Synthesis,IR Spectra,Thermal Analysis and Crystal Structures of Bis(saccharinato)mercury(II) Complexes with 2–Aminomethylpyridine and 2–Aminoethylpyridine

Two bis(saccharinato) (sac) complexes of mercury(II) with 2–aminomethylpyridine (ampy) and 2–aminoethylpyridine (aepy) were synthesized and characterized by means of elemental analysis, FT–IR spectroscopy and thermal analysis and single crystal X–ray diffraction. trans–[Hg(sac)₂(ampy)₂] ( 1 ) crystallizes in the monoclinic space group P2₁/c [a = 10.8274(4), b = 16.4903(6), c = 7.7889(3) Å; β = 99.500(1)°] and [Hg(sac)₂(aepy)] ( 2 ) also crystallizes monoclinic in space group P2₁/n [a = 9.0423(4), b = 14.0594(6), c = 18.0146(8) Å; ß = 98.806(1)°]. Both 1 and 2 consist of neutral monomeric units. The mercury(II) ion in 1 lies on an inversion centre and exhibit distorted octahedral coordination by two sac anions and two ampy ligands, whereas the mercury(II) ion in 2 is tetrahedrally coordinated by an aepy and two sac ligands. The sac ligands in both complexes are N–coordinated, while the ampy and aepy ligands act as a bidentate ligand forming two symmetrically chelate rings around the mercury(II) ion.     

N‐(2‐Hydroxyethyl)ethylenediammonium hydrogenphosphate monohydrate

The title compound, C₄H₁₄N₂O²⁺·HPO₄^2?·H₂O, contains alternating interleaved layers of hydrogenphosphate and N‐(2‐hydroxyethyl)ethyl­enedi­ammonium moieties. The water mol­ecules are associated with channel‐like voids in the structure and a network of hydrogen bonds stabilizes the crystal packing.     

trans‐Bis(diethanolamine‐N,O)bis(saccharinato‐N)cadmium(II)

The structure of the title complex consists of isolated [Cd(C₇H₄NO₃S)₂(C₄H₁₁NO₂)₂] units. The Cd²⁺ cation lies on an inversion centre and is octahedrally coordinated by two N,O‐bidentate diethanol­amine (dea) and two N‐bonded saccharinate (sac) ligands [saccharin is 1,2‐benziso­thia­zol‐3(2H)‐one 1,1‐dioxide]. The dea ligands constitute the equatorial plane of the octahedron, forming two five‐membered chelate rings around the Cd^II ion, while the sac ligands are localized at the axial positions. The Cd—N_sac, Cd—N_dea and Cd—O_dea bond distances are 2.3879 (12), 2.3544 (14) and 2.3702 (13) Å, respectively. The H atoms of the free and coordinated hydroxyl groups of the dea ligands are involved in hydrogen bonding with the carbonyl and sulfonyl O atoms of the neighbouring sac ions, while the amine H atom forms a hydrogen bond with the free hydroxyl O atom. The individual mol­ecules are held together by strong hydrogen bonds, forming an infinite three‐dimensional network.     

Comparison of the ATP binding sites of protein kinases using conformationally diverse bisindolylmaleimides

The conformation of a bisindolylmaleimide may be controlled by the size of a macrocyclic ring in which it is constrained. A range of techniques were used to demonstrate that the tether controls both the ratio of the two limiting conformers (syn and anti) in solution and the extent of conjugation between the maleimide and indole rings. Screening the conformationally diverse bisindolylmaleimides against a panel of protein kinases allowed their ATP binding sites to be compared using a chemical approach which, like sequence alignment, does not require detailed structural information. This approach lead to the conclusion that several AGC group protein kinases (including PKCalpha, PKCbeta, MSK1, p70 S6K, PDK-1, and MAPKAP-K1alpha) may be best inhibited by bisindolylmaleimides which adopt a compressed approximately C2-symmetric anti conformation; in constrast, GSK3beta may be best inhibited by bisindolylmaleimides whose ground state is a distorted syn conformation. It is concluded that PDK-1, whose structure has been determined by X-ray crystallography, and its mutants, may serve as particularly useful surrogates for the study of PKC inhibitors.     

A Novel 1D Coordination Polymer [Pb(phen)(μ‐N3)(μ‐NO3)]n with the First Pb2‐(μ‐N3)2 Unit (phen = 1,10‐phenanthroline)

A novel 1D polymeric lead(II) complex containing the first Pb₂‐(μ‐N₃)₂ motif, [Pb(phen)(μ‐N₃)(μ‐NO₃)]_n (phen = 1,10‐phenanthroline), has been synthesized and characterized. The single‐crystal X‐ray data showed the coordination number of Pb²⁺ ions to be eight (PbN₄O₄) with the Pb²⁺ ions having “stereo‐chemically active” electron lone pairs; the coordination sphere is hemidirected. The chains interact with each other via π‐π interactions to create a 3D framework.     

Acetylsalicylhydroxamic acid and its cobalt(II), nickel(II), copper(II) and zinc(II) complexes

Acetylsalicylhydroxamic acid (AcSHA) was prepared and characterized. Its pK_a value was determined as 7.78. Solid metal complexes of AcSHA were also prepared and characterized by elemental analysis, electronic and i.r. spectroscopies, and by magnetic moment measurements. The shift of both hydroxamic and acetyl carbonyl vibrations to lower frequencies clearly indicates that AcSHA is bonded through oxygen atoms to the metal ions as a tridentate ligand. On the basis of the experimental data, structures for the complexes are purposed.     

Bis­(saccharinato‐κN)zinc(II) com­plexes with N,N′‐bidentate 2‐amino­methyl­pyridine and 2‐amino­ethylpyridine

The structures of trans‐bis[2‐(amino­methyl)­pyridine‐κ²N,N′]­bis­(saccharinato‐κN)­zinc(II), [Zn(C₇H₄NO₃S)₂(C₆H₈N₂)₂], (I), and [2‐(amino­ethyl)­pyridine‐κ²N,N′]bis­(saccharinato‐κN)­zinc(II), [Zn(C₇H₄NO₃S)₂(C₇H₁₀N₂)], (II), exhibit octa‐ and tetrahedrally coordinated Zn^II atoms, respectively. The di­amine ligands behave as N,N′‐bidentate ligands, while saccharinate (sac) is coordinated through the N atom. In (I), the complex lies about an inversion centre with the Zn atom disordered and displaced by 0.256 (2) Å from a centre of symmetry towards a sac N atom. The crystal structure of (I) is stabilized by N—H⋯O hydrogen bonds and the crystal packing of (II) is determined by hydrogen bonding as well as weak π–π stacking interactions between the sac ligands.     

Sizing problem for a cross flow heat exchanger with wing-type vortex generator

In the present study, sizing of a single pass cross flow heat exchanger with unmixed fluid streams has been investigated. The heat exchanger is a cross flow heat exchanger. It has overall dimensions of 20 × 20 × 20 cm. Two the most common heat exchanger design problems are the rating and sizing problem. Sizing problems deal with designing an exchanger and determining its physical size to meet the specified heat duty, pressure drops and other considerations. It means the determination of the exchanger construction type, flow arrangement, heat transfer surface geometries and materials, and the physical sizes of an exchanger to meet specified heat transfer and pressure drop. In this study, the physical size (length, width, height, mass flow rates of both fluids and surface areas on each side of the exchanger) are determined. Inputs to the sizing problem are surface geometries, fluid mass flow rates, inlet and outlet fluid temperatures and pressure drop on each side. Dimensions of L _a , L _b , and L _c for the selected surfaces were investigated such that the design meets the heat duty and pressure drops on both sides exactly.     

Femtosecond electron-transfer reactions in mono- and polynucleotides and in DNA

Quenching of redox active, intercalating dyes by guanine bases in DNA can occur on a femtosecond time scale both in DNA and in nucleotide complexes. Notwithstanding the ultrafast rate coefficients, we find that a classical, nonadiabatic Marcus model for electron transfer explains the experimental observations, which allows us to estimate the electronic coupling (330 cm(-1)) and reorganization (8070 cm(-1)) energies involved for thionine-[poly(dG-dC)](2) complexes. Making the simplifying assumption that other charged, pi-stacked DNA intercalators also have approximately these same values, the electron-transfer rate coefficients as a function of the driving force, DeltaG, are derived for similar molecules. The rate of electron transfer is found to be independent of the speed of molecular reorientation. Electron transfer to the thionine singlet excited state from DNA obtained from calf thymus, salmon testes, and the bacterium, micrococcus luteus (lysodeikticus) containing different fractions of G-C pairs, has also been studied. Using a Monte Carlo model for electron transfer in DNA and allowing for reaction of the dye with the nearest 10 bases in the chain, the distance dependence scaling parameter, beta, is found to be 0.8 +/- 0.1 A(-1). The model also predicts the redox potential for guanine dimers, and we find this to be close to the value for isolated guanine bases. Additionally, we find that the pyrimidine bases are barriers to efficient electron transfer within the superexchange limit, and we also infer from this model that the electrons do not cross between strands on the picosecond time scale; that is, the electronic coupling occurs predominantly through the pi-stack and is not increased substantially by the presence of hydrogen bonding within the duplex. We conclude that long-range electron transfer in DNA is not exceptionally fast as would be expected if DNA behaved as a "molecular wire" but nor is it as slow as is seen in proteins, which do not benefit from pi-stacking.     

The First Calcium(II) Complex with the Saccharinate Ligand: Synthesis,Crystal Structure,Spectral and Thermal Characterization of Trans—diaquabis[(2—hydroxyethyl)pyridinium]bis(saccharinato)calcium(II) Disaccharinate, [Ca(sac)2(H2O)2(Hpyet)2](sac)2

A new calcium(II) complex of the saccharinate ligand (sac) with 2—hydroxyethylpyridinium (Hpyet) was synthesized and characterized by elemental analysis, FT—IR spectroscopy, thermal analysis and single crystal X—ray diffractometry. The [Ca(sac)₂(H₂O)₂(Hpyet)₂](sac)₂ complex crystallizes in the triclinic space group (P1¯) with the cell dimensions a = 7.4360(7)Å, b = 12.5263(12)Å, c = 12.8329(13)Å, α = 82.534(8)°, β = 75.202(8)° and γ = 89.662(8)° (293 K). The title complex consists of a complex cation and two sac anions. In the complex cation, the calcium(II) ion is six—coordinate, bonding to two aqua ligands, two Hpyet ligands andtwo sac ligands located in the trans positions. Two of the sac ions are coordinated to the calcium(II) ion through the carbonyl O atom, while the other two remain outside the coordination sphere as the counter—ions. Thermal decomposition of the complex in air results in elimination of aqua, Hpyet, and sac ions, respectively.