An extensive ecdysteroid CoMFA

The ecdysteroid agonist activity of 71 HPLC-purified ecdysteroids was measured in the Drosophila melanogaster BII tumorous blood cell line assay. The resultant log(ED50) values, spanning almost 6 orders of magnitude, were used to construct a comparative molecular field analysis (CoMFA) model in which conformations were selected by homology to the crystal structure of ecdysone. Model A was constructed by utilization of the region- focused electrostatic indicator field (q2=0.631, r2=0.903, 5 components, 4 outliers). Model B made use of region-focused electrostatic and steric indicator fields along with MlogP (q2=0.694, r2=0.892, 5 components, 4 outliers). The model and its underlying bioassay data support a pharmacophore hypothesis in which ecdysteroid binding is understood to be due principally to the summation of localized interactions from approximately six specific loci. This is in contrast to previous structure-activity relationship hypotheses which are formulated in terms of the presence or absence of essential functional groups, without which ecdysteroid receptor affinity would be completely absent. The present CoMFA model is utilized to predict the activities of heretofore unknown ecdysteroids.     

Application of Water Soluble Resorcinarenes in Nanofiltration-Complexation with Caesium and Strontium as Targets

Combined nanofiltration-complexation is applied to the separation of caesium and strontium from a solution containing a large concentration of sodium. Caesium and strontium complexation was studied using various water soluble resorcinarene-type ligands. Combined with nanofiltration these ligands improved the separation of caesium and strontium from sodium by the FILMTEC NF 70 membrane.     

On the convexity of geometric functional of level for solutions of certain elliptic partial differential equations

We derive a new formula for differentiating with respect to level. We apply it to establish the convexity or concavity of geometric functionals of level for solutions of certain elliptic equations. We also establish a new isoperimetric inequality forp capacity,p2, for an annulus with convex boundaries.     

Simple Functors of Admissible Linear Categories

Generalizing an idea used by Bouc, Thévenaz, Webb and others, we introduce the notion of an admissible R-linear category for a commutative unital ring R. Given an R-linear category \(\mathcal {L}\), we define an \(\mathcal {L}\)-functor to be a functor from \(\mathcal {L}\) to the category of R-modules. In the case where \(\mathcal {L}\) is admissible, we establish a bijective correspondence between the isomorphism classes of simple functors and the equivalence classes of pairs (G, V) where G is an object and V is a module of a certain quotient of the endomorphism algebra of G. Here, two pairs (F, U) and (G, V) are equivalent provided there exists an isomorphism F ← G effecting transport to U from V. We apply this to the category of finite abelian p-groups and to a class of subcategories of the biset category.     

Multiple Roles of Isocyanides in Palladium‐Catalyzed Imidoylative Couplings: A Mechanistic Study

Kinetic, spectroscopic and computational studies examining a palladium‐catalyzed imidoylative coupling highlight the dual role of isocyanides as both substrates and ligands for this class of transformations. The synthesis of secondary amides from aryl halides and water is presented as a case study. The kinetics of the oxidative addition of ArI with RNC‐ligated Pd⁰ species have been studied and the resulting imidoyl complex [(ArC=NR)Pd(CNR)₂I] (Ar=4‐F‐C₆H₄, R=tBu) has been isolated and characterized by X‐ray diffraction. The unprecedented ability of this RNC‐ligated imidoyl‐Pd complex to undergo reductive elimination at room temperature to give the amide in the presence of water and an F^?/HF buffer is demonstrated. Its behavior in solution has also been characterized, revealing an unexpected strong tendency to give cationic complexes, and notably [(ArC=NR)Pd(CNR)₃]⁺ with excess isocyanide and [(ArC=NR)Pd( )(CNR)]⁺ with bidentate phosphines ( ). These species may be responsible for catalyst deactivation and side‐reactions. Ab initio calculations performed at the DFT level allowed us to rationalize the multiple roles of RNC in the different steps of the catalytic cycle.     

Spectroscopic,electrochemical, and structural aspects of the Ce(IV)/Ce(III) DOTA redox couple chemistry in aqueous solutions

The redox potential of the Ce(IV)/Ce(III) DOTA is determined to be 0.65 V versus SCE, pointing out a stabilization of ~13 orders of magnitude for the Ce(IV)DOTA complex, as compared to Ce(IV)_aq. The Ce(III)DOTA after electrochemical oxidation yields a Ce(IV)DOTA complex with a t_1/2 ~3 h and which is suggested to retain the “in cage” geometry. Chemical oxidation of Ce(III)DOTA by diperoxosulfate renders a similar Ce(IV)DOTA complex with the same t_1/2. From the electrochemical measurements, one calculates logK (Ce(IV)DOTA^2?) ~ 35.9. Surprisingly, when Ce(IV)DOTA is obtained by mixing Ce(IV)_aq with DOTA, a different species is obtained with a 2 : 1(M : L) stoichiometry. This new complex, Ce(IV)DOTACe(IV), shows redox and spectroscopic features which are different from the electrochemically prepared Ce(IV)DOTA. When one uses thiosulfate as a reducing agent of Ce(IV)DOTACe(IV), one gets a prolonged lifetime of the latter. The reductant seems to serve primarily as a coordinating ligand with a geometry which does not facilitate inner sphere electron transfer. The reduction process rate in this case could be dictated by an outer sphere electron transfer or DOTA exchange by S₂O₃^2?. Both Ce(IV)DOTA and Ce(IV)DOTACe(IV) have similar kinetic stability and presumably decompose via decarboxylation of the polyaminocarboxylate ligand.     

Different Spin‐State Behaviors in Isostructural Solvates of a Molecular Iron(II) Complex

The complex [FeL₂][BF₄]₂ ( 1 ; L=4‐(isopropylsulfanyl)‐2,6‐di(pyrazol‐1‐yl)pyridine) forms solvate crystals 1 ?solv (solv=MeNO₂, MeCN, EtCN, or Me₂CO). Most of these materials lose their solvent sluggishly on heating. However, heating 1 ?MeNO₂ at 450 K, or storing 1 ?EtCN under ambient conditions, leads to single‐crystal to single‐crystal exchange of the organic solvent for atmospheric moisture, forming 1 ?H₂O. Solvent‐free 1 ( 1 ?sf) can be generated in situ by annealing 1 ?H₂O at 370 K in the diffractometer or magnetometer. The different forms of 1 are isostructural (P2₁/c, Z=4) and most of them exhibit spin‐crossover (SCO) at 141≤T ≤212 K, depending on their solvent content. The exception is the EtCN solvate, whose pristine crystals remain high‐spin between 3–300 K. The cooperativity of the spin‐transitions depends on the solvent, ranging from gradual and incomplete when solv=acetone to abrupt with 17 K hysteresis when solv=MeCN. Our previously proposed relationship between molecular structure and SCO explains some of these observations, but there is no single structural feature that correlates with SCO in all the 1 ?solv materials. However, changes to the unit cell dimensions during SCO differ significantly between the solvates, and correlate with the SCO cooperativity. In particular, the percentage change in unit cell volume during SCO for the most cooperative material, 1 ?MeCN, is 10 times smaller than for the other 1 ?solv crystals.     

Straightforward and Controlled Shape Access to Efficient Macrocyclic Imidazolylboronium Anion Receptors

A straightforward synthesis of air‐ and water‐stable bis‐cationic macrocyclic imidazolylboronium anion receptors is described herein. By taking advantage of the bulky and rigid 9‐borabicyclo[3.3.1]‐nonane (9‐BBN) attaching point and a well‐designed bis‐imidazolylaryl, highly stable dimeric imidazolylboronium macrocycles were synthesized. Additionally, NMR spectroscopy (¹H, DOSY, and HOESY), mass spectrometry (MS), and X‐ray diffraction studies revealed that these macrocyclic scaffolds can bind several monoanions with high association constants in DMSO, and are particularly sensitive for the MS detection of anions (with concentrations in the nm range). This anion/receptor interaction involves eight C?H binding sites, which include C ?H and unusual C_sp3?H hydrogen‐bonding donors.