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 density functional formalism, its applications and prospects

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

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.

The Halogen Bond

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.

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

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.

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

Synthese de l'anion CO 2 F 2 2− par reaction de Tl 2 O avec COF 2 (formation de Tl 2 + CO 2 F 2 2− ) qui elimine rapidement TlF en formant Tl + CO 2 F − . Un essai de preparation identique de BF 3 O 2− echoue

Matrix-isolation study of oxide-transfer reactions to halogen-containing Lewis acids: synthesis of the CO2F22- anion and attempted synthesis of the BF3O2- anion

To enhance the versatility of organic azides in organic synthesis, a better understanding of their photochemistry is required. Herein, the photoreactivity of azidoisoxazole 1 was characterized in cryogenic matrices with IR and UV-Vis absorption spectroscopy. The irradiation (λ = 254 nm) of azidoisoxazole 1 in an argon matrix at 13 K and in glassy 2-methyltetrahydrofuran (mTHF) at 77 K yielded nitrosoalkene 3. Density functional theory (DFT) and complete active space self-consistent field (CASSCF) calculations were used to aid the characterization of nitrosoalkene 3 and to support the proposed mechanism for its formation. It is likely that nitrosoalkene 3 is formed from the singlet excited state of azidoisoxazole 1 via a concerted mechanism or from cleavage of an intermediate singlet nitrene that does not undergo efficient intersystem crossing to its triplet configuration.

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Photolysis of 5-Azido-3-Phenylisoxazole at Cryogenic Temperature: Formation and Direct Detection of a Nitrosoalkene

Magnetic circular dichroism of matrix isolated noble gas monohalides

Infrared matrix isolation and theoretical study of the initial intermediates in the reaction of ozone with cycloheptene

The matrix-isolation technique has been combined with infrared spectroscopy to identify and characterize the products formed by irradiation of cage-paired CrCl2O2 and a series of chloroethenes, C2HxCly (x + y = 4) For each system, oxygen-atom transfer occurred upon irradiation, yielding the corresponding acetyl chloride derivative and the Cl2CrO species The products were formed in the same matrix cage and strongly interacted to form a distinct molecular complex after formation Three different modes of interaction were explored computationally:  η1 to the oxygen atom, η2 to the CO bond, and η1 to the chlorine atom In addition, a five-membered metallocycle and the chloroepoxide species were considered No evidence was obtained for the chloroacetaldehyde derivative, indicating the occurrence of oxygen-atom attack at the more substituted carbon of the chloroethene Evidence tentatively supporting the formation of the metallocycle was obtained as well Theoretical calculations indicated that the acetyl chl

Bruce S. Ault

Papers

Matrix-isolation study of oxide-transfer reactions to halogen-containing Lewis acids: synthesis of the CO2F22- anion and attempted synthesis of the BF3O2- anion

Photolysis of 5-Azido-3-Phenylisoxazole at Cryogenic Temperature: Formation and Direct Detection of a Nitrosoalkene

Magnetic circular dichroism of matrix isolated noble gas monohalides

Infrared matrix isolation and theoretical study of the initial intermediates in the reaction of ozone with cycloheptene

Matrix isolation and theoretical study of the photochemical reaction of CrCl2O2 with chloroethenes.