Synthetic routes to lithium, magnesium, and zinc aluminyl complexes are reported, allowing for the first structural characterization of an unsupported lithium–aluminium bond. Crystallographic quantum-chemical studies consistent with presence a highly polar Li−Al interaction, characterized by low bond order relatively little charge transfer from Al Li. Comparison magnesium systems reveals change...

We have carried out a theoretical investigation of the methylalkalimetal monomers CH3M and tetramers (CH3M)4 with M = Li, Na, K, and Rb and, for comparison, the methyl halides CH3X with X = F, Cl, Br, and I, using density functional theory (DFT) at BP86/TZ2P. Our purpose is to determine how the structure and thermochemistry (e.g., C-M bond lengths and strengths, oligomerization energies) of org...

CcmE is a heme chaperone that binds heme transiently in the periplasm of Escherichia coli and delivers it to newly synthesized and exported c-type cytochromes. The chemical nature of the covalent bond between heme and H130 is not known. We have purified soluble histidine-tagged CcmE and present its spectroscopic characteristics in the visible range. Alanine scanning mutagenesis of conserved ami...

A novel [3]rotaxane composed of two 25-membered crownophanes and one axle molecule having two anthryl end groups was successfully synthesized via covalent bond formation followed by aminolysis, and can incorporate caesium ion into the space between the two macrocycles as a 1 : 1 sandwich-type complex, whereas it makes a 1 : 2 complex with lithium ion.

The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoreti...

Modeling indicates the presence of a region of low electronic density (a "σ-hole") on group 14 elements, and this offers an explanation for the ability of these elements to act as electrophilic sites and to form attractive interactions with nucleophiles. While many papers have described theoretical investigations of interactions involving carbon and silicon, such investigations of the heavier g...

We report novel molecular compound formation from silane-hydrogen mixtures with intermolecular interactions unprecedented for hydrogen-rich solids. A complex H_{2} vibron spectrum with anticorrelated pressure-frequency dependencies and a striking H-D exchange below 10 GPa reveal strong and unusual attractive interactions between SiH_{4} and H_{2} and molecular bond destabilization at remarkably...

An improved density matrix functional [correction to Buijse and Baerends functional (BBC)] is proposed, in which a hierarchy of physically motivated repulsive corrections is employed to the strongly overbinding functional of Buijse and Baerends (BB). The first correction C1 restores the repulsive exchange-correlation (xc) interaction between electrons in weakly occupied natural orbitals (NOs) a...

To understand the structural basis of biology, it is necessary to understand the transformations of macromolecules during functional cycles. These changes can involve large-scale conformational transformations, changes in the state of ligation or association, changes in dynamics, or alterations in covalent bond structure. X-ray crystallography and NMR spectroscopy have been invaluable for the d...

The title trimethyl-tin(IV) carboxyl-ate, [Sn(CH(3))(3)(C(11)H(11)O(2))](n), is a carboxyl-ate-bridged polymer in which the Sn atom exists in a trans-C(3)SnO(2) trigonal bipyramidal coordination. One Sn-O bond is a covalent bond [2.114 (2) Å], whereas the other is a dative bond [2.607 (2) Å]. The polymeric chain propagates along the b axis of the monoclinic unit cell.