A new copper(II) coordination compound with 2,2′-bipyridine-N-oxide as a ligand: Crystal structure, synthesis and spectroscopy

A new copper(II) coordination compound with the ligand 2,2′-bipyridine-N-oxide (abbreviated as bpyNO), Cu(bpyNO)₂(CF₃SO₃)₂, is described. This compound is investigated in detail by spectroscopy, EPR and X-ray crystal structure analysis. The compound crystallizes in the monoclinic space group P2₁/n with a = 6.554(1) ?, b = 13.681(3) ?, c = 14.935(3) ?, β = 98.77(3)°, Z = 2. The copper has an axial elongated octahedral geometry with the basal plane formed by two trans-orientated bpyNO molecules with Cu_N distance of 2.008(2) ? and a Cu_O distance of 1.950(2) ?. The axial positions are occupied by oxygen atoms of two trans-oriented triflate anions with a Cu_O distance of 2.397(2) ?.     

Transformation of β-chalcogeno alkenylboranes into tetrasubstituted olefins

In view of generating trisubstituted vinylic chalcogen derivatives, β-chalcogeno alkenylboranes generated through the chalcogen electrophile induced rearrangements of 1-alkynyltrialkyl borates have been subjected to Suzuki-Miyaura coupling and to boron to copper transmetalation followed by alkylation. Some of the trisubstituted vinyl sulfides obtained by this latter strategy have been converted efficiently into the title olefins through the NiCl₂(dmpe) catalyzed coupling with various Grignard reagents.     

Kinetics of cementite mechanosynthesis

The influence of ball to powder ratio and discontinous milling during ball milling of Fe_0.75C_0.25 elemental powder mixture is presented. The formation of Fe₃C cementite, Hägg and ε carbides has been follwed by X-ray diffraction and Mössbauer Spectroscopy. Higher ball to powder ratios induce faster kinetics. Synthesized cementite has crystallite sizes 9 to 11 nm.     

Ion mixed Co-Nb amorphous films

Multilayers of cobalt and niobium have been deposited in ultra high vacuum, using two E-beams onto both corning glass and silicon wafers substrates kept at 20°C. These films were then ion mixed using Xe ions at 200, 300 and 400 keV. The dose was 3 × 10¹⁵ ions cm^-2 in all cases. FMR and usual magnetization measurements were made to characterize the samples. Films mixed at 300 and 400 keV are homogeneous. FMR line width of 60 Oe and the simple spectra obtained lead us to conclude that these films are much more homogeneous than co-evaporated amorphous films of the same composition.     

On Eckhoff's conjecture for Radon numbers; or how far the proof is still away

Eckhoff's conjecture for the Τ-Radon numbers r(Τ) of a convexity space. (X,C) says r(Τ) ≦ (r?1)(Τ?1)+1, with r = r(2). The main result of this note is that Eckhoff's conjecture is true in case ¦X¦ ≦ 2r and Τ = 3, i.e. each (2r?1)-set in a space with 2r?1 or 2r elements has a 3-Radon partition.     

Design and optimization of cyclized NK1 antagonists with controlled atropisomeric properties

We have previously described a series of antagonists that showed high potency and selectivity for the NK₁ receptor. However, these compounds also had the undesirable property of existing as a mixture of four interconverting rotational isomers. Through biological and structural analysis of the atropisomers, a binding model was developed and used to guide the design of compounds, which were rigidified by installation of a cyclizing linkage. These compounds existed as a mixture of two atropisomers. Further elaboration of the ring system reinforced the desired conformation and eliminated atropisomeric properties. We found that the region distal to the 8-membered ring system could be modified while retaining NK₁ potency, and optimization led to further improvements in the in vivo activity.     

Polyhedral study of the capacitated vehicle routing problem

The capacitated vehicle routing problem (CVRP) considered in this paper occurs when goods must be delivered from a central depot to clients with known demands, usingk vehicles of fixed capacity. Each client must be assigned to exactly one of the vehicles. The set of clients assigned to each vehicle must satisfy the capacity constraint. The goal is to minimize the total distance traveled. When the capacity of the vehicles is large enough, this problem reduces to the famous traveling salesman problem (TSP). A variant of the problem in which each client is visited by at least one vehicle, called the graphical vehicle routing problem (GVRP), is also considered in this paper and used as a relaxation of CVRP. Our approach for CVRP and GVRP is to extend the polyhedral results known for TSP. For example, the subtour elimination constraints can be generalized to facets of both CVRP and GVRP. Interesting classes of facets arise as a generalization of the comb inequalities, depending on whether the depot is in a handle, a tooth, both or neither. We report on the optimal solution of two problem instances by a cutting plane algorithm that only uses inequalities from the above classes.This work was supported in part by NSF grant DDM-8901495.