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

Matrix isolation infrared spectroscopic investigation of the coordination chemistry and reactivity of OVF3

Infrared matrix isolation studies of hydrogen bonds involving C-H bonds: CF3H, (CF2H)2O and CF3OCF2H with selected bases

The high-temperature pyrolytic reaction of (CH 3 ) 3 Al with H 2 S followed by trapping into argon matrices at 14 K has led to the formation and isolation of molecular Al 2 S 3 . Identification was made based on band positions, lack of deuterium shift, the observation of CH 3 D when D 2 S was employed, and a poor spectral match to known aluminum sulfides and by analogy to the molecular species B 2 O 3 and Al 2 O 3 . The spectra are suggestive of a V-shaped molecule, also similar to B 2 O 3 and in contrast to the linear structure of Al 2 O 3

Matrix isolation study of the reaction of trimethylaluminum with hydrogen sulfide and mercaptans: synthesis and spectra of molecular aluminum sulfide

Infrared matrix isolation of the 1:1 complexes of HCl and ClF with sulfur and nitrogen-containing macrocycles

The gas-phase reaction of CsF with GeF, diluted in argon, followed by rapid condensation at 15 K into an inert matrix, has led to the formation of the GeF5anion ion paired with Cs'. At higher concentrations, the GeF6'anion was observed as well. The GeF5anion was characterized by Ge-F stretching modes at 679, 696, and 730 cm-', indicative of a trigonal-bipyramidal structure perturbed by the cesium counterion. The reactions of CsCl with GeF, and CsF with GeCI., gave rise to the Cs'GeClF; and Cs'GeCI,F ion pairs, respectively, but with decreasing yields. The synthesis of the GeCI,anion by the reaction of CsCl with GeC1, was not successful, indicating either marginal stability of this anion or an inherent limitation to the salt/molecule technique.

Bruce S. Ault

Papers

Matrix isolation infrared spectroscopic investigation of the coordination chemistry and reactivity of OVF3

Infrared matrix isolation studies of hydrogen bonds involving C-H bonds: CF3H, (CF2H)2O and CF3OCF2H with selected bases

Matrix isolation study of the reaction of trimethylaluminum with hydrogen sulfide and mercaptans: synthesis and spectra of molecular aluminum sulfide

Infrared matrix isolation of the 1:1 complexes of HCl and ClF with sulfur and nitrogen-containing macrocycles

Infrared matrix isolation studies of the pentahalogermanate anions