Photochemistry of homoconjugated ketones: 2-(carbomethoxy)spiro[5.5]undeca-1, 3-dien-7-one.

The direct and sensitized irradiation of the title compound ($\text{2}$c) was studied with particular attention to its oxa-di-π-methane rearrangement, the product of which is of notable structural and synthetic interest. X-ray diffraction data of the final product (8) are given to support structural assignments.     

Control of surface functionality in poly(phenylenevinylene) dendritic architectures

The efficient synthesis of new asymmetric poly(phenylenevinylene) dendritic macromolecules using a stepwise convergent-growth approach is described. By an iterative methodology that made use of the Horner-Wadsworth-Emmons (HWE) reaction, dendrons and dendrimers up to the third generation, with eight different functional groups located at the periphery, were prepared in good yields. Both the number and placement of functionalities can be accurately controlled to afford a large variety of dendritic architectures.     

Molecular dynamics simulation of the reaction of hydration of formaldehyde using a potential based on solute-solvent interaction energy components

Molecular dynamics simulations of aqueous solutions at infinite dilution of the reaction of water with formaldehyde, H(2)O + H(2)CO --> H(2)C(OH)(2), were performed using Lennard-Jones 12-6-1 potentials to describe the solute-solvent interactions, and TIP3P to describe the water-water interactions. The Morokuma decomposition scheme of ab initio interaction energies at the SCF level and the dispersion component at MP2 level were used to reproduce the molecular parameters of the solute-water interaction potential. The results show that the functions that use the EX-PL-DIS-ES interaction model to describe the solvation of the reactant and product systems lead to good values of the reaction (DeltaG) and activation (DeltaG(#)) free energy as compared with those from using AMBER-derived parameters, and with the available theoretical and experimental data.     

Molecular simulation of the hydration of ethene to ethanol using ab initio potentials and free energy curves

Molecular dynamics simulations of aqueous solutions at infinite dilution of the reaction of water with ethene: H2O + CH2CH2 --> CH3CH2OH were performed using Lennard-Jones 12-6-1 potentials to describe the solute-solvent interactions, and TIP3P to describe the water-water interactions. The Morokuma decomposition scheme of ab initio interaction energies at the SCF level and the dispersion component at the MP2 level were used to reproduce the molecular parameters of the solute-water interaction potentials. The results show that the functions that use the EX-PL-DIS-ES interaction model to describe the solvation of the reactant, transition state, and product systems lead to good values of the reaction (Delta G) and acceptable values of the activation (Delta G#) free energy as compared with those from using AMBER-derived parameters, using the available theoretical and experimental data as referents.     

Sub‐Picosecond Singlet Exciton Fission in Cyano‐Substituted Diaryltetracenes

Thin films of 5,11‐dicyano‐6,12‐diphenyltetracene ( TcCN ) have been studied for their ability to undergo singlet exciton fission (SF). Functionalization of tetracene with cyano substituents yields a more stable chromophore with favorable energetics for exoergic SF (2E(T₁)?E(S₁)=?0.17 eV), where S₁ and T₁ are singlet and triplet excitons, respectively. As a result of tuning the triplet‐state energy, SF is faster in TcCN relative to the corresponding endoergic process in tetracene. SF proceeds with two time constants in the film samples (τ=0.8±0.2 ps and τ=23±3 ps), which is attributed to structural disorder within the film giving rise to one population with a favorable interchromophore geometry, which undergoes rapid SF, and a second population in which the initially formed singlet exciton must diffuse to a site at which this favorable geometry exists. A triplet yield analysis using transient absorption spectra indicates the formation of 1.6±0.3 triplets per initial excited state.     

Constructing Highly Incident Configurations

A geometric (q,k)-configuration is a collection of points and straight lines in the Euclidean plane in which each point lies on q lines and each line passes through k points. We say a (q,k)-configuration is highly incident when one (or both) of q or k is strictly greater than 4. In this paper, two simple lemmas are used to construct infinite classes of (2q,2k)-configurations for any q,k≥2; the resulting configurations have non-trivial dihedral symmetry. In particular, this construction produces the only known infinite class of symmetric 6-configurations.     

Polycationic glycosides

Cationic lipids have long been known to serve as antibacterial and antifungal agents. Prior efforts with attachment of cationic lipids to carbohydrate-based surfaces have suggested the possibility that carbohydrate-attached cationic lipids might serve as antibacterial and antifungal pharmaceutical agents. Toward the understanding of this possibility, we have synthesized several series of cationic lipids attached to a variety of glycosides with the intent of generating antimicrobial agents that would meet the requirement for serving as a pharmaceutical agent, specifically that the agent be effective at a very low concentration as well as being biodegradable within the organism being treated. The initial results of our approach to this goal are presented.