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

Salt-molecule matrix reactions. Infrared spectra of the M+HCl-2 and M+Cl-3 ion pairs in solid argon

The reactions between ferrocene (Cp2Fe) (2a) and ozone (O3) were studied using low-temperature matrix-isolation techniques coupled with theoretical density functional theory (DFT) calculations. Co-deposition of Ar/Cp2Fe and Ar/O3 gas mixtures onto a cryogenically cooled CsI window produced a dark-green charge-transfer complex, Cp2Fe–O3, that photodecomposed upon red (λ ≥ 600 nm) and infrared (λ ≥ 1000 nm) irradiation but was stable to green or blue irradiation. Products of photodecomposition were characterized by FT-IR, oxygen-18 labeling, and DFT calculations using the B3LYP functionals and the 6-311G++(d,2p) basis set. Likely, photochemical products included four structures having the molecular formula C10H10FeO, identified by DFT calculations based on their calculated infrared spectra and 18O isotope shifts. Each of these calculated molecules had one intact and fully coordinated η5-C5H5 cyclopentadienyl (Cp) ring and (1) an η5-C5H5O cyclic ether (pyran ring) (2b), (2) an η4-C5H5O linear aldehyde (2c), ...

Infrared matrix-isolation and theoretical studies of the reactions of ferrocene with ozone.

Matrix isolation infrared spectroscopy has been combined with MP2/6-31+G(d,p) calculations to characterize the 1:1 hydrogen-bonded complexes between H2O2 and the bases NH3 and N(CH3)3. Most obvious from the spectra of these complexes and their deuterated analogues is the shift to lower frequency of the hydrogen-bonded O−H or O−D stretching bands relative to the isolated monomers. The experimental shifts are in good agreement with the computed shifts. Perturbation of the O−O−H bending mode was also observed, along with shifts of certain vibrational modes of the base subunits in the complexes. Surprisingly, the experimental intensities of the product bands are low when compared to other hydrogen-bonded systems and to the computed intensities.

Matrix Isolation and ab Initio Study of 1:1 Hydrogen-Bonded Complexes of H2O2 with NH3 and N(CH3)3

The initial and subsequent reaction products arising from the merged jet copyrolysis of (CH 3 ) 3 Al with NH 3 followed by trapping into argon matrices have been investigated. When the deposition line was at room temperature, the 1:1 complex (CH 3 ) 3 Al.NH 3 was isolated in high yield. Assignment to this species was verified by deuterium and 15 N isotropic labeling. The infrared spectrum of this adduct was characterized by very intense, sharp absorptions.

Bruce S. Ault

Papers

Salt-molecule matrix reactions. Infrared spectra of the M+HCl-2 and M+Cl-3 ion pairs in solid argon

Infrared matrix-isolation and theoretical studies of the reactions of ferrocene with ozone.

Matrix Isolation and ab Initio Study of 1:1 Hydrogen-Bonded Complexes of H2O2 with NH3 and N(CH3)3

Matrix isolation study of the reactions of trimethylaluminum with ammonia

The infrared spectra and theoretical calculations of frequencies of fac-tricarbonyl octahedral complexes of manganese(I).