Noncovalent supramolecular interactions in the crystal structure of 2-amino-3,5-dibromo-4,6-dimethylpyridinium tetrabromocadmate(II)

Reaction of 2-amino-4,6-dimethylpyridine with cadmium chloride, HBr and Br₂ in ethanol yeilds bis(2-amino-3,5-dibromo-4,6-dimethylpyridinium) tetrabromocadmate(II). The complex crystallizes in the monoclinic space group P2₁/c, with tetrahedral distortion of the ion. The cations are arranged in a zig-zag chains that are held together via Br···Br, Br···π, π···Br···π and π-π interactions. Extensive ···cation interactions were found and represented in different Br···HN (pyridinic and aminic) and Br···HCH₂ hydrogen bonding along with Br···Br motifs.     

Bis(2‐amino‐3,5‐dibromo‐4,6‐dimethyl­pyridinium) hexa­bromido­stannate(IV)

In the title compound, (C₇H₉Br₂N₂)₂[SnBr₆], the cations and centrosymmetric anions are stacked in alternating layers that show no significant inter­molecular inter­actions within each stack. Extensive cation⋯[SnBr₆]²⁻ inter­actions are found, represented by short Br⋯Br inter­actions, along with different Br⋯HN (pyridine and amine) and weaker Br⋯HCH₂ hydrogen‐bonding motifs.     

Substituted dipyridylpyridazine rhodium(III) complexes

3,6-Bis(2-pyridyl)pyridazine derivatives (n-dppn) react with hydrated rhodium(III) chloride and bromide (prepared in situ) to give cis-[Rh(n-dppn)₂Cl₂]PF₆·xH₂O (n = 5, 6, 7, 8) and cis-[Rh(n-dppn)₂Br₂]Br·xH₂O (n = 5, 7) complexes, which have been characterized by elemental analyses, conductivity measurements, i.r., electronic and ¹H- and ¹³C-n.m.r. spectra.     

Univalence of integral operators involving Bessel functions

In this note our aim is to deduce some sufficient conditions for integral operators involving Bessel functions of the first kind to be univalent in the open unit disk. The key tools in our proofs are the generalized versions of the well-known Ahlfors’ and Becker’s univalence criteria and some inequalities for the normalized Bessel functions of the first kind.     

A novel framework of N—H...Br hydrogen bonds forming Br(4,4′‐bipyridinium)4 supramolecular synthons: bis(4,4′‐bipyridinium) tris[tetrabromidoferrate(III)] bromide

In the asymmetric unit of the title compound, (C₁₀H₁₀N₂)₂[FeBr₄]₃Br, the Fe atoms are in a distorted tetrahedral environment. The crystal structure contains a novel arrangement of Br(4,4′‐bipyridinium)₄ supramolecular synthons assembled via short N—H...Br hydrogen bonds (H...Br = 2.55, 2.40, 2.38 and 2.55 Å), where four cations surround one nonbonded bromide ion in a tetrahedral arrangement. These synthons are further connected by hydrogen bonds using the remaining terminal NH hydrogens in each cation and the Br⁻ ions to form an adamantoid‐like network and thus produce a three‐dimensional supramolecular architecture with the [FeBr₄]⁻ ions located in the cavities. The structure shows no significant intermolecular Br...Br, Br...aryl or aryl–aryl interactions.     

Tuning the porosity of triangular supramolecular adsorbents for superior haloalkane isomer separations

Distillation-free separations of haloalkane isomers represents a persistent challenge for the chemical industry. Several classic molecular sorbents show high selectivity in the context of such separations; however, most suffer from limited tunability or poor stability. Herein, we report the results of a comparative study involving three trianglamine and trianglimine macrocycles as supramolecular adsorbents for the selective separation of halobutane isomers. Methylene-bridged trianglamine, TA, was found to capture preferentially 1-chlorobutane (1-CBU) from a mixture of 1-CBU and 2-chlorobutane (2-CBU) with a purity of 98.1%. It also separates 1-bromobutane (1-BBU) from a mixture of 1-BBU and 2-bromobutane (2-BBU) with a purity of 96.4%. The observed selectivity is ascribed to the thermodynamic stability of the TA-based host–guest complexes. Based on single crystal X-ray diffraction analyses, a [3]pseudorotaxane structure (2TA⊃1-CBU) is formed between TA and 1-CBU that is characterized by an increased level of noncovalent interactions compared to the corresponding [2]pseudorotaxane structure seen for TA⊃2-CBU. We believe that molecular sorbents that rely on specific molecular recognition events, such as the triangular pores detailed here, will prove useful as next generation sorbents in energy-efficient separations.

The methylene-bridged trianglamine (TA) can selectively capture 1-chlorobutane from a mixture of 1-chlorobutane and 2-chlorobutane due to the greater thermodynamic stability of the TA-based host–guest complex formed with 1-chlorobutane.     

Synthesis of 1,3,4-mercapto-oxadiazole mono- and dinuclear copper(I) and copper(II) complexes and their microbiological activity

Mono- and dinuclear Cu(I) and Cu(II) complexes of 1,3,4-mercapto-oxadiazole derivatives were prepared and characterized by elemental analyses and standard spectroscopic techniques. The complexes were formulated as Cu(G-OX)₂, Cu₂(G-OX)₄(H₂O)₄, Cu(G-OX)₂L₂and Cu₂(G-OX)₂(PPh₃)₂; (G = H, MeO, Cl; L = Ph₃P, Ph₃As). The microbiological activity of the complexes was investigated against bacteria and fungi. All the complexes were active against Candida albicans, while the reactivity against bacteria varied. The antimicrobial activity of the [Cu(MeO-OX)₂(H₂O)₂]₂ complex was exceptionally better than that observed for any other metal complex against both bacteria and fungi.     

The Adomian decomposition method for solving the Boussinesq equation arising in water wave propagation

We will consider the application of the Adomian decomposition method to approximate the solution of the Boussinesq equation. Both the well‐posed and the ill‐posed cases will be considered. The results obtained will be compared to the theoretical solution for single soliton wave. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006