Hydrogen Bonded, π···π Stacked and X···π Framework Structures in Bis(2,6-Lutidinium) Tetrahalocuprate(II) Complexes

Abstract  

In the crystal structures of (2,6-lutidinium)₂[CuCl₄], 1 and (2,6-lutidinium)₂[CuBr₄], 2, the anion CuX₄ ²⁻ is connected to eight and four surrounding cations in 1 and 2, respectively, through (N–H···X) (H₂C–H···X) and (C–H···X) hydrogen bonds to form two-dimensional layers approximately normal to the crystallographic b-axis. These layers are further connected by means of offset face-to-face interactions (parallel to b-axis) to give three-dimensional structures. The hydrogen bonding (type and number) around each anion could be influenced by the anion size, as same cation is used, allowing different cation…anion interpenetrations.     

Peracid-induced ring opening of some hexahydro-2H-isoxazolo[2,3-a]pyridines to second-generation cyclic aldonitrones

A study of the stereo- and face selectivity of the cycloaddition reactions of several mono- and disubstituted alkenes with 4-hydroxymethyl-3,4,5,6-tetrahydropyridine 1-oxide has been carried out. The addition reactions have displayed a very high degree of face selectivity in the range 13-48:1. Use of dimethyl methylenemalonate as a protective group in nitrone cycloaddition reactions has been demonstrated. The invertomeric analysis revealed that the bicyclic cycloadducts remain predominantly as the cis-fused isomer, which leads to the formation of synthetically important second-generation cyclic aldonitrones via peracid oxidation. One interesting finding was that treatment of the cycloadducts with two equivalents of peracid afforded the cyclic N-hydroxy lactams, presumably via further oxidation of the aldonitrones. The piperidine ring has been elaborated by cycloaddition reaction of the second-generation nitrones with several alkenes, which in most cases gave the cycloadducts in a stereoselective manner.     

Exploring rearrangements along the fragmentation pathways of diuron anion: A combined experimental and computational investigation

Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), a common herbicide from phenyl urea class, was investigated by studying the formation of several negative ions [M−H]⁻ in the gas phase and the fragmentation behaviour of the thermodynamically most probably formed isomeric anions upon linear ion acceleration/collision experiments. The collision induced dissociation experiments (CID) were carried out in a hexapole–quadrupole–hexapole hybrid system coupled to 12 T magnet with infinity ICR cell for high resolution measurements. Two distinctive main pathways were observed in the MS/MS spectrum. Sustained off-resonance irradiation (SORI) experiments inside the ICR cell reinforce the fragmentation channels obtained from linear ion acceleration experiments. The fragmentation pathways were also completely investigated by the use of B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) level of theory. Elimination of dimethylamine takes place in a two-step process, by which two successive 1,3 proton shifts occur. The second 1,3 proton shift is concerted with the departure of dimethylamine. The driving force for the (CH₃)₂NH elimination is the formation of isocyanate group. The formed primary product ion can further decompose to release HCl through a new transition state. A stable new aromatic product ion is formed with 10π electrons. Loss of C₃H₅NO neutral from another anionic isomer of the precursor ion was also observed and is characteristic for the amide terminal of the diamide functional group. A concerted mechanism is proposed, by which N–C bond breakage and cyclization of the eliminated neutral fragment C₃H₅NO takes place simultaneously to form 1-methyl-aziridin-2-one.     

The Crystal Structures of Bis(2-amino-5-methylpyridinium) Tetrabromometallate(II): Intermolecular Interactions in (C<Subscript>6</Subscript>H<Subscript>9</Subscript>N<Subscript>2</Subscript>)<Subscript>2</Subscript>[MBr<Subscript>4</Subscript>]; M = Cd and Co

Abstract The crystallization and structures of a triclinic (henceforth T) (C₆H₉N₂)₂[CdBr₄] and a monoclinic (henceforth M) of (C₆H₉N₂)₂[CoBr₄] are reported. The crystal packing of both solids is analyzed and compared: both contain parallel chains of cations and stacks of anions. In both T and M, each [MBr₄]²⁻ is hydrogen bonded non-symmetrically to surrounding cations in a ladder chains that run along b axis, with planar cations in both structures falling in parallel to the planes to anions. In T the cation chains are further involved in classical π···π stacking, while in M the cation chains show less significant stacking, with longer repeat distance. Index Abstract Extensive N–H···Br hydrogen bonds link both anions and cations into chains of the ladder type parallel to the crystallographic b axis. The crystal structures of bis(2-amino-5-methylpyridinium) tetrabromometallate(II): Intermolecular interactions in (C6H9N2)2[MBr4]; M = Cd and Co Rawhi Al-Far and Basem Fares Ali      

Bee Venom: From Venom to Drug

Insects of the order Hymenoptera have a defensive substance that contains many biologically active compounds. Specifically, venom from honeybees (Apis mellifera) contains many enzymes and peptides that are effective against various diseases. Different research papers stated the possibility of using bee venom (a direct bee sting or in an injectable form) in treating several complications; either in vivo or in vitro. Other reports used the active fractions of bee venom clinically or at labratory scale. Many reports and publications have stated that bee venom and its constituents have multiple biological activities including anti-microbial, anti-protozoan, anti-cancer, anti-inflammatory, and anti-arthritic properties. The present review aims to refer to the use of bee venom itself or its fractions in treating several diseases and counteracting drug toxicities as an alternative protocol of therapy. The updated molecular mechanisms of actions of bee venom and its components are discussed in light of the previous updated publications. The review also summarizes the potential of venom loaded on nanoparticles as a drug delivery vehicle and its molecular mechanisms. Finally, the products of bee venom available in markets are also demonstrated.     

Detection of relic gravitational waves in thermal case by using Adv.LIGO data of GW150914

The thermal spectrum of relic gravitational waves enhances the usual spectrum. Our analysis shows that there exist some chances for detection of the thermal spectrum in addition to the usual spectrum by comparison with sensitivity of Adv.LIGO of GW150914 and detector based on the maser light. The behavior of the inflation and reheating stages are often known as power law expansion like \(S(\eta )\propto \eta ^{1+\beta }\), \(S(\eta )\propto \eta ^{1+\beta _s}\), respectively, with constraints \(1+\beta <0, 1+\beta _{s}>0\). The \(\beta \) and \(\beta _s\) have an unique effect on the shape of the spectrum. We find some values of the \(\beta \) and \(\beta _s\) by considering the mentioned comparison. As obtained, the results give us more information as regards the evolution of inflation and reheating stages.