Structure Of Bis Research Articles

2-chloro-3,3,5-trimethyl-2,3-dihydro-1,2λ5-oxaphosphole 2-oxide as precursor in a new synthesis of dialkyl(diaryl)-(2-methyl-4-oxopent-2-yl)phosphine oxides

A new approach has been developed to the synthesis of dialkyl(diaryl)(2-methyl-4-oxopent-2-yl)-phosphine oxides that are structural analogs of the drug dimephosphon. This approach is based on the reaction of 2-chloro-3,3,5-trimethyl-3H-1,2λ5-oxaphosphole 2-oxide with Grignard compounds, and it ensures high yields of the target products. The structure of bis(2-methoxyphenyl)(2-methyl-4-oxopent-2-yl)phosphine oxide was determined by X-ray analysis. (2-Methyl-4-oxopent-2-yl)dipropylphosphine oxide with magnesium bromide formed a 4: 1 complex whose structure was also determined by X-ray analysis.

Nucleophilic Aromatic Substitution of Bis(pentafluorophenyl)mercury with Various Bulky Nucleophiles and the Structures of [Hg(C6F4X-4)2] (X=cyclo-C5H10N, OCH(CH3)2, OC(CH3)3)

Reactions of bis(pentafluorophenyl)mercury with piperidine, sodium iso-propoxide or sodium tert-butoxide have yielded the corresponding 4-substituted tetrafluorophenylmercurials, [Hg(C6F4X-4)2] (X = cyclo-C5H10N (1), OCH(CH3)2 (2), OC(CH3)3 (3)), in reasonable yields but the bulkier nucleophiles, cis-2,6-dimethylpiperidine and 2,6-di-iso-propylphenolate (from sodium 2,6-di-iso-propylphenolate) decomposed the mercurial into pentafluorobenzene. Treatment of bis(pentafluorophenyl)mercury with another bulky nucleophile, 2,6-diphenylphenolate (from sodium 2,6-diphenylphenolate), in methanol, resulted in the unexpected formation of [Hg(C6F4(OMe)-4)2] (4). The structures of all the mercurials have linear C–Hg–C stereochemistry with two coplanar aryl rings. Amongst a complex series of supramolecular interactions, Hg⋯O bonding is observed for the alkoxy substituted mercurials but there are no Hg⋯N interactions in the structure of bis(2,3,5,6-tetrafluoro-4-piperidinophenyl)mercury.

Solvent-templated supramolecular isomerism in 2D coordination polymer constructed by NiII2CoII nodes and dicyanamido spacers: drastic change in magnetic behaviours

Two heterometallic coordination polymers (CPs) have been prepared using [Ni(II)L]2Co(II) (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) as nodes and dicyanamido spacers by varying the solvent for synthesis. Structural characterizations revealed that methanol assisted the formation of a two-dimensional (4,4) connected rhombic grid network of [(NiL)2Co(NCNCN)2]∞ (1a) whereas relatively less polar acetonitrile afforded a different superstructure {[(NiL)2Co(NCNCN)2]·CH3CN}∞ (1b) with a two-dimensional (4,4) connected square grid network. The presence of acetonitrile molecules in the structure of 1b seems to change the spatial orientation of the terminal metalloligands [NiL] from pseudo-eclipsed in 1a to staggered-like in 1b around the central Co(II). These structural changes in the nodes together with the conformationally flexible dicyanamido spacers, which are cis coordinated to the Co(II) in both trinuclear units, led to the differences in the final 2D network. Variable-temperature magnetic susceptibility measurements revealed that this supramolecular isomerism led to a drastic transition from spin-frustrated antiferromagnetism for 1a to a dominant ferromagnetic behaviour for 1b. The geometrical differences in Ni2Co coordination clusters (CCs) which are scalene triangular in 1a but nearly linear in 1b, are held responsible for the changes of the magnetic properties. The DFT calculations of exchange interactions between metal centres provide a clear evidence of the role played by the fundamental geometrical factors on the nature and magnitude of the magnetic coupling in these pseudo-polymorphic CPs.

Synthesis and X-ray Crystal Structure of Bis(<i>O</i>-propylxanthato)-bis(3-chloropyridine)nickel(II)

Synthesis and X-ray Crystal Structure of Bis(<i>O</i>-propylxanthato)-bis(3-chloropyridine)nickel(II)

Silver(I) ferrocenylcarboxylate: Reactivity and reaction behavior toward phosphines and phosphites

Silver(I) ferrocenylcarboxylate [Fe(η5-C5H4CO2Ag)(η5-C5H5)] (1) subsequently decarboxylates either in boiling dichloromethane or tetrahydrofuran to give biferrocene [Fe(η5-C5H4)(η5-C5H5)]2 (2) and elemental silver. Phosphine silver(I) ferrocenylcarboxylates of type [Fe(η5-C5H4CO2Ag(PR3)n)(η5-C5H5)] (R = Ph: 4a, n = 1; 4b, n = 2; 4c, n = 3. R = n-Bu: 5a, n = 1; 5b, n = 2; 5c, n = 3. R = OMe: 6a, n = 1; 6b, n = 2; 6c, n = 3) are accessible by treatment of 1 with PR3 (3a, R = Ph; 3b, R = n-Bu; 3c, R = OMe) in the ratio of 1:n. With dppe (7) tetrametallic [Fe(η5-C5H4CO2Ag(μ-dppe))(η5-C5H5)]2 (8) (dppe = Ph2PCH2CH2PPh2) was formed. The structures of 4b and 8 in the solid state have been determined by single X-ray structure determination. In 4b the silver(I) ion possesses a pseudo-tetrahedral environment, whereby the four coordination sites are occupied by the chelated FcCO2 unit and two datively-bonded PPh3 ligands. Compound 8 forms in the solid state a dimer setup by a [Ag(μ-dppe)]2 central building block. The FcCO2 groups are chelated to Ag(I) thus resulting in a pseudo-tetrahedral coordination sphere at silver. The solution behavior of 4–6 was analyzed by temperature-dependent 31P{1H} NMR studies indicating ligand exchange processes.

Investigation into the crystal structure of bis(pyridine)-bis(trichloroacetato) copper(II) and its electrophotochemical properties

A novel chained Cu(II) complex was synthesized from trichloroacetato copper(II) and pyridine in ethanol solvent, and characterized by elemental analysis and infrared (IR) spectroscopy. The special crystal structure of the Cu(II) complex was determined by X-ray single-crystal diffraction. The results indicate that a chained structure of the Cu(II) complex formed through intermolecular hydrogen bonds. Cu(CCl3COO)2(C5H5N)2(H2O) was monoclinic, with unit cell P21/c and cell parameters as follows: a = 14.389(3) A, b = 7.1911(14) A, c = 23.107(8) A, V = 2,257.5(10) A3, Z = 4, M r = 564.51, D c = 1.661 mg/m3, T = 293(2) K, F(000) = 1,124, μ(Mo Kα) = 1.704 mm−1, R = 0.0984, and ωR = 0.2791. The electrochemical behavior of the Cu(II) complex on a glassy carbon working electrode determined by cyclic voltammetry showed the electrochemical activity of the title compound at 0.2 to −0.3 V (versus SCE) in NH3–NH4Cl buffer solution (pH 9.2), and the redox peak current of the complex had a good linear relationship with the square root of the scan rate in the range 0.02–0.2 V/s.

Structure, electronic, and CV properties of hydroxy-naphthaldehyde Schiff-base copper(II) complexes derived from alkyl amines: X-ray structure of bis(n-i-propyl-3-hydroxy-2-naphthaldiminato)copper(II)

Copper(II) complexes with Schiff bases derived from linear and branched amines with 2-hydroxy-1-naphthaldehyde and 3-hydroxy-2-naphthaldehyde were synthesized and characterized by IR and electronic spectroscopies, magnetic susceptibilities, electrochemistry, cyclic voltammetry (CV), X-ray diffraction, and theoretical calculations. Electronic spectra are a function of the R group on the imine nitrogen of the ligand that determines steric effects. Complexes obtained from 3-hydroxy-2-naphthaldehyde ligand are more distorted from planarity in dimethylformamide solutions than those of 2-hydroxy-1-naphthaldehyde for the same R group. As a result, the former are easier to reduce to the related copper(I) complexes than those of 2-hydroxy-1-naphthaldiminate. The structure of bis(N-i-propyl-3-hydroxy-2-naphthaldiminato)copper(II) was determined by single-crystal X-ray diffraction. Its molecular structure can be described as distorted flat tetrahedral influenced by important packing effects and is flatter than that calculated with density functional theory methods. Additional related flat tetrahedral complexes were studied by theoretical calculations and it has been found that electronic effects also play a significant role.

Boronium‐Cation‐Based Ionic Liquids as Hypergolic Fluids

Two series of boronium-cation-based ionic liquids were prepared and fully characterized by (1)H, (13)C, and (11)B NMR and infrared spectroscopy, differential scanning calorimetry (DSC), and elemental analysis. The structure of bis(1-methyl-1H-imidazole-3-yl)dihydroboronium dicyanoborohydride (5 a) was determined by single-crystal X-ray diffraction. The densities of these ionic liquids range from 1.05 to 1.28 g cm(-3), and the heats of formation, predicted on the basis of Gaussian 03 calculations, fall between -164.6 and 430.5 kJ mol(-1). Compound 5 b, bis(1-allyl-1H-imidazole-3-yl)dihydroboronium dicyanoborohydride, exhibits the lowest viscosity (35 mPa s) and shortest ignition-delay time (14 ms) in combination with 100 % HNO(3).

Improved Synthesis of No-Carrier-Added [*I]MIBG and Its Precursor

3-(Trimethylstannyl)benzyl alcohol was coupled in a Mitsunobu reaction with bis(Boc)-guanidine to give bis(Boc)-protected 3-(trimethylstannyl)benzylguanidine used as precursor for [*I]MIBG. Radioiodination with [¹³¹I]iodine generated from [¹³¹I]NaI and chloramine-T, removal of Boc groups, and purification by HPLC gave no-carrier-added tracer [*I]MIBG (81% radiochemical yield, 99% chemical purity) used for imaging tumors of neuroendocrine origin. The structures of bis(Boc)-guanidine and bis(Boc)-protected 3-(trimethylstannyl)benzylguanidine were secured by single crystal X-ray structure analyses.

Synthesis and structure of bis- and tris-ferrocene containing N-methylimide foldamers

The synthesis and conformational analysis of dimer Fc–CO–NMe–CO–Fc (5) and trimer Fc–CO–NMe–CO–Fn–CO–NMe–CO–Fc (6) have been described. It has been shown by means of spectroscopic studies, X-ray crystallography, and molecular modeling, that these molecules are dominated by cis–cis conformation. Furthermore, we recognized for the first time, that such type of organometallics possess elements of chiral helicity. Their crystal lattices are characterized by π–π and CH–π intermolecular interactions (5) and by CH⋯OC intermolecular hydrogen bonds (6). We believe that foldamers 5/6 are stabilized by the special type of aromatic π–π interactions between the closer cyclopentadienyl rings of the juxtaposed ferrocene units.

Synthesis of Bis-(Tributyl citrate acid)esters as Novel Green Plasticizers

Citrate esters were used as plasticizers in many kinds of plastic resins. Several compounds with new structure of bis-(tribytyl citrate acid) esters have been synthesized via an environmentally friendly way with relatively high yields. The structure of each compound has been verified by MS and NMR spectra analysis. The properties of these plasticizers have been evaluated by weight loss percentage in soybean oil. The various parameters have been calculated to correlate with their properties. The result showed that weight loss percentages are associated with steric parameters. It was also found that some of the new compounds showed better weight loss ability than traditional plasticizers.

Modulation of Metallophilic Bonds: Solvent-Induced Isomerization and Luminescence Vapochromism of a Polymorphic Au–Cu Cluster

We report a homoleptic Au-Cu alkynyl cluster that represents an unexplored class of luminescent materials with stimuli-responsive photophysical properties. The bimetallic complex formulated as [Au(2)Cu(2)(C(2)OHC(5)H(8))(4)](n) efficiently self-assembles from Au(SC(4)H(8))Cl, Cu(NCMe)(4)PF(6), and 1-ethynylcyclopentanol in the presence of NEt(3). This compound shows remarkably diverse polymorphism arising from the modulation of metallophilic interactions by organic solvents. Four crystalline forms, obtained from methanol (1a); ethanol, acetone, or choloroform (1b); toluene (1c); and diethyl ether or ethyl acetate (1d), demonstrate different photoluminescent characteristics. The solid-state quantum yields of phosphorescence (Φ) vary from 0.1% (1a) to 25% (1d), depending on the character of intermetallic bonding. The structures of 1b-d were determined by single-crystal X-ray diffraction. The ethanol (1b, Φ = 2%) and toluene (1c, Φ = 10%) solvates of [Au(2)Cu(2)(C(2)OHC(5)H(8))(4)](n) adopt octanuclear isomeric structures (n = 2), while 1d (Φ = 25%) is a solvent-free chain polymer built from two types of Au(4)Cu(4) units. Electronic structure calculations show that the dramatic enhancement of the emission intensity is correlated with the increasing role of metal-metal bonding. The latter makes the emission progressively more metal-centered in the order 1b < 1c < 1d. The metallophilic contacts in 1a-d show high sensitivity to the vapors of certain solvents, which effectively induce unusual solid-state isomerization and switching of the absorption and luminescence properties via non-covalent interactions. The reported polymorphic material is the first example of a gold(I) alkynyl compound demonstrating vapochromic behavior.

Antineoplastic Agents. 587. Isolation and Structure of 3-Epipancratistatin from Narcissus cv. Ice Follies

Bioassay-guided (cancer cell line) separation of an extract prepared from Narcissus cv. Ice Follies (from The Netherlands) led to the isolation of a new Amaryllidaceae isocarbostiryl, 3-epipancratistatin (1b), as well as narciclasine (2). This Narcissus cultivar was found to be a good source of narciclasine. The structure of 1b was established by high-resolution mass and high-field 2D NMR spectroscopic analyses. Against a panel of murine and human cancer cell lines, 3-epipancratistatin (1b) led to cell growth inhibition (GI(50) 2.2-0.69 μg/mL) some 100× less than that found for pancratistatin (1a) and narciclasine (2), thereby revealing an important configurational requirement in 1a for strong cancer cell growth inhibition.

Polymorphism in 3,4-bis(2-benzimidazolyl)pyridine: Controlled synthesis, crystal structures and photophysical properties

Abstract Two polymorphs of 3,4-bis(2-benzimidazolyl)pyridine (1) were prepared and characterized by infrared, nuclear magnetic resonance spectroscopy and single-crystal X-ray crystallography. The metastable greenish polymorph 1a (hexagonal space group P6522) was solvothermally formed first, which can be irreversibly transformed into the stable yellow polymorph 1b (orthorhombic space group Pbcn) on heating or recrystallization. The structure of 1a shows a dihedral angle of 45.3° between the benzimidazolyl/pyridyl rings and a dihedral angle of 52.2° between the benzimidazolyl/benzimidazolyl rings, while the corresponding dihedral angles in the structure of 1b are 48.0° and 67.9°, respectively. The two polymorphs exhibit different combination of intermolecular interactions (N–H⋯N hydrogen bonds, π–π stacking or C–H⋯π interaction), leading to significantly different supramolecular assemblies. The photophysical properties of 1a and 1b have also been studied.

Influence of counterions on the structure of bis(oxazoline)copper(ii) complexes; an EPR and ENDOR investigation

X- and Q-band EPR and ENDOR spectroscopy was used to study the structure of a series of heteroleptic and homoleptic copper bis(oxazoline) complexes, based on the (-)-2,2'-isopropylidenebis[(4S)-4-phenyl-2-oxazoline] ligand and bearing different counterions (chloride versus triflate); labelled [Cu(II)(1a-c)]. The geometry of the two heteroleptic complexes, [Cu(II)(1a)] and [Cu(II)(1c)], depended on the choice of counterion. Formation of the homoleptic complex was only evident when the Cu(II)(OTf)(2) salt was used (Cu(II)(Cl)(2) inhibited the transformation from heteroleptic to homoleptic complexes). The hyperfine and quadrupole parameters for the surrounding ligand nuclei were determined by ENDOR. Well resolved (19)F and (1)H couplings confirmed the presence of both coordinated water and TfO(-) counterions in [Cu(1a)].

Self-assembly of alkyl N-acetylglyoxylic amides of varying chain lengths

Alkyl N-acetylglyoxylic amides have been synthesised from N-acetylisatins and their self-assembly studied in the solid state by X-ray crystallography. Different molecular conformations were observed for molecules 5a, 5b, 5d and 6b, which have a strong influence on their supramolecular organization in the crystals. Both strong and weak interactions played key roles in the self-assembly process and the formation of well-defined supramolecular architectures. Crystal structures of 5b revealed novel CO⋯CO (carbonyl–carbonyl) dipolar interactions involving three carbonyl groups and intermolecular halogen bonding interactions, either C–H⋯Br contacts with inclusion of cyclohexane in 5b-1 or Br⋯Br contacts without the inclusion of solvent in 5b-2.

Binuclear copper(II) complexes of 1-amidino-O-alkylurea (alkyl = n-propyl, n-butyl, or i-butyl) and vanadate: an EPR study

Five new complexes of bis(1-amidino-O-alkylurea)Cu(II)vanadate where alkyl = methyl, ethyl, n-propyl, n-butyl or i-butyl have been synthesized by reaction of ammonium metavanadate with bis(1-amidino-O-alkylurea)Cu(II)perchlorate complexes. Electron paramagnetic resonance (EPR) spectra of bis(1-amidino-O-n-propylurea)Cu(II)vanadate (1), bis(1-amidino-O-n-butylurea)Cu(II)vanadate (2) and bis(1-amidino-O-i-butylurea)Cu(II)vanadate (3) gave half-field signal (ΔM s = ±2) ca 1623G, in addition to fine structure due to zero field splitting (ZFS) characteristics of the S = 1 system. From the observed ZFS the average Cu–Cu distance was estimated. The isotropic exchange constant J was evaluated by recording EPR spectra at different temperatures. The photoacoustic signal of the complexes indicated square-planar geometry around Cu2+. X-ray powder diffraction studies on 2 suggested orthorhombic structure with unit cell dimensions a = 21.11 Å, b = 24.11 Å, c = 27.11 Å, α = β = γ = 90°. The crystal structure of bis(1-amidino-O-n-butylurea)Cu(II)perchlorate is also reported.

NMR spectral and structural studies on some xanthenones and their thiosemicarbazone derivatives: Crystal and molecular structure of 12-(2-chlorophenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one

Abstract A series of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones [ 1a – 9a ] were prepared employing a three component one-pot reaction of aryl aldehyde, 2-naphthol and 1,3-cyclohexanedione using BF 3 ·OEt 2 as catalyst. Thiosemicarbazone derivatives [ 1b – 5b ] were also prepared in the presence of acid catalyst. All the synthesized compounds have been characterized by IR and NMR. The structure of 5b was confirmed by HSQC spectral analysis. Single crystal X-ray structural analysis of 12-(2-chlorophenyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one evidences the envelope and flattened-boat conformations of cyclohexenone and pyran rings respectively.

Synthesis and spectral studies of Ni(II) heterocyclic dithiocarbamates with S2PN chromophore: X-ray crystal structures of bis(1,2,3,4-tetrahydroquinolinecarbodithioato- S,S′)nickel(II) and 1,2,3,4-tetrahydroquinolinecarbodithioato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Synthesis and spectral studies of Ni(II) heterocyclic dithiocarbamates with S2PN chromophore: X-ray crystal structures of bis(1,2,3,4-tetrahydroquinolinecarbodithioato- S,S′)nickel(II) and 1,2,3,4-tetrahydroquinolinecarbodithioato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Synthesis, Characterization, and Crystal Structure of Bis(2,2′-Dipyridyl) (Nitropyridylsulfide) Ruthenium(II) (Hexafluorophosphate)

The S‒S bond undergoes a reductive cleavage when 2,2′-dithiobis(5-nitropyridine) is reacted with Ru(bpy)2Cl2 (bpy = 2,2′-bipyridine) and yields the monocationic species [Ru(bpy)2(S-Py-NO2)]+. The synthesized complex Ru(N5S)+ was characterized by UV-visible (UV-Vis), cyclic voltammetry, FT-IR, 1H-NMR, and X-ray. The 1H-NMR spectra show a set of signals according to low complex symmetry. The electrochemistry analysis showed a quasi-reversible RuIII/II wave observed at 0.78 V versus Ag/AgCl. X-ray structural analysis revealed a distorted octahedral coordination sphere around the metal. The octahedral N5S chromophore surrounding the metal ion is formed via two trans N and S atoms and four nitrogen atoms from two bis(2,2′-bipyridiyl) ligands. The distortion provoked by an N,S-schelating short-bite ligand has already been shown in similar derivatives. In the title compound, this effect is more dramatic since the four-membered ring presents more strain, and this effect is similar to the previously analyzed four-membered N,S-chelating short-bite ligand.