtained for monopodal-functionalized triple deckers (carbon, oxygen, or sulfur anchor atoms) attached to either Si(100) or Au(111). The fact that similar, relatively high, surface coverages can be achieved regardless of the location (or number) of the tripodal tether indicates that the tripodal functionalization, rather than the location of the tether, is the primary determinant of the packing density.     

Reactions of cephalosporin sulfones 3. Synthesis of 2‐phenylhydrazonocephem‐sulfones. A new potential entry to 2‐aminocephems

Reaction of cephem sulfones 1a‐e with aryldiazonium salts gives the 2‐azo compounds which immediately rearrange into the corresponding 2‐hydrazono derivatives 2a‐e .     

Rate constants for some reactions of inorganic radicals with inorganic ions. Temperature and solvent dependence

Rate constants for several reactions of inorganic radicals with inorganic anions in aqueous and aqueous/acetonitrile solutions have been measured as a function of temperature by laser flash photolysis. The reactions studied were (1) Cl₂^? + N₃^?, (2) Br₂^? + N₃^?, (3) Cl₂^? + SCN^?, (4) Br₂^? + SCN^?, (5) SO₄^? + Cl^?, (6) SO₄^? + CO₃^2?, and (7) N₃? + I^?. The rate constants were corrected for ionic strength and ranged from 10⁶ to 10⁹ L mol^?1 s^?1. The Arrhenius activation energies varied from 2 to 12 kJ mol^?1 for the first 4 reactions, were higher for reaction 6, and negative for reaction 5. The pre-exponential factors also varied considerably with log A ranging from 5 to 14. The values of k₂₉₈ decreased in most cases by more than an order of magnitude upon increasing the acetonitrile (ACN) fraction from 0 to 70%. For most reactions, this decrease in k₂₉₈ was due to changes in log A with little regularity in the small changes observed in E_a. For reaction 7, k₂₉₈ was practically unchanged due to compensating effects of the changes in E_a and log A with ACN mol fraction, giving an isokinetic relationship. An isokinetic relationship was also observed in the case of reaction 6; E_a and log A change in parallel while changing ACN mol fraction. Reaction 3 (Cl₂^? + SCN^?) was also studied in water/t-butanol and water/acetic acid mixtures. Linear correlation was found between log k and the dielectric constant of the medium for water/ACN and water/t-BuOH but the lines for the two solvent mixtures had different slopes, suggesting specific solvation effects in addition to the primary solvent polarity effects. With water/acetic acid, k decreased and then increased upon addition of acetic acid. © 1993 John Wiley & Sons, Inc.     

Synthesis of amide-linked benzazolyl isoxazoles adopting green methods and evaluation as antimicrobials

Some new benzoxazolyl isoxazoles, benzothiazolyl isoxazoles and benzimidazolyl isoxazoles connected by amide bonds ( 7-9 ) were prepared from N-benzazolylcarbamoylmethylcinnamamides ( 1-3 ) adopting eco-friendly synthetic methodologies. In fact, cycloaddition of nitrile oxide generated from araldoxime using iodosobenzene and cetyltrimethylammonium bromide to 1-3 followed by treatment with iodine in dimethyl sulfoxide led to the formation of title compounds with good yields and in shorter reaction times. The structures of all the synthesized compounds were confirmed by spectral parameters, viz, IR, NMR, and mass spectra and were assayed for antimicrobial activity. Among all the tested compounds, 8a and 8c displayed excellent antibacterial activity, whereas 9a and 9c showed promising antifungal activity.     

Sample preparation workflow for the liquid chromatography tandem mass spectrometry based analysis of nicotinamide adenine dinucleotide phosphate cofactors in yeast†

The accurate quantification of the highly unstable intracellular cofactor nicotinamide adenine dinucleotide phosphate in its oxidized and reduced forms demands a thorough evaluation of the analytical workflow and dedicated methods reflecting their solution chemistry as well as the biological importance of their ratio. In this work, we present a workflow for the analysis of intracellular levels of oxidized and reduced nicotinamide adenine dinucleotide phosphate in the yeast Pichia pastoris, including hot aqueous extraction, chromatographic separation in reversed‐phase conditions employing a 100% wettable stationary phase, and subsequent tandem mass spectrometric analysis. A thorough evaluation and optimization of the sample preparation procedure resulted in excellent biological repeatabilities (on average <10%, N = 3) without employing an internal standardization approach. As a consequence, the methodology proved to be appropriate for the relative assessment of intracellular levels of oxidized and reduced nicotinamide adenine dinucleotide phosphate in different P. pastoris strains. The ratio of reduced versus oxidized nicotinamide adenine dinucleotide phosphate was significantly higher in an engineered strain overexpressing glucose‐6‐phosphate dehydrogenase than in the corresponding wildtype strain. Interestingly, a difference was also observed in the nicotinamide adenine dinucleotide phosphate pool size, which was significantly higher in the wildtype than in the modified strain.     

Lithium perchlorate-, acetic anhydride-, and triphenylphosphine-assisted multicomponent syntheses of 4-unsubstituted 2,5-dioxooctahydroquinoline-3-carboxylates and 3-carbonitriles

Lithium perchlorate and acetic anhydride were the key additives for the multi-component reaction between 3-aminocyclohex-2-enones, formaldehyde, and malonates yielding adducts that were annulated under acidic conditions to afford bicyclic 2,5-dioxooctahydroquinoline-3-carboxylates. When methyl cyanoacetate was subjected to the same reaction conditions in the presence of a catalytic amount of triphenylphosphine, the bicyclic 2,5-dioxooctahydroquinoline-3-carbonitriles were obtained in a one-flask reaction.     

Synthesis of Novel Spiro Tetrahydrothiapyrano-Isoxazolines and Pyrazolines

Cis 2,6-Diphenyltetrahydrothiapyranone (1) was subjected to Wittig reaction to generate exocyclic double bond (2a-c). Cycloaddition of nitrile oxides and nitrile imines to the latter led to a novel spiro tetrahydrothiapyranoisoxazolines (3a-f) and spiro tetrahydrothiapyranopyrazolines (4a-f)     

1,5-Diphenyl-3,3-dicyano-1,5-pentanedione: A Synthon for Novel Heterocycles

1,5-Diphenyl-3,3-dicyano-1,5-pentanedione has been used to incorporate N, O, S to obtain 1,4-dihydropyridine, 4 H -pyran, and 4 H -thiopyran, which in turn serve as precursors for the synthesis of novel spiro heterocycles. All the compounds were characterized by IR and NMR spectral data.     

Synthesis,Modification, and Biological Evaluation of a Library of Novel Water-Soluble Thiopyridone-Based Organometallic Complexes and Their Unexpected (Biological) Behavior

A series of 16 dinuclear thiopyridone-based organometallics with excellent water solubility, increased stability and remarkable cytotoxicity were synthesized and characterized. The complexes of this work formed dimeric species featuring a double positive charge in polar protic solvents, accounting for their outstanding solubility in aqueous solution. Most of them displayed higher antiproliferative activity than their parental thiomaltol complex, with unexpected cytotoxicity trends depending on the employed metal center, ligand modification, and cell line. Insights into their behavior in biological systems were gathered by means of amino-acid interaction studies, cytotoxicity tests in 3D spheroid models, laser ablation, cellular accumulation measurements, as well as cell cycle experiments.