Structures and Properties of 4-phpy, pyz, and 4,4′-bpy Adducts of Lantern-Type Dirhodium Complexes with µ-Formamidinato and µ-Carboxylato Bridges

Dinuclear and polymer complexes of 4-phenylpyridine (4-phpy), pyazine (pyz), and 4,4′-bipyridine (4,4′-bpy) were prepared by using cis-[Rh2(4-Me-pf)2(O2CR)2] (4-Me-pf- =N,N’-bis(4-methylphenyl)formamidinate anion; R = CF3 and CMe3) as precursor dinuclear units. The dinuclear structures of cis-[Rh2II,II(4-Me-pf)2(O2CR)2(4-phpy)2] and cis-[Rh2II,III(4-Me-pf)2(O2CCMe3)2(4-phpy)2]BF4 and polymer structures of [Rh2II,II(4-Me-pf)2(O2CR)2(L)]n (L = pyz and 4,4′-bpy) were confirmed by X-ray crystal structure analyses. In these complexes, the lantern-type dinuclear core structures with cis-(2:2) arrangement of formamidinato (4-Me-pf-) and carboxylato ligands are preserved with Rh–Rh distances of 2.44–2.47 Å, regardless of the difference in the axial ligand and oxidation state Rh2II,II or Rh2II,III. In the cyclic voltammograms (CVs) in CH2Cl2, the redox potentials for Rh2II,III/Rh2II,II were estimated as E1/2 = 0.07 V and −0.28 V (vs. Fc+/Fc) for cis-[Rh2(4-Me-pf)2(O2CCF3)2(4-phpy)2] and cis-[Rh2(4-Me-pf)2(O2CCMe3)2(4-phpy)2], respectively, negatively shifted by 0.16 and 0.12 V compared with those of corresponding parent dinuclear complexes. The results were interpreted that the axial interaction with 4-phpy ligands makes the Rh2II,II core oxidized easily. The oxidized complex cis-[Rh2(4-Me-pf)2(O2CCMe3)2(4-phpy)2]BF4 is paramagnetic, which was confirmed by effective magnetic moment value μeff = 1.90 μB at 300 K per Rh2II,III unit (S = 1/2). The polymer complexes [Rh2(4-Me-pf)2(O2CR)2(L)]n (L = pyz and 4,4′-bpy) showed Type II gas-adsorption properties for N2.

Hydrogen bonding to metals as a probe for an inverted ligand field

The M⋯HO axial interaction in the isoleptic and isoelectronic square-planar compounds [(CF3)3Pt(hq)]− and (CF3)3Au(hq) turns from attractive (M = Pt) to repulsive (M = Au), evidencing ligand-field inversion when going from Pt to Au.

Testing of 17 Identical Ductile Reinforced Concrete Beams with Various Loading Protocols and Boundary Conditions

A set of tests on 17 large-scale, nominally identical, beam specimens with variations in loading protocol, loading rate, and restraint to axial elongation are described. Three specimens were also repaired by epoxy injection following an initial damaging earthquake loading. This paper provides a detailed description of the test program, and the corresponding data are made available at Design-Safe (DOI: 10.17603/DS2SQ2K). While the primary goal of the test program was to improve the state of knowledge regarding the post-earthquake residual capacity of reinforced concrete plastic hinges in beams, the data are useful for modeling approaches that consider loading rate, plastic hinge elongation, cyclic degradation, and flexure–shear–axial interaction, in addition to investigating the effectiveness of post-earthquake repair techniques by epoxy injection of cracks.

Axial interaction of a vortex ring with a cylinder

In this paper, axial interaction of a vortex ring with a thin circular cylinder has been studied. An apparatus to generate clean vortex rings, free of piston and stopping vortex effects, has been used. Flow visualization and particle image velocimetry (PIV) experiments are carried out to determine and compare the characteristics of free and interacting vortex rings in the Reynolds number (defined with the circulation of the free travelling vortex ring) range of $2270<Re_{\unicode[STIX]{x1D6E4}}<6790$. It is observed that due to the presence of the cylinder, there is an increase in the velocity of the vortex ring. Also, noticeable changes in the characteristic properties of vortex ring such as core circulation, core diameter and ring diameter have been observed. Changes in these parameters are explained by two changes in the flow field between the vortex ring and the cylinder due to axial interactions: (i) displacement of the streamlines and (ii) acceleration in the induced velocity field in this region. These two mutually opposing effects determine the changes in the primary vortex ring properties that take place during interaction. To justify these experimental observations quantitatively, an analytical study of the interaction under an inviscid assumption is performed. The inviscid analysis does predict the increase in velocity during the interaction, but fails to predict the values observed in the present experiments. However, when the theory is used to correct the velocity change through incorporation of the effects of an axisymmetric induced boundary layer region over the cylinder, modelled as an annular vortex sheet of varying strength, the changes in the translational velocities of the vortex rings match closely with the experimental values.