Copper(II) complexes with a flexible oxamato ligand

We report on a convenient synthesis of the ligand precursor, diethylethylene-1,2-bis(oxamate), (Et2H2oeo, 1), and show how a partial and preferential hydrolysis of the ester group can give rise to the dianionic ligand, (H2oeo)2−. Reaction of this ligand with Cu(II) affords the neutral dimeric species, [Cu2(H2oeo)2], which has a low aqueous solubility. We describe the crystal structure of the hydrate Cu2(H2oeo)2(H2O)4 (2) and report magnetic studies that show a weak exchange interaction in the solid. Under more basic conditions and in the presence of Cu(II) ions, we are able to avoid amide cleavage and yet deprotonate the amide group, resulting in the formation of the highly soluble [Cu(Hoeo)2]4− complex anion. The structure of (NBu4)4[Cu(Hoeo)2](H2O)4 (3) is described and compared with the recently reported anhydrous phase

Dipotassium [N,N '-(propane-1,3-diyl)dioxamato-kappa O-4,N,N ',O ']copper(II) trihydrate: redetermination at 100 K

Redetermination of the structure of the title compound, K-2[Cu(C7H6N2O6)]center dot 3H(2)O,at 100 K reveals conformational disorder in the almost planar copper-containing molecular dianions and clarifies the complex hydrogen-bonded network involving the water molecules. The asymmetric unit contains two independent formula units. In one of the [Cu(C7H6N2O6)](2-) dianions, the propyl chain is disordered over two orientiations, with site-occupancy factors of 0.852 (5) and 0.148 (5)

Visual attention in autism families: ‘unaffected’ sibs share atypical frontal activation

Background: In addition to their more clinically evident abnormalities of social cognition, people with autism spectrum conditions (ASC) manifest perturbations of attention and sensory perception which may offer insights into the underlying neural abnormalities. Similar autistic traits in ASC relatives without a diagnosis suggest a continuity between clinically affected and unaffected family members

Forbidden induced subgraphs and the price of connectivity for feedback vertex set.

Let fvs(G) and cfvs(G) denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. For a graph class G, the price of connectivity for feedback vertex set (poc-fvs) for G is defined as the maximum ratio cfvs(G)/fvs(G) over all connected graphs G in G. It is known that the poc-fvs for general graphs is unbounded. We study the poc-fvs for graph classes defined by a finite family H of forbidden induced subgraphs. We characterize exactly those finite families H for which the poc-fvs for H-free graphs is bounded by a constant. Prior to our work, such a result was only known for the case where |H|=1

Solitary waves in coupled nonlinear Schrodinger equations with spatially inhomogeneous nonlinearities

Using Lie group theory we construct explicit solitary wave solutions of coupled nonlinear Schrodinger systems with spatially inhomogeneous nonlinearities. We present the general theory, use it to construct different families of explicit solutions and study their linear and dynamical stability

Pattern Selection in the Complex Ginzburg-Landau Equation with Multi-Resonant Forcing

We study the excitation of spatial patterns by resonant, multi-frequency forcing in systems undergoing a Hopf bifurcation to spatially homogeneous oscillations. Using weakly nonlinear analysis we show that for small amplitudes only stripe or hexagon patterns are linearly stable, whereas square patterns and patterns involving more than three modes are unstable. In the case of hexagon patterns up- and down-hexagons can be simultaneously stable. The third-order, weakly nonlinear analysis predicts stable square patterns and super-hexagons for larger amplitudes. Direct simulations show, however, that in this regime the third-order weakly nonlinear analysis is insufficient, and these patterns are, in fact unstable