The coordination chemistry of the hydrotris(3-diphenylmethylpyrazol-1-yl)borate (Tp(CHPh2)) ligand

The new ligand, hydrotris[3-(diphenylmethyl)pyrazol-1-yl]borate, Tp(CHPh2), has been synthesized and its coordination chemistry was compared with that of the analogous Tp(iPr). The new ligand was converted to a variety of complexes, such as M[Tp(CHPh2)]X (M = Co, Ni, Zn; X = Cl, NCO, NCS), Pd[Tp(CHPh2)][eta3-methallyl], Co[Tp(CHPh2)](acac), and Co[Tp(CHPh2)](scorpionate ligand). Compounds Tl[Tp(CHPh2)], 1, Co[Tp(CHPh2)]Cl, 2, Co[Tp(CHPh2)](NCS)(DMF), 3, Ni[Tp(CHPh2)](NCS)(DMF)2, 4, Co[Tp(CHPh2)](acac), 5, Co[Tp(CHPh2)][Ph2Bp], 6, Co[Tp(CHPh2)][Bp(Ph)], 7, Co[Tp(CHPh2)][Tp], 8, and (Ni[Tp(CHPh2)])2[C2O4](H2O)2, 9, were structurally characterized.     

Structure-Activity Relationships of Oxygenated Morphinans. I. 4-Mono- and 3,4-dimethoxy-N-methylmorphinans and -N-methyl-morphinan-6-ones with unusually high antinociceptive potency. Preliminary communication

The antinociceptive potency and receptor affinity of several optically active aromatic mono- and di-oxygenated N-methylmorphinans and N-methylmorphinan-6-ones, prepared from natural morphine, were determined. Thus, in order of antinociceptive potency, 4-methoxy-N-methylmorphinan-6-one ≈ 3,4-dimethoxy-N-methylmorphinan-6-one ≈ 3,4-dimethoxy-N-methylmorphinan > 4-methoxy-N-methylmorphinan ≈ 4-acetoxy-N-methylmorphinan-6-one > 4-acetoxy-N-methylmorphinan ≈ 4-hydroxy-N-methylmorphinan-6-one ≈ 4-hydroxy-N-methylmorphinan. The 4-hydroxy compounds were slightly less potent than morphine, and the 4-methoxy and 3,4-dimethoxy compounds were found to have three times the potency of morphine. 4-Methoxy-N-methylmorphinan-6-one showed an opiate receptor affinity one-third that of morphine; this is a remarkably high affinity for a non-phenolic compound.     

Two-loop electroweak parameters

A recent calculation of the electroweak parameter Δr, including the dominant two-loop contributions and resummation of large logarithms, is reformulated in terms of the dressed gauge-boson propagators and extended to the electroweak quantities measured at theZ peak such as the various partial widths and asymmetries. The formalism is simpler and physically more transparent. Large two-loop corrections specific to theZ→bb \(\bar b\) partial width are included consistently. A detailed statistical analysis is presented of the implications for the topquark and Higgs-boson masses from the latest precision measurements of theW-boson mass and theZ-boson partial widths.     

Dimethylmetal(III) pyrazolides

The complexes Me₂Au(R₂pz) (R = H, Me; pzH = pyrazole) are formed on reaction of dimethylgold(III) nitrate with 3,5-disubstituted pyrazoles, R₂pzH, in water, but a similar procedure with Ph₂pzH followed by recrystallization from CHCl₃/CCl₄ gives [Me₂Au(Ph₂pzH)₂]NO₃ · ca.$\text{3}\text{4}$CCl₄. The complexes Me₂(Ph₂pz) (M = Au, Tl), Me₂In(Ph₂pz)·$\text{1}\text{2}$CH₂Cl₂, and Me₂Tl(Me₂pz) are formed on reaction of Me₂MI (M = Au, Tl) or Me₂InCl with Ag(R₂pz) in nonaqueous solvents. The complexes Me₂Au(R₂pz) (R = H, Me, Ph) are dimeric in chloroform and Me₂Tl(Me₂pz) is dimeric in benzene, but osmometric data for Me₂Tl(Ph₂pz) in benzene indicate presence of a monomer—dimer equilibrium.     

Photoinactivation of hepatitis A virus by synthetic porphyrins

Porphyrins are photosensitizers and may be applicable in situations where viral inactivation is required, as for in vitro inactivation of nonenveloped viruses in blood components or in other aqueous media. No study has examined the efficacy of porphyrin inactivation on human pathogens such as hepatitis A virus (HAV) in plasma or other liquids. Experiments were conducted to evaluate the effect of synthetic porphyrins on HAV in porphyrin-containing human plasma and phosphate-buffered saline exposed to long-wavelength (365 nm) UV light. Inactivation of bacteriophage MS2 (MS2) also was determined in some trials. Solutions containing cationic, anionic or amphiphilic porphyrins irradiated with an average light dose of 4.3 J/cm(2) for 90 min resulted in >3 log(10) (>99.9%) to >4 log(10) (>99.99%) inactivation of both HAV and MS2. Viral inactivation may have been greater than observed because the limits of detection of the assay had been reached. Under ambient lighting conditions, none of the porphyrins was mutagenic in the Ames assay and only the congener with the longest chain-length, tetrakis (N-[n-hexadecyl]-4-pyridiniumyl) porphyrin, was appreciably toxic to mammalian cells. Disinfection by photoactivated synthetic porphyrins therefore can offer an effective and relatively safe approach to removal of nonenveloped viruses from aqueous media.     

Synthesis and properties of conjugated oligoyne-centered π-extended tetrathiafulvalene analogues and related macromolecular systems

Alkynyl-substituted phenyldithiafulvenes have been found to act as versatile building blocks for the construction of π-conjugated molecular rods, shape-persistent macrocycles (SPMs), and conducting polymers. Through Cu(I)-catalyzed alkynyl homocoupling, a series of linear-shaped π-extended tetrathiafulvalene analogues (exTTFs) carrying conjugated oligoynes (ranging from diyne to hexayne) as the central π-bridge were readily prepared. The solid-state properties and reactivities of diyne- and tetrayne-centered exTTFs were characterized by X-ray crystallography and differential scanning calorimetry (DSC), while the electronic properties of the oligoyne-exTTFs were elucidated by UV-vis absorption spectroscopy and density functional theory (DFT) calculations. Cyclic voltammetric analysis showed that the terminal phenyldithiafulvene groups of the oligyne-exTTFs could undergo oxidative coupling to form tetrathiafulvalene vinylogue (TTFV)-linked polymer wires. Through a different synthetic route involving oxidative dimerization and Pd/Cu-catalyzed alkynyl homocoupling, the acetylenic phenyldithiafulvene precursors led to shape-persistent macrocycles where the formation of trimeric macrocycles was particularly favored due to the small ring strain incurred. Finally, spectroelectrochemical studies on these oligoyne and TTF hybrid materials disclosed electrochromic and molecular redox-controlled switching properties applicable to molecular electronic and optoelectronic devices.     

Formation of unusual molecular rectangles and squares containing low spin and high spin Co(II) and Fe(II) centers

The ditopic carbohydrazide and thiocarbohydrazide based ligands H?L1 and H?L2 react with Co(II)(OAc)? to produce the homoleptic Co(II) molecular rectangles 1 and 2, containing either a mixture of high spin and low spin Co(II) sites or exclusively low spin Co(II) centers, respectively, with two mono-deprotonated ligands in a syn-conformation, and the other two doubly-deprotonated ligands in an anti-arrangement. The Co(II) centers are bridged by μ-O/S and μ-N-N groups, respectively. Magnetic susceptibility measurements indicate weak antiferromagnetic coupling between metal centers in 1 and 2, with room temperature magnetic moments of 6.6 and 3.4 μ(B), respectively, in good agreement with two S = 3/2 and two S = 1/2 centers for 1 and four S = 1/2 centers for 2. Reaction of H?L1 and H?L2 with Fe(II)(CF?SO?)? in the presence of a base leads to the formation of μ-O/S bridged homoleptic molecular squares 3 and 4, with the Fe(II) centers in high spin and low spin configurations, respectively at room temperature, as indicated from X-ray structural data and magnetic susceptibility measurements. However, in 3 one Fe(II) site undergoes spin crossover to a low spin state at about 150 K, while 4 stays diamagnetic in the full 2-300 K temperature range. Electrochemistry of 4 showed four distinct reversible red-ox waves associated with step-by-step one electron processes in the molecular square [-0.643 (ΔE(p) = 81 mV), -0.278 (ΔE(p) = 70 mV), +0.565 (ΔE(p) = 65 mV), ~1.1 V], associated with the Fe(II)/Fe(III) red-ox couples.     

Stochastic entangled chain dynamics of dense polymer solutions

We propose an adjustable-parameter-free, entangled chain dynamics model of dense polymer solutions. The model includes the self-consistent dynamics of molecular chains and solvent by describing the former via coarse-grained polymer dynamics that incorporate hydrodynamic interaction effects, and the latter via the forced Stokes equation. Real chain elasticity is modeled via the inclusion of a Pincus regime in the polymer's force-extension curve. Excluded volume effects are taken into account via the combined action of coarse-grained intermolecular potentials and explicit geometric tracking of chain entanglements. We demonstrate that entanglements are responsible for a new (compared to phantom chain dynamics), slow relaxation mode whose characteristic time scale agrees very well with experiment. Similarly good agreement between theory and experiment is also obtained for the equilibrium chain size. We develop methods for the solution of the model in periodic flow domains and apply them to the computation of entangled polymer solutions in equilibrium. We show that the number of entanglements Π agrees well with the number of entanglements expected on the basis of tube theory, satisfactorily reproducing the latter's scaling of Π with the polymer volume fraction φ. Our model predicts diminishing chain size with concentration, thus vindicating Flory's suggestion of excluded volume effects screening in dense solutions. The predicted scaling of chain size with φ is consistent with the heuristic, Flory theory based value.     

Observation of slowed rotation about the (η6-arene)-chromium bond in the chromium tricarbonyl complex of thesyn-anti-syn trimer of bicyclo[2.2.1]hept-2-yne

Summary The crystal and molecular structures are reported for the chromium tricarbonyl complexes of the sterically-demanding and rigidsyn-anti-syn andall-syn trimers of bicyclo[2.2.1]hept-2-yne, (3-Cr) and (4-Cr). At very low temperatures, a decoalescence phenomenon occurs in the 75.49 MHz¹³C-{¹H}-NMR spectrum of (3-Cr) and is unambiguously assigned to slowed rotation about the (⁶-arene)-chromium bond.Dedicated to Professor Dr. Karl Schlögl on the occasion of his 65th birthday     

The highly regiospecific synthesis and crystal structure determination of 1,1′-2,5′ substituted ring-locked ferrocenes

1,1′-Ferrocene biscarboxaldehyde (1) has been prepared and the aldehyde groups were subsequently protected with acetal groups to produce 1,1′-bisacetalferrocene (2). A ring-locked ferrocene was synthesised by further derivatisation of the cyclopentadiene rings at the 2,2′ positions with phosphine substituents to produce 2,2′-bis-(acetal)-1,1′-diphenylphosphinoferrocene (3), which was subsequently coordinated to either a nickel chloride (5) or nickel bromide (6) metal centre. The ring-locked ferrocene complexes produced 2,5′-bis-(acetal)-1,1′-diphenylphosphinoferrocene substitution patterns. The acetal protecting groups of 2,2′-bis-(acetal)-1,1′-diphenylphosphinoferrocene were removed to produce 1,1′-bis-carboxaldehyde-2,2′-diphenylphosphinoferrocene (4). The Cp rings of 1,1′-bisacetalferrocene were also further derivatised at the 2,2′ positions with a silane to produce the ring-locked 1,1′-siloxane-2,5′-bisacetalferrocenophane (7). The acetal protecting groups were removed from this to produce 1,1′-siloxane-2,5′-ferrocenophanecarboxaldehyde (8). For both the phosphine and siloxane electrophiles, the substitution on the Cp rings gives chiral products (obtained as racemic mixtures). Due to the highly regioselective nature of the reaction and diastereoselectivity in the products only C₂-symmetric compounds were observed without the presence of meso diastereoisomers. Subsequent ring-locking forced the Cp rings to rotate, leading to 1,1′-ring-locked ferrocenes with 2,5′-arrangement of the acetal groups (i.e. on opposite faces of the ferrocene unit).