Use Of Noncovalent Interactions Research Articles

Using the crystal to engineer the molecule: cis-trans-isomer selection in anionic bis(orotate) complexes

Two chelating orotate2− ligands have been coordinated to the same metal ion, producing the first dianionic bis-orotate complex, [Ni(orotate)2(H2O)2]2−, whose geometric isomer can be selected by enabling or vitiating the formation of non-covalent interactions in the solid in which the product is isolated. This provides an important example of the influence and potential use of non-covalent interactions for isomer selection in the synthesis of coordination compounds, as well as the manner in which such stereochemical selection can be achieved by the appropriate use of counterions.

Exciting Supramolecular Architectures: Light‐Induced Processes and Synthetic Transformations in Noncovalent Assemblies

AbstractFor Abstract see ChemInform Abstract in Full Text.

Exciting Supramolecular Architectures: Light‐Induced Processes and Synthetic Transformations in Noncovalent Assemblies

AbstractThis review outlines recent advances in the area of supramolecular photochemistry, particularly with respect to the use of noncovalent interactions to direct and control excited‐state processes in the solid phase and in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Molecules within molecules: recognition through self-assembly.

Synthetic molecular receptors that completely surround their target molecules can be created through the use of noncovalent interactions. These molecular capsules selectively sequester guest molecules from the influence of bulk solvent and other molecules on the basis of size, shape, and chemical complementarity. This reversible isolation spawns unique behavior within the confines of the host; the catalysis of chemical reactions and the stabilization of reactive species are possible outcomes that have been recently demonstrated. Compartmentalization of reagents can also have a dramatic effect on reactions that take place outside of the capsule, producing nonlinear kinetics in relatively simple reaction systems.

The Use of Non-Covalent Interactions in the Assembly of Metal/Organic Supramolecular Arrays

The design and synthesis of molecules that can organize into specific supramolecular assemblies in the solid state is an area of considerable interest, since incorporation of specific structural components into a crystal lattice may lead to new materials with desirable chemical and physical properties. However, it is still difficult to reliably predict crystal structures especially those in non-centrosymmetric space groups. To develop compounds whose assembly is more controlled and predictable, we are investigating the formation of supramolecular assemblies from C 2 - and C 3 -symmetric molecular species. The C 2 -symmetric systems use a rigid template to control the orientation of appended groups. Using hydrogen bonds and weak metal-ligand interactions as the key forces to control molecular structure, a variety of helical forming compounds can be isolated. The assembly of these compounds was monitored in the crystalline phase and shown to yield a diverse group of lattice architectures. Molecular helices have produced i) microporous networks, ii) extended helices in the lattice and iii) chiral arrays that assemble enantioselectively during crystallization. The use of C 3 -symmetric compounds in supramolecular assembly is illustrated by a chiral tripodal system that forms non-centrosymmetric crystal lattices. A Ni(II)-F salt of this tripod has a lattice that is noteworthy for its six-fold symmetric open framework structure and the alignment of all the molecular Ni-F bonds along a crystallographic axis.

Supramolecular Materials

This issue of MRS Bulletin is devoted to the subject of supramolecular materials. The term supramolecular is widely used to describe the intentional use of noncovalent interactions to bring about a desired arrangement of molecules. As the articles in this issue illustrate, this type of molecular engineering can provide structural control on the nanoscale and beyond, broadly impacting the properties of the resulting materials. The goal is to create a collection of molecules in which the whole possesses characteristics that are different and unattainable from the individual components.

Use of noncovalent interactions to form novel liquid crystalline polymeric materials

AbstractA novel concept in polymeric liquid crystalline (LC) materials, via electrostatic grafting or complexation of functionalized mesogens and appropriate polymers, is described. It is applied to three specific systems characterized by side‐chain LC architecture, two of which involve hydrogen‐bonding interactions, the third ionic interactions. In these systems, complexation tends to create greater order in the mesophases present. In the hydrogen‐bonded systems, the transition temperature from the isotropic state tends to decrease compared to that of the functionalized mesogen; in the ionically‐bonded system, the reverse is true. At low concentrations, the mesogens act as plasticizers.

Destabilization is as important as binding

Enzymes make use of non-covalent interactions with their substrates to bring about a large fraction of their catalytic activity. These interactions must destabilize, or increase the Gibbs energy, of the substrate in the active site in order that the transition state can be reached easily. This destabilization may be brought about by utilization of the intrinsic binding energy between the active site and the bound substrate by desolvation of charged groups, geometric distortion, electrostatic interactions and, especially, loss of entropy in the enzyme-substrate complex. These mechanisms are described by interaction energies and require utilization of the intrinsic binding energy that is realized from non-covalent interactions between the enzyme and substrate. Receptors and coupled vectorial processes, such as muscle contraction and active transport, utilize binding energy similarly to avoid large peaks and valleys along the Gibbs energy profile of the reaction under physiological conditions.