Synthesis,dynamic light scattering,and luminescence properties of copolymers containing iridium(III) bisterpyridine in the side chain

Supramolecular block‐random copolymers containing [Ir(terpy)₂]³⁺ in the side chain were synthesized via postfunctionalization of a P(S‐b‐AC_terpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐AC_terpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007     

Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

Supramolecular fluorophores for biological studies: phenylene vinylene-amino acid amphiphiles

We report here on a family of self-assembling fluorescent organic amphiphiles with a biomolecular L-lysine hydrophile and a photonically active phenylene vinylene hydrophobe. Unlike conventional amphiphiles, these segmented dendrimers feature a rigid, branched hydrophobe, and have packing characteristics controlled by the ratio of cross-sectional areas of the hydrophobe and hydrophile. In dilute solution, the amphiphiles form supramolecular aggregates, which are easily taken in by cells through an endocytic pathway, and have no discernible effect on cell proliferation or morphology. An analogous pyrene-based amphiphile was cytotoxic, suggesting that cell survival may be linked either to the self-assembling nature of the amphiphiles, or to the specific properties of the phenylene vinylene segment. The combination of photonic and biological components in these amphiphiles provides great potential for applications in sensing or delivery of molecules to intracellular targets.     

Dialing in color with rare earth metals: facile photoluminescent production of true white light

Combining polymeric architectures with metal ions produces hybrid materials with extremely rich properties. We are studying polymers containing terpyridine in the side chain. In this report, the chelation of lanthanide ions, Eu³⁺, Tb³⁺, and Dy³⁺ resulted in metal functionalized copolymers that exhibited excellent emission of red, green, and blue light respectively. The polymer architecture easily allows incorporation of all three colors into the material, which leads to the facile production of true white light in solution or the solid state. Quantum efficiencies for the polymer systems were determined. The white light system had an efficiency of 5%. Various combinations of colors were achieved from the basic RBG colors by simply varying the metal ion ratios in the polymer backbone. This easy tuning of the color makes these systems attractive. Copyright © 2007 John Wiley & Sons, Ltd.     

The Dynamics of the Reaction of FeO+ and H2: A Model for Inorganic Oxidation

Extensive density functional theory (DFT) calculations using the B3LYP functional were used to explore the sextet and quartet energy potential energy surfaces (PESs) of the title reaction, and as a basis to fit global analytical reactive PESs. Surface-hopping dynamics on these PESs reproduce the experimentally observed reactivity and confirm that hydrogen activation rather than spin-state change is rate-limiting at low reaction energy, where the main products are Fe⁺ and H₂O. A change in spin state is inefficient in the product region so that excited-state ⁴Fe⁺ is the dominant product. At higher energies, spin-allowed hydrogen atom abstraction to form FeOH⁺ predominates. At intermediate energy, a previously unexpected rebound mechanism contributes significantly to the reactivity.     

Supramolecular Materials with Electroactive Chemical Functions

A diblock coil with diphenylaminophenyl side chains, oligoethylene oxide segments, and a rigid molecular pentamer of phenylene vinylene are present in the molecule studied here (see formula). When films of this material were investigated, the material was found to organize into nanostructures 12 nm in dimension.     

Explicitly correlated coupled-cluster theory using cusp conditions. I. Perturbation analysis of coupled-cluster singles and doubles (CCSD-F12)

Geminal functions based on Slater-type correlation factors and fixed expansion coefficients, determined by cusp conditions, have in recent years been forwarded as an efficient and numerically stable method for introducing explicit electron correlation into coupled-cluster theory. In this work, we analyze the equations of explicitly correlated coupled-cluster singles and doubles (CCSD-F12) theory and introduce an ordering scheme based on perturbation theory which can be used to characterize and understand the various approximations found in the literature. Numerical results for a test set of 29 molecules support our analysis and give additional insight. In particular, our results help rationalize the success of the CCSD(F12) approximation which is based on a very systematic cancellation of the neglected, otherwise individually large third-order geminal-geminal coupling terms. Further approximations to CCSD(F12) can be introduced without sacrificing the accuracy if the entire set of third-order coupling terms between the conventional doubles cluster amplitudes and the geminal doubles amplitudes is retained, leading to the recently proposed CCSD[F12] and CCSD(F12(?)) models, which have negligible overhead compared to conventional CCSD calculations. Particularly, the importance of the ring-term type contribution is pointed out which may be used to improve on other existing approximations such as CCSD-F12b. For small basis sets, it might be advantageous to keep certain higher-order terms leading to CCSD-F12(?), which, for the case of the SP ansatz, merely involves a noniterative correction to CCSD(F12(?)).