Influence of Copper(I) Halides on the Reactivity of Aliphatic Carbodiimides

The influence of copper(I) halides CuX (X = Cl, Br, I) on the electronic structure of N,N′-diisopropylcarbodiimide (DICDI) and N,N′-dicyclohexylcarbodiimide (DCC) was investigated by means of computational DFT (density functional theory) methods. The coordination of the considered carbodiimides occurs by one of the nitrogen atoms, with the formation of linear complexes having a general formula of [CuX(carbodiimide)]. Besides varying the carbon–nitrogen bond lengths, the thermodynamically favourable interaction with Cu(I) reduces the electron density on the carbodiimides and alters the energies of the (NCN)-centred, unoccupied orbitals. A small dependence of these effects on the choice of the halide was observable. The computed Fukui functions suggested negligible interaction of Cu(I) with incoming nucleophiles, and the reactivity of carbodiimides was altered by coordination mainly because of the increased electrophilicity of the {NCN} fragments.

Linear structure taxonomy with the account of environmental polystructures impact

One of the specific features of transportation facilities design is the necessity to account changing environmental conditions in considerable distances along the track. The purpose of the study is theoretical substantiation of structural decomposition of linear structures based on the degree of uniformity of environmental factors effect on the geotechnical system of an object. A new approach to linear road zoning is suggested on the basis of comprehensive assessment of multidimensional spatial data on the environment. Theory of pattern recognition is used as a classification tool. Linear structure taxonomy, as a part of this theory, is based on hierarchical agglomerative clustering algorithms which provide consequential merge of operating territorial units into uniform linear complexes. Application of taxonomy methods is considered for automated tasks solving on various levels of roads information modeling: when designing structures, organizing construction and operating a facility.

Modulation of the relaxation dynamics of linear-shaped tetranuclear rare-earth clusters through utilizing different solvents

Nine tetranuclear centrosymmetric linear complexes have been synthesized and the two differently solvated DyIII complexes exhibit different magnetic relaxation behaviors.

A novel 4-UPU translational parallel mechanism with fault-tolerant configurations

This paper aims at designing a pure translational parallel mechanism constructed by UPU (universal-prismatic-universal joint) kinematic limbs. First, the typical problem of unexpected rotations is pointed out from analyzing the typical 3-UPU parallel mechanism, and the reason for unexpected rotations of parallel mechanism constructed by UPU kinematic limbs is analyzed. Then, in order to design a pure translational parallel mechanism constructed by UPU without the unexpected rotations, the 2-UPU single loop is chosen as the basic structure to construct the 4-UPU translational parallel mechanism. Each 2-UPU single loop can be used to constrain a rotation about an axis of the linear complexes, which defined the unexpected rotations. Therefore, a novel type of 4-UPU pure translational parallel mechanism with redundant actuations is proposed. Since the existence of redundantly actuated kinematic limb, this proposed parallel mechanism possesses analytical forward kinematics, and its singularity can be avoided completely. Finally, the workspace and fault-tolerant performance are analyzed. When the proposed 4-UPU parallel mechanism is located in a fault-tolerant configuration, the moving platform can still possess movable ability to realize the given task even if one kinematic limb is in locked-joint failure mode, and the fault-tolerant workspace is obtained.

A Line Geometric Foundation for Finite Screw Systems Associated With Spatial Linkages

This paper investigates the line varieties corresponding to finite screw systems associated with spatial linkages. This research is based on the correspondence between a screw and a linear complex, and a screw system corresponds to the intersection of the linear complexes. In finite kinematics, two screw systems associated with the finite motions of the revolute-revolute (R-R) and prismatic-revolute (P-R) open chains have been discovered. These two screw systems also led to the discovery of the screw systems associated with the finite motions of the spatial 4R, spatial RPRP, and other overconstrained linkages. By using the intersection operation of linear complexes, this paper finds the linear reguli corresponding to the finite motions of R-R and P-R chains. Then we utilize the sum operation of the linear reguli corresponding to the R-R and P-R chains to obtain the hyperbolic linear congruences corresponding to the finite motions of the spatial 4R and RPRP linkages. The result presented here serves as a line geometric foundation for finite screw systems associated with spatial linkages. In addition, with CAD drawings, this paper enables the visualization of the obtained line varieties and their operations.

Ab initio calculations on C6H6···(HF)n clusters — X–H···π hydrogen bond

MP2/6–311++G(d,p) calculations on C6H6···(HF)n clusters were performed and full optimizations were carried out for systems containing up to four HF molecules (n = 4) and calculations on the systems of C6v symmetry were carried out for up to six HF molecules (n = 6). Cooperativity effects were analyzed for these molecular aggregates. It was found that F–H···π and F–H···F hydrogen bonds exist for these complexes and those interactions are enhanced as the number of HF molecules increases. The cooperativity effects cause numerous changes in geometrical, energetic, and topological parameters, the latter ones derived from the quantum theory of atoms in molecules. Various correlations between the analyzed parameters are presented. There are meaningful differences between the molecular graphs for the fully optimized complexes and those for the linear complexes of C6v symmetry (for the latter, the linear chain of HF molecules is attached to a benzene molecule acting as the Lewis base). For the linear complexes, unique bond paths connect the H-attractor of the HF molecule and the ring critical point of the benzene molecule.