Bruce S. Ault

Bio: Bruce S. Ault is an academic researcher from University of Cincinnati. The author has contributed to research in topics: Matrix isolation & Infrared spectroscopy. The author has an hindex of 30, co-authored 269 publications receiving 4190 citations. Previous affiliations of Bruce S. Ault include University of Virginia.

Proton and deuteron radiolysis of argon matrix samples of O2 and Cl2. Infrared spectra of charged species

Abstract: Argon matrix samples containing O2 and Cl2 have been bombarded with 2.0 keV protons and deuterons during condensation at 15°K. In the oxygen experiments, bands due to O3 and HO2 appeared. Of most interest is isolated O−3 at 804.3 cm−1. Deuteron radiolysis produced increased yields of the 644 cm−1 band which is confirmed as a DAr+n species. Proton and deuteron radiolysis of chlorine−containing samples produced HCl2x and DCl2x in high yields. Owing to the strong electron scavenging capability of chlorine, these species are probably anions.

Photolysis of alpha-azidoacetophenones: direct detection of triplet alkyl nitrenes in solution.

Abstract: We report the first detection of triplet alkyl nitrenes in fluid solution by laser flash photolysis of alpha-azido acetophenone derivatives, 1. Alphazides 1 contain an intramolecular triplet sensitizer, which ensures formation of the triplet alkyl nitrene by bypassing the singlet nitrene intermediate. At room temperature, azides 1 cleave to form benzoyl and methyl azide radicals in competition with triplet energy transfer to form triplet alkyl nitrene. The major photoproduct 3 arises from interception of the triplet alkyl nitrene with benzoyl radicals. The triplet alkyl nitrene intermediates are also trapped with molecular oxygen to yield the corresponding 2-nitrophenylethanone. Laser flash photolysis of 1 reveals that the triplet alkyl nitrenes have absorption around 300 nm. The triplet alkyl nitrenes were further characterized by obtaining their UV and IR spectra in argon matrices. (13)C and (15)N isotope labeling studies allowed us to characterize the C-N stretch of the nitrene intermediate at 1201 cm(-)(1).

Matrix isolation study of the early intermediates in the ozonolysis of cyclopentene and cyclopentadiene: observation of two Criegee intermediates.

Abstract: Matrix isolation studies, combined with infrared spectroscopy, of the twin jet codeposition of ozone into matrices containing either cyclopentadiene or cyclopentene have led to the first observation of several early intermediates in these ozonolysis reactions. Specifically, evidence is presented for the formation, identification, and characterization of the long sought-after Criegee intermediate for each system, as well as the primary and secondary ozonides. These were observed after initial twin jet deposition and grew ∼300% upon annealing to 35 K. Extensive isotopic labeling (2H, 18O and mixtures) experiments provided important supporting data. Detailed theoretical calculations at the B3LYP/6-311++G(d,2p) and B3LYP/6-311++G(3df, 3pd) levels were carried out as well to augment the experimental work. Merged jet (flow reactor) experiments followed by cryogenic trapping in solid argon led to the formation of “late” stable oxidation products of cyclopentadiene and cyclopentene. In contrast, no thermal reacti...

The density functional formalism, its applications and prospects

Abstract: A scheme that reduces the calculations of ground-state properties of systems of interacting particles exactly to the solution of single-particle Hartree-type equations has obvious advantages. It is not surprising, then, that the density functional formalism, which provides a way of doing this, has received much attention in the past two decades. The quality of the energy surfaces calculated using a simple local-density approximation for exchange and correlation exceeds by far the original expectations. In this work, the authors survey the formalism and some of its applications (in particular to atoms and small molecules) and discuss the reasons for the successes and failures of the local-density approximation and some of its modifications.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

Abstract: Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aube rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

Photoremovable Protecting Groups in Chemistry and Biology: Reaction Mechanisms and Efficacy

Abstract: The review covers the knowledge on photoremovable protecting groups and includes all relevant chromophores studied in the time period of 2000–2012; the most relevant earlier works are also discussed.