Conformation‐Controlled Diplatinum(II)–Ferrocene Dyads to Achieve Long‐Lived Charge‐Separated States

Square‐planar polypyridyl platinum(II) complexes possess a rich range of structural and spectroscopic properties that are ideal for designing artificial photosynthetic centers. Taking advantage of the directionality in the charge‐transfer excitation from the metal to the polypyridyl ligand, we describe here diplatinum(II)–ferrocene dyads, open‐butterfly‐like dyad 1 and closed‐butterfly‐like dyad 2 , which were designed to understand the conformation and orientation effects to prolong the lifetime of charge‐separated state. In contrast to the open‐butterfly‐like dyad 1 , the closed‐butterfly‐like dyad 2 shows three‐times long lifetime of charge separated state upon photoexcitation, demonstrating that the orientation in the rigid structure of dyad 2 is a very important issue to achieve long‐lived charge separated state.     

Copper benzenedicarboxylate coordination polymers incorporating a long-spanning neutral co-ligand: Effect of anion inclusion and carboxylate pendant-arm length on topology and magnetism

Three divalent copper coordination polymers containing aromatic dicarboxylate ligands and the long-spanning tethering imine bis(4-pyridylmethyl)piperazine (bpmp) have been prepared and structurally characterized. The length of the dicarboxylate pendant arms, carboxylate binding mode, and the inclusion of anionic components play a synergistic role in structure direction in this system. {[Cu(ip)(bpmp)(H₂O)]·5H₂O}_n (ip = isophthalate, 1) displays neutral (4,4) rectangular coordination polymer grids that stack in an ABCD repeat pattern. Use of the longer pendant arm dicarboxylate 1,3-phenylenediacetate (phda) resulted in {[Cu₂(phda)₂(bpmp)]·H₂O}_n (2), a 3-D network coordination polymer with primitive cubic topology that features strongly antiferromagnetically coupled (J = −331(1) cm⁻¹) {Cu₂(CO₂)₄} paddlewheel units. In the presence of excess nitrate ions, {[Cu(phda)(Hbpmp)](NO₃)·3H₂O}_n (3) was isolated instead of 2; 3 manifests cationic 2-D coordination polymer layers built from weakly antiferromagnetically coupled (J = −2.43(1) cm⁻¹) {Cu₂O₂} dimers linked through phda and protonated bpmp ligands. The striking difference in magnetic properties is ascribed to the equatorial–equatorial versus axial–equatorial bridging of copper coordination spheres in 2 and 3, respectively.     

"One-pot" tandem C-H borylation/1,4-conjugate addition/reduction sequence

A microwave-assisted, one-pot, iridium-catalyzed aromatic C-H borylation/rhodium-catalyzed 1,4-conjugate addition sequence provides a highly robust protocol suitable for high-throughput array synthesis. Selective formation of either β-aryl-substituted ketones or the corresponding alcohols can be achieved in good overall yields by simple variation of the reaction conditions.     

Analysis of radiation induced degradation in FPC-461 fluoropolymers by variable temperature multinuclear NMR

Solid state nuclear magnetic resonance techniques have been used to investigate aging mechanisms in a vinyl chloride:chlorotrifluoroethylene copolymer, FPC-461, due to exposure to γ-radiation. Solid state ¹H MAS NMR spectra revealed structural changes in the polymer upon irradiation under both air and nitrogen atmospheres. Considerable degradation is seen with ¹H NMR in the vinyl chloride region of the polymer, particularly in the samples irradiated in air. ¹⁹F MAS NMR was used to investigate speciation in the chlorotrifluoroethylene blocks, though negligible changes were seen. ¹H and ¹⁹F NMR at elevated temperature revealed increased segmental mobility and decreased structural heterogeneity within the polymer, yielding significant resolution enhancement over room temperature solid state detection. The effects of multi-site exchange are manifested in both the ¹H and ¹⁹F NMR spectra as a line broadening and change in peak position as a function of temperature.     

Characterization of transverse channel concentration profiles obtainable with a class of microfluidic networks

We analyze mathematically a previously reported class of passive microfluidic mixing networks. The networks produce nonhomogeneous concentrations in the output channel, resulting in diverse concentration profiles. We formally prove that all profiles obtainable with this class of networks can be described as polynomials of degree no higher than the number of input channels less one. We derive explicit formulas for the calculation of resultant output concentration profiles and conversely for the calculation of input concentrations needed to obtain set output profiles.     

Discovery of bioactive small-molecule inhibitor of poly adp-ribose polymerase: implications for energy-deficient cells

Poly (ADP-ribose) polymerase (PARP1) is a nuclear protein that, when overactivated by oxidative stress-induced DNA damage, ADP ribosylates target proteins leading to dramatic cellular ATP depletion. We have discovered a biologically active small-molecule inhibitor of PARP1. The discovered compound inhibited PARP1 enzymatic activity in vitro and prevented ATP loss and cell death in a surrogate model of oxidative stress in vivo. We also investigated a new use for PARP1 inhibitors in energy-deficient cells by using Huntington's disease as a model. Our results showed that insult with the oxidant hydrogen peroxide depleted cellular ATP in mutant cells below the threshold of viability. The protective role of PARP1 inhibitors against oxidative stress has been shown in this model system.     

Soliton Solutions for a Generalized Quasilinear Elliptic Problem

Potential Analysis - We establish existence and multiplicity of solutions for the elliptic quasilinear Schrödinger equation $$ -\text{div}(g^{2}(u)\nabla u) +g(u)g^{\prime}(u)|\nabla u|^{2}+...     

Density functional theory for charge transfer: the nature of the N-bands of porphyrins and chlorophylls revealed through CAM-B3LYP, CASPT2, and SAC-CI calculations

While density functional theory (DFT) has been proven to be extremely useful for the prediction of thermodynamic and spectroscopic properties of molecules, to date most functionals used in common implementations of DFT display a systematic failure to predict the properties of charge-transfer processes. While this is explicitly manifest in Rydberg transitions of atoms and molecules and in molecular charge-transfer spectroscopy, it also becomes critical for systems containing extended conjugation such as polyenes and other conducting polymers, porphyrins, chlorophylls, etc. A new density functional, a Coulomb-attenuated hybrid exchange-correlation functional (CAM-B3LYP), has recently been developed specifically to overcome these limitations, and it has been shown to properly predict molecular charge-transfer spectra. Here, we demonstrate that it predicts qualitatively reasonable spectra for porphyrin, some oligoporphyrins, and chlorophyll. However, alternate density functionals developed to overcome the same limitations such as current-density functional theory are shown, in their present implementation, to remain inadequate. The CAM-B3LYP results are shown to be in excellent agreement with complete-active-space plus second-order M?ller-Plesset perturbation theory and symmetry-adapted cluster configuration interaction calculations: These depict the N and higher bands of porphyrins and chlorophylls as being charge-transfer bands associated with localization of molecular orbitals on individual pyrrole rings. The validity of the basic Gouterman model for the spectra of porphyrins and chlorophylls is confirmed, rejecting modern suggestions that non-Gouterman transitions lie close in energy to the Q-bands of chlorophylls. As porphyrins and chlorophylls provide useful paradigms for problems involving extended conjugation, the results obtained suggest that many significant areas of nanotechnology and biotechnology may now be realistically treated by cost-effective density-functional-based computational methods.     

On Eulerian orientations of even-degree hypercubes

It is well known that every Eulerian orientation of an Eulerian $2k$-edge connected (undirected) graph is strongly $k$-edge connected. A long-standing goal in the area is to obtain analogous results for other types of connectivity, such as node connectivity. We show that every Eulerian orientation of the hypercube of degree $2k$ is strongly $k$-node connected.