Oxidomolybdenum(VI) complexes with atrane-type [O3N] ligands

Dioxomolybdenum(VI) complex [MoO₂Cl₂(dmso)₂] reacts with a series of tetradentate O₃N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(Lⁿ)]. The reaction of H₃L¹ produces [MoOCl(L¹)] as two separable isomers, whereas the reaction of H₃L² or H₃L³ yields a single product. The X-ray analyses of cis- and trans-[MoOCl(L¹)] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.     

Quinoxaline N-oxides

The reactions of 2-methyl- and 2, 3-dimethylquinoxalines and their N-oxides with C₆H₅CHO, p-O₂NC₆H₄CHO, and p-CH₃OC₆H₄CHO, have been investigated. It is shown that the 1, 4-di-N-oxides of 2-methyl- and 2, 3-dimethylquinoxaline do not undergo condensation with aromatic aldehydes when heated in the presence of acids, but that in the presence of strongly basic reagents they readily, without heating, undergo an aldol-type reaction, to give the corresponding carbinols. Under those conditions the di-N-oxide of 2, 3-dimethylquinoxaline and C₆H₅CHO or p-CH₃OC₆H₄CHO gives only monocarbinols, whereas p-O₂NC₆H₄CHO reacts with both methyl groups. Under the action of concentrated H₂SO₄ these carbinols give the corresponding styryls. The di-N-oxides of -methyl derivatives of quinoxaline react with aromatic aldehydes more readily than the N-oxides of - and -methylpyridines and quinolines. Views are put forward regarding the relationships between reactivities of - and -methyl derivatives of heterocyclic N-oxides and their abilities to undergo polarization in two opposite directions.     

Novel Porphyrin-Cholic Acid Conjugates as Receptors for Biologically Important Anions

A series of novel receptors showing high binding affinity in aqueous media for biologically important anions are reported. These naturally chromophoric porphyrin-based receptors contain cholic acids connected via quaternary alkyl ammonium amido linkages.     

Structure Effect of Imidazolium-Based Dicationic Ionic Liquids on Claisen Rearrangement

A large group of imidazolium-based dicationic ionic liquids (DILs) has been prepared in good yields. Thermal stability of all DILs has been determined. The effects of the reaction time, cation, imidazolium C₂–H acidity, and anion on the Claisen rearrangement of allyl phenyl ether have been investigated. Type of anion and the presence of the acidic C₂–H bond in the imidazolium moieties have proven to be essential for this reaction. The simple procedure and the possibility of avoiding the use catalysts and volatile organic solvents make this synthetic method environmentally benign and adaptable for large-scale applications.     

Time-resolved fluorescence spectroscopy reveals functional differences of cationic polymer-DNA complexes

Cationic polymers bind DNA and form compacted nanoparticulates (i.e., polyplexes). Polyplexes augment DNA delivery into the cells as a nonviral method of gene therapy. DNA packing and release are the key factors in polyplex-mediated gene delivery, but they are poorly understood due to the lack of physical methods of investigation. We used time-resolved fluorescence spectroscopy to study poly(ethylenimine) (PEI) and poly(L-lysine) (PLL) polyplexes. Analysis of fluorescence lifetimes and time-resolved spectra revealed that DNA exists in several different states in PEI polyplexes and only in one tightly bound state in PLL polyplexes. The observed difference in the nature of the polyplexes may explain why PEI releases DNA more easily than PLL even though both polycations condense DNA effectively. The present method utilizing time-resolved fluorescence spectroscopy gives information on the specific interactions between DNA and the cationic polymers in the polyplexes. This kind of information is very important in the development of biologically effective nonviral systems for DNA delivery.