Cd, Hg, and Pb Compounds of Benzene-1,3-diamidoethanethiol (BDETH(2))

Benzene-1,3-diamidoethanethiol (BDETH2) is an exceptional precipitant for removing soft heavy metals from water. The present work will detail the bonding arrangement of BDETH2 to the metals Cd, Hg, and Pb, along with the full characterization data of the BDET-M compounds. It was found that the Hg compound has a linear S-M-S geometry. The characterization data consisted of Mp, EA, IR, Raman, MS, XANES, EXAFS, and solid-state multinuclear NMR.     

Between discovery and justification

This column is aforum for discussion of mathematical communities throughout the world, and through all time. Our definition of “mathematical community” is the broadest. We include “schools” of mathematics, circles of correspondence, mathematical societies, student organizations, and informal communities of cardinality greater than one. What we say about the communities is just as unrestricted. We welcome contributions from mathematicians of all kinds and in all places, and also from scientists, historians, anthropologists, and others.     

Hydrogen-Bonded Double Strands: Crystal Structure and Spectroscopic Propertiesof a 2,2′-Dipyrryl Ketone

Summary.  The synthesis, crystal structure determination, conformational analysis, and spectroscopic properties of 3,3′-diethyl-4,4′-dimethyl-2,2′-dipyrryl ketone (1) are reported. The dipyrryl ketone is a model for the dipyrrole core of 10-oxobilirubin, a presumed metabolite in alternate pathways of excretion of the yellow pigment of jaundice, bilirubin. In the crystal, 1 adopts a helical conformation, with a molecule of one helicity being hydrogen-bonded to two molecules of the opposite helicity. Thus, 1 self-assembles via hydrogen bonding into supramolecular double-stranded arrays, where molecules of the same helicity comprise one strand and are paired through hydrogen bonding to molecules of opposite helicity in the second strand. In the observed molecular conformation each pyrrole ring and adjacent carbonyl group are rotated into an sc conformation (torsion angle ∼29 °), with each N-H pointing in the same direction as the C*O. Molecular mechanics/dynamics calculations predict the sc,sc conformation, absent hydrogen bonding, to be the most stable, but only by a few tenths of a kj/mol. In CHCl₃, 1 is monomeric according to vapor pressure osmometry studies (). ¹H NMR NH chemical shifts in CDCl₃ suggest a predominantly anti orientation of the C=O and pyrrole NHs, which is opposite to the orientation observed in the crystal. Received February 4, 2000. Accepted February 14, 2000     

On the Molecularity of Bilirubins and their Esters and Anions in Chloroform Solution

Summary.  Bilirubins with propionic acids at C-8 and C-12 engage in intramolecular hydrogen bonding and are thought to be monomeric in solution, although the latter is unproven. In contrast, their dimethyl esters and etiobilirubin analogs (with the C-8 and C-12 propionic acids replaced by alkyl residues) favor intermolecular hydrogen bonding and are thought to be dimeric in nonpolar solvents. There is little information on the molecularity of the bilirubin dianion in solution. In this work, vapor pressure osmometry studies of chloroform solutions of bilirubins, their dimethyl esters, and etio-analogs clearly indicate that the diacids and dianions are monomeric, whereas the diesters and dialkyls are dimeric. However, the presence of a C-10 gem-dimethyl group causes the ester and the etiobilirubin to become monomeric. Received May 9, 2000. Accepted May 19, 2000     

Supramolecular Ribbons. Crystal Structure and Spectroscopic Properties of 2,2′-Bipyrroyl

 A crystal structure determination of 2,2′-bipyrroyl (1; 2,2′-dipyrryl-diketone, bis (2-pyrrolyl)ethanedione) and its spectroscopic properties in solution are reported. In the crystal, 1 self-assembles via hydrogen bonding into supramolecular ribbons that extend indefinitely through the crystal lattice. The observed molecular conformation is one where each pyrrole ring and adjacent carbonyl group are co-planar (torsion angle ∼ 0.9°), with the N-H pointing in the same direction as the C=O. The two carbonyls have a transoid but not co-planar geometry with a torsion angle of ∼128°. Adjacent molecules in the crystal are linked by pairs of intermolecular hydrogen bonds, pyrrole NH to carbonyl oxygen, to form a matrix of polymeric chains that lie like neatly stacked, parallel streams of ribbons. Molecular mechanics calculations on the monomer indicate an intra-molecularly hydrogen bonded planar conformation (sp, ap, sp) at the global energy minimum. In CHCl₃, 1 is monomeric according to vapor pressure osmometry (MW _obs=179±10 vsċMW _calc=188). In THF, the measured molecular weight is 340±15, which corresponds best to one molecule of 1 solvated by two THF molecules (MW=322 for C₁₀H₈N₂O₄ċ2 C₄H₈O) rather than to a dimer.     

Actions of Camptothecin Derivatives on Larvae and Adults of the Arboviral Vector Aedes aegypti

Mosquito-borne viruses including dengue, Zika, and Chikungunya viruses, and parasites such as malaria and Onchocerca volvulus endanger health and economic security around the globe, and emerging mosquito-borne pathogens have pandemic potential. However, the rapid spread of insecticide resistance threatens our ability to control mosquito vectors. Larvae of Aedes aegypti were screened with the Medicines for Malaria Venture Pandemic Response Box, an open-source compound library, using INVAPP, an invertebrate automated phenotyping platform suited to high-throughput chemical screening of larval motility. We identified rubitecan (a synthetic derivative of camptothecin) as a hit compound that reduced A. aegypti larval motility. Both rubitecan and camptothecin displayed concentration dependent reduction in larval motility with estimated EC₅₀ of 25.5 ± 5.0 µM and 22.3 ± 5.4 µM, respectively. We extended our investigation to adult mosquitoes and found that camptothecin increased lethality when delivered in a blood meal to A. aegypti adults at 100 µM and 10 µM, and completely blocked egg laying when fed at 100 µM. Camptothecin and its derivatives are inhibitors of topoisomerase I, have known activity against several agricultural pests, and are also approved for the treatment of several cancers. Crucially, they can inhibit Zika virus replication in human cells, so there is potential for dual targeting of both the vector and an important arbovirus that it carries.     

The existence of disjoint (hooked) near‐Rosa sequences and applications

We show that the necessary conditions are sufficient for the existence of two disjoint near (hooked) Rosa sequences, with all admissible orders $n\ge 6$ and all possible defects. Further, we apply this result for the existence of new types of cyclic and simple GDDs.     

Development of automated separations for actinides analysis

Journal of Radioanalytical and Nuclear Chemistry - Novel methods for sample preparation by adapting an automated chromatography system to radiochemical analysis for analysis of trace impurities is...